Endri Rachman

Bio: Endri Rachman is an academic researcher from Universiti Sains Malaysia. The author has contributed to research in topics: Friction welding & Heat-affected zone. The author has an hindex of 4, co-authored 5 publications receiving 118 citations. Previous affiliations of Endri Rachman include Universiti Sains Malaysia Engineering Campus.

Mechanical evaluation and thermal modelling of friction welding of mild steel and aluminium

Abstract: In friction welding of two dissimilar materials, two rods are welded together by holding one of them still while rotating the other under the influence of an axial load which creates frictional heat in the interface. In this study, mechanical properties of mild steel and aluminium welded rods were evaluated to understand the thermal effects, and an explicit one-dimensional finite difference method was used to approximate the heating and cooling temperature distribution of the joint. The thermal effects of the friction welding were observed to have lowered the welded materials hardness compared to the parent materials. The tensile strength of the welded rods is lower than the parent rods due to incomplete welding. The preliminary predictions were compared to actual thermocouple data from welds conducted under identical conditions and were shown to be in fair agreement. The finite difference method proposed in this work will provide guidance in weld parameter development and will allow better understanding of the friction welding process.

Evaluation of properties and FEM Model of the Friction welded mild Steel-Al6061-Alumina

Abstract: Evaluation of mechanical and interfacial properties of friction welded alumina-mild steel rods with the use of Al6061 sheet are presented in this work. SEM, EDX analysis, hardness and bending strength tests were conducted. The bonds were attained through interfacial interlocking and intermetalllic phase formation with average bending strengths in the range of 40 to 200 MPa and insignificant hardness change in the parent alumina and mild steel. A preliminary simulation was made to predict the deformation, stress, strain and temperature distribution during the joining operation using a fully coupled thermo-mechanical FE model. The aluminum alloy metal being rubbed was simulated using a phenomenological Johnson-Cook viscoplasticity material model, which suited for materials subjected to large strains, high strain rates and high temperatures. The highest stress, strain and deformation are found to be within the heat affected zone of the weld close to the periphery rubbing surface region and correspond to the highest temperature profiles observed.

Characterization and thermal modelling of friction welded alumina–mild steel with the use of Al 1100 interlayer

Abstract: This paper reports a study of the physical and thermal behaviors of friction welded alumina–mild steel rods with the use of AL 1100 sheet as interlayer. A series of hardness tests, bending tests, macrostructure observations, SEM and EDX analyses were carried out and were combined with a finite difference thermal model to acquire material parameters. This work demonstrated the insignificant change in the hardness value of the parent alumina and the slight increase in hardness value of the parent mild steel, particularly near the interface region. The bending strength increased with the increase of friction times with the highest bending strength obtained was 186 MPa at 20 s. The fractured surface shows the strong bond at the middle of the interface. The bond was obtained through interfacial interlocking and narrow intermetallic phase formation. However, the incomplete joint observed was detrimental to the joint strength. The thermal profile predictions were compared to actual thermocouple data from welds conducted under identical conditions and were shown to be in fair agreement. Even though the FD method proposed in this study cannot replace a more accurate numerical analysis, it does provide guidance in weld parameter development and allows better understanding of the friction welding process.

A mathematical modeling for design and development of control laws for unmanned aerial vehicle (uav)

Abstract: Flight Mechanics and Control Laboratory of School of Aerospace Engineering -USM has been designing and developing an unmanned aerial vehicle since year 2003. The temporary result of this effort is a remotely piloted vehicle (RPV) that is controlled by radio control on the ground. In order to convert the RPV to be an unmanned aerial vehicle (UAV) that can performs the autonomous aerial surveillance and reconnaissance missions for civilian purposes, the autonomous control laws/algorithms, like damper, attitude hold/select, altitude hold/select, auto-throttle, coordinated turn and waypoints following, have been designed, and developed. This paper will discuss the step by step procedure in the design and development of the control laws of UAV starting from determination of stability/control derivatives, setting up the non-linear flight model/equation of motion, trim determination, flight dynamics analysis, designing the control laws and gain scheduling development, and the simulation of control laws in form all software simulation, the hardware in the loop simulation (HILS) and the Iron-bird simulation before doing the flight testing.

Temperature Modeling for Friction Welding Process between Ceramic and Metal

Abstract: Numerical model of friction welding between ceramic and metal rods are established to predict temperature rises during the initial phase of the process. In this study alumina(ceramic) and mild steel(metal) rods are used and joined with aluminium sacrificial interlayer. The workpieces are welded together by holding alumina still, while rotating the steel attached with aluminium piece under influence of an axial load which creates frictional heat in the interfaces. The transient thermal response in welding is hard to model analytically. Generally, heat is dissipated over time scales of less than two seconds. For the thermal model, an explicit one dimensional (1-D) finite difference (FD) method is utilized to approximate the heating and cooling temperature distribution of the joined dissimilar rods. The preliminary predictions are compared to actual thermocouple data from welds conducted under identical conditions and are shown to be in fair agreement. Even though the FD method proposed in this study cannot replace a more accurate numerical analysis, it does provide guidance in weld parameter development and allows better understanding of the friction welding process.

Joining of dissimilar materials

Abstract: Emerging trends in manufacturing such as light weighting, increased performance and functionality increases the use of multi-material, hybrid structures and thus the need for joining of dissimilar materials. The properties of the different materials are jointly utilised to achieve product performance. The joining processes can, on the other hand be challenging due to the same different properties. This paper reviews and summarizes state of the art research in joining dissimilar materials. Current and emerging joining technologies are reviewed according to the mechanisms of joint formation, i.e.; mechanical, chemical, thermal, or hybrid processes. Methods for process selection are described and future challenges for research on joining dissimilar materials are summarized.

Properties of Friction Welding Titanium-stainless Steel Joints with a Nickel Interlayer

Abstract: The probability and appropriate processing parameters of friction welding method of commercially pure titanium to a 304L stainless steel with an electroplated nickel interlayer have been investigated. The microstructure of the welded joints has been observed by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, and the main factors affecting friction welding process were analysed. Metallographic analysis revealed that a good bonding was obtained at both the titanium/nickel and nickel/stainless steel interfaces, and the diffusion products were identified in the weld zone. The effect of friction time and forging pressure on metallurgical and mechanical properties were evaluated. The results showed that atom diffused well and no presence of Fe–Ti intermetallic compounds appeared at optimum parameters. With the increment of friction time, the thermal degradation region increasing hence the thickness of interlayer material is decreasing. Microhardness test across the joining interfaces demonstrated the effect of solid solution hardening in the weld zone. The tensile strength increased with increasing forging pressure at constant friction time. Tensile test showed that the maximum average tensile strength of ∼289 MPa was obtained for the joint welded at forging pressure of 320 MPa. The tensile fracture surfaces are indicating river patterns of brittle mode of failure of the joints. The tensile fracture of the welded joint occurred in titanium side near the interface.

Effects of resistance spot welding parameters on microstructures and mechanical properties of dissimilar material joints of galvanised high strength steel and aluminium alloy

Abstract: Intermediate frequency resistance spot welding has been adopted to join dissimilar materials of H220YD galvanised high strength steel and 6008 aluminium alloy. The effects of welding current and welding time on microstructures and mechanical properties of the welded joints were investigated. A thin intermetallic compound layer composed of Fe2Al5 phase and Fe4Al13 phase formed at the steel/aluminium interface. The interfacial intermetallic compound layer has higher nanohardness compared with the aluminium alloy nugget and galvanised steel. With increasing welding current (4–11 kA) and welding time (50–300 ms), the nugget diameter increased, the interfacial layer structure became coarser and the tensile shear load of the welded joints had an increased tendency. The maximum tensile shear load reached 3309 N at 9 kA for 250 ms. Crack initiated at the interfacial intermetallic compound layer of the tensile shear specimens, then propagated through the interfacial layer principally, and meantime through the alum...

Mechanical property and microstructure of aluminum alloy-steel tubes joint by magnetic pulse welding

Abstract: The mechanical properties, microstructure and interface pattern of lapped joint of AA3003-O and steel 20 tubes by magnetic pulse welding (MPW) were investigated. The results show that the tension and torsion strength values are higher than that of the aluminum tube when the discharge voltage of MPW process is not less than 8 kV. The metallurgical joint, which composes of interfaces, non-uniform transition zone and basic metals, are obtained under discharge voltage of 15 kV, the preset oblique angle of 4° and radial gap of 1.2–1.4 mm. High-density dislocations and nanocrystals present in basic metals along the interfaces. The transition zone has the highest micro-hardness of 5.1 GPa. The multi-direction micro-cracks and the micro-apertures characterize the transition zone of MPW joint. The mutual diffusion of Fe and Al elements occurs in the transition zone, where content of Al element is higher than Fe element besides a narrow region close to the interface of steel and zone. The narrower transition zone presents more even distribution of basic elements than the wider one.

Mechanical Property and Microstructure of Linear Friction Welded WASPALOY

Abstract: The mechanical properties and microstructural evolution of WASPALOY joined by linear friction welding (LFW) were investigated in this study. In-situ temperature measurements using thermocouple probes indicated exposure of the weld area to a temperature of at least 1400 K (1126 °C). Based on electron backscatter diffraction (EBSD) mapping of the weldments, up to 50 pct reduction in γ grain size occurred within 0.9 mm of the weld interface as a result of dynamic recrystallization (DRX). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed that progressive dissolution of γ′ precipitates took place from the base metal to the weld interface, where almost no γ′ precipitates were observed. Within 3.3 mm of the weld interface, the γ′ dissolution significantly influenced the hardness profile measured across the extended thermomechanically affected zones (TMAZs). Investigation of strain distributions during tensile testing using the optical Aramis system revealed weak bonding at the edge of the weld due to oxidation. To extrude out oxide layers into the flash, increasing the axial shortening to higher than 1.2 mm is recommended.