Fully implicit frictional dynamics with soft constraints

Dynamics simulation with frictional contacts is important for a wide range of applications, from cloth simulation to object manipulation. Recent methods using smoothed friction forces have enabled robust and differentiable simulation of elastodynamics with friction. However, the resulting frictional behaviors can be qualitatively inaccurate and may not converge to analytic solutions. Here we propose an alternative, fully implicit, formulation for simulating elastodynamics subject to frictional contacts with realistic friction behavior. Furthermore, we demonstrate how higher-order time integration can be used in our method, as well as in incremental potential methods. We develop an inexact Newton method with forward-mode automatic differentiation that simplifies the implementation and improves performance. Finally, we show how our method can be extended to respond to volume changes using a unified penalty function derived from first principles and capable of emulating compressible as well as nearly incompressible media

Large steps in cloth simulation

The bottle-neck in most cloth simulation systems is that time steps must be small to avoid numerical instability. This paper describes a cloth simulation system that can stably take large time steps. The simulation system couples a new technique for enforcing constraints on individual cloth particles with an implicit integration method. The simulator models cloth as a triangular mesh, with internal cloth forces derived using a simple continuum formulation that supports modeling operations such as local anisotropic stretch or compression; a unified treatment of damping forces is included as well. The implicit integration method generates a large, unbanded sparse linear system at each time step which is solved using a modified conjugate gradient method that simultaneously enforces particles ’ constraints. The constraints are always maintained exactly, independent of the number of conjugate gradient iterations, which is typically small. The resulting simulation system is significantly faster than previous accounts of cloth simulation systems in the literature. Keywords—Cloth, simulation, constraints, implicit integration, physically-based modeling.

Identification and control of vibration transmission in a professional washing machine.

openDottorato di ricerca in Ingegneria industriale e dell'informazioneembargoed_20210923Battistella, Nicol

Realistic Cloth Animation

In this paper we present a model for the realistic simulation of the mechanical behavior of cloth based on the Finite Elements Method. The use of this method in a material with the elastic properties of cloth has some problems of convergence to which we propose a solution in this work

Prediction of service life of polymeric sealant compositions for fuel tanks in aerospace structures from measurements of viscoelastic properties Annual report

Prediction of service life of polymeric sealers for fuel tanks from viscoelastic measurement