Effect of Residual Forming Stresses on Fracture in ERW Pipe

2016 ◽  
Author(s):  
Ted L. Anderson ◽  
Gregory W. Brown
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Fracture Behavior ◽  
Finite Element Simulations ◽  
Finite Element Analyses ◽  
Forming Process ◽  
Cold Expansion ◽  
The Past

Many older pipelines contain significant residual stress due to the forming process. Cold expansion or a normalizing heat treatment can virtually eliminate residual forming stresses, but these practices were less common in the past. In the absence of cold expansion or normalization, residual forming stresses can be reduced by hydrostatic testing or operating pressures, but not eliminated entirely. Residual stresses can contribute to fracture in pipelines, particularly when the material toughness is low. This article presents a series of analyses that seek to quantify the magnitude of residual forming stresses as well as their impact on pipeline integrity. The pipe forming process was simulated with elastic-plastic finite element analyses, which considered the effect of subsequent loading on relaxation of residual stresses. A second set of finite element simulations were used to quantify the effect of residual stresses on fracture behavior.

Evaluation of Residual Stresses in Small Diameter Stainless Steel Pipe Welds by Two-Dimensional and Three-Dimensional Finite Element Analyses

2014 ◽  
Author(s):  
Francis H. Ku ◽  
Trevor G. Hicks ◽  
William R. Mabe ◽  
Jason R. Miller
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Steel Pipe ◽  
3D Analysis ◽  
Two Dimensional ◽  
Finite Element Analyses ◽  
Stainless Steel Pipe

Two-dimensional (2D) and three-dimensional (3D) weld-induced residual stress finite element analyses have been performed for 2-inch Schedule 80 Type-304 stainless steel pipe sections joined by a multi-layer segmented-bead pipe weld. The analyses investigate the similarities and differences between the two modeling approaches in terms of residual stresses and axial shrinkage induced by the pipe weld. The 2D analyses are of axisymmetric behavior and evaluate two different pipe end constraints, namely fixed-fixed and fixed-free, while the 3D analysis approximates the non-axisymmetric segmented welding expected in production, with fixed-free pipe end constraints. Based on the results presented, the following conclusions can be drawn. The welding temperature contour results between the 2D and 3D analyses are very similar. Only the 3D analysis is capable of simulating the non-axisymmetric behavior of the segmented welding technique. The 2D analyses yield similar hoop residual stresses to the 3D analysis, and closely capture the maximum and minimum ID surface hoop residual stresses from the 3D analysis. The primary difference in ID surface residual stresses between the 2D fixed-fixed and 2D fixed-free constraints cases is the higher tensile axial stresses in the pipe outside of the weld region. The 2D analyses under-predict the maximum axial residual stress compared to the 3D analysis. The 2D ID surface residual stress results tend to bound the averaged 3D results. 2D axisymmetric modeling tends to significantly under-predict weld shrinkage. Axial weld shrinkage from 3D modeling is of the same magnitude as values measured in the laboratory on a prototypic mockup.

Residual Stresses in Clad Nuclear Reactor Pressure Vessel Steels: Prediction, Measurement and Reconstruction

2015 ◽  
Author(s):  
Karim Serasli ◽  
Harry Coules ◽  
David Smith
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Pressure Vessel ◽  
Nuclear Reactor ◽  
Finite Element Simulations ◽  
Reactor Pressure Vessel ◽  
Mapping Technique ◽  
Pressure Vessel Steels ◽  
Reactor Pressure

Most residual stress measurement methods are limited in terms of their stress and spatial resolution, number of stress tensor components measured and measurement uncertainty. In contrast, finite element simulations of welding processes provide full field distributions of residual stresses, with results dependent on the quality of the input conditions. Measurements and predictions are often not the same, and the true residual stress state is difficult to determine. In this paper both measurements and predictions of residual stresses, created in clad nuclear reactor pressure vessel steels, are made. The measurements are then used as input to a residual stress mapping technique provided within a finite element analysis. The technique is applied iteratively to converge to a balanced solution which is not necessarily unique. However, the technique aids the identification of locations for additional measurements. This is illustrated in the paper. The outcomes from the additional measurements permit more realistic and reliable estimates of the true residual state to be made. The outcomes are compared with the finite element simulations of the welding process and used to determine whether there is a need for additional input to the simulations.

A method for the measurement of residual stresses using a fracture mechanics approach

1989 ◽  
Vol 24 (1) ◽  
pp. 23-30 ◽  
Author(s):  
K J Kang ◽  
J H Song ◽  
Y Y Earmme
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Distribution ◽  
Fracture Mechanics ◽  
Residual Stresses ◽  
Residual Stress Distribution ◽  
The State ◽  
Two Dimensional ◽  
Finite Element Analyses ◽  
Simple Method

A simple method for measuring residual stresses in a plate is described. In this method residual stresses are evaluated using a fracture mechanics approach, that is, the strains or displacements measured at a point on the edge of a plate as a crack is introduced and extended from the edge are used to deduce the state of stresses that existed in the uncracked plate. Through finite element analyses and experiments this method is shown to be valid and effective for measuring the two-dimensional residual stress distribution of a welded plate.

scholarly journals Residual Stress From Cold Expansion of Fastener Holes: Measurement, Eigenstrain, and Process Finite Element Modeling

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Renan L. Ribeiro ◽  
Michael R. Hill
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Slow Crack Growth ◽  
Measurement Data ◽  
Equivalent Plastic Strain ◽  
Contour Method ◽  
Elastic Behavior ◽  
Plastic Behavior ◽  
Cold Expansion

Cold expansion (CX) is a material processing technique that has been widely used in the aircraft industry to enhance fatigue life of structural components containing holes. CX introduces compressive hoop residual stresses that slow crack growth near the hole edge. The objective of this paper is to predict residual stresses arising from cold expansion using two different finite element (FE) approaches, and compare the results to measurement data obtained by the contour method. The paper considers single-hole, double-hole, and triple-hole configurations with three different edge margins. The first FE approach considers process modeling, and includes elastic–plastic behavior, while the second approach is based on the eigenstrain method, and includes only elastic behavior. The results obtained from the FE models are in good agreement with one another, and with measurement data, especially close to the holes, and with respect to the effect of edge margin on the residual stress distributions. The distribution of the residual stress and equivalent plastic strain around the holes is also explored, and the results are discussed in detail. The eigenstrain method was found to be very useful, providing generally accurate predictions of residual stress.

Simulation of Quenching in Aluminium and Comparison With Neutron Diffraction Measurements

2008 ◽  
Author(s):  
R. J. Dennis ◽  
S. Phillips ◽  
C. E. Truman ◽  
A. Stiles ◽  
R. Plant
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Finite Element ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Finite Element Methods ◽  
Test Specimen ◽  
Internal Diameter ◽  
Linear Finite Element ◽  
Quenching Process

The through life integrity of engineering components are routinely assessed using complex finite element methods. A critical input to such an assessment is an understanding of the operating environment, including service loading and temperature. Significant effort is expended identifying and understanding the effect of service loads on component integrity however there are many cases where service loading in isolation cannot account for premature failure of components during testing or in-service. A key assumption is that components in the as-built condition are often treated as stress and defect free and of nominal dimensions. This approach can however be inadequate and there are many documented cases where residual stress has influenced the in-service integrity of components. In this paper the magnitude and distribution of residual stresses are investigated in a quenched Aluminium 2014A TB test specimen. The test specimen has been specifically designed to contain design features representative of pressurised aerospace components which are quenched during manufacture. The specimen has two sections, one cylindrical (65mm internal diameter) and one oval (125mm largest internal diameter). The outer wall thickness is 10mm and the overall specimen length is 200mm with the two sections joined by a 30mm bridge section. The specimen has been subject to solution heat treatment at 505°C for five hours. Following heat treatment the specimen is rapidly quenched in cold water at 10°C with the cylindrical end entering the water first. Non-linear finite element methods have been developed to simulate the quenching process making use of user defined subroutines to enhance the standard features available in the finite element code. The accuracy of the predicted residual stresses has been assessed by comparison with neutron diffraction measurements at a range of critical locations. The work provides an extremely useful insight into how non-linear finite element methods can be successfully used to predict the residual stresses that are generated as a result of the quenching process. Where residual stresses are a potential integrity concern an understanding of the magnitude and spatial distribution of residual stress can be used to influence both the design and in-service operation of components.

Residual Stress Distribution in Hard-Facing of Pressure Relief Valve Seat

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Li Ai ◽  
Xinhai Yu ◽  
Wenchun Jiang ◽  
Wanchuck Woo ◽  
Xiaofeng Ze ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Infrared Imaging ◽  
Element Model ◽  
Pressure Relief Valve ◽  
Stress Distributions ◽  
Relief Valve ◽  
Pressure Relief

In this study, for the hard-facing of spring-loaded pressure relief valve seats, the residual stress distributions after the tungsten inert gas welding, (TIG) postwelded heat treatment and subsequent surface turning were investigated. The heat input parameters of welding were calibrated using an infrared imaging and thermocouples. The residual stress distributions were computed using three-dimensional finite element model. The neutron diffraction approach was employed to verify the finite element calculation. It is found that, the surface temperature during hard-facing welding shows a double ellipsoidal shape with the highest value of around 1570 °C. The high residual stress zones are located exactly under the welded joint except a slight deviation in the hoop direction. The magnitudes of tensile residual stresses in the three directions increase with their corresponding locations from the root of the joint into the base metal. The residual stresses in all of the three directions decrease significantly after the heat treatment. After surface turning, the residual stresses are tensile except for those close to the inner surface that are compressive in axial and radial directions.

Optimising Residual Stress Measurements and Predictions in a Welded Benchmark Specimen: A Review of Phase 2 of the NeT Task Group 1 Single Bead on Plate Round Robin

2009 ◽  
Author(s):  
Michael C. Smith ◽  
Ann C. Smith ◽  
Robert C. Wimpory ◽  
Carsten Ohms ◽  
Brahim Nadri ◽  
...  
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
High Temperature ◽  
Residual Stresses ◽  
Constitutive Models ◽  
Finite Element Simulations ◽  
Task Group ◽  
Phase 2 ◽  
Inelastic Strains ◽  
Group 1

A single weld bead deposited on a flat plate is a deceptively simple problem that is in practice a challenge for both measurement and prediction of weld residual stresses. Task Group 1 of the NeT collaborative network has examined this problem in a two-phase programme extending from 2002 to 2008. Ten independent sets of residual stress measurements have been reported using diverse techniques, and over forty finite element simulations have been performed. This paper reviews Phase 2 of the Task Group 1 round robin. Here, the finite element simulations all made use of optimised thermal solutions, in which the global welding parameters, including efficiency, were fixed, and only the detailed heat source geometry was varied. These resulted in accurate far field welding temperature distributions, with significant variability only close to the weld bead itself. The subsequent mechanical analyses made use of kinematic, isotropic, and mixed isotropic-kinematic material constitutive models, and made a variety of assumptions about the introduction of weld filler material to the structure and the handling of high temperature inelastic strains. The large database of measurements allowed the derivation of statistical best estimates using a Bayesian “duff data” approach, and these best estimates were compared with the predictions to establish the most accurate material constitutive models. The most accurate predictions of residual stress were made using non-linear kinematic or mixed isotropic-kinematic constitutive models. The methods used to handle high-temperature inelastic strains influenced the predicted stresses only in regions where very high temperatures were predicted during welding. The results emphasise the importance and value of both well-characterised benchmark problems and international collaboration in the development of technologies to both measure and predict weld residual stresses.

scholarly journals Residual Stress Measurements in Mo/CuCrZr Tiles Using Neutron Diffraction

2008 ◽  
Vol 59 ◽  
pp. 299-303
Author(s):  
K. Mergia ◽  
Marco Grattarola ◽  
S. Messoloras ◽  
Carlo Gualco ◽  
Michael Hofmann
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Heat Sink ◽  
High Yield ◽  
Fusion Reactors ◽  
Plasma Facing Components ◽  
Induced Stresses ◽  
Compliant Layer

In plasma facing components (PFC) for nuclear fusion reactors tungsten or carbon based tiles need to be cooled through a heat sink. The joint between the PFC and the heat sink can be realized using a brazing process through the employment of compliant layer of either a low yield material, like copper, or a high yield material, like molybdenum. Experimental verification of the induced stresses during the brazing process is of vital importance. Strains and residual stresses have been measured in Mo/CuCrZr brazed tiles using neutron diffraction. The strains and stresses were measured in Mo tile along the weld direction and at different distances from it. The experimental results are compared with Finite Element Simulations.

scholarly journals Residual Stress State of X65 Pipeline Girth Welds Before and After Local and Furnace Post Weld Heat Treatment

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Yao Ren ◽  
Anna Paradowska ◽  
Bin Wang ◽  
Elvin Eren ◽  
Yin Jin Janin
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Residual Stresses ◽  
Outer Surface ◽  
Post Weld Heat Treatment ◽  
Pipe Length ◽  
Stress Profiles ◽  
Girth Welds ◽  
Welded Pipe ◽  
Weld Heat

This research investigated the effects of global (in other words, furnace-based) and local post weld heat treatment (PWHT) on residual stress (RS) relaxation in API 5L X65 pipe girth welds. All pipe spools were fabricated using identical pipeline production procedures for manufacturing multipass narrow gap welds. Nondestructive neutron diffraction (ND) strain scanning was carried out on girth welded pipe spools and strain-free comb samples for the determination of the lattice spacing. All residual stress measurements were carried out at the KOWARI strain scanning instrument at the Australian Nuclear Science and Technology Organization (ANSTO). Residual stresses were measured on two pipe spools in as-welded condition and two pipe spools after local and furnace PWHT. Measurements were conducted through the thickness in the weld material and adjacent parent metal starting from the weld toes. Besides, three line-scans along pipe length were made 3 mm below outer surface, at pipe wall midthickness, and 3 mm above the inner surface. PWHT was carried out for stress relief; one pipe was conventionally heat treated entirely in an enclosed furnace, and the other was locally heated by a flexible ceramic heating pad. Residual stresses measured after PWHT were at exactly the same locations as those in as-welded condition. Residual stress states of the pipe spools in as-welded condition and after PWHT were compared, and the results were presented in full stress maps. Additionally, through-thickness residual stress profiles and the results of one line scan (3 mm below outer surface) were compared with the respective residual stress profiles advised in British Standard BS 7910 “Guide to methods for assessing the acceptability of flaws in metallic structures” and the UK nuclear industry's R6 procedure. The residual stress profiles in as-welded condition were similar. With the given parameters, local PWHT has effectively reduced residual stresses in the pipe spool to such a level that it prompted the thought that local PWHT can be considered a substitute for global PWHT.

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