Research On The Law Of Stress Wave Propagation In Silica Sand Particles

Due to the characteristics of porous particles,high compressibility and significant attenuation of stress wave propagation under impact loading,they are widely used in protective engineering to resist military strikes such as missiles and explosions.Therefore,research on the propagation law of stress waves in Silica sand,especially the attenuation characteristics of stress waves during the propagation process,is of great significance to the construction of actual protection engineering.In this paper,a discrete particle model is established based on the discrete element method,and the propagation of stress waves in the discrete particles is studied.The accuracy of the numerical simulation is verified through experiments.Finally,a preliminary discussion on the practical engineering application of loose particles.It is found through numerical simulations:(1)Under shock loading,the propagation of stress waves in Silica sand decays exponentially.The attenuation factor β can be used to describe the degree of attenuation of stress waves.The larger the value of β,the more the stress waves in the granular body.The more severe the attenuation in the particles;In addition,the stress wave will be accompanied by particle breakage during the propagation process.Different degrees of particle breakage will affect the attenuation of the stress wave in the loose particles.The greater the degree of particle breakage,the more obvious the attenuation of the stress wave during the propagation process;(2)The attenuation of stress waves has a significant rate dependence.The essence is that different loading speeds bring different degrees of particle crushing.The greater the loading speed,the greater the degree of particle crushing,resulting in greater attenuation of stress waves at higher speeds.And the velocity itself has no effect on the attenuation of the stress wave;(3)The stress wave will also be accompanied by the change of pulse width during the propagation process.The attenuation of the stress wave decreases with the increase of the loaded pulse width.This is because the scattered particles have a significant dispersion effect on high-frequency waves and will greatly weaken the short pulse width.Peak stress of the high frequency wave,but the impact on the low frequency wave of the long pulse width is relatively small;(4)The confining pressure effect of the side wall can affect the axial propagation of the stress wave by affecting the radial contact force of the loose particles.In active confining pressure,the greater confining pressure load,the greater the degree of particle breakage,and the attenuation of the stress wave in the loose particles shows a weakening trend with increasing confining pressure.In passive confining pressure,the propagation law of stress waves in loose particles is affected by the side wall material,and different materials show different propagation characteristics;(5)In numerical simulation,the law of wave propagation can also be analyzed by the relationship of energy.In plate loading,the energy is mainly transformed from boundary energy to particle kinetic energy,particle friction energy,particle strain energy,and damping energy.The larger the loading speed,the larger the boundary energy,and different conversion paths under different boundary energies.It shows different attenuation laws of stress waves.In terms of experiments: static and dynamic mechanical experiments on Silica sand were carried out using MTS hydraulic presses and SHPB pressure rods to obtain the stress-strain curve of Silica sand.It was found that the rate of change of stress from strain was slow to rapid,and the stress value varied with the pores during compression.It is found that the confined compressive constitutive of the dispersed particles is compared with the numerical simulation.It is found that the yield stress of both is about 10 MPa.Based on this,the propagation law of stress waves in Silica sand is explored,and the experimental data are compared with the simulation results: The attenuation trends of the stress waves of the two have a good consistency.It can be seen that it is feasible to conduct the study of the propagation of stress waves in loose particles by the discrete element method.Finally,the discrete element method is used to establish the actual engineering application of the dispersed particles,and the preliminary investigation of the propagation characteristics of the stress wave in the actual engineering application is made,and a certain conclusion is obtained.