Mesoscale Numerical Simulation On Mechanical Properties And Damage Of Energetic Materials

Energetic materials are the key materials for the suppression of polymer bonded explosives,and their mechanical properties and damage have important effects on the design,preparation,initiation and safety of explosives.There are various mechanical behaviors such as deformation,temperature rise and stress change during the pressing process of energetic materials,however,these dynamic mechanical behaviors are the source of the explosion.Owing to that the suppression of the explosive is carried out in a closed container,we can only obtain the final result through experiments,and the intermediate process is difficult to be observed.Therefore,it is an important method to simulate the process of energetic materials with numerical simulation to study the mechanical properties of energetic materials.The general numerical simulation methods are Lagrange and Euler.When we solve the problem of large deformation of material,the severe distortion and distortion of the background grid element in Lagrange method will lead to the decrease of calculation precision,And Euler method cannot clearly express the material boundary configuration.Due to the wide distribution of particle size,the particle size distribution is between sub-micron and millimeter,which belongs to the mesoscale in space.Thus,it is of great theoretical and practical value to calculate the mechanical properties of energetic materials with mesoscale model.The material point method divides materials into a number of discrete particles during the calculation,these particles carry all of information(displacement,speed,stress and so on).The motion of the particle on the background grid represents the deformation of the material and avoids the problem of mesh distortion.The material point method is very suitable for dealing with large deformation problems.So we adopt the material point method to simulate the deformation,temperature,stress and damage in the process of compaction on mesoscale.Some interesting phenomena have been found in the study: it is find that the particles is rearrange in the compaction process,and the voids between the particles is decreasing and moved to both sides in the process of mutual extrusion;The temperature of large particles in surface and micro particles is significantly higher than other parts,and the temperature in the gap is relatively low,and the overall temperature of the system increases gradually.The stress in the system increases gradually with the pressing and forms the stress gradient,and the stress spreads from top to bottom in mesh shape.Compare the density of the simulated explosive with the experimental density provided by the project coordinator,the results show that,in the case of a given pressure,the density obtained from the simulation is less than 5% with the experimental results,which verifies the validity of the simulation method.Finally,we study the effect of cracks in the particles on the compaction process,the simulation results show that the cracks in the particles tend to be crushed,and the internal stress produced by pressing the defective particles is smaller than that of the intact particles.This study can provide theoretical guidance for the process design of the explosive.