TC4焊接接头多元竞争失效分析及寿命预测

Multivariate competitive failure analysis and life prediction of TC4 welding joint

针对TC4焊接接头多裂纹源竞争失效机制,提出一种超高周疲劳寿命预测方法。在应力比为-1以及应力幅值300 MPa下对接头开展超高周疲劳试验,以探究其超高周疲劳性能。通过扫描电镜对TC4焊接接头的疲劳断口观察可知,断口内部总计有三处裂纹起裂点,并在载荷持续作用下均得到了不同程度的扩展。进一步结合应力强度因子计算以及断口形貌,绘制断口内部的多元竞争机理图。分析表明,三处缺陷诱发的疲劳裂纹均在不同程度上降低了焊接接头的疲劳寿命,其中1号气孔诱发的裂纹在TC4焊接接头的失效过程中占据主导位置。基于竞争失效分析,构建了一种适用于多裂纹源疲劳失效的寿命预测方法,模型预测结果较好。

A super high cycle fatigue life prediction method is proposed for the competition failure mechanism of multiple crack sources in TC4 welded joints.Ultra-high cycle fatigue tests were conducted on the joint under a stress ratio of-1 and a stress amplitude of 300 MPa to investigate its ultra-high cycle fatigue performance.Through scanning electron microscopy observation of the fatigue fracture surface of TC4 welded joint,it was found that there was a total of three crack initiation points inside the fracture surface,which all expanded to varying degrees under continuous loading.The calculation of stress intensity factor and fracture morphology was combined to draw a multivariate competition mechanism diagram within the fracture surface.Analysis shows that the fatigue cracks induced by three defects all reduce the fatigue life of welded joints to varying degrees,with cracks induced by No.1 porosity occupying a dominant position in the failure process of TC4 welded joints.Based on the competitive failure analysis,a life prediction method applicable to fatigue specimens with multiple crack sources is established,and the model can achieve better predictions.