Determination of Conditional Probability of Dynamic Axial Crack Arrest for Conventionally-Rolled, Lower-Toughness Linepipe Materials

This paper presents an analysis procedure to predict the conditional probability of dynamic ductile axial crack arrest within one pipe joint length for pipeline materials operating at temperature above the brittle-to-ductile transition temperature. These analyses assume there is an event to initiate a rupture with probability of one, so that the absolute probability of a fracture event occurring is the probability of the rupture event (i.e., from mechanical damage) times the conditional probability of arrest within one pipe joint. The underlying deterministic model centers on the Battelle Two-Curve approach with a correction to predict the arrest length given the actual material toughness relative to the minimum arrest toughness. Past full-scale experimental results were used to develop statistical parameters that were used with the deterministic model in a Monte-Carlo analysis. This model was calibrated for low-toughness (<150J) and low-grade (<X65) linepipe materials. Example cases are presented to demonstrate the variation of the conditional probability of arrest with the pipeline operating conditions.