ADIMEW Test: Assessment of a Cracked Dissimilar Metal Weld Assembly

2004 ◽  
Author(s):  
John B. Wintle ◽  
Bridget Hayes ◽  
Martin R. Goldthorpe
Keyword(s):  
Residual Stresses ◽  
Material Properties ◽  
Nuclear Power ◽  
Large Scale ◽  
Research Programme ◽  
Element Analysis ◽  
Dissimilar Metal ◽  
Four Point Bending ◽  
Dissimilar Metal Weld ◽  
Metal Weld

ADIMEW (Assessment of Aged Piping Dissimilar Metal Weld Integrity) was a three-year collaborative research programme carried out under the EC 5th Framework Programme. The objective of the study was to advance the understanding of the behaviour and safety assessment of defects in dissimilar metal welds between pipes representative of those found in nuclear power plant. ADIMEW studied and compared different methods for predicting the behaviour of defects located near the fusion boundaries of dissimilar metal welds typically used to join sections of austentic and ferritic piping operating at high temperature. Assessment of such defects is complicated by issues that include: severe mis-match of yield strength of the constituent parent and weld metals, strong gradients of material properties, the presence of welding residual stresses and mixed mode loading of the defect. The study includes the measurement of material properties and residual stresses, predictive engineering analysis and validation by means of a large-scale test. The particular component studies was a 453mm diameter pipe that joins a section of type A508 Class 3 ferritic pipe to a section of type 316L austentic pipe by means of a type 308 austentic weld with type 308/309L buttering laid on the ferritic pipe. A circumferential, surface-breaking defect was cut using electro discharge machining into the 308L/309L weld buttering layer parallel to the fusion line. The test pipe was subjected to four-point bending to promote ductile tearing of the defect. This paper presents the results of TWI contributions to ADIMEW including: fracture toughness testing, residual stress measurements and assessments of the ADIMEW test using elastic-plastic, cracked body, finite element analysis.

Validation of Welding Residual Stress Model Using Results From a Pressurizer Surge Nozzle Mockup

2011 ◽  
Author(s):  
Doug Killian
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Residual Stresses ◽  
Crack Growth ◽  
Material Properties ◽  
Welding Residual Stress ◽  
Stress Model ◽  
Dissimilar Metal ◽  
Dissimilar Metal Weld ◽  
Metal Weld

Although numerical welding simulation is now commonly used in the nuclear industry to predict residual stresses in reactor vessels and associated piping components, there are currently no universally accepted guidelines for performing such analysis. Moreover, due to the complexity of the calculations and varying analytical procedures among analysts, there remains a need to validate predictions of residual stress against benchmark studies. As part of an industry initiative to manage the degradation of dissimilar metal welds in pressurized water reactor piping that are susceptible to primary water stress corrosion cracking, the U.S Nuclear Regulatory Commission embarked on a multi-phased program to validate welding residual stress models. The aim of Phase II of this program is to obtain measured residual stresses from a pressurizer surge nozzle dissimilar metal weld mockup for use in comparisons with numerically predicted stresses. This paper presents results of finite element analysis for various stages during the fabrication of a 14–inch pressurizer surge nozzle mockup, including an Alloy 82 dissimilar metal weld between a stainless steel safe end and carbon steel nozzle, an inside surface weld repair (back weld) and fill-in weld (weld build-up), and a stainless steel “field” weld attaching a section of straight pipe to the safe end. The NRC validation program was structured to allow participants to first calculate results using their own material properties, and then tune their welding simulations to thermocouple data. This was followed by reanalysis using NRC-supplied material properties. The program was conducted as a round robin analysis among an international group of participants and formatted as a blind validation project wherein results were submitted to the NRC prior to receipt of thermocouple and material property data. Results were obtained for both kinematic and isotropic hardening rules to study the effect of these two extreme measures of material characterization on the development of residual stress. Predicted stresses are then compared to measured stress data obtained by the deep-hole drilling technique at multiple locations through the thickness of the weld. The NRC residual stress model validation project serves as a valuable contribution to the understanding of how residual stresses are developed in dissimilar metal welds. The correlation of calculated residual stresses with measured data from a relevant mockup also serves to increase confidence in predicting crack growth in these primary pressure boundary welds by removing much of the uncertainty previously associated with residual stress input to crack growth analysis.

Finite Element Analysis of a Full-Scale Test of a Cracked Dissimilar Metal Weld for Aging Nuclear Power Piping and Fracture Failure Assessment

2015 ◽  
Author(s):  
Lingfu Zeng ◽  
Chouping Luo ◽  
Lennart G. Jansson ◽  
Patrik Gyllén
Keyword(s):  
Finite Element Analysis ◽  
Mixed Mode ◽  
Nuclear Power ◽  
Mode I ◽  
Element Analysis ◽  
Dissimilar Metal ◽  
Fracture Failure ◽  
Failure Assessment ◽  
Dissimilar Metal Weld ◽  
Metal Weld

This report addresses a mixed mode driven cracking and its fracture failure assessment for applications in aging nuclear power facilities. Following our earlier discussion on the use of mode-I based criteria in the current practice of fracture assessments, a finite element analysis of a full-scale laboratory test, a Benchmark four-point bending test of a straight pipe with an obliquely inserted crack in a dissimilar metal weld of ferritic steel (A508) and austenitic steel (316L), together with weld (308L) and buttering material (309L/308L), is conducted. The behavior of the crack front at the load level, at which crack initiation is observed in the test, such as stress intensities (KI, KII, KIII), J-integrals and other relevant parameters along the crack front, are computed. Crack initiation assessments are thereafter made using three alternatives: (1) Mode I cracking; (2) Mixed mode cracking; (3) An empirical approach suggested for accounting the mixed mode effect using a so-called R6-method. The results confirm our earlier observation: For cases when mixed mode loading conditions are significant, (i) the fracture initiation predicted by using J-integral based mixed mode cracking criteria can approximately be achieved by using the R6-empirical approach for the mixed mode cracking; (ii) it is not conservative to use a purely mode-I based criterion for the evaluation of the fracture failure assessment for typical problems of mixed mode driven cracking.

Effectiveness of Excavate and Weld Repair on a Large Diameter Piping Dissimilar Metal Weld by Finite Element Analysis

2012 ◽  
Author(s):  
Francis H. Ku ◽  
Pete C. Riccardella ◽  
Aparna Alleshwaram ◽  
Eric Willis
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Large Diameter ◽  
Weld Repair ◽  
Element Analysis ◽  
Dissimilar Metal ◽  
Primary Water ◽  
Dissimilar Metal Weld ◽  
Metal Weld

Finite element weld residual stress analyses are performed to investigate the effectiveness of a newly proposed repair option for primary water stress corrosion cracking (PWSCC) in dissimilar metal welds in PWRs: Excavate and Weld Repair (EWR). Analyses are performed on a 30″ (762mm) outside diameter (OD) and 3″ (76mm) thick stainless steel pipe connected to a low alloy steel nozzle with a dissimilar metal weld (DMW). Eight EWR cases are analyzed to evaluate the sensitivities in weld residual stresses due to variations in the width and depth of the EWR, including cases with and without a thin weld cap on top of the DMW. The results demonstrate that a wide EWR that extends beyond the original width of the DMW provides the maximum residual stress benefits to the DMW, in terms of reducing the as-welded residual stresses. It is also found that the presence of the weld cap yields only marginal residual stress benefits.

scholarly journals Experimental Characterisation and Numerical Modelling of Residual Stresses in a Nuclear Safe-End Dissimilar Metal Weld Joint

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1298
Author(s):  
Shuyan Zhang ◽  
Zhuozhi Fan ◽  
Jun Li ◽  
Shuwen Wen ◽  
Sanjooram Paddea ◽  
...  
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Weld Joint ◽  
Steel Tube ◽  
Contour Method ◽  
Fe Modelling ◽  
Dissimilar Metal ◽  
Dissimilar Metal Weld ◽  
Metal Weld

In this study, a mock-up of a nuclear safe-end dissimilar metal weld (DMW) joint (SA508-3/316L) was manufactured. The manufacturing process involved cladding and buttering of the ferritic steel tube (SA508-3). It was then subjected to a stress relief heat treatment before being girth welded together with the stainless steel tube (316L). The finished mock-up was subsequently machined to its final dimension. The weld residual stresses were thoroughly characterised using neutron diffraction and the contour method. A detailed finite element (FE) modelling exercise was also carried out for the prediction of the weld residual stresses resulting from the manufacturing processes of the DMW joint. Both the experimental and numerical results showed high levels of tensile residual stresses predominantly in the hoop direction of the weld joint in its final machined condition, tending towards the OD surface. The maximum hoop residual stress determined by the contour method was 500 MPa, which compared very well with the FE prediction of 467.7 Mpa. Along the neutron scan line at the OD subsurface across the weld joint, both the contour method and the FE modelling gave maximum hoop residual stress near the weld fusion line on the 316L side at 388.2 and 453.2 Mpa respectively, whereas the neutron diffraction measured a similar value of 480.6 Mpa in the buttering zone near the SA508-3 side. The results of this research thus demonstrated the reasonable consistency of the three techniques employed in revealing the level and distribution of the residual stresses in the DMW joint for nuclear applications.

Study of the Stress State of a Dissimilar Metal Weld Due to Manufacturing and Operational Conditions

2022 ◽  
Author(s):  
Bernadett Spisák ◽  
Zoltán Bézi ◽  
Szabolcs Szávai
Keyword(s):  
Residual Stresses ◽  
Load Capacity ◽  
Maximum Load ◽  
Operational Conditions ◽  
Manufacturing Method ◽  
Dissimilar Metal ◽  
Welding Defects ◽  
Complex Procedure ◽  
Dissimilar Metal Weld ◽  
Metal Weld

Welding is accompanied by the presence of weld residual stresses, which in case of dissimilar metal welds even with post weld heat treatment cannot be removed completely therefore they should be considered when assessing possible welding defects. The measurement of residual stress in metal weld is a very complex procedure and also in the investigated case could not be carried out as it is the part of a working plant. However, by modelling these processes, the residual stresses and deformation of the components caused by this manufacturing method can be determined. It is important to calculate these values as accurately as possible to determine the maximum load capacity of the structure. The structure under examination was the dissimilar metal weld of a VVER-440 steam generator. 2D simulations were performed, where temperature and phase-dependent material properties were implemented. Different loading scenarios were considered in the numerical analysis. The results can be useful to determine the real loading conditions of a given component and can be used to predict stress corrosion crack initiation locations, as well as to evaluate the lifetime and failure mode prediction of welded joints.

High-Temperature Constitutive Behavior of Austenitic Stainless Steel for Weld Residual Stress Modeling

2012 ◽  
Author(s):  
Dongxiao Qiao ◽  
Wei Zhang ◽  
Zhili Feng
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
High Temperature ◽  
Residual Stresses ◽  
Constitutive Rule ◽  
Dissimilar Metal ◽  
Weld Residual Stress ◽  
Dissimilar Metal Weld ◽  
Metal Weld

Weld residual stress is a major driving force for initiation and growth of primary water stress corrosion cracking (PWSCC), which is a critical challenge for weld integrity of reactor pressure vessel nozzles in nuclear industry. Predicting weld residual stresses for the purpose of understanding and mitigating PWSCC requires the knowledge of material constitutive rule especially strain hardening behavior over a wide range of temperatures. Though it is adequate for describing deformation at low temperature, the conventional, rate-independent, elastic-plastic constitutive rule falls short in predicting the strong microstructure-mechanical interaction such as the softening due to recovery (dislocation annihilation and realignment) and recrystallization at elevated temperature in welding. To quantify the extent of softening under temperature and strain conditions relevant to welding, a framework has been developed by combining advanced experimental techniques and finite element modeling. First, physical simulation in a Gleeble testing machine is used to simulate the temperature transients typical of dissimilar metal weld by subjecting round tensile bar shaped specimens to rapid heating and cooling. Second, the digital image correlation (DIC) technique is used to map the non-uniform strain field and extract local strain history needed for accurately determining the true stress vs. true strain curve of softened material. Third, the thermally-mechanically processed specimens are characterized metallographically to correlate the microstructure changes to the measured stress-strain behavior. Finally, a thermal-stress finite element model of three-bar frame is used to study the effect of softening on the predicted weld residual stresses. As a first step toward developing the much-needed, comprehensive material constitutive relation database for dissimilar metal weld, the framework has been applied to study AISI 304L austenitic stainless steel. The extent of softening due to different duration of high-temperature exposure is studied and its influence on final residual stresses is discussed.

Development and Validation of Analysis Method for Simulating Residual Stresses in Dissimilar Metal Pipe Butt Welds

2008 ◽  
Author(s):  
Douglas E. Killian ◽  
Samer H. Mahmoud
Keyword(s):  
Residual Stresses ◽  
Fabrication Process ◽  
Research Centre ◽  
Analysis Method ◽  
Weld Repair ◽  
Butt Weld ◽  
Dissimilar Metal ◽  
Dissimilar Metal Weld ◽  
Temperature And Pressure ◽  
Metal Weld

It is now accepted practice in the commercial nuclear power industry to numerically simulate the residual stresses developed during welding of bimetallic piping components. A common example is the Alloy 82/182 shop weld between a low alloy steel nozzle and a stainless steel safe end. Piping is attached to the nozzle safe end by a separate girth butt weld in the field. The safe end to pipe weld influences stresses in the nozzle to safe end weld only for relatively short safe ends. Alloy 600 base metal material and its associated welds are susceptible to primary water stress corrosion cracking (PWSCC) at elevated levels of stress. It is therefore necessary to model each step of the fabrication process to capture the path dependent accumulation of stress and strain in the welded components, and to simulate the pre-service test loads and operating temperature and pressure loads. The fabrication process includes the build up of butter material on the nozzle prior to heat treatment and the deposition of weld metal in a single V-groove between the butter and safe end. This is followed by one or more repair welds to remove welding defects. The welded component is then subjected to a shop hydrostatic test pressure equal to 125 percent of the design pressure. Following several heatup and cooldown cycles to simulate “shakedown” of pre-service stresses, stresses in the vicinity of the weld are determined at operating conditions of temperature and pressure in order to access the susceptibility of the weld and butter to PWSCC. This paper discusses the analytical methodology used to numerically simulate welding residual stresses using the ANSYS general purpose computer code. The method is then applied to two-dimensional axisymmetric welding simulations, which are adequate to investigate most girth butt weld piping components, although it may be necessary to make conservative assumptions regarding weld repair configurations. Numerical results are used to characterize the effects of weld repair, pre-service loads, and cyclic loading on the final state of operating stresses for sustained loading conditions. The analysis method is validated using results from large scale tests performed by the European Commission Joint Research Centre as part of its Assessment of Aged Piping Dissimilar Metal Weld (ADIMEW) project. Residual stresses are predicted for a ferritic-to-austenitic dissimilar metal weld mockup and compared against results from neutron diffraction measurements.

An Approach to Controlling Inaccessible Regions for Inspection Defined by Rules on Fitness-For-Service in Japan

2009 ◽  
Author(s):  
Takashi Ota ◽  
Koji Dozaki
Keyword(s):  
Ultrasonic Testing ◽  
Nuclear Power ◽  
Industrial Safety ◽  
Current Status ◽  
Inlet Pipe ◽  
Dissimilar Metal ◽  
Primary Water ◽  
Alternative Measures ◽  
Dissimilar Metal Weld ◽  
Metal Weld

On September 2007, Primary Water Stress Corrosion Cracking (PWSCC) flaws were found on the dissimilar metal weld of the steam generator (SG) inlet pipe nozzles of Tsuruga-2. Following the Tsuruga-2, similar cases were found in some other plants. These cracks were located in inaccessible regions by Ultrasonic Testing (UT) examination applied from the outer surface. Triggered by these cases, the Nuclear and Industrial Safety Agency (NISA), Japanese regulator of nuclear industries, directed nuclear power plant owners to investigate current status of these inaccessible regions for inspection defined by rules on fitness-for-service in Japan, and required to show developing plan on alternative measures of inspection for UT-exempted welds. On the other hand, the study to manage inaccessible regions in the rules on fitness-for-service has been started. The authors consider and propose a possible approach for modified rules of inspection in order to make control of these inaccessible regions.

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