利用实验和数值结合的方法测量镁合金AZ91动态断裂韧性

利用Hopkinson压杆实现镁合金AZ91三点弯曲断裂试件的动态加载，基于傅里叶变换和VC++面向对象的程序设计方法修正了加载应力波在传播过程中的弥散效应，同时扣除了附加加载杆楔形头惯性效应对加载波的影响。利用ANSYS/LS-DYNA有限元软件对三点弯曲试样在冲击载荷下的动态响应进行了分析，采用虚拟裂纹闭合技术求得动态应力强度因子时程曲线，依据监裂应变计测试信号，换算起裂时间，确定对应于动态应力强度因子时程曲线的值，即为镁合金AZ91的动态断裂韧性。本文提供的实验和有限元数值计算相结合获得镁合金断裂韧性的方法为镁合金构件抗冲击设计和动态载荷作用下结构的安全评定提供依据，也拓宽了Hopkinson压杆实验技术在测试材料动态断裂韧性方面的应用范围。

Measuring the Dynamic Fracture Toughness of Magnesium Alloy AZ91 by Combining Experimental and Numerical Methods

The dynamic load for the three-point bending specimen is supplied by the Hopkinson pressure bar, and the dispersion and inertia effect are accounted in and corrected by numerical method, simultaneously, based on the FFT and the VC++ object-oriented programming method. Then the response of dynamic stress intensity factor vs. time is calculated with visual crack close technique method based FEM. Finally, the crack initiation time is computed from the strain gauge message, and the corresponding value on the response of dynamic stress intensity factor vs. time is obtained as the dynamic fracture toughness. Noting that, the contact of supports and specimen affects seriously for the results validation, which is guaranteed by the monitoring message. The results supply the dynamic fracture toughness data for engineering application of Magnesium alloy, and method mentioned extends the application of Hopkinson pressure bar for measurement of dynamic fracture toughness. The combining method of experimental and numerical for dynamic fracture toughness measurement of Magnesium alloy AZ91 has supplied basic data for the design of the anti-impact Magnesium alloy component and safety assessment of structure under dynamic load, and also extends the application of Hopkinson pressure bar for measurement of dynamic fracture toughness.