Annealing Models in Welding Simulation: Conservative and Non-Conservative Residual Stress Distributions

2010 ◽  
Author(s):  
Mike Keavey ◽  
Alison Mark ◽  
Hui Dai ◽  
Philip J. Withers
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Structural Integrity ◽  
Welding Process ◽  
Short Time Scale ◽  
Stress Distributions ◽  
Welding Simulation ◽  
Annealing Effects ◽  
Assessment Procedures ◽  
Integrity Assessments

The influence of residual stress on degradation mechanisms must be taken into account when performing structural integrity assessments. Conservative hypothetical distributions are often assumed, in which the maximum stress is equal to yield. Finite element simulation is now being used in an attempt to derive more realistic residual stress profiles for incorporation into assessment procedures. It is now possible to include self-annealing effects in finite element simulations of the welding process, whereby stresses in existing material in the immediate vicinity of a weld pass are relaxed locally on a very short time scale. Annealing models used in practice vary in sophistication from a simple erasure of strain hardening history at a particular temperature, through certain non-physical assumptions about temperature dependence, to phenomenological models based on the assumed kinetics of underlying microstructural processes. Even more sophisticated models based on thermodynamical principles have been proposed. The original incentive for developing such models was the hope that peak residual stress predictions within the weld and heat affected zone would be reduced, removing the need for over-conservative assumptions when performing structural integrity assessments. Preliminary 2-D results using a model developed by one of the authors, however, suggest that peak stresses predicted with annealing may actually be higher, the hypothesis being that it is compressive stresses that are relaxed during the welding cycle, and that the final tensile residual stresses are increased via the Bauschinger effect. This paper considers results from a further 3-D welding simulation and looks a little more closely at different annealing models. A number of different modelling approaches to annealing are described, together with the basic modelling parameters used to simulate a weld that has been the subject of various European round-robins, both theoretical and experimental. A brief overview of how a kinetics based model can be implemented in a finite element code is also presented. Predicted residual stress distributions are compared with each other and with neutron diffraction measurements and conclusions drawn.

Study on Weld Residual Stress and Crack Propagation Evaluations for a Saddle-Shaped Weld Joint

2013 ◽  
Author(s):  
Jinya Katsuyama ◽  
Koichi Masaki ◽  
Kunio Onizawa
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Weld Joint ◽  
Power Plants ◽  
Structural Integrity ◽  
Piping System ◽  
Stress Distributions ◽  
Analysis Model ◽  
Element Analysis ◽  
Weld Residual Stress

Stress corrosion cracking (SCC) have been observed in reactor coolant pressure boundary piping system at nuclear power plants. When an SCC is found, the structural integrity of piping should be assessed according to a fitness-for-service rule. However, the rule stipulates the assessment procedures for crack growth and failure only for a simple structure such as cylindrical or plate-wise structure. At the present, the methodology even of an SCC growth evaluation for a geometrically complicated piping such as saddle-shaped weld joints has not been established yet. This may be because analyses on the weld residual stress distribution which affects the SCC growth behavior around such portion are difficult to conduct. In this study, we established a finite element analysis model for a saddle-shaped weld joint of pipes. The residual stress distributions produced by the tungsten inert gas (TIG) welding were calculated based on thermal-elastic-plastic analysis with moving and simultaneous heat source models. Analysis results showed complicated weld residual stress distributions, i.e., residual stresses in both hoop and radial directions were tensile at the inner surface near the nozzle corner in branching pipe. SCC growth simulation based on S-version finite element method (S-FEM) using the weld residual stress distributions in saddle-shaped weld joint was also performed. We confirmed an applicability and the accuracy of S-FEM to saddle-shaped weld joint.

scholarly journals Finite Element Prediction of Residual Stress Distributions in a Multipass Welded Piping Branch Junction

2006 ◽  
Author(s):  
Wei Jiang ◽  
Kadda Yahiaoui
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Welding Process ◽  
Pressure Vessels ◽  
Welding Residual Stress ◽  
Stress Distributions ◽  
Multipass Welding ◽  
Hexahedral Elements ◽  
Element Removal

Piping branch junctions and nozzle attachments to main pressure vessels are common engineering components used in the power, oil and gas, and shipbuilding industries amongst others. These components are usually fabricated by multipass welding. The latter process is known to induce residual stresses at the fabrication stage which can have severe adverse effects on the in-service behavior of such critical components. It is thus desirable if the distributions of residual stresses can be predicted well in advance of welding execution. This paper presents a comprehensive study of three dimensional residual stress distributions in a stainless steel tee branch junction during a multipass welding process. A full 3D thermo-mechanical finite element model has been developed for this purpose. A newly developed meshing technique has been used to model the complex intersection areas of the welded junction with all hexahedral elements. Element removal/reactivate technique has been employed to simulate the deposition of filler material. Material, geometry and boundary nonlinearities associated with welding were all taken into account. The analysis results are presented in the form of stress distributions circumferentially along the weldline on both run and branch pipes as well as at the run and branch cross sections. In general, this computational model is capable of predicting 3D through thickness welding residual stress, which can be valuable for structural integrity assessments of complex welded geometries.

The Validation of Weld Residual Stresses for Use in Structural Integrity Assessment

2011 ◽  
Vol 70 ◽  
pp. 297-302 ◽  
Author(s):  
Steve K. Bate ◽  
P. John Bouchard
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Measurement Techniques ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Modelling Techniques ◽  
High Level ◽  
Assessment Procedures

The continued safe and reliable operation of plant invariably has to consider the assessment of defects in welded structural components. This requires some estimate of the residual stresses that have developed during the welding fabrication process. For as-welded structures these stresses can be of yield magnitude. Engineering critical assessment procedures such as R6, BS 7910, FITNET and API 579-1 provide simplified estimates, bounding profiles or advice on detailed analysis or measurement which can be applied to provide conservative estimates of the remaining life of plant. The use of finite element analysis (FEA) is being applied more frequently to predict residual stresses in welded components for assessment purposes. This calculation involves complex non-linear analyses with many assumptions. As a consequence, the accuracy and reliability of solutions is variable. In order to improve the consistency of weld modelling, and hence the accuracy and confidence in their use, a set of Guidelines covering the calculation of residual stresses have been developed. The residual stress calculations need to be validated before the results can be used in assessments and guidance on how to demonstrate the required standard of validation proof is provided with these Guidelines. The level of validation required, depends on the problem being solved and the sensitivity of the assessment to the presence of residual stress. For example a high level of validation may be required for assessments of safety critical plant. To support these calculations, measurements are required and a series of ‘Weld Residual Stress Benchmarks’, describing welded mock-ups which have been measured using various measurement techniques, are being collated which the users can then refer to when validating their finite element modelling techniques and thus provide a greater confidence in the predicted results.

Study on Welding Deformation and Residual Stress of H-Section Beam Based on Finite Element Method

2017 ◽  
Vol 753 ◽  
pp. 305-309 ◽  
Author(s):  
Xu Lu
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Finite Element ◽  
Source Parameters ◽  
Welding Process ◽  
Steel Structure ◽  
Bottom Plate ◽  
Welding Deformation ◽  
Element Simulation ◽  
Main Components

The welding H-section beam has good mechanical properties with its superior structure. So they become the main components of steel structure and have been widely used. In this paper, the welded H-section beam is used as the research object. The finite element simulation model is established. The heat source parameters are determined. The deformation of the steel due to the welding process is studied. The results show that the bottom plate and the bottom plate inward bending is about 2.32mm cause by welding process. The residual stress can reach 400MPa.

scholarly journals X-ray nanodiffraction analysis of stress oscillations in a W thin film on through-silicon via

2016 ◽  
Vol 49 (1) ◽  
pp. 182-187 ◽  
Author(s):  
J. Todt ◽  
H. Hammer ◽  
B. Sartory ◽  
M. Burghammer ◽  
J. Kraft ◽  
...  
Keyword(s):  
Thin Film ◽  
Residual Stress ◽  
Finite Element ◽  
Diffraction Data ◽  
Element Model ◽  
Stress Distributions ◽  
Through Silicon Via ◽  
X Ray ◽  
Tangential Stresses ◽  
Stress Components

Synchrotron X-ray nanodiffraction is used to analyse residual stress distributions in a 200 nm-thick W film deposited on the scalloped inner wall of a through-silicon via. The diffraction data are evaluated using a novel dedicated methodology which allows the quantification of axial and tangential stress components under the condition that radial stresses are negligible. The results reveal oscillatory axial stresses in the range of ∼445–885 MPa, with a distribution that correlates well with the scallop wavelength and morphology, as well as nearly constant tangential stresses of ∼800 MPa. The discrepancy with larger stress values obtained from a finite-element model, as well as from a blanket W film, is attributed to the morphology and microstructural nature of the W film in the via.

Numerical Methods to Predict Distortion in Welded Components

2008 ◽  
Author(s):  
N. A. Leggatt ◽  
R. J. Dennis ◽  
P. J. Bouchard ◽  
M. C. Smith
Keyword(s):  
Residual Stress ◽  
Numerical Methods ◽  
Structural Integrity ◽  
Large Strain ◽  
Stress Fields ◽  
Specimen Thickness ◽  
Single Bead ◽  
Stress Profiles ◽  
Welding Processes ◽  
Integrity Assessments

Numerical methods have been established to simulate welding processes. Of particular interest is the ability to predict residual stress fields. These fields are often used in support of structural integrity assessments where they have the potential, when accurately characterised, to offer significantly less conservative predictions of residual profiles compared to those found in assessment codes such as API 579, BS7910 and R6. However, accurate predictions of residual stress profiles that compare favourably with measurements do not necessarily suggest an accurate prediction of component distortions. This paper presents a series of results that compare predicted distortions for a variety of specimen mock-ups with measurements. A range of specimen thicknesses will be studied including, a 4mm thick DH-36 ferritic plate containing a single bead, a 4mm thick DH-36 ferritic plate containing fillet welds, a 25mm thick 316L austenitic plate containing a groove weld and a 35mm thick esshete 1250 austenitic disc containing a concentric ring weld. For each component, distortion measurements have been compared with the predicted distortions with a number of key features being investigated. These include the influence of ‘small’ vs ‘large’ strain deformation theory, the ability to predict distortions using simplified analysis methods such as simultaneous bead deposition and the influence of specimen thickness on the requirement for particular analysis features. The work provides an extremely useful insight into how existing numerical methods used to predict residual stress fields can be utilised to predict the distortions that occur as a result of the welding fabrication process.

Review of the Current Conservatisms in the Assessment of Thin-Walled Structures

2009 ◽  
Author(s):  
R. S. Kulka ◽  
A. J. Price
Keyword(s):  
Fracture Mechanics ◽  
Best Practice ◽  
Structural Integrity ◽  
Fracture Behaviour ◽  
Stress Distributions ◽  
Limit Loads ◽  
Thin Walled Structures ◽  
Commercial Drivers ◽  
Thin Walled ◽  
Integrity Assessments

Current methods for performing fracture mechanics assessments of thin-walled structures possess significant levels of conservatism, since they are often for general use with both thin-walled and thick-walled structures. In many industries, there are significant commercial drivers for reducing the amount of conservatism in these assessments. An enhanced understanding of the fracture behaviour of thin-walled structures in different situations may lead to the development of more appropriate structural integrity assessments. A review of the information pertaining to fracture mechanics analysis of thin-walled structures has been conducted. There are indications that improvements to the best practice methodology may be made, through improved tensile and toughness properties, consideration of limit loads, and the effect of residual stress distributions.

Finite Element Analysis Model of Corrosion Fatigue for TIG Welding Workpiece

2016 ◽  
Vol 707 ◽  
pp. 154-158
Author(s):  
Somsak Limwongsakorn ◽  
Wasawat Nakkiew ◽  
Adirek Baisukhan
Keyword(s):  
Residual Stress ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Corrosion Fatigue ◽  
Welding Process ◽  
Simulation Software ◽  
Tig Welding ◽  
Element Analysis ◽  
Fea Model

The proposed finite element analysis (FEA) model was constructed using FEA simulation software, ANSYS program, for determining effects of corrosion fatigue (CF) from TIG welding process on AISI 304 stainless steel workpiece. The FEA model of TIG welding process was developed from Goldak's double ellipsoid moving heat source. In this paper, the residual stress results obtained from the FEA model were consistent with results from the X-ray diffraction (XRD) method. The residual stress was further used as an input in the next step of corrosion fatigue analysis. The predictive CF life result obtained from the FEA CF model were consistent with the value obtained from stress-life curve (S-N curve) from the reference literaturature. Therefore, the proposed FEA of CF model was then used for predicting the corrosion fatigue life on TIG welding workpiece, the results from the model showed the corrosion fatigue life of 1,794 cycles with testing condition of the frequency ( f ) = 0.1 Hz and the equivalent load of 67.5 kN (equal to 150 MPa) with R = 0.25.

Estimation of Residual Stresses in Steel Welded Joints Using Three Dimensional Finite Element Analysis

2018 ◽  
Author(s):  
Shivdayal Patel ◽  
B. P. Patel ◽  
Suhail Ahmad
Keyword(s):  
Residual Stress ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Residual Stresses ◽  
Boundary Conditions ◽  
Welding Speed ◽  
Welded Joints ◽  
Plate Thickness ◽  
Welding Process ◽  
Element Analysis

Welding is one of the most used joining methods in the ship industry. However, residual stresses are induced in the welded joints due to the rapid heating and cooling leading to inhomogenously distributed dimensional changes and non-uniform plastic and thermal strains. A number of factors, such as welding speed, boundary conditions, weld geometry, weld thickness, welding current/voltage, number of weld passes, pre-/post-heating etc, influence the residual stress distribution. The main aim of this work is to estimate the residual stresses in welded joints through finite element analysis and to investigate the effects of boundary conditions, welding speed and plate thickness on through the thickness/surface distributions of residual stresses. The welding process is simulated using 3D Finite element model in ABAQUS FE software in two steps: 1. Transient thermal analysis and 2. Quasi-static thermo-elasto-plastic analysis. The normal residual stresses along and across the weld in the weld tow region are found to be significant with nonlinear distribution. The residual stresses increase with the increase in the thickness of the plates being welded. The nature of the normal residual stress along the weld is found to be tensile-compressive-tensile and the nature of normal residual stress across the weld is found to be tensile along the thickness direction.

FE Predictions of Temperature Distributions in a Multipass Welded Piping Branch Junction

2004 ◽  
Author(s):  
Wei Jiang ◽  
Kadda Yahiaoui ◽  
Chang J. Wang ◽  
Frank R. Hall ◽  
Tahar Laoui
Keyword(s):  
Residual Stress ◽  
Welding Process ◽  
Stress Distributions ◽  
Temperature Dependent ◽  
Material Microstructure ◽  
Temperature Distributions ◽  
Control Schemes ◽  
Complex Temperature ◽  
Walled Cylinder ◽  
Comprehensive Study

This contribution deals with the complex temperature profiles that are generated by the welding process in the intersection region of thick walled, cylinder-cylinder junctions. These affect material microstructure, mechanical properties and residual stresses. Knowledge of the thermal history and temperature distributions are thus critical in developing control schemes for acceptable residual stress distributions to improve in-service component behavior. A comprehensive study of 3D temperature distributions in a stainless steel tee branch junction during a multipass welding process is presented. A newly developed partitioning technique has been used to mesh the complex intersection areas of the welded junction. Various phenomena associated with welding, such as temperature dependent material properties, heat loss by convection and latent heat have been taken into consideration. The temperature distribution at various times after deposition of certain passes and the thermal cycles at various locations are reported. The results obtained in this study will be used for on-going and future analysis of residual stress distributions. The meshing technique and modeling method can also be applied to other curved, multipass welds in complex structures.

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