Effect of structural deformations and bend angle on the collapse load of pipe bends subjected to in-plane closing bending moment

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Silambarasan R. ◽  
Veerappan A.R. ◽  
Shanmugam S.
Keyword(s):  
Plastic Material ◽  
Large Strain ◽  
Bending Moment ◽  
Bend Angle ◽  
Plastic Collapse ◽  
Collapse Load ◽  
Pipe Bend ◽  
Content Type ◽  
Structural Deformations ◽  
Bend Angles

Purpose The purpose of this study is to investigate the effect of structural deformations and bend angle on plastic collapse load of pipe bends under an in-plane closing bending moment (IPCM). A large strain formulation of three-dimensional non-linear finite element analysis was performed using an elastic perfectly plastic material. A unified mathematical solution was proposed to estimate the collapse load of pipe bends subjected to IPCM for the considered range of bend characteristics. Design/methodology/approach ABAQUS was used to create one half of the pipe bend model due to its symmetry on the longitudinal axis. Structural deformations, i.e. ovality (Co) and thinning (Ct) varied from 0% to 20% in 5% steps while the bend angle (ø) varied from 30° to 180° in steps of 30°. Findings The plastic collapse load decreases as the bend angle increase for all pipe bend models. A remarkable effect on the collapse load was observed for bend angles between 30° and 120° beyond which a decline was noticed. Ovality had a significant effect on the collapse load with this effect decreasing as the bend angle increased. The combined effect of thinning and bend angle was minimal for the considered models and the maximum per cent variation in collapse load was 5.76% for small bend angles and bend radius pipe bends and less than 2% for other cases. Originality/value The effect of structural deformations and bend angle on collapse load of pipe bends exposed to IPCM has been not studied in the existing literature.

Effect of Bend Angle on Gross Plastic Deformation of Pipe Bends: A Finite Element Based Study

2015 ◽  
Author(s):  
Anindya Bhattacharya ◽  
Sachin Bapat ◽  
Hardik Patel ◽  
Shailan Patel
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Failure Mechanisms ◽  
Bending Moment ◽  
Bend Angle ◽  
Piping System ◽  
Plastic Collapse ◽  
Collapse Load ◽  
Pipe Bend ◽  
Bend Angles

Bends are an integral part of a piping system. Because of the ability to ovalize and warp they offer more flexibility when compared to straight pipes. Piping Code ASME B31.3 [1] provides flexibility factors and stress intensification factors for the pipe bends. Like any other piping component, one of the failure mechanisms of a pipe bend is gross plastic deformation. In this paper, plastic collapse load of pipe bends have been analyzed for various bend parameters (bend parameter = tRbrm2) under internal pressure and in-plane bending moment for various bend angles using both small and large deformation theories. FE code ABAQUS version 6.9EF-1 has been used for the analyses.

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

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
R. Silambarasan ◽  
V.R. Veerappan ◽  
S. Shanmugam
Keyword(s):  
Internal Pressure ◽  
Bending Moment ◽  
Combined Effect ◽  
Bend Angle ◽  
Collapse Load ◽  
Shape Distortion ◽  
Element Analysis ◽  
Pipe Bend ◽  
Content Type ◽  
Bend Angles

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.

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

2021 ◽  
pp. 095440622110614
Author(s):  
Manish Kumar ◽  
Pronab Roy ◽  
Kallol Khan
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Plastic Material ◽  
Bending Moment ◽  
Bend Angle ◽  
Pipe Bend ◽  
Geometric Imperfection ◽  
Initial Geometric Imperfection ◽  
Out Of Plane ◽  
Plane Bending

The present paper determines collapse moments of pressurized 30°–180° pipe bends incorporated with initial geometric imperfection under out-of-plane bending moment. Extensive finite element analyses are carried out considering material as well as geometric nonlinearity. The twice-elastic-slope method is used to determine collapse moment. The results show that initial imperfection produces significant change in collapse moment for unpressurized pipe bends and pipe bends applied to higher internal pressure. The application of internal pressure produces stiffening effect to pipe bends which increases collapse moment up to a certain limit and with further increase in pressure, collapse moment decreases. The bend angle effect on collapse moment reduces with the increase in internal pressure and bend radius. Based on finite element results, collapse moment equations are formed as a function of the pipe bend geometry parameters, initial geometric imperfection, bend angle, and internal pressure for elastic-perfectly plastic material models.

Effect of Bend Angle on Gross Plastic Deformation of Pipe Bends for Out-of-Plane Bending: A Study Using Plastic Work Curvature Method

2016 ◽  
Author(s):  
Anindya Bhattacharya ◽  
Sachin Bapat ◽  
Hardik Patel ◽  
Shailan Patel ◽  
Michael P. Cross
Keyword(s):  
Plastic Deformation ◽  
Internal Pressure ◽  
Bending Moment ◽  
Plastic Work ◽  
Bend Angle ◽  
Piping System ◽  
Plastic Collapse ◽  
Pipe Bend ◽  
Out Of Plane ◽  
Plane Bending

Bends are an integral part of a piping system. Because of the ability to ovalize and warp they offer more flexibility when compared to straight pipes. Piping Code ASME B31.3 [1] provides flexibility factors and stress intensification factors for pipe bends. Like any other piping component, one of the failure mechanisms of a pipe bend is gross plastic deformation. In this paper, plastic collapse load of pipe bends have been analyzed for various bend parameters (bend parameter = tRbrm2) under internal pressure and out-of-plane bending moment for various bend angles using both small and large deformation theories. FE code ABAQUS version 6.9EF-1 has been used for the analyses. The goal of the paper is to develop an expression for plastic collapse moment for a bend using plastic work curvature method when the bend is subjected to out-of-plane bending moment and internal pressure as a function of bend angle and bend parameter.

Gross Plastic Deformation of Pipe Bends Under Internal Pressure and In- and Out-of-Plane Bending: A Study on the Sensitivity of the Finite Element Models

2014 ◽  
Author(s):  
Anindya Bhattacharya ◽  
Sachin M. Bapat
Keyword(s):  
Plastic Deformation ◽  
Internal Pressure ◽  
Real Life ◽  
Bending Moment ◽  
Piping System ◽  
Plastic Collapse ◽  
Collapse Load ◽  
Pipe Bend ◽  
Out Of Plane ◽  
Plane Bending

Bends are an integral part of a piping system. Because of the ability to ovalize and warp they offer more flexibility when compared to straight pipes. Piping Code ASME B31.3 [1] provides flexibility factors and stress intensification factors for the pipe bends. Like any other piping component, one of the failure mechanisms of a pipe bend is gross plastic deformation. In this paper, plastic collapse load of pipe bends have been analyzed for various D/t ratios (Where D is pipe outside diameter and t is pipe wall thickness) for internal pressure and in-plane bending moment, internal pressure and out-of-plane bending moment and internal pressure and a combination of in and out-of-plane bending moments under varying ratios. Any real life component will have imperfections and the sensitivity of the models have been investigated by incorporating imperfections as scaled eigenvectors of linear bifurcation buckling analyses. The sensitivity of the models to varying parameters of Riks analysis (an arc length based method) and use of dynamic stabilization using viscous damping forces have also been investigated. Importance of defining plastic collapse load has also been discussed. FE code ABAQUS version 6.9EF-1 has been used for the analyses.

Investigation of Smooth Pipe Bends Under the Effect of In-Plane Bending

2017 ◽  
Author(s):  
Diana Abdulhameed ◽  
Michael Martens ◽  
J. J. Roger Cheng ◽  
Samer Adeeb
Keyword(s):  
High Stress ◽  
Circular Cross Section ◽  
Bending Moment ◽  
Bend Angle ◽  
Bending Moments ◽  
Bend Radius ◽  
Pipe Bend ◽  
Cross Sectional ◽  
Smooth Pipe ◽  
Plane Bending

Pipe bends are frequently used to change the direction in pipeline systems and they are considered one of the critical components as well. Bending moments acting on the pipe bends result from the surrounding environment, such as thermal expansions, soil deformations, and external loads. As a result of these bending moments, the initially circular cross-section of the pipe bend deforms into an oval shape. This consequently changes the pipe bend’s flexibility leading to higher stresses compared to straight pipes. Past studies considered the case of a closing in-plane bending moment on 90-degree pipe bends and proposed factors that account for the increased flexibility and high-stress levels. These factors are currently presented in the design codes and known as the flexibility and stress intensification factors (SIF). This paper covers the behaviour of an initially circular cross-sectional smooth pipe bend of uniform thickness subjected to in-plane opening/closing bending moment. ABAQUS FEA software is used in this study to model pipe bends with different nominal pipe sizes, bend angles, and various bend radius to cross-sectional pipe radius ratios. A comparison between the CSA-Z662 code and the FEA results is conducted to investigate the applicability of the currently used SIF factor presented in the design code for different loading cases. The study showed that the in-plane bending moment direction acting on the pipe has a significant effect on the stress distribution and the flexibility of the pipe bend. The variation of bend angle and bend radius showed that it affects the maximum stress drastically and should be considered as a parameter in the flexibility and SIF factors. Moreover, the CSA results are found to be un-conservative in some cases depending on the bend angle and direction of the applied bending moment.

Validity of Assessment Procedure in p-M Method for Multiple Volumetric Flaws

2008 ◽  
Author(s):  
Shinji Konosu ◽  
Masato Kano ◽  
Norihiko Mukaimachi ◽  
Shinichiro Kanamaru
Keyword(s):  
Internal Pressure ◽  
Yield Stress ◽  
Bending Moment ◽  
Pressure Vessels ◽  
Assessment Procedure ◽  
Plastic Collapse ◽  
Storage Tanks ◽  
Collapse Load ◽  
The Status ◽  
Single Flaw

General components such as pressure vessels, piping, storage tanks and so on are designed in accordance with the construction codes based on the assumption that there are no flaws in such components. There are, however, numerous instances in which in-service single or multiple volumetric flaws (local thin areas; volumetric flaws) are found in the equipment concerned. Therefore, it is necessary to establish a Fitness for Service (FFS) rule, which is capable of judging these flaws. The procedure for a single flaw or multiple flaws has recently been proposed by Konosu for assessing the flaws in the p–M (pressure-moment) Diagram, which is an easy way to visualize the status of the component with flaws simultaneously subjected to internal pressure, p and external bending moment, M due to earthquake, etc. If the assessment point (Mr, pr) lies inside the p–M line, the component with flaws is judged to be safe. In this paper, numerous experiments and FEAs for a cylinder with external multiple volumetric flaws were conducted under (1) pure internal pressure, (2) pure external bending moment, and (3) subjected simultaneously to both internal pressure and external bending moment, in order to determine the plastic collapse load at volumetric flaws by applying the twice-elastic slope (TES) as recommended by ASME. It has been clarified that the collapse (TES) loads are much the same as those calculated under the proposed p–M line based on the measured yield stress.

Load History Effect on Plastic Collapse in a Single-Edge Notched SUS316 Subjected to a Combined Tension and Bending

2002 ◽  
Author(s):  
Satoru Izawa ◽  
Masaaki Matsubara ◽  
Kikuo Nezu ◽  
Kenji Sakamoto
Keyword(s):  
Plastic Region ◽  
Bending Moment ◽  
Plastic Collapse ◽  
Collapse Load ◽  
Load History ◽  
Single Edge ◽  
Complex Load ◽  
Steel Members ◽  
Edge Notch ◽  
History Effect

This paper is evaluates the effects of load history on the plastic collapse load of stainless steel members with a single-edge notch. It considers, both the tension force due to an internal pressure and the bending moment caused by an earthquake, considered as load cases for a structure. Experimental equipment was specially developed to cope with the indeterminate problems in fracture mechanics. In this experiment, the stress state of a plastic collapse point was assessed using a membrane stress and axial displacement chart as well as a bending stress and deflection angle chart, which is well known as the ligament method. As a result, we successfully developed a new method for assessing plastic collapse under a complex load. We found that a different load history affects the formation of the plastic region and the collapse point position. The effects of load history on the plastic collapse load were not very big.

Plastic Collapse Load for Vessel With External Flaw Simultaneously Subjected to Internal Pressure and External Bending Moment: Experimental and FEA Results

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Shinji Konosu ◽  
Masato Kano ◽  
Norihiko Mukaimachi ◽  
Hiroyuki Komura ◽  
Hiroyuki Takada
Keyword(s):  
Internal Pressure ◽  
Yield Stress ◽  
Pressure Ratio ◽  
Safety Margin ◽  
Bending Moment ◽  
Plastic Instability ◽  
Plastic Collapse ◽  
Collapse Load ◽  
The Status ◽  
Work Done

This paper is based on work done to establish the validity of a simple engineering approach to assess plastic collapse for a vessel with a local thin area (LTA). The approach is based on a recently developed p-M (internal pressure ratio and external bending moment ratio) diagram, which is an easy way to visualize the status of a vessel with a LTA simultaneously subjected to internal pressure, p and external bending moment, M due to earthquake, etc. If the assessment point (Mr,pr) lies inside the p-M line, the vessel with the LTA is judged to be safe. Numerous experiments and finite element analyses for a cylinder with an external flaw were conducted under (1) pure internal pressure, (2) pure external bending moment, and (3) subjected simultaneously to both internal pressure and external bending moment, in order to determine the plastic initiation load and plastic collapse load by applying the twice-elastic slope (TES) as recommended by ASME. It has been clarified that the collapse (TES) loads are similar to those calculated under the proposed p-M line based on the measured yield stress. The p-M line adopted in the Ibaraki fitness for service (FFS) rule based on the specified minimum yield stress with a safety factor of 1.5 indicates that the safety margin for the plastic initiation loads at LTA is about 1.0–3.0, about 1.5–4.0 for the TES loads at LTA, and 2.5–6.5 for the plastic instability (break) loads.

Effect of Bend Angle on Plastic Limit Loads of Pipe Bends Under In-Plane Bending Moment

2016 ◽  
Author(s):  
Shunjie Li ◽  
Changyu Zhou ◽  
Jian Li ◽  
Xinting Miao
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Large Strain ◽  
Large Angle ◽  
Three Dimensional ◽  
Bending Moment ◽  
Limit Load ◽  
Bend Angle ◽  
Plastic Limit ◽  
Limit Loads

The effect of bend angle on plastic limit loads of pipe bends (elbows) under in-plane opening and closing bending moment is presented using three-dimensional large strain nonlinear finite element analyses. The results show that the presence of ovality significantly leads to the stress concentration in the middle cross section, which is the critical section of pipe bends. Meanwhile the state of stress concentration is also associated with the loading modes including the in-plane opening bending moment and the closing bending moment. Then plastic limit loads of pipe bends are further studied. It is found that plastic limit loads are decreasing with the increase of bend angles. Especially the variation of plastic limit loads of small angle pipe bends (bend angle from the 0 degree to 90 degree) is larger than that of large angle pipe bends (bend angle greater than 90 degree). Based on the finite element results, the present plastic limit load solutions are not fit for the large angle pipe bends (bend angle greater than 90 degree).

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