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.

Numerical Simulation on 3D Residual Stress Field of Both-Side Laser Shot Peened Specimen with Center-Hole

2010 ◽  
Vol 97-101 ◽  
pp. 3816-3819
Author(s):  
X.D. Yang ◽  
Jian Zhong Zhou ◽  
Shu Huang ◽  
Ling Ling Hu ◽  
Cheng Dong Wang
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Residual Stress ◽  
Stress Field ◽  
Laser Shot ◽  
Bottom Surface ◽  
Stress Distributions ◽  
Residual Stress Field ◽  
Typical Experiment ◽  
Compressive Residual Stresses

A numerical analytical model for both-side laser shot peening (LSP) of specimen with center-hole was established, the influence of the center-hole on peening effect was investigated, and the 3D residual stress distributions of ZK60 specimen after one-side and both-side LSP were analyzed. The results showed that compressive residual stresses were obtained at the both sides of specimen after both-side LSP, with a stress value of -179.41MPa on the bottom surface, much larger than that of one-side LSP. The typical experiment of LSP for ZK60 specimen was carried out and the experimental data were well correlated with the simulated results.

scholarly journals Evaluation of the Impact of Residual Stresses in Crack Initiation with the Application of the Crack Compliance Method Part I, Numerical Analysis

2010 ◽  
Vol 24-25 ◽  
pp. 253-259 ◽  
Author(s):  
G. Urriolagoitia-Sosa ◽  
B. Romero-Ángeles ◽  
Luis Héctor Hernández-Gómez ◽  
G. Urriolagoitia-Calderón ◽  
Juan Alfonso Beltrán-Fernández ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Numerical Analysis ◽  
Stress Field ◽  
Crack Initiation ◽  
Residual Stresses ◽  
Main Concern ◽  
Residual Stress Field ◽  
Set Up ◽  
The Impact

The understanding of how materials fail is still today a fundamental research problem for scientist and engineers. The main concern is the assessment of the necessary conditions to propagate a crack that will eventually lead to failure. Nevertheless, this kind of analysis tends to be more complicated, when a prior history in the material is taken into consideration and it will be extremely important to recognize all the factors involved in this process. In this work, a numerical simulation of the introduction of residual stresses, which change the crack initiation conditions, in a modified compact tensile specimen to change the condition of crack initiation is presented. Four numerical analyses were carried out; an initial evaluation was performed in a specimen without a crack and it was used for the estimation of a residual stress field produced by an overload; three more cases were simulated and a crack was introduced in each specimen (1 mm, 5 mm and 10 mm, respectively). The overload was then applied to set up a residual stress field into the component; furthermore, in each case the crack compliance method (CCM) was applied to measure the induced residual stress field. By performing this numerical simulation, the accuracy of the crack compliance method can be evaluated. On the other hand, elastic-plastic finite element analysis was utilized for the residual stress estimation. The numerical analysis was based on the mechanical properties of a biocompatible material (AISI 316L). The obtained results provided significant data about diverse factors, like; the manner in which a residual stress field could modify the crack initiation conditions, the convenient set up for induction of a beneficial residual stresses field, as well as useful information that can be applied for the experimental implementation of this research.

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..

scholarly journals An inverse approach for constructing the residual stress field induced by welding

2002 ◽  
Vol 37 (4) ◽  
pp. 345-359 ◽  
Author(s):  
Y P Cao ◽  
N Hu ◽  
J Lu ◽  
H Fukunaga ◽  
Z. H Yao
Keyword(s):  
Experimental Data ◽  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Strain Field ◽  
Basis Functions ◽  
Residual Stress Field ◽  
Inverse Approach ◽  
Inherent Strain ◽  
Inherent Strain Method

In this paper, an inverse approach based on the inherent strain method has been proposed for constructing the residual stress field induced by welding. Firstly, some smooth basis functions in the form of polynomials have been employed to approximate inherent strains. To select the basis functions properly, previous valuable knowledge about distributions of residual stresses for some typical welding structures should be considered. Furthermore, singular modes in the assumed inherent strain that do not cause residual stresses should be excluded. In this way, a stable profile of the inherent strain field can be assumed. Secondly, by employing the finite element method (FEM) and the least-squares technique, the inherent strain field can be identified from the experimental data at some key points. The proper selection of positions of experimental points has also been considered. Finally, the distribution of residual stresses can be constructed efficiently by using the obtained inherent strain field. Compared with the traditional inherent strain method, in the present work the sensitivity matrix for predicting inherent strains can be evaluated more effectively and experimental data needed in the identification procedure can be reduced significantly. Some typical examples have been presented to demonstrate the effectiveness of the present method.

Influence of Material Model on Tensile Loaded Joint

2010 ◽  
Vol 165 ◽  
pp. 394-399 ◽  
Author(s):  
E. Szymczyk ◽  
Grzegorz Slawinski
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Numerical Analysis ◽  
Stress Field ◽  
Material Model ◽  
Finite Element Simulations ◽  
Residual Stress Field ◽  
Material Models ◽  
Riveted Joint ◽  
Load Conditions

The paper deals with the numerical analysis of a tensile loaded riveted joint. Finite element simulations of the upsetting process were carried out with the use of Marc code to determine the residual stress field. The contact with friction is defined between the mating parts of the joint. The computations were performed for four cases of material and load conditions and a comparison was performed on the basis of results obtained for standard elasto plastic and Gurson material models. Moreover, the influence of material model and residual stress on the tensile loaded joint was analyzed.

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.

scholarly journals Numerical Analysis of Longitudinal Residual Stresses and Deflections in a T-joint Welded Structure Using a Local Preheating Technique

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3487 ◽  
Author(s):  
Mato Perić ◽  
Ivica Garašić ◽  
Sandro Nižetić ◽  
Hrvoje Dedić-Jandrek
Keyword(s):  
Residual Stress ◽  
Numerical Analysis ◽  
Stress Field ◽  
Numerical Models ◽  
Preheat Temperature ◽  
Residual Stress Field ◽  
Residual Stress State ◽  
Welded Structure ◽  
Longitudinal Residual Stress ◽  
Interpass Time

In this paper a numerical analysis of a T-joint fillet weld is performed to investigate the influences of different preheat temperatures and the interpass time on the longitudinal residual stress fields and structure deflections. In the frame of the numerical investigations, two thermo-mechanical finite element models, denoted M2 and M3, were analyzed and the results obtained were then compared with the model M1, where the preheating technique was not applied. It is concluded that by applying the preheat temperature prior to the start of welding the post-welding deformations of welded structures can be significantly reduced. The increase of the preheat temperature increased the longitudinal residual stress field at the ends of the plates. The influence of the interpass time between two weld passes on the longitudinal residual stress state and plate deflection was investigated on two preheated numerical models, M4 and M5, with an interpass time of 60 s and 120 s, respectively. The results obtained were then compared with the preheated model M3, where there was no time gap between the two weld passes. It can be concluded that with the increase of interpass time, the plate deflections significantly increase, while the influence of the interpass time on the longitudinal residual stress field can be neglected.

Characterising Residual Stresses in Rectangular Beam Specimens Following Thermo-Mechanical Loading

2006 ◽  
Author(s):  
Ali Mirzaee-Sisan ◽  
Christopher E. Truman ◽  
David J. Smith
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
Stress Field ◽  
Residual Stresses ◽  
Mechanical Loading ◽  
Ferritic Steel ◽  
Thermal Stresses ◽  
Residual Stress Field ◽  
Rectangular Beam

The neutron diffraction (ND) technique was used to characterise residual stress fields in thin rectangular beam specimens containing residual stresses induced thermo-mechanically by partial quenching. Two types of material were considered, type 316H stainless steel and A533B ferritic steel. The work was motivated by a need to investigate the influence of residual stress on the fracture behaviour of steels. During quenching, specimens experienced a severe temperature gradient which induced thermal stresses resulting in plastic strains and a subsequent residual stress field. An extensive finite element (FE) analysis was undertaken to predict the residual stress following thermo-mechanical loading. It was shown that partial quenching generated a considerable residual stress field in 316H stainless steel. However, the level of residual stresses in the A533B steel specimens was lower than that 316H stainless steel specimens. There was acceptable agreement between the finite element simulations and measurements with simulations generally predicting higher tensile residual stresses following partial quenching than those measured in the 316H stainless steel, and lower tensile residual stresses than those measured in the A533B ferritic steel.

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