Abstract
In this article, an automated method for prediction of the long-term (creep rupture) behavior of multilayer pipes under hydrostatic pressure is presented. For long-term extrapolation, a combined quadratic and linear regression analysis is used. This procedure is automated in the pipe software called automated design and analysis of pipes (ADAP) for design and analysis of pipelines. Two examples showing this procedure using the software ADAP are presented and the results are compared with the existing international standards. Through this study, a new automated procedure for the extrapolation of the long-term hydrostatic strength of thermoplastic and fiber reinforced pipes is presented. Hence the arbitrary action of defining a sharp knee becomes redundant. Moreover, instead of a computational but physically non-plausible sharp knee, a transition zone between the ductile and the brittle behavior at a higher temperature is obtained. This automated method and the inherent novel features may be of use in the revisions of the existing international standards. The proposed method can be used for the prediction of the long-term internal hydrostatic behavior of thermoplastics pipes, glass fiber reinforced laminate pipes, and multilayer plastics pipes.