典型高聚物黏结炸药在不同温度下的脆韧转换机制

Brittle⁃Ductile Transition Mechanism of Typical Polymer Bonded Explosives(PBX)at Different Temperatures

为研究典型高聚物黏结炸药(PBX)在温度影响下剪切带和脆韧转换行为的关系,结合DIC数字图像技术,测试PBX在323~363 K下的剪切带参数,对剪切带演变规律与破坏模式进行深入分析。基于裂纹滑移理论模型,分析温度效应下PBX的脆韧转换机制,得到翼裂纹失稳扩展和塑性滑移区的判定条件。结果表明:在323~363 K下,PBX的剪切带宽度变化取决于剪胀和剪缩的竞争机制,其主要机制有4类:Ⅰ:剪胀与剪缩达到平衡;Ⅱ:剪缩占优;Ⅲ:剪胀占优;Ⅳ:剪胀间歇性占优。结合Griffith能量释放原理,发现试件的剪切强度、粘聚力、断裂韧度是脆韧转换的控制因素,并以此为基础,进一步获得了PBX脆韧转换的判定依据:当满足翼裂纹失稳的条件时,宏观破坏模式趋于劈裂破坏;当满足塑性滑移区的临界生成条件时,多个滑移区相互连接形成塑性滑移面,宏观破坏模式以剪切裂纹滑移的韧性断裂为主导。

To study the relationship between shear band and brittle‑ductile transition behavior of typical polymer bonded explo‑sives(PBX)under the influence of temperature,the mechanical response of PBX at 323-363 K was tested by using DIC digital image technology,in‑depth analysis of shear band evolution law and failure mode.At the same time,the brittle‑ductile transi‑tion mechanism of PBX under temperature effect was analyzed based on the theoretical model of crack slip.And the critical con‑ditions of wing crack development and plastic slip area were obtained by considering the effect of temperature.The results showed that at 323-363 K,the variation of the shear band width of the PBX depended on the competition mechanism of dilation and shrinkage.There are four main mechanisms:Ⅰ.Dilatation and shrinkage reach equilibrium;Ⅱ.Shrinkage is dominant;Ⅲ.Dilatation is the main controlling factor;Ⅳ.Dilatation dominates intermittently.Combined with the principle of Griffith energy release,it is found that the shear strength,cohesion and fracture toughness of the specimen are the key controlling factors of the brittle‑ductile transition.Under the condition,the judging basis of PBX brittle‑ductile transition was obtained.When the condi‑tion of wing crack instability was met,the macroscopic failure mode tends to split failure;and when the critical condition of the plastic slip area was achieved,the multiple slip zones are connected to each other to form a plastic slip surface,and the macro‑scopic failure mode was dominated by the ductile fracture of shear crack slip.