Determination of collapse moment of different angled pipe bends with initial geometric imperfection subjected to in-plane bending moments

Abstract

From the recent literature, it is revealed that pipe bend geometry deviates from the circular cross-section due to pipe bending process for any bend angle, and this deviation in the cross-section is defined as the initial geometric imperfection. This paper focuses on the determination of collapse moment of different angled pipe bends incorporated with initial geometric imperfection subjected to in-plane closing and opening bending moments. The three-dimensional finite element analysis is accounted for geometric as well as material nonlinearities. Python scripting is implemented for modeling the pipe bends with initial geometry imperfection. The twice-elastic-slope method is adopted to determine the collapse moments. From the results, it is observed that initial imperfection has significant impact on the collapse moment of pipe bends. It can be concluded that the effect of initial imperfection decreases with the decrease in bend angle from 150∘ to 45∘. Based on the finite element results, a simple collapse moment equation is proposed to predict the collapse moment for more accurate cross-section of the different angled pipe bends.

Development of an improved structural integrity assessment correlation for circumferential through-wall cracked 90° shape-distorted pipe bends subjected to in-plane opening bending moment

“…28,29 The material considered was Type 304 SS, generally used in the piping system, with a 0.26 Poisson's ratio (γ), yield stress (σ o ) of 271.93 MPa, and Young's modulus (E) of 193 GPa. 17,18,26,28 For the present analysis, the elasticperfectly plastic (EPP) material model was used, which offers a conservative estimation of the FE results and thus is useful from the standpoint of the pipe bend's design. 28…”

“…22–24 The circumferential crack ( 2 θ) at the intrados was taken as 0°, 45°, 60°, and 90° for which the corresponding relative crack lengths ( θ/π) were 0, 0.125, 0.167, and 0.25, respectively. 28,29 The material considered was Type 304 SS, generally used in the piping system, with a 0.26 Poisson's ratio 0.25em false( γ false), yield stress ( σ o false) of 271.93 MPa, and Young's modulus ( E ) of 193 GPa. 17,18,26,28 For the present analysis, the elastic-perfectly plastic (EPP) material model was used, which offers a conservative estimation of the FE results and thus is useful from the standpoint of the pipe bend's design.…”

“…17,18,26,28 For the present analysis, the elastic-perfectly plastic (EPP) material model was used, which offers a conservative estimation of the FE results and thus is useful from the standpoint of the pipe bend's design. 28…”

Evaluation of collapse moment of pressurized 30°–180° bend pipes subjected to out-of-plane bending moment

“…Also, it is necessary to note that most of the research refers to 90° pipe bends, whereas the pipe bends of different angle are not emphasized under combined loading of internal pressure and bending moment. Recently, present authors (Kumar et al 24 ) reported the outcomes of study on determination of collapse moment of pipe bend of different angles incorporated with initial imperfection under in-plane closing and opening bending moments for unpressurized condition and observed that initial imperfect has significant effect. The pipe bends are subjected to out-of-plane bending moments in many situations, for example, some external connections or attachments of pipe features, live load during maintenance, and repair works.…”