Structural effect in the creep behavior of thermoplastic pressure pipes at high temperature - role of geometrical defects

摘要

Failure mechanisms such as local cavitation observed in crystalline thermoplastics pipes submitted to low constant pressure are likely to be induced by microstructure heterogeneity and time-dependent macroscopic stress fields. This study on poly(vinylidene) fluoride (PVDF) focuses on the latter, simulating the long-term creep behavior of homogeneous viscous pipes with finite-element calculations. Stress and strain distributions are evaluated just after loading and their evolution with time is considered. The hydrostatic stress is analyzed in relation to the onset of cavitation. The detrimental consequences of thickness defects due to extrusion on the onset of cavitation are also established.