Fracture mechanics approach to the fretting fatigue strength of axle assemblies

The objective of the present paper is to evaluate the fatigue crack growth behavior in press-fitted axles using a fracture mechanics approach and to predict the fatigue strength regarding crack propagation (sigma(w2)). The relationship between nominal bending stress (sigma(n)) and non-propagating crack length in press-fitted axles is also discussed. Rotating bending fatigue tests were conducted on the induction hardened and quench-tempered axles of 38 and 40 mm in diameter. The equation for Delta K was formulated from the result of FEM analyses in which the micro-profile at the contact edge was taken into consideration. The threshold stress intensity factor range Delta K-th for small cracks was estimated from the crack size measured after the fatigue tests by using a modified stress ratio effect at fully compressed stress reversals due to high compression residual stress, sigma(w2) and the relationship between sigma(n) and non-propagating crack length were predicted by using the above mentioned Delta K and Delta K-th. The predicted sigma(w2) and non-propagating crack length were in good agreement with the experimental values.