钛合金扩散焊接头复合型疲劳裂纹扩展

设计并加工了TC4扩散焊接头紧凑拉伸剪切(CTS)试样。开展了不同加载角度下的Ⅰ-Ⅱ复合型疲劳裂纹扩展试验。试验结果发现:在加载角度小于45°时,裂纹均沿焊缝扩展至断裂,当加载角度达到45°以上时,裂纹开始出现沿与初始裂纹面呈一定角度的方向扩展至母材的情况。使用电子显微镜结合电位法获得了裂纹扩展a-N曲线。在此基础上,采用相互作用积分法计算复合型应力强度因子,以应变能释放率为参量对Ⅰ-Ⅱ复合型裂纹扩展过程进行了分析。考虑Ⅱ型裂纹所占权重引入复合比,并在此基础上建立了TC4扩散焊接头不同加载角度及载荷下Ⅰ-Ⅱ复合型疲劳裂纹扩展速率统一模型。 

Mixed-mode fatigue crack propagation of titanium alloy diffusion bonded joints

Compact tensile shear（CTS) specimens of TC4 diffusion bonded joints were designed and processed. The fatigue crack propagation tests of Ⅰ-Ⅱ mixed mode under different loading angles were carried out. The test results showed that when the loading angle was less than 45 degrees, the cracks propagated along the weld line. When the loading angle was more than 45 degrees, the cracks started to propagate along base metal at certain angle. The a-N curves of crack propagation were obtained by electron microscopy in combination with potential method. Based on the test results, the interaction integral method was used to calculate the stress intensity factor, and the Ⅰ-Ⅱ mixed crack propagation process was analyzed based on the strain energy release rate. Finally, considering the weight of crack mode Ⅱ, the composite ratio was introduced. On this basis, a unified model of Ⅰ-Ⅱ mixed crack propagate rate of TC4 diffusion bonded joints under different loading angles and loads was established.