Influences of lumped passes on welding residual stress of a thick-walled nuclear rotor steel pipe by multipass narrow gap welding

2014 ◽  
Vol 273 ◽  
pp. 47-57 ◽  
Author(s):  
Long Tan ◽  
Jianxun Zhang ◽  
Dong Zhuang ◽  
Chuan Liu
Keyword(s):  
Residual Stress ◽  
Welding Residual Stress ◽  
Steel Pipe ◽  
Rotor Steel ◽  
Narrow Gap ◽  
Narrow Gap Welding

Numerical Simulation of Residual Stress in Multi-Pass Butt-Welded Stainless Steel Pipe

2009 ◽  
Author(s):  
S. Kasa ◽  
M. Mouri ◽  
M. Tsunori ◽  
D. Takakura
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Three Dimensional ◽  
Structural Response ◽  
Welding Residual Stress ◽  
Steel Pipe ◽  
Inelastic Behavior ◽  
Axisymmetric Model ◽  
Stiffness Method ◽  
Stainless Steel Pipe

It is necessary to obtain an accurate welding residual stress distribution for the evaluation of stress corrosion cracking (SCC) behavior. However, a welding residual stress simulation for pipes is often performed by a two dimensional axisymmetric model because this type of simulation requires significant time to analyze the complicated inelastic behavior. This approximation deteriorates the modeling accuracy since the welding heat input and the structural response are approximated by axisymmetric responses although they are originally three dimensional. The authors propose “a virtual additional stiffness method” in order to improve the accuracy of the axisymmetric model. With this method, the difference between the axisymmetric model and a three dimensional behavior was greatly reduced. The virtual additional stiffness method was used to reproduce three dimensional constraints that were not taken into account in the axisymmetric model. In the case of the axisymmetric model, an unrealistic large thermal expansion was observed because of simultaneous heating along a hoop direction of the whole pipe. In order to compensate this unrealistic deformation, a virtual additional stiffness was added in axial and radial directions on the axisymmetric model. This stiffness was added by using spring elements whose positions and spring constants were determined by comparing the two and three dimensional models. Results obtained by this new method in the multi-pass butt-welded stainless steel pipe were in very good agreement with measurements of the mock-up specimens.

Characterisation of the Residual Stress Field and Mechanical Properties of a Narrow-Gap Girth-Welded Stainless Steel Pipe and Subsequent Application to a Numerical Model

2011 ◽  
Author(s):  
Robert J. A. McCluskey ◽  
Andrew H. Sherry ◽  
Martin R. Goldthorpe
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Stainless Steel ◽  
Stress Field ◽  
Steel Pipe ◽  
Primary Circuit ◽  
Narrow Gap ◽  
Residual Stress Field ◽  
Butt Weld ◽  
Stainless Steel Pipe

Girth-butt welds are used to join sections of stainless steel pipe in the primary circuit of Pressurised Water Reactors. The welding process creates residual stress fields across the weldment, which can contribute to the crack driving force when a defect is present. Assessment procedures account for such defects, enabling safety justifications to be made for continued operation of nuclear power plant. Such procedures require the size and nature of the residual stress field to be determined in order to make reliable structural integrity assessments. This paper describes the investigation of the residual stress field and fracture behaviour of a recently developed narrow-gap 304-stainless steel girth-butt weld in a primary circuit pipe. Two residual stress measurement techniques, Neutron Diffraction (ND) and incremental Deep Hole Drilling (iDHD), were used to measure the original residual stress field in the pipe weld. A second pipe weld specimen was used to fabricate tensile and fracture toughness specimens from which the mechanical properties of the weld material were determined. The residual stress and mechanical test data were used to develop numerical models of the pipe weld containing a postulated circumferential defect under an applied axial load. The numerical simulation results were applied within a failure assessment diagram, comparing different interaction parameters on the prediction of component failure load.

Estimates of Mechanical Properties and Residual Stress of Narrow Gap Weld for Leak-Before-Break Application to Nuclear Piping

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Jun-Seok Yang ◽  
Chi-Yong Park ◽  
Nam-Su Huh
Keyword(s):  
Residual Stress ◽  
Power Plant ◽  
Nuclear Power Plant ◽  
Steam Generator ◽  
Nuclear Power ◽  
Welding Residual Stress ◽  
Fracture Toughness Test ◽  
Narrow Gap ◽  
Main Loop ◽  
Leak Before Break

The present paper addresses the mechanical characteristics of the stainless steel narrow gap weld (NGW) for the leak-before-break (LBB) application to the main loop piping of a nuclear power plant. Recently, in Korea, the connection with the reactor coolant main loop piping and the steam generator has been welded with ER308L NGW after the replacement of a steam generator of a Korean nuclear power plant. The NGW technique has many merits, for instance, the reduction of construction time and the reduction of shrinkage and deformation after welding due to its small groove angle and welding bead width compared with the conventional welds. In this paper, the tensile and fracture toughness test results of the three ER308L test coupons from NGW were presented and compared with those from conventional welds at the operating condition of the nuclear power plant. In addition, the distribution of the welding residual stress as well as the deformation behavior of the ER308L weld due to NGW was predicted through the nonlinear two-dimensional finite element analysis in which the detailed actual welding process of NGW was simulated. The results presented in this paper can be used to evaluate LBB application to nuclear piping with NGW and to provide the important information to perform the flaw evaluation as well as improve the weld procedure of NGW.

ANALYSIS OF RESIDUAL STRESS FOR NARROW GAP WELDING USING FINITE ELEMENT METHOD

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2797-2802 ◽  
Author(s):  
CHOON YEOL LEE ◽  
JAE KEUN HWANG ◽  
JOON WOO BAE
Keyword(s):  
Finite Element Method ◽  
Residual Stress ◽  
Finite Element ◽  
Nuclear Power ◽  
Power Plants ◽  
Large Diameter ◽  
Narrow Gap ◽  
Narrow Gap Welding ◽  
Welding Processes ◽  
Element Method

Reactor coolant loop (RCL) pipes circulating the heat generated in a nuclear power plant consist of so large diameter pipes that the installation of these pipes is one of the major construction processes. Conventionally, a shield metal arc welding (SMAW) process has been mainly used in RCL piping installations, which sometimes caused severe deformations, dislocation of main equipments and various other complications due to excessive heat input in welding processes. Hence, automation of the work of welding is required and narrow-gap welding (NGW) process is being reviewed for new nuclear power plants as an alternative method of welding. In this study, transient heat transfer and thermo-elastic-plastic analyses have been performed for the residual stress distribution on the narrow gap weldment of RCL by finite element method under various conditions including surface heat flux and temperature dependent thermo-physical properties.

Effect of Groove Designs on Residual Stress and Transverse Shrinkage in GMAW and PGMAW of A333 Seamless Steel Pipes

2020 ◽  
Vol 19 (04) ◽  
pp. 799-813
Author(s):  
Rohit Mishra ◽  
Avani Kumar Upadhyay ◽  
Amneesh Singla ◽  
Yashvir Singh
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Optimum Number ◽  
Narrow Gap ◽  
Narrow Gap Welding ◽  
Weld Deposit ◽  
Steel Pipes ◽  
Grade 3 ◽  
Number Of Passes ◽  
Transverse Shrinkage

The effectiveness of weld joints primarily depends on the fusion of base metal, minimum heat-affected zone (HAZ) and lesser residual stresses. The severity of thermomechanical effects e.g. weld shrinkages and residual stresses is significantly minimized by narrow gap welding technique over the traditional welding. This work describes the welding of A333 Grade 3 steel pipes by the application of GMAW and PGMAW techniques. The analysis is made to capture the effects of groove designs on residual stress and transverse shrinkage. The process parameters used for the analysis are voltage, current and welding speed. In this work, narrow groove design using PGMAW process is capable of reducing the number of passes and area of weld deposit by 35–40% by volume. In PGMAW, decrement in residual stresses is observed with a narrow groove compared to conventional V groove technique. The results are validated by metallurgical and mechanical investigation of welded joints. This work will help other researchers to understand the effect of narrow gap welding using an optimum number of passes for thick pipes.

Numerical Simulation of Weld Metal by Ultra-Narrow Gap Arc Welding

2011 ◽  
Vol 704-705 ◽  
pp. 728-732
Author(s):  
Li Zhao ◽  
Ke Jie Dai ◽  
Fu Ju Zhang
Keyword(s):  
Numerical Simulation ◽  
Finite Element Method ◽  
Residual Stress ◽  
Finite Element ◽  
Thick Plate ◽  
Welding Residual Stress ◽  
Narrow Gap ◽  
Welding Temperature ◽  
Welding Joint ◽  
Element Method

The ultra narrow gap welding process is suitable to the thick plate, ultra-thick plate welding with the characteristic of highly effective, high quality, low cost, low energy consumption and so on, and is easy to realize the mechanization and the automation. In this paper, the numerical simulation and technical experiment are used to study the form, grow and distribution regulation of the welding temperature field, stress field in welding joint with UNG MAW. Using the calculation to the thickness of 32mm, an example to simulate the magnitude and distribution of the residual stress in welding joint is given. Research shows that it is an effective analysis method to heat process and mechanic behavior in the welding by using finite element method numerical simulation and few experiments. Keywords: UNG MAW, Welding residual stress, Finite element method, Numerical simulation

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