PSI - Issue 41

Irina Goryacheva et al. / Procedia Structural Integrity 41 (2022) 220–231 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

227

8

5. Analysis of damage accumulation and wear kinetics The accumulated damage function and its evolution during the process of the fracture of subsurface layers of the material were calculated using the relations (12) and (13). In addition to the parameters that affect the stress state of the contacting bodies under the conditions of sliding and rolling friction mentioned in Section 4, the strength characteristics of the material (coefficient c and exponent m in (10)) influence the fatigue damage accumulation. In calculations the dimensionless damage value / * Q Q , which depends only on the parameter m , is used: ( ) ( ) ( ) max 0 * * ma * * x , ( , ) m z Q z N Q z N N Q N Q z        +   =    (16) So, for * N N  the surface or subsurface fracture (delamination) occurs if the value of the right-hand side of Eq. (16) reaches 1. For study of fatigue damage accumulation and wear, a numerical analysis of the damage function (16) was carried out. In Fig. 4 the evolution of the damage function (curves 1-6) in sliding contact is presented, where each curve corresponds to a number of cycles passed until the damage function reaches the critical value at the surface ( 0) z = or under the surface ( 0 z  ) of the elastic half-space.

Fig. 4 . Accumulated damage for sliding contact, sliding friction coefficient μ = 0.2 and m = 4.8

After the first case of subsurface fracture (curve 1), the damage function is a monotonically decreasing function with a maximum on the surface (curves 2 and 3). Then, with an increase in the number of cycles, there is an inflection of the function curve and the next act of subsurface fracture occurs (curve 4). After that, the damage function again takes the form of a monotonically decreasing (with the depth) function corresponding to surface wear (curves 5 and 6).

5.1. Sliding contact

In sliding contact the effect of the sliding friction coefficient  and the strength properties of the material, describing by the parameter m in Eq. (16), on the damage accumulation in the elastic half-space, i.e. the function * ( , ) / Q z N Q (16), is studied. Damage functions for different number of cycles (Fig. 5 a ) and the kinetics of wear (Fig. 5 b ) in the sliding contact for sliding friction coefficient µ = 0.2 and different values of parameter m are shown in Fig. 5.