Lower bound to plastic load of cylinders with opening under combined loading

This paper proposes an analytical solution to obtain the lower bound limit load of cylindrical shells with circular opening under the action of combined axial force and bending moment at ends. The yield criterion proposed by Ivanov for plastic analysis of shells employing Von Mises criteria is used for general cylindrical shells. The method of solution is based on formulating the lower bound to limit load as a nonlinear mathematical programming problem. In this analysis Feasible Sequential Quadratic Programming (FSQP) is employed as an optimization technique to obtain the lower bound limit load. The lower bound results are presented in dimensionless form for a wide range of loading cases and geometric parameters of practical interest and compared with finite element elastic–plastic results which are found to be in good agreement.