Tensile failure of filament-wound pipes under long-term creep loading: A probabilistic analysis

Creep tests exhibit wide scatter in time-to-failure results. One mean value is generally insufficient and, in order accurately to define the entire distribution, several tests are necessary. This study presents an experimental device designed to collect data on filament-wound pipes loaded in axial tension. It has been shown that experimental values can be fitted to a two-parameter log normal law or to a Weibull law. Two different methods are proposed for the evaluation of the law parameters. Both of them give similar estimates . A method is proposed for reducing the number of tests without losing the accuracy of estimators and is applied to the two-parameter (m,sigma(o)) log normal law. Two equations suffice to determine the time-to-failure distributions in their entirety. In the medium stress range (between 74% and 83% of the static strength), sigma(o) remains constant and m depends linearly on the applied stress. For lower stresses, our latest tests (72.5% of the static strength) prove the existence of a reliability area. (C) 1997 Elsevier Science Limited.