Effect of single-period overload parameters on fatigue crack retardation for high-density polyethylene

Abstract

Nowadays, polymers have become indispensable and ubiquitous materials in many critical engineering applications. The majority of industrial polymeric components are subjected to unexpected overloads in service which may affect their lifespan. During the discontinuous slow crack growth (SCG), irreversible plastic zone is formed on the head of the crack tip. The applied overloads have a significant effect on the size of the formed plastic zone as well as the fatigue crack propagation (FCP) rate which consequently affects the failure lifetime of the component. The objective of this work is to investigate the effect of single-period overload with constant amplitude and sinusoidal waveform on the resultant FCP rate, crack band length, and the corresponding plastic zone size for High-Density Polyethylene (HDPE100). The effects of the overload ratio (OL ratio) for the first propagation crack-arrest band on the crack propagation process have been also investigated to achieve maximum retardation for crack growth and to obtain the maximum lifespan of the tested specimens. High retardation is observed at high OL ratios under constant OL position and OL number of cycles (duration). The morphology of fracture surface shows higher crack band length at high OL ratio. The crack band length represents about 80–90 % of the measured craze length.