Residual stress variations during rolling contact fatigue of refrigerant lubricated silicon nitride bearing elements

The residual stress field of rolling contact silicon nitride bearing elements with refrigerant lubrication was studied. Residual stress measurements were performed using X-ray method. Rolling contact fatigue tests were performed at various Hertz contact stresses using a modified four ball machine coupled with a pressurised chamber. Residual stress value of −242 MPa measured at 0.1 millions stress cycles and −60 MPa at 5.6 millions stress cycles shows an inverse relationship between residual stresses and rolling contact fatigue cycles. These results are helpful in predicting rolling contact fatigue life. Residual stress measurements were also performed on the contact path at various distances from the induced ring crack. The residual stress field analysis shows that residual stresses are relieved due to sub-surface damage. Maximum contact stresses at the edges of the contact path due to Hertz contact stress causing a weaker residual stress field at the sub-surface crack front.