An energy based regression method to evaluate critical CTOA of pipeline steels by instrumented drop weight tear tests

摘要

An energy based regression method to estimate critical crack-tip-opening-angle (CTOAc) of high strength and toughness pipeline steels has been established derived from the Martinelli-Venzi ductile fracture model. Key curve method was applied onto the load-displacement curves of standard pressed-notch drop-wcight-tear-tcst specimens to evaluate the dynamic crack extension, providing a way to verify the correlation between the load and remaining ligament width. In the meanwhile, the material based parameter (A* σf), usually required by other CTOAc estimation algorithm, could also be determined experimentally. As a result, CTOAc of a typical high grade pipeline steel plate was acquired as a constant over steady-state stage during crack propagation, independent of specimen geometry.