Plastic Limit Load of Elbows with Local Thinned Area under Combined Internal Pressure and In-Plane Closing Bending Moment

Plastic limit load of elbows with local thinned area （LTA） under combined internal pressure and in-plane closing bending moment has been studied by finite element analysis （FEA） and experiments. The results of FEA and experiments show that,with different LTA, the variation of the limit load of elbows to the internal pressure is different. When a/b≤0.313, the limit moment of elbows always decreases with the increasing of the internal pressure. When a/b＞0.313, the limit moment of elbows increases with the increasing of the internal pressure and then decreases with the increasing of the internal pressure. By fitting the results of FEA, the safety assessment figure for elbows under combined internal pressure and in-plane closing bending moment is drawn. The safety assessment method using this figure is applicable for the engineer problems.