延性金属拉伸型断裂物理机制及损伤演化规律研究

项目名称： 延性金属拉伸型断裂物理机制及损伤演化规律研究

项目编号： No.10876014

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 轻工业、手工业

项目作者： 王永刚

作者单位： 宁波大学

项目金额： 35万元

中文摘要： 以典型延性金属纯铝作为研究对象，开展了不同外载荷条件下的层裂实验，建立了从样品材料设计到波剖面测量、微细观表征相结合的实验方法，详细分析了晶粒度、晶粒排布和晶粒取向对材料损伤演化的影响，揭示了拉伸断裂微损伤状态与材料微结构之间的内在联系，并对微孔周围基体的组织结构进行了初步的表征，获得了材料失效机制的新认识。通过对材料的宏观实时测量数据和损伤细观统计数据进行深入系统地分析，找出了材料从初始损伤到完全断裂所表现出的规律性变化，再结合相关的数值模拟结果，在物理机制方面深化了对延性金属微损伤演化规律的认知，为指导损伤断裂理论模型的建立提供了物理依据。基于封加波损伤度函数和逾渗理论，构建了一个临界损伤度物理模型，并提出了逾渗软化函数的应力松弛机制，首次将内聚力模型引入到损伤破坏的研究中，合理解释了拉伸断裂自由面速度波剖面的规律特征，特别是自由面速度"回跳"后波形振荡特征，从而完善了临界损伤度物理模型。最后，把临界损伤度物理模型嵌入瞬态动力学有限元程序中，完成了内爆加载柱壳构形样品拉伸断裂的三维数值模拟，初步检验了模型在描述不同构型样品损伤破坏行为方面的普适性。

中文关键词： 层裂；损伤演化；微结构；临界损伤度；数值模拟

英文摘要： A series of spall experiments of pure aluminum were performed under different loadings by combining the design of specimen, the measurement of wave profiles and the microscopic statistics of damage characteriaztion. The influences of the size of grain,the arrange of grain and the orinentation of grain on damage evolution were investigated carefully.The relationship between damage evolution and microstructure of material was explored by the metallographic analysis of the matrix around the micro-void. Based on the results of experiments and numerical simulations, the rule of damage evolution in ductile metals under dynamic tensile fracture was revealed. Based on the damage function proposed by Feng Jiabo and percolation theory,a critical damage fracture model was established to describe the dynamic tensile fracture of metals. In order to describe the quick stress relaxation due to the void-coalescence process, a Percolation-Softening function was proposed. Meanwhile, a cohesive zone model was introduced firstly to study the importance of stress relaxation during the spallation of metals.A satisfied agreement was obtained bewteen the predictions and the experimental data,especially the oscillation frequency and decay of the wave profiles. To verify the practicability of the critial damage model, the spall experiments of metallic cylindrical shells under sliding detonation of high explosive were simulated by using the Ls-dyna incorporated such dynamic damage model.A good agreement between the simulations and the experiments demonstrated the good applicability of the critical damage model to describe the intrinsic characteristic of dynamic tensile fracture in explosion and shock wave events.

英文关键词： Spall；damage evolution；microstructure； critical damage；Numerical simulation