裂纹宽度对分步压装装药撞击安全性的影响

针对装药裂纹与装药密度不均匀两个因素耦合作用下分步压装装药撞击安全性缺乏系统研究的问题,利用大型落锤加载装置对具有不同裂纹宽度的分步压装药柱进行了撞击加载试验,并分析了试验前、后药柱内部应力和密度分布状态的变化规律,讨论了裂纹宽度对分步压装装药撞击安全性的影响机制。结果表明:当裂纹宽度小于1.0 mm时,带裂纹分步压装药柱的撞击安全性均优于无裂纹药柱;但当裂纹宽度达到1.5 mm时,其撞击安全性明显降低。这主要是因为在撞击加载条件下,当裂纹未扩展时,裂纹区域的闭合过程能够吸收部分落锤撞击能量,减弱炸药颗粒径向流动趋势,进而降低"热点"形成的几率;而当裂纹发生扩展时,在裂纹扩展区域极易引发"热点"形成,使分步压装药柱的撞击安全性降低。可见,随裂纹宽增大,分步压装装药中裂纹所起的主要作用发生变化,从而导致装药的响应结果不同。

Influence of crack width on collision safety of step press loading charge

Based on the analysis of the changing rules of the maximum stress and density distribution pre-& pro-impact tests,the given paper intends to make a discussion of the effects of the crack width on the impact safety of the step press loading charge.In the paper,we have prepared the samples with density inhomo geneity and different crack widths,with the samples being under the impact loaded by using a drop hammer.The results of our test indicate that the impact safety of the step-press-loading samples tends to increase at first,and,then,decrease with the increase of the crack width.However,when the crack width is less than 0.2 mm,the maximum stress point should be located at the maximum radius of the sample' s upper end with the radial flow tendency of explosive particles being slightly decreased,and the impact safety of the samples with the cracks better than those without cracks.But,when the crack width increases to 1.0 mm,the maximum stress point should be located at the intersection of the cracks whereas the radial flow tendency of the explosive particles would decrease obviously.In such a case,the impact safety of the samples still remains better than those without cracks.However,when the crack width increases to 1.5 mm,the maximum stress point will be located at the intersection of the cracks but the radial flow tendency of explosive particles would basically disappear,with the impact safety of the samples being reduced quite obviously.Thus,it can be predicted through the integrated analysis that,when the loading stress value and the crack size are less than the growth threshold of the cracks,the partial impact energy would be absorbed in the crack closure process,which can be conducive to the increase of the impact safety.But,in contrast,once the cracks tend to grow further,it would be possible for the partial impact energy likely to be absorbed in the crack closure process and,in turn,leads to the eomplicated situation of friction,the shear and fracture would occur in the crack area,which is prone to result in the "hot spot" change with the impact safety of the samples being decreased.In summary,with the increase of the crack width,the main function of the charge crack in the step press loading charge may turn to be changed and result in different loading test effects.