Low‐pressure and long‐pulse loadings are critical loading modes in research on non‐shock ignition. Under such loadings, viscoplastic deformation, fracture, and a local rise in temperature may occur around inherent defects in condensed explosives to cause non‐shock ignition. In this study, transparent poly(methyl methacrylate) was chosen as an explosive simulant to elucidate the processes of crack growth, pore collapse, and rise in temperature at a cylindrical defect by using a set of modified split Hopkinson pressure bars. A recently developed optical temperature‐sensing technique that uses the multiphonon‐assisted anti‐Stokes‐to‐Stokes fluorescence intensity ratio was used to monitor the rise in temperature in the cracks. By combining the work here with our previous research, two significant conclusions are arrived at: 1) Around the cylindrical defect, the opening‐mode crack initiated earlier than the shearing‐mode crack did but its rate of propagation was considerably lower. Moreover, the smaller the cylindrical defect was, the lower was the rate of propagation of the cracks. 2) The rise in temperature in shearing‐mode cracks was higher than that of the opening‐mode cracks. It can be inferred that the local rise in temperature caused by shearing was the major factor leading to the non‐shock ignition of condensed explosives

中文翻译：

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在低压和长脉冲载荷下测量爆炸模拟物圆柱缺陷周围的裂纹扩展和温度升高

低压和长脉冲载荷是非冲击点火研究中的关键载荷模式。在这样的载荷下，凝聚炸药的固有缺陷周围可能会发生粘塑性变形，破裂和局部温度升高，从而引起非电击点火。在这项研究中，选择透明聚甲基丙烯酸甲酯作为爆炸性模拟剂，以通过使用一组改进的剖分式霍普金森压力棒来阐明圆柱缺陷处的裂纹扩展，孔塌陷和温度升高的过程。最近开发的一种光学温度感测技术使用多声子辅助的反斯托克斯对斯托克斯荧光强度比来监测裂缝中的温度升高。通过将此处的工作与我们先前的研究相结合，得出了两个重要的结论：1）在圆柱状缺陷周围，开裂形式的裂纹比剪裁形式的裂纹更早地开始，但是其扩展速率却低得多。而且，圆柱状缺陷越小，裂纹的扩展率越低。2）剪切模式裂纹的温度升高高于开口模式裂纹的温度升高。可以推断，剪切引起的局部温度升高是导致未爆炸爆炸物爆炸的主要因素