Numerical Simulation Of OFHC Copper Pore Collapse Process Under Impact Load Based On Material Point Method

The problem of pore collapse is a joint research topic in the fields of explosive compaction,explosive initiation,and material damage.Study on the problem of pore collapse under impact load is of great significance for the preparation of high-quality dense materials.The process of pore collapse is an instantaneous small-scale process with high strain rate,strong coupling and strong nonlinearity,which is difficult to conduct experimental research.As a new numerical simulation method,the material point method combines the advantages of the Lagrangian method and the Euler method,effectively avoiding the grid distortion of the finite element method and the general Mesh-less method.It has great potential in studying large deformation problems.In this paper,the numerical simulation of the pore collapse process under impact load is carried out based on the material point method to explore the pore collapse law of different impact loads,pore shapes and numbers on the pore collapse process.The mechanism of improving the compaction forming performance of materials under high impact load is discussed.The weighted residual method is used to derive the weak form of the Lagrangian scheme in the governing equation and momentum equation,and the specific process of the explicit solution by the matter point method is given.The rigid-flexible contact algorithm is introduced,and the FORTRAN language is used to write a material point method program for simulating pore collapse under impact load.Through two examples of single cylindrical pore collapse and hemispherical pore collapse,the self-written material point method program was used to simulate the pore collapse process under a certain impact velocity,and the simulation results were compared with the pore collapse results in the existing literature.The comparison verifies the validity and reliability of the self-programming.Based on the material point method,the numerical simulation of pore collapse process under impact load is carried out.The collapsing law of pores with different impact loads,pore shapes(spherical pore,regular triangular prism-shaped pore or cylindrical pore)and numbers(single-pore,double-pore,treble-pore or multi-pore)on the pore collapse process was explored.Under the same impact load,the jet velocity of spherical pore is the largest followed by the regular triangular pore,the cylindrical pore is the smallest.The penetration depth law is also the same.For the collapse of a single pore,when the impact load is higher than 300 m/s,three types of pores will have jets.The single regular triangular prism pores will produce peculiar double jets.For the collapse of two pores,the law of collapse of the upper pores is similar to that of single pores,and the collapse of the lower pores is slower.For the collapse of three or more rows of pores,oblique jets will be generated when the impact load is higher than 300 m/s.At this time,the pores of the same row of pores close to the central axis are closed first,and the parts of the pores near the central axis are closed first.Strong jet penetration will make the temperature in the pores exceed the melting point of OFHC copper to obtain more tight boundaries when the impact load is high.The greater the impact load,the greater the jet velocity and penetration depth.So the properties of OFHC copper spherical porous materials can be improved by compaction under high impact load.The research in this paper provides a novel idea for the numerical simulation of pore collapse process under impact load,and also plays a guiding role in the actual production of impact compaction of materials.