以2524铝合金与激光熔化沉积TC11钛合金为试验对象，开展了不同载荷条件下的疲劳裂纹扩展试验，采用数字图像相关方法（DIC）对裂纹尖端张开位移（CTOD）进行了测量，研究了CTOD、CTOD变程、CTOD塑性分量、CTOD滞回环面积等参量在疲劳裂纹扩展过程中的变化规律，分析了上述参量与疲劳裂纹扩展速率的相关性，提出了一种以CTOD滞回环面积为主控参量的疲劳裂纹扩展速率模型。研究结果表明，CTOD滞回环面积和CTOD塑性分量与疲劳裂纹扩展速率间均存在明确的关联关系，可有效地表征疲劳裂纹扩展中塑性行为的影响；采用CTOD滞回环面积表征疲劳裂纹扩展速率在恒幅与变幅载荷下均具有适用性，且受测量偶然误差的影响更小，在应用中具有一定优势。
Aluminum alloy 2524 and laser melting deposited TC11 titanium alloy were selected for the Fatigue Crack Growth (FCG) tests under different load conditions, Digital Image Correlation (DIC) method is adopted to obtain the Crack Tip Opening Displacement (CTOD) during FCG, the variations of CTOD, the range of CTOD, the plastic component of CTOD and the area of CTOD hysteresis loop in FCG are investigated. Meanwhile, the relationships between Fatigue Crack Growth Rate (FCGR) and these parameters are further analyzed, and a FCGR model based on the area of CTOD hysteresis loop is proposed. The results show that correspondences between the area of CTOD hysteresis loop and FCGR, as well as between the plastic component of CTOD and FCGR, are clearly revealed under different stress ratios and material orientations, which indicate these two mechanical parameters can effectively characterize the influence of plastic behavior in FCG. The results also indicate that the area of CTOD hysteresis loop is applicable for both constant amplitude and variable amplitude loading conditions, and less affected by accidental measurement errors, which has certain advantages in practical applications.
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