Analytical and numerical investigation of strain-hardening viscoplastic thick-walled cylinders under internal pressure by using sequential limit analysis

Plastic limit load of strain-hardening viscoplastic thick-walled cylinders subjected to internal pressure is investigated numerically and analytically in the paper. The paper applies sequential limit analysis to deal with the quasi-static problem involving hardening material properties and weakening behavior corresponding to the strain-rate sensitivity and widening deformation. By sequential limit analysis, the paper treats the plasticity problems as a sequence of limit analysis problems stated in the upper bound formulation. Rigorous upper bounds are acquired iteratively through a computational optimization procedure with the internal pressure factor as the objective function. Especially, rigorous validation was conducted by numerical and analytical studies of thick-walled cylinders in terms of the plastic limit load as well as the onset of instability. It is found that the computed limit loads are rigorous upper bounds and agree very well with the analytical solutions.