Parallel Computation Of Contact-Impact Problems With FEM And Its Engineering Application

With large deformation, the behavior of contact-impact computation presents geometric non-linearity, material non-linearity and boundary condition non-linearity. Because of its complexity, the large-scale contact-impact computing is very time-consuming. It's difficult to obtain satisfactory accuracy without the use of supper-computers.In order to gain high efficiency and good accuracy for the numerical simulation of large-scale contact-impact problems under cluster computer environment, the TUL formulation is presented. In this formulation, the variables refer to the configuration at several time-step ago, neither the initial configuration at time 0, nor the known configuration at last time-step. It has the advantages of both TL and UL formulation. By using the TUL formulation, the precision of the numerical result is almost the same as the UL formulation and the efficiency is almost the same as the TL formulation for the explicit dynamic analysis based supper-parametric shell elements.To solve the contact-searching problem that is the most time-consuming process in the 3D large-scale contact-impact simulation, a new global searching algorithm is proposed. In terms of the linked-list, this algorithm solves the problem of sorting and searching contacts in three dimensions by transforming it to a retrieving process from two one-dimensional arrays, and binary searching is no longer required. Using this algorithm, the cost of contact searching is reduced to the order of O(n) while the traditional ones cost O(Nlog₂N). Moreover, this algorithm is reliable and efficient, and can handle contact systems with arbitrary mesh layouts.To improve the accuracy of contact search, a new FFS searching algorithm is proposed in this paper for the local contact search. The algorithm is based on a special free-formed-surface. It makes the normal vector continued among the neighbor element segments. Not only the dead-zone problem is overcome, but also the accuracy of contact searching and contact-force computing is improved. It is not necessary to distinguish the contact status of node-to-segment, node-to-edge, node-to-node in this algorithm. Thus the algorithm is suitable for parallel environments.