【摘要】 利用标识载荷试验技术,将具有两种不同显微组织TC4钛合金分别在三种应力水平下进行疲劳试验,在光学显微镜下对疲劳裂纹扩展断口进行观察,获得裂纹扩展过程中不同循环周次下的裂纹长度,以此建立了表征TC4钛合金原始疲劳质量的通用EIFS分布。研究结果显示钛合金双态组织比片层组织具有更好的原始疲劳质量,双态组织具有较高的疲劳裂纹萌生寿命及裂纹扩展系数。此外还分析了双态组织中添加标识载荷的疲劳断口形貌,认为其疲劳断口标识线的形成是由于加入标识载荷后,应力强度因子范围发生变化,导致疲劳裂纹扩展过程中断裂模式发生改变,从而在断口上形成了可判读的标识线。更多还原

【Abstract】 Fatigue crack growth a-N data of TC4 titanium alloy with bimodal and lamellar microstructure was obtained from fracture surface by marker load technique.Based on three different stress levels,the general distribution of equivalent initial flaw size(EIFS) was established to describe the initial fatigue quality(IFQ) of the two microstructures.The results show that,compared with lamellar structure,the IFQ of TC4 titanium alloy with bimodal structure is a high level titanium alloy,in which the IFQ is affected by both the initiating cycles of fatigue crack and the crack propagating coefficient.The fracture morphology in bimodal microstructure by marker load technique was analyzed.It was revealed that the model of fatigue crack propagation changed after the marker load added,which lead to the readable marker line in fracture surface.更多还原