Minimum fatigue striation spacing and its stress amplitude dependence in a commercially pure titanium

摘要

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.