On Residual Stress and Relief for an Ultra-Thick Cylinder Weld Joint Based on Mixed Hardening Model: Numerical and Experimental Studies

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Luyang Geng ◽  
Shan-Tung Tu ◽  
Jianming Gong ◽  
Wenchun Jiang ◽  
Wei Zhang
Keyword(s):  
Residual Stress ◽  
Weld Joint ◽  
Kinematic Hardening ◽  
Experimental Studies ◽  
Bending Moment ◽  
Band Width ◽  
Thick Wall ◽  
Mixed Hardening ◽  
Inner Surface ◽  
Simulation Results

Residual stress distributions as welded and after local postwelding heat treatment (PWHT) of butted weld joint of a huge cylinder with ultra-thick wall were investigated by finite element (FE) simulations and measurement. Sequential coupling thermal-mechanical analyses were conducted with a generalized plane strain two-dimensional (2D) model to simulate the welding procedure bead by bead, combining with three-dimensional (3D) double-ellipsoid moving heat source and mixed isotropic–kinematic hardening plastic model. The simulation was validated by X-ray diffraction (XRD) measurements. Simulation results showed that local PWHT with heated band width of 0.5Rt can significantly reduce the residual stress on the outer surface of weld joint, but bring about harmful high tensile stress on inner surface due to bending moment induced by local radial thermal distortion. For the purpose to find out the appropriate heated band width of local PWHT, relations between stress relief and size of heated band were studied. Results show that the stresses on the inner surface reach a maximum value when the heated band width is less than 1Rt. Based on the simulation results and from the view point of lowering the stress level on the inner surface, the optimum width of 3Rt for heated band was proposed.

Weld Residual Stress in Large Diameter Nuclear Nozzles

2011 ◽  
Author(s):  
Tao Zhang ◽  
F. W. Brust ◽  
Gery Wilkowski
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Nuclear Power ◽  
Kinematic Hardening ◽  
Large Diameter ◽  
Thick Wall ◽  
Isotropic Hardening ◽  
Residual Stress Field ◽  
Mixed Hardening ◽  
Weld Residual Stress

Weld residual stresses in nuclear power plant can lead to cracking concerns caused by stress corrosion. These are large diameter thick wall pipe and nozzles. Many factors can lead to the development of the weld residual stresses and the distributions of the stress through the wall thickness can vary markedly. Hence, understanding the residual stress distribution is important to evaluate the reliability of pipe and nozzle joints with welds. This paper represents an examination of the weld residual stress distributions which occur in various different size nozzles. The detailed weld residual stress predictions for these nozzles are summarized. Many such weld residual stress solutions have been developed by the authors in the last five years. These distributions will be categorized and organized in this paper and general trends for the causes of the distributions will be established. The residual stress field can therefore feed into a crack growth analysis. The solutions are made using several different constitutive models such as kinematic hardening, isotropic hardening, and mixed hardening model. Necessary fabrication procedures such as repair, overlay and post weld heat treatment are also considered. Some general discussions and comments will conclude the paper.

Weld Residual Stress in Various Large Diameter Nuclear Nozzles

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Tao Zhang ◽  
Frederick W. Brust ◽  
Gery Wilkowski
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Power Plants ◽  
Kinematic Hardening ◽  
Large Diameter ◽  
Postweld Heat Treatment ◽  
Thick Wall ◽  
Isotropic Hardening ◽  
Mixed Hardening ◽  
Weld Residual Stress

Weld residual stresses in nuclear power plants can lead to cracking concerns caused by stress corrosion. Many factors can lead to the development of the weld residual stresses, and the distributions of the stress through the wall thickness can vary markedly depending on the weld processing parameters, nozzle and pipe geometries, among other factors. Hence, understanding the residual stress distribution is important in order to evaluate the reliability of pipe and nozzle welded joints. This paper represents an examination of the weld residual stress distributions which occur in different nozzles. The geometries considered here are large diameter thick wall pipe and nozzles. The detailed weld residual stress predictions for these nozzles are summarized. These results are categorized and organized in this paper and general trends for the causes of the distributions are established. The solutions are obtained using several different constitutive models including kinematic hardening, isotropic hardening, and mixed hardening model. Necessary fabrication procedures such as weld repair, overlay, and postweld heat treatment are also considered. The residual stress field can therefore be used to perform a crack growth and instability analysis. Some general discussions and comments are given in the paper.

Effects of material hardening model and lumped-pass method on welding residual stress simulation of J-groove weld in nuclear RPV

2016 ◽  
Vol 33 (5) ◽  
pp. 1435-1450 ◽  
Author(s):  
Chuan Liu ◽  
Ying Luo ◽  
Min Yang ◽  
Qiang Fu
Keyword(s):  
Residual Stress ◽  
Kinematic Hardening ◽  
Computation Time ◽  
Welding Residual Stress ◽  
Cyclic Plasticity ◽  
Fe Model ◽  
Content Type ◽  
Hardening Model ◽  
Mixed Hardening ◽  
Hardening Models

Purpose – The purpose of this paper is to clarify the effect of material hardening model and lump-pass method on the thermal-elastic-plastic (TEP) finite element (FE) simulation of residual stress induced by multi-pass welding of materials with cyclic plasticity. Design/methodology/approach – Nickel-base alloy and stainless steel, which are used in J-type weld for manufacturing the nuclear reactor pressure head, can easily harden during multi-pass welding. The J-weld welding experiment is carried out and the temperature cycle and residual stress are measured to validate the TEP simulation. Thermal-mechanical sequence coupling method is employed to get the welding residual stress. The lumped-pass model and pass-by-pass FE model are built and two materials hardening models, kinematic hardening model and mixed hardening model, are adopted during the simulations. The effects of material hardening models and lumped-pass method on the residual stress in J-weld are distinguished. Findings – Based on the kinematic hardening model, the stresses simulated with the lumped-pass FE model are almost consistent with those obtained by the pass-by-pass FE model; while with the mixed hardening material model, the lumped-pass method has great effect on the simulated stress. Practical implications – A computation with mixed isotropic-kinematic material seems not to be the appropriate solution when using the lumped-pass method to save the computation time. Originality/value – In the simulation of multi-pass welding residual stress involved in materials with cyclic plasticity, the material hardening model should be carefully considered. The kinematic hardening model with lump-pass FE model can be used to get better simulation results with less computation time. The results give a direction for welding residual stress simulation for the large structure such as the reactor pressure vessel.

Welding Simulation: Relationship Between Welding Geometry and Determination of Hardening Model

2012 ◽  
Author(s):  
Jonathan Mullins ◽  
Jens Gunnars
Keyword(s):  
Residual Stress ◽  
Test Data ◽  
Mechanical Test ◽  
Kinematic Hardening ◽  
Isotropic Hardening ◽  
Hardening Model ◽  
Welding Simulation ◽  
Mixed Hardening ◽  
Heating And Cooling ◽  
Single Bead

It is generally acknowledged that the material hardening model exerts a considerable effect on predicted weld residual stress fields. For this reason the choice of hardening model has attracted interest among analysts, particularly during recent validation studies. Nevertheless there is still lack of evidence for a hardening model which is generally applicable for all welding geometries. In this work we examine the predictions of nonlinear kinematic, isotropic and mixed hardening models for two different geometries: a single bead on plate weld, and a multi-bead girth weld. Hardening parameters are based on the same openly available mechanical test data. Deformation histories for the two welding geometries are presented. Predicted residual stress profiles are compared with experimental measurements. It is noted that nonlinear kinematic hardening results in good predictions for the single bead welding simulation where hardening in the weld and HAZ is dominated by a single heating and cooling cycle. Isotropic hardening results in good predictions for the 42 bead girth weld, where hardening in the weld and HAZ is heavily influenced by several heating and cooling cycles from the addition of several weld beads and where some relaxation of residual stress is possible. Mixed hardening can result in good predictions for both welding geometries. Additional strategies for development of material models based on isotropic and kinematic hardening and relevant test data are discussed with particular attention paid to intermediate weld geometries.

The Role of Plasticity Theory on the Predicted Residual Stress Field of Weld Structures

2013 ◽  
Vol 772 ◽  
pp. 65-71 ◽  
Author(s):  
Ondrej Muránsky ◽  
Cory J. Hamelin ◽  
Mike C. Smith ◽  
Phillip J. Bendeich ◽  
Lyndon Edwards
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Kinematic Hardening ◽  
Plasticity Theory ◽  
Isotropic Hardening ◽  
Residual Stress Field ◽  
Hardening Model ◽  
Mixed Hardening ◽  
Weld Residual Stress

Constitutive plasticity theory is commonly applied to the numerical analysis of welds in one of three ways: using an isotropic hardening model, a kinematic hardening model, or a mixed isotropic-kinematic hardening model. The choice of model is not entirely dependent on its numerical accuracy, however, as a lack of empirical data will often necessitate the use of a specific approach. The present paper seeks to identify the accuracy of each formalism through direct comparison of the predicted and actual post-weld residual stress field developed in a three-pass 316LN stainless steel slot weldment. From these comparisons, it is clear that while the isotropic hardening model tends to noticeably over-predict and the kinematic hardening model slightly under-predict the residual post-weld stress field, the results using a mixed hardening model are quantitatively accurate. Even though the kinematic hardening model generally provides more accurate results when compared to an isotropic hardening formalism, the latter might be a more appealing choice to engineers requiring a conservative design regarding weld residual stress.

Residual Stress of Thin-Wall Pipe Subjected to Axisymmetric Plastic Expansion

2002 ◽  
Author(s):  
Norimasa Chiba ◽  
Yuji Ishida ◽  
Nagahisa Ogasawara ◽  
Hiroshi Ito ◽  
Kunio Enomoto ◽  
...  
Keyword(s):  
Residual Stress ◽  
Plastic Region ◽  
Longitudinal Direction ◽  
Residual Stress Distribution ◽  
Thick Wall ◽  
Thin Wall ◽  
Pipe Expansion ◽  
Inner Surface ◽  
Peak Location ◽  
Axisymmetric Plastic

A straight thin-wall pipe was plastically expanded at one end in the radial direction by inserting a rigid disk. The residual stress measured after withdrawal of the disk at the inner surface in the hoop and in the longitudinal direction shows a strong tensile peak beyond the region where the pipe was directly expanded by the insertion of the disk. The reason why the residual stress reaches its peak at the location far inward of the pipe, not in the region where the pipe was directly expanded, is discussed. From the FE analysis, it is concluded that the residual stress reaches its tensile peak on the inner surface at the plastic region front that was developed during the pipe expansion, and a simple formula for the tensile peak location is proposed. The similarities and differences between the residual stress distribution of the thin-wall pipe and the thick-wall pipe are discussed.

Springback Prediction Using Finite Element Simulation Incorporated With Hardening Data Acquired From Cyclic Loading Tool

2019 ◽  
Vol 6 (1) ◽  
pp. 19-39
Author(s):  
Jasri Mohamad ◽  
Mohd Zaidi Sidek
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Bauschinger Effect ◽  
Fe Simulation ◽  
Kinematic Hardening ◽  
Isotropic Hardening ◽  
Mixed Hardening ◽  
Element Simulation ◽  
Simulation Results ◽  
Springback Prediction

The aims of this article are to present the accuracy of springback prediction in U-bending sheet metal forming processes using finite element (FE) simulation incorporated with kinematics or mixed hardening parameters that are derived from cyclic data provided by the developed cyclic loading tool. The FE simulation results in the form of springback angles are compared with the experimental results for validation. It was found that the mixed hardening model provides better simulation results in predicting springback. This is due to the capability of the isotropic hardening part of this model to describe cyclic transient and the kinematic hardening part to improve description of the Bauschinger effect. Kinematic hardening however, on its own is capable of providing relatively good springback simulation illustrated by errors of less than 8 percent. Overall, the data provided by cyclic loading from the newly developed bending-unbending tool is considered valuable for simulating springback prediction.

Influence of Laser Shock Processing on the Weld Line and Finite Element Simulation

2011 ◽  
Vol 464 ◽  
pp. 627-631
Author(s):  
Jie Zhang ◽  
Ai Hua Sun ◽  
Le Zhu ◽  
Xiang Gu
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Welding Residual Stress ◽  
Laser Shock ◽  
Analysis Software ◽  
Laser Shock Processing ◽  
Element Analysis ◽  
Welding Line ◽  
Simulation Results ◽  
Shock Processing

Welding residual stress is one of the main factors that affect the strength and life of components. In order to explore the effect on residual stress of welding line by laser shock processing, finite element analysis software ANSYS is used to simulate the welding process, to calculate the distribution of welding residual stress field. On this basis, then AYSYS/LS-DYNA is used to simulate the laser shock processing on welding line. Simulation results show that residual stress distributions of weld region, heat-affected region and matrix by laser shock processing are clearly improved, and the tensile stress of weld region effectively reduce or eliminate. The simulation results and experimental results are generally consistent, it offer reasons for parameter optimization of welding and laser shock processing by finite element analysis software.

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