Effect of contact pressure on fretting fatigue failure of oil-well pipe material

As the result of a full-scale test of a thread joint connecting oil-well casing pipes, fretting fatigue failure at the middle of the thread engagement part was identified. The objective of this study is to understand the mechanism of the fretting fatigue failure at the middle of the contact part. A similar failure mode was reproduced by a bridge-pad type fretting fatigue test under gross slip conditions. It was found that the crack position moved from the contact edge toward the inside of the contact part with the progress of the fretting wear.