The term contact fatigue broadly refers to the surface damage process that leads to pitting, wear debris formation and fatigue cracking when the surfaces of two bodies repeatedly touch each other. The relative motion between the bodies may involve global/partial slip or rolling, or a combination of these modes of contact. Usually either or both surfaces in contact may also be subjected to fluctuating stresses from vibration or other mechanical loads.

In this chapter, attention is directed at the mechanics and mechanisms of different contact fatigue phenomena. Table 13.1 provides the definitions of key terminology encountered in contact fatigue, along with examples of practical situations where such phenomena apply. These processes will be discussed in detail in various sections of this chapter.

Basic terminology and definitions

Figure 13.1 provides a general frame of reference with which the various parameters of interest in contact mechanics are defined. In this figure, adapted from Johnson (1985), two surfaces in nonconforming contact are shown whose shapes prior to contact deformation are characterized by the functions, z1(x, y) and z2(x, y). The separation between the surfaces is h(x, y) = z1 + z2. Let V1 and V2 denote the linear velocity of surfaces 1 and 2, respectively, and let Ω1 and Ω2 be their respective angular velocities. The frame of reference, centered at the instantaneous contact point O, moves with linear and angular velocities Vo and Ωo, respectively, so as to preserve its orientation to the indicated common tangent plane and the common normal at O.