Crack Propagation in Rolling Line Contacts

Abstract

The stress intensity factors for short straight and branched subsurface cracks subjected to a Hertzian loading are calculated by the finite element method. The effect of crack face friction on stress intensity factors is considered for both straight and branched cracks. The calculations show that the straight crack is subjected to pure mode II loading, whereas the branched crack is subjected to both mode I and mode II, with ΔKI/ΔKII < 0.25. Although KI is small, it strongly influences KII by keeping the branched crack faces apart. Based on the ΔKII values and Paris’s crack growth model, the number of stress reversals required to grow a crack in a rolling component from an initial threshold length to the final spalling length was estimated. It was found that the crack propagation period is small compared with the expected bearing fatigue life. Therefore, crack propagation is not the rate controlling factor in the fatigue failure of bearings operating under normal loading levels.

A NEW METHOD FOR THE MEASUREMENT OF MODE II FATIGUE THRESHOLD STRESS INTENSITY FACTOR RANGE ΔKτth

“…As has been pointed out [2,6,7,15], the frictional force acting on the crack faces resists mode I1 sliding and decreases the effective mode I1 stress intensity factor range at the crack tip. In order to investigate the effect of friction, a test was carried out using a lubricant on the crack surface.…”

A numerical approach to subsurface crack propagation assessment in rolling contact

“…Most of the propagation phase usually occurs along a path parallel to the contact surface, as many evidences show, until cracks deviate towards the surface causing material removal and final failure 1,4,5,10–13 . As several studies show, 5,14–16 this phase of propagation occurs in mode II, given the triaxial compressive stress state (in particular the component parallel to the crack path), that inhibits crack opening displacements (CODs), crack kinking and mode I propagation.…”

A mode II weight function for subsurface cracks in a two‐dimensional half‐space

“…2. The procedure to derive the K II from the displacement field resulting by the FEM analysis near the crack tip can be found in the literature 10 . The resulting coefficients are reported in Table 1.…”

“…The procedure to derive the K II from the displacement field resulting by the FEM analysis near the crack tip can be found in the literature. 10 The resulting coefficients are reported in Table 1. The chosen crack depths are representative of the region where the most common phenomena of rolling contact fatigue are experimentally observed.…”

“…4±6 Particular attention has been focused on the problem of short cracks starting from inclusions, which, as is known, have a substantially different behaviour from long cracks. 6±8 In all these approaches a central problem is represented by the calculation of the applied Stress Intensity Factor (SIF) at the crack tip: different methods have been proposed in the literature, such as the Body Forces Method, 9 the Finite Elements Method (FEM), 10 the Boundary Elements Method, 11 the Weight Functions (WF) method, 12 and others. The Finite Elements Method is the most commonly used, because it is reliable and the computing programs necessary to its application are widely diffused.…”