Mechanics of Contact Fatigue

Contact fatigue between typical machine elements such as gears, roller followers, bearings and other components involves many complex interacting features. There are the effects of geometry, mechanical properties, material properties and surface chemistry. The present discussion will center around analytical prediction techniques that are concerned only with the mechanical aspects of contact fatigue between two elements. Aspects related to the initiation of a crack under repeated loading will be discussed. The application of an approach developed by Mura, analogous to Griffith’s criterion for fracture, will be used to show how estimates of initiation life can be made and how these estimates are related to currently used ones. Once a crack has been initiated, then issues related to crack propagation become important. Some fracture mechanics based methods developed to calculate crack growth will be described along with estimates of crack propagation life.