Penalty Force for Coupling Materials with Coulomb Friction

Ding, Ounan; Schroeder, Craig

doi:10.1109/tvcg.2019.2891591

Cited by 12 publications

(11 citation statements)

References 35 publications

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“…Unifying fast collision detection and contact force computations, Allard et al [2010] target deformable contact dynamics where deeper penetrations can arise. Recent work [Ding and Schroeder 2020] has integrated penalty-based friction models with optimizationbased time integration. Exact Coulomb friction paired with adaptive node refinement at contact locations is used for accurate cloth simulation [Li et al 2018].…”

Section: Frictional Contact Dynamicsmentioning

confidence: 99%

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et al. 2020

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We present a differentiable dynamics solver that is able to handle frictional contact for rigid and deformable objects within a unified framework. Through a principled mollification of normal and tangential contact forces, our method circumvents the main difficulties inherent to the non-smooth nature of frictional contact. We combine this new contact model with fully-implicit time integration to obtain a robust and efficient dynamics solver that is analytically differentiable. In conjunction with adjoint sensitivity analysis, our formulation enables gradient-based optimization with adaptive trade-offs between simulation accuracy and smoothness of objective function landscapes. We thoroughly analyse our approach on a set of simulation examples involving rigid bodies, visco-elastic materials, and coupled multi-body systems. We furthermore showcase applications of our differentiable simulator to parameter estimation for deformable objects, motion planning for robotic manipulation, trajectory optimization for compliant walking robots, as well as efficient self-supervised learning of control policies.

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Section: Frictional Contact Dynamicsmentioning

confidence: 99%

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“…To account for this requirement an implementation of the model proposed in Ding and Schroeder [30] was chosen. Their approach of a penalty contact is compatible with the utilized explicit scheme and allows for a straight forward implementation.…”

Section: Mpm Contact Against Rigid Surfacesmentioning

confidence: 99%

“…Only single surfaces are considered in this contribution as contact partners. For a detailed insight into the algorithm, we refer to the work of Ding and Schroeder [30], while we give a brief overview of the strategy in to following, respectively.…”

Section: Mpm Contact Against Rigid Surfacesmentioning

confidence: 99%

Modeling of the Split-Hopkinson-Pressure-Bar experiment with the explicit material point method

Niekamp

Bergmann²,

Pöhl

et al. 2021

Comp. Part. Mech.

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The material point method (MPM) represents an alternative discretization method for numerical simulations. It aims to combine the benefits of a Lagrangian representation of bodies and an Eulerian numerical solution approach. Therefore, especially at high material deformations the method is not prone to mesh distortions such as the finite element method (FEM). For this reason, the MPM is used to a great extent for modeling granular materials as in geo-mechanics. However, high deformations occur in many industrial processes on metallic materials. The Split-Hopkinson-Pressure-Bar (SHPB) experiment is used to characterize material properties at high deformation rates. Although widely used, this experiment is not yet standardized and shows a variety of sensitivities, e.g. to friction. Inter alia for this reason, simulations are conducted with the experiment to allow for a better evaluation of the measured data. The purpose of this work from an engineering point of view is to analyze the performance of the MPM on an SHPB experiment. In order to validate the experimental results for the material characterization under dynamic loading conditions we introduce frictional contact. We use arbitrary tri-linear brick domains in a 3D CPDI1 scheme, instead of originally used parallelepipeds. This allows for a more flexible geometry approximation using standard meshes. The results of the method are analyzed with respect to discretization sensitivity and discussed in the context of the experimental results for a 42CrMo4 steel. We were able to show that the method is capable to reproduce the SHPB experiment. Additionally the method shows convergency in the results with finer discretizations. Thus, the MPM has underlined its importance as an alternative simulation technique for problems with high deformation.

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“…One approach is to simply lag the plasticity [SSC*13, GPH*18], but this can significantly alter the physical behavior of some models. Alternatively, the plasticity can be included directly within a Newton solver, which produces asymmetrical systems that are generally difficult to solve [KGP*16, DS19], though [TGK*17] has suggested a compromise between the options. Alternative formulations can also avoid the problem [DBD16].…”

Section: Related Workmentioning

confidence: 99%

“…We use it when colliding with objects that are not the domain boundary. We note that other collision treatments also exist, such as an extension for cutting [HFG*18], a penalty collision treatment for implicit integration [DS19], and a special treatment for sand [DBD16]. For domain boundaries, reflection boundary conditions for MPM simulation of fluids were introduced in [DSS19], and give the basis for our reflection boundary conditions.…”

Section: Related Workmentioning

confidence: 99%

Effective time step restrictions for explicit MPM simulation

Sun

Shinar

Schroeder

2020

Computer Graphics Forum

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Time steps for explicit MPM simulation in computer graphics are often selected by trial and error due to the challenges in automatically selecting stable time step sizes. Our time integration scheme uses time step restrictions that take into account forces, collisions, and even grid‐to‐particle transfers calculated near the end of the time step. We propose a novel set of time step restrictions that allow a time step to be selected that is stable, efficient to compute, and not too far from optimal. We derive the general solution for the sound speed in nonlinear isotropic hyperelastic materials, which we use to enforce the classical CFL time step restriction. We identify a single‐particle instability in explicit MPM integration and propose a corresponding time step restriction in the fluid case. We also propose a reflection‐based boundary condition for domain walls that supports separation and accurate Coulomb friction while preventing particles from penetrating the domain walls.

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Penalty Force for Coupling Materials with Coulomb Friction

Cited by 12 publications

References 35 publications

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Modeling of the Split-Hopkinson-Pressure-Bar experiment with the explicit material point method

Effective time step restrictions for explicit MPM simulation

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