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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。
In order to find out the mechanism of low cycle fatigue crack propagation in GH2036 superalloy, the low cycle fatigue crack growth behavior of GH2036 superalloy at 550 ℃ and different stress ratio was studied. The digital image correlation (DIC) Open stress intensity factor of superalloy. The results show that the crack growth of GH2036 superalloy is closed at a temperature of 550 ℃ and a stress ratio of more than 0.7. Based on this, a crack closure model of GH2036 superalloy is established with the residual crack tip open displacement and stress ratio as parameters. Then, SEM analysis of the fracture shows that with the increase of stress ratio, the crack propagation region transforms from transgranular fracture to intergranular fracture. Finally, based on the crack closure model of GH2036 superalloy, the method for predicting the fatigue life of low cycle fatigue crack growth of GH2036 superalloy was established, which is in good agreement with the experimental data and verified the accuracy of the method.