Fretting Fatigue Behavior of the Titanium Alloy Ti-6AL-4V Under Seawater Conditions

摘要

The fretting fatigue behavior of Ti-6A1-4V was investigated in laboratory air and under a controlled environment consisting of synthetic seawater. Fretting fatigue tests were performed for both low and high cycle fatigue regimes. Finite element analysis was utilized to model and analyze the experimental data. The applied stress range and the Modified Shear Stress Range were evaluated as potential fatigue parameters. The results found from this study can be summarized as: (1) seawater had a deleterious effect on fretting fatigue life in the low cycle fatigue regime but improved life in the high cycle fatigue regime, (2) although the Q/P ratio for both conditions increased with an increasing applied stress, the difference between the two conditions was negligible, (3) debris from dry samples contained titanium and oxides while the debris from seawater samples contained titanium, oxides, and seawater contaminants, (4) fretting scar volume was larger under seawater conditions than dry conditions, (5) there were more, closely spaced striations on the fracture surface of the dry samples than of the seawater samples, and (6) both the applied (far field) stress range and the Modified Shear Stress Range can potentially be used as conservative fretting fatigue parameters under high cycle fatigue conditions.