颗粒炸药撞击加载下能量输运和再分配机理研究

Investigation of impact ignition of granular explosives is crucial to solve the issues related to the safety of energetic materials. During the process of impact ignition, based on the dynamic mechanical response of granular explosives, dynamic transportation and reallocation of energy, including translation, transfer, and deposition can be realized due to mechanical-thermal-chemical coupling. Unfortunately, the understanding to those key processes is still insufficient. Based on the micro and mesoscale information of granular materials, the project intends to establish the multi-physics model embedded with complicated dynamic response via combing peridynamics and discrete element method and coupling mechanical, thermal, and chemical processes. By using large scale simulations, the project will study dynamic processes such as deformation and breakage, collision and jetting, and temperature increase and ignition, explore the influence of granular properties and impact conditions on dynamic processes mentioned above. Moreover, the project will also analyze mechanisms of dynamic energy transportation and reallocation, and eventually boost understanding for impact ignition of granular explosives. The characteristics of this project are to combine microstructure of granular explosives and its macro response and to combine mechanical response and thermal evolution. The new mechanism and new criterion about impact ignition of granular explosives can be achieved based on this research, which have scientific significance for the research of non-shock ignition of energetic materials.

颗粒炸药撞击点火的研究对加深理解含能材料安全性问题有重要意义。撞击点火过程中，颗粒炸药在动态力学响应基础上，由力学-热学-化学反应耦合，实现能量的转化、传递、及沉积等动态输运和再分配。目前对这些关键过程的理解不足。该项目试图从颗粒炸药微细观结构出发，结合近场动力学和离散元方法，耦合力学-热学-化学反应等多物理过程，构建含复杂动态响应的多物理耦合计算模型。通过大规模数值计算模拟，研究颗粒炸药在撞击加载下变形破碎、碰撞抛射、及温升点火等动态过程，探索颗粒炸药物性参数、撞击条件对上述结果影响，分析能量动态输运和再分配机理，推进对颗粒炸药撞击点火过程和规律的认识。该项目将颗粒炸药微细观结构与宏观响应结合，将动态力学响应与温升演化结合，可望得到颗粒炸药撞击点火的新机制和建立新准则，这对含能材料非冲击点火的研究有重要的科学意义。

低速撞击下由于非均匀的能量沉积过程，炸药会出现意外点火现象，从而可能造成巨大的人员和财产损失，因此炸药安全性研究在国防领域具有重要意义。本项目针对颗粒炸药低速撞击点火问题，着力发展相应的数值模拟技术，揭示颗粒炸药撞击点火相关现象内在物理过程及机制。基于离散元和近场动力学模拟，结果显示在不同的撞击速度下，颗粒材料呈现不同的破坏模式，且破坏模式与裂纹形态密切相关，发现随着撞击速度依次增加，呈现赫兹环、赫兹环与短径向裂纹、赫兹环与长径向裂纹、径向裂纹与环向裂纹、更多的径向裂纹与环向裂纹、裂纹分叉等丰富现象。构建了力-热-化学耦合的HMX颗粒炸药落锤撞击点火计算模型，该模型能描述能量转化、传递、沉积物理过程，研究了不同炸药颗粒尺寸、颗粒形状、落锤高度、和样品质量对撞击加载下能量耗散的影响。着重分析了塑性变形、滚动摩擦、滑动摩擦导致的能量耗散机制。发现能量耗散随落锤高度增加而增加，随炸药颗粒尺寸增加而增加。在一定范围内，能量耗散随样品质量减少而增加。通过对比分析不同的能量耗散机制，发现碰撞过程中，炸药颗粒之间的摩擦相互作用导致的能量耗散，是落锤撞击过程中主要的能量耗散机制。基于近场动力学模拟，发现在约束条件下，由于炸药和约束材料之间存在界面，入射应力波在界面上会出现反射、透射等行为，这些应力波动力学行为与炸药动态损伤密切相关。最后也对PBX炸药动态响应进行了数值模拟，通过构建三维近场动力学计算模拟，研究了不同加载条件、物性参数、及损伤模式之间的耦合关系。数值模拟结果加深了对炸药安点火响应问题的理解与认识，同时发展的数值模拟技术对提升炸药安全性数值模拟水平具有推进作用。