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应用有限元方法和断裂实验对铝合金材料Ｌｙ１２和４０ＣｒＮｉＭｏ钢在Ⅰ＋Ⅱ型载荷下启裂韧度ＪＭＣ的测定方法及弹塑性断裂行为进行了研究，给出了２种材料复合断裂的Ｊ积分准则．结果表明：１）根据复合型ＪＲ阻力曲线，应用裂纹延伸区零扩张量法测定的不同复合比下的启裂韧度ＪＭＣ值能够满足工程精度，且简便易行；２）不同复合比下的启裂韧度ＪＭＣ值满足一定的关系式．只要能得到材料的ＪⅠＣ、ＪⅡＣ值，任何复合比下的ＪＭＣ值都可由一定的关系式计算得到．另外，得出了适用于具有较好塑韧性和中高强度材料的复合型弹塑断裂准则
The determination method and elastoplastic fracture behavior of cracking initiation toughness of aluminum alloy Ly12 and 40CrNiMo steel under load type Ⅰ + Ⅱ are studied by finite element method and fracture mechanics. The J integral criterion for composite fracture of two kinds of materials is given. The results show that: 1) According to composite JR resistance curve, the crack initiation toughness (JMC) under different composite ratios measured by zero-expansion method of crack extension area can meet the engineering accuracy and is simple and easy to implement; (2) Fracture toughness JMC value to meet a certain relationship. As long as the material can be JI C, J Ⅱ C value, the JMC value of any composite ratio can be calculated by a certain relationship. In addition, the composite elastic-plastic fracture criterion that is suitable for plastic materials with good ductility and high strength