Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

Rapid tool degradation poses a critical challenge for joining of high carbon steels using friction stir welding (FSW) despite its ability to provide sound and defect-free welded joints. Tools of tungsten carbide with nickel binder phase (WC-Ni) are potential alternatives as they exhibit good strength and toughness. A detailed examination on the wear and consequent damage of WC-Ni tools for FSW of steels is reported in this work. The results show that the longevity of the WC-Ni tools is improved at relatively higher welding speed and lower tool rotational speed during FSW of high carbon steels. In contrast, higher tool rotational speeds and lower welding speeds result in higher rate of heat generation and elevated temperature leading to adhesion wear and oxidation of the tools. In FSW of typical 3-mm-thick high carbon steel plates, a tool rotational speed of 300 rpm and welding speed of 150 mm min−1 resulted in the minimum tool wear and allowed the use of a single tool up to 1000 mm without any significant damage. © 2021, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.

Department of Mechanical Engineering

World University root node

International Journal of Advanced Manufacturing Technology

Degradation of nickel-bonded tungsten carbide tools in friction stir welding of high carbon steel

Tecnologia em Metalurgia, Materiais e Minera{\c{c}}{\~{a}}o

Probing underlying mechanisms for PCBN tool decay during friction stir welding of nickel-based alloys

India-UK SPARC Webinar on Metal Additive Manufacturing and Friction Stir Processing: Present and Future

Friction hydro-pillar processing (FHPP) is a novel technique that involves solid-state joining of an external plug onto a substrate by plastic deformation. A systematic investigation on material flow during FHPP is required but rarely reported. The present work reports a coupled theoretical and a three-dimensional X-ray computer tomography-based experimental study using a Ti-alloy as a tracer material to realise the material flow during FHPP of a AISI 4140 steel substrate. The cumulative results showed that the central portion of the plug deformed in a series of layer-wise shear planes. However, the plasticised material towards the outer area of the plug flowed through the clearance between the plug and the substrate with excess volume moving out as flash. © 2019, © 2019 Institute of Materials, Minerals and Mining. Published by Taylor & Francis on behalf of the Institute.

Science and Technology of Welding and Joining

Material flow during friction hydro-pillar processing

Stationary shoulder friction stir welding (SSFSW) is a new variant of the conventional FSW with rotation of only the tool probe to reduce the rate of heat generation along the tool–workpiece interface and hence, weld joint residual stresses. Studies on the evolution of residual stresses in SSFSW are rare as the process is new. A detailed investigation on the evolution of welding-induced residual stress is reported here for SSFSW and the conventional FSW of four different aluminum alloys. A finite element method–based numerical model, JWRIAN-Hybrid, is used for the three-dimensional heat transfer and thermo-mechanical stress analyses. The computed results are validated extensively with the corresponding experimentally measured results. The results show approximately 10% to 20% reduction in the peak residual stresses in SSFSW under identical welding conditions. © 2019, Springer-Verlag London Ltd., part of Springer Nature.

Probing residual stresses in stationary shoulder friction stir welding process

The rate of heat generation and plastic deformation of materials should be precisely controlled in order to get a strong and sound weld joint during dissimilar friction stir lap welding (FSLW) of aluminium and steel. The effect interfacial microstructure at the weld joint interface on mechanical properties is elucidated in the present investigation with the help of detailed microstructure evaluation in FSLW of AA6061 and mild steel (MS). The results indicated a substantial variation in interfacial structure from formation of a bi-metallic straight interface, intercalated structure to mechanically mixed zone (MMZ) with the increase in tool rotation speed from 300 rpm to 1700 rpm. In addition, significant differences in the microstructure evolution mechanisms were noticed from the AA6061 side to MS side through the interfacial microstructure. The variation in interfacial structure and corresponding change in the fracture location predominantly affected the mechanical properties of the joints at different tool rotation speeds. The fracture locations in MMZ and intercalated structure showed the highest and lowest lap shear strengths, respectively. © 2020 Elsevier Inc.

Materials Characterization

Elucidation of interfacial microstructure and properties in friction stir lap welding of aluminium alloy and mild steel

Girth friction welding is a novel technique to join co-axial linepipes with an external ring (girth) in solid state and without melting of materials. The ring or the girth is rotated between two pipes under an axial force resulting in frictional heat generation and plastic deformation along the pipe-girth interfaces. The rotation of the girth is stopped after a preset displacement of the pipes while the force is maintained to consolidate the deformed material and form the joint along the girth-pipe interfaces. Since the girth is only rotated and the pipeline sections remain stationary, the process simplifies the in situ assembly operations and enables the joining of complex configurations. As the melting of pipes and girth is avoided, the formation of harmful intermetallic compounds and deterioration of toughness in the heat affected zone are minimized. A comprehensive numerical model is reported in the present work to analyse the influence of key process variables on the rate of heat generation, resulting temperature field and thermal cycles, and the nature of material flow along the pipe-girth interfaces in girth friction welding of duplex stainless steel pipes. The computed results of thermal cycles and joint shapes are validated with the corresponding experimentally measured results. The results showed a favorable balance of the ferrite and austenite phases, and very little presence of the harmful sigma phases in the recrystallized weld-zone, which is difficult in fusion welding processes of similar materials. © 2020

Journal of Manufacturing Processes

An investigation on girth friction welding of duplex stainless steel pipes

Pre-prints of the National Meeting of Japan Welding Society

Assessment of tool wear in friction stir welding of high carbon steel

Preprints of the National Meeting of Japan Welding Society

Modeling of residual stresses in stationary shoulder friction stir welding

The effect of process parameters on temperature distribution in stationary shoulder friction stir welding (SSFSW) and conventional FSW of AA7010-T6 alloy are studied using a three-dimensional heat conduction analysis. The computed results are validated from experimentally measured results reported in independent literature. The tool torque, traverse force and the mechanical stresses on the FSW tool were evaluated analytically using mechanics based principles. The estimated results showed that the tools used in the SSFSW process were more likely to early failure. © 2019, The Minerals, Metals & Materials Society.

Minerals, Metals and Materials Series

Probing Tool Durability in Stationary Shoulder Friction Stir Welding

Effect of plate thickness on tool life in FSW of high strength aluminum alloy

A coupled experimental and theoretical study is reported here on friction hydro-pillar processing of AISI 4140 steel, which is a novel solid-state joining technique to repair and fill crack holes in thick-walled components by an external stud. The stud is rotated and forced to fill a crack hole by plastic flow. During the process, frictional heating occurs along the interface of the stud and the wall of crack hole leading to thermal softening of the stud that eases its plastic deformation. The effect of the stud force, its rotational speed and the total processing time on the rate of heat generation and resulting transient temperature field is therefore examined to correlate the processing variables with the joint structure and properties in a systematic and quantitative manner, which is currently scarce in the published literature. The results show that a gentler stud force rate and greater processing time can promote proper filling of the crack hole and facilitate a defect-free joint between the stud and original component. © The Minerals, Metals & Materials Society and ASM International 2018.

Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science

Friction hydro-pillar processing of a high carbon steel: Joint structure and properties

A coupled theoretical and experimental study was undertaken to examine the impact of plate thickness, alloy strength and processing conditions on the susceptibility of tool failure in friction stir welding of AA7075 and AA7039. A three-dimensional steady-state heat transfer model was used to compute the temperature field in tool and workpiece alloy. The torque and traverse force, and the mechanical stresses on the tool were estimated analytically and validated with the corresponding experimentally measured results for a range of processing conditions. The propensity of the tool to failure was assessed by a durability factor, which was estimated as a ratio of tool material strength at the computed peak temperature and the resultant mechanical stress on the tool probe. The results showed that rise in welding speed, alloy strength and plate thickness could lead to increased mechanical stresses on tool probe, reduced durability factor and enhanced susceptibility of tool failure. The overall methodology was used successfully to provide the underlying basis for two reported practical examples of tool failures in friction stir welding. © 2016 Elsevier B.V.

Journal of Materials Processing Technology

Probing torque, traverse force and tool durability in friction stir welding of aluminum alloys

Friction hydro pillar processing (FHPP) is a novel technique to fill in crack-holes in thick-walled metal structures by an external stud and forming a solid-state bond between the stud and the metal substrate. During the process, the stud is rotated against the crack-wall to facilitate friction heating and flow of plasticized material for proper filling of the crack-hole. We present here a coupled experimental and numerical study on FHPP of ASTM A36 steel to understand the effect of processing conditions on the joint structure and properties. An axi-symmetric heat transfer analysis is carried out to compute the temperature field. The computed thermal cycles are used to estimate the hardness distribution across the joint. The estimated thermal cycles and hardness distribution are tested with the corresponding experimentally measured results. © 2017 Institute of Materials, Minerals and Mining. Published by Taylor & Francis on behalf of the Institute.

An investigation on friction hydro-pillar processing

Al-Zn-Mg alloys are widely used as structural materials due to high strength-to-weight ratio and impact toughness. As fusion welds in these alloys commonly face hot cracking and macro porosity, friction stir welding is increasingly becoming the preferred recourse. We report here a detailed experimental study on friction stir welding of a specific Al-Zn-Mg alloy with its chemical compositions close to AA7039. The effect of tool rotational speed and welding speed on the weld profile, joint microstructure, and mechanical properties is studied extensively. The results show sound weld profiles and joint properties within the selected range of process conditions. Within the selected range of welding conditions, the welds made at a tool rotational speed of 350 rpm and welding speed of 3 mm/s have showed joint structure, tensile, and impact toughness properties fairly close to that of the base material. © 2016, ASM International.