Crack face friction effects on mode II stress intensities for a surface-cracked coating in two-dimensional rolling contact

This work focuses on the effects of crack free friction on Mode II stress intensity factors, K-II, for a vertical surface crack in a two-dimensional finite element model of TiN/steel subject to rolling line contact. Second-order extrapolation of K-I and K-II from nodal stresses ahead of the crack tip is found to be a more consistent technique than linear extrapolation. Results indicate that maximum K-II values, which occur when the load is adjacent to the crack, may be significantly reduced in the presence of crack face friction. The reduction is more significant for thick coatings than for thin. Crack extension and increased layer thickness result in increased K-II values. The effect of crack face friction on compressive K-I values appears negligible. Comparative results are presented for MoS2/steel and diamond-like carbon/Ti systems.