高应变率下韧性碎裂的实验和理论研究

The study on the fragmentation phenomenon of ductile materials under impact loadings has significant scientific interests and engineering values. It has been shown that the fragmentation process is closely related to the material's ductility, the applied strain rates, the defects distributions, etc. To investigate the effects of these factors, a new experimental apparatus, based on the Split Hopkinson Pressure Bar (SHPB), will be developed for conducting expanding ring tests. Using this experimental apparatus, we will experimentally study the dynamic tensile deformation and fragmentations of the circular ring specimen made of ductile metals. The effects of the fracture energy, the loading rates, and the initial defects on the fragment size and size distribution will be examined. Based on the experimental study, we will establish the relationship linking the one-dimensional fragmentation properties to the material properties and the loading conditions. We will further expand the 1D fragment theory to the 2D case, through theoretical and numerical analyzes. These investigations will enrich people's understanding on the phenomenon of dynamic fragmentations, and provide theoretical basis for the design of engineering applications.

固体在冲击载荷下的动态碎裂现象具有很强的科学意义和工程应用价值。碎裂过程与材料的韧性、应变率、以及缺陷等密切相关。本项目建立一个基于分离式Hopkinson压杆的冲击膨胀环实验平台，实验研究典型韧性金属圆环在冲击拉伸载荷作用下的碎裂过程，研究断裂能、加载速率、初始缺陷等因素对一维碎片尺寸及尺寸分布的影响；进一步，面向工程应用，分析和模拟卸载波在二维等轴拉伸过程中的传播规律，建立二维碎裂尺寸模型。研究成果将加深人们对韧性冲击碎裂过程的理解，为工程设计提供理论依据。

总结前期研究成果，提出了材料在高应变率拉伸载荷作用下的最快速卸载理论，可以较好的预测韧性碎裂和脆性碎裂过程中产生的碎片尺寸；建立了液压冲击膨胀环实验平台，包括实验装置、测试技术和诊断技术；研究了典型韧性碎裂过程及应变率、损伤演化规律、初始缺陷等因素对碎裂过程的影响；采用流固耦合的有限元方法模拟了韧性材料的拉伸碎裂过程，采用离散颗粒动力学方法模拟了脆性材料的拉伸碎裂过程；开展了粘弹性材料和脆性材料在高应变率拉伸载荷作用下的碎裂过程的实验研究。