Predictions of Residual Stresses and Deformations in Pipe Bends Produced Using Cold, Warm and Induction Bending Processes

2014 ◽  
Author(s):  
Y. Ding ◽  
M. Yetisir ◽  
S. Khajehpour
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Numerical Models ◽  
Local Heating ◽  
Safety Evaluation ◽  
Stress Distributions ◽  
Advantages And Disadvantages ◽  
Cold Bending ◽  
Bending Process ◽  
Thickness Variations

Cold bending, warm bending (bending with local heating) and induction bending are three manufacturing processes widely used to produce pipe bends. The cold and warm bending processes have been used for the fabrication of carbon steel feeder bends for CANDU® reactors, and the induction bending process was considered for the fabrication of stainless steel feeder pipes for an advanced CANDU reactor. Bending processes result in plastic deformation, and inevitably, introduce residual stresses in the deformed pipes. Residual stresses in feeder bends are believed to be a very important contributing factor in feeder cracking. Different bending processes result in widely different residual stress patterns and magnitudes in pipe bends. Hence, it is important to understand the effect of bending processes and the process parameters used on the residual stress distribution in the bent pipes. Numerical models have been successfully developed to predict the residual stresses and the deformed shapes induced by cold, warm and induction bending processes. This paper provides a comprehensive review of the predicted residual stress distributions, ovality and wall-thickness variations of the cold, warm and induction bends. The predicted results were compared to earlier measurements of spare CANDU feeder bends and test bends. Advantages and disadvantages of the three bending processes are summarized. Numerical approaches for the modeling of residual stresses could be of benefit to engineering estimates of residual stresses in feeder pipes for safety evaluation of nuclear reactors.

On the Mechanics of Residual Stresses in Girth Welds

2006 ◽  
Vol 129 (3) ◽  
pp. 345-354 ◽  
Author(s):  
P. Dong
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Relative Importance ◽  
Stress Distributions ◽  
Unified Framework ◽  
Joint Geometry ◽  
Weld Residual Stress ◽  
Girth Welds ◽  
Welding Procedure

In this paper, some of the important controlling parameters governing weld residual stress distributions are presented for girth welds in pipe and vessel components, based on a large number of residual stress solutions available to date. The focus is placed upon the understanding of some of the overall characteristics in through-wall residual stress distributions and their generalization for vessel and pipe girth welds. In doing so, a unified framework for prescribing residual stress distributions is outlined for fitness-for-service assessment of vessel and pipe girth welds. The effects of various joint geometry and welding procedure parameters on through thickness residual stress distributions are also demonstrated in the order of their relative importance.

The Effect of Residual Stresses on the Fracture Resistance of Ductile Steels

2002 ◽  
Author(s):  
Noel P. O’Dowd ◽  
Yuebao Lei
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Crack Opening ◽  
Stress Distributions ◽  
Residual Stress Field ◽  
Element Analysis ◽  
Fatigue And Fracture ◽  
Negative Effect ◽  
Fracture Performance

Tensile residual stresses, such as those generated by welding, act as crack opening stresses and can have a negative effect on the fatigue and fracture performance of a component. In this work the effect of representative residual stress distributions on the fracture behaviour of a ferritic steel has been examined using finite element analysis. A Gurson-type void growth model is used to model the effect of ductile tearing ahead of a crack. For the cases examined it is seen that a tensile residual stress field may lead to a reduction in the toughness of the material (as represented by the J-resistance curve). The observed difference in toughness can be linked to the different constraint levels in the specimens due to the introduction of the residual stress field and can be rationalised through the use of a two parameter, J–Q approach.

Effects of Pipe Dimensions and Outer Surface-Buttering Weld Conditions on Residual Stress Distributions

2008 ◽  
Author(s):  
Nobuyoshi Yanagida
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Outer Surface ◽  
Hoop Stress ◽  
Axial Stress ◽  
Butt Joint ◽  
Stress Distributions ◽  
The Finite Element Method ◽  
Butt Joints ◽  
Inner Surface

Effects of pipe dimensions and outer surface-buttering weld conditions on residual stress distributions were evaluated using the finite element method. Residual stresses were analyzed for 508–mm-diameter (500A) pipe 38.1 mm thick, 508–mm-diameter (500A) pipe 15.1 mm thick, and 267–mm-diameter (250A) pipe 15.1 mm thick. After the residual stresses at pipe butt joints were analyzed, residual stresses at these joints subjected to the outer surface-buttering welds were analyzed. Residual stresses were determined for various weld widths, thicknesses, and heat inputs. These analyses indicate that tensile axial stress occurred at inner surface of the pipe butt joint and that it decreased with increasing the outer surface buttering-weld width or heat input. They also indicate that compressive hoop stress occurred at inner surface of the joint and that outer surface-buttering weld increased it. The outer surface-buttering weld conditions that generate compressive residual stress at the inner surface of the pipe butt joints were determined.

Formulas for Generating Prescribed Residual Stress Distributions in Center-Wound Rolls

1991 ◽  
Vol 58 (3) ◽  
pp. 836-840 ◽  
Author(s):  
Zine-Eddine Boutaghou ◽  
Thomas R. Chase
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Circumferential Stress ◽  
Stress Distributions ◽  
Wound Rolls

Altmann’s equations for describing the residual stresses in center-wound rolled webs are solved to determine the winding stress necessary to produce prescribed residual stress distributions in the finished roll. A solution for constant circumferential stress is expanded to control the peak winding stress. Two example winding problems are discussed.

Experimental Residual Stress and Geometric Imperfections on Pressure Hull Instability Analysis

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Paulo Rogério Franquetto ◽  
Miguel Mattar Neto
Keyword(s):  
Residual Stress ◽  
Numerical Models ◽  
Experimental Results ◽  
Pressure Reduction ◽  
Collapse Pressure ◽  
X Ray ◽  
Cold Bending ◽  
Portable System ◽  
Stress Profiles ◽  
Welding Processes

Residual stress produced by cold bending and welding processes contributes to the collapse pressure reduction of submarine hulls. Usually, the residual stress profiles used to quantify this reduction are obtained from analytical or numerical models. However, such models have limitations to take into account cold bending and welding in the same time. Hence, experimental analyses are necessary to better quantify the residual stress. Based on that, this paper presents residual stress experimental results obtained at six points on a pressure hull prototype using X-ray portable system. Based on these results, the residual stress profiles through the material thickness were estimated for each region on the frame by using a polynomial approximation. These profiles were introduced in a nonlinear finite element numerical model to study the collapse pressure reduction. Experimental results available on the literature were also used. Material and geometric nonlinearities were considered in the analysis. The results show that the residual stress reduces the collapse pressure as part of the frame web has stress level higher than the material yield. The preload introduced by the residual stress plays a less important role for the collapse pressure reduction at higher out-of-roundness and out-of-straightness defect amplitudes.

Residual Winding Stresses Due to Spatial Web Thickness Variation

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
J. K. Good ◽  
C. Mollamahmutoglu ◽  
R. Markum ◽  
J. W. Gale
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Thickness Variation ◽  
Feedback Parameter ◽  
Manufacturing Defects ◽  
Process Feedback ◽  
Thickness Variations ◽  
Control Feedback ◽  
Stress Variations ◽  
The Web

At the end of roll-to-roll (R2R) manufacturing process machines, the web substrate must be wound into rolls. Winding is the only means known to store and protect vast lengths of very thin webs for subsequent processing. Web thickness variation in wound rolls is a root cause of large manufacturing loss due to residual stress-related defects. Minute thickness variations down the length and across the web width can induce large residual stress variations and defects within the roll. Winding models allow the exploration of winding residual stresses whose variation has been affected by web thickness or coating imperfections. Knowledge of these stresses is used to mitigate manufacturing defects. Spot web thickness sensors are employed in R2R process lines that scan over the web width while the web is moving downstream through the process machine. Spatially, this provides a measure of web thickness in a zig-zag pattern. During manufacturing, the thickness variation is used as a control feedback parameter to manipulate a forming or coating die lip to reduce the web or coated web thickness variation. The thickness variation acceptable in process may be very different than that which is acceptable based on the residual stresses in the wound roll. It will be determined whether the thickness test data captured spatially for process feedback are sufficient to characterize the residual stresses in the wound roll. A winding model will be developed and verified that is used to characterize these residual stresses.

Experimental/Modelling Study of Residual Stress in Al/SiCp Bent Bars by Synchrotron XRD and Slitting Eigenstrain Methods

2008 ◽  
Vol 571-572 ◽  
pp. 277-282 ◽  
Author(s):  
Xu Song ◽  
Solène Chardonnet ◽  
Giancarlo Savini ◽  
Shu Yan Zhang ◽  
Willem J.J. Vorster ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Residual Strain ◽  
Numerical Models ◽  
Front Face ◽  
Stress Profile ◽  
X Ray Diffraction ◽  
Element Analysis ◽  
X Ray ◽  
Residual Stress Profile

The aim of the study presented here was to evaluate the residual stresses present in a bar of aluminium alloy 2124-T1 matrix composite (MMC) reinforced with 25vol% particulate silicon carbide (SiCp) using X-ray diffraction and 3D profilometry (curvature measurement using Mitutoyo/Renishaw coordinate measurement machine) and comparing these results with numerical models of residual strain and stress profiles obtained by a simple inelastic bending model and Finite Element Analysis (FEA). The residual strain distribution was introduced into the test piece by plastic deformation in the 4-point bending configuration. At the first stage of this study the elasticplastic behaviour of the MMC was characterized under static and cyclic loading to obtain the material parameters, hardening proprieties and cyclic hysteresis loops. Subsequently, synchrotron Xray diffraction and CMM curvature measurements were performed to deduce the residual stress profile in the central section of the bar. The experimental data obtained from these measurements were used in the inelastic bending and FEA simulations. The specimens were then subjected to incremental slitting using EDM (electric discharge machining) with continuous back and front face strain gauge monitoring. The X-ray diffraction and incremental slitting results were then analysed using direct and inverse eigenstrain methods. Residual stresses plots obtained by different methods show good agreement with each other.

Measurement of residual stresses in T-plate weldments

2003 ◽  
Vol 38 (4) ◽  
pp. 349-365 ◽  
Author(s):  
R. C Wimpory ◽  
P. S May ◽  
N. P O'Dowd ◽  
G. A Webster ◽  
D J Smith ◽  
...  
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Plastic Zone ◽  
Residual Stresses ◽  
Plate Thickness ◽  
Welding Process ◽  
Plastic Zone Size ◽  
Hole Drilling ◽  
Stress Distributions ◽  
Premature Failure

Tensile welding residual stresses can, in combination with operating stresses, lead to premature failure of components by fatigue and/or fracture. It is therefore important that welding residual stresses are accounted for in design and assessment of engineering components and structures. In this work residual stress distributions, obtained from measurements on a number of ferritic steel T-plate weldments using the neutron diffraction technique and the deep-hole drilling method, are presented. It has been found that the residual stress distributions for three different plate sizes are of similar shape when distances are normalized by plate thickness. It has also been found that the conservatisms in residual stress profiles recommended in current fracture mechanics-based safety assessment procedures can be significant—of yield strength magnitude in certain cases. Based on the data presented here a new, less-conservative transverse residual stress upper bound distribution is proposed for the T-plate weldment geometry. The extent of the plastic zone developed during the welding process has also been estimated by use of Vickers hardness and neutron diffraction measurements. It has been found that the measured plastic zone sizes are considerably smaller than those predicted by existing methods. The implications of the use of the plastic zone size as an indicator of the residual stress distributions are discussed.

Determination of Residual Stresses in Medium Density Fibreboard

Holzforschung ◽  
2000 ◽  
Vol 54 (2) ◽  
pp. 176-182 ◽  
Author(s):  
Jeroen van Houts ◽  
Debes Bhattacharyya ◽  
Krishnan Jayaraman
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Thickness Swell ◽  
Hole Drilling ◽  
Medium Density ◽  
Stress Distributions ◽  
Moisture Expansion ◽  
Hole Drilling Method ◽  
Drilling Method ◽  
Residual Internal Stress

Summary Due to the moisture and temperature gradients developed during hot pressing of medium density fibre-board (MDF), residual stresses occur within the board as it equilibrates to room conditions. It would be extremely useful to measure these residual stresses and to determine their effects on board properties such as moduli of elasticity and rupture in bending, internal bond strength and dimensional stability. In this article two methods, namely dissection and hole drilling, have been adapted to measure residual internal stress distributions in six different samples of industry produced MDF. The dissection method involves cutting several pieces of MDF perpendicular to the thickness direction at different depths. The residual stresses released by the dissection can be determined by measuring the curvatures of cut pieces and knowing their elastic moduli. The hole drilling method, on the other hand, involves mounting three strain gauges on the surface of a piece of MDF and drilling a hole to release residual stresses in close proximity. The released stresses are manifested as strains in the forms of which can be measured in three directions on the surface of the board. A theoretical model for predicting residual stresses involving various parameters has been developed and an excellent agreement with the experimental results from both the dissection and hole drilling methods has been achieved. Linear moisture expansion coefficient appears to have the greatest influence on residual stress. When compared against each other, the residual stresses measured by the hole drilling method show some shortcomings towards the centre of the board. While all six of the MDF boards exhibited similar trends in their residual stress distributions, significant differences were identified in the magnitudes of residual stress measured. Finally, some preliminary results linking the residual stress with the thickness swell of the samples and their surface densities have been presented.

Surface Effects and Residual Stresses in Electrolytically Ground Steel

1962 ◽  
Vol 84 (4) ◽  
pp. 483-489 ◽  
Author(s):  
J. Frisch ◽  
R. R. Cole
Keyword(s):  
Residual Stress ◽  
Corrosion Resistance ◽  
Residual Stresses ◽  
Material Removal ◽  
Removal Rate ◽  
Stress Distributions ◽  
Electrolyte Flow ◽  
Surface Conditions ◽  
Mechanical Removal ◽  
Grinding Conditions

The effects of electrolytic grinding on surface conditions and residual stress characteristics has been experimentally investigated. Surface finish, uniformity of material removal, and corrosion resistance are found to be dependent on mechanical removal rate as determined by wheel downfeed as well as electrolyte flow rate. Downfeeds of approximately 0.002 in. in the process do not produce measurable residual stresses and therefore it was further established that electrolytic grinding with moderate downfeeds can be used in place of swab etching techniques for evaluation of residual stress distributions. The maximum residual surface stresses were found to be not more than 22,000 psi, well below the yield strength of the material and were induced during the most severe grinding conditions.

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