A New Material Failure Criterion for Numerical Simulation of Burst Pressure of Corrosion Defects in Pipelines

Abstract

Accurate burst pressure prediction of corroded pipelines is critical to safety design, integrity assessment and operation management. This paper evaluates five corrosion assessment methods: three flow stress-based ASME B31G, Modified B31G, and RSTRENG, and two ultimate tensile stress (UTS)-based LPC and PCORRC. The UTS-based methods were developed using the elastic-plastic finite element analyses (FEA) and an assumed material failure criterion, i.e., the Mises equivalent stress equals to the true UTS of the material. However, recent numerical investigations showed that the assumed Mises stress-based failure criterion is not valid generally, and may depend on the material hardening response. Thus the UTS-based methods may be inaccurate. In order to improve the UTS-based corrosion assessment methods, this paper investigates a general stress-based material failure criterion, and proposes a new Mises stress-based criterion that depends on the material strain hardening exponent. This new criterion is then applied to determine burst pressures of corrosion defects in the FEA simulations. With the FEA predicted burst pressures, an improved burst pressure prediction model is developed. It is shown that the proposed material failure criterion can determine more accurate burst pressures, and the improved corrosion model predicts burst pressures agreeing well with experimental data.