Shakedown and limit load of pipe bends with local wall thinning under combined internal pressure and cyclic in-plane bending moment

Abstract

The behaviour of smooth 90-degree pipe bends under combined internal pressure and cyclic bending loads has received a substantial attention in recent few years where shakedown and ratcheting boundaries have been determined. However such data are scarcely found for those pipe bends suffering from local wall thinning. This paper quantifies the effect of local wall thinning parameters on both elastic and shakedown boundaries via a non cyclic-numerical technique developed by Abdalla et al. [1]. The effect of local wall thinning parameters is investigated also on limit loads of pipe bends under the internal pressure and bending moments based on a systematic FE limit loads using elastic perfect plastic material model. The limit load study has been verified with the proposed approximations developed by Oh et al. [2] and Kim et al. [3]. The thinning geometry is assumed to be rectangular rather than circular but the geometrical nonlinearities are considered. Finite and fully circumferential local wall thinning in pipe bends under combined internal pressure and in-plane bending; opening and closing have been studied. Both extrados and intrados local wall thinning locations have been considered also.