Predicting the Fracture Initiation Transition Temperature in High Toughness, Low Transition Temperature Line Pipe With the COD Test

Abstract

This paper describes the use of the crack opening displacement (COD) test to predict the fracture initiation transition temperature of high toughness, low-transition temperature in line pipe. A series of COD tests using t × t and t × 2t specimens made from this line pipe material. The COD test was conducted over a range of temperatures and the point where the upper shelf COD values began to decrease with decreasing temperature was defined. To verify the full-scale significance of this temperature, a series of three experiments was conducted on 48-in. (1.22m) dia line pipe to bracket the transition temperature defined in the COD Test. The results suggest that the COD transition temperature can ve used to define the fracture initiation temperature for static loading in pipe. In addition, in the transition temperature region, the full-scale results, while limited in number, suggest that the COD values could possibly be used to predict the critical flaw sizes in the pipe material.