Effect of Load Angle on Limit Load of Polyethylene Miter Pipe Bends

2010 ◽  
Author(s):  
Tarek M. A. A. EL-Bagory ◽  
Maher Y. A. Younan ◽  
Hossam E. M. Sallam ◽  
Lotfi A. Abdel-Latif
Keyword(s):  
Crack Depth ◽  
Bending Moment ◽  
Limit Load ◽  
Factor H ◽  
Pipe Bend ◽  
Combined Load ◽  
Specific Loading ◽  
Out Of Plane ◽  
Plane Bending ◽  
Load Angle

The aim of this paper is to investigate the effect crack depth a/W = 0 to 0.4 and load angle (30°,45°,and 60°) on the limit load of miter pipe bends (MPB) under out-of-plane bending moment with a crosshead speed 500 mm/min. The geometry of cracked and uncracked multi miter pipe bends are: bend angle, α = 90°, pipe bend factor, h = 0.844, standard dimension ratio, SDR = 11, and three junctions, m = 3. The material of the investigated pipe is a high-density polyethylene (HDPE), which is applied in natural gas piping systems. Butt-fusion welding is used to produce the welds in the miter pipe bends. An artificial crack is produced by a special cracking device. The crack is located at the crown side of the miter pipe bend, such that the crack is collinear with the direction of the applied load. The crack depth ratio, a/W = 0, 0.1, 0.2, 0.3 and 0.4 for out-of-plane bending moment “i.e. loading angle φ = 0°”. For each out-of-plane bending moment and all closing and opening load angles the limit load is obtained by the tangent intersection method (TI) from the load deflection curves produced by the specially designed and constructed testing machine at the laboratory. For each out-of-plane bending moment case, the experimental results reveals that increasing crack depth leads to a decrease in the stiffness and limit load of MPB. In case of combined load (out-of-plane and in-plane opening; mode) higher load angles lead to an increase in the limit load. The highest limit load value appears at a loading angle equal, φ = 60°. In case of combined load (out-of-plane and in-plane closing; mode) the limit load decreases upon increasing the load angle. On the other hand, higher limit load values take place at a specific loading angle equal φ = 30°. For combined load opening case; higher values of limit load are obtained. Contrarily, lower values are obtained in the closing case.

Effect of Load Angle on Limit Load of Polyethylene Miter Pipe Bends1

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Tarek M. A. A. EL-Bagory ◽  
Maher Y. A. Younan ◽  
Hossam E. M. Sallam ◽  
Lotfi A. Abdel-Latif
Keyword(s):  
Crack Depth ◽  
Bending Moment ◽  
Limit Load ◽  
Factor H ◽  
Pipe Bend ◽  
Combined Load ◽  
Specific Loading ◽  
Out Of Plane ◽  
Plane Bending ◽  
Load Angle

The aim of this paper is to investigate the effect of crack depth a/W = 0–0.4 and load angle (30 deg, 45 deg, and 60 deg) on the limit load of miter pipe bends (MPB) under out-of-plane bending moment with a crosshead speed 500 mm/min. The geometry of cracked and un-cracked multi miter pipe bends are: bend angle, α = 90 deg, pipe bend factor, h = 0.844, standard dimension ratio, SDR = 11, and three junctions, m = 3. The material of the investigated pipe is a high-density polyethylene (HDPE), which is applied in natural gas piping systems. Butt-fusion welding is used to produce the welds in the miter pipe bends. An artificial crack is produced by a special cracking device. The crack is located at the crown side of the miter pipe bend, such that the crack is collinear with the direction of the applied load. The crack depth ratio, a/W = 0, 0.1, 0.2, 0.3, and 0.4 for out-of-plane bending moment “i.e., loading angle ϕ = 0 deg”. For each out-of-plane bending moment and all closing and opening load angles the limit load is obtained by the tangent intersection method (TI) from the load deflection curves produced by the specially designed and constructed testing machine at the laboratory (Mechanical Design Department, Faculty of Engineering, Mataria, Helwan University, Cairo/Egypt). For each out-of-plane bending moment case, the experimental results reveals that increasing crack depth leads to a decrease in the stiffness and limit load of MPB. In case of combined load (out-of-plane and in-plane opening; mode) higher load angles lead to an increase in the limit load. The highest limit load value appears at a loading angle equal, ϕ = 60 deg. In case of combined load (out-of-plane and in-plane closing; mode) the limit load decreases upon increasing the load angle. On the other hand, higher limit load values appear at a specific loading angle equal ϕ = 30 deg. For combined load opening case; higher values of limit load are obtained. Contrarily, lower values are obtained in the closing case.

Limit Load of Pre-Cracked Polyethylene Miter Pipe Bends Subjected to In-Plane Bending Moment

2010 ◽  
Author(s):  
Tarek M. A. A. EL-Bagory ◽  
Maher Y. A. Younan ◽  
Hossam E. M. Sallam ◽  
Lotfi A. Abdel-Latif
Keyword(s):  
High Density Polyethylene ◽  
Crack Depth ◽  
Testing Machine ◽  
Bending Moment ◽  
Limit Load ◽  
Factor H ◽  
Bend Angle ◽  
Pipe Bend ◽  
Piping Systems ◽  
Plane Bending

The main purpose of the present paper is to investigate the effect of crack depth on the limit load of miter pipe bends (MPB) under in-plane bending moment. The experimental work is conducted to investigate multi miter pipe bends, with a bend angle 90°, pipe bend factor h = 0.844, standard dimension ratio SDR = 11, and three junctions under a crosshead speed 500 mm/min. The material of the investigated pipe is a high-density polyethylene (HDPE), which is used in natural gas piping systems. The welds in the miter pipe bends are produced by butt-fusion method. The crack depth varies from intrados to extrados location according to the in-plane opening/closing bending moment respectively. For each in-plane bending moment the limit load is obtained by the tangent intersection (TI) method from the load deflection curves produced by the testing machine specially designed and constructed in the laboratory. The study reveals that increasing the crack depth leads to a decrease in the stiffness and limit load of (MPB) for both inplane closing and opening bending moment. Higher values of the limit load are reached in case of opening bending moment. This behavior is true for all investigated crack depths.

Limit Load Determination and Material Characterization of Cracked Polyethylene Miter Pipe Bends1

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Tarek M. A. A. EL-Bagory ◽  
Maher Y. A. Younan ◽  
Hossam E. M. Sallam ◽  
Lotfi A. Abdel-Latif
Keyword(s):  
Fracture Toughness ◽  
Limit Load ◽  
Factor H ◽  
Thickness Variation ◽  
Pipe Bend ◽  
Manufacturing Defects ◽  
Combined Load ◽  
Crosshead Speed ◽  
Out Of Plane ◽  
Load Angle

The quality of Natural Gas Piping Systems (NGPS), must be ensured against manufacturing defects. The main purpose of the present paper is to investigate the effect of loading mode and load angle (30 deg, 45 deg, and 60 deg) on the limit load of miter pipe bends (MPB), under different crack depths a/W = 0–0.4 at a crosshead speed 500 mm/min. The geometry of cracked and uncracked multi-miter pipe bends are pipe bend angle, α = 90 deg, pipe bend factor, h = 0.844, standard dimension ratio, SDR = 11, and three junctions, m = 3. The material of the investigated pipe is a high-density polyethylene (HDPE), which is commonly used in NGPS. The welds at the miter pipe junction are produced by butt-fusion welding. For all loading modes the limit load is obtained by the tangent intersection (TI) method from the load–deflection curves produced by the specially designed and constructed testing machine at the laboratory5. Tensile tests are conducted on specimens longitudinally extruded from the pipe with thickness, T = 10, 30 mm, at different crosshead speeds (5–500 mm/min), and different gauge lengths (G = 20, 25, and 50 mm) to determine the mechanical properties of welded and unwelded specimens. The fracture toughness is determined on the basis of elastic plastic fracture mechanics (EPFM). Curved three-point bend specimens (CTPB), are used. All specimens are provided with artificial precrack at the crack tip, a/W = 0.5. The effect of specimen thickness variation (B = 10, 15, 22.5, 30, 37.5, and 45 mm) for welded and unwelded specimens is studied at room temperature (Ta = 23 °C) and at different crosshead speeds, VC.H, ranging from 5 to 500 mm/min. The study reveals that increasing the crack depth leads to a decrease in the stiffness and limit load of MPB for both in-plane, and out-of-plane bending moment. In case of combined load (out-of-plane and in-plane opening; mode), higher load angles lead to an increase in the limit load. The highest limit load value occurs at a loading angle, ϕ = 60 deg. In case of combined load (out-of-plane and in-plane closing; mode), the limit load decreases with increasing load angles. At a load angle ϕ = 30 deg, the higher limit load value occurred in both cases. For combined load opening case, higher values of limit load are obtained. The crosshead speed has a significant effect on the mechanical behavior of both welded and unwelded specimens. The fracture toughness, JIC, is greater for unwelded than welded specimen.

Limit Load Determination and Material Characterization of Cracked Polyethylene Miter Pipe Bends

2011 ◽  
Author(s):  
Tarek M. A. A. EL-Bagory ◽  
Maher Y. A. Younan ◽  
Hossam E. M. Sallam
Keyword(s):  
Fracture Toughness ◽  
Natural Gas ◽  
Limit Load ◽  
Factor H ◽  
Pipe Bend ◽  
Combined Load ◽  
Crosshead Speed ◽  
Piping Systems ◽  
Out Of Plane ◽  
Load Angle

The quality of Natural Gas Piping Systems, NGPS, must be ensured against manufacturing defects. The main purpose of the present paper is to investigate the effect of loading mode and load angle (30°,45°, and 60°) on the limit load of miter pipe bends, MPB, under different crack depths a/W = 0 to 0.4 at a crosshead speed 500 mm/min. The geometry of cracked and un-cracked multi miter pipe bends are: pipe bend angle, α = 90°, pipe bend factor, h = 0.844, standard dimension ratio, SDR = 11, and three junctions, m = 3. The material of the investigated pipe is a high-density polyethylene, HDPE, which is commonly used in natural gas piping systems. The welds at the miter pipe junction are produced by butt-fusion welding. For all loading modes the limit load is obtained by the tangent intersection method, TI, from the load deflection curves produced by the specially designed and constructed testing machine at the laboratory. Tensile tests are conducted on specimens longitudinally extruded from the pipe with thickness, T = 10, 30 mm, at different crosshead speeds (5–500 mm/min), and different gauge lengths (G = 20, 25, and 50 mm) to determine the mechanical properties of welded and un-welded specimens. The fracture toughness is determined on the basis of elastic plastic fracture mechanics, EPFM. Curved three-point bend specimens, CTPB, are used. All specimens are provided with artificially pre-crack at the crack tip, a/W = 0.5. The effect of specimen thickness variation (B = 10, 15, 22.5, 30, 37.5, and 45mm) for welded and un-welded specimens is studied at room temperature (Ta = 23°C) and at different crosshead speeds, VC.H, ranging from 5 to 500 mm/min. The study reveals that increasing the crack depth leads to a decrease in the stiffness and limit load of MPB for both in-plane, and out-of-plane bending moment. In case of combined load (out-of-plane and in-plane opening; mode) higher load angles lead to an increase in the limit load. The highest limit load value occurs at a loading angle, φ = 60°. In case of combined load (out-of-plane and in-plane closing; mode) the limit load decreases with increasing load angles. On the other hand, higher limit load values are proved at a load angle, φ = 30°. For combined load opening case; higher values of limit load are obtained. The crosshead speed has a significant effect on the mechanical behavior of both welded and un-welded specimens. The fracture toughness, JIC, is greater for un-welded than welded specimen.

Plastic Load of Precracked Polyethylene Miter Pipe Bends Subjected to In-Plane Bending Moment1

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Tarek M. A. A. EL-Bagory ◽  
Maher Y. A. Younan ◽  
Hossam E. M. Sallam ◽  
Lotfi A. Abdel-Latif
Keyword(s):  
Crack Depth ◽  
Testing Machine ◽  
Bending Moment ◽  
Factor H ◽  
Bend Angle ◽  
Pipe Bend ◽  
Obvious Effect ◽  
Linear Elastic ◽  
Piping Systems ◽  
Plane Bending

The main purpose of the present paper is to investigate the effect of crack depth on the plastic load (collapse load) of miter pipe bends (MPB) under in-plane bending moment. The experimental work is conducted to investigate multimiter pipe bends, with a bend angle 90 deg, pipe bend factor h = 0.844, standard dimension ratio (SDR) = 11, and number of welding junctions m = 3 under a crosshead speed 500 mm/min. The material of the investigated pipe is a high-density polyethylene (HDPE), which is used in natural gas (NG) piping systems. The welds in the miter pipe bends are produced by butt-fusion method. The crack depth varies from intrados to extrados location according to the in-plane opening/closing bending moment, respectively. For each in-plane bending moment, the plastic load is obtained by the tangent intersection (TI) method from the load–deflection curves produced by the testing machine specially designed and constructed in the laboratory.5 The study reveals that increasing the crack depth leads to a decrease in the stiffness and plastic load of MPB for both in-plane closing and opening bending moment. Higher values of the plastic load are reached in case of opening bending moment. This behavior is true for all investigated crack depths. A circumferential external crack has an obvious effect on the behavior of load–deflection curve. The linear elastic region in both mode of loading decreases with increasing crack depth.

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

2017 ◽  
Vol 62 (3) ◽  
pp. 1881-1887
Author(s):  
P. Ramaswami ◽  
P. Senthil Velmurugan ◽  
R. Rajasekar
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Limit Load ◽  
Outer Radius ◽  
Factor H ◽  
Geometrical Shape ◽  
Element Analysis ◽  
Pipe Bend ◽  
Plane Bending

Abstract The present paper makes an attempt to depict the effect of ovality in the inlet pigtail pipe bend of a reformer under combined internal pressure and in-plane bending. Finite element analysis (FEA) and experiments have been used. An incoloy Ni-Fe-Cr B407 alloy material was considered for study and assumed to be elastic-perfectly plastic in behavior. The design of pipe bend is based on ASME B31.3 standard and during manufacturing process, it is challenging to avoid thickening on the inner radius and thinning on the outer radius of pipe bend. This geometrical shape imperfection is known as ovality and its effect needs investigation which is considered for the study. The finite element analysis (ANSYS-workbench) results showed that ovality affects the load carrying capacity of the pipe bend and it was varying with bend factor (h). By data fitting of finite element results, an empirical formula for the limit load of inlet pigtail pipe bend with ovality has been proposed, which is validated by experiments.

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.

Shakedown Boundary of a 90–Degree Back–to–Back Pipe Bend Subjected to Steady Internal Pressures and Cyclic Out–of–Plane Bending Moments

2014 ◽  
Author(s):  
Hany F. Abdalla
Keyword(s):  
Internal Pressure ◽  
Bending Moment ◽  
Bending Moments ◽  
Pipe Bend ◽  
Structure Comparison ◽  
Out Of Plane ◽  
Plane Bending ◽  
Shakedown Limit ◽  
Elastic Shakedown ◽  
Internal Pressures

Ninety degree back–to–back pipe bends are extensively utilized within piping networks of modern nuclear submarines and modern turbofan aero–engines where space limitation is considered a supreme concern. According the author’s knowledge, no shakedown analysis exists for such structure based on experimental data. In the current research, the pipe bend setup analyzed is subjected to a spectrum of steady internal pressures and cyclic out–of–plane bending moments. A previously developed direct non–cyclic simplified technique, for determining elastic shakedown limit loads, is utilized to generate the elastic shakedown boundary of the analyzed structure. Comparison with the elastic shakedown boundary of the same structure, but subjected to cyclic in–plane bending moments revealed a higher shakedown boundary for the out–of–plane bending loading configuration with a maximum bending moment ratio of 1.4 within the low steady internal pressure spectrum. The ratio decreases towards the medium to high internal pressure spectrum. The simplified technique outcomes showed excellent correlation with the results of full elastic–plastic cyclic loading finite element simulations.

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.

Limit and Shakedown Loads Determination for Locally Thinned Wall Pipe Branch Connection Subjected to Pressure and Bending Moments

2012 ◽  
Author(s):  
Youssef A. F. Hafiz ◽  
Maher Y. A. Younan ◽  
Hany F. Abdalla
Keyword(s):  
Numerical Models ◽  
Bending Moment ◽  
Limit Load ◽  
Tension Stress ◽  
Assessment Procedure ◽  
Wall Thinning ◽  
Out Of Plane ◽  
Plane Bending ◽  
Shakedown Limit ◽  
Local Wall Thinning

In this paper the shakedown limit load for unreinforced locally thinned wall pipe branch connection is determined using the Simplified Technique. Loadings were considered to be internal pressure, as a steady load, with in-plane bending or with out-of-plane bending applied on the branch, as alternating loads. Two locations of local wall thinning were taken; one was on the run pipe opposite to the branch and other on the branch at the maximum tension stress side of the bending moment applied whether in in-plane or out-of-plane situation. Two Finite Element (FE) limit load models were used to verify the modeling of the pipe branch connection with its local wall thinning. First model results were compared with experimental data taken from the literature, and the second results were compared with numerical models taken also from the literature and also compared with API 579 “Fitness For Service” (FFS), part-five, level-two assessment procedure. First and second comparisons lead to good agreement but for API 579 comparison it was found that it is slightly changing with the depth of the local wall thinning but does not reflect the expected behavior of the limit load as the FEA models showed. For the results of the shakedown limit load analysis, Bree diagrams were constructed to show elastic, shakedown and plastic collapse regions. Then, comparison was made to show the effect of the local wall thinning depth and location on previous limits. Finally, the shakedown results were verified using the elastic-plastic ratcheting analysis of API 579, level three assessment and it showed successfully the shakedown, ratcheting and reversed plasticity regions. This verifications and results can prove that the Simplified Technique can be used as a level-three ratcheting assessment in API 579.

Sign in / Sign up

Export Citation Format

Share Document