Evaluation of through-thickness residual stresses and microstructure in SA516 Gr. 70 steel welds

2021 ◽  
pp. 095440542199012
Author(s):  
Pradeeptta Kumar Taraphdar ◽  
Manas Mohan Mahapatra ◽  
Arun Kumar Pradhan ◽  
Pavan Kumar Singh ◽  
Kamal Sharma ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Nuclear Power ◽  
Three Dimensional ◽  
Welding Process ◽  
Influential Factors ◽  
Stress Fields ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Steel Welds

The critical working condition of nuclear power plant equipment necessitates meticulous determination of the welding process and parameters. In this work, some major influential factors of welding were investigated to observe their effects on the through-thickness residual stress distribution in multipass pressure vessel steel welds. In this regard, experiments were conducted to find the characteristics of residual stresses dispersed in SA516 Grade 70 steel welds of different groove geometries with distinct welding conditions. Three-dimensional finite element models of the weldments were developed considering a moving heat source with temperature-dependent material properties to simulate the welding thermal cycles and corresponding residual stress fields. Effects of weld groove geometry, number of weld passes, external constraints, and preheating on the through-thickness residual stress fields were studied. Additional attention was given to the evaluation of the heterogeneous microstructure and microhardness across the weld cross-section associated with their weld thermal history. Finally, the evolution of the through-thickness residual stresses attributed to subsequent weld passes was elaborated.

Finite Element Simulation of Laser Welding in a P91 Steel Plate

2013 ◽  
Author(s):  
Kiranmayi Abburi Venkata ◽  
Christopher E. Truman
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Laser Welding ◽  
Nuclear Power ◽  
Power Plants ◽  
Welding Process ◽  
P91 Steel ◽  
Modelling Techniques ◽  
Materials Used ◽  
Steel Welds

New methods for joining materials used in advanced nuclear power plants are of interest to increase the efficiency and productivity. Optimised joints require narrow heat affected zones, low residual stress, strain and distortion. This requires research into a large range of aspects including the nature of the joining processes, characterisation of the joint materials and the integrity of joints in manufacture and service. Of particular interest is the laser welding of the P91 steel used extensively in the power plants. The objective of this paper is to fully characterise the laser welding process using numerical modelling techniques and compare the measured residual stresses for P91 steel welds induced by the welding process with the predicted residual stresses by numerical simulation. The FE simulation consists of thermal analysis and a sequentially coupled structural analysis. Solid state phase transformation is included in the analysis to account for the volumetric changes due to martensitic transformation during cooling. The neutron diffraction technique is used to measure the residual stresses in the welded plate. The measurements are compared with the simulation results and the characteristics of the residual stress distribution and the influence of phase transformations are discussed.

Influence of Cooling Rate on Predicted Weld Residual Stress Buildup in a Thick-Walled Piping Intersection

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Wei Jiang ◽  
Kadda Yahiaoui
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Cooling Rate ◽  
Nuclear Power ◽  
Three Dimensional ◽  
Modeling Technique ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Residual Stress State ◽  
External Cooling

Welded, thick-walled piping intersections are widely used in many engineering applications including the offshore and nuclear power industries. These components are often fabricated by multipass welding, which inevitably introduces undesirable residual stresses. In this paper, weld-induced residual stresses in a thick-walled piping intersection were predicted using a validated, full three dimensional, sequentially coupled thermomechanical finite element modeling technique. The moving heat source was simulated by imposing body heat flux onto the newly activated elements progressing along the circumferential weld path around the intersection during each pass. The effect of cooling rate on the final residual stress state, especially at critical areas where the peak residual stresses are located, was then investigated by applying different convective heat transfer coefficients to the exposed piping intersection surfaces. It was found that the magnitudes and overall spatial distributions of residual stresses were very sensitive to cooling rate. Residual stresses on the outer surfaces of the component can be significantly reduced by external cooling. On the other hand, cooling the inner surfaces can dramatically convert residual stresses from tensile to compressive in these regions. The results and modeling technique presented in this paper show that residual stress profiles in multipass welded complex geometries can be efficiently optimized through convenient cooling rate control.

Influence of the Welding Sequence on Residual Stresses in Laser Welded T-Joints of an Airframe Aluminium Alloy

2008 ◽  
Vol 571-572 ◽  
pp. 375-380 ◽  
Author(s):  
Winulf Machold ◽  
Peter Staron ◽  
Funda S. Bayraktar ◽  
Stefan Riekehr ◽  
Mustafa Koçak ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Welding Process ◽  
Base Plate ◽  
Stress Fields ◽  
Stress Concentrations ◽  
T Joints ◽  
Element Simulation ◽  
Welding Sequence ◽  
Welding Sequences

The effect of different welding sequences between a 4.5 mm thick AA 6156 T6 base plate and a 2 mm thick AA 6013 T6 clip – resembling a skin-clip joint of an airframe – using a 3.3 kW Nd:YAG laser is investigated. Under cyclic loading the breakdown of such T-joints happens at one end of the clip, which is due to local residual stress concentrations. Recent measurements indicated that tensile stresses could be lower at the run-in than at the run-out locations. For a deeper investigation of this effect sheets with different welding sequences were produced. One welding sequence was made with two starting points in the centre, and a second with starting points at the clip ends. Temperature measurements were made using thermocouples to verify the heat conditions for a finite element simulation of the welding process, which is used for predictions of the residual stress distribution. Actual values of the residual stress fields were determined by neutron diffraction. The influences of the welding sequence on the measured temperatures and the residual stresses are discussed.

A Numerical Study on Mock-Up Downsizing to Predict Residual Stresses at CRDM Welds

2010 ◽  
Author(s):  
Ik-Joong Kim ◽  
Jae-Uk Jeong ◽  
Jae-Boong Choi ◽  
Young-Jin Kim ◽  
Sung-Woo Kim ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Nuclear Power ◽  
Power Plants ◽  
Numerical Study ◽  
Welding Process ◽  
Piping System ◽  
Experimental Conditions ◽  
Control Rod ◽  
Set Up

Since several defects caused by PWSCC (Primary Water Stress Corrosion Cracking) have been observed at the piping system of nuclear power plants, during the last two decades, lots of analytical and experimental researches have been performed to find out the relationship between the residual stress and PWSCC initiations. The present research deals with prediction of the residual stress at welding parts of CRDM (Control Rod Drive Mechanism). Especially, numerical investigations are carried out to support relevant experimental set-up because it is not easy to prepare large-sized mock-ups comparable to real geometry. First, preliminary examination was performed to establish an optimized welding process simulation procedure to accurately predict weld residual stresses. Then, detailed parametric FE analyses were carried out to examine effects of varying geometries and experimental conditions. Key findings were obtained from the FE analyses, which were used for finalizing the configuration of mock-up, are fully discussed in this manuscript.

Residual Stress Fields Under Different Clamping Conditions in Circumferentially Welded Thin-Walled Cylinders

2008 ◽  
Author(s):  
Afzaal M. Malik ◽  
Ejaz M. Qureshi ◽  
Naeem Ullah Dar ◽  
Iqbal Khan
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Nuclear Power ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Stress Fields ◽  
Shop Floor ◽  
High Tech ◽  
Thin Walled

Arc welding is a reliable joining method widely utilized in nuclear, pressure vessels, aerospace and aeronautical structures to ensure the intended in service behaviour during the thermal and/or pressure loadings. Weld induced deformations and high residual stresses often occur during the course of welding. These cause significant threats for the structural integrity of the nuclear power plant components, particularly in stress corrosion inhibited environments owing to the risk of stress corrosion cracking (SCC). In this research, the consequences of five different structural boundary conditions on the evolution of residual stress fields after the welding are investigated. Both experimental and numerical simulations based on finite element modeling are employed during the course of investigation. Full three-dimensional FE models for the circumferentially, arc welded thin-walled cylinders are developed in ANSYS®. The complex coupled, thermo-mechanical phenomenon during the welding is simulated by sequentially coupled approach enhanced by user written APDL subroutines. The role of welding restraints in minimizing / optimizing the residual stresses is presented and discussed in detail. The result reveals that residual stresses show weak dependence on the degree of the restraints. Although the stress levels slightly varies in magnitude, but similar trend is observed for all the structural clamping conditions under study. Simulation results validated through full-scale experiments with high-tech reliably instrumented welding and measuring equipments shows promising features of the developed modelling and simulation strategy for use in shop floor applications.

Design and Manufacture of Welded Plate Specimens for Residual Stress Experiments

2008 ◽  
Author(s):  
P. R. Hurrell ◽  
K. Bridger ◽  
P. Bunney ◽  
C. Gill ◽  
J. A. Francis ◽  
...  
Keyword(s):  
Residual Stress ◽  
Mechanical Behaviour ◽  
Pressure Vessel ◽  
Ferritic Steel ◽  
Steel Plates ◽  
Welding Parameters ◽  
Pressure Vessel Steel ◽  
Welding Temperature ◽  
Vessel Steel ◽  
Steel Welds

A long-term UK research programme has been established in order to improve the understanding of thermo-mechanical behaviour and residual stresses generated in pressure vessel steel welds as well as developing finite element (FE) welding simulation methods. The production of representative test specimens is an important element of this research project, since quality measurement data are needed to validate FE models. This paper describes the design, development and manufacture of welded plate specimens used for residual stress (RS) experiments. To date, research has focused mainly on developing the understanding of SA508 pressure vessel steel welds. Specimen dimensions were selected to facilitate stress measurements using a range of techniques. The philosophy adopted was to start with relatively simple 1-pass weld specimens and gradually increase the complexity to multi-pass groove welds in plates. Simple 1-pass weld specimens were generally designed to investigate the effect of welding parameters on thermo-mechanical behaviour, such as heat-affected zone (HAZ) microstructures and phase transformations. Later specimens are more representative of multi-pass power plant welds. They are being used to study material thermal cyclic hardening/softening behaviour. Other issues of concern are also being investigated, such as the effect of restraint during welding on RS and the effectiveness of post weld heat treatment (PWHT). Specimens were also designed to study peak stresses arising at bead stop/start positions and whether such peak stresses are annealed in overlaying additional weld metal. These investigations were performed on multi-pass groove welds in both austenitic and ferritic steel plates. Practical issues encountered during welding trials are discussed, including plate distortion and magnetisation of the ferritic steel plates. Information is also provided about welding temperature measurements and metallurgical examinations.

Computational Models for Resistance Spot Welding

2012 ◽  
Author(s):  
Pierluigi Mollicone ◽  
Martin Muscat ◽  
Matthew Said
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Spot Welding ◽  
Large Scale ◽  
Computational Models ◽  
Computational Modelling ◽  
Welding Process ◽  
Stress Fields ◽  
Modelling Technique ◽  
Hole Drilling

Spot welding is a very important joining process for many industries. Structural integrity of a spot welded joint is however compromised by the formation of residual stress fields, which arise due to the thermal loadings imposed on the material during this welding process. Experimental investigation of these effects is possible but often costly, especially in complex and large-scale applications. Computational models, through the application of advanced Finite Element Analysis (FEA) techniques, are hence of interest for the prediction, analysis and assessment of these effects. The computational modelling required to assess these effects is however relatively complex due to the interaction of thermal and structural solution fields. It follows that many decisions must be taken with regards to the modelling technique to adopt in these scenarios. This work presents a modelling technique for the prediction of spot welding induced residual stresses, validated with experimental measurements for the temperature and residual stress fields. The simulations, carried out in ANSYS, are aimed at using a general-purpose solver to predict residual stresses whilst the validation is carried out through transient thermocouple measurements and residual stress measurements done using the hole drilling method. Comparison of experimental and FEA model results highlight which parts and assumptions of the computational model are to be considered valid and hence its boundary for use in industry.

Influence of Cooling Rate on Predicted Weld Residual Stress Build-Up in a Thick Walled Piping Intersection

2008 ◽  
Author(s):  
Wei Jiang ◽  
Kadda Yahiaoui
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Cooling Rate ◽  
Nuclear Power ◽  
Three Dimensional ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Residual Stress State ◽  
External Cooling ◽  
Element Simulation

Welded, thick-walled piping intersections are widely used in many engineering applications including the offshore and nuclear power industries. These components are often fabricated by multipass welding which inevitably introduces undesirable residual stresses. In this contribution, weld-induced residual stresses in a thick-walled piping intersection were predicted using a validated, full three dimensional, sequentially coupled thermo-mechanical finite element simulation. The effect of cooling rate on the final residual stress state, especially at critical areas where the peak residual stresses are located, was then investigated by applying different convective heat transfer coefficients to the exposed piping intersection surfaces. It was found that the magnitudes and overall spatial distributions of residual stresses were very sensitive to cooling rate. Residual stresses on the outer surfaces of the component can be significantly reduced by external cooling. On the other hand, cooling the inner surfaces can dramatically convert residual stresses from tensile to compressive in these regions. The results and modeling technique presented in this contribution show that residual stress profiles in multipass welded complex geometries can be efficiently optimized through convenient cooling rate control.

Overview of Welding Research Under the New Nuclear Manufacturing (NNUMAN) Programme

2014 ◽  
Author(s):  
B. Jeyaganesh ◽  
M. D. Callaghan ◽  
J. A. Francis ◽  
P. D. English ◽  
A. Vasileiou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Residual Stresses ◽  
Numerical Models ◽  
Welding Process ◽  
High Energy ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Reactor Pressure Vessel Steel ◽  
Manufacturing Technologies ◽  
Welding Processes

The New Nuclear Manufacturing (NNUMAN) programme was established in the UK in late 2012, to develop new manufacturing technologies for nuclear components. One of the themes of this programme is research to develop candidate advanced joining methods using arc and high-energy welding processes, for components manufactured using nuclear grade reactor pressure vessel steel SA508 Grade 3 Class 1. The key outcomes of this study are the comparison of residual stresses and mechanical properties of welded mock-ups as a function of different welding processes, together with the development and validation of numerical models to predict residual stresses and mechanical properties. This paper gives an overview of the NNUMAN welding programme, coupled with design of experiments to date. The ultimate objective of this research is aimed at determining the effect of the selection of welding process, on the performance of nuclear components with operational lifetimes of 60 years or greater.

Simplified Computation of the Welding Process on a Steam-Generator Divider Plate

2013 ◽  
Author(s):  
Frédérique Rossillon ◽  
Lionel Depradeux
Keyword(s):  
Residual Stress ◽  
Steam Generator ◽  
Nuclear Power ◽  
Power Plants ◽  
Welding Process ◽  
Computation Time ◽  
Stress Fields ◽  
Residual Stress Field ◽  
Butt Weld ◽  
2D Simulation

The integrity of structures in nuclear power plants has to be assessed to meet given safety criteria. For a better understanding of the in-service loads in welded areas of PWRs components, the residual stresses resulting from the welding process have to be estimated. For that purpose, numerical simulations of welding have proved efficient but still require some improvement in terms of computation time reduction to be widely used in an industrial context. This paper focuses on the residual stress fields in a double V butt weld on a steam generator divider plate. To set a reference, a 2D simulation of multi-pass welding was performed taking into account the whole non-linear thermo-mechanical history. Two simplified method were then carried out to estimate the residual stress field. The first method consists of modeling macro-beads by merging passes together. The second considers only a reduced number of appropriately selected passes in the analysis. Both methods are confronted to the full multi-pass simulation, set as a reference simulation, and their respective efficiency and robustness are discussed. The main feature of this work, the RNP method, based on a reduced number of appropriately selected passes, gives a good reproduction of the stress fields and strongly reduce the computation time. A significant improvement is observed: CPU time is divided by 10 times with this predictive method.

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