Simulation and Measurement of Through-Wall Residual Stresses in a Structural Weld Overlaid Pressurizer Nozzle

2010 ◽  
Author(s):  
Stephen Marlette ◽  
Paula Freyer ◽  
Michael Smith ◽  
Andrew Goodfellow ◽  
Xavier Pitoiset ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Residual Stresses ◽  
Hole Drilling ◽  
Steel Weld ◽  
Deep Hole ◽  
Deep Hole Drilling ◽  
Dissimilar Metal ◽  
Stainless Steel Weld ◽  
Stress Profiles

Full structural weld overlays (FSWOLs) have been used extensively as a repair/mitigation technique for primary water stress corrosion cracking (PWSCC) in pressurizer nozzle dissimilar metal (DM) welds. To support an approved FSWOL design and safety submission for British Energy pressurized water reactor (PWR) nozzles, an in-depth evaluation was performed to assess the effects of a FSWOL on the through-wall residual stress distribution in safety/relief pressurizer nozzles. Two safety/relief pressurizer nozzle mockups were fabricated based on British Energy’s PWR nozzle design. One mockup included the nozzle to safe-end DM weld and the safe-end to stainless steel weld while the second mockup included the DM weld, the stainless steel weld and a Westinghouse-designed structural weld overlay. The mockups were fabricated utilizing materials and techniques that represented the plant-specific nozzles as closely as possible and detailed welding parameters were recorded during fabrication. All welds were subsequently nondestructively evaluated (NDE). A thorough review of the detailed fabrication records and the NDE results was performed and several circumferential positions were selected on each mockup for subsequent residual stress measurement. The through-wall residual stress profiles were experimentally measured through the DM weld centerline at the selected circumferential positions using both the deep hole drilling (DHD) and incremental deep hole drilling (iDHD) measurement techniques. In addition to experimental residual stress measurements, the through-wall residual stress profiles were simulated using a 2-D axisymmetric ANSYS™ finite element (FE) model. The model utilized kinematic strain hardening and the temperature constraint method which greatly simplified the simulation as compared to detailed heat source modeling methods. A range of residual weld stress profiles was calculated by varying the time at which the temperature constraints were applied to the model. The simulation results were compared to the measurement results. It was found that the effects of the FSWOL were principally three fold. Specifically, the FSWOL causes a much deeper compressive stress field, i.e., the overlay shifts tension out towards the outside diameter surface. Further, the FSWOL reduces tension in the underlying dissimilar metal weld, and finally, the FSWOL causes higher peak compressive and tensile residual stresses, both of which move deeper into the nozzle wall after the overlay is applied. Relatively good agreement was observed between the FE results and the measurements results.

Simulation and Measurement of Through–Wall Residual Stresses in a Structural Weld Overlaid Pressurizer Nozzle

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Stephen Marlette ◽  
Paula Freyer ◽  
Michael Smith ◽  
Andrew Goodfellow ◽  
Xavier Pitoiset ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Residual Stresses ◽  
Hole Drilling ◽  
Steel Weld ◽  
Deep Hole ◽  
Deep Hole Drilling ◽  
Dissimilar Metal ◽  
Stainless Steel Weld ◽  
Stress Profiles

Full structural weld overlays (FSWOLs) have been used extensively as a repair/mitigation technique for primary water stress corrosion cracking in pressurizer nozzle dissimilar metal (DM) welds. To support an approved FSWOL design and safety submission for British Energy pressurized water reactor (PWR) nozzles, an in-depth evaluation was performed to assess the effects of a FSWOL on the through wall residual stress distribution in safety/relief pressurizer nozzles. Two safety/relief pressurizer nozzle mockups were fabricated based on British Energy’s PWR nozzle design. One mockup included the nozzle to safe-end DM weld and the safe-end to stainless steel weld, while the second mockup included the DM weld, the stainless steel weld, and a Westinghouse designed structural weld overlay. The mockups were fabricated utilizing materials and techniques that represented the plant specific nozzles as closely as possible and detailed welding parameters were recorded during fabrication. All welds were subsequently nondestructively evaluated (NDE). A thorough review of the detailed fabrication records and the NDE results was performed and several circumferential positions were selected on each mockup for subsequent residual stress measurement. The through wall residual stress profiles were experimentally measured through the DM weld centerline at the selected circumferential positions using both the deep-hole drilling (DHD) and incremental deep-hole drilling (iDHD) measurement techniques. In addition to experimental residual stress measurements, the through-wall residual stress profiles were simulated using a 2D axisymmetric ansys™ finite element (FE) model. The model utilized the application of temperature constraints on the weld elements to simulate the thermal welding cycle which greatly simplified the simulation as compared with detailed heat source modeling methods. Kinematic strain hardening was used for material modeling of the weld and base metals. A range of residual weld stress profiles was calculated by varying the time at which the temperature constraints were applied to the model. The simulation results were compared with the measurement results. It was found that the effects of the FSWOL were principally threefold. Specifically, the FSWOL causes a much deeper compressive stress field, i.e., the overlay shifts tension out toward the outside diameter (OD) surface. Furthermore, the FSWOL reduces tension in the underlying dissimilar metal weld, and finally, the FSWOL causes higher peak compressive and tensile residual stresses, both of which move deeper into the nozzle wall after the overlay is applied. Relatively good agreement was observed between the FE results and the measurements results.

Analysis and Optimization of the Deep-Hole Drilling Technique in Measuring Complex Residual Stress

2017 ◽  
Author(s):  
Gang Zheng ◽  
Sayeed Hossain ◽  
Feng Shen ◽  
Chris Truman
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Longitudinal Axis ◽  
Hole Drilling ◽  
Internal Diameter ◽  
Deep Hole ◽  
Element Analysis ◽  
Deep Hole Drilling ◽  
Drilling Technique ◽  
Technique Comparison

The aim of the present study was to utilize a complex residual stress generated within a welded circular disc to further investigate the standard deep-hole drilling (DHD) technique and the newly developed over-coring deep-hole drilling (oDHD) technique in accurately measuring residual stresses well over yield stress. Finite Element Analysis (FEA) was used to optimize and extend the deep-hole drilling technique and improve its accuracy. The standard DHD procedure involves 4 steps. (1) A reference hole is gun-drilled through the component. (2) The internal diameter of the reference hole is measured at different angular positions through the depth of the component. (3) A cylindrical section with the reference hole as its longitudinal axis is trepanned free from the component. (4) Finally, the relaxed internal diameter is re-measured at the same angular positions and the same depths. The drilling, trepanning procedures and the parameters of the deep-hole drilling technique were all studied in detail to optimize the technique. Comparison is made between the FEA predicted residual stress in the weld, the measurements and the reconstructed residual stresses of the measurements. The close correlations confirmed the suitability of new modifications made in the deep-hole drilling technique to account for plasticity when measuring near yield residual stresses present in a component.

Summary of Weld Residual Stress Analyses for Dissimilar Metal Weld Nozzles

2010 ◽  
Author(s):  
F. W. Brust ◽  
Tao Zhang ◽  
Do-Jun Shim ◽  
Sureshkumar Kalyanam ◽  
Gery Wilkowski ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Residual Stresses ◽  
Weld Metal ◽  
Crack Growth ◽  
Steam Generator ◽  
Deep Hole ◽  
Pressurized Water ◽  
Dissimilar Metal ◽  
Weld Residual Stress

Flaw indications have been found in some dissimilar metal nozzle to stainless steel piping welds in pressurized water reactors (PWR) throughout the world. The nozzle welds usually involve welding ferritic (often A508) nozzles to 304/316 stainless steel pipe using Alloy 182/82 weld metal. Due to an unexpected aging issue with the weld metal, the weld becomes susceptible to a form of corrosion cracking referred to as primary water stress corrosion cracking (PWSCC). It can occur if the temperature is high enough (usually >300C) and the water chemistry in the PWR is typical of operating plants. This paper represents one of a series of papers which examine the propensity for cracking in a particular operating PWR in the UK. This paper represents an examination of the weld residual stress distributions which occur in four different size nozzles in the plant. Companion papers in this conference examine crack growth and PWSCC mitigation efforts related to this plant. British Energy (BE) has developed a work program to assess the possible impact of PWSCC on dissimilar metal welds in the primary circuit of the Sizewell ‘B’ pressurized water reactor. This effort has included the design and manufacture of representative PWR safety/relief valve nozzle welds both with and without a full structural weld overlay, multiple residual stress measurements on both mock-ups using the deep hole and incremental deep hole methods, and a number of finite element weld residual stress simulations of both the mock-ups and equivalent plant welds. This work is summarized in companion papers [1–3]. Here, the detailed weld residual stress predictions for these nozzles are summarized. The weld residual stresses in a PWR spray nozzle, safety/relief nozzle, surge nozzle, and finally a steam generator hot-leg nozzle are predicted here using an axis-symmetric computational weld solution process. The residual stresses are documented and these feed into a natural crack growth analysis provided in a companion PVP 2010-25162 paper [1]. The solutions are made using several different constitutive models: kinematic hardening, isotropic hardening, and a mixed hardening model. Discussion will be provided as to the appropriateness of the constitutive model for multi-pass DM weld modeling. In addition, the effect of including or neglecting the post-weld heat treatment process, which typically occurs after the buttering process in a DM weld, is presented. During operation the DM welds in a PWR experience temperatures in excess of 300°C. The coefficient of thermal expansion (CTE) mismatch between the three materials, particularly the higher CTE in the stainless steel, affects the stresses at operating temperature. The K-weld geometry used in the steam generator nozzles in this plant combines with CTE mis-match effects to result in service stresses somewhat different from V-weld groove cases.

Application of the Modified Deep Hole Drilling Technique (iDHD) for Measuring Near Yield Non-Axisymmetric Residual Stresses

2009 ◽  
Author(s):  
Amir-Hossein Mahmoudi ◽  
David J. Smith ◽  
Chris E. Truman ◽  
Martyn J. Pavier
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Fields ◽  
Hole Drilling ◽  
Deep Hole ◽  
Axisymmetric Stress ◽  
Deep Hole Drilling ◽  
Element Simulation ◽  
Drilling Technique ◽  
Shrink Fit

The modified deep hole drilling technique (iDHD) has been developed to allow near yield residual stresses to be measured and has been validated for axisymmetric residual stress fields. In the present investigation, the application of the iDHD technique was extended to non-axisymmetric stress fields. First, a finite element simulation of the iDHD technique was carried out to demonstrate its effectiveness at measuring near yield residual stress. Experimental measurements were then carried out on shrink fit specimens to investigate the performance of the technique in practice. These shrink fit specimens were assembled in such a way that either axisymmetric or non-axisymmetric stress fields could be generated. The results indicated that the iDHD technique is capable of measuring non-axisymmetric residual stresses in presence of plasticity.

Measurement of Residual Stresses in Large Industrial Components Using the Deep Hole Drilling Technique

2005 ◽  
Author(s):  
X. Ficquet ◽  
C. E. Truman ◽  
D. J. Smith ◽  
T. B. Brown ◽  
T. A. Dauda
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Excellent Agreement ◽  
Stress Component ◽  
Hole Drilling ◽  
Deep Hole ◽  
Deep Hole Drilling ◽  
Drilling Technique ◽  
Compressive Residual Stresses

“ELIXIR – Extending Plant Life Through Improved Fabrication and Advanced Repair Methodology” was a European Union FP5 sponsored project. During the duration of the Elixir project, much work was directed at providing the necessary data for the validation of numerical modelling techniques applied to residual stress generation and hydrogen diffusion arising from the welding process. The project focussed around four industrial applications, namely petrochemical, boiler, offshore and submarine. This paper presents through-thickness residual stress measurements obtained by the University of Bristol on two of the large industrial components. The results were obtained using the deep hole drilling technique and compared to Finite Element predictions provided by other partners. The components considered are a large P275 steel set-in nozzle, typical of a boiler application and a large S690 steel set-on nozzle, typical of an offshore application. The boiler application consisted of a nozzle of diameter 600mm and thickness 50mm, on a pipe of diameter 1100mm and 100mm thickness. The offshore application was a nozzle of diameter 900mm and thickness 50mm, on a pipe of diameter 1050mm and 50mm thickness. Both the longitudinal and transverse stresses measured using deep hole drilling showed excellent agreement with Finite Element predictions through the thickness of the boiler sample. On the top surface, a zone of tensile residual stresses, over a distance of approximately 40mm, was revealed, which was equilibrated by a zone of compressive residual stresses over the final 50mm of thickness. Results for the offshore application demonstrated that at the front surface, both of the stress components were essentially zero, but both the longitudinal and transverse components rose rapidly to maxima of approximately 500MPa and 220MPa, respectively. Tensile residual stresses were supported over a distance of approximately 30mm. Over the final 20mm of thickness, compressive residual stresses existed, which again fell to approximately zero on the back face. There is excellent agreement between measurements and the Finite Element predictions for the transverse stress component, but less good agreement between measurements and predictions of the longitudinal stress component.

Simulation and Measurement of Residual Stresses in a Stainless Steel Ring Welded Circular Disc

2012 ◽  
Author(s):  
Gang Zheng ◽  
Sayeed Hossain ◽  
Mike Smith ◽  
David Smith
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Circular Disc ◽  
Hole Drilling ◽  
Deep Hole ◽  
Deep Hole Drilling ◽  
Hole Drilling Method ◽  
Drilling Method

Residual stresses were predicted and measured in a circular disc containing a partial ring weld. This study first created an axisymmetric finite element model so that the process of introducing the ring weld was simulated using thermal and mechanical modelling. The resulting residual stresses were then mapped onto a 3D model which included the necessary mesh and boundary conditions to simulate the process of residual stress measurement using the deep hole drilling method. Then an experimental programme of residual stress measurement using the deep hole drilling method and the neutron diffraction technique was conducted on the welded circular disc. The results from the deep hole drilling measurements matched well with the neutron diffraction results on the original stress field in the ring weld. While comparison between measurements and predicted residual stresses show that predicted hoop stresses are slightly higher than measured, there is in general a fair comparison between measured and predicted residual stress.

Residual Stress Measurements Using the Contour, Deep-Hole Drilling and Neutron Diffraction Methods in T-Section Specimens

2016 ◽  
Author(s):  
Karim Serasli ◽  
Douglas Cave ◽  
Ed Kingston
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Complex Geometry ◽  
Contour Method ◽  
Hole Drilling ◽  
Deep Hole ◽  
Premature Failure ◽  
Deep Hole Drilling ◽  
The Wire

The presence of high magnitude residual stresses in welded components causes material degradation, local yielding and plastic deformation. Their presence provides the potential for premature failure and compromises the integrity of a structure. This paper presents a review of work carried out to ascertain the residual stresses present within T-section specimens, made from ferritic steel, in their as-welded condition. The standard and incremental deep hole drilling (DHD and iDHD) techniques, the neutron diffraction (ND) and the contour method were applied to characterise the residual stresses in the regions in and around the two fillet welds of the specimens and the surrounding parent material within which the balancing residual stresses needed to be measured. The results of these measurements are presented and compared to highlight agreements and discrepancies in the measured residual stress distributions using these different techniques. A compendium of measurements at a similar location in various T-sections and their comparison with the BS7910 standard show that the measured longitudinal distributions are similar despite the observed scatter. Finally, this paper briefly attempts to investigate and discuss the technical challenges identified when applying the contour method to complex geometry components. The constraint of the specimen during the wire electro-discharge machining (EDM) process, the quality of the wire EDM cut made and the analysis of the raw data for the conversion into residual stresses directly affect the accuracy of the contour method results. The identification and investigation of these challenges lead to continuous improvements of the contour method procedure and reduce uncertainties of the measurement.

Characterisation of Residual Stress Levels Retained in Fracture Mechanics Specimens Machined From Non-Stress Relieved Welds

2013 ◽  
Author(s):  
Robert J. A. McCluskey ◽  
Gang Zheng ◽  
Andrew H. Sherry ◽  
David J. Smith
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Fracture Mechanics ◽  
Residual Stresses ◽  
Hole Drilling ◽  
Deep Hole ◽  
Deep Hole Drilling ◽  
Integrity Assessment ◽  
Weld Residual Stress ◽  
Stress Levels

The structural integrity assessment of weldments in engineering components, including piping, is dependent upon the acquisition of valid fracture toughness data. Test standards provide guidance for the preparation of fracture mechanics specimens machined from welds, recognising that under some circumstances retained weld residual stress in the specimens may influence the test, for example, by impairing the ability to establish a valid fatigue pre-crack. To date, however, there are little experimental data quantifying the level and distribution of retained residual stress in fracture mechanics specimens. This paper describes an experimental study characterising the residual stresses retained in single-edge notched bend specimens machined from a non stress-relieved, narrow-gap Tungsten Inert Gas welded pipe, manufactured from 304L stainless steel. The original weld residual stress field was characterised using neutron diffraction and deep hole drilling. The residual stress levels retained in the test specimens were subsequently quantified using deep hole drilling. The results indicated that reasonable levels of residual stress are retained within specimens, although for high toughness, ductile steel, this is insufficient to influence the fracture toughness measurement. The results, however, have implications for testing non stress-relieved welds manufactured from low toughness materials, where retained residual stresses could unduly influence fracture toughness measurements.

Finite Element Validation of the over-Coring Deep-Hole Drilling Technique

2011 ◽  
Vol 70 ◽  
pp. 291-296 ◽  
Author(s):  
Sayeed Hossain ◽  
Ed J. Kingston ◽  
Christopher E. Truman ◽  
David John Smith
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Residual Stress Measurement ◽  
Hole Drilling ◽  
Deep Hole ◽  
Residual Stress Field ◽  
Deep Hole Drilling

The main objective of the present study is to validate a simple over-coring deep-hole drilling (oDHD) residual stress measurement technique by utilising finite element simulations of the technique. A number of three dimensional (3D) finite element analyses (FEA) were carried out to explore the influence of material removal and the cutting sequence during the deep-hole drilling (DHD) residual stress measurement process on the initial residual stress field. Two models were considered in the study. First, the residual stress field predicted in a rapid spray water quenched solid cylinder was used as the initial stress field for the DHD FE model. The DHD reconstructed residual stresses were compared with the initial FE predicted stresses. Different cutting sequences and different dimensions were systematically simulated before arriving at an optimum solution for the oDHD technique. The oDHD technique significantly improved the spatial resolution and was applied in a second model consisting of a 40mm thick butt-welded pipe. The DHD reconstructed residual stresses compared very well with the initial FE predicted weld residual stress thereby validating the oDHD technique.

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