爆炸载荷下脆性颗粒体系破碎特性的数值研究

Numerical study on particle breakage characteristics under blast loading

试验发现,以球形TNT为中心爆源,球形玻璃珠构成的颗粒和球壳中发生破碎的颗粒体积分数随当量比(颗粒球壳的质量与TNT炸药的质量比)的增加呈现指数衰减规律。采用有限元与离散元耦合的连续非连续数值方法,揭示了中心炸药起爆后颗粒环壳内爆炸波的传播衰减和在环壳外界面反射后的稀疏卸载过程。由于爆炸波的短脉冲特性,颗粒内部应力场始终处于应力非均衡状态,采用应力均衡状态下颗粒破碎强度的Weibull分布会得到远高于试验测得的破碎颗粒体积分数。因此采用破坏波传播特征时间内的平均诱导应力而非瞬时诱导应力作为颗粒破碎强度的应力指标,并通过试验结果确定破坏波传播特征时间。考虑了应力传播的非均匀性对于颗粒破碎的影响,得到了平均诱导应力峰值的概率分布随比例距离的变化规律,结合修正后的颗粒破碎强度Weibull分布建立了破碎颗粒体积分数随比例距离的变化模型。

Experiments indicated that with spherical TNT as the central explosion source,the volume fraction of the particles composed of spherical glass beads and the broken particles in the spherical shell showed an exponential decay law with the increase of the M/C(the mass ratio of the spherical shell of the particle to the mass of the TNT).Using the DEM coupled with FEM,this paper reveals the propagation attenuation of the explosion wave in the particle annular shell after the central explosive is detonated and the sparse unloading process after reflection at the outer interface of the annular shell.Due to the short pulse characteristics of the blast wave,the internal stress field of the particles is always in a state of stress non-equilibrium,and the Weibull distribution of the particle crushing strength in the stress-equilibrium state will be much higher than the volume fraction of the broken particles measured by the test.Therefore,in this paper,the average induced stress rather than the instantaneous induced stress in the characteristic time of the breaking wave propagation is used as the stress index of the particle crushing strength,and the characteristic time of the breaking wave propagation is determined by the test results.In this paper,the influence of the non-uniformity of stress propagation on particle breakage is considered,and the variation law of the probability distribution of the mean induced stress peak value with the proportional distance is obtained.