Analysis of cyclic crack growth under rolling contact loading conditions.

摘要

The fatigue failure of components undergoing repeated contact loading, such as bearings, gears and rails often involves the propagation of cracks under complex loading paths. Additional complications are given by the frictional shear tractions which develop on the crack face, the non-linear nature of the material properties, and the presence of residual stresses.;The present work introduces a versatile finite element model which makes it possible to study subsurface, frictional Mode II cracks subjected to rolling contact loading, under general conditions of plane strain. The model may address the linear-elastic or linear-elastic-kinematic-plastic material behaviors. The influence of system geometry and type of loading on the crack driving force is also evaluated. The results of the finite element model are compared with analytical solutions for the non-zero crack face friction coefficient, and for an elastic material confirm the soundness of the model. In agreement with experimental results, the model predicts a faster propagation rate from the trailing tip. The increase in crack tip driving force due to the onset of cyclic plasticity is found to be easily related to material constants. The crack tip driving force, ;Cyclic crack propagation experiments under cyclic torque plus alternating compression are described. An alternative experimental method to determine the crack propagation rate under nominal Mode III conditions is introduced. The experimentally observed reduction in the propagation rate are qualitatively explained. The morphology of the resulting fracture surface is described, as well as its influence on the propagation rate. A new technique aimed to find an effective crack face friction coefficient is presented. The complex behavior of a Mode III shear crack under compression is qualitatively described.