Development of an alternative failure criterion for residual strength of corrosion defects in moderate- to high-toughness pipe. Final report

Under sponsorship of the Line Pipe Research Supervisory Committee of PRC International, Battelle has conducted ongoing research on the fundamental mechanisms driving failure of pipeline corrosion defects. This phase of the research investigation has resulted in a simplified, closed-form failure criterion for blunt corrosion, known as PCORRC. This report summarizes the key elements of recent research including: (1) development of a PC-software computational model, known as PCORR, for predicting the remaining strength of the class of corrosion defects that fail by ductile plastic-collapse under internal pressure loading; (2) a comparative evaluation of the material and defect geometry variables that control the remaining strength of blunt corrosion defects in moderate- to high-toughness pipe materials; (3) development of the simplified failure criterion, PCORRC, for predicting the remaining strength of blunt corrosion defects in moderate- to high-toughness pipe materials. The results of this investigation indicate that corrosion defects may fail by one of two potential failure mechanisms. The first is a ductile plastic collapse mechanism in which failure is controlled by the material`s ultimate tensile strength. The second is a fracture-based mechanism in which cracks may nucleate, grow, and coalesce at the base of the corrosion defect.