Colloquiam: Documents published in 2022

Compression after impact test on woven CFRP laminates with graphene

Materiales Compuestos — Tue, 12 Jul 2022 20:28:04 +0200

Nowadays carbon fibre reinforced epoxy laminates represent the standard material in the designing and manufacturing of aeronautical composite structures. However, advantages related to metals manufacturing could represent an important menace for the role of composite materials in this industry. Therefore, new improvements in composite structures have to be seek in order to improve their competitiveness.

Graphene is a nanomaterial that possess the higher stiffness and strength ever measured. Therefore, the use of Graphene Related Material (GRM) for enhancing composite laminate materials could represent an important advance in order to reduce their impact vulnerability and to improve the performance of Resin Transfer Molding (RTM) composites.

In this work epoxy resin doped with GRM were used to manufacture carbon fiber aeronautical composites by RTM. Low velocity impacts and Compression After Impact (CAI) tests were performed. Regarding experimental methodology, ASTM standard was followed, also new measuring techniques were used as 3D High Speed Digital Image Correlations. All tests were performed on GRM enhanced material and reference material to compare their results. Under impact loads, elastic behavior, peak force or damage results do not depend on the addition of graphenic particles. Whereas, a minor improvement enhanced with GRM in compression preserving the visible damage for an impact equivalent to the tool drop (30 J). Is important to keep this effect in order to detect damages in the composites structures.

The role of nanofiber veils developed by electrospinning in mechanical properties of carbon fiber composites

Materiales Compuestos — Tue, 12 Jul 2022 20:15:03 +0200

Research on nanofiber veils used as reinforcements in composite materials began several years ago and there have been numerous works published on this topic by the research community. However, there is still a long way to go to build a solid knowledge on the behavior of nanofibers in the most common failure mode in carbon fiber composites; the delamination that happens between the tissues of the fibers and the fragile matrices that agglutinate them. The fact of inserting these thermoplastic veils in the delamination region without hardly altering the weight of the composite has proven to be an adequate method to increase the fracture toughness since the beginning of these investigations.

Electrospinning is a versatile and simple technique that allows a tailor-made manufacture of nanofiber veils from a wide variety of polymers, with different morphologies in terms of grammage, nanofiber diameter, etc. One of the most important characteristics of nanofibers is their nanometric scale, which gives them a great surface-volume ratio, high porosity and excellent mechanical performance. This paper shows the influence of the grammage of veils based on polyamide 6 nanofibers and the different ways to achieve the same weight in mechanical properties of the manufactured composites. The results show an improvement in the fracture toughness and in the impact strength when these thermoplastic veils are introduced.

X-ray tomography investigation of the use of veils to improve the impact tolerance of thin-ply composite laminates

Materiales Compuestos — Tue, 12 Jul 2022 20:05:04 +0200

Interleaving high fibre areal weight veils, typically used to improve the interlaminar fracture toughness and impact tolerance of composite laminates, impairs their tensile and compressive properties. We characterized the mechanical response of a thin-ply quasi-isotropic baseline laminate and laminates interleaved with two types of light (4 g/m2) co-polyamide veil: tension, compression, mode-I interlaminar fracture toughness, impact and compression after impact. X-ray tomography provided comprehensive understanding into the effect interleaving has on the microstructure, impact resistance and fracture process zone of double cantilever beam specimens.

The veil fibre diameter was the key-parameter controlling the tensile properties (the veil with thinner fibres avoided resin accumulation at the interfaces and left the baseline tensile properties unaffected). The adhesion between veil fibres and resin controlled mode-I interlaminar fracture toughness (the veil with a suspected higher adhesion deflected crack propagation to the surrounding 0° plies, which enhanced mode-I interlaminar fracture toughness by 43%). Both veils reduced pristine compressive strength by up to 9%; however, the veil with thinner fibres improved CAI strength by up to 28% for impact at 14 J.

Magnetic properties and applications of glass-coated ferromagnetic microwires

Materiales Compuestos — Sun, 10 Jul 2022 13:44:03 +0200

The impact of post-processing on soft magnetic properties and the giant magnetoimpedance (GMI) effect of Fe- and Co-based glass-coated microwires is evaluated. A remarkable improvement of magnetic softness and GMI effect is observed in Fe-rich glass-coated microwires subjected to stress annealing. Frequency dependence of GMI ratio of stress-annealed Fe-rich microwires has been discussed considering frequency dependence of the skin penetration depth, δ, as well as magnetic anisotropy distribution within the metallic nucleus. Annealed and stress-annealed Co-rich microwires present rectangular hysteresis loop and single and fast domain wall propagation. However, Co-based stress-annealed microwires present high magnetoimpedance ratio. Observed stress-induced anisotropy and related changes of magnetic properties are discussed considering internal stresses relaxation and “back-stresses”.

Iber v3. Manual de referencia e interfaz de usuario de las nuevas implementaciones

Marcos Sanz-Ramos — Sun, 10 Jul 2022 09:06:07 +0200

Iber es un modelo numérico bidimensional de simulación de flujo turbulento en lámina libre en régimen no-permanente, y de procesos medioambientales en hidráulica fluvial. Desde el lanzamiento de la primera versión, que incluía un motor de cálculo hidrodinámico completamente acoplado con procesos de transporte de sedimento y turbulencia, Iber ha ido evolucionando hasta convertirse en una herramienta de modelización de flujo en lámina libre de procesos ambientales de elevada complejidad. En este documento se presentan los desarrollos realizados para la versión 3, donde los avances son principalmente en cuatro líneas de investigación: un nuevo módulo de drenaje urbano, un avance significativo en las capacidades del módulo de hidrología, un nuevo módulo de erosión de suelos, y un nuevo módulo para el cálculo del transporte de sedimentos considerando material no uniforme (mezclas). Asimismo, todos los trabajos han ido acompañados por una tarea transversal de mejora de la interfaz, tanto para los módulos ya existentes, como la creación de nuevas ventanas y menús para los nuevos módulos con el objetivo de mejorar todo el flujo de trabajo.

Análisis citogenético mediante cultivo de linfocitos T para el cariotipo de la oveja domestica (Ovis aries)

ANA CAMILA BELTRAN URREGO — Sun, 10 Jul 2022 02:36:05 +0200

Se realizaron cuatro cultivos de linfocitos de una Hembra Ovina encontrada en las instalaciones de la Universidad Nacional de Colombia sede Bogotá, siguiendo respectivamente el protocolo de siembra y cosecha previamente establecido en el laboratorio de citogenética de la Institución. Se utilizó 1ml de sangre completa heparinizada en cada cultivo, a partir de los cuales se obtuvieron 12 láminas goteadas, asignadas de manera equitativa a los procesos de tinción Giemsa, Bandeo G (GTG) y Bandeo C (CBG). Las láminas fueron observadas en un microscopio de luz con el fin de establecer el cariotipo de la hembra ovina seleccionada, la cual cumplió con el número cromosómico normal de la especie, siendo este 2n=54. En adición a esto, no se encontraron anomalías estructurales aparentes en el cariotipo obtenido.

Formulación y determinación de aportes nutricionales de una dieta balanceada para loras cariamarillas (Amazona amazónica) en estado de rehabilitación

ANA CAMILA BELTRAN URREGO — Sun, 10 Jul 2022 01:59:03 +0200

Las patologías desarrolladas a partir de desórdenes nutricionales son una problemática de común ocurrencia en los centros de rehabilitación de fauna silvestre, ya que por su naturaleza, este tipo de animales no suele ser objeto de estudio, y por tanto, el desconocimiento en materia de hábitos alimenticios y requerimientos nutricionales es evidente. Con base a esta problemática, se decidió trabajar con un grupo psitácidas pertenecientes al género Amazona en estado de rehabilitación para la formulación de una dieta balaceada acorde con sus requerimientos y con los recursos disponibles en la Unidad de rehabilitación. Las aves fueron sometidas a una evaluación física y nutricional la cual fue contrastada con los aportes nutricionales y consumos de la dieta que se ofrecía al momento de iniciar el estudio, para finalmente realizar ajustes a la formula existente y sugerir estrategias en el modo de alimentación de estos psitácidos. Se encontró que a pesar de presentar pesos aceptables y uniformes (346 - 440g) y una condición corporal óptima en el 92% de las aves, se contaba con problemas de déficit en proteína, fosforo y aminoácidos esenciales, además de considerables excesos de energía y cantidad de alimento ofrecido por ave, generando desperdicios de entre 34 y 51% del total de la dieta. A partir de estos hallazgos fue posible realizar un ajuste de la dieta ofrecida, alterando las proporciones de ingredientes según su categoría (frutas, verduras, semillas y granos, concentrado, suplementos y otros), con lo cual se logró suplir con los déficits nutricionales y reducir los excesos en cantidad de alimento y energía ofrecida. Sin embargo, se reconoce el déficit de información en el área y la necesidad urgente de realizar investigaciones encaminadas a la nutrición de psitácidos que permita optimizar y mejorar los procesos de rehabilitación y las condiciones de los lugares encargados de llevar a cabo estas labores.

Smart composites with magnetic microwire inclusions allowing non-contact stress and temperature monitoring

Materiales Compuestos — Sat, 09 Jul 2022 15:01:03 +0200

We observed evolution of the transmission and reflection parameters of the composites contaning magnetic microwire inclusions during the composites matrix polymerization. A remarkable change of the reflection and transmission in the range of 4-7 GHz upon the matrix polymerization is observed. Observed dependencies are discussed considering variation of temperature and stresses during the thermoset matrix polymerization and their influence on magnetic properties of glass-coated microwires. Obtained results are considered as a base for novel sensing technique allowing non-destructive and non-contact monitoring of the composites utilizing ferromagnetic glass-coated microwire inclusions with magnetic properties sensitive to tensile stress and temperature.

Epoxy resins used in rollers for the paper manufacturing with improve mechanic properties, conductivity and roughness

Materiales Compuestos — Sat, 09 Jul 2022 14:45:28 +0200

Big rollers are used in the paper manufacturing industry, they are composed of layers of different materials (metallic core, polyurethane and composite with epoxy resin between others). The company TECNOCAUCHO is dedicated to the manufacturing of these rollers and towether with AIMPLAS have modified two epoxy resins that are used in two rollers (guide and calendering). In both cases the epoxy resin layer was the weak point of the rollers, consequently the mechanic properties of the resin were improved in order to extend the useful life of each roller and also the conductivity of the guide roller and the roughness and brightness of the calendering roller were improved. Currently, a epoxy resin with the improved properties achieved in this paper is not available on the market.

Guide roller: mechanic properties of the epoxy resin were improved 7,7% compared to original comercial resin through nanofiller addition. Besides, resistivity values below 100 Ωm (company´s target value) were achieved, minimizing the sparks generation.

Calendering roller: mechanic properties were improved to 18,6% (tensile strenght at 130ºC), brightness and roughness (Rz below to 0,2 microns, company´s target value) through nanofillers addition, improving significantly the superficial properties of the paper.

Composite epoxy matrixes Bisphenol A free

Materiales Compuestos — Sat, 09 Jul 2022 14:34:03 +0200

Although Bisphenol A content in epoxy resins based on it (called Bisphenol A diglycidyl ethers, BADGE) is practically undetectable using nowadays analytical techniques, Bisphenol A is a controversial product due to its toxicology. For this reason, epoxy resins in general and composite epoxy matrices in particular are in focus of scientific and social media. We studied several alternatives both petroleum-based (e.g. trimethylolpropane or entaerythritol) and bio-based (e.g. isosorbide, lignin or sorbitol). The main objective of these BADGE alternatives is to obtain products that could be adapted to the requirements of the composite market with minor differences respect to Bisphenol A epoxy derivatives in morphological, chemical, mechanical and thermal properties.

Temperature effects on the microstructure and on the mechanical response of 3D printed continuous carbon fibre reinforced polymers

Materiales Compuestos — Sat, 09 Jul 2022 13:53:04 +0200

The state-of-the-art additive manufacturing technology of continuous carbon fibre reinforced polymers (CFRP) is based on fused filament fabrication (FFF), which has a great potential for reproducing robust and complex geometries. However, 3D printed CFRP present relatively poor mechanical properties in comparison to traditional composites. This work analyses post-processing temperature effects on the microstructure and on the interlaminar mechanical properties of the printed CFRP. Post-processed pieces at 150°C (exceeding matrix glass transition) showed a reduction of porosity by 80% and improved mechanical properties by 250% with respect to unprocessed pieces.

Molds manufactured with 3D printing for UV curing using Light-RTM

Materiales Compuestos — Sat, 09 Jul 2022 13:39:03 +0200

Ultraviolet (UV) curing is a competitive process both in terms of cycle time and energy consumption. However, it is limited to open mold processes where the material can be irradiated directly with UV light. There is a variant of RTM, Light-RTM, in which the flexible semi-mold can be manufactured with transparent/translucent materials and in small thicknesses. In the present work the feasibility of performing the semi-mold by stereolithography (SLA) has been studied. The photocurable resin selected for SLA was the high temperature resin from FormLabs. First, the UV light transmission has been characterized according to the thickness of the semi-mold wall, in which the mold thickness has been determined in 3 mm. The ageing process has also been analysed, characterising the variation of the transmitted spectrum as a function of the irradiation time for a 3 mm thick plate, where a loss of light transmission of approximately 13 % has been observed for 15 minutes of exposure time. Finally, a semi-mold has been manufactured for the manufacture by Light-RTM of a 150 mm × 40 mm × 2 mm flat plate. During the process, there were no problems of vacuum loss and the intensity of UV light that passes through the semi-mold allows curing the photocurable matrix of the composite material.

Manufacturing of carbon fiber reinforced PET from wastes of CFRP and PET bottles

Materiales Compuestos — Fri, 08 Jul 2022 18:35:04 +0200

This work is focused on two current and important issues. On one hand, 12 millions of tons of PET are thrown into the sea each year. In fact, in spite of being a recyclable polymer, less than 50 % of processed PET is recycled in Europe. On the other hand, thermoset matrix composites are widely used in the industry and the end-of-life products and scraps need to be recycled. Compared to thermoplastics, thermosets present a problem for being recycled or remolded due to their irreversible curing.

Many researches are focused on the recycling of carbon fiber reinforced epoxy, presenting three different paths: mechanical, thermal and chemical recycling. Thermal recycling is the most promising because it allows to recover clean fiber. However, it is an energetically expensive and non-environmentally friendly process. Chemical recycling, for its part, needs hazardous products, such as nitric acid, to dissolve the matrix. Finally, both, fibers and matrix, are recovered with mechanical recycling which consists on milling the composite to obtain finer parts.

In this work, unidirectional carbon fiber reinforced epoxy is blade-milled and it is used as reinforcement of a new composite. As matrix, PET coming from recycled bottles is used. First of all, pellets of PET are produced from the bottles with a blade mill. Recycled composite and PET are mixed and a sheet is manufactured with a hot plates press. The resulting material is chemically and mechanically tested.

Propuesta y Formulación para el Análisis Subestructurado de Grandes Estructuras de Material Compuesto

Dominika Behrendt — Fri, 08 Jul 2022 16:32:03 +0200

The main objective of FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept in which advanced and innovative FRP manufacturing technologies are successfully introduced. This project has received funding from European Union's Horizon 2020 research and innovation programme under grant agreement n°101006860.

Ternary cements as a sustainable alternative in Civil Engineering

Materiales Compuestos — Fri, 08 Jul 2022 14:48:02 +0200

Construction industry is among the most polluting human activities, mainly due to CO2 emisions produced during portland cement manufacture. The cement production industry has incorporated byproducts of other industries, to produce a more sustainable material. This would be due to the decrease of raw materials, treat byproducts in a safe way, and improve the properties of the cement manufactured. The durability of the structures would also be improved. The main problem is that the properties are not good in the short term.

In the last years there have been many efforts regarding the incorporation of two or more aditions, because they produce a synergic effect that improve the properties of concrete or mortars. This type of cements has been called ternary cements

In this work ternary cements have been produced using three different aditions: ground granulated blast furnance slag, and fly ashes, as active aditions, and limestone filler as a non-active adition. The total amount of addition is limited to a 35% maximum, for all of them together, as it is stated in the instruction for structural concrete, EHE-08. 35% is the maximum adition allowed for concrete production, and always added to ordinary portland cement.

Mechanical properties and some durability parameters have been studied in the short terms for both a ternary cement and the results have been compared with a binary cement.The results are promising, and show a good behavior, what means that these cements could be safely used in real structures.

Structural analysis and design of a large inflatable hangar for aircrafts (preprint)

Eugenio Oñate — Thu, 07 Jul 2022 10:42:03 +0200

Buildair S.A. has recently designed, manufactured and built an inflatable hangar (termed H75 hangar) for the aeronautic industry in Jeddah Airport (Kingdom of Saudi Arabia). H75 hangar is the largest aircell inflated structure ever built in the world, finally erected in July 2019. The structural analysis and design of the main body of the hangar has involved complex structural concepts due to the specificity of the structural elements employed, like membranes and straps which lead to a highly non-linear mechanical problem, or the treatment of wind over the structure without a defined standard for inflatable structures. In this paper, the structural conception and specificities of the structure are presented, as well as the design procedure for the H75 hangar based in the numerical analysis, to fulfill the design requirements in terms of stresses, and deformations for the structural elements of the main body.

Design and characteristic analysis of dual-excitation and dual-modulation axial permanent magnetic gear

Daming Wang — Thu, 07 Jul 2022 07:23:50 +0200

Due to marked axial and tangential magnetic leakage and low torque density of APMG, an external magnetic regulating ring is developed in this study based on APMG to form a DEM-APMG structure of bidirectional excitation and bidirectional modulation. The low-speed permanent magnet rotor of the DEM-APMG is sandwiched between the inner and outer flux regulating rings, which can convert the axial and tangential flux leakage of the APMG into useful harmonics to increase the output torque and torque density of the DEM-APMG. In this study, mathematical analysis is used to describe the air gap magnetic density and electromagnetic torque model of a DEM-APMG, which essentially describes the root cause of the increase in torque density. Using 3-D finite element static and dynamic simulations, the transmission characteristics of the APMG and DEM-APMG are compared and analyzed. Results show that the maximum static torque of the DEM-APMG high-speed and low-speed permanent magnet rotor with the same outer diameter increase by 22.7% and 23.8%, respectively, compared with APMG, 26% and 29%, respectively, in steady-state operation, and the torque density increases by 24%. The influence of the primary structural parameters on the transmission characteristics is also investigated using the control variable method. Results show that the duty cycle of the magnet adjusting block, the axial length of the high-speed permanent magnet and the low-speed permanent magnet have the strongest effect on the torque density of the DEM-APMG. When the axial length of the high-speed permanent magnet and low-speed permanent magnet is 8mm, and the duty cycle is 0.4, the torque density can reach the optimal value of 156kNm/m³.

WRF-LES Simulation of Wind Flow over Rough Urban Surface during Typhoon Lan (2017)

Scipedia content — Wed, 06 Jul 2022 17:36:54 +0200

In this study, we investigated the influence of ground surface boundary conditions of the meteorological model on the accuracy in predicting the mean wind speed and wind speed fluctuation in the urban area. Two types of ground surface boundary conditions (Cases 1 and 2) were created. In Case 1, the roughness length for the urban area was set to 0.5 m uniformly, whereas in Case 2, the spatial distribution of roughness length for the urban area was set based on the urban geometry. We performed the wind flow simulation in the central part of Tokyo during Typhoon Lan (2017) by using WRF-LES with the created ground surface boundary conditions. By setting the roughness length based on the urban geometry, the accuracy in predicting the mean wind speed was improved significantly. However, in both cases, WRF-LES underestimated the turbulence intensity, especially near the ground surface.

Wind Pressure Characteristics of High-rise buildings in Middle and High-height Urban Areas Spread over Local Terrain

Scipedia content — Wed, 06 Jul 2022 17:36:35 +0200

In an urban area where middle and high-height buildings are densely built on a complex terrain, it is important for wind-resistant design to know what kind of strong wind blows during a typhoon and the wind pressure acts on the building. In this study, we focused on the wind of the wind direction SSE observed during typhoon LAN (2017), and investigated the relationship between the topography and the flow field around the buildings, and the wall surface pressure by LES. As a result, we clarified the complicated flow due to the interference between the target building and the local terrain and surrounding buildings. In addition, the validity was shown by comparing the wind pressure coefficient of LES with that of the wind tunnel experiment.

Visualization of Flow Simulation Based on AR Using GNSS Data

Scipedia content — Wed, 06 Jul 2022 17:36:20 +0200

This paper presents an AR visualization system for flow simulation based on the location-based AR using GNSS data. The accuracy of position data obtained by the GNSS receiving machine is investigated and the position correction method using two GNSS receiving machines is investigated. The present method is applied to the visualization of flow velocity in rivers. The validity and the efficiency of the present method is investigated by the comparison with the marker based AR.

Validation of DEM using macroscopic stress-strain behavior and microscopic particle motion in sheared granular assemblies

Scipedia content — Wed, 06 Jul 2022 17:36:05 +0200

Validation and/or calibration of distinct element method (DEM) models is usually performed by comparing element test simulation results with the corresponding stress-strain relationships observed in the laboratory [1]. However, such a validation procedure performed at the macroscopic level does not ensure capturing the microscopic particle-level motion [2]. Thus, the reliability of the DEM model may be limited to some stress paths and may not hold when the material response becomes non-uniform for example when shear bands develop. In this study, the validity of the DEM is assessed by comparing the numerical result with experimental data considering both particle-scale behavior (including particle rotations) and macroscopic stress-strain characteristics observed in shearing tests on granular media. Biaxial shearing tests were conducted on bi-disperse granular assemblies composed of around 2700 circular particles under different confining pressures. Particle-level motions were detected by a novel image analysis technique. Particle rotations are observed to be a key mechanism for the deformation of granular materials. The results from this study suggest that to properly calibrate DEM models able to capture the mechanical behavior in a more realistic way particle scale motions observed in laboratory experiments along with macroscopic response are necessary.

Unconditionally stable dynamic analysis of multi-patch Kirchhoff-Love shells in large deformations

Scipedia content — Wed, 06 Jul 2022 17:35:49 +0200

This work presents a numerical framework for long dynamic simulations of structures made of multiple thin shells undergoing large deformations. The C1-continuity requirement of the KirchhoffLove theory is met in the interior of patches by cubic NURBS approximation functions with membrane locking avoided by patch-wise reduced integration. A simple penalty approach for coupling adjacent patches, applicable also to non-smooth interfaces and non-matching discretization is adopted to impose translational and rotational continuity. A time-stepping scheme is proposed to achieve energy conservation and unconditional stability for general nonlinear strain measures and penalty coupling terms, like the nonlinear rotational one for thin shells. The method is a modified mid-point rule with the internal forces evaluated using the average value of the stress at the step end-points and an integral mean of the strain-displacement tangent operator over the step computed by time integration points.

Unbonded Fiber Reinforced Elastomeric Isolator (UFREI) made of high damping natural rubber blend

Scipedia content — Wed, 06 Jul 2022 17:35:35 +0200

Some commercial base isolators have been introduced in the last four decades to protect buildings from vibration and earthquakes. Typically, they are constituted by several alternating layers of rubber pads and steel (elastomeric isolator) interposed by two continuous pads, limiting vertical deformability. At the same time, they exhibit good deformation capacity in the horizontal direction when subjected to a seismic load. A very effective seismic isolator shall satisfy the following functions: good performance under all service loads, vertical and horizontal; provide enough horizontal flexibility to reach the target natural period for the isolated structure; recentering capability after the ground motion so that no residual horizontal displacement can downgrade the serviceability of the structure; provide an adequate level of energy dissipation (damping) to control the displacement that could damage other structural members. Steel-reinforced elastomeric isolators (SREIs) are the most used method of seismic isolation. Since these devices are generally too expensive due to the need to introduce thick steel plates for their supports and the high energy consumed for the manufacturing process, they are not suitable for ordinary residential buildings, especially in developing countries. Compared with SREIs, fiber-reinforced elastomeric isolators (FREIs) have considerably lower weight and can be installed between the structure in elevation and the foundation without any bonding or fastening in the so called unbonded application (UFREI), reducing costs hugely. Furthermore, without steel supports, the shear load is transferred through the friction generated between the isolator and the structure surfaces, improving the dissipation energy of the devices. The main feature of such a UFREIs is the large deformability thanks to the rollover deformation and the favorably lower lateral stiffness compared to the bonded isolator. In this paper, a series of experimental tests of the rubber compound and numerical analyses of UFREIs made of high damping rubbers (HDR) combined with glass fiber reinforcement have been performed. A HDR made of Natural Rubber and Ethylene Propylene Diene Monomer (NREPDM) blend has been considered. Finite Element shear test results have shown good dynamic performances of the proposed device.

DOUBLE-SIDED ULTRASONIC TESTING AND IMAGING OF MULTILAYER COMPOSITES WITH OUT-OF-PLANE FIBER WRINKLING

Scipedia content — Wed, 06 Jul 2022 17:35:22 +0200

For fiber reinforced polymers (FRPs), ply stacking errors and fiber waviness during manufacturing will have a great influence on the mechanical properties of composites, which requires non-destructive testing and evaluation (NDT&E) for potential structure defects. Herein, this study analyzes the ultrasonic echo signals in pulse-echo (PE) mode to assess the layered structure and sub-structure of laminates, analytically and numerically. Based on recursive stiffness matrix method and analytic-signal technology, analytical modeling is performed to investigate the propagation of ultrasound and detect the layered structure in flat laminates. In addition, a numerical finite element model is built to further study the propagation of ultrasound in wavy composites. Based on the circular variances of ply angles extracted by structure tensor analysis, the double-sided ultrasonic testing and B-scan imaging method is proposed to correct the imaging artifact areas of wavy composites. After statistical validation, this weighted sum method can indeed reduce the influence of ultrasonic beam deviation caused by out-of-plane fiber wrinkling, thereby improving the imaging effect in wavy composites.

2D analytical solution for multi-segmented Auminium-steel- composite panel-An Aerospace Application

Scipedia content — Wed, 06 Jul 2022 17:35:08 +0200

E-vehicles and light weight structural parts in automotive and aerospace industry has led to design and development of new structures where traditional materials aluminium/steel are joined with composite laminated materials. This approach has led the engineers/researchers to reduce weight and ultimately save fuel consumption and reduce carbon footprints. Moreover, prosthetic limbs are also designed to have varying material along the length for better suitability. The above problems cannot be analysed using functionally graded theories/concepts. In theory, material properties vary linearly, exponentially, or power-law-like along x-values but for the above cases, material property does not follow a particular variation. Further even, it is not always practical to produce or manufacture components having very smooth variations along the length. Number of research articles are reported on the development of joining techniques for the dissimilar materials.1, 2Bending, free vibration and buckling analysis is also needed for theses case.3At the joining or interface point, local inplane and transverse stresses may rise sharply and may cause debonding and failure of structures. One dimensional analysis based on classical assumption or higher order can not accurately predict the stress behaviour at theses places. In this paper, an attempt is made to develop the 2D analytical solution for multi-segmented Al/ steel-composite panel under transverse loading. Extended Kantorovich method is used for developing governing equations. Continuity of displacement and stresses are satisfied at interface of each segment. Two segmented panels having aluminium/steel equal segment are considered. The deflection and stresses are compared with the finite element solution and found in good agreement.

Tsunami Evacuation Simulation Considering Building Collapse and Fire Spread

Scipedia content — Wed, 06 Jul 2022 17:34:42 +0200

The objective of this study is to develop a tsunami evacuation simulation system that takes into account building collapse and fire spread. Road blockage is determined by calculating the road blockage probability due to building collapse, taking into account the size of the assumed earthquake, location of buildings, and type of building. For fire spread simulation, an existing simulator based on the fire spread rate equation is used. Under average wind direction and speed conditions for the target area, arbitrary fire points are set up and fire spread is represented using fire times for each building obtained from the simulation. The applicability of this system as a scenario is extended. The present system is applied to several examples to demonstrate the validity and effectiveness of the system.

Transport of logarithmic potentials versus process duration

Scipedia content — Wed, 06 Jul 2022 17:34:16 +0200

The transport of logarithmic potentials provides a dynamical equilibrium that allows obtaining the lasting time estimation of a dynamical process. Bayesian rules are applied as a bridge between logarithmic potentials and the transport equation to obtain the potential associated with the interaction between systems. In this work, a data set from a chemical process is considered to test the method. Then, to enrich the analysis, an actual prediction by dynamical components is perform that illustrates how long every process and the global common process last.

Transient cooling of reactor vessel wall during LOCA

Scipedia content — Wed, 06 Jul 2022 17:33:59 +0200

The article describes a multistage modelling methodology proposed by the author for the modelling of emergency core cooling processes. The methodology is based on the best practice guidelines presented by the IAEA, it is applied to a specific scenario of emergency core cooling during a loss of coolant accident [1] with an effective break diameter of 20mm. A 3D thermohydraulic analysis was performed as the first step in the solution process, where the transient changes in the pressure, velocity and temperature fields within the reactor pressure vessel were studied [2]. The primary knowledge learned when processing the results of the first step, was the presence of an oscillating cold coolant stripe in close proximity to the pressure vessel wall. The next step in the methodology consisted of a three-dimensional thermomechanical analysis of the reactor pressure vessel [3]. In this step, pressure thermal shock induced critical zones of mechanical loading were identified and the influence of the oscillatory character of the cold stripe on the pressure vessel was studied. The last step of the methodology consisted of a fracture mechanics analysis of postulated defects during the pressure thermal shock. Acquired results from the final step shown, that the postulated defects' sensitivity to the oscillatory nature of the cold stripe is highly dependent on the postulated defect's orientation.

Towards automated computation with uncertainty estimation for industrial simulation of ship flow

Scipedia content — Wed, 06 Jul 2022 17:33:37 +0200

Adaptive grid refinement is tested for routine, automated simulations of ship resistance in calm water. A simulation protocol for these computations is fine-tuned on one test case and then applied unchanged to three different cases. The solutions are numerically accurate and compare well with experiments. Effective numerical uncertainty estimation increases the trustworthiness of the solutions.

Toward Concurrent Multiscale Topology Optimization for High Heat Conductive and Light Weight Structure

Scipedia content — Wed, 06 Jul 2022 17:33:21 +0200

Solid structures that are light and heat conductive are significant in a variety of engineering applications. We investigated multiscale topology optimization for excessive lightweight heat-conductive porous structures and introduced a mathematical optimization model formulation for concurrently optimizing the macrostructure and the constitutive pores (microstructure) to maximize the design performance. The microscale is constructed utilizing the asymptotic homogenization approach as a representative volume element. During the optimization process, the effective heat conductivity tensor of the microstructure is assessed and utilized as the heat conductivity of the macrostructure for each iteration. To address the macro and microstructure connection, a sensitivity analysis of this concurrent optimization approach was developed. Moreover, the method of introducing initial predetermined design domain was investigated to attain fin-like design in order to despite heat efficiently. Results showed very good results for attaining excessive weight reduction with attaining high heat conductivity. Moreover, the method of predetermined design domains increased the performance significantly.

Topology Optimization of Acoustic-Poroelastic-Elastic Structures for Sound Attenuation

Scipedia content — Wed, 06 Jul 2022 17:33:08 +0200

Structures for sound attenuation have been explored in many scenarios, ranging from civil construction to automotive and aerospace industries. However, the proper multiphysics interactions of acoustic-poroelastic-elastic structures are still challenging, especially when topology optimization techniques are involved. This work entails a new topology optimization methodology based on the Bidirectional Evolutionary Structural Optimization (BESO) approach to design bidimensional structures for sound attenuation enhancements. The full modeling of poroelastic bodies is done by the mixedu/p technique. At the same time, the elastic and acoustic (air) materials are obtained by the degeneration of the latter, leading to the well-known elasto-dynamic and Helmholtz formulations, respectively. Such procedure is done in by the combination of the Finite Element Method (FEM) with the Unified Multiphase (UMP) modeling approach, which in turn contributes to the development of material interpolation schemes suited for the application. In this scenario, the topology optimization problem is established as the maximization of the time-averaged dissipative power, composed by the summation of its structural, viscous and thermal dissipative components. The numerical examples show the effectiveness of the proposed methodology since it provides well-defined topologies with generally enhanced dissipative performances.

Time domain Sound Field Analysis Using the Finite Element Method and the Fast Multipole Boundary Element Method

Scipedia content — Wed, 06 Jul 2022 17:32:52 +0200

This paper presents a noise evaluation system based on acoustic wave theory. This paper utilizes two methods – the finite element method and the boundary element method using a fast multipole method, and compares the numerical results of the benchmark problem. In addition, we show the results using the analytical model of the complex shape based on standard specifications of noise barriers and discuss the difference of the numerical results and auralization results between the two methods.

Time-dependent modelling of quasi-brittle materials with a strong discontinuity approach

Scipedia content — Wed, 06 Jul 2022 17:32:36 +0200

The time-dependent behaviour of quasi-brittle materials can have a significant effect on serviceability and ultimate failure. E.g., in the case of concrete structures, the presence of cracking can evolve, propagate and gradually widen over time, therefore significantly changing the stress state and expected structural response. The development of models that can account for the discrete nature of cracking whilst predicting time-dependent behaviour can be of interest to many practical applications. The discrete strong discontinuity approach (DSDA) has been validated as a reliable approach for simulating the cracking phenomenon by directly embedding the traction-separation constitutive relation within finite elements, therefore enriching standard finite element models with the ability to capture cracks, where material can separate without the need for remeshing. This work presents a generalisation to account for the long-term behaviour of cracked quasi-brittle materials, more specifically creep and shrinkage. To this end, a rate-type creep is first applied through a number of kelvin units; the interaction of the resulting response from the Kelvin chain system, shrinkage, and discrete cracking is developed to obtain a suitable constitutive model for the discrete crack simulations. Finally, the formulation is deployed on a finite element code where the performance of the proposed model is assessed through representative numerical examples.

Three-Dimensional Super-Resolution of Passive-Scalar and Velocity Distributions Using Neural Networks for Real-Time Prediction of Urban Micrometeorology

Scipedia content — Wed, 06 Jul 2022 17:32:22 +0200

In future cities, micrometeorological predictions will be essential to various services such as drone operations. However, the real-time prediction is difficult even by using a super-computer. To reduce the computation cost, super-resolution (SR) techniques can be utilized, which infer high-resolution images from low-resolution ones. The present paper confirms the validity of three-dimensional (3D) SR for micrometeorology prediction in an urban city. A new neural network is proposed to simultaneously super-resolve 3D temperature and velocity fields. The network is trained using the micrometeorology simulations that incorporate the buildings and 3D radiative transfer. The error of the 3D SR is sufficiently small: 0.14 K for temperature and 0.38 m s-1for velocity. The computation time of the 3D SR is negligible, implying the feasibility of real-time predictions for the urban micrometeorology.

The non-smooth tale of Accumoli civic tower

Scipedia content — Wed, 06 Jul 2022 17:32:07 +0200

In this paper, advanced numerical models are used to study the progressive damage of a historic building, namely the Palazzo of Podestà and the Civic Tower of Accumoli (central Italy). The dynamic behaviour of the structure is analyzed following important seismic events such as those that occurred in 2016-2017. Discontinuous and continuous approaches are used. In the formers, the masonry response is represented both with Discrete Element Method (DEM) and the Non-Smooth Contact Dynamic (NSCD) method; in the latter the masonry non linearity is replicated using the Concrete Damage Plasticity (CDP) model. The numerical results showed a good correspondence of all the approaches with the real damage suffered by the structure after the seismic sequence.

The effect of particle shape on rockfall events

Scipedia content — Wed, 06 Jul 2022 17:31:52 +0200

The effects of rock shape and initial orientation on the rockfall phenomena are studied using a two-dimensional polygonal discrete element method (DEM). In the simulation, rock particles with the same mass but different shapes are dropped from the same height onto a straight slope to investigate the variations in both translational and rotational kinetic energies and the runout distance. Parametric studies under varied angularity and aspect ratio of the rock revealed a significant effect of rock shape and initial orientation on the runout distance.

Texture Shape Optimization for Minimization of Friction Coefficient (Comparison of Shape Optimization Results for Circular and Herringbone Texture)

Scipedia content — Wed, 06 Jul 2022 17:31:37 +0200

In order to reduce the friction coefficient of lubricated surfaces with circular and herringbone shaped textures, an adjust variable method was introduced to optimize the shape of the oil film thickness distribution in the textured areas. The optimized oil film thickness distribution can be evolved by the shape updating formula proposed by Sasaoka et al. based on the smoothed sensitivity. For computational convenience, the objective function in the optimization is defined as the friction force, not the friction coefficient. The constraint function was also defined by the Reynolds equation. The finite element method was used in the optimization procedure. The optimization results show that the herringbone shape texture has a bowl-shaped oil film thickness distribution similar to that of the circular shape texture. Furthermore, the location of the deepest part was found to be different.

Testing the use of radial basis function augmented with polynomials as basis functions in the boundary element method for heat transfer problems

Scipedia content — Wed, 06 Jul 2022 17:31:22 +0200

The accuracy of the numerical solution obtained by the Boundary Element Method (BEM) is directly affected by the type of interpolation function used. Meanwhile, interpolation by radial basis function augmented with polynomials has been shown to be more accurate than Lagrange interpolation for a range of different functions. Therefore, this paper is concerned with the application of such functions as the interpolation functions for all boundary values in the boundary element method for the numerical solution of two-dimensional heat transfer problems. Numerical examples with different geometries and temperature distributions are presented and comparisons with both isogeometric and classical formulation are made to demonstrate the accuracy of the proposed method.

Surrogate model of elastic large-deformation behaviors of compliant mechanism using co-rotational beam element

Scipedia content — Wed, 06 Jul 2022 17:31:08 +0200

We propose a surrogate model for predicting in-plane nonlinear structural deformations of a compliant mechanism. Our model utilizing a 2-dimensional co-rotational beam element extracts the essential deformation degrees-of-freedoms (DOFs) of bending flexible beams. The total number of DOFs of nodes at both ends of a 2-dimensional beam is six, while the number of deformation DOFs is three, i.e., axial extension, symmetric bending, and anti-symmetric bending. Therefore, it enables us to reduce the computational cost, from six to three, associated with the models by using the essential deformation DOFs of the co-rotational beam element. Moreover, it is difficult to predict the nonlinear responses of forces derived from displacements of a compliant mechanism due to bifurcation of the deformation-path. To overcome the problem, we generate the datasets by applying external forces and use the inverse response for constructing the surrogate models. In the numerical example, large-deformation behaviors of several types of compliant mechanisms are predicted by our surrogate models constructed by three typical learning algorithms: polynomial approximation, radial basis function, and neural network. The prediction performances and computational costs are investigated for verifying that they can be beneficial tools for designing a compliant mechanism with nonlinear elastic deformation behaviors.

Study on Reinforced Concrete Slabs Subjected to low-velocity Impact - The method of Preventing scattering debris by using steel deck plates -

Scipedia content — Wed, 06 Jul 2022 17:30:50 +0200

In the building construction above public lines such as railroads, it is necessary to assume the accident by falling objects such as column members lifted by cranes. Even if RC slabs prevent perforation caused by falling objects during construction, scattering concrete debris may cause serious damage to the public space below the slabs. This study suggests an anchoring system to control the debris scattering by folding up the end of steel deck plates which are used as permanent formworks. Impact test was performed with specimens that have an anchoring system or not with changing the drop height as parameters. As a result, the anchoring system prevents debris from scattering in the case that the falling height was twice as high as the case without the anchoring system. In addition, finite element analysis was also performed to evaluate the result of the impact test. The result showed the analysis could evaluate the debris scattering of both the specimen which has the anchoring system or not.

Spherulite Microstructure Formation Simulation Based on Effect of Molding Conditions on Polylactic Acid

Scipedia content — Wed, 06 Jul 2022 17:30:32 +0200

This study investigates a simulation model predicting spherulite microstructure formation based on experimental observations. The crystallization process of polylactic acid is observed at different molding temperatures by in-situ observation, and the rate of spherulite formation and growth is estimated. Furthermore, according to the Turnbull-Fisher primary nucleation model and the Lauritzen-Hoffman secondary nucleation model, Monte Carlo simulations of spherulite microstructure formation are performed based on the obtained experimental results. The validity of the method is verified by a comparison of the simulated and the experimental results.

Spatially Variable Coal Slope Stability Analysis using Image-Based Scaled Boundary Finite Element Method

Scipedia content — Wed, 06 Jul 2022 17:30:15 +0200

Slope stability analysis is a challenging task when complex stratigraphies, complex geometries and spatially variably soil parameters are considered. Numerical methods, such as the finite element method are commonly used in slope stability analyses, however, these methods require significant user input when meshing geometries consisting of heterogeneous and spatially variable materials. This paper presents a numerical technique combining the scaled boundary finite element method and image-based meshing for slope stability analysis. The inputs for the analyses require images detailing the stratigraphy and the spatial variation of the material properties. Quadtree decomposition is applied to simultaneously generate meshes and consider the spatial variation of material properties directly from the images through a mapping technique. The stability of slopes is analysed assuming an elastoplastic Mohr-Coulomb constitutive model for the soil. The shear strength reduction technique is applied to evaluate the shear reduction factor iteratively to define the factor of safety of the slope. Coal slopes at Yallourn open-pit mine, Victoria, Australia was considered, forming the basis of a case study to demonstrate the applicability of the presented method.

Simulation of wave propagation in remote bonded FBG sensors using the spectral element method

Scipedia content — Wed, 06 Jul 2022 17:29:59 +0200

Ultrasonic guided waves (GW) due to their ability to monitor large areas with few sensors, are commonly employed for structural health monitoring (SHM) in aerospace, civil, and mechanical industries. The FBG sensors in the edge filtering setup are re-emerging as a favored technique for GW sensing. The FBG sensors offer embeddability, ability to be multiplexed, small size, and immunity to electric and magnetic fields. To enhance the sensitivity of these sensors, these sensors are deployed in the so-called remote bonding configuration where the optical fiber is bonded to the structure while the FBG sensor is free. This configuration not only enhances the sensitivity but also opens up possibility of self-referencing. In this setup the GW in the structure is coupled to the fiber and converted into fiber modes. These modes propagate along the fiber and then are sensed at the FBG. The conversion of the plate modes to fiber modes is a phenomenon which is still being studied. The effect of the adhesive layer and the material properties of the adhesive on the coupling are still not known. Furthermore the directional nature of this coupling and its marked difference from the directly bonded configuration needs to be studied in detail. For this detailed study a computationally efficient model which captures the physics of the coupling is necessary. Hence, in this research we develop a numerical model based on the spectral element method (SEM) for the modeling of the remote bonded configuration of the FBG. The model comprises four meters long optical fiber bonded to the center of the plate by the adhesive layer and the piezoelectric disc (PZT) used for wave excitation. The ability of the SEM model to capture the effect of the adhesive and the remote bonding as well as the directional nature of the coupling has been studied in this paper. The model is validated with analytical and experimental results. It has been shown that the SEM model captures the physics of the coupling and is computationally more efficient than other methods using conventional finite element software.

Simulation of the temperature distribution in glued butt-joint timber connections

Scipedia content — Wed, 06 Jul 2022 17:29:45 +0200

The end-grain bonding of timber components with the Timber Structures 3.0 technology (TS3) is an emerging construction method in timber engineering. For onsite applications at low ambient temperatures down to 0 °C, it is being investigated numerically and experimentally if it’s possible to heat the butt-joint to above 17 °C during the curing process using a heating wire. The current research results show that this is basically possible.

Simulation of Stretching Deformation of Film for Electronic Devices in Automotive Applications

Scipedia content — Wed, 06 Jul 2022 17:29:30 +0200

In this study, we proposed a simulation method for film transverse stretching based on the finite element method using the orthogonal anisotropy plastic model. The simulation method can analyse the large deformation of film stretching and predict whether the kink band phenomenon occurs during the film transverse stretching. The validity of the simulation method was confirmed by the transverse stretching tests performed on the fluorine films with different longitudinal stretching ratios. Using the simulation method, we clarified that the plastic anisotropy index of the longitudinally stretched fluorine film has a great influence on the presence or absence of the kink band phenomenon during the film transverse stretching. The plastic anisotropy index of the longitudinally stretched fluorine film can be related to its birefringence, and the two are approximately in a linear relationship. Moreover, we revealed the change in film stretching deformation due to difference in the ratio of the stretching zone length to the width of the tenter.

Simulation of bearing capacity of pile in crushable soil

Scipedia content — Wed, 06 Jul 2022 17:29:13 +0200

Crushable soils such as volcanic soils, carbonate sand or decomposed granites whose grains are easily break under foundation pressure, especially, large magnitude of stresses under pile tips. When the grains are crushed, particle size distribution (PSD) varies followed by higher compressibility of these soils. Pile foundation's settlement in crushable soils tends to be increased. Nonetheless, design code for bearing capacity of pile in crushable soil is still unavailable leading to a lot of difficulties for engineers to have an appropriate foundation design. This paper introduces a constitutive model for soils which takes account of the breakage mechanics including the evolutions of PSD and the compressibility due to grain crushing. The model is implemented in a finite element code to simulate pile penetration in crushable soil. Finally, the particle breakage around pile's tip is examined.

Seismic Vulnerability Assessment of Historic Masonry Buildings through Fragility Curves Approach

Scipedia content — Wed, 06 Jul 2022 17:28:57 +0200

The assessment of the seismic vulnerability of built heritage is still an open issue. Regarding this topic, in recent years many researchers have worked in the development of refined numerical models to simulate the behaviour of different building typologies subjected to seismic action. To be reliable, these models require in-depth knowledge of the building object of study. In many countries, such as Italy, where the widespread historical heritage is widely present, there is the need to define quick, but reliable, evaluation procedures, which allow, in advance, to assess the vulnerability of the historical heritage of an entire area using databases already present without necessarily proceeding with detailed investigations on each building. Based on procedures in the literature, the authors have developed an assessment methodology focused on the construction of fragility curves, safety factor vs PGA and vulnerability index, which allows to formulate hypotheses on the probable behaviour of a specific type of building, to any similar actions and the probable expected damage. In the view of evaluating the seismic safety of a small historic centre in an area with a high seismic propensity, this procedure could be useful for prioritizing interventions in probabilistic terms.

Robust Design Optimization Under Uncertain Structural Parameters by Stochastic Simulation-Based Approach

Scipedia content — Wed, 06 Jul 2022 17:28:43 +0200

The inherent uncertainty in the structural parameters directly affects the structural performance, and its variation may lead to improper designs and catastrophic consequences. When subjected to uncertainty, the structure design must be optimized to get an insensitive design using a Robust Design Optimization (RDO) technique. Such design aims to find a system design in which the structural performance is less sensitive (insensitive) to the uncertainty of the inherent structural parameter without eliminating them. This is usually achieved by simultaneously minimizing the mean and variance of the structural performance function. Various RDO approaches, such as those based on Taylor series expansion, simulation-based methods, dimension reduction, and metamodel, can effectively take into account these uncertainties. However, the computational efficiency and accuracy in evaluating the mean and variance of the performance function remain a challenging task. To obliviate this limitation, a novel stochastic simulation-based approach is proposed in the present work. The proposed approach is built on an `Augmented optimization problem,' in which design variables are artificially considered an uncertain parameters. An unconstraint Genetic algorithm (GA)based optimization approach is formulated to determine the optimal solution. As the mean and variance frequently conflict with each other, so to obtain the Pareto optimum, a linear scalarized objective function is adopted. To demonstrate the proposed approach, RDO of a four-bar structure is performed. The results obtained are compared with the conventional Monte Carlo simulation approach and confirm that the proposed approach yields accurate results. This paper allows the designers to design the insensitive structure systems by minimizing the variance of the performance function. Moreover, the proposed RDO approach is not only limited to the civil structures but can also be enforced in the design of any realistic linear/nonlinear structures and systems such as machine components (like clutches, gears, etc.), aerospace, etc., having uncertainties in their geometry or material, such as the residual strain, modulus, thickness, density, etc.

Reproduction Method of Mechanical Anisotropy Induced by Rolling in Crystal Plasticity FE Simulation

Scipedia content — Wed, 06 Jul 2022 17:28:28 +0200

In this study, we investigate a method for accurately representing mechanical anisotropy in a crystal plasticity finite element (FE) analysis using a computational model with a small number of crystal grains to reproduce the rolling texture. We propose a method for extracting the preferred orientation of the rolling texture, construct a computational model using this method, and perform a crystal plasticity FE simulation.

Reducing velocity error and its consequences by an iterative feedback immersed boundary method

Scipedia content — Wed, 06 Jul 2022 17:28:11 +0200

The immersed boundary method (IBM) has attracted growing interest in the computational fluid dynamics (CFD) research community due to its simplicity in dealing with moving boundaries in fluid-structure interaction (FSI) systems. We present a study on streamline penetration, velocity error and consequences of a FSI solver based on an iterative feedback IBM. In the FSI, the fluid flows are solved by the lattice Boltzmann method; the solid structure deformation is solved by the finite difference method, and an iterative feedback IBM is used to realize the interaction between fluid and structure. The iteration can improve the no-slip and no-penetration boundary conditions at the fluid-solid interface. Four benchmark cases are simulated to study the reduced velocity error and its consequences: a uniform flow over a flapping foil, flow-induced vibration of a flexible plate attached behind a stationary cylinder in a channel, flow through a two-dimensional asymmetric stenosis and a one-sided collapsible channel. Results show that the iterative IBM can suppress the boundary-slip error and spurious flow penetration on the solid wall. While the iterative IBM does not have significant effect on the force production and structure deformation for external flows, it significantly improves the prediction of the force distribution and structure deformation for internal flows. The increased computational cost incurred by the iteration can be largely reduced by increasing the feedback coefficient. This study will provide a better understanding of the feedback IBM and a better option for the CFD community.

Reduced Order Modeling for modular anisotropic Structures based on Proper Orthogonal Decomposition and Mesh Tying

Scipedia content — Wed, 06 Jul 2022 17:27:52 +0200

A model order reduction technique in combination with mesh tying is used to efficiently simulate a large number of different structures that are assembled from a set of substructures. The stiffness matrices of the substructures are computed separately and assembled into a global stiffness matrix with tied contact formulation. The computational time can be further decreased by reducing the degrees of freedom of each substructure with a projection-based model order reduction technique. The precomputations to obtain the mode matrices are computationally cheap because they can be carried out on each substructure separately. For the development and optimization of new construction strategies for fiber reinforced concrete, a large number of different combinations of the modules have to be tested. The nonlinear anisotropic material behavior, like the primary directions of orthotropic materials, leads to parameter-dependent mode matrices. The precomputations can only be done for a relatively small number of parameters. For all other parameters, the mode matrices have to be adapted with interpolation methods to obtain an accurate solution .

Proposal of Crack Propagation Condition Criterion Considered Constraint Effect under Extremely Low Cycle Fatigue; Evaluation by 1T-CT and 2T-CT Specimen

Scipedia content — Wed, 06 Jul 2022 17:27:36 +0200

The strength evaluation of structures that requires high reliability, such as power generation facilities, is extremely important. It is necessary to ensure safety under extremely low cycle fatigue caused by earthquakes. However, a highly reliable evaluation method has not yet been developed because of variable fracture toughness due to the constraint effect with large deformation. The crack propagation criterion proposed by the previous study has needed some modification for accurate prediction. In this study, we confirmed whether the crack propagation criterion proposed by previous study can reproduce the fracture behavior of the experiment. Among then, relationship between the number of cycle and crack length, hysteresis loop, reproduction of crack shape were evaluation items.

Proposal of Crack Propagation Criterion Considered Constraint Effect under Extremely Low Cycle Fatigue; Evaluation by 1.5T-CT Specimen

Scipedia content — Wed, 06 Jul 2022 17:27:22 +0200

The prediction of fracture behavior under extremely low cycle fatigue due to excessive loading is necessary for the life assessment of structures. This study evaluates the validity of the crack propagation criterion proposed in a previous study by performing generation phase and application phase analysis based on the results of fracture tests on a 1.5T-CT specimen (SGV410). The analysis show that the crack propagation criterion in the previous study predicted the experimental behavior well, however crack shape was incomplete in reproducing the crack shape.

Preparing the path for the efficient simulation of turbulent compressible industrial flows with robust collocated RK-DG solvers

Scipedia content — Wed, 06 Jul 2022 17:27:08 +0200

We present an analysis of the performance of some standard and optimized explicitly Runge Kutta schemes that are equipped with CFL-based and error-based time step adaptivity when they are coupled with the relaxation procedure to achieve fully-discrete entropy stability for complex compressible flow simulations. We investigate the performance of the temporal integration algorithms by simulating the flow past the NASA juncture flow model using the in-house KAUST SSDC hp-adaptive collocated entropy stable discontinuous Galerkin solver. In addition, we present a preliminary analysis of the performance of the SSDC framework on the Amazon web service cloud computing. The results indicate that SSDC scales well on the most recent and exotic computing architectures available on the Amazon cloud platform. Our findings might help select a more robust and efficient temporal integration algorithm and guide the choice of the EC2 AWS instances that give the best price and wall-clock-time performance to simulate industrially relevant turbulent flow problems.

Prediction of warp distortion in circuit board using machine learning

Scipedia content — Wed, 06 Jul 2022 17:26:54 +0200

A convolutional neural network, which reproduce a function by data, was used to predict the amount of warp distortion of a four-layer circuit board in a reflow soldering process. The data used for training are material properties such as Young's modulus, board thickness, and residual copper content as input data, and the predicted warp distortion data is the amount of warpage of the circuit board obtained from the measurement. Since a number of distortion data to be predicted was insufficient to be used for training, a newly proposed data augmentation method used to increase a number of data. The augmentation method is evaluated through the result of the predictions and discussed.

Practical Boundary Conditions for Electronic Structure Calculations

Scipedia content — Wed, 06 Jul 2022 17:26:41 +0200

Computational materials design is an active area of research which aims at predicting physical and chemical properties of various materials from first-principles electronic structure calculations. To keep the computational costs manageable, the Schr¨odinger equations are often approximated by Kohn-Sham equations within the framework of density-functional theory. These Kohn-Sham equations are solved numerically either by a basis set expansion or real-space discretization under given boundary conditions. In the case of a plane-wave basis set, it is common practice to apply periodic boundary conditions in all directions, while isolated boundary conditions are more common for the atomic basis set. However, there are many other options besides these standard boundary conditions. In this presentation, we will explore several non-standard boundary conditions which exploit the characteristics of each system, such as surfaces, interfaces, and cyclic/helical structures, to minimize the computational costs of electronic structure calculations. Most of these boundary conditions are easily implemented by minor modifications of existing electronic structure codes. Numerical examples on a few model systems are also presented for the validation of these boundary conditions.

Physically based bead topology model coupled with electro-mechanical power source model applied for wire and arc additive manufacturing

Scipedia content — Wed, 06 Jul 2022 17:26:28 +0200

The present work is carried out in the framework of the WAS project [1] which deals with WAAM process. The process relies on an automatized welding process in which a part is built by successively deposed metal bead. We propose a physically based bead topology model using the equilibrium between the hydrostatic pressure and the capillarity force, under twodimensional hypothesis. This equilibrium can be described by the Laplace equation [2]. The proposed model is used to estimate a bead topology which is deposed on an inclined support. Moreover, a deposed melted metal volume is necessary for the bead topology model. By modelling a gas metal arc welding (GMAW) power source system [3], the volume can be estimated and be used as a physical parameter for the bead topology model. Combining the topology and the power source models, the coupling model allows to simulate the topology of a weld bead through WAAM. In addition to the modelling, experimental profiles of the beads are used to validate the model.

Part-scale Thermo-mechanical Modelling for The Transfusion Module in The Selective Thermoplastic Electrophotographic Process

Scipedia content — Wed, 06 Jul 2022 17:26:10 +0200

This study proposes a thermos-mechanical model for the transfusion module in the additive manufacturing process, selective thermoplastic electrophotographic process (STEP). The reduced-order method and parametric study are presented, as well.

LOWER BOUND LIMIT ANALYSIS OF MASONRY PLATES IN TWO- WAY BENDING BY MEANS OF FULL 3D ELEMENTS

Scipedia content — Wed, 06 Jul 2022 17:25:55 +0200

The paper provides a novel Lower Bound (LB) Limit Analysis (LA) Finite Element (FE) model for the study at failure of masonry walls in two-way bending by means of full 3D elements. The method of hexahedral discretization is used, while assuming infinite resistance and a quadrilateral interface where all plastic dissipation occurs. It can more accurately analyze the collapse mechanism of masonry panels in the process of two-way bending. It chose two cases to study. They are three series of panels with and without perforations tested at collapse at the University of Adelaide Australia and four series of solid and perforated panels tested at the University of Plymouth UK. The feasibility of the research method was verified. The obtained research results show that the use of the method proposed allows to provide a safe prediction of the existing LA code based on kinematics theorem, with a small computational burden, and the obtained results are more in line with the actual situation and have better practical effects.T The original abstract is titled: 'Out of Plane Lower Bound Limit Analysis'

On situ vibration-based structural health monitoring of a railway steel truss bridge: a preliminary numerical study.

Scipedia content — Wed, 06 Jul 2022 17:25:40 +0200

Railway network is subject to increasing travelling loads and traffic frequency. In addition, since most of the bridges were built in the last century, they are subject to ageing and degradation. It is therefore necessary to develop proper structural health monitoring systems that can support periodical visual inspections. In this context, direct monitoring systems represent an important and promising solution for structural health monitoring purposes. This paper is the result of a numerical study performed on a 3D FE bridge model based on an existing structure: the latter is a Warren truss railway bridge, located in Northern Italy, built few years after the end of the second world war. The purpose of the study is to numerically evaluate the effectiveness in damage detection and localization of different vibration-based techniques. This analysis has been performed for a set of different damage scenarios, suggested by the infrastructure managers.

Object Classification and Segmentation Based on Deep Learning Using Underwater Mapping Data

Scipedia content — Wed, 06 Jul 2022 17:25:25 +0200

This paper presents a fast and accurate classification method for underwater objects using underwater mapping data obtained by a small Autonomous Underwater Vehicle (AUV) and autonomous surface vehicle (ASV). For the mapping data, in addition to underwater acoustic reflection intensity images, water depth data, point cloud data and backscattering reflection intensity data are employed. We propose the automatic classification and semantic segmentation method on deep learning using a convolutional neural network (CNN) and PointNet++. In order to verify the effectiveness of the present method, we applied it to the measured several underwater mapping data.

Numerical study on the hydrate rich sediment behaviour during depressurization

Scipedia content — Wed, 06 Jul 2022 17:25:08 +0200

Exploratory studies have been carried out to identify the potential natural gas hydrate reserves for commercially producing gas. While extracting the gas from the hydrate-bearing sediments using various dissociation techniques, there will be a significant loss of strength in these sediments. It is well known that the behavior of gas hydrate sediments is governed by Thermo Hydro Mechanical Chemical THMC coupled process during the gas extraction. Thus, in this study, in order to understand the influence of depressurization at the well-bore and the permeability of the hydrate reservoir on the sediment deformation characteristics, a 2D (plane strain condition) hydrate reservoir is simulated (using a multiphase numerical schema). From the study, it is observed that the flow response, i.e., the rate of change of gas pressure near the well-bore, decreases with the increase in the duration of the extraction. The maximum settlement occurs for reservoirs having low well-bore pressure (higher amount of depressurization) and high intrinsic permeability. Additionally, these same reservoir conditions also lead to maximum cumulative gas production. Thus, the continuous gas extraction results in a highly porous medium that is stabilized primarily due to the geomechanical changes.

Numerical Simulation of Neck Propagation in Double Network Hydrogel

Scipedia content — Wed, 06 Jul 2022 17:24:52 +0200

In this study, we at first employ a nonaffine polymer chains network model to account for the irreversible structural change during the deformation of DN gels. And then, a finite element model of the DN gels under simple tension is constructed. On the other hand, neck propagation is one kind of localized instability and there will be a local transfer of strain energy from one part of the model to neighboring parts. To solve such unstable quasi-static problem, an automatic mechanism provided by Abaqus/Standard is employed. The simulation results show that the nonaffine polymer chains network model together with the stablization algorithm for localized transformation of strain energy can be employed to reproduce the phenomenon of neck propagation in DN gels very well.

Numerical simulation of interaction between two Savonius turbines aimed at practical application of ocean current power generation

Scipedia content — Wed, 06 Jul 2022 17:24:37 +0200

One of the vertical axis wind turbines that utilize drag force is the Savonius wind turbine. Savonius wind turbines are characterized by low speed rotation and high torque, so they are rarely used for wind power generation but have possibility to apply to ocean current power generation, which has been attracting attention recently. In this report, we actually performed a numerical simulation of the flow using suitable grid, focusing mainly on the case where two wind turbines are rotating in reverse at a constant speed, and investigated the state of the flow field. Two-dimensional incompressible Navier-Stokes equations are adopted as the basic equation and solved numerically using the finite difference method. In addition, in order to enable calculation even in a high Reynolds number flow, the nonlinear term of the equations are approximated by using the third-order accuracy upstream difference method. The simulation is performed under the condition that the flow corresponds to three types of angles of 90 degrees, 45 degrees, and 0 degrees with respect to the line connecting the centers of the two wind turbines. The flow field differs greatly depending on each angle, and the interaction between the two wind turbines has been clarified.

Numerical Evaluation of Bell-Shaped Proportional Damping Model for Softening Structures

Scipedia content — Wed, 06 Jul 2022 17:24:19 +0200

A new type of proportional damping models, called bell-shaped proportional damping model, has recently been proposed. This new model has not only addressed the spurious damping forces, but also maintained the same order of computational efficiency as the Rayleigh model. This model has also been further improved such that, by using the tangent stiffness approach, it becomes suitable for structures experiencing softening response with negative stiffness. The improved model allows users to have flexible control of modal damping ratio for all interested frequency intervals, including those associated with negative stiffness. In this study, the performance of bell-shaped damping model is evaluated numerically in a response history analysis of a multi-storey building under seismic loading. The results show that, compared to the Rayleigh model, the bell-shaped model performs excellently in terms of always giving desirable positive energy dissipation even when the structure is experiencing softening response.

Nonlinear Dynamic Characteristics and Resonant Actuation of Bi-stable Composite Laminates

Scipedia content — Wed, 06 Jul 2022 17:24:07 +0200

In the fields of morphing aircraft design, flow control and broadband energy harvesting, the dynamic characteristics of the multi-stable structure provide an idea for realizing the dynamic deformation of configurations. Its unique nonlinear characteristics and local strong stability provide an important theoretical basis and application value for the investigation of morphing structures. Taking asymmetric bi-stable composite laminates as the research object, this paper analyzes the effects of boundary conditions on the stable configurations and utilizes finite element simulation software ABAQUS to research the nonlinear dynamic characteristics of each configuration and its dynamic response under different excitation levels. By comparing two boundary conditions of cantilever and clamped at the center, the dynamic snap-through phenomena of bistable laminated panels are investigated, and the morphing strategies targeting modal frequencies need to be optimized.

New calculation scheme for compressible Euler equation

Scipedia content — Wed, 06 Jul 2022 17:23:51 +0200

In this paper, numerical demonstrations of a modified compressible Euler system are shown, where the bubble function element stabilization method together with adaptive mesh refinement is introduced for increasing numerical stability and numerical accuracy. For a test case, NACA0012 is selected as a domain of interest, and numerical results using finite elements of P1P1bP1 and P2P2bP2 for densityvelocitypressure were compared at AOA=1.25 and Mach number 0.8. As a result, the shock wave is not found on the upperend and the lower end of NACA0012 in the former, and on the other hand the latter is adequate numerical result and relative errors of Cl, Cd with previous study are 1.197% and 0.15376%. The mathematical model is much simpler than the compressible Euler equation, because they are advection equations for a density, a velocity, and a pressure with each external forces. Therefore, the material derivative is considered for time stepping, and the characteristic curve method can be used for decreasing calculation cost.

Neural Network-Based Surrogate Models Applied to Fluid-Structure Interaction Problems

Scipedia content — Wed, 06 Jul 2022 17:23:36 +0200

Traditional computational methods face significant challenges with ever-increasing complexity in the problems of engineering interest. One category of problems that suffer from this phenomenon is those where Fluid-Structure Interaction (FSI) is present. One set of problems that suffer from this phenomenon is those where Fluid-Structure Interaction (FSI) is present. FSI simulations are traditionally time-consuming and computationally extremely expensive. Potential alternatives rely on using a surrogate model to substitute one or more systems involved. A promising approach employs artificial neural networks as the basis for such a surrogate model combined with strong physics simulations based on finite element methods (FEM). This approach requires the seamless integration of AI algorithms and packages into the simulation workflow. Such an example is the NeuralNetworkApplication developed in KratosMultiphysics. The routines related to the neural networks are executed through an interface with the Keras API. Mok's benchmark is chosen as the study case to test the capacity of the previous method applied to FSI problems. Two cases in which one of the systems is substituted by a neural network-based surrogate model are analyzed. Strong and weak coupling scenarios are considered. The results present improvements in simulation time without sacrificing accuracy, especially when compared with the original benchmark. This contribution discusses the influence of the original data and network architecture on the simulation outcome and different considerations for generating surrogate models for FSI.

On the Performance of Different Architectures in Modelling Elasto-Plasticity with Neural Network

Scipedia content — Wed, 06 Jul 2022 17:23:21 +0200

Constitutive models have been utilized to study the mechanical behaviors of solid material. The formulation of constitutive relations is difficult and could be associated with limiting hypothesis. This work proposes neural network-based approaches to reproduce the complex nonlinear constitutive relations of solid materials including elastic behavior and plastic deformation. It is shown that the proposed history-based and internal variable-based strategies can represent exactly the von Mises elasto-plastic material model in uni-axial stress state. Furthermore, close investigation suggests that the internal variable-based approach is most suitable.

Multiscale Modelling of Normal Fault Rupture-Soil-Foundation Interaction

Scipedia content — Wed, 06 Jul 2022 17:23:04 +0200

A multiscale approach that couples the finite element method (FEM) and the discrete element method (DEM) is employed to model and analyses the earthquake fault rupture-soilfoundation interaction (FR-SFI) problem. In the approach, the soil constitutive responses are obtained from DEM solutions of representative volume elements (RVEs) embedded at the FEM integration points so as to effectively bypass the phenomenological hypotheses in conventional FEM simulations. The fault rupture surfaces and shear localization patterns under normal faults with or without foundation atop have been well captured by the multiscale approach and verified with available centrifuge experimental and numerical results. By examining the responses and microstructural evolutions of local RVE packings, it is found that the RVEs located in- or outside the shear bands (SBs) behave distinctly, and may change their stress states from initial at-rest to active in the normal fault case. The micromechanics study also sheds lights on the possible detriment of heavy foundations for the superstructure despite the rupture surface diversion.

Multi-Region and Multi-Component Thermal Fluid Analysis of Hydrothermal Oxidative Decomposition Reactor

Scipedia content — Wed, 06 Jul 2022 17:22:48 +0200

To elucidate the corrosion mechanism of a hydrothermal oxidation decomposition reactor for the treatment of polychlorinated biphenyls (PCBs), a coupled thermal fluid analysis of the heat transfer between two mixtures of fluids with different physical properties and the reactor body was executed using OpenFOAM. Based on the analysis results, we propose a method to evaluate the corrosion risk at the solid-liquid interface by focusing on three factors: (1) the corrosion temperature of reactor vessel, (2) the amount of fluid deposition that causes corrosion, and (3) the wall shear stress on the solid-liquid interface. Variation of corrosion risk with operating conditions of the reactor is discussed.

Multiple solvers for implicit temperature calculation of heat conduction with the MPS method

Scipedia content — Wed, 06 Jul 2022 17:22:29 +0200

In this study, an implicit algorithm and different solvers are applied to the Moving Particle Semi-Implicit (MPS) method for temperature calculation. The original MPS method uses an explicit method for temperature calculation and is limited by time increment due to diffusion number. In this paper, the heat conduction of plates with Dirichlet boundary condition and Neumann boundary condition is studied. The accuracy of explicit and implicit calculation of plate heat transfer cases are compared. In addition, different solvers are compared. Consequently, it is shown thatthe error of the implicit algorithm is not much different from the original one. And CG is still the better solver,CGS is also a superior solver. The implicit algorithm increases the size of a single time stepby a maximum of 50 times (original diffusion number is 0.2), while the calculation time of a single time step does not increase Substantially, so it has a significant effect on the acceleration of calculation.

Multi-body Rope Approach for the Form-Finding of Shape Optimized Grid Shell Structures

Scipedia content — Wed, 06 Jul 2022 17:22:11 +0200

Over the past decades, different approaches, physical and geometrical, were implemented to identify the optimal shape, reducing the internal stresses, of grid shells and vaults. As far as their original organic shape is concerned, the design of grid shell structures inspired architects and structural engineers worldwide and in any time. The method, here presented, is developed and extended, from its original formulation, employing a self-made code based on the dynamic equilibrium, ensured by the d'Alembert principle, of masses interconnected by rope elements in the space-time domain. The equilibrium corresponding the optimized shape to be defined, is obtained through an iterative process in the falling masses connected by a net for the definition of the 'catenary surface' coinciding with the best shape of the shell (form minimizing the bending moment) according to the conditions of zero velocities and accelerations of the nodes. The implementation of the method is realized in MATLAB and set up for Python in an interpreted high-level general-purpose programming language. By the use of this code as well as its object-oriented architecture the MRA Python code will be linked to the Grasshopper environment for the direct visualization of the shapes and their fastparametrization phase.

A SMART PASSIVE YAW DAMPER FOR THE REDUCTION OF LATERAL CONTACT FORCES IN LOW-RADIUS CURVED TRACKS

Scipedia content — Wed, 06 Jul 2022 17:21:56 +0200

High-speed trains are equipped with yaw dampers to prevent the arising of hunting motion. These suspension components play an important role in improving the vehicle stability. However, the presence of yaw dampers increases the steering resistance of the bogies, especially in transient curve track segments. For this reason, passive yaw dampers are designed according to a tradeoff between improvement of high-speed stability and limitation of curving performance degradation. This paper introduces an innovative passive smart yaw damper, the Position Dependent Yaw Damper, able to overcome the typical limitations of standard passive components. The damper can variate its dynamic performances according to the operating conditions of the vehicle. In this paper, a PDYD prototype will be experimentally characterized. Then, a numerical model of the damper will be tuned on the experimental data. The model aims at predicting the influence of the PDYD on the dynamic performances of a rail vehicle, simulated with a Multibody model. A sensitivity analysis will assess the relationship between different PDYD layouts and the vehicle curving performances co-simulating damper and vehicle models. The numerical comparison will be focused on the low-speed negotiation of low radius curves. Finally, the best PDYD layout will be implemented in a numerical simulation of a high-speed high-radius curve to verify its effectiveness in reducing the arising of hunting unstable motion.

Modelling of forming processes using the Particle Finite Element Method (PFEM)

Scipedia content — Wed, 06 Jul 2022 17:21:39 +0200

In this work we present the latest advances in the Particles Finite Element Method (PFEM) for the numerical modeling of forming processes. In the recent past, very good results of the method have been shown in the simulation of 3D cutting problems. The method has very good capabilities for treating large deformations in massive volumetric parts. Now the method is applied and extended to other forming operations: forging, blanking, minting, machining, etc., for metals and other materials. One of the important aspects of these manufacturing techniques is the interaction with the molds and dies. Deformable contact interactions are needed to obtain a close correspondence between numerical and experimental results. The characterization of the thermomechanical interaction with the coatings of the tool plays an important role. Advances have been made in meshing techniques for treating threedimensional parts and for the modeling deformable contact. The characterization of friction and wear of the forming tools can be modeled considering also the lubrication on the surfaces. The purpose is to obtain the characteristics of the final shape of the workpiece, the areas that experience large plastic deformations and the residual stresses that remain in the processed material. This information is very valuable for the optimal design of the manufacturing operation. To show the virtues of the method, several examples of forming operations are presented. The capabilities of the method are discussed, as well as the accuracy of the solutions.

Modelling landslide debris flow with entrainment: development and validation

Scipedia content — Wed, 06 Jul 2022 17:21:25 +0200

The volume and mobility of a debris flow could increase with distance travelled as it has the potential to entrain a substantial amount of channel-bed material along its travel path. This entrainment effect renders the debris flow more devastating to downslope populations and facilities. Over the past two decades, the Geotechnical Engineering Office (GEO) of Hong Kong has expended considerable effort to develop debris mobility modelling tools for use in routine engineering practice for forward prediction purposes. Recently, GEO has completed a study to enhance an in-house debris mobility code. Physical parameters which can be estimated from the field by engineers or geologists are incorporated in the code to predict entrainment effects in a simple and rational manner. This allows the modelling of varying entrainment potential along a debris flow path. The code has been checked against simplified analytical solutions and validated against field observations in a major historical landslide event involving highmobility debris flows in Hong Kong. The numerical modelling results indicated that simulated entrainment volume and mobility characteristics are broadly consistent with geological field mapping records.

Modelling and validation of Selective Laser sintering of PA12

Scipedia content — Wed, 06 Jul 2022 17:21:10 +0200

One of the larger growing fields within additive manufacturing is the selective laser sintering process of semi-crystalline polymer powders. The powder is locally fused at certain areas, due to the energy output of a laser. This method allows for rapid production of complex parts, which are well suited for prototyping. The overall accuracy and stability of the process along with part properties are highly related to the process parameter. A better control of these parameters will therefore optimize the process even further. The current paper propos a numerical modelling approach and the model makes it possible, to analyze the influence of the laser-related input parameters concerning the temperature distribution and size of the melt pool. For the validation, certain outputs from the model are compared to the ones found from experimental single-line track data, where the melt pool geometry can be compared to the numerical measurements.

Modeling Freely Flying Monarch Butterflies Using a Strongly Coupled High Fidelity Numerical Framework

Scipedia content — Wed, 06 Jul 2022 17:20:52 +0200

Flying insects are impressive creatures due in part to their small size and agile flight maneuvers. Additionally, butterflies can be highly efficient fliers, as evidenced by monarchs having the longest migration amongst insects. To begin uncovering the complex mechanisms enabling monarchs to migrate roughly 80 million times their average body length, high-fidelity modeling tools are required: These tools must consider the distinguishing features of monarchs their low flapping frequency, high Reynolds number (amongst insects), large wings relative to their body, low wing loading, flexibility of their wings, and the highly coupled interplay between the instantaneous wing aerodynamics and dynamic body response. Many butterfly flight models to date have neglected the passive wing pitching arising from butterfly's flexible wings. Here, we propose a framework that tightly couples the effects of all three physics solvers using a dynamic relaxation scheme. As such, the highly nonlinear interplay between fluid, body, and passive wing dynamics is efficiently accounted for in each time step. We apply the model to the free flight of monarch butterflies, resulting in stable motion for many periods without any controllers.

Modeling and numerical simulations of MEMS shutter devices

Scipedia content — Wed, 06 Jul 2022 17:20:35 +0200

We investigate the acoustic behaviour of Micro-Electro-Mechanical-Systems (MEMS) with a focus on shutter devices. These shutter devices can be used for a new method of sound generation which we call Advanced Digital Sound Reconstruction (ADSR) where a redirection mechanism for sound pulses is incorporated [1]. With the help of this redirection mechanism, sound pulses can be generated which are superimposed to form an audio signal. At MEMS-scales viscous effects can play a major role regarding sound transmission. Therefore, we utilize the linearized flow equations in time domain in order to solve for the acoustic pressure while incorporating effects caused by viscous boundary layers. Furthermore, the movement of the shutter itself contributes to the overall generated sound in a negative manner. Since the generation of the sound pulses is in the ultra sound range, the generated noise by the shutter might lead to adverse effects on the human body [2]. Hence, modeling the shutter noise and understanding its generation process can help to improve the design. To model the noise generated by the shutter, we apply the arbitrary LagrangianEulerian (ALE) framework to the linearized flow equations to be able to compute the noise generation on the moving geometry. The geometry update itself is governed by an artificial quasi-static mechanical problem which is solved in each step to get the new element deformation [3]. Assuming that the impact of the acoustic pressure is negligible, a simple forward coupling from the quasistatic mesh-smoothing to the the linearized flow equations is employed. Furthermore, we use a direct coupling approach to couple the acoustic wave equation to the linearized flow equations. The final coupled system is then used to characterize the impact of the shutter movement on the overall system behaviour of a certain embodiment.

Modeling and Analysis of Real World and Industry Applications with Geomiso SEA: a New Hybrid CAD/CAE Software for Inelastic Static Isogeometric Shell Analysis and 3D Design with Advanced Spline Techniques

Scipedia content — Wed, 06 Jul 2022 17:20:21 +0200

In this paper, the new Geomiso SEA software (www.geomiso.com) is proposed for inelastic static isogeometric analysis with shell elements and splines. Geomiso SEA offers an innovative way to merge geometric design with mesh generation, by creating, with its modern user interface, 3D models as tensor product grids. The utilization of the exact mesh for analysis eliminates geometric errors, while there is no need of repeating the geometry design for refinement purposes. In contrast, the standard finite element technique, not only cannot fully utilize the available data ofthe exact mesh, but also makes engineers unable to benefit from advanced spline techniques. Real world and industry applications on both thick (Mindlin-Reissner) and thin (KirchhoffLove) shells are demonstrated with a comparison between Geomiso SEA and FEA programs with shell and hexahedral elements.

Modeling and Analysis of Real World and Industry Applications with Geomiso ISA: Α New Hybrid CAD/CAE Software for Static Isogeometric Analysis with Plate Elements and Advanced Spline Techniques

Scipedia content — Wed, 06 Jul 2022 17:20:06 +0200

In this paper, we propose Geomiso ISA (www.geomiso.com), a new hybrid software for applications on static isogeometric analysis with plate elements. It is based on the IGA, the powerful generalization of the traditional FEA, which, in combination with the plate theory, has attracted increasing attention in construction industry over the last decade, as it achieves efficient design-through-analysis procedures and shows superior performance. This recently developed program is not just a plug-in, but a both on-premises and cloud-based software solution, applicable to thin (Kirchhoff-Love) and thick (Mindlin-Reissner) plates. It is used to simulate spline models of slabs and analyze their strength and behavior, while it has many features in common with both FEA software and design programs. This software solution addresses the rising industrial need for seamless integration of CAD and CAE, while it appears to be more efficient to FEA software packages with major improvements, as it facilitates the geometry modeling within analysis, and achieves superior accuracy per degreeof-freedom with shortened computational cost. This is the first time ever such a cloud-based program has been developed.

Mitigation of Seismic Pounding between Adjacent Buildings by means of Isolation and Supplemental Dissipation at the Base

Scipedia content — Wed, 06 Jul 2022 17:19:52 +0200

Double concave surface slider (DCSS) is considered as an effective solution for baseisolation of existing structures located in a near-fault site, because of its capacity to notably increase horizontal displacements that can be accommodated in comparison to a single concave surface slider (SCSS) of identical in-plan dimensions. However, unexpected torsional pounding of in-plan irregular adjacent structures may be induced by variability of friction force and lateral stiffness of SCSS and DCSS, depending on the axial load and friction coefficient changes during an earthquake. Effectiveness of supplemental viscous damping at the base is studied in this work with the aim to analyse its effectiveness for limiting base displacement, so avoiding too large seismic gap requirement. Structural pounding between fixed-base and baseisolated L-shaped buildings, placed adjacent to form Tand C-shaped plans, is analysed. A simulated design of the original reinforced concrete (RC) fixed-base framed structure is preliminarily carried out in accordance to a former Italian code, for a medium-risk seismic zone. Then, seismic retrofitting with SCSSs is carried out, in order to attain performance levels imposed by the current Italian code in a high-risk seismic zone, while DCSSs have radius of curvature equal to half the SCSSs and the same friction coefficient. The insertion of additional fluid viscous dampers (FVD) at the base is examined, following damping distribution inversely proportional to the distance between the stiffness centre of the base-isolation system and the plane frame where each FVD is placed. Nonlinear modelling of SCSSs and DCSSs considers variable axial load combined with friction coefficient at breakaway and stick-slip and as function of the sliding velocity, axial pressure and rising temperature at the sliding interface. Attention is focused on the pulse-type nature of near-fault earthquakes generally observed in the velocity time-histories but largely overlooked in the acceleration ones. Automated classification algorithms using wavelet analysis are adopted to compile three datasets of seismic input rotated in the range 0°-360°, with a constant step of 15°. Distinction is made between no-pulse and velocity-pulse, the latter further categorised into non-acceleration and acceleration-pulses.

Mechanism of delayed leaching of heavy metals from naturally contaminated soils

Scipedia content — Wed, 06 Jul 2022 17:19:39 +0200

Naturally contaminated soils that contain contaminants deep within the particles may show delayed leaching. To incorporate this, a novel approach for predicting the distribution of contaminants, both in the soil particle and surrounding liquid, is achieved using the finite difference method. The approach is named the 'intraparticle pore-diffusion model' and is applied to simulate the batch leaching test of heavy metal contaminated soils. Intraparticle diffusion and sorption equilibrium are considered. The desorption phenomena of heavy metal from soil particles are considered as a one-dimensional, polar-symmetric problem in the spherical coordinate system by supposing soil particles to be porous, perfect spheres. The results indicate that soil constituted of larger particles leach more contaminants at a certain time and faster for a certain leaching amount.

Material Cost Minimization Problem for Aluminum Alloy Beam using Beam String Structure

Scipedia content — Wed, 06 Jul 2022 17:19:21 +0200

Aluminum alloy is a light-weight material with excellent corrosion resistance but low rigidity. When the aluminum alloy is used to a girder bridge, it takes high costs owing to the increment of its stiffness. Therefore in order to reduce a material cost, the cost minimization problem was performed on beam string structure (BSS) made of the aluminum alloy material based on the results of the topology optimization. We focused on the layout of the BSS and diameter of the cable. The conducted simulation made clear the effectivity of the BSS to the aluminum alloy material for a reduction of material cost and increment of the beam span.

Local Peak Pressure on Super High-rise Building in Actual Urban Area

Scipedia content — Wed, 06 Jul 2022 17:19:06 +0200

In this study, the characteristics and cause of local peak pressure observed on the surface of a super high-rise building with lower parts in an actual urban area are investigated through a relationship with the flow characteristics. A large-eddy simulation (LES) of a high-density area including several super high-rise buildings is carried out using the turbulent inflow boundary condition. It is confirmed that the large peak suction near the windward corner of the target building is induced by the development of strong conical vortex. The rotation of a conical vortex is accelerated by the separated shear layer generated by the windward building and the lower part of the target building when negative peak pressure occurs.

LES on wind pressure acting on high-rise building under strong wind events of Typhoon

Scipedia content — Wed, 06 Jul 2022 17:18:52 +0200

This study predicts wind pressure on high-rise buildings under typhoons by LES using CUBE and discuss the effects of turbulence fields obtained from broad region simulation and fine vortex structure around complicated facade on wind pressure. First, the computation of broad region including many high-rise building is carried out. The computation reveals that structures with streamtwise vorticity appears from the upper corner of high-rise building and remains even in 1km leeward region. Then, the computation resolving the complicated façade of two buildings is carried out and turbulent structure around the complicated façade is examined. The result shows that it is possible to show local wind pressure induced by fine structure of vortex by the computation with high spatial resolution resolving the shape of unevenness on building façade.

LES around a Realistic City Block Designed Based on a Future City Concept

Scipedia content — Wed, 06 Jul 2022 17:18:38 +0200

In this study, we discuss the flow field of the realistic city block model planned according to the concept of the future city, in the case of an actual typhoon and a winter monsoon hit. This study applied BCM-LES technique, which enables large scale simulation with high efficient of parallel computing. The fluctuating inflow of the actual typhoon was created by using the method of adding the turbulent component based on WRF-LES. From the computed results, we confirmed that properties of inflow and the location of high-rise buildings affect the flow field and the pressure distribution of target high-rise building.

LES Analysis of Ventilation Performance and Wind Gust Occurrence for Strategic Urban Transformation

Scipedia content — Wed, 06 Jul 2022 17:18:27 +0200

In order to achieve desirable urban redevelopment in the near future, various transformation strategies were investigated using LES, focusing on their impact on ventilation performance and wind gust generation. This study evaluated the replacement of city blocks with high-rise buildings, replacement with mid-rise buildings lower than the surrounding area, and simple multi-building arrangements utilizing the prevailing wind direction.

Lateral Resistance of Buried Pipes by Frictional Limit Analysis

Scipedia content — Wed, 06 Jul 2022 17:18:11 +0200

Pipelines are vital means of transportation of liquids and gases over large geographical areas. Regarding buried pipes, they are submitted to thermal and mechanical loads due to their support conditions, pipe-soil friction and the surrounding soil mass. Under high compressive loads carried out by these efforts, loss of stability and buckling may occur. Then, the evaluation of soil lateral resistance that will cause a imminent breakout is important. This work aims the analysis of the soil lateral resistance by frictional limit analysis formulation, considering the soil mass as a deformable body and the pipe as a rigid one. An yield function considering material porosity and material friction angle is considered. The soil lateral resistance forces obtained from the proposed formulation are compared to a those ones considering the limit analysis lower bound found in literature. The fully bounded condition observed in most models is also discussed.

Isogeometric analysis for 3D printed concrete monoclinic Timoshenko beam

Scipedia content — Wed, 06 Jul 2022 17:17:56 +0200

Anisotropy is one of the most important characteristics of 3D printed concrete. If material property is only symmetric on one plane, it is called monoclinic material, in which there are totally 13 independent elastic constants. In this paper, 3D printed concrete Timoshenko beam is analysed using isogeometric technique considering the monoclinic material property. Non-uniform Rational B-Spline(NURBS) functions are used as basis functions to integrate with computer aided design data. In addition, several numerical experiments are conducted to verify accuracy of the isogeometric analytical model. It is demonstrated that the proposed method in this paper can be widely used in analyses of 3D printed concrete monoclinic Timoshenko beams.

Interaction between Indoor and Outdoor Air Pollution in Natural Ventilating Building: Application to Sense-City urban area

Scipedia content — Wed, 06 Jul 2022 17:17:41 +0200

As majority of people spend 90% of their time in indoor environment, air quality has become an important scientific field in the last few decades. Indoor air quality is affected by many factors. One of the significant factors is outdoor air pollutions [1]. They enter the indoors through ventilation systems or natural ventilation and may stay indoors for a long time due to the airtightness of buildings. The present study especially focuses on nitrogen dioxide (NO2) concentration in a natural ventilating room that comes from outdoor pollutant sources such as vehicle emissions. In the present study, we have performed numerical simulations of a controlled environment in Sense-City urban area [2]. Sense-City is a unique full-scale equipment that can reproduce controlled conditions of temperature, humidity, airflow and pollution using an atypical climatic chamber. Reynolds Averaged Navier-Stokes (RANS) simulations have been carried out to calculate indoor and outdoor NO2 concentrations. RANS simulations are performed in two steps: district scale and building scale. Pressure values and pollutant concentrations are extracted from the district scale simulation and applied to the building scale simulation as boundary conditions. As expected, a sensitivity analysis study shows that the NO2 concentration in the building depends mainly on the pollutant concentration at the windows. Once opening windows, indoor pollutant concentration reached the almost same level of that of outdoor within a few minutes. Therefore, the interaction between indoor and outdoor air quality cannot be negligible for indoor air quality. This study can be useful for engineers and for local authorities to understand the importance of considering the interaction of the indoors and outdoors, the potential and limitation of RANS simulation in a natural ventilating. Considering the limitation of the number of sensors for air pollution in real applications, Computational Fluid Dynamics (CFD) is promising to obtain air pollutant distribution cartography. It can also be used as a decision-support tool for relevant urban planning such as the optimal placement of sensors and depolluting systems in urban areas.

Full-Waveform Inversion of Seismic Input Motions at a Domain Reduction Method Boundary in a PML-truncated domain

Scipedia content — Wed, 06 Jul 2022 17:17:25 +0200

A new inverse modeling is investigated for identifying an effective seismic force at virtual interfaces and estimating the seismic wave motions in an interior domain surrounded by a domain reduction method (DRM) boundary from limited seismic measurement data. The two-dimensional domain is truncated by the highly efficient non-convolutional second-order complex-frequency-shifted perfectly matched layers (CFS-PML), and the DRM is utilized to model seismic input motions coming from the outside domain of the CFS-PML. A partial differential equation (PDE)-constrained optimization method aims at minimizing a misfit between measured ground motions at sparsely-distributed sensors on the surface induced by surface wave-dominant incident waves (or equivalent effective forces on a DRM layer) and their estimated counterparts induced by inverted effective forces. The numerical results show that the presented full-waveform inversion of seismic input motions can identify an effective seismic force at a DRM layer and reconstruct the seismic wave responses in a near-surface domain.

Forensic Evaluation of Historic Shell Structure: Development of In-Situ Geometry

Scipedia content — Wed, 06 Jul 2022 17:17:05 +0200

When completed in 1961, the roof of St. Charles Church became the largest unbalanced hyperbolic paraboloid structure in the world and the only shell structure in Spokane, WA. Situated on an 8-acre site on the north side of the city, St. Charles is a modernist structure designed through partnership of Funk, Molander & Johnson and architect William C. James. This asymmetric structure is over 45.72m (150ft) and utilizes folded edge beams that taper from 1067mm (42in) at the base to a 76.2mm (3in) thickness at the topmost edge using regular strength reinforcing steel and concrete. The novelty of the shell structure serves both architectural and structural design criteria by delivering a large, uninterrupted interior sanctuary space in materially and economically efficient manner. Having previously completed an initial analysis of the structure, now, 60 years later, a complete structural forensic evaluation of the shell has been conducted using full point cloud laser scanning to generate a complete in-situ model. The in-situ geometry and historic loads are described and deflections as first steps in a full structural forensic study. Results of the current in-situ geometry are compared to the design geometry of original construction documents.

Force method conception using transfer matrix to apply to multiphase flow by one-by-one corresponding Particle-Cartesian cell (P/CC) model

Scipedia content — Wed, 06 Jul 2022 17:16:50 +0200

This work presents a novel force method for multiphase flow in which displacements and forces progress while strains terminate on surfaces between two different phases, such as the surface between air and liquid. This report is part of a research project to apply Helmholtz decomposition (H-d) to the finite element method. State vectors continues to exist on the surface of multiphase. The conventional scheme uses displacement method and applies a model to set Dirichlet boundary conditions for air on the air-liquid interface. The proposed scheme allows simulating it without such modeling.

Finite element quantitative analysis and deep learning qualitative estimation in structural engineering

Scipedia content — Wed, 06 Jul 2022 17:16:37 +0200

In the past two decades, finite element method (FEM) has been widely used to study mechanics of solids, fluid–structure interactions, and building construction strategies. FEM has been rapidly grown all over the world due to development of computer technology. Computer has much more powerful computing capability than humans. However, structural engineering education not only focused on teaching engineers to use FEM as computation tool, but also concentrated on cultivating engineers’ capability of experience-based qualitative analysis. In addition, artificial intelligence techniques have been rapidly developed in recent years. It is demonstrated that human experience-based capabilities might also be replaced by deep learning methods in various game-playing areas. Thus, this study aims at exploring what role artificial intelligence techniques will play in the futural structural analysis area. In this paper, several finite element analyses are carried out for three representative boundary value problems, such as tightly stretched wires under loading, soil seepage, and plane stress. Corresponding deep neural networks are trained using FEM simulation data to quickly and accurately predict results of relevant problems. It is indicated that to some extent artificial intelligence technique might replace human experience-based qualitative analysis as a surrogate of FEM.

Filtering Spurious Eigenmodes in Electromagnetic Cavities Discretized by Energy-Orthogonal Twenty-Nodes Hexahedral Finite Elements

Scipedia content — Wed, 06 Jul 2022 17:16:25 +0200

Extraction of Disaster Area from Satellite Image by combining Machine Learning and Image Processing Technology

Scipedia content — Wed, 06 Jul 2022 17:16:12 +0200

In recent years, heavy rain which frequently occurred in various places in Japan have been caused severe damage. It is important to identify the damaged area for disaster recovery and reconstruction. In this study, we focus on the optical satellite images that are easy to process and interpret, and extract the damaged area by combining a land cover classification method using machine learning and an additive color mixture method. As the results, it is possible to visually express the land cover changes before and after the disasters in a specific category and to extract the damaged area from the optical satellite image.

Experimental Investigation of the Static and Dynamic behaviors of 3D-Printed Shell Structures

Scipedia content — Wed, 06 Jul 2022 17:15:54 +0200

Over the last years, several optimization strategies were conducted to find the optimal shape minimazing internal stress or total weight (volume) of shell structures. In recent times, this structure typology gained a great importance among researchers and the scientific community for the renowed interest in the form-findind optimization of column-free space solution for large span roofing constructions. In the present paper, a form-finding of a shallow grid shells was introduced basing on the multy-body rope approach (MRA) for the definitions of vault shapes and different hole percentage. In order to obtain an experimental validation, a physical model was reproduced at the laboratory scale performing ad hoc measurements to compare the observed respect to the simulated behaviour. A 3D printing procedure based on the Fuse Deposition Modeling (FDM) technique in polylactide (PLA) material was used to realise form-works of the cement based blocks of the scaled prototype. Several static and dynamic load configurations are investigated, collecting into a sensitivity analysis the parameters which mainly affect the structural behaviour. To simulate earthquake ground motion an assigned frequency range as dynamic input to the structure was provided by a shaking table. Finally, some preliminary considerations of the dynamic response of the model were provided testing the robustness of the form-finding approach when horizontal load are taken into account.

Estimation of Distribution Algorithm for Constrained Optimization in Structural Design

Scipedia content — Wed, 06 Jul 2022 17:15:37 +0200

Nowadays, the need to deal with limited resources together with the newly discovered awareness of the human over-exploitation of the environment, has made the optimization a cutting edge topic both in scientific research and in the different professional fields. In this paper, a particular evolutionary optimization algorithm is presented: The Estimation of Distribution Algorithm (EDA). This type of algorithm has been developed to be used in search-based constrained optimization problems which are difficult and time-consuming to be solved by other general algorithms. Being an evolutionary algorithm, the main idea is to generate a population of solutions and evaluate the objective function of each one of them. Then, using the information obtained from the previous generations, the algorithm step-by-step will generate new populations that will tend to the best value of the objective function. In EDA, the population of solutions defines a probability density function (PDF) and, by integration, a cumulative density function (CDF), which is used for the generation of the next generation. In structural design optimization problems, it is very common that the best solution is very close to the constraint function. The main advantage of applying the EDA for constrained optimization problems is that each generation of solutions is obtained starting from a PDF that is defined on the whole domain. This means that, for each generation, the solutions have a probability to be on the unfeasible domain space, maintaining the information about the objective function in the evolution process. In the present research, an original EDA and related self-made code are presented together with a specific application to structural optimization problems, in order to show the effectiveness of the obtained results and to make a comparison with other evolutionary optimization algorithms.

Estimation of the state of matter in young impact craters on the Moon based on the orbital observations

Scipedia content — Wed, 06 Jul 2022 17:15:20 +0200

The report examines the results of a 3D-survey of the relief in young impact craters based on high-resolution images obtained from lunar orbits. The craters examined included: the Tsiolkovsky and Aitken craters on the far side of the Moon, the Ticho and Ina craters of the visible hemisphere, as well as the Orientale Mare in the marginal zone of the Moon. To build 3D-models, orbital images of the Soviet spacecraft'Zond-6,-8' and the American spacecraft 'Apollo-17' delivered to Earth, as well as images transmitted to Earth from the Lunar Reconnaissance Orbiter (LRO) were used.