Fatigue Analysis for Isolated Rocker Cover Capscrews 2002-01-0664
An engine cover isolation system consists of a number of components that interact with each other. These components include the gasket, cover, bolts and bolt isolators. The stiffness and damping of this system determines the dynamic motion of the cover. The magnitude of the cyclic bending stress that develops in the capscrew is proportional to the magnitude of the dynamic motion. If the cyclic bending stress exceeds the fatigue strength of the bolt, a fatigue failure will occur.
This paper will present an analytical model for predicting the cyclic bending stress on the outer fiber of the bolt in response to the dynamic motions that occur in an isolation system. The impact of bolt stiffness on system stiffness and on dynamic motion will be reviewed. This analytical model has been validated with experimental results and will enable the isolation system designer to avoid bolt fatigue failures.