Influence of Tightening Bolts into a Plastic Region on the Fatigue Strength of the Cap Bolt of a Connecting Rod

Abstract

In order to examine the effects of tightening bolts into a plastic region on fatigue strength, close-to-practice tests on the fatigue performance and the dynamic loseness were conducted or the cap bolt of a connecting rod used (actually) in a diesel engine. The fatigue strength of a bolt tightened by the present method has been found to be better than that of the conventional elastic-controlled method. The residual axial tension of bolts tightened by the present method was still superior to that of bolts tightened by the other method. The fractographic examination using SEM showed that the fatigue crack of bolts tightened with the present method was initiated and propagated under a smaller cyclic plastic deformation than that tightened with the elastic method.