Study And Applications Of Material Point Method In Impact Dynamics

Impact dynamics is an important one of research fields in dynamics, involving keyproblem of national defense, aerospace industry and so on. The difficulties of study includeshock wave propagation, elastic-plastic mechanics model, yield criterion, equation of stateand material failure model, etc. It is a strong time-dependent non linear system that acomprehensive dynamics process is analysed and lots of difficulties will arise. In this paper, anew meshfree method is applied to research some key issues in impact dynamics, includinghigh-speed collision of solid material, craters formed by hypervelocity impact, spall fructure,debris clouds and gas shock wave and exploding in air. Compared to experimental results ortheoretical results, it was proved that material point method has a huge advantage in impactdynamics.Specific contents:1. Firstly, both traditional grid-based numerical methods and meshless methods aresummarized with emphasis on the material point method of initiation, development andinnovation. The application of material point method and the challenge are illustrated clearly.2. Introducing the basic equations. The spatial discretization, time discretization, theweighting function, boundary conditions, the stress update format, artificial bulk viscosity,time step size and other key issues are summarized. For three forms of material point method,the standard material point method, the generalized interpolation material point method(GIMP) and convected particle domain interpolation technique are discussed in natrue.3. Material point method is applied to simulate the high-speed, hypervelocity impactcollision. Mie-Grüneisen EOS is used to study the strong shock wave. Johnson-Cookconstitutive model is used to analyse the yield stress in high temperature, high pressure andhigh strain rate state. Some typical failure models are used to study failure damage such asmaximum equivalent plastic, strain failure, maximum tensile stress failure, melt failure, etc.Framework of large deformations Jaumann rate of incremental constitutive integrationalgorithm and both the update algorithm of stress and equation of state, with adiabatictemperature rise effects included are considered. Taking into account all these factors tocalculate the Taylor bar impact problem, the phenomenon of high-speed into the thick target,hypervelocity impact of spallation phenomena, hypervelocity impact forming debris clouds phenomenon. Compared to the available experimental or comparative literature results found,material point method can improve the accuracy and efficiency of simulation of impact.4. For shock wave in the gas, GIMP is shown that the accuracy is improved obviously,and decrease in2D problems. And the concept of generalized adaptive split material pointmethod is presented firstly which can solve the tension instability inherent in the GIMP and isextended to the exploding effect by solid explosive in gas.