Numerical Analyses of Residual Stress Fields in Welded Components

2009 ◽  
Author(s):  
Dieter Siegele ◽  
Marcus Brand ◽  
Igor Varfolomeev ◽  
Jo¨rg Hohe
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Base Metal ◽  
Stress Fields ◽  
X Ray Diffraction ◽  
Residual Stress Field ◽  
Temperature Dependent ◽  
Compressive Stresses ◽  
Core Shroud

Residual stresses in welded components can influence the lifetime significantly. Besides experimental methods of residual stress measurements numerical methods of welding simulation are an important tool to determine the whole residual stress field in a component as a basis for lifetime prediction. As examples, the residual stresses in a core shroud of a boiling water reactor (BWR) and in a cladded plate have been investigated. In case of the core shroud postulated cracks in the residual stress field of the weld have been assessed with respect to possible crack corrosion cracking. For the cladded plate, the numerical simulation of the cladding and heat treatment process was accompanied by measurements of temperature, distortions and residual stresses. In the analysis, the temperature dependent material properties as well as the transformation behavior of the ferritic base metal were taken into account. The calculated residual stresses show tensile stresses in the cladding followed by compressive stresses in the base metal that are in agreement with measurements with X-ray diffraction technique.

Determination of the Residual Stress Field around Scratches Using Synchrotron X-Rays and Nanoindentation

2010 ◽  
Vol 652 ◽  
pp. 25-30
Author(s):  
M.K. Khan ◽  
Michael E. Fitzpatrick ◽  
L.E. Edwards ◽  
S.V. Hainsworth
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Small Scale ◽  
X Rays ◽  
X Ray Diffraction ◽  
Residual Stress Field ◽  
Fine Grained ◽  
Load Displacement

The residual strain field around the scratches of 125µm depth and 5µm root radius have been measured from the Synchrotron X-ray diffraction. Scratches were produced using different tools in fine-grained aluminium alloy AA 5091. Residual stresses up to +1700 micro-strains were measured at the scratch tip for one tool but remained up to only +1000 micro-strains for the other tool scratch. The load-displacement curves obtained from nanoindentation were used to determine the residual stresses around the scratches. It was found that the load-displacement curves are sensitive to any local residual stress field present and behave according to the type of residual stresses. This combination of nanoindentation and synchrotron X-rays has been proved highly effective for the study of small-scale residual stresses around the features such as scratches.

scholarly journals Modèle numérique pour l’étude des structures fissurées soumises à des contraintes résiduelles

2007 ◽  
pp. 627-642
Author(s):  
Zohra Gaiech ◽  
Hocine Kebir ◽  
Laurent Chambon ◽  
Jean-Marc Roelandt
Keyword(s):  
Residual Stress ◽  
Boundary Element Method ◽  
Stress Field ◽  
Residual Stresses ◽  
Specific Treatment ◽  
Cyclic Loads ◽  
Residual Stress Field ◽  
Principle Of Superposition ◽  
Compressive Stresses ◽  
Improve Fatigue

During their operational use the aeronautic structures can be submitted to relatively moderate cyclic loads and more rarely to stern loads. These last can generate residual stress field, which will influence the in-service behaviour. Otherwise, residual stress field can be created in a voluntary way by a specific treatment (compressive stresses). They permit to improve fatigue tolerance behaviour. This illustrates the importance of the study of the structure behavior under residual stresses, and the need to consider them in numerical simulations. The objective of this work is to develop a numerical method, based on the boundary element method and the principle of superposition, to assess the influence of residual stresses on fracture mechanics parameters.

Numerical Simulation of Residual Stresses Due to Cladding Process

2007 ◽  
Author(s):  
Dieter Siegele ◽  
Marcus Brand
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Residual Stresses ◽  
Base Metal ◽  
Base Material ◽  
Pressure Vessels ◽  
Measured Temperature ◽  
Residual Stress Field

The inner surface of reactor pressure vessels is protected against corrosion by an austenitic cladding. Generally, the cladding is welded on the ferritic base metal with two layers to avoid sub-clad cracks and to improve the microstructure of the cladding material. On the other hand, due to the cladding process and the difference of the thermal expansion coefficient of the austenitic cladding and the ferritic base material residual stresses act in the component. This residual stress field is important for assessing crack postulates in the cladding or subclad flaws in the base metal. For the determination of the residual stress field, plates of RPV steel were cladded and heat treated representative to the RPV relevant conditions. During the cladding process the temperature and distortion were measured as basis for the validation of the finite element simulations. The numerical simulation was performed with the finite element code SYSWELD. The heat source of the model was calibrated on the measured temperature profile. In the analysis, the temperature dependent material properties as well as the transformation behavior of the ferritic base metal were taken into account. The calculated residual stresses show tensile stresses in the cladding followed by compressive stresses in the base metal that are in agreement with measurements with X-ray diffraction technique.

Numerical Simulation of Residual Stress Field in Laser Transformation Hardening for GCr15 Steel Components and Experimental Study

2012 ◽  
Vol 538-541 ◽  
pp. 1897-1903 ◽  
Author(s):  
Sheng Lei ◽  
Yan Yan ◽  
Heng Li ◽  
Liu Niu ◽  
Zhong Xiang Gui ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Wide Band ◽  
Heating Process ◽  
X Ray Diffraction ◽  
Residual Stress Field ◽  
Gcr15 Steel ◽  
Compressive Stresses ◽  
Hardening Process ◽  
Laser Transformation Hardening

The laser quenching of GCr15 steel by wide band scanning technology was researched. Hardness and depths of laser transformation hardening zones of samples were also measured experimentally. Temperature field and residual stress field in the laser hardening process were numerically simulated by ANSYS software. The calculated results are in good agreement with the experimental results. The distribution of residual stress is closely related to the temperature distribution made by laser heating process. Then the distribution of residual stresses of the laser surface hardened layers was analyzed by using the X-ray diffraction (XRD). Compressive stresses were detected on the surface of the harden layer after the laser transformation hardening process, and the residual stress value of the surface of samples increases with the increasing of laser power. But the residual stress value of surface melting zones of samples is small.

Measurement and Prediction of the Residual Stress Field Generated by Side-Punching

2006 ◽  
Vol 128 (3) ◽  
pp. 451-459 ◽  
Author(s):  
A. H. Mahmoudi ◽  
D. Stefanescu ◽  
S. Hossain ◽  
C. E. Truman ◽  
D. J. Smith ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Measurement Techniques ◽  
Hole Drilling ◽  
X Ray Diffraction ◽  
Residual Stress Field ◽  
Surface Residual Stress ◽  
Alloy Plate ◽  
Near Surface

Side-punching is proposed as a method of introducing a well-defined residual stress field into a laboratory-sized test specimen. Such a specimen may subsequently be used to assess the influence of residual stresses on the fracture behavior of materials. Side-punching consists of simultaneously indenting opposite faces of a plate of material with rigid tools, using sufficient force to cause localized yielding over a finite-sized volume of material adjacent to the punching tools. This paper presents experimental measurements, obtained using three independent measurement techniques, of the residual stress field generated in an aluminium alloy plate after side-punching. Incremental center hole drilling is used to determine the near-surface residual stress field, while synchrotron x-ray diffraction and deep hole drilling are used to measure the through-thickness residual stress field along a path linking the two punch center points. Finite element (FE) predictions are also presented and compared to the measurements. There is very good agreement between all three sets of measurements and the FE results, which all show that the through-thickness residual stresses are compressive and attain a maximum value at the center of the plate. The results confirm the potential use of side-punching in residual stress-crack interaction studies.

scholarly journals Residual stresses in thermite welded rails: significance of additional forging

2020 ◽  
Vol 64 (7) ◽  
pp. 1195-1212
Author(s):  
B. Lennart Josefson ◽  
R. Bisschop ◽  
M. Messaadi ◽  
J. Hantusch
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Weld Metal ◽  
Welding Process ◽  
Surface Zone ◽  
Fe Model ◽  
Uneven Surface ◽  
Residual Stress Field ◽  
High Dynamic

Abstract The aluminothermic welding (ATW) process is the most commonly used welding process for welding rails (track) in the field. The large amount of weld metal added in the ATW process may result in a wide uneven surface zone on the rail head, which may, in rare cases, lead to irregularities in wear and plastic deformation due to high dynamic wheel-rail forces as wheels pass. The present paper studies the introduction of additional forging to the ATW process, intended to reduce the width of the zone affected by the heat input, while not creating a more detrimental residual stress field. Simulations using a novel thermo-mechanical FE model of the ATW process show that addition of a forging pressure leads to a somewhat smaller width of the zone affected by heat. This is also found in a metallurgical examination, showing that this zone (weld metal and heat-affected zone) is fully pearlitic. Only marginal differences are found in the residual stress field when additional forging is applied. In both cases, large tensile residual stresses are found in the rail web at the weld. Additional forging may increase the risk of hot cracking due to an increase in plastic strains within the welded area.

Temperature and Residual Stress Fields in an Austenitic Circumferential Pipe Weld

2002 ◽  
Author(s):  
Ruthard Bonn ◽  
Klaus Metzner ◽  
H. Kockelmann ◽  
E. Roos ◽  
L. Stumpfrock
Keyword(s):  
Residual Stress ◽  
Numerical Calculation ◽  
Stress Field ◽  
Quantitative Determination ◽  
Welding Residual Stress ◽  
Stress Fields ◽  
Residual Stress Field ◽  
Circumferential Welds ◽  
The Impact

The main target of a research programme “experimental and numerical analyses on the residual stress field in the area of circumferential welds in austenitic pipe welds”, sponsored by Technische Vereinigung der Großkraftwerksbetreiber e. V. (VGB) and carried out at MPA Stuttgart, was the validation of the numerical calculation for the quantitative determination of residual stress fields in austenitic circumferential pipe welds. In addition, the influence of operational stresses as well as the impact of the pressure test on the residual stress state had to be examined. By using the TIG orbital welding technique, circumferential welds (Material X 10 CrNiNb 18 9 (1.4550, corresponding to TP 347) were produced (geometric dimensions 255.4 mm I.D. × 8.8 mm wall) with welding boundary conditions and weld parameters (number of weld layers and weld built-up, seam volume, heat input) which are representative for pipings in power plants. Deformation and temperature measurements accompanying the welding, as well as the experimentally determined (X-ray diffraction) welding residual stress distribution, served as the basis for the verification of numeric temperature and residual stress field calculations. The material model on which the calculations were founded was developed by experimental weld simulations in the thermo-mechanical test rig GLEEBLE 2000 for the determination of the material behaviour at different temperatures and elasto-plastic deformation. The numeric calculations were carried out with the Finite Element program ABAQUS. The comparison of the calculation results with the experimental findings confirms the proven validation of the developed numerical calculation models for the quantitative determination of residual stresses in austenitic circumferential pipings. The investigation gives a well-founded insight into the complex thermo-mechanical processes during welding, not known to this extent from literature previously.

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.

Thermal Simulation of an Arbitrary Residual Stress Field in a Fully or Partially Autofrettaged Thick-Walled Spherical Pressure Vessel

2008 ◽  
Author(s):  
M. Perl
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Pressure Vessel ◽  
Stress Fields ◽  
Equivalent Temperature ◽  
Residual Stress Field ◽  
Element Analysis ◽  
Spherical Pressure ◽  
The Ideal

The equivalent thermal load was previously shown to be the only feasible method by which the residual stresses due to autofrettage and its redistribution, as a result of cracking, can be implemented in a finite element analysis, of a fully or partially autofrettaged thick-walled cylindrical pressure vessel. The present analysis involves developing a similar methodology for treating an autofrettaged thick-walled spherical pressure vessel. A general procedure for evaluating the equivalent temperature loading for simulating an arbitrary, analytical or numerical, spherosymmetric autofrettage residual stress field in a spherical pressure vessel is developed. Once presented, the algorithm is applied to two distinct cases. In the first case, an analytical expression for the equivalent thermal loading is obtained for the ideal autofrettage stress field in a spherical shell. In the second case, the algorithm is applied to the discrete numerical values of a realistic autofrettage residual stress field incorporating the Bauschinger effect. As a result, a discrete equivalent temperature field is obtained. Furthermore, a finite element analysis is performed for each of the above cases, applying the respective temperature field to the spherical vessel. The induced stress fields are evaluated for each case and then compared to the original stress. The finite element results prove that the proposed procedure yields equivalent temperature fields that in turn simulate very accurately the residual stress fields for both the ideal and the realistic autofrettage cases.

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