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A Combined Particle-Element Method for High-Velocity Impact Computations

机译：一种用于高速冲击计算的组合粒子元件方法

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This article presents a Combined Particle-Element Method (CPEM) for high-velocity impact computations. It includes a description of the numerical algorithms, and example computations. For this new approach the initial mesh is input as solid finite elements, and then it is put into a meshless-particle structure in the preprocessor. The integration points of the original elements are transformed into massless stress points, and the nodes from the original elements carry the mass and accept forces from the stresses. When the equivalent plastic strain in a stress point is less than a user-specified value (ε_(crit)) a finite-element algorithm (formulated within a particle structure) is used to update the strain rates and strains at the stress point, and to compute forces for the (fixed connectivity) particle nodes. When the equivalent plastic strain in a stress point exceeds ε_(crit) the strain rates are determined from the surrounding neighbor nodes (obtained from a search routine) with a Moving Least Squares (MLS) formulation, and the nodal forces are determined from a weak-form formulation. With this approach there is a simple transition between the element and particle algorithms. The advantages are that the lower-strained particles (stress points) are computed with a fast and accurate finite-element formulation, and the higher-strained particles are computed with a meshless-particle formulation that can handle severe distortions. Furthermore, the meshless-particle algorithm (with MLS strain rates and weak-form forces) is consistent and does not exhibit tensile instabilities. It is also well-suited for conversion of finite elements into variable-connectivity meshless particles because it does not require deletion of elements and addition of particles, as required with the existing conversion algorithms that use the Generalized Particle Algorithm (GPA). Instead it is simply a branch point based on equivalent plastic strain. The basic approach can also be used for the element algorithm only or the particle algorithm only.
机译：本文提出了一种合成粒子元法（咨询处）的高速冲击计算。它包括的数值算法的说明，示例计算。对于这种新方法的初始网格被输入作为固体有限元素，然后将其放入预处理器中的一个无网格颗粒结构。原始的元素的融合点转化为无质量的受力点，并从原来的元素节点进行质量和接受来自应力力量。当在应力点的等效塑性应变小于被用来更新在应力点处的应变率和应变一个用户指定的值（ε_（击））有限元算法（粒子结构内配制），并来计算力的（固定连接）粒子的节点。当在应力点的等效塑性应变超过ε_（击）的应变速率从周围的相邻节点（从搜索程序中获得）与移动最小二乘（MLS）配方确定，并且节点力从弱确定 - 形式的配方。采用这种方法有在元件和颗粒的算法之间的简单转换。的优点是在应变较低的颗粒（应力点）被计算同一个快速而准确的有限元制剂，具有较高的应变颗粒计算与无网格颗粒制剂，其能够处理严重失真。此外，无网格粒子对算法（MLS应变率和弱式力）是一致的，并且不表现出拉伸不稳定。它也非常适用于有限元为可变的连通无网格粒子的转换，因为它不需要的元素和添加的颗粒的缺失，如与使用广义粒子算法（GPA）的现有的转换算法所需。相反，它是简单地基于等效塑性应变的分支点。基本的方法也可以用于只元件算法或仅所述颗粒的算法。

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