宽温宽应变率范围下PBX炸药破坏准则及细观变形机制研究

The deformation and failure of high energy PBXs greatly influence the structural reliability and safety of PBX components during their life cycle. It is increasingly desired to study the deformation behaviors and failure characteristics of PBXs over a wide range of temperature and strain rate under complex stress states, and it is also of great importance on engineering design and assessment of weapon system. This study will aim at the technical bottleneck and general problems in science that are required to solve emergently in development periods of special weapon equipments. This proposed project for fundamental research focuses on experimental techniques for mechanical measurement of PBXs over wide ranges of temperature(-20 to 80 C) and strain rate(10^-4 to 10^2/s) under complex stress states. The static and dynamic properties of typical PBX under different stress states and at various temperatures will be measured experimentally, and primary mechanical properties will be obtained systematically. Studies into viscoelasticity of PBX for wide range of strain rate will be performed so that the creep strength model and rate-temperature equivalency available for wide ranges of temperature and strain rate can be constructed. The intrinsic relations between the deformation mechanisms under thermal environment and high velocity deformation mechanisms at normal temperature will be revealed. Optical microscopic and mesomechanics analyses will be conducted to investigate the deformation, damage and fracture mechanisms of PBX at various temperature and strain rates. Based on mesomechanics for heterogeneous brittle materials and dynamic experimental researches, the three dimensional temperature-strain rate dependent constitutive model and failure criterion for typical PBX subjected to complex stress states will be proposed.

高能炸药的变形与破坏直接关系到炸药构件在全寿命周期的结构可靠性与安全性，开展炸药在复杂应力状态下、宽温宽率范围的变形与损伤研究，对武器设计与评估具有极其重要的作用，需求迫切。本项目面向武器装备研制中出现的亟待解决的技术瓶颈问题及共性科学问题，针对典型PBX开展复杂应力状态下宽温(-20至80 C)宽应变率(准静态至10^2/s)范围内的实验技术研究，对典型PBX进行不同温度和不同应力状态下的实验测试，获得炸药较完整的力学性能数据；开展PBX宽温宽率范围的粘弹性理论分析，建立材料强度模型以及宽温宽率的率-温等效模型，揭示PBX炸药热环境变形机制与常温高率形机制之间的内在联系；开展细观组织形貌与细观力学分析，揭示固体炸药温度-应变率相关的变形、损伤及破坏机制，基于脆性多相非均质材料细观力学理论分析以及冲击动力学实验研究，建立复杂应力状态下典型PBX炸药温度-应变率相关的三维本构与破坏准则。

PBX炸药是重要的放能材料与承力材料，广泛应用于国防装备研制。在外界力-热环境下PBX材料的力学行为对炸药构件的完整性和安全性有重要影响，也影响到装备可靠性和安全性。研究炸药在复杂应力状态下的力学行为，是国防装备研制中的重要课题，研究成果在国防装备研制中具有直接应用价值。. 主要研究内容：1）采用广义塑性理论，研究PBX的准静态变形与破坏行为；分析热环境下PBX厚壁球热应力问题与失效问题。2）分析PBX屈服函数等、增量本构模型，对PBX裂纹的萌生与扩展进行模拟。3）研究PBX材料弹脆性、弹塑性以及粘弹性力学行为的近场动力学分析方法，开展PBX炸药裂纹扩展问题模拟。4）研究PBX构件动态实验技术。5）基于三失效面的本构模型；6）分析伪多晶法预测有效模量，分析PBX力学响应的温度、应变率相关性；采用代表性体积单元研究颗粒分布形式、颗粒形貌对有效模量的影响。. 重要结果：（1）构建了基于D-P模型的增量型弹塑性本构模型，且应用与多种应力状态下PBX弹塑性准静态变形分析，获得了与实验相一致的结果；获得了结构承受温差的能力与材料性能及结构系数之间的关系。（2）建立宽温宽应变率范围内线性PBX率-温等效原理；预测了材料的应变率相关的失效应力数据；结合细观力学方法得到PBX力学响应的温度、应变率相关性。（3）揭示了含孔洞的PBX炸药在整体压缩下裂纹萌生到裂纹扩展全过程的开裂破坏机理。（4）建立了PBX蠕变模拟的近场动力学方法；建立了适用于PBX准脆性材料近场动力学模拟方法。（5）建立了可应用于安全性分析的三失效面本构模型。（6）初步建立了考虑颗粒间不同相互作用的应变集中张量修正法与考虑颗粒形貌的Eshelby张量修正法；提出了“伪多晶法”预测PBX有效弹性模量，精度上有很大提升；初步构建了PBX的双分布模型，使得有效模量的计算趋于合理。