Study of the Stress State of a Dissimilar Metal Weld Due to Manufacturing and Operational Conditions (original) (raw)
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Fracture and Structural Integrity, 2016
This paper summarizes the results of the through-thickness residual stress distributions on dissimilar metal weld (DMW) mock-up. DMWs, as welded joints between ferritic steels and either austenitic stainless steels or nickel-based alloys, are commonly found in piping systems of NPPs as well as in other industrial plants. The welding of the mock-up is simulated by the 3D finite element model using temperature and phase dependent material properties. The commercial finite element code MSC.Marc is used to obtain the numerical results by implementing the Goldak's double ellipsoidal shaped weld heat source and combined convection radiation boundary conditions. Residual stress measurements are performed on welded joints to validate the simulation results. The validated residual stress distributions can be used for the life time assessment and failure mode predictions of the welded joints.
The effect of thermal properties and weld efficiency on residual stresses in welding
Purpose: A parametric model is adopted and the technique of element “birth and death” is used to estimate theeffect of thermal properties and weld efficiency on residual stresses in butt weld joints.Design/methodology/approach: Residual stresses and distortions on butt welded joints are numericallyevaluated by means of finite element method. The FE analysis allows to highlight and evaluate the stress fieldand its gradient around the fusion zone of welded joints, higher than any other located in the surrounding area.Findings: The main conclusion is the significant effect of varying the value of the conductivity on residualstresses.Practical implications: Several experimental destructive and non destructive techniques for directly measuringresidual stress have been developed. However, the application of these methods in practice is usually limitedby either cost or accuracy. Numerical simulation based on finite element techniques, therefore, offers acomprehensive solution for the predi...
Influence of welding parameters on the welding residual stresses
2017
FE simulation of welds from austenitic steel was carried out in the current paper. Two different multi-pass welds were modelled. Measurements of welding residual stresses, which were found in literature, were applied for the validation of the results. The validated models were then used as basis for sensitivity analysis. The influence of differentiating the welding speed, the heat input of the weld heat source, intermediate cooling between consecutive weld-passes and welding sequence on the welding residual stresses was investigated.
2019
In this study, the experimental procedure of various welding processes has been explained and the variations in the various properties of weldment due to the influence of several welding parameters were studied. Here, the processes are common to all the conditions such as the welding conditions and material selection criterion. In the present paper, the focus is on presenting and classifying the specified welding process and the changes in the properties of weld in terms of varying parameters applied for welding process. This study allows putting them into proper context based on the new trends in the field of welding. Finally, the variations of the properties of weld with respect to various parameters, defects in weldment and stresses in weldment have been reviewed.
Welding residual stresses in ferritic power plant steels
Materials Science and Technology
Many of the degradation mechanisms relevant to power plant components can be exacerbated by stresses that reside within the material. Good design or structural integrity assessments require therefore, an accounting of residual stresses, which often are introduced during welding. To do this it is necessary to characterise the stresses, but this may not be possible in thick components using non-destructive methods. These difficulties, and a paucity of relevant engineering data, have led to an increasing emphasis on the development and validation of suitable modelling tools. Advances are prominent in the estimation of welding residual stresses in austenitic stainless steels. The progress has been less convincing in the case of ferritic alloys, largely due to the complexities associated with the solid state phase transformations that occur in multipass welding. We review here the metallurgical issues that arise in ferritic steel welds, relate these to the difficulties in calculating residual stresses, and highlight some stimulating areas for future research.
The prediction of residual stress and its influence on the mechanical properties of weld joint
A three-dimensional metallo-thermo-mechanical analysis of bead on plate welding is performed in this work. This coupled model enables to capture the microstructural development and temperature history at local region. As a result, the residual stress is evaluated based on the temperature-dependent mechanical properties computed by the mixture of individual phase. Isotropic hardening is assumed in the finite element (FE) analysis. At the same time, the distribution of residual stress is also predicted by treating the mechanical properties as integral values of sheet metal. The two simulated fields of stress and strain after welding are analysed and compared. Moreover, as it is known that welding changes the mechanical properties of the original material, especially in fusion zone (FZ) and heat affected zone (HAZ), the stress and strain data at interested areas (HAZ and FZ) are subtracted for comparison. The predicted stress and strain fields are imported to subsequent simulation of standard tensile test. The stress-strain curves are compared with the one of base material. It is found that residual stress has significant influence on the structural performance of weld joints.
Welding thermal stress diagrams as a means of assessing material proneness to residual stresses
Journal of Materials Science, 2020
In this work, the proposal and appraisal of a method to describe in a quantitative manner the phenomenon of thermal stresses formation in welding at different heat-affected zone (HAZ) regions and under different cooling rates, by means of physical simulation, are explained. Under the denomination of welding thermal stress diagrams (WTSD), initially the concept and experimental arrangements needed to use the idea, based on a Gleeble simulator, are revealed. An approach to determine more realistic thermal cycles (peak temperature and heating/cooling rates) is introduced and applied. The method assessment was carried out by using specimens of a HSLA quenchable steel subjected to different cooling rates (covering a wide range of typical welding heat inputs) and peak temperatures (representing regions progressively farther away from the fusion line). The different thermal stress (TS) curves proved the concept based on the justification of the results. In addition, it was physically demon...
A Study on Residual Stresses of Dissimilar Welding Joints
This research work focused on different types of dissimilar weld joints commonly used in refineries and chemical industries to investigate the magnitude, type and distribution of welding residual stresses in weld metal and HAZ at both face and root sides. These joints were combined from mild steel, stainless steel types 304 and 316, and Incoloy 800. For comparison, similar weld joints for each material were also studied. Stress relaxation or sectioning technique was used for welding residual elastic strain measurements using electrical strain gauges. The results of this study have shown that measured elastic strains of both face and root sides were different and this difference increased with the increase in plate thickness. Welding residual stresses of HAZ did not depend on joint type, it depended only on properties of base metal. A considerable difference in the value of welding residual stresses between similar and dissimilar pipe weld joints was obtained. However, both have shown almost similar trend of stress distributions.
2017
This paper describes work carried out under the NNUMAN research programme. This work focuses on the measurement and modelling of residual stresses in weld test pieces that have a thickness that is representative of primary components in a pressurised water reactor, such as the steam generators and the pressuriser. Weld test pieces at thicknesses of 30 mm and 130 mm have been and are being manufactured in SA508 Grade 3 Class 1 steel. Attention has been given to welding processes that are currently applied in nuclear manufacturing, such as narrow-groove arcbased welding processes, as well as to candidate processes for future build programmes, such as electron beam welding. The manufacture, characterisation and modelling of large test pieces each present challenges over and above those that arise when dealing with the smaller test pieces that are more typically manufactured in research laboratories. Some of those challenges, and the approaches that have been used to overcome them, are ...