Papers by Author: Mariyam Jameelah Ghazali

Abstract: This paper explains about the evaluation of intake air flow, volumetric efficiency and noise of a motor-driven engine that used an adaptive valve lift and timing mechanism (AVLT) on one intake valve. This system is developed with an aim to produce a more powerful engine through variable valve timing and lift technique. The system made the valve lifts higher without increasing the valve lift duration. Therefore, a dynamic valve lift profile with respect to the engine speed can be achieved thus varies the input and output of an engine. As a result of applying the AVLT on a motor-driven engine, the engine noise, emission noise and the mass air flow entering the engine cylinder was increased. When AVLT is employed to a maximum lift, the mass air flow of default intake valve lift was improved within a range from 8% to 46.64% in 500 rpm to 2000 rpm speed range. Maximum lift produced engine noise within a range of 2.57% to 18.13% higher than the default lift throughout all speed. Also, maximum lift produced emission noise within a range of 2.47% to 19.19% higher than the default lift throughout all speed. The product of this research will be useful to optimise the height and timing of the valve lift and the AVLT mountings on the engine head during operation thus improves the engine performance, fuel economy, emission levels and reduced noise of a modified engine.

Abstract: Different techniques have been developed in the area of bearing wear monitoring. This paper proposes a different experimental study on bearing wear monitoring by using an airborne technique. The data captured in the airborne technique will be analyzed by using I-kaz^TM Multi Level (⁷Z) coefficient and then will be correlated with the conventional specific wear rates, K. The wear tests were carried out by using a pin-on-disc configuration at a sliding speed of 7.85 m/s. A set of sliding distance ranging from 20 160 km at a fixed load of 200 N was utilized and the K value was measured at every interval of 20 km for the speed. SAE40 type lubricant was used in the test to simulate the actual operation of the connecting rod bearing. The audio range frequency below 20 kHz in the airborne technique was obtained through a microphone 40SC type which was placed 10 mm from the pin-disc contact. The analysis result showed that the wear rate, K increased from 1.82 to 6.70x10^-8 mm³/Nm as the sliding distance increased, indicating that a mild-abrasion wear regime had occurred. The curve fitting of K as a function of I-kaz^TM Multi Level coefficient showed a similarity to an established of Taylor Tool Life curve. Thus, it was possible to correlate the Taylor curve and worn bearing, mainly in monitoring and identifying the bearing condition with respect to the sliding distance. The trend of I-kaz^TM Multi Level coefficient was found to be consistent with the increase of sliding distance which indicates that the I-kaz^TM Multi Level value can positively be used as wear response indicator for bearing.

Abstract: The stress intensity factor (SIF) under the combined bending and torsion loading were studied using a finite element (FE) analysis ANSYS. A 20-node iso-parametric element was used to model the crack tip and the square-root singularity of stress/strain was employed by shifting the mid-side node to the ¼ position to the crack tip. Different crack geometries and loading ratios were used and due to the non-symmetrical analysis involved, a full FE model was developed and analyzed. Remotely applied bending and torsion moment were subjected to the FE model and the SIF were then calculated along the crack front under such loadings. The SIF calculated using the finite element analysis (FEA) was compared with those results obtained using an effective combined SIF method. According to the comparisons, the discrepancies were dependent on the normalized coordinate, x/h, the relative crack depth, a/D, the crack aspect ratio, a/b and the loading ratio, .

Abstract: Effect of peak-aged and over-aged Cu particles on wear behaviour of ferritic iron was investigated by means of Pin-on-Disc wear test under dry sliding condition. It was found that hardness of the peak-aged sample was higher than the over-aged sample. The specific wear rates of peak-aged samples were in the range of 0.20 × 10-4 to 0.89 × 10-4 mm3/(Nm) while the over-aged samples were in the range of 0.21 × 10-4 to 1.29 × 10-4 mm3/(Nm). Although both samples possessed moderate wear behaviours, the peak-aged samples had better wear resistance. Scanning Electron Microscopy observation found that most wear mechanism were due to plastic ploughing phenomenon. Transferred materials from the counterface tool was also proven by Energy Dispersive Spectroscopy test. However, the roughness test showed that the peak-aged sample surface was finer than the over-aged sample surface. Average roughness of peak-aged samples were in the range of 0.49 to 1.79 μm while the over-aged samples were in the range of 3.28 to 4.02 μm. Hence, it can be concluded that the peak-aged Cu particles can improve the wear resistance of steel.

Abstract: Microstructure and mechanical properties of heat treated Al-Si alloy containing up to 10 wt% aluminum nitride (AlN) particles were investigate. In this work high purity AlN powder with different weight percentage of 0, 5, 7 and 10 were calculated as reinforced material to the metal matrix composites. The Al-Si matrix was prepared by a bottom pour stir casting technique. Heat treatment was performed by soaking and followed by an aged treatment. It was found that the AlN particles were scattered randomly distributed in the matrix composite. Ageing induced Si grain transformation into to spheroid shapes while Al dendrites tend to become finer. Ultimate tensile strength (UTS) had improved drastically from to 125MPa to 306MPa for un-aged Al-Si alloy and aged AlN 7 wt%. Fracture morphologies showed a pronounced feature with small dimples, tear ridges and micro neck particularly in the aged samples leading to a higher tensile value and increase in ductility. The presence of AlN particles in the alloys had improved the tensile strength by slowing down the plastic deformation during tensile test.

Abstract: This paper discusses the effect of several variables in plasma spray method, namely; the flow rate, spray distance and power used on the mechanical properties of Cu-Ni coated A7075. All spraying techniques were designed using 23 factorial plans prior to the actual experiments. The produced coatings were characterised using a scanning electron microscopy (SEM). Morphological observation indicated that most sprayed particles were formed in splash shape splats. The effects of interactions between the response variable factors were screened using a response surface methodology. Three coating factors were used, namely, plasma power, number of coating layer and spraying distance where as the coating hardness and surface roughness were set as the responses. In general, an ideal parameter of 5 coating layers with a power of 30 kW and a spraying distance of 150 mm gave a maximum hardness of 622 Hv and a minimum surface roughness of 9.7 µm.

Abstract: Fatigue in materials is caused by repeated loading and unloading cycles below the ultimate strength of a material. Fatigue tests are expensive since they required a lot of time consuming. Simulation of fatigue crack propagation using commercial software can reduce the costs related to time. The purpose of this study is to compare the fatigue crack propagation in metal under variable and constant amplitude loading. A standard size of aluminum cast alloy specimen according to ASTM E647 document was modelled using a pre-processor and it was later being analysed. In another aspect, strain gauges were attached to an engine mounting bracket and connected to the data acquisition set in order to capture the actual strain signals when an automobile was driven on to different road conditions. For the simulation purpose, a constant amplitude loading was then derived from a variable amplitude loading obtained from the data capturing process. The related parameters on between different road conditions, variable and constant amplitude loadings and crack propagation rate were presented. The relationship between those parameters were finally correlated and discussed.

Abstract: An elastic-plastic finite element analysis (FEA) is used to determine the J-integral around the crack front of 3-dimensional semi-elliptical surface crack in a round bar under torsion loading. Crack geometries are based on the experimental observation. The present model is validated using the SIF under bending loading since no suitable SIF for torsion is available. Lack of numerical solution of elastic and plastic stress parameters under torsion are found. The FE J values are normalized by dividing with the estimation J value using a reference stress method. It is found that higher J values are obtained for deep cracks and the maximum J changed from the deepest point along the crack front to the outer point at the free surface when a/D > 0.2. J values can be estimated for all type of crack geometries under consideration with a correction factor, h1.

Abstract: This paper discusses the effect of Al2O3-13% TiO2 agglomerated nanoparticle powders ranging from 20 to 60 m and microparticle powders ranging from 10 to 25 m on commercial marine grade mild steels using a plasma spray technique. Prior to coating, the nanoparticle powders were subjected to a 2 level factorial design of experiment to give a careful control and optimise the operational spray parameters as well as process by using the statistical methods. The method was focused on the primary gas pressure, carrier gas pressure and powder feed rate of the spray parameters. The optimum properties of wear rate, surface roughness and microhardness were identified by using the lowest primary and carrier gas pressure together with the highest powder feed rate. As for the microparticle powders, they were subjected to an optimum properties by using 35 kW plasma spray power. In this study, the plasma spray power for microparticle varied from 20 kW to 40 kW, while the other parameters such as primary gas pressure, carrier gas pressure, powder feed rate and spray distance were held constant. It was found that microparticle powders exhibited denser coating microstructure s and improved both surface roughness and microhardness. On the other hand, the nanoparticle powder coating gave a greater wear resistance than those of micro particle powders, which may likely due to the strengthening effect of both fully and partially melted region.

Abstract: This work aims to characterise a Cu-based coating material on Al-7075 by using a plasma-spray technique in order to enhance the surface properties of components for automotive applications. Plasma-spray is a process for formation coating on substrates whereby a feedstock is rapidly heated to a molten or near-molten state, and a gas are use to propel the material toward suitably prepared substrate. The most prominent advantages of this method are virtually any coating material can be used and any substrate material can be coated with low thermal stress on substrate parts and high deposition rates [1]. The coating characteristic can be controlled by varying the process variables such as input powers, material feed rates, gas pressures, surface preparation of the substrate and spray distance [2]. The effect of crucial parameters like the electric power input to plasma, spray rate and substrate roughness were studied. The experiments of spraying were design using a 23 fractional factorial plan. The plan allows studying the effect of each factor on the response variables, as well as the effect of interactions between factors on the response variable at the least number of experiment runs. The coating layers have been characterised with respect to the structure by using a scanning electron microscopy (SEM). The result indicates that sprayed particles cool and built up into pancake-like shapes splat, characteristic a plasma spray electric process products. It was found that the optimum parameters were obtained at a power of 24.6 kW, with a powder feed rate of 1 rpm and substrate roughness of 0.5µm.