Fracture Toughness Measurement by Using Pipe-ring Specimens

Abstract

Fracture toughness Measurement of thin walled pipe-line with flaw or defect in most critical axial direction is difficult. In this paper the non-standard modified specimens has been proposed for simple fracture testing. The comparison between fracture behaviour of single edge notch bending (SENB), compact tension (CT) and pipe-ring specimens with notch and fatigue pre-crack were analysed. In order to determine CTOD-R curve the normalization method by using remote measurement CMOD has been used for all specimens. For non-standard pipe ring pre-cracked specimens the plastic correction eta factor is determined by using finite element method. The stable crack growth initiation was determined also as a crack tip surface strain-relaxation by using stereo-optical grading method. Comparison between CTOD-R curves of all three types of specimens shows quite similar fracture toughness in stable crack initiation range.