Combined effect of shape distortion and bend angle on collapse load of pipe bends under in-plane closing bending moment and internal pressure

Abstract

Purpose The purpose of this paper is to quantify the combined effect of shape distortion and bend angle on the collapse loads of pipe bends exposed to internal pressure and in-plane closing bending moment. Non-linear finite element analysis with large displacement theory was performed considering the pipe bend material to be elastic perfectly plastic. Design/methodology/approach One half of the pipe bend model was built in ABAQUS. Shape distortion, namely, ovality (Co) and thinning (Ct), were each varied from 0% to 20% in steps of 5% and bend angle was varied from 30° to 180° in steps of 30°. Findings The findings show that ovality has a significant impact on collapse load. The effect of ovality decreases with an increase in bend angle for small thickness. The opposite effect was observed for large thickness pipe bends. The influence of ovality was more for higher bend angles. Ovality impact was almost negligible at certain internal pressure denoted as nullifying point (NP). The latter increased with an increase in pipe bend thickness and decreased with increase in pipe bend radius. For small bend angles one NP was observed where ovality impact is negligible and beyond this point the ovality effect increased. Two NPs were observed for large bend angles and ovality effect was maximum between the two NPs. Thinning yielded a minimal effect on collapse load except for small bend angles and bend radii. The influence of internal pressure on thinning was also negligible. Originality/value Influence of shape distortions and bend angle on collapse load of pipe bend exposed to internal pressure and in-plane closing bending has been not revealed in existing literature.

Investigation on structural integrity of shape distorted 90° back-to-back pipe bends under in-plane closing bending moment

“…For the current investigation, stainless steel (type 304) was used, and the properties of this material are as follows: Poisson's ratio ( μ ) = 0.26, Young's modulus ( E ) = 193 GPa and Yield stress ( σ °) = 271.93 MPa (Krishna et al. , 2020; Silambarasan et al. , 2021b).…”

Determination of bend angle and shape imperfection effect on collapse load of pipe bends under in-plane opening moment

“…28 The magnitude of shape distortion can be calculated through the contour of the pipe bend's cross-section captured by the first off-trail test using equations (1) to (3). 27,29–35 To incorporate shape imperfection at the mid-section of pipe bends for building the FE geometry model, has been speculated as shown below. The mid-portion (A–A 1 ) of the pipe bend is presumed to be a perfect elliptical shape if ovality is present.…”

“…Li et al 26 investigated the limit load for pipe bend with different bend angles subjected to IP, in-plane and out-of-plane bending moments and torsion moments. Silambarasan et al 27 examined the influence of bend angle and shape imperfection on collapse load for IPCM imposed pipe bends and proposed a mathematical solution to predict the combined effect of bend angle and shape imperfection. The most crucial factor is the determination of the effect of IPOM in pipe bends with shape imperfections.…”

Development of an improved limit pressure equation for structurally distorted thin-walled pressurized 90 degree pipe bends

“…To consolidate irregularities in pipe bends, the following are derived from Figure 3 (Vinothkumar et al , 2022; Krishna et al , 2021; Silambarasan et al , 2021a): …”

“…Ovality had a remarkable effect, and thinning produced effects for ovality up to 5% in large strain formulation. Silambarasan et al (2021aSilambarasan et al ( , 2021b quantified the influences of bend angle and structural distortions and with the inclusion of internal pressure on the plastic collapse load (PCL) of bend portion of pipe exposed to IPCB moment and proposed the empirical solutions. Krishna et al (2021) investigated the elastic stresses for structurally deformed 90°v ery thin-walled pipe bends under IPCB and reported the mathematical expressions.…”