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.

Key Technology Research of the Temperature Field Simulation Based on the Flat Butt Weld

2012 ◽  
Vol 562-564 ◽  
pp. 729-732 ◽  
Author(s):  
Yu Wen Li ◽  
Fu Xing Wang
Keyword(s):  
Residual Stress ◽  
Temperature Field ◽  
Stress Field ◽  
Field Distribution ◽  
Welding Process ◽  
Residual Stress Field ◽  
Butt Weld ◽  
Temperature Method ◽  
Simulation Based ◽  
Direct Loading

Aluminum as solder, in the flat welding process, the temperature field and the residual stress field distribution was the main problem of the study; According to the actual situation of the welding process, using the direct loading temperature method and the indirect loading temperature method , the main path of temperature field distribution curves and the residual stress field distribution were gained by 2D numerical simulation respectively; Through comparison, the indirect loading method can get more accuracy of residual stress field distribution than that of the direct loading temperature method; The above methods were useful in practical production.

A Study of Redistribution of Residual Stress and Hardness Due to Welding and Surface-Machining at Girth Welded Joint

2009 ◽  
Author(s):  
Masahito Mochizuki ◽  
Jinya Katsuyama ◽  
Ryohei Ihara ◽  
Hiroaki Mori ◽  
Yoshiki Mikami ◽  
...  
Keyword(s):  
Residual Stress ◽  
Nuclear Power ◽  
Power Plants ◽  
Crack Growth Behavior ◽  
Internal Diameter ◽  
Butt Weld ◽  
Butt Welding ◽  
Surface Machining ◽  
Inner Surface ◽  
Before And After

Stress corrosion cracking (SCC) near the welded zone of core internals and recirculation piping of Type 316L stainless steel in BWR nuclear power plants has been observed at the surface where tensile residual stress exists due to welding and/or surface-machining. It is well-known that butt-welding of austenitic piping causes the tensile stress in the inner surface of the pipe and that surface-machining is usually conducted before and after piping butt-welding to match the internal diameter (ID) of pipes and to provide a smooth surface finish but some amount of hardening. The SCCs near the welds of Ni-based alloys have been observed in the environment of primary water coolant, which is so called PWSCC. In this case, both residual stress and hardening are also the most important factors induced by welding as well as surface-machining in the regions of interest. In this work, therefore, Vickers hardness and residual stress distributions at work hardened layer such as inner surface of piping butt-weld by surface-machining before and after welding were experimentally evaluated. A simulation using a local micron-scale finite element method (FEM) model has been performed to support the understanding of experimental data by a model which was proposed in previous paper (PVP2006 and 2008 [1, 2]). Redistribution behavior of residual stress by welding after surface-machining will be discussed based on experimental and analytical results with regard to crack growth behavior.

Fast Simulation for Multi-Pass Welding Process Using Iterative Substructure Method: Investigation of Optimization and Efficient Computation

2014 ◽  
Author(s):  
Akira Maekawa ◽  
Atsushi Kawahara ◽  
Hisashi Serizawa ◽  
Hidekazu Murakawa
Keyword(s):  
Residual Stress ◽  
Power Plants ◽  
Welding Process ◽  
Computation Time ◽  
Efficient Computation ◽  
Element Analysis ◽  
Substructure Method ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Welding Processes

Residual stress caused by welding processes affects characteristics of strength and fracture of equipment and piping in power plants. Numerical thermal elastic-plastic analysis is a powerful tool to evaluate weld residual stress in actual plants. However, the conventional three-dimensional precise analysis for a welding process such as multi-pass welding, machining and thermal treatment requires enormous computation time though it can provide accurate results. In this paper, the finite element analysis code based on the iterative substructure method that was developed to carry out thermal elastic-plastic analysis efficiently, with both high computational speed and accuracy, was proposed to simulate the welding process of plant equipment and piping. Furthermore, optimization of the proposed analysis code was examined and the computational efficiency and accuracy were also evaluated.

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.

Analytical Study of the Relaxation of Welding Residual Stress by Excessive Loading for Austenitic Stainless Steel Piping Welds

2009 ◽  
Author(s):  
Jinya Katsuyama ◽  
Kunio Onizawa
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Three Dimensional ◽  
Welding Residual Stress ◽  
Low Carbon ◽  
Three Dimensional Model ◽  
Butt Weld

Welding residual stress is one of the most important factors of stress corrosion cracking (SCC) for austenitic stainless steel in pressure boundary piping in nuclear power plants. The effect of excessive loading, such as an earthquake, on the residual stress was evaluated by three-dimensional analyses based on finite element method (FEM). The FEM analyses were performed using three-dimensional model for a 250A piping butt weld of low carbon stainless steel of Type 316L. A welding simulation method used in this work is based on the moving heat source with the double ellipsoid model and was confirmed by comparing with the experimental measurements. After conducting welding residual stress simulation, several loading patterns of bending moment and uni-axial displacements have been applied to a model by varying amount of moment and displacement. The analyses indicated that higher loading to bending and axial stresses caused higher relaxation of welding residual stress near piping welds. The difference in the effect of loading direction was observed for both cases. It is concluded that the SCC growth rate might be decreased as loading level increased.

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.

Effect of the Groove Shape on Residual Stress Distribution of Narrow Gap Welds

2011 ◽  
Author(s):  
Na-Hyun Soh ◽  
Nam-Su Huh ◽  
Jun-Seok Yang
Keyword(s):  
Residual Stress ◽  
Steam Generator ◽  
Power Plants ◽  
Welding Process ◽  
Small Deformation ◽  
Life Assessment ◽  
Narrow Gap ◽  
Bead Width ◽  
Groove Shape ◽  
Weld Residual Stress

Recently, in Korea, the reactor coolant main loop piping and the steam generator have been connected with narrow gap welding (NGW) method after the replacement of steam generator of Korean nuclear power plants. The NGW method has many advantages, for instance, the reduction of welding time and the shrinkage of weld, and the small deformation of a component resulting from the small groove angle and welding bead width. In the actual welding process with NGW, some different groove shapes have been adapted. Noting that the distribution of a weld residual stress is significantly affected by welding conditions, for instance, shape of weld groove, direction of welding and width of weld groove etc., the weld residual stress due to NGW with different welding conditions should be accurately investigated for its application to life assessment considering actual conditions since these residual stress distributions can affect the susceptibility of parent and weld material to the primary water stress corrosion cracking (PWSCC) which is one of main issues in the nuclear component integrity. In this context, the present paper investigates the distribution of the weld residual stress as well as the deformation behavior of ER308L weld due to NGW using the nonlinear 2-dimensional (2-D) finite element (FE) analysis in which the detailed actual welding process of NGW was simulated. In particular, the effect of shape of weldment, i.e., the shape of welding groove (“single-side weld” and “double-side weld”) and the width of weld, on the residual stress is emphasized. Based on the FE results, the relevant groove shape is discussed in the sense that it provides lower residual stress values at the inner surface of pipe, which might reduce susceptibility to PWSCC.

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.

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