Ahmad Majdi Abdul Rani

Prototype production and experimental analysis for circular and profiled conformal cooling channels in aluminium filled epoxy injection mould tools

Purpose – The purpose of this paper is to present a technique of fabricating profiled conformal cooling channels (PCCC) in an aluminium filled epoxy mould using rapid prototyping (RP) and rapid tooling (RT) techniques and to compare the cooling times for the moulds with circular and profiled channels experimentally. The cooling channels in injection mould tools have a circular cross section. In a PCCC, the cross sectional shape is so designed that the flat face surface of the channel facing the cavity follows the profile of the cavity. These types of channels can be manufactured through RP and RT techniques.Design/methodology/approach – A part to be moulded was designed and modelled. Two moulds were then designed with the part cavity, one having a circular channel and the second with a profiled channel, both having the same cross sectional area for coolant flow. The channel patterns were designed with supports according to their position regarding height and distance from the cavity as designed earlier. B...

Analysis of Journal Bearing with Double-Layer Porous Lubricant Film: Influence of Surface Porous Layer Configuration

This article presents an analysis of a long journal bearing with a double-layer porous lubricant film using couple stress and Newtonian fluids. The porous layer with infinite permeability analyzed in this study simulates the surface layer. The Brinkman model was utilized to model the flow in the porous region. The effects of couple stresses were analyzed based on Stokes microcontinuum theory. A double-layer porous lubricant film configuration, with a low-permeability porous layer on top of a high-permeability bearing adherent porous layer, improved the journal bearing performance characteristics. A surface porous layered lubricant film configuration increased the load-carrying capacity and reduced the coefficient of friction in a journal bearing.

Novel Nano Copper-Tungsten-Based EDM Electrode

Using electrical discharge machining (EDM), it is possible to machine material that is difficult to machine by conventional machining technique as long as it is electrically conductive. The performance of EDM is highly dependent on the type of electrode being used, the power supply system, and the dielectric system. Copper–tungsten electrode combines the higher melting point of tungsten with the good electrical and thermal conductivity of copper, but it is difficult to manufacture due to the variation in melting point and zero miscibility of copper with tungsten. Thus, newly modified copper–tungsten–silicon (Cu–WC–Si) electrode was synthesized using ball milling method. The method was used to synthesize the new electrode material due to the possibility to overcome the problems encountered in alloying materials which have a large variation in melting temperature or low miscibility at low temperatures. Taguchi method is the main statistical tool used to design and analyse ball milling and machining processes. Material removal rate and electrode wear are the parameters used for comparing the performance between the existing copper–tungsten and new developed electrode. Milling results show a clear change in the thickness of crystalline and d-spacing of the milled powder. The performances of Cu–WC–Si electrode in machining of hardened die steel show an improvement in MRR and EW compared with that achieved by using Cu–W electrode when it is milled for less than 10 h.

Stability evaluation of three-layered journal bearing with slip/partial slip

Purpose This paper aims to present stability of a three-layered journal bearing considering magnitude of the layers’ thicknesses and viscosities with slip/partial slip on the bearing surface. Design/methodology/approach Modified Reynolds equation based on one-dimensional analysis is derived for a three-layered journal bearing with slip/partial slip. Dynamic coefficients are derived based on infinitesimal perturbation method. Linearized stability analysis is presented taking into account slip/partial slip on bearing surface; thicknesses and viscosities of bearing surface layer; and core layer and journal surface layer. Findings Results of threshold speed and critical whirl frequency ratio coefficients (Cω, CΩ), stiffness (Kij for i = x,y) and damping (Bij for i = x, y) coefficients and threshold speed (ωs) and critical whirl frequency ratio (Ωs) are presented. The bearing surface is analyzed for slip (total surface with slip) and partial slip (partial surface with slip). The slip-on bearing surface reduces stability, while partial slip improves bearing stability. The threshold speed coefficient (Cω) decreases with slip on bearing surface. The threshold speed (ωs) and critical whirl frequency ratio (Ωs) are influenced by the variation of threshold speed coefficient (Cω) and critical whirl frequency ratio coefficient (CΩ), respectively. A three-layered journal bearing with partial slip and thick high viscosity bearing surface layer results in higher threshold speed coefficient and has a potential to improve stability of journal bearing. The analyses indicate that optimal angular extent of partial slip region (θs) enhances the stability of journal bearing. Originality/value The paper presents parametric study of stability coefficients (Cω and CΩ) and evaluation of threshold speed (ωs) and critical whirl frequency ratio (Ωs) of a three-layered journal bearing with slip/partial slip.

Optimization of bone drilling parameters using Taguchi method based on finite element analysis

Thermal necrosis results fracture problems and implant failure if temperature exceeds 47 °C for one minute during bone drilling. To solve this problem, this work studied a new thermal model by using three drilling parameters: drill diameter, feed rate and spindle speed. Effects of those parameters to heat generation were studied. The drill diameters were 4 mm, 6 mm and 6 mm; the feed rates were 80 mm/min, 100 mm/min and 120 mm/min whereas the spindle speeds were 400 rpm, 500 rpm and 600 rpm then an optimization was done by Taguchi method to which combination parameter can be used to prevent thermal necrosis during bone drilling. The results showed that all the combination of parameters produce confidence results which were below 47 °C and finite element analysis combined with Taguchi method can be used for predicting temperature generation and optimizing bone drilling parameters prior to clinical bone drilling. All of the combination parameters can be used for surgeon to achieve sustainable orthopaedic surgery.

Analysis of Micropolar and Power Law Fluid–Lubricated Slider and Journal Bearing with Partial Slip–Partial Slip Texture Configuration

ABSTRACT An analysis of micropolar and power law fluid–lubricated partial slip–partial slip texture slider and journal bearings is presented. The nondimensional pressure and shear stress expressions for a partial slip texture configuration are analyzed using narrow groove theory. The parameters used in the analysis are nondimensional partial slip length, nondimensional partial slip–partial slip texture length, nondimensional depth of recess, ratio of land with slip to recess, nondimensional slip coefficient, coupling number; ratio of characteristic length to film gap, and power law index. A partial slip configuration with a higher slip coefficient yields an improvement in load capacity and reduction in coefficient of friction compared to a partial slip texture configuration for micropolar and power law shear thinning (pseudoplastic) fluid-lubricated slider and journal bearings.

Stability analysis of double porous and surface porous layer journal bearing

The linear stability analysis of double porous and surface porous layer journal bearing based on long and short bearing approximations is presented. The Brinkman model is employed in the porous region and the infinite permeability porous layer is simulated as surface layer. The coefficients of load, threshold speed and critical whirl frequency ratio are computed for double porous and surface porous layer configurations. The coefficients obtained using long and short bearing approximations yield same results. Higher threshold speed is obtained for double layer configurations of (i) high permeability bearing adsorbent porous layer topped with low permeability porous layer, and (ii) surface porous layer lubricant film.

Analysis of CNT additives in porous layered thin film lubrication with electric double layer

This paper presents an analysis of thin film lubrication of porous layered carbon nanotubes (CNTs) additive slider bearing with electric double layer. The CNTs additive lubricant flow in the thin fluid film and porous layers are governed by Stokes and Brinkman equations respectively, including electro-kinetic force. The apparent viscosity and nondimensional pressure expression are derived. The nondimensional load capacity increases under the influence of electro-viscosity, CNT additives volume fraction, permeability and thickness of porous layer. A CNTs additive lubricated porous thin film slider bearing with electric double layer provides higher load capacity.

Mathematical Modeling for the Prediction of Depth of Penetration in Double Pulse GMA Welding Using Fractional Factorial Method

The quality of weld joint is directly influenced by the input process parameters influenced by various process parameters during welding. The weld quality can be decided by bead geometry viz., depth of penetration and bead width. Inadequate depth of penetration will lead to failure of the welded structure. This paper presents the development of mathematical model for the prediction of depth of penetration of weld bead geometry in pulsed gas metal arc welding process in double pulse mode. The model is based on experimental data .In this investigation four input process parameters wire feed rate, ratio of wire feed rate to travel speed, amplitude and double pulse frequency are considered. The experiments were conducted on 6mm thickness plate of 5083 H111 aluminum alloy using fractional factorial design of experiments. The mathematical model for depth of penetration is developed using multiple nonlinear regression. The developed model is then compared with experimental results and it is found that the results obtained from mathematical model are accurate. The obtained results help in selecting quickly the process parameters to achieve the desired quality.

Analysis of Two-Layered Film Journal Bearing with Partial Slip Surface

Based on the approach of two-layered film consisting of different Newtonian viscosities, the present study examines the effects of partial slip bearing configuration on load capacity and friction coefficient for journal bearing. Navier slip boundary conditions are used to analyze partial slip configuration. A modified Reynolds equation for a journal bearing with two-layered film on a partial slip surface is presented. The modified Reynolds equation is derived taking into consideration of magnitude of lubricant layers film thickness, viscosities and the extent of partial slip on the bearing surface. The Reynolds boundary conditions are used in the analysis to predict nondimensional load capacity and coefficient of friction. Partial slip of bearing surfaces has a potential to improve load carrying capacity and reduce coefficient of friction for two-layered film journal bearing.