We report the fatigue striation spacing of commercially pure titanium with respect to stress amplitude. Rotating bending fatigue tests were performed at 150, 175, 200 and 227 MPa in which samples did not fail at 150 MPa. No fatigue striation up to a certain crack length is observed for the studied conditions. For each condition, a minimum striation spacing value is found that decreases from 0.45 to 0.36 to 0.24 μm with increasing stress from 175 to 200 to 227 MPa, respectively. The minimum striation spacing remains constant up to a certain crack length for each condition. Thereafter, it starts increasing with crack length. It is quite understandable that the constant striation spacing over a certain crack length may not represent the macroscopic fatigue crack growth rate. The fatigue crack growth mechanism during the constant striation spacing region has been discussed in detail.

中文翻译：

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商业纯钛的最小疲劳条纹间距及其应力幅度依赖性

我们报告了相对于应力振幅的商业纯钛的疲劳条纹间距。旋转弯曲疲劳试验分别在150、175、200和227 MPa下进行，其中样品在150 MPa时不会失效。对于所研究的条件，未观察到直至一定裂纹长度的疲劳条纹。对于每种条件，发现最小条纹间距值从0.45减小到0.36到0.24μm，而应力分别从175增大到200到227 MPa。在每种情况下，最小条纹间距一直保持恒定，直至达到一定的裂纹长度。此后，它随着裂纹长度开始增加。完全可以理解的是，在一定的裂纹长度上恒定的条纹间距可能无法代表宏观疲劳裂纹的增长率。