表面加工介观状态对金属柱壳绝热剪切断裂影响的细观动力学规律及其表征模型研究

Metal cylindrical shell is the representative of the typical structure of the warhead. Concern about the details of dynamic fracture process is one of the most important aspects of the design of modern weapons. The related theoretical model and numerical simulation based on microstructures and properties of body material can not achieve a reasonable explanation and prediction on some experimental appearances of adiabatic shear deformation instability and unstable fracture of metal cylindrical shell, such as self organized shear bands and the exclusive selection of shear bands orientation et al. The project intends to study the meso-dynamics law of the effect of the difference of surface machining mesoscopic state (surface topography, strain-hardened layer, residual stress, et al.) on the adiabatic shear fracture of the metal cylindrical shell. Based on dislocation dynamics, strain gradient theory, fracture mechanics and the model of interaction between shock wave and residual stress, an attempt to establish the meso material model and the meso mechanical model considering the effect of surface mesoscopic state is performed. Combination with experimental observations, theoretical analysis and numerical simulation, the mesoscopic physical image of the effect of surface topography, microstructure of material, residual stress due to surface processing on the metal cylindrical shell adiabatic shear instability and fracture is studied. The study will obtain the sensitivity factors and the physical mechanisms of the origin and development of cylindrical shell shear fracture. The study has important scientific significance and value of the establishment of dynamic fracture theory, computational simulation models and carrying out real quantitative engineering design of metal cylindrical shell.

金属柱壳是战斗部典型结构的代表，关注其动态断裂过程的细节，是现代武器设计中最重要的环节之一。基于柱壳体材料微结构和性能的相关理论模型和数值模拟，尚未能对柱壳的绝热剪切变形和失稳断裂有关实验现象细节(如剪切带单旋等)做出合理的预测和物理解释。本项目拟通过研究切削加工后材料表面介观状态(表面形貌、硬化层、残余应力等)差异对金属柱壳绝热剪切变形和断裂影响的细观动力学规律；基于位错动力学、应变梯度理论、断裂力学、冲击波与残余应力相互作用模型，建立考虑表面加工介观状态各物理量影响、描述金属柱壳绝热剪切变形的细观材料模型和力学模型。结合实验观察、理论和数值分析，研究切削加工引起的材料表面介观状态差异对金属柱壳绝热剪切断裂影响的细观物理图像，获得其影响金属柱壳动态断裂起源和发展的敏感性因素及其物理机制，对建立金属柱壳动态断裂理论、计算模拟模型和开展实际工程的定量化设计，具有重要的科学意义和价值。

金属柱壳是武器战斗部典型结构的代表，关注影响其动态断裂过程的细节，是现代武器设计中最重要的环节之一。现有基于柱壳体材料微结构和性能的相关理论模型和数值模拟，尚未能对柱壳的绝热剪切变形和失稳断裂有关实验现象细节(如剪切带自组织和单旋等)做出合理的预测和物理解释。本项目基于实验研究、数值模拟和理论分析相结合的研究方法，系统研究了表面加工介观状态(表面粗糙度、表面加工塑性层和残余应力)差异对金属柱壳绝热剪切变形和断裂的影响，重点研究了表面粗糙度和表面加工塑性层变化对金属柱壳绝热剪切变形和断裂影响的细观动力学规律、表征模型和物理机制，取得了以下主要进展。建立了具有不同表面加工介观状态的金属柱壳加工及其各状态参量之间的解耦方法；获得了表面粗糙度、表面加工塑性层和残余应力变化对金属柱壳绝热剪切断裂影响的细观动力学规律；建立了表面粗糙度大小和峰谷单元平均宽度变化的数学模型；建立了表面粗糙度大小和峰谷平均宽度变化对金属柱壳绝热剪切断裂影响的表征模型，阐明了表面粗糙度大小和峰谷平均宽度变化对金属柱壳绝热剪切断裂影响物理机制；建立了表面粗糙度几何构型变化诱发剪切带自组织单旋现象的分析模型，阐明了由表面几何构型诱发剪切带自组织单旋现象形成的物理机制；建立了表面加工塑性层及其微纳结构对柱壳绝热剪切带单旋现象影响的表征模型，探索了表面加工塑性层及其微纳结构诱发柱壳绝热剪切带单旋现象形成的物理机制。结果表明，随着试样内表面粗糙度的增大，剪切带数量、长度、形核速率和扩展速率均增加，剪切带的屏蔽效应越明显，剪切带裂纹形核数量增加；表面粗糙度对钛合金柱壳多重剪切带自组织行为的影响具有组织敏感性；随着柱壳内表面塑性层厚度的增加，其剪切带数量、长度、形核速率和扩展速率均增大，多重剪切带越倾向单旋结构；表面加工残余应力越大越容易发生膨胀断裂，越小越不容易发生膨胀断裂。研究结果对建立金属柱壳动态断裂理论和计算模拟模型，开展实际工程的定量化设计，具有重要的科学意义和价值。