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.

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.

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.

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.

Development of a Residual Stress Simulation Benchmark for a Single Bead-on-Plate Weldment

2006 ◽  
Author(s):  
Peter J. Bouchard ◽  
Lyndon Edwards ◽  
Anastasius G. Youtsos ◽  
Roger Dennis
Keyword(s):  
Residual Stress ◽  
Assessment Procedure ◽  
Defect Assessment ◽  
Best Estimate ◽  
Weld Residual Stress ◽  
Single Bead ◽  
Stress Prediction ◽  
Stainless Steel Bead ◽  
Stress Simulation ◽  
Network Project

Finite element weld residual stress modelling procedures involve complex non-linear analyses where many assumptions and approximations have to be made by the analyst. Weld modelling guidelines for inclusion in the R6 defect assessment procedure are in preparation and will be accompanied by a series of validation benchmarks that can be used to evaluate the accuracy of weld modelling procedures and assess their suitability for use in fracture assessments. It is intended to base one of the benchmarks on a stainless steel bead-on-plate weldment that has been extensively studied by members of Task Group 1 of the NeT European Network project. This paper uses round robin residual stress measurements from the NeT project to derive a statistically based ‘best estimate’ distribution of transverse stress passing through the wall-section at mid-length of the bead-on-plate weldment. The accuracy of a state-of-the-art residual stress prediction is benchmarked against the best estimate measurements using a root mean square error analysis and comparisons of decomposed components of stress. The appropriateness of using the predicted residual stresses in fracture assessments is assessed by comparing stress intensity factors based on the measured and predicted distributions of stress. The results from these studies will be used to help establish accuracy targets and acceptance criteria for the welding benchmark.

Two Case Studies in 3-D Residual Stress Prediction for Nuclear Power Applications

2016 ◽  
Author(s):  
Michael L. Benson ◽  
Patrick A. C. Raynaud ◽  
Frederick W. Brust
Keyword(s):  
Residual Stress ◽  
Nuclear Power ◽  
Three Dimensional ◽  
Repair Process ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling ◽  
Weld Residual Stress ◽  
Plant Operations ◽  
Stress Prediction ◽  
Residual Stress Modeling

Residual stress prediction contributes to nuclear safety by enabling engineering estimates of component service lifetimes. Subcritical crack growth mechanisms, in particular, require residual stress assumptions in order to accurately model the degradation phenomena. In many cases encountered in nuclear power plant operations, the component geometry permits two-dimensional (i.e., axisymmetric) modeling. Two recent examples, however, required three-dimensional modeling for a complete understanding of the weld residual stress distribution in the component. This paper describes three-dimensional weld residual stress modeling for two cases: (1) branch connection welds off reactor coolant loop piping and (2) a mockup to demonstrate the effectiveness of the excavate and weld repair process.

scholarly journals Human Performance Analysis of Industrial Radiography Radiation Exposure Events

1995 ◽  
Vol 39 (9) ◽  
pp. 491-495
Author(s):  
Wendy J. Reece ◽  
Susan G. Hill
Keyword(s):  
Information Processing ◽  
Performance Analysis ◽  
Radiation Exposure ◽  
Human Performance ◽  
Nuclear Regulatory Commission ◽  
Industrial Radiography ◽  
Event Trees ◽  
Regulatory Commission ◽  
Descriptive Models ◽  
The U.S

A set of radiation overexposure event reports were reviewed as part of a program to examine human performance in industrial radiography for the U.S. Nuclear Regulatory Commission. Incident records for a seven year period were retrieved from an event database. Ninety-five exposure events were initially categorized and sorted for further analysis. Descriptive models were applied to a subset of severe overexposure events. Modeling included: (1) operational sequence tables to outline the key human actions and interactions with equipment, (2) human reliability event trees, (3) an application of an information processing failures model, and (4) an extrapolated use of the error influences and effects diagram. Results of the modeling analyses provided insights into the industrial radiography task and suggested areas for further action and study to decrease overexposures.

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