损伤力学方法在材料低周疲劳试验中的应用研究

考察了低周疲劳过程中的弹性模量和应力随循环次数的变化.研究表明:可以用弹性模量和应力的变化来反映材料的低周疲劳损伤过程.对没有明显循环稳定阶段并表现为循环软化响应行为的材料,不适合用应力的变化来定量的反映材料低周疲劳的损伤过程.用弹性模量随循环次数的演化关系得到了不同应变水平下材料的疲劳裂纹萌生寿命,并用三参数幂函数方程对应变与疲劳裂纹萌生寿命进行了拟合处理,得到了应变与疲劳裂纹萌生寿命方程.

Application research of damage dynamics for low cycle fatigue test

The change of elastic modulus and stress associated with fatigue cyclic number was investigated during low cycle fatigue.The research shows that,the low cycle fatigue damage can be determined by the change of elastic modulus and stress.For the materials,which have no cyclic steady stage but exhibit cyclic softening,this method isn't suitable to determine the low cycle fatigue damage with the change of stress.The fatigue crack initiation life was acquired by the change of elastic modulus under different strain levels,so the relationship between strain and fatigue crack initiation life was determined by three parameters power equation.