铝型材防撞梁的碰撞断裂失效表征

Characterization of the fracture of an aluminum alloy anticollision-beam to impact loading

作为汽车轻量化的重要材料,铝合金的脆性断裂问题不可忽视。该文以某汽车铝型材防撞梁为研究对象,开展了铝合金静态和动态拉伸、静态剪切、静态缺口、静态拉剪以及穿孔等力学性能试验,获取了铝合金材料在不同应变率下拉伸应力状态的力学特性,以及准静态拉压剪等不同应力状态下的力学属性数据,使用Swift-Hockett-Sherby本构描述铝合金材料应变硬化特性,基于LS-DYNA有限元法模拟对标拉压剪等不同应力状态试验,获得不同应力状态试验的失效单元的应力三轴度和Lode角信息,标定了铝合金材料的修正的Mohr-Coulomb(MMC)断裂准则。通过铝型材动态三点弯结构试验和模拟,验证了MMC断裂模型对于表征铝合金材料在不同应力状态下断裂失效的有效性。

Aluminum alloys are important light materials for vehicle weight reduction, hut they frequently experience fracture under impact loading. This paper describes experimental and analytical methods for characterizing the fracture of aluminum alloy bumper beams. A test matrix is designed to obtain the material mechanical properties at different tensile strain rates and a variety of stress states, including tension, shear, notch tension, tension shear and punch. The Swift-Hockett-Sherby law is used to describe the hardening of the material, with different stress states then simulatedin the L^DYNA finite element analysis environment to get a good correlation. Then, the stress triaxialities and lode angles extracted from the simulations are used to calibrate a modified Mohr Coulomb （MMC） fracture model. Simulations of the material tests and a component bending test with the MMC model correlate well with the test results to support the validity of this method for fracture characterization, as well as the validity of the MMC fracture model for predicting metal fracture.