Fatigue Damage Progression in Plastics During Cyclic Ball Indentation‪.‬

Abstract AE (acoustic emission) is utilized to monitor the progression of sub-surface damage in a transparent PVC (poly-vinyl-chloride) plate subjected to contact fatigue by cyclic ball indentation. We monitored AEs from sub-surface damage by four small AE sensors mounted on the four edges of a square plate, and estimated both the source location and fracture mode. The AE analysis revealed that Mode-II lateral cracks initiated at cycle number, N = 8.9 x [10.sup.4]. AE sources of corresponding events were located in front of progressing sub-surface lateral cracks at the depth of 516 [micro]m. We could not, however, monitor AE from Mode-I radial crack possibly due to small crack opening. Finite element method (FEM) predicted lateral crack initiation at approximately 500 [micro]m below the surface with the maximum shear stress.