Fatigue fracture behavior of solid-state extruded high-density polyethylene

High-density polyethylene (HDPE) specimens for fatigue experiments were prepared by solid-state extrusion. Variations of dynamic viscoelasticity and surface temperature of the specimen were measured under cyclic fatigue. Fatigue behavior of extruded HDPE showed characteristic features depending on the type of cyclic fatigue. In the case of the fatigue test including compression deformation, extruded HDPE fatigue-fractured via the formation of a kink-band along the maximum shear stress direction. On the other hand, in the case of the pure tension fatigue test, the fatigue fracture surface generated in the normal direction of cyclic straining. The total hysteresis loss energy is divided into the two parts: The energy consumed to fracture the specimen and the energy dissipated as heat under cyclic fatigue. A fatigue fracture criterion based on the magnitude of the hysteresis loss energy consumed for a structural change was established. The fatigue strength of extruded HDPE estimated on the basis of this criterion was high in the cases of pure tension and pure compression fatigue tests, and also, was low in that of the tension-compression fatigue test.