The mechanics properties and fracture behaviors of 6061 aluminum alloy were investigated by the tensile shear tests and in-situ tensile shear tests with tensile shear specimen devised. The FEM software ABAQUS can be used to describe the fracture behaviors of 6061 aluminum alloy under shear stress states. The results indicate that with increasing the shear strain rates, the shear yield stress and shear ultimate stress of 6061 aluminum alloy remain constant basically, while the shear fracture strain obviously decreases. The shear strain rates have no influence on the fracture surfaces. A lot of slip bands paralleling to the tensile direction are produced on the specimens' surfaces. The grain boundaries of 6061 aluminum alloy are the weakest area, and the microcracks initiate at the slip bands and grain boundaries parallel to the tensile direction under shear stress. With increasing the shear stress, the microcracks extend and coalesce. The specimens fracture due to coalescence or shearing between the microcracks. The Johnson-Cook model can be used to describe the fracture behaviors of 6061 aluminum alloy under shear stress states.%对设计的拉伸剪切试样和原位拉伸剪切试样分别进行不同剪应变率下的拉伸剪切试验及原位拉伸剪切试验,研究6061铝合金在剪力状态下的力学性能及断裂行为,并用有限元软件ABAQUS对铝合金在剪应力状态下的断裂行为进行模拟.结果表明:随着剪应变率的增大,6061铝合金的剪切屈服强度和抗剪强度基本保持不变,但剪切断裂应变明显减小；剪应变率对试样的断口形貌没有影响；6061铝合金晶界是其最薄弱环节,在拉伸剪切过程中铝合金试样表面上产生了大量与拉伸方向平行的滑移带；微裂纹在剪应力作用下形核于与拉伸方向平行的滑移带和晶界,随着剪应力的增加,微裂纹长大和扩展；微裂纹之间通过剪切而连接导致试样断裂；6061铝合金剪切断裂行为可以用Johnson-Cook模型进行描述.
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