Fatigue Strength of PVC Pipes

Abstract

The strength of unplasticized polyvinyl chloride (PVC) pipes being used widely was investigated by several kinds of tests. The static strength of PVC pipes was determined in tension tests by using the dumbbell shape specimens and the ring shape specimens. In order to study the fatigue strength of PVC pipes, flexural fatigue tests by plane bending for the dumbbell shape specimens taken from the pipe and pulsating internal pressure tests for PVC pipes were carried out at different temperatures in the range of 5°C to 50°C. An apparatus has been designed and constructed which allows the determination of the strength of circumferential direction of the pipe subjected to internal pressure. The experiments showed that the static strength in the circumferential direction of PVC pipes was about 90% of that in the longitudinal direction. On the other hand, the fatigue strength in the circumferential direction determined by the pulsating internal pressure test for PVC pipes was much less than that in the longitudinal direction by the plane bending test for the dumbbell shape specimen. The experimental results mentioned above were discussed in terms of the effects of temperature and strain rate on the yield stress of PVC. The results were also used to construct the critical curves of fatigue strength for PVC pipes subjected to pulsating internal pressure in a wide temperature.