Type 1 energy analysis for the creep of smooth circular pipe bends under combined in-plane bending and internal pressure

Abstract

Many pipeline systems, in addition to catering for thermal expansion conditions, have to carry internal pressure loading. An approximate theoretical analysis is given for the pure creep of a smooth curved pipe bend under fixed ratios of combined pressure and in-plane bending. The bend is circular in cross-section and of constant thickness. An energy method designated type 1, coupled with a simple n-power constitutive relationship, is used and implemented by direct minimization techniques.

Selected deformation and stress results are presented as possible design factors for a number of the geometric and material parameters. For part of the geometric spectrum, large displacement effects are significant and lead to non-steady creep behaviour. Consequently there is not a direct analogy with elasticity, although linear elastic results can nevertheless be identified. Other special cases of loading or geometry are reducible from the general case.