An evaluation of residual stress distribution in welded compact tension specimens using neutron diffraction

2005 ◽  
Vol 40 (2) ◽  
pp. 211-216 ◽  
Author(s):  
G. O Rading
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Neutron Diffraction ◽  
Stress Field ◽  
Fatigue Cracks ◽  
Compact Tension ◽  
Maximum Tensile Stress ◽  
Thickness Variation ◽  
Residual Stress Field ◽  
Neutron Diffraction Technique

The neutron diffraction technique was used to determine the residual stress field in welded compact tension specimens of the aluminium-lithium alloy AA 2095. The deep penetrating characteristic of neutrons was exploited to evaluate the through-thickness variation in residual stress. Moreover, insight into the redistribution of these stresses was gained by extending a fatigue crack through the residual stress field and re-examining the stress distribution. The specimen without a crack was found to have a high compressive stress (of the order of - 135MPa) ahead of the notch. This rose to a maximum tensile stress of about 50MPa, 22 mm from the notch, followed by a drop to negative values further ahead of the notch. It was observed that the magnitude of the stresses changed on moving into the thickness of the specimen. However, the form of the graph showing stress versus distance ahead of the notch remained unchanged. When fatigue cracks of different lengths were introduced, the magnitude of the stress close to the tip first increased with crack length, before decreasing and then rising again. Nevertheless, the form of the graph remained unchanged and the stress at the crack tip remained compressive. The paper concludes that any study of the response of a component to mechanical loading involving a residual stress field must take these factors (i.e. through-thickness stress variation and stress redistribution) into consideration.

Neutron Diffraction Studies of Residual Stresses Around Gouges and Gouged Dents

2012 ◽  
Author(s):  
Lynann Clapham ◽  
Vijay Babbar ◽  
Thomas Gnaeupel-Herold ◽  
Remi Batisse ◽  
Mures Zarea
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Neutron Diffraction ◽  
Stress Field ◽  
Residual Stresses ◽  
Wall Stress ◽  
Outer Wall ◽  
Stress Distributions ◽  
Wall Surface ◽  
Residual Stress Field

The residual stress pattern surrounding gouges is complex and, to date, has not been accurately modeled using stress modeling software. Thus measurement of these stress distributions is necessary. Neutron diffraction is the only experimental method with the capability of directly evaluating residual strain throughout the entire thickness of a pipe wall, in and around dent or gouged regions. Neutron diffraction measurements were conducted at the NIST reactor on three gouged dents in X52 pipeline sections. These were part of a larger sample set examined as part of the comprehensive MD4-1 PRCI/DOT PHMSA project. Gouges contained in pipeline sections were termed BEA161 (primarily a gouge with little denting), and BEA178 (mild gouging, very large dent). Measurements were also conducted on a coupon sample – P22, that was created as part of an earlier study. For the moderate gouges with little or no associated denting (BEA161 and P22) the residual stress field was highly localized around the immediate gouge vicinity (except where there was some denting present). The through wall stress distributions were similar at most locations — characterized by neutral or moderate hoop and axial stresses (50–100MPa) at the outer wall surface (i.e. at the gouge itself) gradually becoming highly compressive (up to −600MPa) at the inner wall surface. The other sample (BEA178) exhibited a very mild gouge with significant denting, and the results were very different. The denting process associated with this kind of gouge+dent dominated the residual stresses, making the residual stress distribution very complex. In addition, rather than having a residual stress field that is localized in the immediate gouge vicinity, the varying stress distribution extends to the edge of the dented region..

ENPOWER: Investigations by Neutron Diffraction and Finite Element Analyses on Residual Stress Formation in Repair Welds Applied to Ferritic Steel Plates

2005 ◽  
Author(s):  
Carsten Ohms ◽  
Robert C. Wimpory ◽  
Dimitar Neov ◽  
Didier Lawrjaniec ◽  
Anastasius G. Youtsos
Keyword(s):  
Experimental Data ◽  
Residual Stress ◽  
Numerical Analysis ◽  
Neutron Diffraction ◽  
Stress Field ◽  
Ferritic Steel ◽  
Maximum Stress ◽  
Steel Plates ◽  
Residual Stress Field ◽  
Welding Procedure

The European collaborative research project ENPOWER (Management of Nuclear Plant Operation by Optimizing Weld Repairs) has as one of its main objectives the development of guidelines for the application of repair welds to safety critical components in nuclear power plants. In this context letter box repair welds applied to thin ferritic steel plates to simulate repair of postulated shallow cracks have been manufactured for the purpose of experimental and numerical analysis of welding residual stresses. Two specimens have been procured, one of them prepared in accordance with a standard welding procedure, while in the second case a different procedure was followed in order to obtain extended martensite formation in the heat affected zone. Residual stresses have been determined in both specimens by neutron diffraction at the High Flux Reactor of the Joint Research Centre in Petten, The Netherlands. In parallel Institut de Soudure in France has performed a full 3-d analysis of the residual stress field for the standard welding case taking into account the materials and phase transformations. The experimental data obtained for both specimens clearly suggest that the non-conventional welding procedure rendered higher maximum stress values. In the case of the standard welding procedure numerical and experimental data show a reasonable qualitative agreement. The maximum stress value was in both cases found in the same region of the material — in the base metal just underneath the weld pool — and in both cases found to be of similar magnitude (∼800 MPa found in neutron diffraction and ∼700 MPa found in numerical analysis). In this paper the experimental and numerical approaches are outlined and the obtained results are presented. In addition an outlook is given to future work to be performed on this part of the ENPOWER project. A main issue pending is the application of an optimized advanced post weld heat treatment in one of the two cases and the subsequent numerical and experimental determination of its impact on the residual stress field. At the same time further evaluation of the materials transformations due to welding is pursued.

Effect of Grit-Blasting on Residual Stress Field

2014 ◽  
Vol 606 ◽  
pp. 91-94
Author(s):  
Ondřej Kovářík ◽  
Petr Haušild ◽  
Zdenek Pala ◽  
Pavel Sachr ◽  
Vadim Davydov
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Stress Field ◽  
Mild Steel ◽  
Sample Surface ◽  
Electron Back Scatter Diffraction ◽  
Residual Stress Field ◽  
Grit Blasting ◽  
Maximum Value ◽  
Cold Rolled

The effect of grit-blasting on the development of residual stress field during the surface treatment of the cold rolled mild steel was characterized by means of neutron diffraction, nanohardness measurement and electron back-scatter diffraction. The neutron diffraction revealed strong residual compressive stress with the maximum value (about-100 MPa) situated just under the sample surface of the grit-blasted sample. The deformation profiles obtained by the nanoindentation and electron back-scatter diffraction (band slope signal) revealed the strain hardening after grit blasting up to depth of approximately 100 μm.

Abrasive Waterjet Peening With Elastic Prestress: Subsurface Residual Stress Distribution

2007 ◽  
Author(s):  
Balaji Sadasivam ◽  
Alpay Hizal ◽  
Dwayne Arola
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Stress Field ◽  
Yield Strength ◽  
Residual Stresses ◽  
Residual Stress Distribution ◽  
Abrasive Waterjet ◽  
Residual Stress Field ◽  
Surface Residual Stress ◽  
Compressive Residual Stresses

Recent advances in abrasive waterjet (AWJ) technology have resulted in new processes for surface treatment that are capable of introducing compressive residual stresses with simultaneous changes in the surface texture. While the surface residual stress resulting from AWJ peening has been examined, the subsurface residual stress field resulting from this process has not been evaluated. In the present investigation, the subsurface residual stress distribution resulting from AWJ peening of Ti6Al4V and ASTM A228 steel were studied. Treatments were conducted with the targets subjected to an elastic prestress ranging from 0 to 75% of the substrate yield strength. The surface residual stress ranged from 680 to 1487 MPa for Ti6Al4V and 720 to 1554 MPa for ASTM A228 steel; the depth ranged from 265 to 370 μm for Ti6Al4V and 550 to 680 μm for ASTM A228 steel. Results showed that elastic prestress may be used to increase the surface residual stress in AWJ peened components by up to 100%.

An Energy-Based Residual Stress Field Reconstruction Approach Using Limited Measurements

2015 ◽  
Author(s):  
H.-B. Liu ◽  
Y.-P. Li ◽  
Y.-Q. Wang ◽  
X.-J. Sheng
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Stress Field ◽  
Structural Integrity ◽  
Spline Interpolation ◽  
Residual Stress Field ◽  
Strain Compatibility ◽  
Integrity Assessment ◽  
Field Reconstruction ◽  
Initial Stress Field

To characterize the residual stress distribution is very crucial for workpiece fatigue lifetime and structural integrity assessment. An energy-based residual stress field reconstruction approach using limited measurements is proposed. Firstly, the Ferguson spline interpolation technique is employed as the stress interpolation base of the 2-order stress tensor. Then, an initial stress field can be reconstructed using the overall boundary conditions by minimizing strain energy. Further, the stress distribution is modified according to strain compatibility equation. At last, a typical stress unit from the artificial stress field constructed by FEM, was picked up as an input set to verify the validation of the developed model and algorithm numerically. It was demonstrated that the energy-based scheme was efficient and reliable to reconstruct the residual stress field from limited measurements.

Study of Creep Relaxation Behaviour of 316H Austenitic Steels Under Mechanically Induced Residual Stress

2011 ◽  
Author(s):  
Hamed Yazdani Nezhad ◽  
Noel P. O’Dowd ◽  
Catrin M. Davies ◽  
Kamran M. Nikbin ◽  
Robert C. Wimpory
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Compact Tension ◽  
Load Level ◽  
Austenitic Steels ◽  
Combined Loading ◽  
Relaxation Behaviour ◽  
Residual Stress Field ◽  
Stress Profiles ◽  
Significant Distance

Compact tension 316H austenitic steel specimens, extracted from an as-received ex-service pressure vessel header, have been pre-compressed to different load levels in order to introduce a residual stress field. Finite element (FE) analysis has been performed to predict the load level required to obtain a high magnitude tensile stress field over a significant distance ahead of the notch while preventing a large plastic zone in the specimen. The predicted residual stress profiles along the crack path are compared with those measured using neutron diffraction (ND). Comparisons have also been provided between the ND results of this work with recent work carried out on 316H and 347 stainless steels under different loading levels. The creep relaxation behaviour of the steel has been studied numerically. A proposed method to estimate the steady state creep crack tip parameter, C*, has been examined using the obtained displacement rates for the case of combined loading. Creep relaxation data for combined stresses are compared with the earlier studies.

Effect of Residual Stress Field in Front of the Slant Precrack Tip on Bent Fatigue Crack Propagation

2007 ◽  
Vol 353-358 ◽  
pp. 1207-1210 ◽  
Author(s):  
Kenichi Shimizu ◽  
Tashiyuki Torii ◽  
J. Nyuya ◽  
Y. Ma
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Stress Field ◽  
Mixed Mode ◽  
Compressive Residual Stress ◽  
Fatigue Cracks ◽  
Crack Opening ◽  
Residual Stress Field ◽  
Method Analysis ◽  
Crack Sliding Displacement

Fatigue crack bending and propagation behaviors were studied under mixed-mode conditions using annealed and fatigue slant precracks. The bent fatigue crack initiated from the fatigue slant precrack propagated under mixed-mode conditions with mode II stress intensity factor evaluated from the crack sliding displacement measured along the crack. On the other hand, bent fatigue cracks propagated under the mode I condition for an annealed slant precrack specimen. The forces which suppress the crack opening/sliding were calculated along the slant precrack and the bent crack by FEM (Finite Element Method) analysis. As a result, the crack opening suppress forces were generated by the compressive residual stress around the fatigue slant precrack, while the forces which promote the crack sliding were caused by the residual stress field in front of the fatigue slant precrack.

Measurement of the residual stress field in MIG-welded Al-2024 and Al-7150 aluminium alloy compact tension specimens

2006 ◽  
Vol 437 (1) ◽  
pp. 46-53 ◽  
Author(s):  
S. Pratihar ◽  
V. Stelmukh ◽  
M.T. Hutchings ◽  
M.E. Fitzpatrick ◽  
U. Stuhr ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Aluminium Alloy ◽  
Compact Tension ◽  
Residual Stress Field ◽  
Al 2024

Modelling Fatigue Crack Growth in a Residual Stress Field

2006 ◽  
Author(s):  
A. J. Price ◽  
P. Tsakiropoulos ◽  
M. R. Wenman ◽  
P. R. Chard-Tuckey
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Fatigue Crack ◽  
Stress Distribution ◽  
Stress Field ◽  
Crack Growth ◽  
Nuclear Reactor ◽  
Element Model ◽  
Residual Stress Distribution ◽  
Residual Stress Field

Tensile residual stresses can have a detrimental affect on the safe operating limits of components. In most cases, these residual stress fields can be relieved through various treatments but in many cases it is not realistic to expect the complete elimination of these stresses. When considering the Reactor Pressure Vessel (RPV) located within a Nuclear Reactor Plant (NRP), knowledge of fatigue and fracture within a residual stress field is essential in support of safety cases. This research has investigated the behaviour of flaws that lie within a residual stress field with emphasis on fracture toughness through a series of fracture toughness tests. Alongside this experimental series, a finite element model has been created to predict the stress distributions prior to fracture. To enable an accurate simulation of the residual stress field distribution before loading to fracture it is important that the introduction of a fatigue crack is accurately modelled. This paper details several methods of introducing a fatigue crack into a simulation. During this research it has been shown that the introduction of a crack in progressive stages will lead to a better representation of the residual stress distribution prior to fracture. It has been shown that it is essential to use experimentally determined crack front shapes for the final stage of crack growth as this shape can significantly alter the residual stress distribution.

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