The Experts below are selected from a list of 18492 Experts worldwide ranked by ideXlab platform

V Balasubramanian - One of the best experts on this subject based on the ideXlab platform.

  • effect of Welding processes on mechanical and microstructural characteristics of high strength low alloy naval grade steel joints
    Defence Technology, 2015
    Co-Authors: Ragu S Nathan, V Balasubramanian, S Malarvizhi
    Abstract:

    Abstract Naval grade high strength low alloy (HSLA) steels can be easily welded by all types of fusion Welding processes. However, fusion Welding of these steels leads to the problems such as cold cracking, residual stress, distortion and fatigue damage. These problems can be eliminated by solid state Welding process such as friction stir Welding (FSW). In this investigation, a comparative evaluation of mechanical (tensile, impact, hardness) properties and microstructural features of shielded metal arc (SMA), gas metal arc (GMA) and friction stir welded (FSW) naval grade HSLA steel joints was carried out. It was found that the use of FSW process eliminated the problems related to fusion Welding processes and also resulted in the superior mechanical properties compared to GMA and SMA welded joints.

  • establishing relationships between mechanical properties of aluminium alloys and optimised friction stir Welding process parameters
    Materials & Design, 2012
    Co-Authors: S Rajakumar, V Balasubramanian
    Abstract:

    Abstract Friction stir Welding (FSW) is a solid state Welding process for joining aluminium alloys and is employed in aerospace, rail, automotive and marine industries. In FSW, the base metal properties such as yield strength, hardness and ductility control the plastic flow of the material under the action of a rotating non-consumable tool. The FSW process parameters such as, the tool rotational speed, the Welding speed and the axial force play a major role in deciding the weld quality. In this investigation, FSW joints were made using six different grades of aluminium alloys (AA1100, AA2219, AA2024, AA6061, AA7039, and AA7075) using different levels of process parameters. Macrostructural analysis was carried out to identify the feasible working range of process parameters. The optimal Welding conditions to attain maximum strength for each alloy were identified using Response Surface Methodology (RSM). Empirical relationships were established between the base metal mechanical properties of aluminium alloys and optimised FSW process parameters. These relationships can be effectively used to predict the optimised FSW process parameters from the known base metal properties (yield strength, elongation and hardness).

  • optimising diffusion bonding parameters to maximize the strength of aa6061 aluminium and az31b magnesium alloy joints
    Materials & Design, 2012
    Co-Authors: Joseph M Fernandus, T Senthilkumar, V Balasubramanian
    Abstract:

    The main difficulty when joining magnesium (Mg) and aluminum (Al) alloys by fusion Welding process lies in the existence of oxide films and formation of brittle intermetallic in the weld region. However, Solid-State Welding processes such as friction Welding and diffusion bonding are suitable processes to join these two materials. The diffusion bonding process parameters such as bonding temperature, bonding pressure, holding time, and surface roughness of the bond specimen play a major role to determine the joint strength. In this investigation, an attempt was made to develop empirical relationships to predict the lap shear strength and bonding strength of diffusion bonded dissimilar joints of AZ61A magnesium and AA6061 aluminum alloys, incorporating the above-mentioned parameters. Response surface methodology (RSM) was applied to optimize the diffusion bonding process parameters to attain the maximum shear strength and bonding strength of the joint. From this investigation, it is found that the bonds fabricated with the bonding temperature of 420.43°C, bonding pressure of 7.70 MPa, holding time of 27.15 min, and surface roughness of 0.10 μm exhibited maximum shear strength and bonding strength of 51.24 and 72.10 MPa, respectively.

  • relationship between base metal properties and friction stir Welding process parameters
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008
    Co-Authors: V Balasubramanian
    Abstract:

    Friction stir Welding (FSW) is a solid state Welding process for joining aluminum alloys and has been employed in aerospace, rail, automotive and marine industries for joining aluminium, magnesium, zinc and copper alloys. In FSW, the base metal properties such as yield strength, ductility and hardness control the plastic flow of the material under the action of rotating non-consumable tool. The FSW process parameters such as tool rotational speed, Welding speed, axial force, etc. play a major role in deciding the weld quality. In this investigation, an attempt has been made to establish relationship between the base material properties and FSW process parameters. FSW joints have been made using five different grades of aluminium alloys (AA1050, AA6061, AA2024, AA7039 and AA7075) using different combinations of process parameters. Macrostructural analysis has been done to check the weld quality (defective or defect free). Empirical relationships have been established between base metal properties and tool rotational speed and Welding speed, respectively. The developed empirical relationships can be effectively used to predict the FSW process parameters to fabricate defect free welds.

Per F Peterson - One of the best experts on this subject based on the ideXlab platform.

  • tube expansion and diffusion bonding of 316l stainless steel tube to tube sheet joints using a commercial roller tube expander
    Journal of Materials Processing Technology, 2016
    Co-Authors: Nils Haneklaus, Rony Reuven, Cristian Cionea, Peter Hosemann, Per F Peterson
    Abstract:

    Abstract Diffusion bonding is a Solid-State Welding technique to join metallic and non-metallic materials. Due to geometrical considerations, fabrication and possible materials choices diffusion bonding was chosen here to support tube-to-tube sheet joints of large coil-wound heat exchangers (CWHE) made from 316L stainless steel. In contrast to traditional diffusion bonding where pressure is applied constantly during heat treatment, pressure is applied here initially prior to heat treatment using a commercial three roller tube expander. Processing parameters of this novel approach are presented in this study. Mechanical pull-out tests were conducted to evaluate if the manufactured joints are sufficiently bond to guarantee safe operation of the device. It was found that diffusion bonding followed tube expansion increases the pull-out force nearly threefold from a mean of 3.4 kN to 9.2 kN at which level the tube ruptures so that higher loads could not be measured. Tube-to-tube sheet joints fabricated using tube expansion and diffusion bonding met the engineering requirement, tube rupture against mechanical pull-out, set for this study.

  • tube expansion and diffusion bonding of 316l stainless steel tube to tube sheet joints using a commercial roller tube expander
    Journal of Materials Processing Technology, 2016
    Co-Authors: Nils Haneklaus, Rony Reuven, Cristian Cionea, Peter Hosemann, Per F Peterson
    Abstract:

    Abstract Diffusion bonding is a Solid-State Welding technique to join metallic and non-metallic materials. Due to geometrical considerations, fabrication and possible materials choices diffusion bonding was chosen here to support tube-to-tube sheet joints of large coil-wound heat exchangers (CWHE) made from 316L stainless steel. In contrast to traditional diffusion bonding where pressure is applied constantly during heat treatment, pressure is applied here initially prior to heat treatment using a commercial three roller tube expander. Processing parameters of this novel approach are presented in this study. Mechanical pull-out tests were conducted to evaluate if the manufactured joints are sufficiently bond to guarantee safe operation of the device. It was found that diffusion bonding followed tube expansion increases the pull-out force nearly threefold from a mean of 3.4 kN to 9.2 kN at which level the tube ruptures so that higher loads could not be measured. Tube-to-tube sheet joints fabricated using tube expansion and diffusion bonding met the engineering requirement, tube rupture against mechanical pull-out, set for this study.

J Dos M F Santos - One of the best experts on this subject based on the ideXlab platform.

  • fatigue life assessment of friction spot welded 7050 t76 aluminium alloy using weibull distribution
    International Journal of Fatigue, 2016
    Co-Authors: P S Effertz, V Infante, L Quintino, U F H Suhuddin, Stefanie Hanke, J Dos M F Santos
    Abstract:

    Abstract Friction spot Welding is a solid state Welding process suitable to obtain spot like-joints in overlap configuration. The process is particularly useful to weld lightweight materials in similar and dissimilar combinations, and therefore an interesting alternative to other joining techniques (rivets, resistance Welding, etc.). Optimum process parameters have been defined using the Taguchi method by maximizing the response variable (the lap shear strength). A study of the fatigue life was carried out on specimens welded with the above mentioned optimized process parameters. Fatigue tests were performed using a stress ratio of R = 0.10. Two-parameter Weibull distribution was used to analyze statistically the fatigue life for the joined overlapped sheets. Subsequently, the Weibull plots were drawn, as well as S–N curves considering different reliability levels. The results show that for a relatively low load, corresponding to 10% of the maximum supported by the joint, the number of cycles surpasses 1 × 106, hence infinite life of the service component can be attributed. Fatigue fracture surfaces were investigated for the highest and lowest loads tested using scanning electron microscope (SEM).

  • mechanical and microstructural investigation of friction spot welded aa6181 t4 aluminium alloy
    Materials & Design, 2011
    Co-Authors: Tonilson De Souza Rosendo, J Dos M F Santos, Bruno Serafim Parra, Marco Antonio Durlo Tier, A A M Da Silva, Telmo Roberto Strohaecker, Nelson Guedes De Alcântara
    Abstract:

    Abstract Friction spot Welding (FSpW) is a solid state Welding process suitable for spot joining lightweight low melting point materials like aluminium and magnesium alloys. The process is performed by plunging a rotating three-piece tool (clamping ring, sleeve and pin) that creates a connection between sheets in overlap configuration by means of frictional heat and mechanical work. The result is a spot welded lap connection with minimal material loss and a flat surface with no keyhole. FSpW has been performed in a 1.7 mm-thick AA6181-T4 aluminium alloy using different Welding parameters (rotation speed and joining time) aiming to produce high quality connections in terms of microstructure and mechanical performance. Microstructural features of the FSpW connections were analysed by optical microscopy; while mechanical performance was investigated in terms of hardness and tensile testing. Connections with shear strength close to 7 kN were obtained with high reproducibility. The results also showed that geometric features of the connection play an important role on the fracture mechanism and hence on the mechanical performance of the connections.

Rony Reuven - One of the best experts on this subject based on the ideXlab platform.

  • tube expansion and diffusion bonding of 316l stainless steel tube to tube sheet joints using a commercial roller tube expander
    Journal of Materials Processing Technology, 2016
    Co-Authors: Nils Haneklaus, Rony Reuven, Cristian Cionea, Peter Hosemann, Per F Peterson
    Abstract:

    Abstract Diffusion bonding is a Solid-State Welding technique to join metallic and non-metallic materials. Due to geometrical considerations, fabrication and possible materials choices diffusion bonding was chosen here to support tube-to-tube sheet joints of large coil-wound heat exchangers (CWHE) made from 316L stainless steel. In contrast to traditional diffusion bonding where pressure is applied constantly during heat treatment, pressure is applied here initially prior to heat treatment using a commercial three roller tube expander. Processing parameters of this novel approach are presented in this study. Mechanical pull-out tests were conducted to evaluate if the manufactured joints are sufficiently bond to guarantee safe operation of the device. It was found that diffusion bonding followed tube expansion increases the pull-out force nearly threefold from a mean of 3.4 kN to 9.2 kN at which level the tube ruptures so that higher loads could not be measured. Tube-to-tube sheet joints fabricated using tube expansion and diffusion bonding met the engineering requirement, tube rupture against mechanical pull-out, set for this study.

  • tube expansion and diffusion bonding of 316l stainless steel tube to tube sheet joints using a commercial roller tube expander
    Journal of Materials Processing Technology, 2016
    Co-Authors: Nils Haneklaus, Rony Reuven, Cristian Cionea, Peter Hosemann, Per F Peterson
    Abstract:

    Abstract Diffusion bonding is a Solid-State Welding technique to join metallic and non-metallic materials. Due to geometrical considerations, fabrication and possible materials choices diffusion bonding was chosen here to support tube-to-tube sheet joints of large coil-wound heat exchangers (CWHE) made from 316L stainless steel. In contrast to traditional diffusion bonding where pressure is applied constantly during heat treatment, pressure is applied here initially prior to heat treatment using a commercial three roller tube expander. Processing parameters of this novel approach are presented in this study. Mechanical pull-out tests were conducted to evaluate if the manufactured joints are sufficiently bond to guarantee safe operation of the device. It was found that diffusion bonding followed tube expansion increases the pull-out force nearly threefold from a mean of 3.4 kN to 9.2 kN at which level the tube ruptures so that higher loads could not be measured. Tube-to-tube sheet joints fabricated using tube expansion and diffusion bonding met the engineering requirement, tube rupture against mechanical pull-out, set for this study.

Antonino Squillace - One of the best experts on this subject based on the ideXlab platform.

  • Surface and mechanical characterization of stationary shoulder friction stir welded lap joints: experimental and numerical approach
    International Journal of Material Forming, 2020
    Co-Authors: Gianluca Buffa, Livan Fratini, Filomena Impero, Attilio Masnata, Fabio Scherillo, Antonino Squillace
    Abstract:

    Friction Stir Welding (FSW) is one of the most used Solid-State Welding processes in the aeronautical, aerospace, ground transportation and naval fields. Stationary Shoulder Friction Stir Welding (SSFSW) is a recently introduced variant of the process allowing lower heat input into the joints, with beneficial effects in terms of joint mechanical properties, microstructure and top surface finish. In the paper, lap joints produced by SSFSW and made out of AA6082-T6 aluminum alloy sheets have been analyzed with the aim to investigate the effect of the stationary shoulder on the lap joints surface, metallurgical, and mechanical properties. The lap joints produced by SSFSW have been compared to the ones produced by “conventional” FSW in order to highlight the differences between the two processes. The top surface of the joints obtained with the two processes has been quantitatively evaluated. Finally, a dedicated numerical model has been utilized to highlight the causes of the observed differences through the distributions of the main field variables, namely temperature, strain and strain rate. It was found that SSFSW results in narrower weld nugget and smaller areas involved by micro hardness reduction caused by smaller peak temperature and high temperature zone. Additionally, better surface quality was found for the joint welded by SSFSW with lower heights and flash, allowing to avoid subsequent finishing operations needed for most industrial applications.

  • study of the metallurgy of a dissimilar ti 6al 4v stainless steel linear fiction welded joints
    Key Engineering Materials, 2015
    Co-Authors: Filomena Impero, Fabio Scherillo, Antonino Squillace, Antonello Astarita, Kathryn A Beamish, Michele Curioni, X Zhou
    Abstract:

    This paper deals with the investigation of the metallurgy of a dissimilar Ti-6Al-4V-stainless steel joint linear friction welded. In particular two different stainless steel were considered: AISI 304 and AISI 316. These two alloys differs in the Molybdemun content. Metallographic observations, EDS analysis and Vickers Microhardness measurements were carried out, particular attention was focused on the study of the intermetallic compounds and on the microstructures of the different zones produced by the process. As usual for solid state Welding processes, three different zones can be identified: the parent material, the heat affected zone (HAZ) and the thermo-mechanical affected zone (TMAZ), furthermore a very thin joining line, rich of intermetallic compounds, was also observed. In this zone diffusive phenomena also occurred resulting in a variation of the alpha phase content on the titanium side.In the TMAZ, the bimodal microstructure of the parent material was deformed and the presence of elongated alpha grains with broken beta-phase particles was established. Moreover it was observed that in the weld region, exposure to supertransus temperatures (995°C) combined with hot-deformation working and rapid cooling after joining induced the recrystallization of a martensitic beta grain structure. Concerning the joint between Ti-6Al-4V and AISI 316 some cracks were observed within the weld line, this due to the presence of brittle intermetallics compounds in this zone. The formation of these intermetallics was promoted by the presence of Molybdenum.

  • a comparison between fsw and tig Welding techniques modifications of microstructure and pitting corrosion resistance in aa 2024 t3 butt joints
    Journal of Materials Processing Technology, 2004
    Co-Authors: Antonino Squillace, A De Fenzo, G Giorleo, F Bellucci
    Abstract:

    Abstract An experimental investigation has been carried out, in present paper, on microstructure and corrosion resistance of weld butt joints of AA 2024-T3. Two different Welding processes have been considered: a conventional tungsten inert gas (TIG) process and an innovative solid state Welding process known as friction stir Welding (FSW). Micro-hardness measurements allow pointing out a general decay of mechanical properties of TIG joints, mainly due to high temperatures experienced by material. In FSW joint, instead, lower temperatures involved in process and severe plastic deformations induced by tool motion allow rising of a complex situation: by a general point of view a slight decay of mechanical properties is recorded in nugget zone, flow arm and thermo-mechanically altered zone (TMAZ), while in heat-affected zone (HAZ), due to starting heat treatment of alloy under investigation, a light improvement of such properties is appreciated. In flow arm and in nugget zone, however, a light recovery of hardness, w.r.t. TMAZ zone, is recorded, due to the re-crystallisation of a very fine grain structure. Polarisation curve tests and electrochemical impedance spectroscopy, performed in this paper, allow assessing a generalised nobler behaviour of weld bead with respect to parent alloy. In FSW joint, however, the differences between the three examined zone are not so evident as in TIG joint; what is more, inside FSW weld bead, retreating zone shows a behaviour nobler than advancing one.