Plastic collapse load analysis of the pipe elbows

Based on Von Mises yield condition, the plastic collapse load equations for the pipe elbows under the loads of internal pressure and torsion, and the loads of internal pressure, bending and torsion are derived. By simplified, several different plastic collapse loads such as plastic limit bending can be got. Some experiments have verified the theories. The theoretical bases have been provided to fully utilize its plastic limit capability, and a fundamental method of plastic collapse load for defected elbows is also made.