Through-Thickness Welding Residual Stress Profile in Dissimilar Metal Nozzle Butt Weld

2010 ◽  
Author(s):  
Tae-Kwang Song ◽  
Ji-Soo Kim ◽  
Chang-Young Oh ◽  
Hong-Yeol Bae ◽  
Jun-Young Jeon ◽  
...  
Keyword(s):  
Residual Stress ◽  
Welding Residual Stress ◽  
Stress Profile ◽  
Pressurized Water ◽  
Butt Weld ◽  
Butt Welds ◽  
Residual Stress Profile ◽  
Dissimilar Metal ◽  
Stress Profiles ◽  
Water Reactors

This paper provides the through-thickness welding residual stress profile in dissimilar metal nozzle butt welds of pressurized water reactors. For systematic investigations of the effects of geometric variables, i.e. the thickness and the radius of the nozzle and the length of the safe end, on welding residual stresses, idealized shape of nozzle is proposed and elastic-plastic thermo-mechanical finite element analyses are conducted. Through-wall welding residual stress profiles for dissimilar metal nozzle butt welds are proposed, which take a modified form of existing welding residual stress profiles developed for austenitic pipe butt weld in R6 code.

Welding Residual Stress and Flaw Evaluation for Dissimilar Metal Welds With Alloy 52 Inlays

2009 ◽  
Author(s):  
D. Rudland ◽  
A. Csontos ◽  
F. Brust ◽  
T. Zhang
Keyword(s):  
Residual Stress ◽  
Nickel Alloy ◽  
Nuclear Power ◽  
Mitigation Strategies ◽  
Welding Residual Stress ◽  
Residual Stress Field ◽  
Pressurized Water ◽  
Dissimilar Metal ◽  
Water Reactors ◽  
Resistant Layer

With the recent occurrences of primary water stress corrosion cracking (PWSCC) at nickel-based dissimilar metal welds (specifically Alloy 82/182 welds) in the nation’s pressurized water reactors (PWRs), the commercial nuclear power industry has been proposing a number of mitigation strategies for dealing with the problem. Some of these methods include Mechanical Stress Improvement Process (MSIP), Full and Optimized Structural Weld Overlay (FSWOL, OWOL) and Inlay and Onlay welds. All of these methods provide either a reduction in the ID residual stress field, (MSIP and WOL) and/or apply a corrosion resistant layer to stop or retard a leak path from forming (WOL, Inlay, Onlay). For the larger bore pipe, i.e. hot leg outlet nozzle, methods such as FSWOL become cost prohibitive due to the amount of weld metal that must be deposited. Therefore, inlay welds are being proposed since only a small layer (3 weld beads) needs to be deposited on the inside surface of the pipe. Currently the ASME code is developing Code Case N-766 ‘Nickel Alloy Reactor Coolant Inlay and Cladding for Repair or Mitigation of PWR Full Penetration Circumferential Nickel Alloy Welds in Class 1 Items.’ This code case is documenting the procedures for applying these inlay welds. As part of a confirmatory analysis, the US NRC staff and its contractor, Engineering Mechanics Corporation of Columbus, (Emc2) have conducted both welding residual stress and flaw evaluation analyses to determine the effectiveness of inlay welds as a mitigative technique. This paper presents the ongoing results from this effort. Using several large bore geometries, detailed welding simulation analyses were conducted on the procedures set forth in draft Code Case N-766. Effects of weld repairs and temper bead welding are included. Using these residual stress results, PWSCC growth analyses were conducted using simulated crack growth rates as a function of chromium content to estimate the time to leakage and rupture for small initial flaws in the inlay. The paper concludes with discussions on the effectiveness of inlays based on these analyses.

Crack Growth Analysis in Alloy 82/182 Butt Weld by Using the Finite Element Alternating Method

2009 ◽  
Author(s):  
Maan-Won Kim ◽  
Young-Jong Kim ◽  
Byoung Chul Kim
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Growth Analysis ◽  
Welding Residual Stress ◽  
Analysis Model ◽  
Element Analysis ◽  
Pressurized Water ◽  
Butt Weld ◽  
Butt Welds ◽  
Alternating Method

Primary water stress corrosion cracking (PWSCC) of Alloy 82/182 butt welds has been a concern for pressurized water reactor (PWR) plants worldwide for the past decade. A lot of works have been performed to calculate exact welding residual stresses and PWSCC growth rate for Alloy 82/182 butt welds. The PWSCC growth analysis of Alloy 82/182 butt welds has been performed by using the Raju-Newman type solutions for the crack tip stress intensity factors (SIFs). In this study, a finite element alternating method (FEAM) was used to calculate the SIFs and crack propagation in Alloy 82/182 butt weld. The FEAM is consisted of two solution parts: an exact theoretical SIF solution for a crack embedded in infinite body and a simple finite element analysis model with coarse mesh for finite body. In this study, the theoretical SIFs were derived by using a dislocation density function. Finite element (FE) analysis was performed to obtain the welding residual stress distribution for a nozzle with Alloy 82/182 butt weld and PWSCC growth analysis was performed by using the FEAM with PWSCC growth model described in MRP reports under welding residual stress along the nozzle thickness.

Finite Element Analyses of Residual Stresses in Typical Welded Joints Used in Nuclear Power Plants and Comparisons With Experiments

2010 ◽  
Author(s):  
Dean Deng ◽  
Kazuo Ogawa ◽  
Nobuyoshi Yanagida ◽  
Koichi Saito
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Residual Stresses ◽  
Welded Joints ◽  
Nuclear Power ◽  
Power Plants ◽  
Butt Joint ◽  
Welding Residual Stress ◽  
Dissimilar Metal ◽  
Water Reactors

Recent discoveries of stress corrosion cracking (SCC) at nickel-based metals in pressurized water reactors (PWRs) and boiling water reactors (BWRs) have raised concerns about safety and integrity of plant components. It has been recognized that welding residual stress is an important factor causing the issue of SCC in a weldment. In this study, both numerical simulation technology and experimental method were employed to investigate the characteristics of welding residual stress distribution in several typical welded joints, which are used in nuclear power plants. These joints include a thick plate butt-welded Alloy 600 joint, a dissimilar metal J-groove set-in joint and a dissimilar metal girth-butt joint. First of all, numerical simulation technology was used to predict welding residual stresses in these three joints, and the influence of heat source model on welding residual stress was examined. Meanwhile, the influence of other thermal processes such as cladding, buttering and heat treatment on the final residual stresses in the dissimilar metal girth-butt joint was also clarified. Secondly, we also measured the residual stresses in three corresponding mock-ups. Finally, the comparisons of the simulation results and the measured data have shed light on how to effectively simulate welding residual stress in these typical joints.

Advanced FEA Modeling of PWSCC Crack Growth in PWR Dissimilar Metal Piping Butt Welds and Application to the Industry Inspection and Mitigation Program

2008 ◽  
Author(s):  
G. White ◽  
J. Broussard ◽  
J. Collin ◽  
M. Klug ◽  
C. Harrington ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Crack Growth ◽  
Circumferential Stress ◽  
Welding Residual Stress ◽  
Sensitivity Matrix ◽  
Element Analysis ◽  
Pressurized Water ◽  
Stability Calculation ◽  
Butt Welds ◽  
Dissimilar Metal

In late summer 2005, the U.S. pressurized water reactor (PWR) fleet imposed mandatory inspection requirements upon itself to address the challenge posed by primary water stress corrosion cracking (PWSCC) in PWR reactor coolant system (RCS) dissimilar metal (DM) piping butt welds. Under this program, the highest temperature, and thus most susceptible, locations have been addressed first. The set of highest temperature locations comprises the DM piping butt welds on the pressurizer. Within three years of promulgating the requirements, all pressurizer locations will have been inspected and nearly 90% of these locations will have been mitigated. In October 2006, several indications of circumferential flaws were reported in the pressurizer nozzles at Wolf Creek. These indications raised questions about the need to accelerate refueling outages or take mid-cycle outages at other plants. In order to address these concerns, an industry effort was undertaken to evaluate the viability of detection of leakage from a through-wall flaw in an operating plant to preclude the potential for rupture of pressurizer nozzle DM welds given the potential concern about growing circumferential stress corrosion cracks. Previous calculations of growth of PWSCC in Alloy 600 wrought materials and Alloy 82/182 weld metal materials have assumed an idealized crack shape, typically a semi-ellipse characterized by a length-to-depth aspect ratio. A key aspect of the industry effort involved developing an advanced finite-element analysis (FEA) methodology for predicting crack growth when loading conditions do not lead to a semi-elliptical flaw shape. The work also investigated an extensive crack growth sensitivity matrix to cover geometry, load, and fabrication factors, as well as the uncertainty in key modeling parameters including the effect of multiple flaw initiation sites in a single weld. Other key activities included detailed welding residual stress simulations covering the subject welds, development of a conservative crack stability calculation methodology, development of a leak rate calculation procedure using existing software tools (EPRI PICEP and NRC SQUIRT), and verification and validation studies. This paper will describe the study undertaken to model growth of circumferential weld cracks and its application to a group of nine PWRs with regard to implementation of the industry inspection and mitigation program [1]. The paper will also explore implementation progress of the industry program as the three-year mark approaches, as well as industry actions to support completion of baseline DM weld examinations.

The Mechanics Basis of Residual Stress Profiles in Proposed API 579 Appendix E

2006 ◽  
Author(s):  
P. Dong ◽  
Z. Cao
Keyword(s):  
Residual Stress ◽  
Heat Input ◽  
Stress Measurement ◽  
Measurement Data ◽  
Stress Profile ◽  
Continuous Change ◽  
Parametric Function ◽  
Residual Stress Profile ◽  
Stress Profiles ◽  
Pipe Geometry

In this paper, the mechanics basis underlying the parametric through-thickness residual stress profiles proposed for the revised API 579 Appendix E are presented. The proposed residual stress profiles are governed to a large extent by a unified parametric function form valid for a broad spectrum of pipe and vessel welds. The functional relationship is established based on the comprehensive knowledge base developed within a recent major international joint industry project (JIP) under the auspice of Pressure Vessel Research Council (PVRC) and a large amount of residuals stress measurement data from recent literature. One of the most important features associated with the proposed revision is that residual stress profile is uniquely determined by two important sets of governing parameters: (1) parameters relevant to pipe geometry, i.e., r/t and t; (2) a parameter related to welding linear heat input Q (J/mm), referred to as the characteristic heat input Qˆ which has a dimension of J/mm3. As a result, the corresponding through-wall residual stress distribution exhibits a continuous change as a function of r/t, t, and Qˆ, instead of falling into a few discrete and unrelated profiles, as seen in the current Codes and Standards.

A New Finite Element Approach Without Chip Formation to Predict Residual Stress Profile Patterns in Metal Cutting

2009 ◽  
Author(s):  
S. Anurag ◽  
Y. B. Guo ◽  
Z. Q. Liu
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Hard Turning ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Stress Profile ◽  
Residual Stress Profile ◽  
Stress Prediction ◽  
Element Approach ◽  
Stress Profiles

Residual stress prediction in hard turning has been recognized as one of the most important and challenging tasks. A hybrid finite element predictive model has been developed with the concept of plowed depth to predict residual stress profiles in hard turning. With the thermo-mechanical work material properties, residual stress has been predicted by simulating the dynamic turning process followed by a quasi-static stress relaxation process. The residual stress profiles were predicted for a series of plowed depths potentially encountered in machining. The predicted residual stress profiles agree with the experimental one in general. A transition of residual stress profile has been recovered at the critical plowed depth. In addition, the effects of cutting speed, friction coefficient and inelastic heat coefficient on residual stress profiles have also been studied and explained.

Detailed Analysis of Residual Stress Profile at Micro-Scale in Transmission Laser Bonded Titanium/Polyimide System

2008 ◽  
Author(s):  
Ankitkumar P. Dhorajiya ◽  
Mohammed S. Mayeed ◽  
Gregory W. Auner ◽  
Ronald J. Baird ◽  
Golam M. Newaz ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Laser Beam ◽  
Stress Analysis ◽  
Detailed Analysis ◽  
Stress Profile ◽  
Fe Model ◽  
Residual Stress Profile ◽  
Stress Profiles ◽  
Residual Stress Analysis

Detailed analysis of residual stress profile due to laser micro-joining of two dissimilar biocompatible materials, polyimide (PI) and titanium (Ti), is vital for the long-term application of bio-implants. In this work, a comprehensive three dimensional (3D) transient model for sequentially coupled thermo-mechanical analysis of transmission laser micro-joining of two dissimilar materials has been developed by using the finite element (FE) code ABAQUS, along with a moving Gaussian laser heat source. The laser beam (wavelength of 1100 nm and diameter of 0.2 mm), moving at an optimized velocity, passes through the transparent PI, gets absorbed by the absorbing Ti, and eventually melts the PI to form the bond. The laser bonded joint area is 6.5 mm long by 0.3 mm wide. First the transient heat transfer analysis is performed and the nodal temperature profile has been achieved, and then used as an input for the residual stress analysis. Non-uniform mixed meshes have been used and optimized to formulate the 3D FE model and ensure very refined meshing around the bond area. Heat resistance between the two materials has been modeled by using the thermal surface interaction technique, and melting and solidification issues have been approximated in the residual stress analysis by using the appropriate material properties at corresponding temperature. First the model has been used to observe a good bonding condition with the laser parameters like laser traveling speed, power, and beam diameter (burnout temperature of PI > maximum temperature of PI achieved during heating > melting temperature of PI) and a good combination has been found to be 100 mm/min, 3.14 W and 0.2 mm respectively. Using this combination of parameters in heating, the residual stress profile of the laser-micro-joint has been calculated using FE model after cooling the system down to room temperature of 27 °C and analyzed in detail by plotting the stress profiles on the Ti and PI surfaces. Typically the residual stress profiles on the PI surface show low value in the middle, increase to higher values at about 160 μm from the centerline of the laser travel symmetrically at both sides, and to the contrary, on Ti surface show higher values near the centerline of traveling laser beam. The residual stresses have slowly dropped away on both the surfaces as the distance from the bond region increased further. Maximum residual stresses on both the Ti and PI surfaces are at the end of the laser travel, and are in the orders of the yield stresses of respective materials.

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