考虑初始裂纹分布的PBX炸药低速撞击点火研究

The ignition prediction of polymer bonded explosives (PBXs) under low velocity impact is critical for the safety of explosives and weapons. The probabilistic ignition of PBXs under low velocity impact highly depends on initial crack heterogeneous distribution inside PBXs, and further could not be predicted based on traditional material constitutive models, which plays a critical role and a big challenge for the safety assessment of explosives..The evolution of initial heterogeneous cracks could result in energy localization related to the ignition. However, the relevant among the crack heterogeneous distribution, energy localization and the probabilistic ignition is still not clear. This project investigates the probabilistic ignition of HMX-based PBX under low velocity impact by means of testing techniques, material constitutive model and statistical method, with the aim of critical scientific issues as follows: (1) Non-destructive testing techniques, including small-angle x-ray scattering (SAXS), micro-CT and optical microscopy, are applied to analyze the feature of the spatial distribution, size, and density of the initial crack inside PBX by means of image processing techniques, and further to quantify the stochastic feature of the crack based on statistic method. (2) Considering the characteristic of initial heterogeneous cracks, a macro-microscopic material constitutive model is developed. (3) The method of the prediction of probabilistic ignition is proposed for revealing the mechanism of ignition in view of macro-microscopic level based on the mechanical-thermal response under the low velocity impact, such as Steven test and Spigot test..The methodology of the ignition prediction developed in this project offers a theoretical basis and methodological support for safety assessment of explosives. Furthermore, it probably offers a practical value for the improvement of the capability to predict the safety of weapons and the development of the safety strategy to use weapons.

对高聚物粘结炸药（PBX）低速撞击点火预测是提升炸药甚至武器安全性的基础，低速撞击随机点火预测与炸药内部裂纹细观非均匀性密切相关，尚不能被传统材料本构模型所描述，这也是炸药低速撞击点火与炸药安全性研究的难点。本项目针对低速撞击炸药内部裂纹非均匀性的演化、能量局域化过程与炸药点火概率关联性等问题，以HMX基PBX炸药为研究对象，采用包括小角散射、Micro-CT和光学显微镜在内的无损检测技术，结合图像处理技术与统计分析方法，确定炸药初始裂纹的空间位置分布、尺寸和数密度等非均匀性分布特征。建立考虑初始裂纹非均匀性的PBX炸药宏细观材料本构模型，形成炸药随机点火预测方法，获得炸药Steven试验和Spigot试验等典型低速撞击点火的力-热响应特征，揭示PBX炸药随机点火宏细观机理，为炸药安全性的评估提供理论支撑和方法依据，对提高我国武器安全预测能力并制定安全策略具有实际价值。

复杂多样的战场环境对武器弹药提出了更高的要求，炸药作为武器弹药核心部件在加工、运输、贮存、使用过程中存在意外撞击的情况，有可能发生意外点火甚至爆炸，导致极其严重的后果。炸药点火行为受自身材料属性和外界载荷等多因素控制，形成机理复杂。因此，研究炸药撞击点火行为及机理，准确预测其安全阈值条件以满足武器弹药升级换代的需要至关重要。. 本项目以经典的Visco-SCRAM模型和微裂纹表面摩擦生热的热点形成模型为基本框架，建立了炸药力-热-化耦合宏细观本构模型，通过典型的炸药Steven低速撞击点火实验，验证了模型的有效性。进一步通过有限元重启技术，研究了多次撞击条件下炸药点火行为，获得了多次撞击条件下临界点火速度阈值、损伤演化、点火位置和点火时间等特征。研究结果表明，随着连续损伤的积累，临界点火速度阈值降低。. 微裂纹演化对炸药低速撞击点火行为起着至关重要的作用，发展了精细化的统计裂纹演化模型，与宏观粘弹性体融合形成了炸药宏细观本构模型，能够准确地捕捉炸药在撞击过程中损伤形貌。进一步结合了蒙特卡洛方法，构建了考虑初始裂纹非均匀性的炸药随机点火行为计算方法，系统研究了初始裂纹数密度与特征长度的非均匀性对炸药点火概率的影响。研究结果表明，随着初始裂纹特征长度非均匀性程度增加，炸药点火速度阈值降低。随着初始裂纹数密度分散性增加，炸药发生点火概率增加。. 基于上述具有高保真的炸药低速撞击点火行为有限元模型，开展了大量的炸药低速撞击点火行为数值模拟，建立了可靠的炸药点火行为虚拟数据库，提出了一种基于数据驱动的炸药点火行为高效预测方法。与传统经典的机器学习模型相比较，提出的机器学习模型具有更高的准确性和效率。. 上述研究成果解决了炸药安全性精准评估的难题，提升了我国典型武器弹药安全性设计水平。为保障重大武器装备服役可靠性提供了理论及技术支撑。