Effect of Residual Stress on Crack Growth Specimens Fabricated From Weld Metal

2011 ◽  
Author(s):  
Matthew Kerr ◽  
Darrell Dunn ◽  
Mitchell D. Olsen ◽  
Bogdan Alexandreanu ◽  
Michael R. Hill ◽  
...  
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Weld Metal ◽  
Crack Growth ◽  
Nuclear Regulatory Commission ◽  
Compact Tension ◽  
Slitting Method ◽  
Stress Profiles ◽  
Regulatory Commission ◽  
Made In

Slitting method residual stress measurements (Hill Engineering and UC Davis) and finite element weld simulation (US Nuclear Regulatory Commission) have been conducted in order to evaluate both the residual stress intensity factor and residual stress profiles for two compact tension coupon blanks. The two compact tension coupon blanks were provided by Argonne National Lab (ANL) and are similar to coupons used in ongoing stress corrosion cracking (SCC) studies in weld metal. The experimental data and finite element results are in reasonable agreement, showing similar trends in calculated residual stress profiles. Results from the work document the effect of specimen size and location on residual stress profiles, and could be used to determine the degree to which residual stresses affect crack growth measurements made in similar coupons.

Crack Growth Rates for Evaluating PWSCC of Thick-Wall Alloy 690 Material and Alloy 52, 152, and Variant Welds

2017 ◽  
Author(s):  
Amanda R. Jenks ◽  
Glenn A. White ◽  
Paul Crooker
Keyword(s):  
Crack Growth ◽  
Growth Rates ◽  
Nuclear Regulatory Commission ◽  
Compact Tension ◽  
Thick Wall ◽  
Pressurized Water ◽  
Alloy 690 ◽  
Data Points ◽  
Regulatory Commission ◽  
Crack Growth Rates

Due to the widespread use of thick-wall Alloy 690 and its corresponding weld metals Alloys 52 and 152 in various replacement, repair, mitigation, and new plant pressurized water reactor (PWR) applications, there is a need in the industry for an equation or methodology for predicting crack growth rates (CGRs) for primary water stress corrosion cracking (PWSCC) of these materials. Although there have been no indications of PWSCC reported in these materials in PWRs to date, there is the possibility that such an indication could be reported in the future or the possibility that a manufacturing defect could be conservatively interpreted as PWSCC. Crack growth rates are thus needed to support leaving such an indication in service for a justified period of time. In addition, safety assessments of hypothetical PWSCC flaws require prediction of PWSCC crack growth rates for these materials, so as to set appropriate inspection intervals. Current inspection intervals were selected to be conservative pending a consensus CGR model. Example applications for which PWSCC CGRs are needed to determine appropriate reexamination intervals include Alloy 690 penetration nozzles attached to the inside of the reactor pressure vessel top head with Alloy 52/152/variant welds, and Alloy 52/152/variant weld inlays and onlays used to mitigate Alloy 82/182 piping butt welds. An international PWSCC CGR Expert Panel was organized by EPRI, with the participation of national laboratories sponsored by the US Nuclear Regulatory Commission (NRC),1 to support the development of such PWSCC CGR equations. A database of over 500 Alloy 690 CGR data points and over 130 Alloy 52/152 CGR data points using thick-wall compact tension specimens from seven research laboratories was compiled, scored for data quality, and assessed to determine the effects of numerous parameters such as temperature, crack-tip stress intensity factor, yield strength, and crack orientation. The methodology and results of these statistical analyses are presented in this paper. It should be noted that this paper provides a status of the ongoing work, which is planned for completion in late 2017.

Exploring Finite Element Validation for Weld Residual Stress Prediction

2018 ◽  
Author(s):  
Michael L. Benson ◽  
Patrick A. C. Raynaud ◽  
Jay S. Wallace
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Uncertainty Quantification ◽  
Nuclear Regulatory Commission ◽  
Weld Residual Stress ◽  
Rigorous Framework ◽  
Stress Prediction ◽  
Regulatory Commission ◽  
Compare And Contrast ◽  
The U.S

The U.S. Nuclear Regulatory Commission staff has analyzed results from the weld residual stress round robin study, conducted in 2014. An uncertainty quantification scheme was applied to the dataset in order to compare and contrast results from independent analysts. The uncertainty quantification scheme provides a rigorous framework within which to make judgement calls about appropriate modeling guidelines and potential validation schemes. This paper will explore various options for guidelines and validation approaches, as informed by a statistical analysis of the dataset.

Finite element modeling of residual stress profile patterns in hard turning

2009 ◽  
Vol 24 (S1) ◽  
pp. S22-S25
Author(s):  
Y. B. Guo ◽  
S. Anurag
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Finite Element Modeling ◽  
Hard Turning ◽  
Internal State ◽  
Stress Profile ◽  
Surface Residual Stress ◽  
Mechanical Coupling ◽  
Element Modeling ◽  
Stress Profiles

Hard turning, i.e., turning hardened steels, may produce the unique “hook” shaped residual stress (RS) profile characterized by surface compressive RS and subsurface maximum compressive RS. However, the formation mechanism of the unique RS profile is not yet known. In this study, a novel hybrid finite element modeling approach based on thermal-mechanical coupling and internal state variable plasticity model has been developed to predict the unique RS profile patterns by hard turning AISI 52100 steel (62 HRc). The most important controlling factor for the unique characteristics of residual stress profiles has been identified. The transition of maximum residual stress at the surface to the subsurface has been recovered by controlling the plowed depth. The predicted characteristics of residual stress profiles favorably agree with the measured ones. In addition, friction coefficient only affects the magnitude of surface residual stress but not the basic shape of residual stress profiles.

STYLE: Modelling of the Extraction of Bend Specimens From Repair Weld and the Influence of Residual Stress on Fracture Testing

2014 ◽  
Author(s):  
Peter James ◽  
Mike Ford
Keyword(s):  
Residual Stress ◽  
Crack Growth ◽  
Large Scale ◽  
Crack Depth ◽  
Compact Tension ◽  
Materials Testing ◽  
Ductile Crack ◽  
Local Approach ◽  
Ductile Crack Growth ◽  
Low Constraint

Within the EU 7th framework programme, STYLE, a number of large-scale tests have been performed. One of these tests, Mock-Up 2 (MU-2), was performed on a through wall crack located at a repair weld adjacent to a multi-pass narrow-gap weld. The aim of MU-2 was to investigate ductile crack growth under conditions with significant levels of residual stress. As part of the materials testing programme, low-constraint fracture specimens (three-point bend specimens with a/t=0.1) were extracted from the weld to test the weld materials fracture toughness. An overview of these tests is provided here. However, these low constraint tests demonstrated somewhat unusual fatigue crack growth on inserting the crack, leading to the crack depth being shorter in the centre of the specimens to the outside. Subsequently, although it has not been possible to use these specimens to determine the materials J-R curve, it does provide a features test for ductile modelling with the Gurson-Tvergaard-Needleman (GTN) local approach model for ductile crack growth. This paper provides an overview of the modelling associated to understand these observations, including an estimate of the retained residual stress, fatigue growth estimates and subsequent ductile modelling. An overview of the calibration of the GTN model is also provided using the weld material’s tensile tests, high constraint compact-tension tests and MU-2.

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.

Effects of Weld Geometry on Residual Stress and Crack Driving Force for Centerhole Control Rod Drive Mechanism Nozzles: Part I — Weld Residual Stress

2005 ◽  
Author(s):  
Wentao Cheng ◽  
David L. Rudland ◽  
Gery Wilkowski ◽  
Wallace Norris
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Driving Force ◽  
Nuclear Regulatory Commission ◽  
Crack Driving Force ◽  
Control Rod ◽  
Drive Mechanism ◽  
Weld Geometry ◽  
Weld Residual Stress ◽  
Regulatory Commission

The U.S. Nuclear Regulatory Commission (NRC) has undertaken a program to assess the integrity of control rod drive mechanism (CRDM) nozzles in existing plants that are not immediately replacing their RPV heads. This two-part paper summarizes some of the efforts undertaken on the behalf of the U.S.NRC for the development of detailed residual stress and circumferential crack-driving force solutions to be used in probabilistic determinations of the time from detectable leakage to failure. In this first paper, the finite element (FE) simulations were conducted to investigate the effects of weld geometry on the residual stresses in the J-weld for a centerhole CRDM nozzle. The variables of weld geometry included three weld heights (weld sizes) and three groove angles for each weld height while keeping the same weld size. The analysis results indicate that the overall weld residual stress decreases as the groove angle increases and higher residual stress magnitude is associated with certain weld height. The results also reveal that the axial residual stresses in the Alloy 600 tube are very sensitive to the weld height, and that the tube hoop stresses above the J-weld root increase with the increasing weld height.

Creep Crack Initiation in a Weld Steel: Effects of Residual Stress

2005 ◽  
Author(s):  
Noel P. O’Dowd ◽  
Kamran M. Nikbin ◽  
Farid R. Biglari
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Crack Initiation ◽  
Equivalent Stress ◽  
Stress Triaxiality ◽  
Compact Tension ◽  
Residual Stress Field ◽  
Element Analysis ◽  
Creep Ductility ◽  
Uniaxial Test

In this paper, the effect of residual stress on the initiation of a crack at high temperature in a Type 347 austenitic steel weld is examined using the finite element method. Both two and three dimensional analyses have been carried out. Residual stresses have been introduced by prior mechanical deformation, using a previously developed notched compact tension specimen. It has been found that for the 347 weld material, peak stresses in the vicinity of the notch are approximately three times the yield strength at room temperature and the level of stress triaxiality (ratio between hydrostatic and equivalent stress) is approximately 1 (considerably higher than that for a uniaxial test). The finite element analysis includes the effects of stress redistribution and damage accumulation under creep conditions. For the case examined the analysis predicts that crack initiation will occur under conditions of stress relaxation if the uniaxial creep ductility of the material is less than 2.5%. Furthermore, the predicted life of the component under constant load (creep conditions) is significantly reduced due to the presence of the residual stress field.

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