Experimental study on the stability of circumferentially through-wall cracked piping against an unstable fracture

The onset of an unstable ductile fracture in a piping system is dependent on the compliance and supporting conditions of the loading system as well as the material properties. This paper firstly discusses the influence of the compliance and pipe support on the onset of an unstable fracture under bending load. Based on the bending test results of 6-inch and 12-inch diameter SUS304 pipes with a through-wall crack in the circumferential direction, an empirical expression which represents the critical instability condition of compliance and piping support is derived. Using the above expression, case studies are performed on the critical support span length for simply supported 3-point bending pipes of 3-, 6-, 12- and 24-inch diameters. The calculated results show that the critical span length increases with the increase of pipe diameter and initial crack angle. (author)