Strength Criteria And Analytic Predictions of Failure Pressure In Line Pipes

This paper analytically investigates the failure pressure of line pipes with or without corrosion defects, and focuses on the conditions under which the classic strength criteria are appropriate for predicting failure pressure. Based on finite strain theory, a plastic collapse model is presented for end-capped defect-free pipes in a power-law hardening material. A closedform solution of the limit pressure is thus formulated as a function of the strain hardening exponent n, and an estimation of n from the T/Y ratio is developed as well. This plastic instability solution is then extended to predict the failure pressure of corroded line pipes, and is validated using detailed finite element results and the PRCI experimental database. Results show that, when n approaches 0.2 or 0, which reflects the practical limits of a high or low hardening material, the plastic instability solution is coincident with that predicted by the Tresca or von Mises criterion, respectively.