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.

A Study of the Effect of Hardening Model in the Prediction of Welding Residual Stress

2012 ◽  
Author(s):  
Martina M. Joosten ◽  
Martin S. Gallegillo
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Kinematic Hardening ◽  
Welding Process ◽  
Cyclic Hardening ◽  
Welding Residual Stress ◽  
Isotropic Hardening ◽  
Hardening Models ◽  
Set Up

The presence of residual stresses can significantly affect the performance of manufactured products. The welding process is one of the most common causes of large tensile residual stresses, which may contribute to failure by brittle fracture or cause other forms of failure such as damage by corrosion and creep. Welding is a widely used method of fabrication and it can generate high levels of residual stress over significant proportions of the thickness of a component. In order to study the effect of material characterisation on computer based predictions of welding residual stresses, the presented work was carried out as part of the European Network on Neutron Techniques Standardisation for Structural Integrity (NeT). Within the NeT, a task group is investigating a three-pass Tungsten Inert Gas (TIG) weld benchmark. The three-pass specimen offers the possibility of examining the cyclic hardening and annealing behaviour of the weld metal and heat affected zone. A 3D model of the benchmark NeT problem was set up using ABAQUS v6.9.1 and validated against measurements. This paper presents the finite element work. Future papers from the NeT shall present experimental measurements. Different hardening models were considered in order to study their effect on the residual stresses. The different hardening models were isotropic hardening, linear and nonlinear kinematic hardening and combinations of these. Also the effect of annealing on the hardening behaviour is studied. Finally, the results of the simulations are compared to residual stress distributions as given in several standards.

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.

A Study on Development of Optimum FE Analysis Model on Welding Stress Analysis for CEDM Penetration Nozzle

2014 ◽  
Author(s):  
Tae-young Ryu ◽  
J. B. Choi ◽  
Kyoung S. Lee
Keyword(s):  
Residual Stress ◽  
Stress Analysis ◽  
Experimental Methods ◽  
Fe Analysis ◽  
Welding Residual Stress ◽  
Hole Drilling ◽  
Fe Model ◽  
Analysis Model ◽  
Welding Stress ◽  
Mesh Density

For decades, the PWSCC on the penetration nozzles like BMI and CEDM nozzles are widely occurred all around the world. The PWSCC is dependent on the tensile stress condition, specific materials and chemical environment. Therefore, to evaluate the severity of the PWSCC, prediction of the welding residual stress on the J-groove welding part in the penetration nozzles is essential. Residual stress can be measured by using experimental methods like deep-hole drilling and X-ray diffraction, etc. However, the results of experimental methods are quite doubtable and these methods are hard to apply on the actual equipment. Therefore, computational approach like the FE analysis has been considered. The FE analysis results are very sensitive to the FE model density and analysis conditions. In this paper the optimized FE model for the residual stress analysis will be developed in the case of CEDM penetration nozzle. The optimized parameters contains bead number and mesh density. The bead numbers along the longitudinal and circumferential directions are considered and the mesh density in each the bead is also considered. The model will be verified by numerical error control.

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.

The Effects of Loadings on Welding Residual Stresses and Assessment of Fracture Parameters in a Welding Residual Stress Field

2011 ◽  
Author(s):  
Liwu Wei ◽  
Weijing He ◽  
Simon Smith
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Path Dependence ◽  
Welding Residual Stress ◽  
Assessment Procedure ◽  
Fe Model ◽  
J Integral ◽  
Residual Stress Field ◽  
Growing Crack

The level of welding residual stress is an important consideration in the ECA of a structure or component such as a pipeline girth weld. Such a consideration is further complicated by their variation under load and the complexity involved in the proper assessment of fracture mechanics parameters in a welding residual stress field. In this work, 2D axi-symmetric FEA models for simulation of welding residual stresses in pipe girth welds were first developed. The modelling method was validated using experimental measurements from a 19-pass girth weld. The modeling method was used on a 3-pass pipe girth weld to predict the residual stresses and variation under various static and fatigue loadings. The predicted relaxation in welding residual stress is compared to the solutions recommended in the defect assessment procedure BS 7910. Fully circumferential internal cracks of different sizes were introduced into the FE model of the three-pass girth weld. Two methods were used to introduce a crack. In one method the crack was introduced instantaneously and the other method introduced the crack progressively. Physically, the instantaneously introduced crack represents a crack originated from manufacturing or fabrication processes, while the progressively growing crack simulates a fatigue crack induced during service. The J-integral values for the various cracks in the welding residual stress field were assessed and compared. This analysis was conducted for a welding residual stress field as a result of a welding simulation rather than for a residual stress field due to a prescribed temperature distribution as considered by the majority of previous investigations. The validation with the 19-pass welded pipe demonstrated that the welding residual stress in a pipe girth weld can be predicted reasonably well. The relaxation and redistribution of welding residual stresses in the three-pass weld were found to be significantly affected by the magnitude of applied loads and the strain hardening models. The number of cycles in fatigue loading was shown to have little effect on relaxation of residual stresses, but the range and maximum load together governed the relaxation effect. A significant reduction in residual stresses was induced after first cycle but subsequent cycles had no marked effect. The method of introducing a crack in a FE model, progressively or instantaneously, has a significant effect on J-integral, with a lower value of J obtained for a progressively growing crack. The path-dependence of the J-integral in a welding residual stress field is discussed.

Cyclic Plasticity for Nonproportional Paths: Part 2—Comparison With Predictions of Three Incremental Plasticity Models

1978 ◽  
Vol 100 (1) ◽  
pp. 104-111 ◽  
Author(s):  
H. S. Lamba ◽  
O. M. Sidebottom
Keyword(s):  
Cyclic Loading ◽  
Material Property ◽  
Yield Surface ◽  
Strain Path ◽  
Kinematic Hardening ◽  
Cyclic Plasticity ◽  
Limit Surface ◽  
Hardening Rule ◽  
Hardening Models ◽  
Hardening Rules

Experiments that demonstrate the basic quantitative and qualitative aspects of the cyclic plasticity of metals are presented in Part 1. Three incremental plasticity kinematic hardening models of prominence are based on the Prager, Ziegler, and Mroz hardening rules, of which the former two have been more frequently used than the latter. For a specimen previously fully stabilized by out of phase cyclic loading the results of a subsequent cyclic nonproportional strain path experiment are compared to the predictions of the above models. A formulation employing a Tresca yield surface translating inside a Tresca limit surface according to the Mroz hardening rule gives excellent predictions and also demonstrates the erasure of memory material property.

3-D Elastic-Plastic Constitutive Relationship of Mixed Hardening

2012 ◽  
Vol 249-250 ◽  
pp. 927-930
Author(s):  
Ze Yu Wu ◽  
Xin Li Bai ◽  
Bing Ma
Keyword(s):  
Finite Element ◽  
Constitutive Relation ◽  
Kinematic Hardening ◽  
Constitutive Relationship ◽  
Isotropic Hardening ◽  
Element Analysis ◽  
Hardening Model ◽  
Elastic Plastic ◽  
Mixed Hardening ◽  
Advantages And Disadvantages

In finite element calculation of plastic mechanics, isotropic hardening model, kinematic hardening model and mixed hardening model have their advantages and disadvantages as well as applicability area. In this paper, by use of the tensor analysis method and mixed hardening theory in plastic mechanics, the constitutive relation of 3-D mixed hardening problem is derived in detail based on the plane mixed hardening. Numerical results show that, the proposed 3-D mixed hardening constitutive relation agrees well with the test results in existing references, and can be used in the 3-D elastic-plastic finite element analysis.

Influence of the Hardening Model on the Predicted Welding Distortion of DP600 Lap Joints

2010 ◽  
Vol 638-642 ◽  
pp. 3710-3715
Author(s):  
T. Schenk ◽  
I.M. Richardson ◽  
G. Eßer ◽  
M. Kraska
Keyword(s):  
Kinematic Hardening ◽  
Tensile Tests ◽  
Lap Joints ◽  
Welding Distortion ◽  
Isotropic Hardening ◽  
Hardening Model ◽  
Mixed Hardening ◽  
Overlap Joint ◽  
Definition Of ◽  
Robust Process

The accurate prediction of welding distortion is an important requirement for the industry in order to allow the definition of robust process parameters without the need to perform expensive experiments. Many models have been developed in the past decades in order to improve prediction. Assumptions are made to make the models tractable; however, the consequences are rarely discussed. One example for such an assumption is the strain hardening model, which is often a choice between either kinematic or isotropic hardening. This paper presents the results of tensile tests for DP600 performed from room temperature up to one thousand degrees and for different strain-rates. In order to employ a mixed isotropic-kinematic hardening model, the fractions of each hardening contribution have been determined by means of bend testing. The welding distortion of a DP600 overlap joint has been simulated and it is shown that such a mixed-hardening model results in more accurate and reliable results.

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