Studies on ratcheting behaviour of pressurised pipes and elbows
Ratcheting studies were carried out on SA 312 Type 304LN stainless steel straight pipes (8Nos.) and elbows (4 Nos.) subjected to steady internal pressure and cyclic bending load. The internal pressure for all the straight pipes was ranging from 25 MPa to 45 MPa and in the case of elbows the internal pressure was varied for different elbows, ranging from 27.6 MPa to 39.2 MPa. Cyclic bending load was applied on the specimens by subjecting them to different levels of load-line displacement. The straight pipes failed either by occurrence of through-wall crack accompanied by simultaneous ballooning, or bursting with simultaneous ballooning. All the elbows failed by occurrence of through-wall crack accompanied by simultaneous ballooning. Ratcheting behaviour of straight pipes and elbows were compared and it was generally inferred that ratcheting was more pronounced in straight pipes than in elbows
