Anisotropic Body Under Impact Loading Stress Wave Propagation, Damage And Destruction,

The substance of problems in simulating the damage and failure processes of material under dynamic loading, such as impact and penetration, is that the mechanics model of material transfers from continuum to noncontinuum. Among the numerical proceedings, finite element method, finite difference method, which are based on the continuum mechanics theory is suitable to predict the damage or failure area, but incapable of simulating the whole process of the damage in the material or the structures. Discrete Element Method (DEM) is a powerful method proposed to deal with the non-continuum mechanics problem. The basic idea is put forward by Cundall et. al. in the 70's. Now several researchers have tried to extent it to simulate impact dynamics problems of continuum and the process from continuum to noncontinuum under impact loading, especially the problems in the dynamic failure of concrete media. It shows great vitality in these fields. But comparing with the traditional numerical methods, such as finite element method, the results of calculation are too rough to farther expand the OEM's application in dynamic mechanics.In this paper, a numerical algorithm based on the discrete element method is proposed for calculating the dynamic problems in orthotropic solids under impact loading. Base on the basic principle of continuum mechanics, 2-D contact type model are derived using circular plate element. Mohr-Coulomb type failure criteria and failure coefficients related with stress ratio are used in this model to simulate the failure process. The wave propagation in an orthotropic plane under impact loadings was numerically simulated, by using this algorithm. Comparing its results with those by LS-D YNA, the accuracy of this algorithm was presented. Moreover the failure process in concrete due to impact loading and the failure process of a steel bullet penetrating a concrete circular plane was demonstrated, which presented the dynamic transitional process from continuum to non-continuum. Several different fundamental damage forms simulated by using this algorithm were discussed, comparing with the results from experiments.The algorithm is also extended to three dimensions, and 3-D contact type model are derived using ball element. The dynamic failure process of concrete block due to impact loading is studied using this model.Finally the process of blasting compaction is numerical simulated by the DEM. It is proved to be a good tool to study the mechanic problem in this process and shows great potential in engineering applications.The examples above sufficiently prove that the DEM is a powerful tool of simulating the dynamic problems from continuum to noncontinuum. This algorithm shows widelyapplicability and good prospect. The 2-D and 3-D DEM codes are developed using C-H-programming language based on the idea of OOA (Object Oriented Analysis). A set of preprocess and postprocess code for the DEM is also developed. The two codes in one become an integrative discrete element analysis system: S-DEM (Super-Discrete Element Method). All the examples above are calculated and dynamically displayed by this analysis system.