Shakedown and limit analysis of 90° pipe bends under internal pressure, cyclic in-plane bending and cyclic thermal loading

Abstract

The Linear Matching Method is used to create the shakedown limit and limit load interaction curves of 90 degree pipe bends for a range of bend factors. Two load cases are considered i) internal pressure and in-plane bending (which includes opening, closing and reversed bending) and ii) internal pressure and a cyclic through wall temperature difference giving rise to thermal stresses.The effects of the ratios of bend radius to pipe mean radius (R/r) and mean radius to wall thickness (r/t) on the limit load and shakedown behaviour are presented.

Effect of Ovality in Inlet Pigtail Pipe Bends Under Combined Internal Pressure and In-Plane Bending for Ni-Fe-Cr B407 Material

“…A long rod of length, equal to five times the bend radius (R) was attached at the free end for applying the in-plane load. Spring balance and load cell were used to measure the magnitude of the applying load which is placed at the free end of the rod [10]. Dial gauges were used to measure the deflection in the bend section by fixing it in the intrados, crown and extrados regions (Fig.…”

“…Besides shape irregularities, pipe diameter, wall thickness and bend radius also effect a change in stress in bend region [4]. However, the majority of the existing solutions have been developed either empirically based on test data or analytically based on a simple equilibrium stress field and yield criterion considering without the effect of ovality in pipe bends [5][6][7][8][9][10], thus the resulting solutions tend to under predict the actual limit loads, which lead to failure in bend region. Effect of ovality in pipe bend should be quantified and included in limit loads solution to avoid failure.…”

Cyclic Plasticity Behavior of 90° Back-to-Back Pipe Bends Under Cyclic Bending and Steady Pressure

“…Iterative elastic technique is a typical approach which contains Elastic Compensation Method [4], GLOSS R-node method [5], LMM [6], and so on. The LMM has acquired distinguished reputation of providing accurate result for many complicated geometries subjected to complex loading as well as it can consider temperature dependent material parameters [7][8][9].…”

Effect of local wall thinning on shakedown regimes of pressurized elbows subjected to cyclic in-plane and out-of-plane bending

“…Upon comparison with ASME B31.3 and EN 13480-3 design standards for occasional loading conditions, Varelis et al[11] results highlighted lack of design provisions within the low cycle fatigue range. Chen H. et al[12] generated SD domains utilizing the Linear Matching Method (LMM) for sound pressurized elbows subjected to cyclic IPO, IPC, and reversed bending modes. Cyclic through wall temperature difference of pressurized elbows was also studied to investigate the effect of thermal stresses on generated SD domains.…”

“…Cyclic through wall temperature difference of pressurized elbows was also studied to investigate the effect of thermal stresses on generated SD domains. It is reported that application of cyclic thermal load resulted in significant reduction in SD domains[12]. Wood et al[13] conducted experimental tests and FE analyses on 90 degree sound pressurized single unreinforced mitred bend subjected to cyclic IPC bending.…”