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Simulation of welding residual stresses in resistance spot welding, FE modeling and X-ray verification
, Article Journal of Materials Processing Technology ; Volume 205, Issue 1-3 , 26 August , 2008 , Pages 60-69 ; 09240136 (ISSN) ; Serajzadeh, S ; Kokabi, A. H ; Sharif University of Technology
2008
Abstract
In the present study, an electro-thermo-mechanical model is utilized to predict electrical potential, temperature and residual stress distributions during different stages of resistance spot welding. In order to improve accuracy, material properties including physical, thermal and mechanical properties supposed to be temperature-dependent. The employed model is capable of considering the effects of welding parameters such as heat input and welding time on residual stress distribution. The model results are then compared with the measured residual stresses and good agreement is observed. Predictions show that maximum tensile residual stresses are located at the weld center while they are...
Effect of Welding Parameters on Microstructure and Mechanical Properties of Friction stir Spot Welded Aluminum Alloy
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor)
Abstract
Friction stir spot welding (fssw) is a newly-developed solid state joining technology. In this study, normal fssw is applied to join the AlMg6 aluminum alloy sheets with 3 mm thickness and then the effect of the rotational speed and dwell time on microstructure and mechanical properties is discussed. The hardness profile of the welds exhibited a W-shaped appearance and minimum hardness was measured in the HAZ. The results of tensile/shear tests indicate that the joint strength increases and after a special rotational speed it decreases. Also the strength increases and after a special dwell time it decreases . At the rotational speed of 1500 rpm and dwell time of 6 sec, the...
Design and Manufacture of Friction Stir Spot Welding (FSSW) Machine with Ability of Refilling and Study on Effects of Welding Parameters on Al1100 Joint
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor)
Abstract
Friction Stir Spot Welding (FSSW) with ability of refilling weld’s keyhole, is one of the new solid state joining processes which have gained many applications, especially in automobile industry. Considering newness of the process, first part of this study has been dedicated to design and manufacture of a FSSW machine which is done entirely by author of this study. Second part was survey on effect of parameters such as Tool rotation speed, Weld time, and Forge time for refilling the hole, on properties of an aluminum joint. After welds were made, specimens were subjected to Lap-shear tensile test, after that, studies on macro and microstructure have been carried out. Generally an increase in...
Microstructure and mechanical properties in dissimilar butt friction stir welding of severely plastic deformed aluminum AA 1050 and commercially pure copper sheets
, Article Journal of Materials Science and Technology ; Vol. 30, issue. 8 , 2014 , p. 826-834 ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
Abstract
In this study, AA 1050 aluminum alloy and commercially pure copper in annealed and severely plastic deformed conditions were used. The technique used for imposing the severe strain to the sheets was constrained groove pressing (CGP) process. The annealed and severely plastic deformed sheets were subjected to friction stir welding (FSW) at different rotation and traverse speeds. Cu was placed in advancing side. Constant offset of approximately 1 mm was used toward Al side for all welds. A range of welding parameters which can lead to acceptable welds with appropriate mechanical properties was found. For the FSWed CGPed samples, it was observed that the welding heat input caused grain growth...
Effect of welding parameters on semisolid stir welding of Mg–9Al–1Zn magnesium alloy
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 26, Issue 10 , 2016 , Pages 2586-2594 ; 10036326 (ISSN) ; Aashuri, H ; Kokabi, A. H ; Sharif University of Technology
Nonferrous Metals Society of China
2016
Abstract
Semisolid stir welding of AZ91 was investigated with focus on the joining temperature and rotational speed. An Mg–25%Zn interlayer was located between two AZ91 pieces and the system was heated up to the semisolid state of base metal and interlayer. The weld seam was stirred using a drill-tip at different joining temperatures and rotational speeds. Optical and scanning electron microscopes were employed to study microstructure, cavity formation, and segregation. Hardness profile and shear punch test were also employed to rank the welds based on their quality and homogeneity. Results showed that the lowest cavity content (2.1%) with the maximum ultimate shear strength (about 188 MPa) was...
Energy absorption of friction stir welded 1050 aluminum sheets through wedge tearing
, Article Materials and Design ; Volume 93 , 2016 , Pages 216-223 ; 02641275 (ISSN) ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
In this research, 1050 aluminum alloy sheets were welded through Friction Stir Welding technique at different rotational speeds (ω) and advance rates (V) in order to investigate the effects of welding parameters on the energy absorption. Wedge tearing test was then conducted on the specimens in two directions of 0 and 90 degrees relative to the weld line. Energy absorption was revealed to be much higher in the welded specimens in comparison with the non-welded sheets. This increase in the amount of absorbed energy is due to the fine equiaxed grain structure formed in the stir zone of the weld which increases the strength. It was also concluded that when movement of the wedge is parallel to...
Investigation of structural and mechanical properties of magnetic pulse welded dissimilar aluminum alloys
, Article Journal of Manufacturing Processes ; Volume 37 , 2019 , Pages 292-304 ; 15266125 (ISSN) ; Abdollah zadeh, A ; Sarvari, M ; Pouranvari, M ; Miresmaeili, R ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The present study aimed to join AA4014 to AA7075 by using magnetic pulse welding (MPW). In addition, acceptable joints were achieved by selecting welding parameters such as collision angle and discharge energy appropriately. Changing collision angle and discharge energy can influence the velocity, leading to the formation of three different types of welding interfaces with wavy, molten wavy and porous morphologies. The formation of these various morphologies is mainly associated with different collision angle parameters. The hardness of the welding interface with molten layer was significantly higher than that of the base metals due to the grain refinement phenomenon occurring through the...
Resistance spot welding of ultra-fine grained steel sheets produced by constrained groove pressing: Optimization and characterization
, Article Materials Characterization ; Volume 69 , 2012 , Pages 71-83 ; 10445803 (ISSN) ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
2012
Abstract
Constrained groove pressing as a severe plastic deformation method is utilized to produce ultra-fine grained low carbon steel sheets. The ultra-fine grained sheets are joined via resistance spot welding process and the characteristics of spot welds are investigated. Resistance spot welding process is optimized for welding of the sheets with different severe deformations and their results are compared with those of as-received samples. The effects of failure mode and expulsion on the performance of ultra-fine grained sheet spot welds have been investigated in the present paper and the welding current and time of resistance spot welding process according to these subjects are optimized....
Effect of welding parameters on microstructure, mechanical properties and hot cracking phenomenon in Udimet 520 superalloy
, Article Materials and Design ; Volume 36 , 2012 , Pages 94-99 ; 02613069 (ISSN) ; Akbarpour, M. R ; Parvizi, S ; Kokabi, A. H ; Sadrnezhaad, S. K ; Sharif University of Technology
2012
Abstract
In the present research, different weld layers were deposited on a 1.2714 steel die by gas tungsten arc (GTA) welding with the weld wire of Udimet 520, and effects of welding parameters on microstructure and mechanical properties of Udimet 520 superalloy were investigated. The results showed Udimet 520 weld with cellular-dendritic and rarely dendritic structure including γ matrix rich of Cr, Mo and W, low percentage associated with order morphology and relative uniform distribution of MC type carbides. Udimet 520 alloy showed high resistance against hot cracking during welding and hot cracking occurred only at high input heat values. Also, cracking during welding occurred at the places that...
Mechanical properties and microstructure of resistance spot welded severely deformed low carbon steel
, Article Materials Science and Engineering A ; Volume 529, Issue 1 , 2011 , Pages 237-245 ; 09215093 (ISSN) ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
2011
Abstract
The welding of nanostructured low carbon steel sheets produced by severe plastic deformation (SPD) has been considered in the present paper. Constrained groove pressing (CGP) method is used for imposing the severe plastic deformation to the steel sheets as a large pre-strain. The SPDed sheets are joined using resistance spot welding (RSW) process. The results show that severe plastic deformation can effectively increase the electrical resistivity of steel sheets; therefore it can affect the microstructure and mechanical properties of spot welds. Microstructure and mechanical properties of fusion zone, heat affected zone (HAZ), recrystallized zone and base metal of SPDed sheets are...
Effect of welding parameters on residual stresses in dissimilar joint of stainless steel to carbon steel
, Article Journal of Materials Science ; Volume 46, Issue 9 , 2011 , Pages 3225-3232 ; 00222461 (ISSN) ; Serajzadeh, S ; Kokabi, A. H ; Fischer, A ; Sharif University of Technology
2011
Abstract
In this study, a thermo-mechanical model was utilized to investigate the effects of welding parameters on the distribution of residual stresses in dissimilar TIG welds of low carbon and ferritic stainless steels. To solve the governing thermal and mechanical problems, a finite element program, ANSYS, was employed while the different aspects such as welding sequence and dilution were considered in the numerical solution. To validate the predictions, the model results were compared with the residual stresses measured by X-ray diffraction technique and a reasonable agreement was found. The results show that the magnitude of tensile residual stresses decrease as the welding current increases...
Effects of heat input in friction stir welding on microstructure and mechanical properties of AA3003-H18 plates
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 25, Issue 7 , July , 2015 , Pages 2147-2155 ; 10036326 (ISSN) ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
Nonferrous Metals Society of China
2015
Abstract
The non-heat-treatable AA3003-H18 plates were joined by friction stir welding (FSW) to achieve a proper joint by optimizing the welding parameters. For this purpose, the effects of heat input on microstructure and mechanical properties of the welded samples were investigated by changing the ratios of rotational speed (800-1200 r/min) to travel speed (40-100 mm/min) (ω/v). It was revealed that the grain growth rate was strongly increased with the increase of the heat input by rotational speed at constant travel speed, while the grain growth rate was slightly increased with the increase of the heat input by travel speed at constant rotational speed. Subsequently, hardness reduction was...
Effect of intermetallic compounds on the fracture behavior of dissimilar friction stir welding joints of Mg and Al alloys
, Article International Journal of Minerals, Metallurgy and Materials ; Volume 26, Issue 10 , 2019 , Pages 1285-1298 ; 16744799 (ISSN) ; Sajuri, Z ; Selamat, N. F. M ; Omar, M. Z ; Miyashita, Y ; Kokabi, A. H ; Sharif University of Technology
University of Science and Technology Beijing
2019
Abstract
Joining Mg to Al is challenging because of the deterioration of mechanical properties caused by the formation of intermetallic compounds (IMCs) at the Mg/Al interface. This study aims to improve the mechanical properties of welded samples by preventing the fracture location at the Mg/Al interface. Friction stir welding was performed to join Mg to Al at different rotational and travel speeds. The micro structure of the welded samples showed the IMCs layers containing Al12Mg17 (γ) and Al3Mg2 (β) at the welding zone with a thickness (> 3.5
Investigation on the wear properties of Ti/TiC/TiN composite coatings prepared by powder cored wires through TIG method at nitrogen atmosphere on titanium substrate
, Article Materials Research ; Volume 22, Issue 2 , 2019 ; 15161439 (ISSN) ; Allahyari, A. A ; Sharif University of Technology
Universidade Federal de Sao Carlos
2019
Abstract
In this present study, Tungsten Inert Gas (TIG) welding and powder filled cored wires with nitrogen shielding gas were utilized to produce TiC and TiN surface composite coatings on the titanium (Ti) sheet substrate. The TIG procedure was done at same welding parameters for all of prepared samples. Phase analysis and microstructures were done by X-ray Diffraction (XRD), Energy-Dispersive X-ray Spectroscopy (EDS), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). The obtained results from XRD and EDS demonstrated that the presence of crystalline phases of TiC, TiN and Ti. SEM and OM exhibited formation of the spherical and dendritic TiC particles in a martensitic matrix and also,...
Investigation on the wear properties of Ti/TiC/TiN composite coatings prepared by powder cored wires through TIG method at nitrogen atmosphere on titanium substrate
, Article Materials Research ; Volume 22, Issue 2 , 2019 ; 15161439 (ISSN) ; Ammari Allahyari, A ; Sharif University of Technology
Universidade Federal de Sao Carlos
2019
Abstract
In this present study, Tungsten Inert Gas (TIG) welding and powder filled cored wires with nitrogen shielding gas were utilized to produce TiC and TiN surface composite coatings on the titanium (Ti) sheet substrate. The TIG procedure was done at same welding parameters for all of prepared samples. Phase analysis and microstructures were done by X-ray Diffraction (XRD), Energy-Dispersive X-ray Spectroscopy (EDS), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). The obtained results from XRD and EDS demonstrated that the presence of crystalline phases of TiC, TiN and Ti. SEM and OM exhibited formation of the spherical and dendritic TiC particles in a martensitic matrix and also,...
Evolution of microstructures and mechanical properties in similar and dissimilar friction stir welding of AA5086 and AA6061
, Article Materials Science and Engineering A ; Volume 528, Issue 28 , 2011 , Pages 8071-8083 ; 09215093 (ISSN) ; Serajzadeh, S ; Kokabi, A. H ; Sharif University of Technology
2011
Abstract
In this work, thermo-mechanical behavior and microstructural evolution in similar and dissimilar friction stir welding of AA6061-T6 and AA5086-O have been investigated. Firstly, the thermo-mechanical behaviors of materials during similar and dissimilar FSW operations have been predicted using three-dimensional finite element software, ABAQUS, then, the mechanical properties and the developed microstructures within the welded samples have been studied with the aid of experimental observations and model predictions. It is found that different strengthening mechanisms in AA5086 and AA6061 result in complex behaviors in hardness of the welded cross section where the hardness variation in similar...
Mechanical characteristics improvement of spot-welded dissimilar steels in different thickness
, Article Proc. of the Int. Conf. on Advances in Welding Science and Technology for Construction, Energy and Transportation, AWST 2010, held in Conj. with the 63rd Annual Assembly of IIW 2010, 11 July 2010 through 17 July 2010, Istanbul ; 2010 , Pages 803-810 ; 9786056141911 (ISBN) ; Kokabi, A. H ; Adineh, A ; Mansourzadeh, S. A ; Ghasemzadeh, H ; Ardakani, R. T ; Sharif University of Technology
2010
Abstract
Resistance spot welding of dissimilar materials especially in different thickness is generally more challenging than that of similar materials due to differences in the physical, chemical and mechanical properties of the base metals. And also when the part is under static and dynamic forces the health of spot-welds is crucial. Hence, the influence of welding parameters such as current, time, applied force and hold time on the shear-tensile load has been investigated in this study. Moreover, in this research the case study is one of the most important body parts of the vehicle which is front wheel house, and effect of above-mentioned parameter on the strength of spot-welds has been...