Stress Analysis of Stainless Steel Elbow and Tee Fittings Subjected to Internal Pressure and External Loads

1999 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Tetsuya Furuya ◽  
Tadahiro Murakami ◽  
Yasuyuki Kagaya
Keyword(s):  
Internal Pressure ◽  
Wall Thickness ◽  
Bending Moment ◽  
Maximum Pressure ◽  
Screw Thread ◽  
The Finite Element Method ◽  
Internal Working ◽  
Stress States ◽  
Screw Threads ◽  
External Loads

Abstract In this paper, mechanical behaviors of the Elbow and Tee fittings connected to pipes by screw threads under internal pressure, external tensile loads and bending moment are analyzed using the Finite Element Method (FEM). FEM code employed is MARC. The maximum Mises stress of the Elbow and Tee fittings are obtained when the wall thickness is changed while the internal working maximum pressure is held constant at 20bar. The elasto-plastic stress states of screw threads the fittings and the pipes are obtained under internal pressure and external loads. Under the assumptions that nodal points are released when the strain of the elements reaches the rupture strain of the fitting’s material, the load when the rupture occurs at the screw thread is analyzed. The safety factor for the wall thickness of the Elbow and Tee fittings used in the experiment is found to be about 5. The results indicate deduced that the dimensions of Elbow and Tee fittings can be reduced. The strength of the fittings under internal pressure and external loads is obtained. It is found that the stress concentrates at the first root of male thread and expected that a fracture initiates at the first root. The strain of the Elbow and Tee fittings subjected to internal pressure were measured by using strain gauges. The numerical results are in a fairly good agreement with the experimental results.

FEM Stress Analysis and the Sealing Performance Evaluation in Stainless Steel Elbow and Tee Fittings Under Internal Pressure: Case Where Internal Fluid is Liquid

2004 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Hideaki Shimazu
Keyword(s):  
Stainless Steel ◽  
Internal Pressure ◽  
Stress Analysis ◽  
Chemical Plants ◽  
Three Dimension ◽  
Sealing Performance ◽  
Internal Fluid ◽  
Calculated Stress ◽  
Stress States ◽  
Screw Threads

Stainless steel fittings such as elbows, tees, nipples and so on have been widely used in mechanical structures and chemical plants, it is well known that the leakage in the fittings used sealing tapes is less than that without the sealing tapes. In a practical design, it is necessary to examine the stress states and the leakage in the fittings under internal pressure and external loads such as tensile loads, bending moments and so on. This paper deals with the FEM stress analysis of the fittings subjected to internal pressure. In the FEM calculations, the engaged screw threads are taken into consideration as helical threads in the three-dimension. The leakage tests for the fittings under internal pressure were also conducted by using liquid (oil). Using the results of the leakage tests and the calculated stress states in the fittings, the sealing performance of the fittings under internal pressure was evaluated and the effect of the tightening torque was clarified on the sealing performance. In addition, the numerical results were compared with the experimental results. As the result, the effects of the sealing tapes on the contact stress distributions were also clarified.

Effects of Nut Thinning due to Corrosion on the Strength Characteristics and the Sealing Performance of Bolted Flange Joints Under Internal Pressure

2011 ◽  
Author(s):  
Tsutomu Kikuchi ◽  
Yuya Omiya ◽  
Toshiyuki Sawa
Keyword(s):  
Internal Pressure ◽  
Yield Stress ◽  
Strength Characteristic ◽  
Small Scale ◽  
Screw Thread ◽  
Flange Joint ◽  
Bearing Surface ◽  
Sealing Performance ◽  
Bolted Flange ◽  
Screw Threads

The effects of nut thinning due to corrosion on the strength characteristic and the sealing performance in 3B bolted flange joints under internal pressure are examined from both FEM calculations and experiments. The following results are obtained. When bolts and nuts in a bolted flange joint are tightened with 50% of yield stress, no yield region at the engaged screw thread occurs, however, when they arc tightened with 90% of the yield stress, a small scale yield region occurs at the roots of the engaged three screw threads from the bearing surface of the nut. While verifying this phenomenon using FEM, it was newly discovered that when the height of the nut was reduced to 1/3 (equivalent to approximately two threads) of the original dimensions according to the standards, the sealing performance could no longer be assured.

3-D FEM Stress Analysis of Screw Threads in Bolted Joints Under Static Tensile Loadings

2014 ◽  
Author(s):  
Shunichiro Sawa ◽  
Mitsutoshi Ishimura ◽  
Yuya Omiya ◽  
Toshiyuki Sawa
Keyword(s):  
Plastic Deformation ◽  
Bolted Joints ◽  
Experimental Result ◽  
Screw Thread ◽  
Numerical Result ◽  
Static Tensile ◽  
Hollow Cylinders ◽  
Stress States ◽  
Plastic Deformation Region ◽  
Screw Threads

The stress concentration factor (SCF) for the roots of screw threads in bolted joints under static loadings is analyzed using 3-D elastic FEM taking account the spiral of screw threads. At first, the stress states at the roots of screw threads in initial clamping state in a bolted joint where two hollow cylinders were clamped with a bolt and a nut were analyzed in initial clamping. The elastic FEM result of SCF for the first root was obtained as SCF=3.2. When the bolt was clamped in initial clamping (preload) at the 60 % of bolt yield stress, the plastic deformations were found at the first and the second roots, and non-engaged screw threads. It was found that as the external tensile loads increased, the development in plastic deformation region increased from the first root to the other roots as well as the non-engaged screw threads. It was found that the rupture occurred from the non-engaged screw threaded part while the plastic deformation increased at each root of screw threads. The numerical result was coincided with the experimental result. In the experiments, it was observed that the rupture occurred from the non-engaged screw thread and not from the first root of screw thread. Also, the bolt fatigue was predicted from FEM and it was shown that a fatigue fracture occurred from the first root.

Bending Capacity of Pipe Bends in Deepwater Conditions

2010 ◽  
Author(s):  
Shulong Liu ◽  
Alastair Walker ◽  
Philip Cooper
Keyword(s):  
Internal Pressure ◽  
Induction Heating ◽  
Wall Thickness ◽  
Failure Modes ◽  
Limit State ◽  
Bending Moment ◽  
External Pressure ◽  
Fe Method ◽  
Moment Capacity ◽  
Operation Conditions

Offshore pipeline systems commonly incorporate induction-heating formed bends along flowlines and in pipeline end termination assemblies and spools. In deepwater locations, the pipeline and bends are subjected to various combinations of external pressure, internal pressure, bending moment and temperature changes, during installation, and operation. Although there is a history of research into the limiting loads and failure modes of such bends and pipelines systems there is, as yet, no comprehensive guidance to enable the calculation of the maximum capacity under combined bending and external pressure loading. Conservative guidance is presented in DNV OS-F101 (2007) [1] that proposes increasing the pipe wall thickness to reduce the effect of external pressure collapse effects thus enabling bending formulations relevant to straight pipe to be used. This proposed approach leads to unfeasibly large wall thickness requirements in very deepwater applications. There is therefore a requirement for a method to design deepwater bends for installation and operation conditions with levels of safety comparable with those used in the design of straight sections of pipelines that does not depend on the requirement to increase the wall thickness to the extent proposed in the current DNV guidance. In this study, a nonlinear FE method using ABAQUS is proposed to evaluate the ultimate capacities of induction-heating formed bends. The method takes into account the combined effects of non-linear material properties, initial ovality, wall thinning/thickening, external or internal pressure, internal CRA cladding and temperature change on the ultimate moment capacity of the bend. The numerical model is validated by comparison with available published results. The method developed here is based on the limit state design formulations in the current DNV OS-F101 guidance.

scholarly journals The Effect of Internal Pressure on Radial Strain of Steel Pipe Subjected to Monotonic and Cyclic Loading

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2849 ◽  
Author(s):  
Costel Pleșcan ◽  
Mariana D. Stanciu ◽  
Matyas Szasz
Keyword(s):  
Finite Element Method ◽  
Internal Pressure ◽  
Failure Modes ◽  
Radial Strain ◽  
The Finite Element Method ◽  
Steel Pipes ◽  
Environmental Disasters ◽  
Plastic Domain ◽  
Stress States ◽  
Hardening Of Materials

Steel pipes in different engineering applications may fail, leading to numerous environmental disasters. During loading, certain mechanical and chemical phenomena develop inside the pipes and cause them to burst. In this study, the influence of internal pressure on the elastic and plastic behaviour of E355 steel pipes was investigated on small specimens with different wall thicknesses. First, the failure modes of pipes subjected to monotonic loading were assessed, and then the behaviour of specimens subjected to cyclic internal pressure was analysed in terms of variation of radial strain. The strain and stress states of pipes were analysed using the finite element method. The results revealed that the hardening of materials inside the pipes increases the risk of cracking and bursting because of elasticity limits being exceeded, causing entry into the plastic domain. The transition of mechanical behaviour can be observed in the microstructure of steel in cracked areas from the inside to the outside of the pipe.

Bifurcation of Elastic-Plastic Circular Cylindrical Shells Under Internal Pressure

1979 ◽  
Vol 46 (4) ◽  
pp. 889-894 ◽  
Author(s):  
C.-C. Chu
Keyword(s):  
Internal Pressure ◽  
Critical Pressure ◽  
Separation Of Variables ◽  
Cylindrical Shells ◽  
Maximum Pressure ◽  
Thin Shells ◽  
The Finite Element Method ◽  
Elastic Plastic ◽  
Analytical Results ◽  
Good Agreement

The bifurcation of long elastic-plastic cylindrical shells subject to internal pressure is investigated. It is assumed that the end conditions are such that plane strain conditions prevail. For thin shells, simple approximate bifurcation criteria are obtained analytically. The finite-element method is then employed, in conjunction with separation of variables, to obtain the bifurcation conditions for cylindrical shells with arbitrary thickness to radius ratios. For sufficiently thin shells, the numerical and the analytical results are in good agreement for the critical pressure at bifurcation. The numerical and analytical results both indicate that, for sufficiently thin shells, a variety of bifurcation modes are available virtually simultaneously at this critical pressure. However, for thicker shells, the numerical results reveal that there is a single preferred bifurcation mode. The mode number associated with this preferred bifurcation mode depends on the thickness to radius ratio. The possibility of bifurcation occurring before the attainment of the maximum pressure is also explored. For the specific cases investigated here, bifurcation always occurs after the maximum pressure point.

Study on steel wire reinforced thermoplastic pipes under combined internal pressure and bending moment at various temperatures

2021 ◽  
Vol 169 ◽  
pp. 108381
Author(s):  
Jianfeng Shi ◽  
Sijia Zhong ◽  
Xinyu Nie ◽  
Jun Shi ◽  
Jinyang Zheng
Keyword(s):  
Internal Pressure ◽  
Steel Wire ◽  
Bending Moment

Ratcheting assessment of corroded elbow pipes subjected to internal pressure and cyclic bending moment

2021 ◽  
pp. 030932472198989
Author(s):  
Ali Salehi ◽  
Armin Rahmatfam ◽  
Mohammad Zehsaz
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Internal Pressure ◽  
Bending Moment ◽  
Axial Direction ◽  
Hoop Strain ◽  
Cyclic Bending ◽  
High Fatigue ◽  
The Impact ◽  
Cyclic Bending Moment

The present study aimed to study ratcheting strains of corroded stainless steel 304LN elbow pipes subjected to internal pressure and cyclic bending moment. To this aim, spherical and cubical shapes corrosion are applied at two depths of 1 mm and 2 mm in the critical points of elbow pipe such as symmetry sites at intrados, extrados, and crown positions. Then, a Duplex 2205 stainless steel elbow pipe is considered as an alternative to studying the impact of the pipe materials, due to its high corrosion resistance and strength, toughness, and most importantly, the high fatigue strength and other mechanical properties than stainless steel 304LN. In order to perform numerical analyzes, the hardening coefficients of the materials were calculated. The results highlight a significant relationship between the destructive effects of corrosion and the depth and shape of corrosion, so that as corrosion increases, the resulting destructive effects increases as well, also, the ratcheting strains in cubic corrosions have a higher growth rate than spherical corrosions. In addition, the growth rate of the ratcheting strains in the hoop direction is much higher across the studied sample than the axial direction. The highest growth rate of hoop strain was observed at crown and the highest growth rate of axial strains occurred at intrados position. Altogether, Duplex 2205 material has a better performance than SS 304LN.

Elasto-Plastic Stress Distribution in Triplate Joint Assembly under Bending Moment

2007 ◽  
Vol 345-346 ◽  
pp. 1437-1440
Author(s):  
Tae Hyun Baek ◽  
Seung Kee Koh ◽  
Jie Cheng
Keyword(s):  
Finite Element Method ◽  
Residual Stresses ◽  
Pure Aluminum ◽  
Main Tool ◽  
Bending Moment ◽  
The Finite Element Method ◽  
Shipbuilding Industry ◽  
Structural Parts ◽  
Von Mises

Pre-produced triplate transition joint assemblies are widely used in shipbuilding industry to make welds between aluminum and steel for a number of years now. The straight-shaped transition joint assemblies are bent during shipbuilding. So it is necessary to study the residual stresses created by punch forming, which would have heavy effects on the quality of structural parts. ABAQUS is a suite of powerful engineering simulation programs, based on the finite element method. In this paper, ABAQUS was used as the main tool to simulate the residual stresses in a triplate transition joint after unloading. Punch-pressing was carried to simulate bending moment in ABAQUS. The triplate is consisted of baselayer (steel: Lloyd’s Shipplate Gr. A), interlayer (pure aluminum: Al99.5) and superlayer (Al-Mg alloy: AlMg4.5Mn). Results from the ABAQUS analysis showed that increasing the radius of punch significantly reduced the von Mises residual stresses in steel. Changes of von Mises residual stresses in interlayer (Al99.5) and superlayer (AlMg4.5Mn) were negligible.

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