Documents published in Scipedia

• Modeling the Effective Inelastic Behavior of Multi-Wire Cables Under Mechanical Load Using Finite Elements

  M. Hawwash, V. Dörlich, J. Linn, R. Keller, R. Müller

  eccomas2022.

  
  

  Abstract

  In the development and manufacturing process of modern cars, cables and hoses are important system components. In automotive industry, virtual assembly planning and digital validation of system layouts require a fast and physically correct simulation of the mechanical behavior of cables and hoses. The mechanical response of cable systems and hoses under load is typically non-linear and inelastic due to their multi-component structure. However, those effects can hardly be observed and investigated separately in experiments. Thus, the authors recently presented simplified cable models using the commercial finite element tool ANSYS which take wire interactions into account. As cables in automotive applications are often subject to large deformations, finite beam elements with quadratic shape functions were used to discretize the single helix wires. The comparison of simulation results obtained for helix wire strands under bending with analytical results based on wire rope theory showed good agreement for the case of frictionless interactions. Furthermore, the modeling approach serves as a versatile toolbox for the investigation of material and structural inelastic effects which commonly occur when cables are deformed. A significant influence of structural parameters, such as the helix angle of the wires or the choice of friction model parameters, on the mechanical response could be found. In this work, this modeling approach is applied to the simulation of multi-wire strands consisting of parallel elastic wires under bending and torsion. The results of these mesoscopic simulations will be compared to experimental results.

  Abstract
  In the development and manufacturing process of modern cars, cables and hoses are important system components. In automotive industry, virtual assembly planning and digital [...]

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• Estimating stress fluctuations in polycrystals with an improved maximum entropy method

  M. Krause, T. Böhlke

  eccomas2022.

  
  

  Abstract

  The prediction of local field statistics from effective properties is an open problem in the field of micromechanics. Partial information on the local field statistics is accessible from homogenization assumptions. In particular, exact phase-wise second moments of stresses can be calculated analytically from the effective strain energy density. In recent years, full-field calculations have become efficient enough to sample large ensembles of microstructures in the plastic regime (e.g. Gehrig et. al [4]). In the present work, the maximum entropy method known from statistical thermodynamics is used to estimate first and second moments of local stresses from known eigenstrain distributions. The simple and refined formulations of the maximum entropy method proposed by Kreher and Pompe [9] are considered. While the simple method yields satisfactory results for a large amount of material classes (cf. Krause and Böhlke [7]), we prove that it does not respect the linearity of the eigenstrain problem. We further show that neither method corresponds to the exact second moments of stresses known from the effective strain energy density. By incorporating additional information, we find an improved maximum entropy method. As an example, we analyze stress fluctuations in polycristalline titanium.For the exact analytical solution and the maximum entropy methods, we use the singular approximation and the Hashin-Shtrikman bounds. For comparison, we numerically approximate full-field statistics using an FFT approach. In all methods, the stress fluctuations caused by the anisotropy of the single crystal strongly influence the elastic-plastic transition.

  Abstract
  The prediction of local field statistics from effective properties is an open problem in the field of micromechanics. Partial information on the local field statistics is [...]

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• Quantifying errors due to the Hertzian contact model in multi-sphere Discrete Element Modelling simulations

  S. Constandinou, J. Blackford, K. Hanley

  eccomas2022.

  
  

  Abstract

  In Discrete Element Modelling (DEM), non-spherical particles are often emulated using clusters of rigidly connected spheres that can be either overlapping or not. Within this multi-spherical approach, two sources of error directly affecting the normal contact forces present can be identified. One is due to the difference between the true particle shape and the multispherical approximation; the other arises from the contact model used in the DEM simulations. The potential for inaccuracy in multi-sphere DEM simulations is well known. However, for a DEM simulator it remains unclear what error might be expected when multi-sphere particles are adopted. This contribution focuses on the role of the contact model as a source of error for the special case of two-sphere particles. Considering a single multi-spherical rod consisting of two identical spheres and quasi-statically compressing it until a total of 5% strain has been applied, the force response obtained through Finite Element Analysis (FEA) was compared against the Hertzian contact model. The process was repeated for spheres with varying degrees of overlap, ranging from 0 to 100%, and the relative errors of the FEA models against the Hertzian contact model were calculated. Up to a 60% sphere overlap, Hertz underpredicts the normal contact forces beyond 0.5% strain, where the disparity between the FEA model and Hertz forces is increasing monotonically with strain. However, beyond an overlap of 70%, Hertz overpredicts the normal contact forces with the sphere overlap being the main driver of this deviation. Future research will involve comparing these errors with the `shape' source of error by compressing perfect spherocylinders, considering rods composed of more spheres, and investigating how the error is affected by the relative orientation of two contacting particles.

  Abstract
  In Discrete Element Modelling (DEM), non-spherical particles are often emulated using clusters of rigidly connected spheres that can be either overlapping or not. Within this [...]

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• Simulating Nonlinear Elastic Behaviour of Cables Using an Iterative Method

  T. Zhao, F. Schneider-Jung, J. Linn, R. Müller

  eccomas2022.

  
  

  Abstract

  This contribution introduces a novel approach to simulate the nonlinear elastic bending behaviour of cables. Bending tests on real cables with complex structures clearly show the existence of nonlinear constitutive bending behaviour. In our current framework, only constant effective stiffness parameters are used. In order to enable nonlinear bending behaviour within the current framework, we propose an iterative method where, at each step, constant stiffness parameters are used and are updated according to the current cable state. The presented method is demonstrated by means of numerical experiments. Moreover, the inverse problem, i.e. the determination of state-dependent bending stiffness characteristic, is considered.

  Abstract
  This contribution introduces a novel approach to simulate the nonlinear elastic bending behaviour of cables. Bending tests on real cables with complex structures clearly show [...]

  • 47
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• Director-based IGA beam elements for sliding contact problems

  P. Wasmer, P. Betsch

  eccomas2022.

  
  

  Abstract

  The geometrically exact beam theory is one of the most prominent non-linear beam models. It can be used to simulate aerial runways or pantograph-catenaries, where a sliding contact condition between two or more beams is used. A smooth discretization of at least C1continuity is needed to not introduce any unphysical kinks. This can be achieved using the isogeometric analysis, which we apply to a director-based formulation of the geometrically exact beam. For a stable time integration scheme we use an energy-momentum conserving scheme. Using the notion of the discrete gradient, an energy-momentum conserving algorithm is constructed, including the case of sliding contact between beams.

  Abstract
  The geometrically exact beam theory is one of the most prominent non-linear beam models. It can be used to simulate aerial runways or pantograph-catenaries, where a sliding [...]

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• Nonlinear seismic analysis of reinforced concrete structures using POD reduced order method

  N. Ayoub, W. Larbi, J. Deü

  eccomas2022.

  
  

  Abstract

  This paper presents an extension of the Proper Orthogonal Decomposition method (POD) to nonlinear dynamic analysis of reinforced concrete multistory frame structure where the material nonlinearity is modeled by the multi-fiber section. To test the effectiveness of this approach, we first perform a nonlinear dynamic analysis under a seismic excitation using a direct implicit time integration scheme. Then, based on structural response observations, POD modes were extracted and used to reduce the structural system subjected to different earthquakes. A comparison was made between full model and reduced model analysis in order to assess the effectiveness of this technique.

  Abstract
  This paper presents an extension of the Proper Orthogonal Decomposition method (POD) to nonlinear dynamic analysis of reinforced concrete multistory frame structure where [...]

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• Simulation of non-round particles in tribological three-body systems

  R. Bilz, K. de Payrebrune

  eccomas2022.

  
  

  Abstract

  Particles between the contact interfaces of two components in relative motion are present in many technical applications and can strongly influence the system behavior. In this context, the focus is often on the investigation of wear and damage. In addition to such undesirable phenomena, however, there is also the targeted use of hard particles, for example in the lapping process. In lapping, hard particles are intentionally inserted between a lapping disc and the workpiece surface to be processed in order to cause material removal with the help of the particles and to improve the morphology of the workpiece surface for certain applications. Many simulations of such tribological systems are based on the assumption of spherical particles. However, both, size and shape of the particles have an essential effect on the system behavior. Here, an approach is presented in which hard, arbitrarily shaped particles in tribological contacts can be studied a priori using the finite element method by performing indentation simulations for various particle orientations. Based on the results, an orientation-dependent particle model is created for simulations of the overall system, which includes particles in narrow gaps. This modular design allows direct control in the implementation of phenomenological effects and new insights into the behavior of such systems, as well as the estimation of the resulting surface topography.

  Abstract
  Particles between the contact interfaces of two components in relative motion are present in many technical applications and can strongly influence the system behavior. In [...]

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• Molecular dynamics investigation of the effect of interlayer cavities of the structure of calcium silicate hydrate at the atomistic scale

  D. Tavakoli, M. Hajmohammadian Baghban

  eccomas2022.

  
  

  Abstract

  Calcium silicate hydrate (CSH) gel, as the most important component of hydration products, has the most significant effect on the properties of hardened cement paste. One of the most critical factors affecting the mechanical properties of CSH is the interlayer cavities in the gel. In this study, the effect of these cavities on Young's modulus of CSH has been investigated. For this purpose, first, the atomic structure of CSH is created, and then interlayer cavities with different dimensions are created inside the structure. For modelling, first, a super cell with dimensions of 3 × 6 × 1 times the unit cell of Tobermorite is prepared, and then each of these layers are placed on both sides of the new cell, and a space is created between these two layers. This distance is basically the cavity between the layers.

  Abstract
  Calcium silicate hydrate (CSH) gel, as the most important component of hydration products, has the most significant effect on the properties of hardened cement paste. One [...]

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• Simulation and experimental investigation of tire tread block wear in three-body contact

  D. Nguyen, S. Kahms

  eccomas2022.

  
  

  Abstract

  On gravel roads, tires are not in direct contact with the surface. Particles of e.g. sand or stone contact directly with the tire and cause the tire to wear. During the sliding process, an interaction between particles and the tire occurs. On simplified conditions investigation of the movement of particles, friction and wear of a tire tread sample are done experimentally for different settings. Additionally, a finite element simulation is built up to simulate the wear of the tire tread sample under varying conditions. In this paper results from the experimental and numerical investigation of the wear of the tire tread sample are shown.

  Abstract
  On gravel roads, tires are not in direct contact with the surface. Particles of e.g. sand or stone contact directly with the tire and cause the tire to wear. During the sliding [...]

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• Microscale numerical simulation of yarn tensile behavior using a high-fidelity geometrical fiber model extracted from micro-CT imaging

  A. Bral, L. Daelemans, J. Degroote

  eccomas2022.

  
  

  Abstract

  Air jet weaving, where the weft yarn is transported through the machine using air as propelling medium, is a popular weaving method due to its superior productivity, however at the cost of a high energy demand. The interactions between the weft yarn and the air jets are complex and not yet fully understood. Moreover, state-of-the-art techniques to simulate these interactions, are far from mature since the yarn is often simplified as a smooth and solid cylinder. Therefore, a novel multi-scale and multi-physics approach is proposed to simulate the interaction between weft yarns and air jets. Starting from microcomputed tomography (µCT) scans of a yarn used in air jet weaving, a high-fidelity microscale geometrical model is constructed, representing the yarn by its fibers. This geometrical model is used as input for microstructural simulations and will be used for flow simulations on microscale, where the aim is to extract local coefficients and as such characterize the yarn. These coefficients are then used as input for computationally cheap macroscale models, where the yarn is represented by its centerline containing the microscale properties. In a final stage, the macroscale structural and flow models will be coupled as to obtain a full FSI simulation of a weft insertion in an air jet loom. Current paper highlights the microscale geometry extraction of a fine wool fiber yarn of 28.8 tex. Consecutively, a computational framework is proposed to simulate the tensile behavior of this yarn, using the previously obtained microscale geometrical model. The resulting stress-strain curve of the yarn is compared to experiments and shows good correspondence.

  Abstract
  Air jet weaving, where the weft yarn is transported through the machine using air as propelling medium, is a popular weaving method due to its superior productivity, however [...]

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