基于全场法的航空Ti-2Al-1.5Mn钛合金疲劳裂纹扩展各向异性研究

准确定量表征航空重要承载结构材料抗疲劳裂纹扩展能力是实施结构件服役寿命评估的基础。本文针对航空用Ti-2Al-1.5Mn钛合金,沿着板材不同取向制备CT试样开展疲劳裂纹扩展速率试验,分别基于全场法及传统方法定量表征了裂纹扩展各阶段应力强度因子幅DK。结果表明：疲劳裂纹扩展速率da/dN-DK关系及裂纹扩展路径显著受到材料取向的影响。相比较于传统表征应力强度因子幅方法,基于全场法一方面能够直接考虑裂尖塑性变形引起裂纹闭合的影响,另一方面能够有效避免因裂纹扩展路径偏折带来的有效裂纹长度测量偏差,从而不能准确获取有效应力强度因子幅的问题,其具有显著优势。基于全场法的疲劳裂纹扩展应力强度因子幅表征具有广泛应用全景。

Study on anisotropy of fatigue crack propagation of Ti-2Al-1.5Mn titanium alloy based on full-field measurements

Characterizations of fatigue crackSpropagationSresistance of the key bearing structures precisely in aviation area are the basis of its service lifetime evaluation. In this work, Ti-2Al-1.5Mn titanium alloy was selected, some CT samples were prepared along different sheet orientation, the fatigue crack growth rate test was carried out, the stress intensity factor range DK at different crack stage were calculated based on full-field measurements and traditional method. It can be concluded that the fatigue crack growth rate da/dN versus DK curve and crack growth path are affected by material orientation. Compared with the traditional method, DK calculation based on full-field measurements was proved to be more efficient. For one thing, the crack shielding effect due to plastic zone in crack tip can be directly considered. For another, a more accurate DK can be got for the case that the crack path was zigzag. It has a wideSapplication in future of DK calculation based on full-field measurements.