Improvements in the fatigue strength of joints by the use of interference fits

Abstract

A study is made of the effect of interference fit in loaded holes on the fatigue strength of the associated part. Fatigue-test results are given for aluminium alloy fiat bars with a single hole loaded by a pin in double shear. Two series of tests were made. In one series the pin was fitted directly in the hole with various degrees of interference fit up to 0.003 in. excess diameter. The other series had a mild steel bush interposed with similar degrees of interference in the bar, but with a push fit between pin and bush. Both sets showed a great increase in fatigue strength for interference fits above a critical value. The application of these results for raising the fatigue strength of aircraft structural joints is considered.