基于简化的质点-弹簧模型织物变形仿真研究

研究织物变形特定性优化问题,针对织物形状动态改变提出了一种基于物理模型方法仿真织物变形,对织物采用质点-弹簧模型进行建模,解决织物变形在实际中的真实特用性,对质点-弹簧模型作了简化,即在模型中减少一部分剪切弹簧。在求解模型中,采用简单的显式欧拉积分法来求解织物的变形方程。同时对织物与环境之间进行了碰撞检测与处理。仿真结果表明,设计的模型稳定性和实时性好,为实际实现提供了参考。

基于改进弹簧振子模型的软组织形变仿真

研究虚拟手术中软组织形变的特定性优化问题。传统弹簧振子模型由于采用线弹力方程及显示欧拉积分法求解,导致的真实性低、计算复杂、实时性差的问题。为解决形变动特性问题,提出一种改进弹簧振子模型的形变方法,采用四面体网格弹簧振子模型进行建模,并通过定义质点间弹簧的非线性弹力方程以及作用于质点的体积力方程,来减弱超弹性现象的发生,提高真实性。模型求解时,采用一种改进显式欧拉积分的动态局部算法来求解形变方程。实验结果表明,所提算法提高了形变仿真的真实性、实时性和稳定性,可为软组织形变动态仿真系统的设计提供参考。

An explicit integration scheme for hypo-elastic viscoplastic crystal plasticity

An explicit integration scheme for rate-dependent crystal plasticity （CP） was developed. Additive decomposition of the velocity gradient tensor into lattice and plastic parts is adopted for describing the kinematics; the Cauchy stress is calculated by using a hypo-elastic formulation, applying the Jaumann stress rate. This CP scheme has been implemented into a commercial finite element code （CPFEM）. Uniaxial compression and roiling processes were simulated. The results show good accuracy and reliability of the integration scheme. The results were compared with simulations using one hyper-elastic CPFEM implementation which involves multiplicative decomposition of the deformation gradient tensor. It is found that the hypo-elastic implementation is only slightly faster and has a similar accuracy as the hyper-elastic formulation.

A Finite Volume Backward Euler Difference Method for Nonlinear Parabolic Integral-differential Equation

The Finite volume backward Euler difference method is established to discuss two-dimensional parabolic integro-differential equations.These results are new for finite volume element methods for parabolic integro-differential equations.