Documents published in Scipedia

• Space-time analysis for the container problem

  M. Göttlicher

  WCCM2024.

  
  

  Abstract

  The container problem describes the behaviour of elastic porous media in a rectangular container, which is completely saturated by an ideal incompressible liquid. By time the liquid extrudes on the surface of the container while the stress resulting from a given top load acts on the shrinking elastic solid due to its compression. The analysis bases on a space time potential that contains a linear elastic term, a darcy flow term, and a boundary load term. The variation of the potential results in a space-time principle. Its minimum preserves approximately equilibrium over space and time.

  Abstract
  The container problem describes the behaviour of elastic porous media in a rectangular container, which is completely saturated by an ideal incompressible liquid. By time [...]

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• Three-field model for wave propagation in porous media based on mixture theories

  B. Campos, R. Gracie

  WCCM2024.

  
  

  Abstract

  Simulations of wave propagation in porous media are important to the understanding of various phenomena, such as seismic effects and non-destructive testing. The derivation and implementation of finite element analysis for a fully dynamic three-field deformable porous media model based on the de la Cruz and Spanos (dCS) theory [1] is presented. The dCS theory accounts for the fluid viscous dissipation mechanism and nonreciprocal solid-fluid interactions, which are neglected in Biot theory [2]. While the Biot theory is based on experimental data, the dCS theory is derived from mixture theories associated with the volume fraction concept and representing the connection between micro and macro pore scales. dCS results presented build upon recent FE model for quasi-static analysis [3]. Here, for the fully dynamic case incorporating both fluid and solid inertia, the accuracy and robustness of the FEA model is verified by wave propagation examples in one and two dimensions. Time integration scheme utilized and the changes in convergence rates according to how strongly coupled is the system will be discussed. The required element approximation order for all variables to ensure numerical stability will be demonstrated. The presented model is compared with the results from Biot theory, allowing one to observe the differences between the two theories and their relevance. The solutions in the time and frequency domain are also discussed, where the analysis of the correspondent eigenproblem leads to important information regarding wave velocity and attenuation.

  Abstract
  Simulations of wave propagation in porous media are important to the understanding of various phenomena, such as seismic effects and non-destructive testing. The derivation [...]

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• Development of high-strength wooden pallets utilizing local timber from Ehime Prefecture

  X. Zhu, A. Ochi, T. Kaneko, D. Ito

  WCCM2024.

  
  

  Abstract

  Wooden pallets account for a large percentage of pallets indispensable for logistics. From the viewpoint of strength and rigidity, pallets made of foreign timber (e.g., American pine) are the mainstream, and pallets made of domestic timber, especially cypress and cedar, which are inexpensive in terms of log price, are rarely distributed. The objective of this research is to develop a domestic wood pallet with high strength and rigidity comparable to that of American pine. Structural analysis using the finite element method was conducted to calculate stresses and strains under bending and compressive loads. The analytical results were also verified by JIS flat pallet bending and compression tests.

  Abstract
  Wooden pallets account for a large percentage of pallets indispensable for logistics. From the viewpoint of strength and rigidity, pallets made of foreign timber (e.g., American [...]

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• Determination of orthotropic elastic modulus of wood by indentation with none-axisymmetric indenter and FEM simulation

  T. Tsuji, K. Saito

  WCCM2024.

  
  

  Abstract

  The purpose of this study is to estimate the material constants of woods as an anisotropic material, by indentation tests using an ellipsoid indenter. Firstly, uniaxial compression tests are performed to investigate anisotropic modulus. Secondary, indentation tests are conducted to get load-displacement curve by rotating the non-axisymmetric indenter along the indentation axis. Finally, the orthotropic elastic parameters are estimated by comparing the indentation test results and finite element analysis results. The modulus along longitudinal direction, which is given by the present indentation method, are in good agreement with the measured modulus by the compression test. Therefore, it is confirmed that the longitudinal modulus can be measured by using the present method with the non-axisymmetric indenter

  Abstract
  The purpose of this study is to estimate the material constants of woods as an anisotropic material, by indentation tests using an ellipsoid indenter. Firstly, uniaxial compression [...]

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• Constitutive modelling of wood-based materials

  Z. Chen

  WCCM2024.

  
  

  Abstract

  Wood, unlike steel and concrete, is an anisotropic material. Because of its inherent characteristics, the mechanical behaviour of wood depends on the grain direction and the load type. Appropriate material models are the fundamental basis of reliable simulations. The constitutive models incorporated in existing general design software packages are often limited, making the software unsuitable for accurately predicting the mechanical behaviour and failure modes of wood-based materials. In this paper, a comprehensive constitutive model, composed of sub-models for describing the elastic properties, strength criterion, post-peak softening for quasi-brittle failure modes, plastic flow and hardening rule for yielding failure modes, and densification perpendicular to grain, was introduced. Modelling considerations on the effects of temperature, moisture content, and loading time were discussed. Advanced and practical modelling methods and key considerations for wood-based products were introduced, aiming to support practicing engineers and researchers to become better acquainted with modelling and analysing timber structures.

  Abstract
  Wood, unlike steel and concrete, is an anisotropic material. Because of its inherent characteristics, the mechanical behaviour of wood depends on the grain direction and the [...]

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• Assumption bulging frequency of the real scale tank by micro-tremor measurement and the eigenvalue analysis

  S. Hirai, T. Ono, H. Hirano, N. Sato

  WCCM2024.

  
  

  Abstract

  Damage to tanks has been reported every time an earthquake with a seismic intensity of 6 or higher occurs, such as the 2011 Tohoku Pacific Coast Earthquake (Great East Japan Earthquake), the 2016 Kumamoto Earthquake, and the 2022 Fukushima Prefecture Earthquake.[1-5] . The damage assessment revealed that there are two main types of damage that can occur inside the tanks. The first case is damage to the roof and upper sidewalls of the tank, and the second case is damage to the sidewalls and corners, mainly at the bottom of the tanks. The first is caused by the sloshing phenomenon (liquid level motion due to resonance between the natural frequency of the liquid content and the dominant frequency of seismic waves) due to longer-period seismic motion. On the other hand, the second type is caused by the bulging phenomenon[6,7] (coupled vibration between tank wall and liquid content), and is mainly caused by vibration of the tank structure due to short-period seismic motion

  Abstract
  Damage to tanks has been reported every time an earthquake with a seismic intensity of 6 or higher occurs, such as the 2011 Tohoku Pacific Coast Earthquake (Great East Japan [...]

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• Power dissipation modelling in rolling contact

  A. Myśliński, A. Chudzikiewicz

  WCCM2024.

  
  

  Abstract

  This paper is concerned with the modeling of power dissipation due to friction and its relation with wear estimation in wheel–rail contact. In contact models, wear is usually described in terms of the wear depth function. This function modifies the gap between the contacting bodies as well as the shape of the surfaces of the wheel and rail in contact. In this paper, besides the wear depth function, the dissipated energy, rather than the contact stress, is taken into account to evaluate the wear impact on rail or wheel surfaces. The dissipated energy allows us to more precisely evaluate the wear debris amount as well as the depth of wear and its distribution along the contact interface. A two-dimensional rolling contact problem with frictional heat flow is considered. The elasto-plastic deformation of the rail is assumed. This contact problem is governed by a coupled system of mechanical and thermal equations in terms of generalized stresses, displacement and temperature. The finite element method is used to discretize this problem. The generalized Newton method is applied to numerically solve this mechanical subproblem. The dissipated power is evaluated based on the resultant force and slip at a reference point. Numerical results including the distribution of slip velocity, power factor and wear rate are provided and discussed.

  Abstract
  This paper is concerned with the modeling of power dissipation due to friction and its relation with wear estimation in wheel–rail contact. In contact models, wear is usually [...]

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• How does friction affect sliding contact mechanics?

  N. Menga, C. Mueller, G. Carbone, M. Mueser

  WCCM2024.

  
  

  Abstract

  Dealing with semi-infinite solids, interfacial friction is usually neglected, as normal and tangential displacements fields are independent on each other (unless material dissimilarity occurs). However, contacts involving a sufficiently thin layer, do not stick to such a simplified assumption, as thickness related normal/tangential coupling occurs, and surface frictional shear stresses do matter. It is the case, for instance, of classical rotary seals in boundary lubrication regimes, where rough frictional contacts between thin polymeric sealing lips and rotating shafts occur. Also, functional coatings to control the interface (adhesive, frictional, chemical, etc.) behavior, may be very thin and compliant, and usually experience frictional sliding during operation. All the same, these examples indicates that conditions exists where elastic coupling between in plane and out of plane displacements cannot be neglected and must be considered, instead. Here, we present our results on the rough contact mechanics of elastic and viscoelastic thin layers. We assume sliding conditions and friction at the interface, and we investigate the contact problem in the framework of linear (visco)elasticity, by relying on the Green’s functions approach. We show that, due to the friction and coupling, the presence of interfacial friction may lead to a significant increase of the contact area (up to 10%), compared to the frictionless case, which may affect specific functional response of the interface, such as electrical and thermal conductivity. Since the normal gap distribution is also affected by coupling and friction, the leak rate at the interface turns out significantly altered too. Coupling and friction also affect the contact pressure, which presents a certain degree of asymmetry leading (even for purely elastic materials) to an additional interlocking contribution to the tangential force opposing the relative motion at the interface. Therefore, the overall macroscale friction cannot be predicted by summing-up the local friction contributions occurring at microscale as commonly expected; it should instead include an additional coupled-induced term. The surface stress tensor is also affected, as due to friction and coupling very high tensile stresses are localized at the contact trailing edge, which are likely to induce material failure. In conclusion, we show that the common practice to neglect in-plane interactions in contact mechanics may lead to misleading tribological predictions.

  Abstract
  Dealing with semi-infinite solids, interfacial friction is usually neglected, as normal and tangential displacements fields are independent on each other (unless material [...]

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• Hyper-dimensional gap finite elements for the enforcement of interfacial constraints

  B. Giffin

  WCCM2024.

  
  

  Abstract

  In the classical theory of two-body contact, a single shared contact interface is considered between two continuum bodies, and is further discretized as such in the finite element setting. In general, however, the finite element mesh topology of two contacting bodies will be non-conforming at this shared interface, requiring the definition of a preferred or intermediate surface over which integral constraints may be evaluated. The specification of this interface is deemed to be somewhat arbitrary, but in practice the numerical solution of contact problems may exhibit sensitivity to the particular choice of intermediate surface. A further complication concerns the need to establish projective mappings between the discretized finite element surfaces and the chosen intermediate surface, particularly for the sake of evaluating the contact gap function between pairs of points on each of the two bodies. In this work, a new methodology for the enforcement of contact constraints in the context of finite element analyses is proposed. The method entails an alternative representation of contact surface integrals by equivalently integrating over the interstitial – albeit degenerate gap volume between two contacting bodies. An auxiliary indicator field is defined on each body, and is used to represent the degenerate interstitial volume as a non-degenerate hyper-dimensional gap volume. Over this domain, the gradient of the continuously interpolated displacement field with respect to the indicator field yields the oriented displacement gap, which may be used in the formulation of contact inequality constraints. Discretization of the hyper-dimensional gap volume into conforming finite elements is explored, and is observed to offer several advantages over existing contact discretization methods: the proposed method does not require the computation of geometric intersections or projections; it exploits conventional Gaussian quadrature schemes to integrate the hyper-dimensional gap integrals with a sufficient degree of accuracy; and may be naturally and efficiently extended to represent contact between higher-order surfaces. The efficacy of the method is demonstrated on several benchmark problems. Continuing and future work is also discussed, with a focus on intended applications and extensions of the method.

  Abstract
  In the classical theory of two-body contact, a single shared contact interface is considered between two continuum bodies, and is further discretized as such in the finite [...]

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• Development of a Mixed Reality visualization system using a location-based method for the underwater objects

  R. Nakaso, K. Kashiyama, T. Kotoura

  WCCM2024.

  
  

  Abstract

  This paper presents a development of a hybrid Mixed Reality visualization system using location-based and marker-based methods. The Microsoft Hololens 2 is employed for the MR device. In open-sky environment, location-based method was used for the superimposition method. To obtain location information, GNSS (Global Navigation Satellite System) receivers are used, which can obtain highly accurate location information by network RTK positioning at open-sky environment. The system is capable of superimposed 3D models into real space accurately and automatically. Also, by allowing the switch to marker-based method, this system can be applied to non-open-sky environment. The present system is applied to the visualization of underwater objects in order to check the validity and effectiveness.

  Abstract
  This paper presents a development of a hybrid Mixed Reality visualization system using location-based and marker-based methods. The Microsoft Hololens 2 is employed for the [...]

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