Numerical Analysis of Weld Residual Stress in a Pressurizer Surge Nozzle Full-Scale Mockup: The Effect of Hardening Constitutive Model and Interpass Temperature

2015 ◽  
Author(s):  
Minh N. Tran ◽  
Ondrej Muránsky ◽  
Michael R. Hill ◽  
Mitchell D. Olson
Keyword(s):  
Thermal Analysis ◽  
Residual Stress ◽  
Kinematic Hardening ◽  
Measurement Techniques ◽  
Mechanical Analysis ◽  
Full Scale ◽  
Contour Method ◽  
Cooperative Research ◽  
Weld Residual Stress ◽  
Interpass Temperature

In an effort to shed light on accuracy and reliability of finite element (FE) weld modeling outputs, the U.S. Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute (EPRI) have been engaged in a program of cooperative research on weld residual stress (WRS) prediction. The current work presents numerical FE simulation of the WRS in a pressurizer surge nozzle full-scale mockup (Phase 2b), as a part of the broader NRC/EPRI program. Sequentially-coupled, thermo-mechanical FE analysis was performed, whereby the numerical solution from the thermal analysis was used as an input in the mechanical analysis. The thermal analysis made use of a dedicated weld modeling tool to accurately calibrate an ellipsoidal Gaussian volumetric heat source. The subsequent mechanical analysis utilized the isotropic and nonlinear kinematic hardening constitutive models to capture cyclic response of the material upon welding. The modeling results were then validated using a number of measurement techniques (deep hole drilling, contour method, slitting, and biaxial mapping). In addition, an effect of the interpass temperature (i.e. 24.5 °C, 150 °C, and 260 °C) on the final prediction of WRS is discussed.

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.

Characterization of a Plate Specimen From Phase I of the NRC/EPRI Weld Residual Stress Program

2011 ◽  
Author(s):  
Matthew Kerr ◽  
David L. Rudland ◽  
Michael B. Prime ◽  
Hunter Swenson ◽  
Miles A. Buechler ◽  
...  
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Phase I ◽  
Nuclear Regulatory Commission ◽  
Contour Method ◽  
304L Stainless Steel ◽  
Fe Model ◽  
Stress Measurements ◽  
Weld Residual Stress ◽  
Plate Specimen

Time-of-flight neutron diffraction and contour method residual stress measurements were conducted at Los Alamos National Lab (LANL) on a lab sized plate specimen (P4) from Phase I of the joint U.S. Nuclear Regulatory Commission and Electric Power Research Institute Weld Residual Stress (NRC/EPRI WRS) program. The specimen was fabricated from a 304L stainless steel plate containing a seven pass Alloy 82 groove weld, restrained during welding and removed from the restraint for residual stress characterization. This paper presents neutron diffraction and contour method results, and compares these experimental stress measurements to a WRS Finite Element (FE) model. Finally details are provided on the procedure used to calculate the residual stress distribution in the restrained or as welded condition in order to allow comparison to other residual stress data collected as part of the EPRI lead Phase I WRS program.

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.

Modelling and Measuring Residual Stresses in Pipe Girth Welds: Lessons From the Style Framework 7 Project

2014 ◽  
Author(s):  
Mike C. Smith ◽  
Ondrej Muransky ◽  
David Smith ◽  
Son Cao Do ◽  
P. John Bouchard ◽  
...  
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Measurement Techniques ◽  
Simulation Techniques ◽  
Element Simulation ◽  
Weld Residual Stress ◽  
Wide Range ◽  
Girth Welds ◽  
Welded Pipe ◽  
Stress Simulation

A number of girth-welded pipe mock-ups have been manufactured and investigated during the STYLE project, using a wide range of measurement techniques accompanied by extensive finite element simulation campaigns. This paper gives an overview of the work carried out and presents preliminary conclusions on the performance of finite element weld residual stress simulation techniques in the different mock-up designs.

Measurement of Residual Stress in Reactor Nozzle Mock-Ups Containing Dissimilar Metal Welds

2014 ◽  
Author(s):  
Adrian T. DeWald ◽  
Michael R. Hill ◽  
Michael L. Benson ◽  
David L. Rudland
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Tensile Residual Stress ◽  
Contour Method ◽  
Two Dimensional ◽  
Weld Residual Stress ◽  
Accelerate Growth ◽  
Primary Water ◽  
Spatially Varying

Weld residual stresses can significantly impact the performance of structural components. Tensile residual stresses are of particular concern due to their ability to accelerate failure. For example, the presence of tensile residual stress can cause initiation and accelerate growth of primary water stress corrosion cracking (PWSCC). The contour method is a residual stress measurement technique capable of generating two dimensional maps of residual stress, which is particularly useful when applied to welds since they typically contain spatially varying residual stress distributions. The two-dimensional capability of the contour method enables detailed visualization of complex weld residual stress fields. This data can be used to identify locations and magnitude of tensile residual stress hot-spots. This paper provides a summary of the contour method and presents detailed results of contour method measurements made on a mock-up from the NRC/EPRI weld residual stress (WRS) program [1].

Phase 2b Weld Residual Stress Round Robin: Mockup Design and Comparisons of Measurement and Simulation Results

2015 ◽  
Author(s):  
Michael L. Benson ◽  
Minh N. Tran ◽  
Michael R. Hill
Keyword(s):  
Residual Stress ◽  
Nuclear Regulatory Commission ◽  
Round Robin ◽  
Contour Method ◽  
Hole Drilling ◽  
Problem Statement ◽  
Double Blind ◽  
Weld Residual Stress ◽  
Surge Line ◽  
Regulatory Commission

The U. S. Nuclear Regulatory Commission and the Electric Power Research Institute, cooperating under the auspices of a memorandum of understanding, conducted a double-blind round robin study for prediction of weld residual stress in a full-scale pressurizer surge line mockup. This work is the latest in a series of studies aimed at understanding and reducing uncertainty in the numerical prediction of weld residual stress. The round robin study involved both measurements and modeling. The measurements included deep hole drilling and contour method. Ten international participants submitted finite element modeling results to the study. This paper summarizes the mockup design, the modeling problem statement, and the measurement and modeling results.

Residual Stress Concentrations in a Stainless Steel Slot-Weld Measured by the Contour Method and Neutron Diffraction

2009 ◽  
Author(s):  
P. John Bouchard ◽  
Mark Turski ◽  
Mike C. Smith
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Neutron Diffraction ◽  
Structural Integrity ◽  
Measurement Techniques ◽  
Transverse Component ◽  
Contour Method ◽  
Stress Concentrations ◽  
Residual Stress Field ◽  
Concentration Effects

Arc-welding involves the deposition of molten filler metal and the localised input of intense heat. The surrounding parent material and, in the case of multi-pass welds, previously deposited weld metal, undergoes complex thermo-mechanical cycles involving elastic, plastic, creep and viscous deformations. These processes result in the development of large residual stress gradients around the welded region, which can be particularly detrimental to the structural integrity of plant components. The present study examines aggregated weld bead start and stop stress concentration effects in a three pass slot weld specimen that was designed to represent a multi-pass weld repair (without any original weld). The specimen design comprised a Type 316L stainless steel base-plate of nominal dimensions (300 × 200 × 25) mm3 with a 100 mm long by 10 mm deep central slot filled with 3 stringer manual metal arc weld beads, laid one on top of another. Residual stresses in three orthogonal directions were measured by neutron diffraction on a plane cutting through the centre of the plate, parallel to the welding direction, to show concentrations of tensile stress at both the weld start and stop positions. The transverse component of residual stress on the same plane in a second, nominally identical, specimen was mapped using the contour method. By applying two independent measurement techniques the residual stress field within the specimen type was determined with an increased level of confidence. Maximum transverse stress values of about 200 MPa at the weld start position and 300 MPa at the weld stop position were found. Peak tensile stresses in the longitudinal direction of 370 and 460 MPa were measured using neutron diffraction at the weld start and stop positions, respectively. The stresses measured by the contour method and neutron diffraction were in reasonable overall agreement with each other. However, the comparisons pointed to the possible presence of cutting artefacts in the contour results.

Weld Residual Stress Predictions in Reactor Vessel Head Penetrations: FE Simulation

2009 ◽  
Author(s):  
Anne Teughels ◽  
Rodolfo L. M. Suanno ◽  
Christian Malekian ◽  
Lucio D. B. Ferrari
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Element Model ◽  
Mechanical Analysis ◽  
Welding Residual Stress ◽  
Alloy 600 ◽  
Residual Stress Field ◽  
Pressurized Water ◽  
Weld Residual Stress ◽  
Water Reactors

The penetrations in the early Pressurized Water Reactors Vessels are characterized by Alloy 600 tubes, welded by Alloy 182/82. The Alloy 600 tubes have been shown to be susceptible to PWSCC (Primary Water Stress Corrosion Cracking) which may lead to crack forming. The cracking mechanism is driven mainly by the welding residual stress and, in a second place, by the operational stress in the weld region. It is therefore of big interest to quantify the weld residual stress field correctly. In this paper the weld residual stress field is calculated by finite elements, using a common approach well known in nuclear domain. It includes a transient thermal analysis simulating the heating during the multipass welding, followed by a transient thermo-mechanical analysis for the determination of the stresses involved with it. The welding consists of a sequence of weld beads, each of which is deposited in its entirety, at once, instead of gradually. Central as well as eccentric sidehill nozzles on the vessel head are analyzed in the paper. For the former a 2-dimensional axisymmetrical finite element model is used, whereas for the latter a 3-dimensional model is set up. Different positions on the vessel head are compared and the influence of the sidehill effect is illustrated. In the framework of a common project for Angra 1, Tractebel Engineering (Belgium) and Eletronuclear (Nuclear Utility, Brazil) had the opportunity to compare their analysis method, which they applied to the Belgian and the Brazilian nuclear reactors, respectively. The global approach in both cases is very similar but is applied to different configurations, specific for each NPP. In the article the results of both cases are compared.

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