The fatigue crack propagation behaviors of two brands titanium alloys, TC11 and TC4, are studied. Fatigue crack propagation rate tests at room temperature and 400t were carried out. Results of the tests indicate that the experimental data at 400℃ seems more scatter than data at room temperature for both Ti alloys, especially for TC11. The reason of data scatter is discussed. Because of the high data scatter, the linear regression based on the average expectation is no longer suitable. Thus the prediction is non-conservative because of the large deviation of crack propagation rates on the high rate side. A new data fitting policy based on high propagation rale points is proposed. It is found that at room temperature and 400t , the crack propagation rate of TCI 1 is slower than TC4. Consequently TC11 is better than TC4 from the damage tolerance point of view.%TC11和TC4这两种变形对这两种钛合金室温和400℃的疲劳裂纹扩展试验结果及其特性进行了分析.试验结果显示,两种钛合金的室温疲劳裂纹扩展速率的数据比较集中,而400℃时的分散性比较大.通过对造成数据分散性的原因分析,认为以平均值为期望值的线性回归拟合方法会造成偏危险的估计,因此提出了以数据上边界为基础的Paris拟合方法.根据两种钛合金的室温和400℃时的数据,发现TC11的裂纹扩展速率比较低,具有较好的损伤容限性能.
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