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spot-welding
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Achieving high mechanical performance in protrusion friction stir spot welding (PFSSW) of DQSK steel compared to other techniques
, Article Materials Research Express ; Volume 5, Issue 10 , 2018 ; 20531591 (ISSN) ; Mousavizade, S. M ; Ezatpour, H. R ; Pouranvari, M ; Sharif University of Technology
Institute of Physics Publishing
2018
Abstract
Protrusion friction spot stir welding (PFSSW) was introduced as a novel method to produce keyhole-free welds of a drawing quality special killed low carbon steel (DQSK). The effects of welding parameters such as tool rotation speed and plunging depth were investigated on the mechanical properties and metallurgical aspects. The sheet/sheet joint interface of the welds produced by PFSSW was visible and non-planar compared to the conventional FSSW method. Microstructure and hardness were affected by dynamic recrystallization and transformation hardening in the stir zone. Hardness value of the stir zone produced by the present work was much lower than that produced by resistance spot welding...
Advanced approach to modify friction stir spot welding process
, Article Metals and Materials International ; Volume 26, Issue 10 , 2020 , Pages 1562-1573 ; Abbasi, M ; Abdollahzadeh, A ; Omidvar, H ; Sharif University of Technology
Korean Institute of Metals and Materials
2020
Abstract
Abstract: Nowadays, friction stir spot welding (FSSW) is used in automotive, rail vehicle construction, the aerospace industry, and electrical industry. In the current research, a modified version of the FSSW process entitled friction stir spot vibration welding was introduced to join Al5083 specimens. The joining specimens were vibrated normal to the tool movement direction, while the joint position cooled by passing coolant through the fixture. Different characteristics of developed joint namely microstructure, mechanical properties, corrosion behavior were studied. The results showed that stir zone grain size decreased significantly as the vibration was employed and the joint position was...
Fatigue life estimation of spot welds using a crack propagation-based method with consideration of residual stresses effect
, Article Materials Science and Engineering A ; Volume 527, Issue 23 , 2010 , Pages 6359-6363 ; 09215093 (ISSN) ; Kokabi, A. H ; Sharif University of Technology
2010
Abstract
In the present paper, a crack propagation-based fatigue life estimation approach has been proposed for resistance spot welds. The presented approach also takes into account the effect of welding residual stresses. It can provide an accurate and systematic prediction of the life of spot weld joints with various dimensions and shapes. Experimental verification tests confirmed the validity of the calculations and good agreement was found between the theoretical predictions and experimental data
Dissimilar Al/steel friction stir spot welding: To penetrate into the lower steel sheet or not?
, Article Science and Technology of Welding and Joining ; Volume 21, Issue 6 , 2016 , Pages 466-472 ; 13621718 (ISSN) ; Movahedi, M ; Kokabi, A. H ; Sharif University of Technology
Taylor and Francis Ltd
2016
Abstract
There has always been a question about which condition results in superior mechanical properties in friction stir spot welds: (i) when the tool tip penetrates into the lower sheet or (ii) when the tool tip does not touch it. Given the question, the effects of the tool penetration depth were investigated on the microstructure and mechanical behaviour of dissimilar Al-5083/St-12 joints produced by friction stir spot welding (FSSW). Two different processes named as non-penetrating and penetrating FSSW were used. Optical and scanning electron microscopes as well as microhardness and tensile-shear tests were utilised to examine the obtained joints. The results showed that the penetrating process...
Critical assessment: dissimilar resistance spot welding of aluminium/steel: challenges and opportunities
, Article Materials Science and Technology (United Kingdom) ; Volume 33, Issue 15 , 2017 , Pages 1705-1712 ; 02670836 (ISSN) ; Sharif University of Technology
Abstract
Dissimilar joining of aluminium and steel, especially using resistance spot welding as a critical process in vehicle manufacturing, is a key challenge for multi-materials lightweight design strategy. Controlling the formation and growth of Al5Fe2 intermetallic is the outstanding issue for producing high strength crash-resistance Al/steel dissimilar resistance spot welds. This critical assessment highlights the current understating regarding factors affecting the joint properties and approaches to control the interfacial reaction. Finally, the unresolved scientific challenges are discussed with the goal of shedding light on the path forward to produce reliable metallurgical bonding between...
Peak load and energy absorption of DP600 advanced steel resistance spot welds
, Article Ironmaking and Steelmaking ; Volume 44, Issue 9 , 2017 , Pages 699-706 ; 03019233 (ISSN) ; Pouranvari, M ; Salim, R. K ; Hashim, F. A ; Marashi, S. P. H ; Sharif University of Technology
Abstract
The paper aims at investigating the microstructure, failure mode transition, peak load and energy absorption of DP600 dual phase steel during the tensile-shear test. It was found that the welding current has profound effect on the load–displacement characteristics. In the low welding current, welds failed in interfacial failure mode. Increasing welding current resulted in sufficient weld nugget growth to promote double-sided pullout failure mode with improved mechanical properties. Further increase in the welding current caused expulsion and failure mode was changed to single-sided pullout with reduced energy absorption capability. It was found that the fusion zone size is the key parameter...
A pathway to produce strong and tough martensitic stainless steels resistance spot welds
, Article Science and Technology of Welding and Joining ; Volume 24, Issue 3 , 2019 , Pages 185-192 ; 13621718 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
Martensitic stainless steel (MSS) resistance spot welds are prone to quasi-cleavage interfacial failure with very low energy absorption capability due to formation of hard and brittle carbon and chromium rich martensite in the fusion zone (FZ). In this work, a new pathway is proposed to enhance strength/toughness of the MSS resistance spot welds based on modification of the FZ composition/microstructure via introducing a nickel interlayer. This altered the FZ microstructure from dual phase microstructure of martensite and δ-ferrite to austenitic microstructure with finely dispersed ultra-fine chromium rich carbides. Formation of a tough predominately austenitic microstructure in the FZ...
Prediction of the failure mode of automotive steels resistance spot welds
, Article Science and Technology of Welding and Joining ; Volume 25, Issue 6 , 2020 , Pages 511-517 ; Jaderian, S ; Mazaheri, Y ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
In this study, the critical nugget size, at which the failure state in tensile shear test changed from the interfacial failure mode to the pull-out failure one, was estimated as a function of nugget and base metal hardness. The proposed approach could address the effect of various parameters involved in resistance spot welding process, such as sheet thickness, base metal chemical composition and physical properties of electrodes and sheets. The reliability of the present model was evaluated using independent experimental results. Based on the obtained results, the effect of steel composition on critical nugget diameter was found to be more important, especially for the sheets thicker than...
Acoustic simulation of ultrasonic testing and neural network used for diameter prediction of three-sheet spot welded joints
, Article Journal of Manufacturing Processes ; Volume 64 , 2021 , Pages 1507-1516 ; 15266125 (ISSN) ; Farrahi, G. H ; Amiri, N ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Ultrasonic Testing (UT) is one of the most common types of nondestructive methods that is being used in various industries, especially in the automotive industry. In this paper, qualitative and quantitative control of resistance spot welds on three-sheet joints was studied. Initially, mathematical model of ultrasonic waves was extracted for triple sheet joints. Then, acoustic simulation of ultrasonic testing on spot welds was performed using Finite Element Method (FEM). Afterwards, A Multilayer Perceptron (MLP) neural network was used to classify spot welds based on their diameter. There was a mean error of 20.9 % between peak amplitudes of numerical and theoretical models which the most...
Reliability of Ultrasonic Technique Used for Defect Detection of Spot Welded Plates in Automotive Industry
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossien (Supervisor) ; Chizari, Mahmoud (Supervisor) ; kashizadeh, Kazem Reza (Co-Supervisor)
Abstract
Resistance Spot Welding (RSW) is one of the common techniques for connecting steel sheets in automotive industries. There are about 3000-5000 RSWs in the automotive chassis and body. Therefore, health and quality of RSW play a critical role in the final product performance. Also, welding process should be performed in a fully controlled program to ensure the durability of the vehicle body. In the automotive industry, there are various non-destructive methods (i.e., Chisel and Ultrasonic tests) and peel test as a destructive test (DT) to control the quality of RSW. Since the DT method is costly (waste of time, manpower, and materials), the main aim of the present research is to evaluate the...
Projection friction stir spot welding: a pathway to produce strong keyhole-free welds
, Article Science and Technology of Welding and Joining ; 2018 ; 13621718 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
This paper introduces a novel facile method, called projection friction stir spot welding, to produce a keyhole-free friction stir welds based on a pinless tool method involving using a specially designed projection on the surface of the backing anvil. The projection plays two key roles contributing to the bonding mechanism and the joint strength: (i) encouraging the material flow perpendicular to the joint interface and (ii) bending the joint interface at the edge of the projection. The process enables pathway to produce keyhole-free welds with superior mechanical performance in steel sheets compared to the other spot welding techniques. © 2018, © 2018 Institute of Materials, Minerals and...
Projection friction stir spot welding: a pathway to produce strong keyhole-free welds
, Article Science and Technology of Welding and Joining ; Volume 24, Issue 3 , 2019 , Pages 256-262 ; 13621718 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
This paper introduces a novel facile method, called projection friction stir spot welding, to produce a keyhole-free friction stir welds based on a pinless tool method involving using a specially designed projection on the surface of the backing anvil. The projection plays two key roles contributing to the bonding mechanism and the joint strength: (i) encouraging the material flow perpendicular to the joint interface and (ii) bending the joint interface at the edge of the projection. The process enables pathway to produce keyhole-free welds with superior mechanical performance in steel sheets compared to the other spot welding techniques. © 2018, © 2018 Institute of Materials, Minerals and...
Effect of expulsion on peak load and energy absorption of low carbon steel resistance spot welds
, Article Science and Technology of Welding and Joining ; Volume 13, Issue 1 , 2008 , Pages 39-43 ; 13621718 (ISSN) ; Abedi, A ; Marashi, P ; Goodarzi, M ; Sharif University of Technology
2008
Abstract
The effects of weld nugget size and expulsion on the performance of low carbon steel resistance spot weld have been investigated in the present paper. Failure mode, peak load and failure energy obtained in tensile-shear test have been used to describe the performance of spot weld. The influence of voids and porosity as well as electrode indentation associated with expulsion on peak load and failure energy is discussed. The results showed that although expulsion does not reduce the load carrying capacity of spot welds, it decreases their energy absorption capability which was attributed to the change of failure location due to excessive electrode indentation associated with expulsion. © 2008...
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...
Analysis of resistance spot welding process parameters effect on the weld quality of three-steel sheets used in automotive industry: Experimental and finite element simulation
, Article International Journal of Engineering, Transactions A: Basics ; Volume 33, Issue 1 , 2020 , Pages 148-157 ; Reza Kashyzadeh, K ; Minaei, M ; Sharifpour, A ; Riazi, S ; Sharif University of Technology
Materials and Energy Research Center
2020
Abstract
In the present research, the effects of spot-welding process parameters on the nugget diameter and electrode penetration depth of spot-welded joints were investigated. To achieve this, a spot-welded joint of three-thin sheet low carbon steels (same thicknesses of 0.8 mm) was simulated as an electerical-thermal-mechanical coupling of 3D finite element model. After validating the finite element simulation presented in this study by comparison with the experimental results for the spot diameter, various cases of spot welds were analyzed based on the design on experiment (i.e., Taguchi method). Six variables including electrode force, electric current, and quadrilateral times (squeeze, up-slope,...
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...
Crack initiation and kinking behaviours of spot welded coach peel specimens under cyclic loading
, Article Science and Technology of Welding and Joining ; Volume 12, Issue 8 , 2007 , Pages 696-702 ; 13621718 (ISSN) ; Kokabi, A. H ; Ekrami, A. A ; Motarjemi, A. K ; Sharif University of Technology
2007
Abstract
The present study Is carried out to investigate fatigue crack initiation and kinking behaviours of spot welded coach peel (CP) specimens of low carbon steel sheets subjected to cyclic loading by experimental and finite element analysis methods. Evaluations of fatigue crack growth stages were performed by crack tip plastic strains and J integral analyses and also by microhardness measurements on process zone. According to the experimental and analytical results, fatigue crack initiation and growing stages in the spot welded CP specimens can be divided to three stages. Stage I corresponds to 'gap sharpening stage' observed at the beginning steps of cyclic loading with crack growing on the...
Effect of weld nugget size on overload failure mode of resistance spot welds
, Article Science and Technology of Welding and Joining ; Volume 12, Issue 3 , 2007 , Pages 217-225 ; 13621718 (ISSN) ; Asgari, H. R ; Mosavizadch, S. M ; Hoveida Marashi, P ; Goodarzi, M ; Sharif University of Technology
2007
Abstract
In the present paper, effects of welding current, welding time, electrode pressure and holding time on the weld nugget size were studied. A failure mechanism was proposed to describe both interfacial and pullout failure modes. This mechanism was confirmed by SEM investigations. In the light of this mechanism, the effect of welding parameters on static weld strength and failure mode was studied. Then, an analytical model was proposed to predict failure mode and to estimate minimum nugget diameter (critical diameter) to ensure pullout failure mode in shear tensile test. On the contrary to existing industrial standards, in this model, critical nugget diameter is attributed to metallurgical...
On the failure behavior of highly cold worked low carbon steel resistance spot welds
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Vol. 45, issue. 3 , Oct , 2014 , p. 1376-1389 ; 10735623 ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
Abstract
Highly cold worked (HCW) low carbon steel sheets with cellular structure in the range of 200 to 300 nm are fabricated via constrained groove pressing process. Joining of the sheets is carried out by resistance spot welding process at different welding currents and times. Thereafter, failure behavior of these welded samples during tensile-shear test is investigated. Considered concepts include; failure load, fusion zone size, failure mode, ultimate shear stress, failure absorbed energy, and fracture surface. The results show that HCW low carbon steel spot welds have higher failure peak load with respect to the as-received one at different welding currents and times. Also, current limits for...
Control of resistance spot welding using model predictive control
, Article 9th International Conference on Electrical and Electronics Engineering, 26 November 2015 through 28 November 2015 ; 2015 , Pages 864-868 ; 9786050107371 (ISBN) ; Haeri, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
Nowadays, the need for industrial processes with sufficient accuracy, efficiency, and flexibility to compete world markets is inevitable. On the other hand, the advent of control techniques and increased computation power of CPUs allow implementation of complex controllers using optimization techniques to provide higher efficiency and economic productivity. Model predictive control refers to a wide range of optimization-based control methods applying explicit models to predict its prospective use. These methods of control compute control signal by minimizing the cost function so that the process output becomes very close to the optimal path. In this paper, we use a new model predictive...