Residual Stress Analysis of Laser Welded Aluminium T-Joints Using Neutron Diffraction

2006 ◽  
Vol 524-525 ◽  
pp. 419-424 ◽  
Author(s):  
Funda S. Bayraktar ◽  
Peter Staron ◽  
Mustafa Koçak ◽  
Andreas Schreyer
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Short Distance ◽  
Weld Seam ◽  
Base Plate ◽  
Laser Source ◽  
T Joints ◽  
Weld Residual Stress ◽  
Risk Areas

In this study the distribution and magnitude of residual stresses in a T-joint of aerospace grade aluminium alloy weldment was determined using neutron diffraction. A 2 mm thick AA 6013 sheet (as clip) was laser beam welded to a 6 mm thick AA 6056 base plate (as skin) to resemble the “short distance” welded clip-skin joints of an airframe. The total length of the weld was 120 mm and it was welded using 3.3 kW Nd:YAG laser source and 12% Si containing wire from one side only. No post weld heat treatment was applied after the welding. Start (run-in) and end (run-out) locations of the T-joints are generally considered as high risk areas with respect to solidification cracking and crack initiations under external loadings. It is of interest to investigate the weld residual stress fields at these locations to develop optimum joint design. Therefore, strain measurements have been performed not only in the middle of the weld seam but also at the run-in and run-out locations of these short distance welds. Higher longitudinal tensile residual stresses are detected at the run-out locations than the run-in locations. The measurements in the clip showed that the clip has a longitudinal tensile stress peak away (about 8 mm) from the weld seam.

Influence of the Welding Sequence on Residual Stresses in Laser Welded T-Joints of an Airframe Aluminium Alloy

2008 ◽  
Vol 571-572 ◽  
pp. 375-380 ◽  
Author(s):  
Winulf Machold ◽  
Peter Staron ◽  
Funda S. Bayraktar ◽  
Stefan Riekehr ◽  
Mustafa Koçak ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Welding Process ◽  
Base Plate ◽  
Stress Fields ◽  
Stress Concentrations ◽  
T Joints ◽  
Element Simulation ◽  
Welding Sequence ◽  
Welding Sequences

The effect of different welding sequences between a 4.5 mm thick AA 6156 T6 base plate and a 2 mm thick AA 6013 T6 clip – resembling a skin-clip joint of an airframe – using a 3.3 kW Nd:YAG laser is investigated. Under cyclic loading the breakdown of such T-joints happens at one end of the clip, which is due to local residual stress concentrations. Recent measurements indicated that tensile stresses could be lower at the run-in than at the run-out locations. For a deeper investigation of this effect sheets with different welding sequences were produced. One welding sequence was made with two starting points in the centre, and a second with starting points at the clip ends. Temperature measurements were made using thermocouples to verify the heat conditions for a finite element simulation of the welding process, which is used for predictions of the residual stress distribution. Actual values of the residual stress fields were determined by neutron diffraction. The influences of the welding sequence on the measured temperatures and the residual stresses are discussed.

Analysis of Residual Stress in Laser Welded Aerospace Aluminium T-Joints by Neutron Diffraction and Finite Element Modelling

2008 ◽  
Vol 571-572 ◽  
pp. 355-360 ◽  
Author(s):  
Funda S. Bayraktar ◽  
Peter Staron ◽  
Mustafa Koçak ◽  
Andreas Schreyer
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Fe Simulation ◽  
Base Plate ◽  
Experimental Results ◽  
Finite Element Software ◽  
Two Samples ◽  
First Results

The residual stress distribution in three laser welded T-joint configurations of aerospace aluminium alloys were measured using neutron diffraction and FE-simulation was conducted to compare with the experimental results. A 2 mm thick AA 6013 T6 sheet (as clip) was welded to a 4.5 mm thick and 400 mm wide AA 6156 T4 base plate (as skin of the airframe). In two samples, the thickness of the plate was reduced in some areas after welding to produce so-called “pockets” with the purpose of the weight reduction to resemble the fabrication practise in aircraft industry. The effect of pocketing process, which produced two different geometries around the clip weld on the residual stress evolution was analysed. In the plain sample (without pockets), residual stresses were predicted using the SYSWELD finite element software. The strain measurements on the base plate were performed at three locations; namely, the middle of the weld length (mid-clip), welding start (run-in) and end (run-out) locations. In all welded plates, slightly higher longitudinal tensile residual stresses were detected at the midclip locations, whereas transverse residual stresses were similar for all locations. In the run-out location, higher longitudinal tensile residual stresses were present than in the run-in location, which was the case in our previous results on other samples. The first results of the SYSWELD FE-simulation of the plain sample were compared with experimental results. The comparison has shown particularly good agreement for the transverse stresses. Although the simulation yields higher longitudinal tensile stresses than the experimental results, the stress distributions were very similar.

scholarly journals Residual Stress Measurements in Mo/CuCrZr Tiles Using Neutron Diffraction

2008 ◽  
Vol 59 ◽  
pp. 299-303
Author(s):  
K. Mergia ◽  
Marco Grattarola ◽  
S. Messoloras ◽  
Carlo Gualco ◽  
Michael Hofmann
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Heat Sink ◽  
High Yield ◽  
Fusion Reactors ◽  
Plasma Facing Components ◽  
Induced Stresses ◽  
Compliant Layer

In plasma facing components (PFC) for nuclear fusion reactors tungsten or carbon based tiles need to be cooled through a heat sink. The joint between the PFC and the heat sink can be realized using a brazing process through the employment of compliant layer of either a low yield material, like copper, or a high yield material, like molybdenum. Experimental verification of the induced stresses during the brazing process is of vital importance. Strains and residual stresses have been measured in Mo/CuCrZr brazed tiles using neutron diffraction. The strains and stresses were measured in Mo tile along the weld direction and at different distances from it. The experimental results are compared with Finite Element Simulations.

Residual stresses in Al2O3/Y-TZP Ceramic Laminates Fabricated by Tape and Slip Casting

2008 ◽  
Vol 571-572 ◽  
pp. 327-332 ◽  
Author(s):  
Jesus Ruiz-Hervias ◽  
Giovanni Bruno ◽  
Jonas Gurauskis ◽  
A.J. Sanchez-Herencia ◽  
C. Baudin
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Volume Fraction ◽  
Tape Casting ◽  
Slip Casting ◽  
Ceramic Composites ◽  
Processing Route ◽  
Alumina Matrix ◽  
Stress Profiles

Residual stress profiles were measured by neutron diffraction in Al2O3/Y-TZP ceramic composites containing 5 and 40 vol.% Y-TZP fabricated by conventional slip casting and by a novel tape casting route. Residual stresses in the zirconia are tensile and increase as its volume fraction decreases. For the alumina matrix, residual stress is compressive and increases with the zirconia volume fraction. In the composite with 5 vol.% zirconia, the processing route does not have an influence on residual stresses. However, in the composite with 40 vol.% zirconia, residual stresses are different in the samples obtained by both processing routes.

Weld Residual Stress in Large Diameter Nuclear Nozzles

2011 ◽  
Author(s):  
Tao Zhang ◽  
F. W. Brust ◽  
Gery Wilkowski
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Nuclear Power ◽  
Kinematic Hardening ◽  
Large Diameter ◽  
Thick Wall ◽  
Isotropic Hardening ◽  
Residual Stress Field ◽  
Mixed Hardening ◽  
Weld Residual Stress

Weld residual stresses in nuclear power plant can lead to cracking concerns caused by stress corrosion. These are large diameter thick wall pipe and nozzles. Many factors can lead to the development of the weld residual stresses and the distributions of the stress through the wall thickness can vary markedly. Hence, understanding the residual stress distribution is important to evaluate the reliability of pipe and nozzle joints with welds. This paper represents an examination of the weld residual stress distributions which occur in various different size nozzles. The detailed weld residual stress predictions for these nozzles are summarized. Many such weld residual stress solutions have been developed by the authors in the last five years. These distributions will be categorized and organized in this paper and general trends for the causes of the distributions will be established. The residual stress field can therefore feed into a crack growth analysis. The solutions are made using several different constitutive models such as kinematic hardening, isotropic hardening, and mixed hardening model. Necessary fabrication procedures such as repair, overlay and post weld heat treatment are also considered. Some general discussions and comments will conclude the paper.

On the Mechanics of Residual Stresses in Girth Welds

2006 ◽  
Vol 129 (3) ◽  
pp. 345-354 ◽  
Author(s):  
P. Dong
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Relative Importance ◽  
Stress Distributions ◽  
Unified Framework ◽  
Joint Geometry ◽  
Weld Residual Stress ◽  
Girth Welds ◽  
Welding Procedure

In this paper, some of the important controlling parameters governing weld residual stress distributions are presented for girth welds in pipe and vessel components, based on a large number of residual stress solutions available to date. The focus is placed upon the understanding of some of the overall characteristics in through-wall residual stress distributions and their generalization for vessel and pipe girth welds. In doing so, a unified framework for prescribing residual stress distributions is outlined for fitness-for-service assessment of vessel and pipe girth welds. The effects of various joint geometry and welding procedure parameters on through thickness residual stress distributions are also demonstrated in the order of their relative importance.

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.

scholarly journals Residual Stresses Distribution Posterior to Welding and Cutting Processes

2021 ◽  
Author(s):  
Asma Manai
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Weld Seam ◽  
Considerable Change ◽  
Cutting Process ◽  
Local Material ◽  
Weld Residual Stress ◽  
Exact Size ◽  
Cutting Processes ◽  
Welding Processes

Welding is a joining process that leads to considerable change in the local material and the formation of welding residual stresses (RS). Welding residual stresses can be compressive (beneficial for the fatigue life) or tensile (harmful for the fatigue life). In this chapter, a probabilistic analysis of residual stresses distribution posterior to welding processes is carried out. Several researchers stated that the type of the introduced stresses either compressive or tensile depends on several factors. Some of these factors are listed in this chapter. Welding of mega-structures is carried out in the workshops, then a cutting process takes place to construct the exact size of the structural components. This cutting process has a significant effect on the weld residual stresses re-distribution. A study of the re-distribution of the weld residual stress after cutting was performed. It was found that independent of the weld seam length, the residual stresses re-distributed up to 60 % of the weld seam length.

Residual Stresses in Steel and Zirconium Weldments

1997 ◽  
Vol 119 (2) ◽  
pp. 137-141 ◽  
Author(s):  
J. H. Root ◽  
C. E. Coleman ◽  
J. W. Bowden ◽  
M. Hayashi
Keyword(s):  
Residual Stress ◽  
Electron Beam ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Prolonged Exposure ◽  
Electron Beam Welding ◽  
Three Dimensional ◽  
Diffraction Method ◽  
Outer Diameter ◽  
Stress Relieving

Three-dimensional scans of residual stress within intact weldments provide insight into the consequences of various welding techniques and stress-relieving procedures. The neutron diffraction method for nondestructive evaluation of residual stresses has been applied to a circumferential weld in a ferritic steel pipe of outer diameter 114 mm and thickness 8.6 mm. The maximum tensile stresses, 250 MPa in the hoop direction, are found at mid-thickness of the fusion zone. The residual stresses approach zero within 20 mm from the weld center. The residual stresses caused by welding zirconium alloy components are partially to blame for failures due to delayed hydride cracking. Neutron diffraction measurements in a GTA-welded Zr-2.5Nb plate have shown that heat treatment at 530°C for 1 h reduces the longitudinal residual strain by 60 percent. Neutron diffraction has also been used to scan the residual stresses near circumferential electron beam welds in irradiated and unirradiated Zr-2.5Nb pressure tubes. The residual stresses due to electron beam welding appear to be lower than 130 MPa, even in the as-welded state. No significant changes occur in the residual stress pattern of the electron-beam welded tube, during a prolonged exposure to thermal neutrons and the temperatures typical of an operating nuclear reactor.

Weld Residual Stress and Fracture Behavior of NASA Layered Pressure Vessels

2019 ◽  
Author(s):  
F. W. Brust ◽  
R. H. Dodds ◽  
J. Hobbs ◽  
B. Stoltz ◽  
D. Wells
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Fracture Behavior ◽  
Service Evaluation ◽  
Pressure Vessels ◽  
Weld Residual Stress ◽  
Proof Testing ◽  
Fracture Assessment ◽  
High Level ◽  
Initial Results

Abstract NASA has hundreds of non-code layered pressure vessel (LPV) tanks that hold various gases at pressure. Many of the NASA tanks were fabricated in the 1950s and 1960s and are still in use. An agency wide effort is in progress to assess the fitness for continued service of these vessels. Layered tanks typically consist of an inner liner/shell (often about 12.5 mm thick) with different layers of thinner shells surrounding the inner liner each with thickness of about 6.25-mm. The layers serve as crack arrestors for crack growth through the thickness. The number of thinner layers required depends on the thickness required for the complete vessel with most tanks having between 4 and 20 layers. Cylindrical layers are welded longitudinally with staggering so that the weld heat affected zones do not overlap. The built-up shells are then circumferentially welded together or welded to a header to complete the tank construction. This paper presents some initial results which consider weld residual stress and fracture assessment of some layered pressure vessels and is a small part of the much larger fitness for service evaluation of these tanks. This effort considers the effect of weld residual stresses on fracture for an inner layer longitudinal weld. All fabrication steps are modeled, and the high-level proof testing of the vessels has an important effect on the final WRS state. Finally, cracks are introduced, and service loading applied to determine the effects of WRS on fracture.

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