GH2036高温合金平板裂纹闭合效应及裂纹扩展模型

为探明GH2036高温合金的低循环疲劳裂纹扩展机理,对GH2036高温合金平板在550℃、不同应力比下的低循环疲劳裂纹扩展特性进行了试验研究,采用数字图像相关(DIC)方法确定了GH2036高温合金的张开应力强度因子。结果表明,温度550℃、应力比大于0.7时GH2036高温合金无裂纹闭合现象,在此基础上建立了以残余裂尖张开位移、应力比为参量的GH2036高温合金裂纹闭合模型。而后,断口的SEM分析表明:随着应力比的增加,裂纹扩展区由穿晶断裂向沿晶断裂转化。最后,基于GH2036高温合金的裂纹闭合模型,建立了GH2036高温合金平板的低循环疲劳裂纹扩展寿命预测方法,与试验数据吻合良好,验证了方法的准确性。

Crack closure effect and crack growth life prediction for GH2036 superalloy plate

In order to examine the crack growth behavior of GH2036 supealloy subjected to low cycle fatigue (LCF) loading, crack growth experiments on GH2036 superalloy plates under different ratios at 550 °C were performed and the crack opening stress intensity factor of GH2036 superalloy were measured using Digital Image Correlation (DIC) technique. It was shown that no crack closure is observed at 550 °C when the stress ratio is greater than 0.7. Meanshile, crack closure model in GH2036 superalloy was established in terms of the residual crack tip opening displacement and stress ratio. In addition, SEM analysis of fracture analysis showed that with the increase of stress raio, the fracture mode at the crack growth region changes from transgranular to intergranular. Finally, crack growth life of GH2036 superalloy under LCF loading was predicted using the established crack closure model in GH2036 superalloy plates. Low life scatter factor through model validation indicated satisfactory results of the predicted crack growth life model.