Olatunji P. Abolusoro

Bio: Olatunji P. Abolusoro is an academic researcher from University of Johannesburg. The author has contributed to research in topics: Friction stir welding & Welding. The author has an hindex of 3, co-authored 12 publications receiving 35 citations.

Tool rotational speed impact on temperature variations, mechanical properties and microstructure of friction stir welding of dissimilar high-strength aluminium alloys

Abstract: Temperature variations during friction stir welding result from the heat generated by the frictional action of a rotating tool on the workpiece. This temperature distribution affects the mechanical behaviour and ultimately the quality of welds produced. The study of the correlations between process parameter, temperature, mechanical properties and microstructure has become imperative in order to promote welds devoid of defects and possessing sound mechanical properties and to establish a temperature feedback control for effective components designs for industrial applications. This work studied the impact of tool rotational speed on temperature profile, mechanical behaviour and microstructure of friction stir welding of dissimilar aluminium alloy 6101-T6 and 7075-T651. Processing parameters of three different rotational speeds with values 1250 rpm, 1550 rpm and 1850 rpm and a constant travel speed of 50 mm/min were employed. The temperature profile was measured with one end of thermocouple wires embedded in the plates and the other end connected to a data capturing software device. The temperature profile indicates that the temperature rises with time and is higher at the retreating sides than at the advancing side of the weld. The tensile test results show that the ultimate tensile strength decreases as the temperature increases. Microstructural observations of weld zone revealed non-uniformity in material flow. However, more material penetration into each other occurred more at 1550 rpm.

Mechanical and microstructural evaluation of aluminium matrix composite reinforced with wood particles

Abstract: Aluminium-wood particle composites were formed by casting method. Different weight fractions of wood particle as reinforcement to the Aluminium alloys were used to produce the composites. The physical and mechanical properties such as density, impact strength, tensile strength, hardness and microstructure were investigated. The results showed that the density decreases with the percentage increase in reinforcement. Also, a significant enhancement in the ultimate tensile strength (UTS) of the composite compared to that of pure aluminium was achieved. The maximum UTS of the Aluminium -wood composite is 97.69 MPa and occurred at 20%wt wood particulate addition reinforcement while that of the unreinforced Aluminium is 40.189 MPa. The impact energy varies from 47.00 J to 89.00 J with a maximum value at 10%wt wood particulate addition while the hardness varies from 52.33BHN to 62BHN with a maximum value at 10%wt. All the mechanical behaviours investigated in the study generally showed that the Aluminium -wood composite exhibited better mechanical properties than the pure Aluminium. The microstructure examination revealed that the wood particles were uniformly distributed in the metal matrix composite.

Effects of processing parameters on mechanical, material flow and wear behaviour of friction stir welded 6101-T6 and 7075-T651 aluminium alloys

Abstract: Dissimilar friction stir welding (FSW) between 6101-T6 and 7075-T651 aluminium alloys was conducted. Three different parameters each were investigated for rotational speed and travel speed, and the effects of these parameters on the tensile behaviour, hardness and wear were evaluated. The results indicate that the ultimate tensile strength increases with an increase in the feed rate. However, the increase in rotational speed decreases the ultimate tensile values. The fractured analysis of the tensile samples shows similarities in the fractured pattern as all the samples failed at heat affected zone close to the 6101-T6 alloy. The hardness varies across the heat affected zones and nugget zone both at constant rotational speed and welding speeds. The highest resistance to wear occurred at 65 mm min−1 and 1850 rpm welding speed and rotational speed respectively while better material mixing was achieved at the nugget zone of the welds at 1250 rpm and 110 mm/min.

In-Process Cooling in Friction Stir Welding of Aluminium Alloys—An Overview

Abstract: Friction stir welding (FSW) is a welding technique that has found extensive use in the joining of aluminium alloys for many applications. During FSW welding, severe plastic deformation occurs due to the stirring actions of the tool which generates heat on the workpiece. The thermal cycle set up at the weld region causes deterioration of precipitates by coarsening or dissolutions. The resultant mechanical properties of the weld region, therefore, become lesser than that of the base metal. Efforts have been made by various researchers to address this challenge through in-process cooling using different cooling fluids such as cryogenic, slush ice, water, compressed air and liquified nitrogen to control the temperature during FSW so as to enhance the mechanical behavior of the welds. The in-process cooling approach was generally reported to have improved the mechanical and corrosion behavior of welded joints as a result of fine and stable microstructures obtained at the weld zone. This paper reviewed the research efforts in this direction. The authors and their investigations and findings have been briefly summarized and the influence of these cooling media on tensile, microstructures and corrosion behavior has been highlighted. The overall aim of this review paper is to provide comprehensive requisite knowledge of the current state of research on in-process cooling in FSW of aluminium alloys with a view to exposing further areas of research interest in this aspect of FSW.

Electrochemical methods in tribocorrosion: a critical appraisal

Abstract: Tribocorrosion is an irreversible transformation of a material resulting from simultaneous physico-chemical and mechanical surface interactions in a tribological contact. Electrochemical methods are well suited for the study of tribocorrosion phenomena because they allow one to simulate the corrosive effect of the environment by imposing a fixed potential. Furthermore, the measurement of the anodic current permits one to determine the amount of material removed by oxidation as opposed to mechanical wear. In the present paper, experimental and theoretical aspects of applying electrochemical methods in tribology are discussed and recent results obtained with passivating metals in the authors' laboratory are presented. The importance of controlling the mechanical parameters and the contact geometry is stressed, and it is shown that these parameters can significantly affect the electrochemical response of a tribocorrosion system.

Advanced Welding Manufacturing: A Brief Analysis and Review of Challenges and Solutions

Abstract: Welding is a major manufacturing process that joins two or more pieces of materials together through heating/mixing them followed by cooling/solidification. The goal of welding manufacturing is to join materials together to meet service requirements at lowest costs. Advanced welding manufacturing is to use scientific methods to realize this goal. This paper views advanced welding manufacturing as a three step approach: (1) pre-design that selects process and joint design based on available processes (properties, capabilities, and costs); (2) design that uses models to predict the result from a given set of welding parameters and minimizes a cost function for optimizing the welding parameters; and (3) real-time sensing and control that overcome the deviations of welding conditions from their nominal ones used in optimizing the welding parameters by adjusting the welding parameters based on such real-time sensing and feedback control. The paper analyzes how these three steps depend on process properties/capabilities, process innovations, predictive models, numerical models for fluid dynamics, numerical models for structures, real-time sensing, and dynamic control. The paper also identifies the challenges in obtaining ideal solutions and reviews/analyzes the existing efforts toward better solutions. Special attention and analysis have been given to (1) gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) as benchmark processes for penetration and materials filling; (2) keyhole plasma arc welding (PAW), keyhole-tungsten inert gas (K-TIG), and keyhole laser welding as improved/capable penetrative processes; (3) friction stir welding (FSW) as a special penetrative low heat input process; (4) alternating current (AC) GMAW and double-electrode GMAW as improved materials filling processes; (5) efforts in numerical modeling for fluid dynamics; (6) efforts in numerical modeling for structures; (7) challenges and efforts in seam tracking and weld pool monitoring; (8) challenges and efforts in monitoring of keyhole laser welding and FSW; and (9) efforts in advanced sensing, data fusion/sensor fusion, and process control using machine learning/deep learning, model predictive control (MPC), and adaptive control.

Tool rotational speed impact on temperature variations, mechanical properties and microstructure of friction stir welding of dissimilar high-strength aluminium alloys

Abstract: Temperature variations during friction stir welding result from the heat generated by the frictional action of a rotating tool on the workpiece. This temperature distribution affects the mechanical behaviour and ultimately the quality of welds produced. The study of the correlations between process parameter, temperature, mechanical properties and microstructure has become imperative in order to promote welds devoid of defects and possessing sound mechanical properties and to establish a temperature feedback control for effective components designs for industrial applications. This work studied the impact of tool rotational speed on temperature profile, mechanical behaviour and microstructure of friction stir welding of dissimilar aluminium alloy 6101-T6 and 7075-T651. Processing parameters of three different rotational speeds with values 1250 rpm, 1550 rpm and 1850 rpm and a constant travel speed of 50 mm/min were employed. The temperature profile was measured with one end of thermocouple wires embedded in the plates and the other end connected to a data capturing software device. The temperature profile indicates that the temperature rises with time and is higher at the retreating sides than at the advancing side of the weld. The tensile test results show that the ultimate tensile strength decreases as the temperature increases. Microstructural observations of weld zone revealed non-uniformity in material flow. However, more material penetration into each other occurred more at 1550 rpm.

Friction Stir Welding of Dissimilar Metal: A Review

Abstract: Friction Stir Welding (FSW) is a solid-state welding process which produces welds due to the compressive force contact of work pieces which are either rotating or moving relative to each other. The heat required to join different specimens is generated by heating due to friction at the interface. Application of Friction Stir Welding in aerospace industries is very broad. Rolls-Royce now uses friction welding processes for its modern Trent aero engines that drive the Airbus A380 and the Boeing 787. In this paper, Friction Stir Welding of various dissimilar metals is reviewed. The microstructure, hardness, and flow characteristics are also reviewed.