Evaluation of Time to Ductile Failure in Creep of PEs from Short-term Testing

摘要

Ductile failure of PE pipe in sustained pressure test results from instability of steady creep process. The instability is manifested in formation of localized necking, which appears in form of ballooning under internal pressure. The condition of instability of the steady creep is an unbounded increase of the strain rate: ε → ∞. A strain rate ～ stress relation combined with basic stability analysis leads to simple relation between the applied stress and the creep time prior to PE pipe ductile failure. A simple method of evaluation of PE steady creep behavior from short-term ramp tests data is proposed in this work. It opens a new and straightforward approach to screening a large number of material formulations and therefore to connecting molecular architecture with material durability.