Geometry Effects when Controlling Residual Stresses in Friction Stir Welds by Mechanical Tensioning

2006 ◽  
Vol 524-525 ◽  
pp. 71-76 ◽  
Author(s):  
David G. Richards ◽  
Philip B. Prangnell ◽  
Philip J. Withers ◽  
Stewart W. Williams ◽  
Andrew Wescott ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Heat Input ◽  
Finite Element Modelling ◽  
Room Temperature ◽  
Welding Parameters ◽  
Fe Model ◽  
Element Modelling ◽  
Friction Stir ◽  
Low Sensitivity ◽  
Compressive Residual Stresses

Finite element modelling has proved to be an effective tool for the investigation of trends effected by changing welding conditions. This is especially important in mechanical tensioning of friction stir welds because of the large number of parameters involved. In this paper, an FE model is used to examine the effectiveness of the mechanical tensioning technique for controlling residual stresses in FSWs by the investigation of trends caused by changes to the welding parameters. Comparisons between different geometries, traverse speeds, and welding off-axis angle all produced consistent results, and showed that the peak stresses are most strongly influenced by both the local tensioning and heat input, and not by the more global welding conditions. The results also showed a progressive decrease in the residual stresses for increasing tensioning levels and, although affected by the heat input, a relatively low sensitivity to the welding variables. At tensioning levels greater than ~50% of the room temperature yield stress, tensile stresses were replaced by compressive residual stresses within the weld.

scholarly journals FE Modelling of Mechanical Tensioning for Controlling Residual Stresses in Friction Stir Welds

2007 ◽  
Vol 539-543 ◽  
pp. 4025-4030 ◽  
Author(s):  
David G. Richards ◽  
Philip B. Prangnell ◽  
Philip J. Withers ◽  
Stewart W. Williams ◽  
Andrew Wescott ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Heat Input ◽  
High Strength ◽  
Fusion Welding ◽  
Fe Model ◽  
Fe Modelling ◽  
Friction Stir ◽  
Low Sensitivity ◽  
Plate Geometry ◽  
Detrimental Impact

Although Friction Stir Welding (FSW) avoids many of the problems encountered when fusion welding high strength Al-alloys, it can still result in substantial residual stresses that have a detrimental impact on service life. An FE model has been developed to investigate the effectives of the mechanical tensioning technique for controlling residual stresses in FSWs. The model purely considered the heat input and the mechanical effects of the tool were ignored. Variables, such as tensioning level, heat input, and plate geometry, have been studied. Good general agreement was found between modelling results and residual stress measurements, justifying the assumption that the stress development is dominated by the thermal field. The results showed a progressive decrease in the residual stresses for increasing tensioning levels and, although affected by the heat input, a relatively low sensitivity to the welding variables. At tensioning levels greater than ~ 50% of the room temperature yield stress, tensile were replaced by compressive residual stresses within the weld.

scholarly journals Prediction and Measurements of Thermal Residual Stresses in AA2024-T3 Friction Stir Welds as a Function of Welding Parameters

2010 ◽  
Vol 638-642 ◽  
pp. 1215-1220 ◽  
Author(s):  
Laurent Dubourg ◽  
P. Doran ◽  
Michael A. Gharghouri ◽  
Simon Larose ◽  
Mohammad Jahazi
Keyword(s):  
Residual Stresses ◽  
Welding Parameters ◽  
Fe Model ◽  
Influence Of Process Parameters ◽  
High Rotational Speed ◽  
Friction Stir ◽  
Thin Walled Structures ◽  
Thermal Residual Stresses ◽  
Compressive Stresses ◽  
Aa 2024

Friction Stir Welding (FSW) induces thermal residual stresses resulting in distortions in thin-walled structures. In order to understand and quantify this phenomenon, simulations and experiments of FSW on aluminium alloy (AA) 2024-T3 have been performed using different rotational and welding speeds. A sequentially coupled finite element (FE) model was used to study the residual stresses caused by the thermal cycling induced from FSW. The 3D FE model used temperature-dependent mechanical and thermophysical material properties. The predicted longitudinal stresses peaked at ~300 MPa and had a ‘‘W’’ profile with tensile stress peaks in the weld and compressive stresses outside the weld. In the FE model, the influence of process parameters on residual stress distribution was studied. The application of ‘hot’ welding conditions, i.e. low welding speed and high rotational speed, increased the residual stresses significantly, mainly in the transverse direction. Conversely, ‘cold’ welding conditions resulted in lower residual stresses. The magnitude and distribution of the residual stresses predicted by the FE model were validated by neutron diffraction. The results indicate a good agreement between the measured and predicted residual stresses in AA2024-T3.

scholarly journals Microstructure and Residual Stresses of AA2519 Friction Stir Welded Joints under Different Heat Treatment Conditions

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 834
Author(s):  
Lucjan Śnieżek ◽  
Robert Kosturek ◽  
Marcin Wachowski ◽  
Bogusz Kania
Keyword(s):  
Heat Treatment ◽  
Residual Stresses ◽  
Welded Joints ◽  
Precipitation Hardening ◽  
Cold Water ◽  
Traverse Speed ◽  
Welding Parameters ◽  
X Ray ◽  
Friction Stir ◽  
Treatment Conditions

The aim of this research was to investigate the effect of different heat treatment conditions of AA2519 friction stir welded joints on their microstructure and residual stresses. The following welding parameters have been used: 500 rpm tool rotation speed, 150 mm/min tool traverse speed, tool tilt angle 2°, pressure force 17 kN. The welded material was investigated in three different configurations: HT0, HT1, and HT2. The first type of weld (HT-0) was made using AA2519 alloy in non-precipitation hardened state and examined in such condition. The second type of weld (HT-1) has been performed on AA2519-T62, that corresponds to precipitation hardening condition. The last type of weld (HT2) was performed on annealed AA2519 and the obtained welds were subjected to the post-weld precipitation hardening process. The heat treatment was carried out in two stages: solution heat treatment (530 °C/2 h + cooling in cold water) and aging (165 °C/1 0 h). Residual stresses were measured using X-Ray diffraction patterns obtained from Bruker D8 Discover X-ray diffractometer utilizing the concepts of Euler cradle and polycapillary primary beam optics. The conducted research indicates that the best material properties: homogenous microstructure and uniform distribution of microhardness and compressive state of residual stresses were obtained for the HT-2 series samples subjected to heat treatment after the friction stir welding (FSW) process.

In-Plane Plane-Strain Formability Investigation of Friction Stir Welded Sheets Made of Dissimilar Aluminium Alloys

2013 ◽  
Vol 446-447 ◽  
pp. 301-305
Author(s):  
Mukesh Kumar ◽  
Satish V. Kailas ◽  
R. Ganesh Narayanan
Keyword(s):  
Plane Strain ◽  
Heat Input ◽  
Rotational Speed ◽  
Aluminium Alloys ◽  
Traverse Speed ◽  
Al Alloys ◽  
Welding Parameters ◽  
Strain Hardening Exponent ◽  
Friction Stir ◽  
Shoulder Diameter

In the present work, the influence of shoulder diameter, traverse speed, and rotational speed on the formability of friction stir welded sheets made between sheets of AA6061T6 and AA5052H32 Al alloys has been studied. In-Plane Plane-Strain formability tests are conducted for this purpose. It is understood from the results that the formability of welded sheets can be improved by optimizing the welding and tool parameters. A larger shoulder diameter, higher traverse speed, and lower rotational speed are favorable for improved formability, and strain hardening exponent of weld region. This is due to the fact that the heat input and subsequent microstructure evolved depends on the heat input, which depends on the welding parameters.

Stress Measurement Using a Bilayer Metal-Ceramic Strip

1992 ◽  
Vol 264 ◽  
Author(s):  
Shukla Kapur ◽  
Philip L. Flaltz
Keyword(s):  
Finite Element ◽  
Thermal Expansion ◽  
Residual Stresses ◽  
Finite Element Modelling ◽  
Stress Measurement ◽  
Second Phase ◽  
Thermal Expansion Mismatch ◽  
Element Modelling ◽  
Metal Ceramic ◽  
Stress Asymmetry

AbstractResidual stresses that develop in metal/ceramic bonded systems due to thermal expansion mismatch have been calculated using finite element modelling and measured experimentally using a simple bilayer strip. Bending in the strip occurs during cooling due to the stress asymmetry. Residual stresses are calculated by measuring the deflection of the strip and the temperature at which the strip is flat. Various compositions of both copper and nickel pastes, with and without glass and other second phase additions were evaluated on glass-ceramic. The effects of further processes, e.g. thermal cycling, brazing and plating, are also reported in this work.

Finite Element Modelling of Stress-Induced Fracture in Ti-Si-N Films

2014 ◽  
Vol 553 ◽  
pp. 10-15
Author(s):  
E.A. Flores-Johnson ◽  
Lu Ming Shen ◽  
R.K. Annabattula ◽  
P.R. Onck ◽  
Yao Gen Shen ◽  
...  
Keyword(s):  
Thin Films ◽  
Residual Stresses ◽  
Finite Element Modelling ◽  
Nanocomposite Coating ◽  
Industrial Applications ◽  
Coating Films ◽  
Element Modelling ◽  
Mechanical And Physical Properties ◽  
Buckling Delamination ◽  
Sputter Deposited

Nanocomposite coating films have been increasingly used in industrial applications because of their unique mechanical and physical properties. Residual stresses generated during the growth of sputter-deposited thin films due to a strain mismatch between the film and the substrate may lead to significant failure problems. Large residual stresses may generate buckling, delamination and film fracture. Although buckles with cracks in thin films have been experimentally observed, their origins are still not well understood.

scholarly journals Effect of Residual Stress on the Mechanical Properties of FSW Joints with SUS409L

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Yeong-Seok Lim ◽  
Sang-Hyuk Kim ◽  
Kwang-Jin Lee
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Residual Stresses ◽  
Welded Joints ◽  
Stress Measurement ◽  
Charpy Impact ◽  
Stir Zone ◽  
Hole Drilling ◽  
Friction Stir ◽  
Compressive Residual Stresses

This study was performed to investigate both the residual stress distribution and the effect of the residual stress formed at the welding region on the mechanical properties of the friction stir welded joints with 409L stainless steel sheets. Residual stress measurement with hole-drilling method; mechanical property evaluation including tensile test, Charpy impact test, and fatigue test; and microstructure observation were conducted. It has got no residual stresses to speak of at the center region of the stir zone because the stored stresses are released in the process of the dynamic recrystallization, while a small quantity of compressive residual stresses is formed at the surface region of the stir zone because of strong compression reaction by the tool shoulder. A considerable amount of compressive residual stresses is formed at the thermomechanical affected zone because of the synergy between the thermal expansion due to the heat conduction from the stir zone and mechanical compression by the tool. The formation of residual stresses shows a similar tendency between the advancing side and the retreating side. Both the mitigation of residual stress in the stir zone and the formation of compressive residual stress in the thermomechanical affected zone contribute to the improvement of the mechanical properties of the friction stir welded joints.

scholarly journals Predicting the Effects of Grain Size on Machining-Induced Residual Stresses in Steels

2014 ◽  
Vol 996 ◽  
pp. 634-639 ◽  
Author(s):  
Mohamed N.A. Nasr
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Residual Stresses ◽  
Finite Element Modelling ◽  
Material Strength ◽  
Grain Size Effect ◽  
Inverse Relation ◽  
Lower Yield ◽  
Element Modelling ◽  
Lower Yield Strength

The current study examines the effect of grain size on machining-induced residual stresses (RS), during turning, using finite element modelling. Based on the well-known inverse relation between grain size and material strength, the grain size effect was simulated via changing the workpiece yield strength. This was also done at different strain hardening rates. The model was validated using four materials. Larger grain size (lower yield strength) resulted in higher surface tensile RS. This is attributed to the surface layer being subjected to higher compressive plastic deformation, as well as higher workpiece temperatures, which both contribute to higher tensile RS.

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