Life prediction of titanium and aluminum alloys under fretting fatigue conditions using various crack propagation criteria. Part 1. Experimental and calculation techniques

Using the analysis of state-of-the-art techniques of fretting fatigue studies and results of description of multi-stage fatigue crack propagation in fretting zone within fracture mechanics framework, we have refined the calculation-and-experimental technique earlier proposed by the author. This technique allows one to predict current values of the angle and rate of inclined crack propagation in the subsurface layers of material under fretting conditions using calculated stress intensity factors KI and KII for contact and bulk loads, as well as experimental crack resistance diagrams by KI and/or KII types. We have performed comparative analysis of various techniques for construction of crack resistance diagrams by KI and KII types and obtained the results for AMg6N and Al 7075-T6 aluminum alloys and VT9 titanium alloy. It is shown that the initial stage of crack propagation in the above alloys can occur in the maximal shear stress plane by shear mechanism or in the maximal tensile stress plane by cleavage mechanism according to the Otsuka two-parameter criterion or to the Richard empirical criterion.