CHARACTERISTICS OF THE FRETTING FATIGUE DAMAGE THRESHOLD

It has been found that different variables, such as normal pressure and maximum fatigue stress, affect the fretting fatigue damage threshold, but the degree to which the fretting fatigue damage threshold is influenced by these variables varies from material to material. This is evidenced by the fact that increasing the maximum fatigue stress and keeping the rest of the variables constant through the test caused the damage threshold of 7075-T6 aluminum alloy to disappear, but did not change the damage threshold of Ti-6Al-4V titanium alloy. Increasing the normal pressure from 20.7 to 34.5 MPa and keeping other test variables constant, caused the damage threshold of 7075-T6 aluminum alloy to change from 30% to 20% of fretting fatigue life. An explanation is given for this behavior by presenting a model that links the fretting fatigue damage threshold to fretting-induced damage that is capable of nucleating cracks.