Mohd Ridha Muhamad

Bio: Mohd Ridha Muhamad is an academic researcher from University of Malaya. The author has contributed to research in topics: Welding & Friction stir welding. The author has an hindex of 5, co-authored 14 publications receiving 110 citations.

Effect of Surface States on Joining Mechanisms and Mechanical Properties of Aluminum Alloy (A5052) and Polyethylene Terephthalate (PET) by Dissimilar Friction Spot Welding

Abstract: In this research, polyethylene terephthalate (PET), as a high-density thermoplastic sheet, and Aluminum A5052, as a metal with seven distinct surface roughnesses, were joined by friction spot welding (FSW). The effect of A5052’s various surface states on the welding joining mechanism and mechanical properties were investigated. Friction spot welding was successfully applied for the dissimilar joining of PET thermoplastics and aluminum alloy A5052. During FSW, the PET near the joining interface softened, partially melted and adhered to the A5052 joining surface. The melted PET evaporated to form bubbles near the joining interface and cooled, forming hollows. The bubbles have two opposite effects: its presence at the joining interface prevent PET from contacting with A5052, while bubbles or hollows are crack origins that induce crack paths which degrade the joining strength. On the other hand, the bubbles’ flow pushed the softened PET into irregularities on the roughened surface to form mechanical interlocking, which significantly improved the strength. The tensile-shear failure load for an as-received surface (0.31 μ m Ra) specimen was about 0.4–0.8 kN while that for the treated surface (>0.31 μ m Ra) specimen was about 4.8–5.2 kN.

Autogenous double-sided T-joint welding on aluminum alloys using low power fiber laser

Abstract: In this study, a successive double sided laser beam welding process was used to join dissimilar aluminum alloys, AA2024-O and AA7075-T6 using a low power Yb-fiber laser in a T-joint configuration without additions of filler materials. The influence of welding speeds and focal distances were evaluated. First, the welding speeds were varied from 12 mm/s to 21 mm/s at a constant laser power of 270W. Optical microscopic observations have shown that the minimum gap line of 0.8mm was obtained at a laser welding speed of 12mm/s, while the maximum gap line of 1.8mm was obtained at a laser welding speed of 21mm/s. The focal distance with offsets of -1, 0 and +1 at welding speed 18mm/s were evaluated, showing variations in the gap line. Vickers microhardness evaluation across the welding region showed the hardness values at the fusion and heat affected zones were lower than those of the base metals when welding speed varied. Meanwhile, the Vickers microhardness increases when focal distance is defocused +1. The pull test showed the force needed to fracture the welded specimens increased from 101N to 427N as the welding speed decreased from 21mm/s to 12mm/s. For constant welding speed and laser power, the fracture force increased from 100N to 400N as the focal distance changes from -1 to +1. It was observed that a lower welding speed and positive offset value of focal distance will result in deeper penetration, leading to better weld quality between alloys AA2xxx and AA7xxx.

A review on nanomaterials reinforcement in friction stir welding

Abstract: Nanomaterial reinforced friction stir welding (FSW) is an emerging domain, as it delivers a promising method for enhancing joint properties by making composite joints. Composite joints can enhance surface properties like hardness, strength, corrosion resistance, wear resistance, fatigue life, electrical conductance. Over few years many publications have been reported on the application of nanoparticles reinforcement in FSW joints. The present review critically analyses the current status of nanoparticle reinforcement FSW process. Firstly need, type, behaviour, intrinsic properties of nanoparticles used in FSW are discussed. Then, the microstructural examinations of reinforced joints are analysed. Followed by, various properties associated with reinforced joints are presented with the mechanism of the relationship between microstructure and properties. Finally, various methods of deposition of nanoparticle in FSW is discussed. At last prospects of reinforced FSW are explored followed by concluding remarks.

A brief review study of flow phenomena over a backward-facing step and its optimization

Abstract: The flows of fluid via sudden expansions are among the basic topics within the discipline of fluid mechanics. The comprehension of these types of flows has attracted a great volume of research, attributable to their wide usage in numerous fluid applications such as heat exchangers, dump combustors, nuclear reactors and diffusers; as well as pipe-flow systems within the chemical and petroleum industries, pharmaceutical, medical science, air-conditioning ducts, and fluidic devices. Many researchers have conducted a great deal of empirical and numerical studies in this discipline. Survey works existing in this discipline are lacking. A bibliographical survey of the flow via sudden expansion is presented in this work along with the critical analysis of the published empirical and numerical research in the specified field. In this review, flow specifications for several kinds of fluids, conditions of flow, conduit geometrical parameters, plain and modified abrupt enlargement configurations, as well as further related factors are discussed. The primary purpose here is to provide a summary of the recent research progress on the flow specifications of fluid flowing via abrupt enlargement configurations in order to suggest several potential explanations about implementation of these configurations in industrial applications.

Recent research progress in friction stir welding of aluminium and copper dissimilar joint: a review

Abstract: Aluminium and copper are employed in various industrial applications due to their high plasticity, thermal conductivity, electrical conductivity and characteristics. By effectively joining dissimilar aluminium and copper, the unique properties of composite formed by these metals can be adequately addressed. Friction stir welding (FSW), an energy-efficient solid-state welding process is capable of joining dissimilar metals, has enormous potential in the future of various industries. This present work comprehensively summarises all pertinent topics related to aluminium to copper FSW, such as FSW process parameters, microstructural characterisation, mechanical properties, and electrical characteristics of aluminium–copper joints produced by FSW. In addition, the current report also discusses several applications of additives used in dissimilar FSW of Al–Cu and new FSW techniques, which generally aim to enhance Al–Cu joint properties. Moreover, numerical modelling of Al–Cu FSW is discussed profoundly to understand the effects of alterations in different process parameters on temperature gradients and microstructure evolution, which would be time-consuming or prohibitively expensive in practice by physical testing. Additionally, several recommendations for future research are proposed to facilitate the advancement and success of Al–Cu FSW studies.

Handbook Of Modern Sensors Physics Designs And Applications

Abstract: Thank you for reading handbook of modern sensors physics designs and applications. As you may know, people have search hundreds times for their chosen readings like this handbook of modern sensors physics designs and applications, but end up in infectious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they juggled with some malicious bugs inside their laptop.

Friction stir welding/processing of polymers and polymer matrix composites

Abstract: Friction stir welding/processing (FSW/P) involving temperature, mechanics, metallurgy and interaction, is a complex solid state joining and processing technology. FSW has been widely applied to join aluminum alloy, titanium alloy and other materials which are difficult to weld by fusion welding. The last scientific study states that FSW has potential to join thermoplastic polymers and polymer matrix composites. In this review, current understanding and development about FSW of thermoplastic polymers and polymer matrix composites, multifunctional composites fabrication as well as dissimilar FSW of metal and polymer are reviewed. Future scientific research and engineering development related to FSW/P of thermoplastic polymers and polymer matrix composites are identified.

Numerical study on mixed convection of a non-Newtonian nanofluid with porous media in a two lid-driven square cavity

Abstract: In the present numerical study, mixed flow of the non-Newtonian water/Al2O3 nanofluid with 0–4% nanoparticles volume fractions (φ) inside a two-dimensional square cavity with hot and cold lid-driven motion and porous media is simulated at Richardson numbers (Ri) of 0.01, 10 and 100 and Darcy numbers (Da) of 10−4 ≤ Da ≤ 10−2 using Fortran computer code. The obtained results for temperature domain, velocity, Nusselt number and streamlines indicate that by increasing Richardson number and decreasing axial velocity parameter of walls and similarity of flow behavior to natural flow mechanism, variations of velocity are reduced, which is due to the reduction in fluid momentum. By increasing Darcy number, penetrability of fluid motion enhances and fluid lightly moves along the cavity. Figuration of streamlines at lower Richardson numbers highly depends on the Darcy number changes. In case (2), due to the counterflow motion and buoyancy force, distinction of flow domain profiles is more obvious. On the other hand, this issue causes more velocity gradients and vortexes in special sections of cavity (central regions of cavity). In case (2), the behavior of streamlines is affected by some parameters such as variations of Darcy number, nanoparticles volume fraction and Richardson number more than case (1). By increasing Darcy number, flow lightly passes among hot and cold sources and leads to improve the heat transfer. Moreover, reduction in flow penetrability in cavity results in the reduction in fluid flow in its direction, sectional distribution and regions with higher temperature. Consequently, in these regions the growth of thermal boundary layer is more significant. In case (2), at lower Richardson numbers compared to higher ones, the affectability of lid-driven motion contrary to buoyancy force caused by density variations is less because of higher fluid momentum. At Ri = 0.01, because of the strength of lid-driven motion, flow direction is compatible with lid-driven motion. Also, temperature distribution is not uniform, and in these regions, fluid has the minimum velocity which leads to the enhancement of dimensionless temperature. In both studied cases, the increment of nanoparticles volume fraction as well as Darcy number and reduction in Richardson number result in the improvement of temperature distribution and decrease in dimensionless temperature.