Elasto-plastic state of thick-wall convoluted elements subject to internal pressure

According to current available literature data, there is no solution for the elasto-plastic problem of convoluted piping elements (elbows, branch pipes) subject to internal pressure. A solution with several assumptions is proposed for this problem. Let us examine a thick-wall convoluted piping element as a part of a closed thick-wall toroidal shell in which only normal stresses develop under an internal pressure. We will assume that the convoluted element is fabricated from an ideally plastic incompressible material conforming to the Huber–Mises plasticity condition [1]: