变幅载荷对高温合金裂纹萌生及扩展寿命的影响

Effect of Crack Initiation and Propagation Life of High Temperature Alloy under Variable Amplitude

为了更好地分析航空发动机用高温合金裂纹萌生阶段的变幅载荷对高温材料的低周疲劳裂纹萌生及扩展寿命的影响,将低周疲劳的裂纹萌生过程视作损伤累积过程,基于连续损伤力学建立了低周疲劳损伤累积模型。结合室温下GQGH4169合金的裂纹扩展试验数据,通过有限元建模计算和数值分析方法确定了模型中具体的损伤参数数值,并对裂纹萌生寿命进行了预测。结果表明:该方法不但能准确地预测变幅加载下CT试样的裂纹萌生寿命,而且能很好地反映萌生阶段变幅载荷对裂纹扩展寿命的影响,而且降低了试验成本。

The low cycle fatigue crack initiation life was regarded as a process of damage accumulation, based on the continuum damage mechanics, a damage accumulation model was established to analyze the influence of variable amplitude at the crack initiation stage of high temperature alloys on the low cycle fatigue crack initiation and propagation life of high temperature materials. With the crack propagation parameters of GQGH4169 alloy at normal temperature, the specific value of damage parameter was determined by finite element and numerical analysis method. Then, crack initiation life predictions were carried out. The results show that the approach can not only predict the crack initiation life of CT specimen accurately, but also reflect a definite influence of crack propagation life under variable amplitude, and the application reduces the cost.