Papers by mariyam ghazali
Journal of Materials Science, 2009
The success of semi-solid metal processing mostly depends on the formation of suitable starting m... more The success of semi-solid metal processing mostly depends on the formation of suitable starting microstructure, which must consist of solid metal spheroids in a liquid matrix.
This paper discusses the fractography observation in crack propagations of Al6061 under a fatigue... more This paper discusses the fractography observation in crack propagations of Al6061 under a fatigue spectrum loading. Most of the real components and engineering structures are subjected to stress of variable amplitude. The load sequences in variable amplitude loading condition can have a very significant effect on the fatigue crack propagation rate. Fatigue crack propagation tests were performed according to ASTM E647 standard using a 100 kN servo-hydraulic fatigue testing machine. Random loading signals were obtained from the engine mount bracket of an automobile while driven at almost constant velocity onto different surface conditions, i.e. on the residential area and highway road. These random loadings were converted to constant amplitude loading (CAL), high to low and low to high spectrum loadings in order to study the effect of loading sequence on the crack propagation rates. The fatigue fracture surfaces were then analysed using a high magnifying tabletop microscope to identify the fracture behaviour under particular load sequences. Results showed that the fatigue fractography behaviours were influenced significantly by the load interaction and the sequence effect, which can be related to the crack propagation rate of Al6061 under fatigue spectrum loadings.
Materialprufung, Oct 1, 2012
International Journal of Mechanical and Materials Engineering
A sliding wear behaviour of several commercial bearing alloys were tested against a hardened AISI... more A sliding wear behaviour of several commercial bearing alloys were tested against a hardened AISI 4340 steels at three different sliding distance, 500, 800 and 1500 m. Under a pin-on-disc configuration, the test was performed in a lubricated condition (engine oil) in order to imitate the contact behaviour of a connecting rod and a crankshaft in an engine. In this work, deformations of the bearings were being monitored by an acoustic method via airborne. With frequencies ranging from 0 to 20 kHz, deformed bearing signals were then analysed by MATLAB software including the 3D I-kaz method. It was found that wear coefficient, K' for 500 m sliding speed showed 8.5x10 -5 mm³/Nm and based on FFT analysis a signal was generated during the test done. Thus, it can be concluded that the wear loss can be recorded via airborne which was induced by generated sound from the pin and disc contacts.
International Journal of Mechanical and Materials Engineering
The effect of cerium addition on wear behaviour of ascast Al-4Si-4Mg alloys has been studied. Dry... more The effect of cerium addition on wear behaviour of ascast Al-4Si-4Mg alloys has been studied. Dry sliding wear tests were performed against a hardened carbon steel (Fe-2.3%Cr-0.9%C) using a pin-on-disc configuration with fixed sliding speed of 1 m/s and a range of load 10 N, 30 N and 50 N at room temperature (25 o C). Morphologies of both worn surfaces and collected debris were characterised by a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDX). It was revealed that 1 -5 wt% of cerium addition resulted in the formation of intermetallic phase Al-Ce and Al-Si-Ce. The increase of cerium content in the alloy led to higher wear resistance behaviour for ascast alloys. Formation of craters and localised plastic deformation were observed on the worn surface of the alloys, resulting fine particulate and sheet-like wear debris. The change in morphology of the wear debris was also found consistent with the change in worn surface appearance.
International Journal of Mechanical and Materials Engineering
Preparation and characterization of aluminum metal matrix composites reinforced with aluminum nit... more Preparation and characterization of aluminum metal matrix composites reinforced with aluminum nitride was carried out. A graphite crucible and a stainless steel permanent mould was used to prepare the samples. An optimum stirring speed was determined for a fixed stirring time before cast in the permanent mould. Morphology of the composite and particle distribution were investigated by optical microscopy. The reinforcing particles were clearly shown present at the edges and around grains of silicon primary, silicon needles and inter-metallic compound of FeMg 3 Si 6 Al 8. The result of hardness test was 44 Hv for Al-Si matrix and increased to 89 Hv for an Al-Si composite reinforced with 5% wt.% AlN powder. The higher values in hardness indicated that the AlN particles contributed to the increase of hardness of the matrix.
This paper presents a simple method for detecting of wear bearing progression that ranged of low ... more This paper presents a simple method for detecting of wear bearing progression that ranged of low frequency signal f < 20 kHz. This new statistical approached can be computed in real time. The implementation of this technique gives pattern recognition in order to identify bearing wear. The wear test was conducted under pin-on-disc configuration in lubricated sliding condition. It was found that the higher value of I-kaz coefficient, Z ∞ was represented by scattered data in three dimensional in I-kaz three dimensional big spaces and vice versa. It was found that the results for this method may capture realistic behaviour of bearing contacts in which correlates wear progression and the produced signal. From the statistical analyses of the wear bearing, it was possible to correlate the relationship between Taylor Tool Life curve, which was utilized in identifying typical wear growth. The Z ∞ and Taylor curve were observed to the trend of wear rate. The lower value of Z ∞ indicating wear became severe as showed in failure region in Taylor curve.
The work hardening study of four commercial wrought aluminium alloys; AA2124, AA3004, AA5056 and ... more The work hardening study of four commercial wrought aluminium alloys; AA2124, AA3004, AA5056 and AA6092 against two different sliders (M2 steel and an alumina) under dry sliding conditions at 1m/s over the load range 23N to 140N was carried out. A ferrous slider was used, to promote a mechanical mixed layer (MML), whereas an alumina slider to minimise the formation of an MML due to its inert behaviour, so that the true effect of the work hardening induced by wear can be analysed. It was found that in Al/M2 system, the presence of major alloying elements in the Al-alloy that have high solubility in steel promoted a thick mechanically mixed layer. The solubility of these elements in α-Fe is in the order of Si, Mn, Cu, Mg, which roughly approximates the thickness of the MML formed, while the Fe content of the MML also scaled in this order. The MMLs with high Fe content tended to be comprised of fragmented particulate, while a low Fe content tended to be associated with a more homogenous MML. As for the Al/Al 2 O 3 system, the MML was derived from fracture of the slider, and also from transfer and re-transfer of the aluminium alloy. In contrast to the Al/M2 tests, none of the alloying elements in the aluminium alloy were expected to chemically react with the Al 2 O 3 , but the thickness of the MML appears to be controlled by different factors to that against the M2 slider. It was found that the average nano-hardness of the MML layer in the Al/Al 2 O 3 decreased with load. Unlike alloys worn against M2 slider, the nano-hardness of the MML in this work was associated with the wear rate. In the case of slider type, the nano-hardness of precipitate-hardened A2124 against Al 2 O 3 showed lower hardness than those MML worn against M2 slider.
Aluminium alloys are very attractive compared to other materials like steels, particularly for th... more Aluminium alloys are very attractive compared to other materials like steels, particularly for their mechanical properties. Despite of having a relatively low density (2.7 g/cm 3 as compared to ± 7.9 g/cm 3 of steel), they also possess high ductility (even at room temperature), high electrical and thermal conductivity and resistance to corrosion and high thermal conductivity. However, aluminium by itself exhibits poor tribological properties and their usage, for example in automotive applications, has been limited by their inferior strength, rigidity and wear resistance, compared with ferrous alloys. With respect to friction and wear behaviour, it has been well understood that the tribological behaviour of aluminium alloys is strongly influenced by the mechanical, physical and chemical properties of the near-surface materials. Whether lubricated or dry sliding, there is evidence that substantial work-hardening occurs at the worn surface. Surface strains can be well in excess of those found in conventional mechanical working. Intimate contact between ductile materials in particular, normally involved transferred materials, which may result in the formation of a mechanically mixed layer (MML). The MML was generally found to be comprised of materials from both contact surfaces, and may also include oxygen, and was known to have very different properties to the Al-alloy. Although the formation of an MML was known to modify wear behaviour, the exact manner was not fully understood. Moreover, very little was known about the effect that matrix alloy composition had on MML formation although it was claimed that the MML could improved wear resistance.
The effect of surface treatment on the interlaminar fracture toughness of silk/epoxy composite ha... more The effect of surface treatment on the interlaminar fracture toughness of silk/epoxy composite has been studied. The multi-layer woven silk/epoxy composites were produced by a vacuum bagging process in an autoclave with increasing layers of silk fibre of between 8 and 14 layers. Two sets of sample were prepared, in the first sets silk were treated with a surface treatment using a silane-based coupling agent and in the second sets, silk fibre were not treated at all. All the samples have been tested for mode I interlaminar fracture using double cantilever beam specimens (DCB) testing method. It was found that the interlaminar fracture toughness, GIC of the composite in set 1 are higher than set 2 and GIC increases as the number of silk layers increases for both sets. Stable crack propagation is observed for both sets of samples during the tests and the crack propagation areas for the untreated fibres showed all the fibres were bare with no matrix covering them as were seen at 100x an...
Materials & Design, 2013
ABSTRACT The study aimed to present several fatigue tests under loading sequences, and to compare... more ABSTRACT The study aimed to present several fatigue tests under loading sequences, and to compare the fatigue life behaviour between AA6061 and AA7075 alloys subjected to spectrum loadings at room and elevated temperatures. Constant amplitude loading (CAL), high-to-low and low-to-high loading sequences were derived from a real-time variable amplitude loading that captured from an engine mount bracket of a 1300 cc automobile under normal driving conditions. The shortest fatigue life was found under CAL, followed by the high-to-low and low-to-high loading sequences at both room and elevated temperatures with difference between the maximum and minimum cycles ranged from 7% to 84%. Increased testing temperature (from 27 �C to 250 �C) exponentially decreased the number of cycles by 75–84%. The effect of loading sequence was more significant at room temperature than at elevated temperature.
Jurnal Teknologi, 2013
This paper discusses a methodology used to predict the stress-life (S-N) curve at elevated temper... more This paper discusses a methodology used to predict the stress-life (S-N) curve at elevated temperatures based on the normal S-N curve. Fatigue tests were performed under stress control at room temperature in accordance with the ASTM E466 standard to obtain a normal S-N curve. In addition, the tests were performed at both room and elevated temperatures using constant-amplitude, high-to-low sequence, and low-to-high sequence loadings to investigate the effect of the load sequence at elevated temperatures on fatigue life. Three elevated temperature regimes at 70 to 250C were chosen based on the maximum temperature of the engine mount bracket and the cylinder head that can be reached during normal service. The results show that the fatigue lives were significantly affected by the load sequences at both room and elevated temperatures. Furthermore, the existing fatigue data obtained at elevated temperatures can be used to predict the corresponding S-N curves.
Tribology International, 2015
ABSTRACT With good combination of hardness, ductility, and wear resistance, TiO2 coatings are one... more ABSTRACT With good combination of hardness, ductility, and wear resistance, TiO2 coatings are one of the most potential hard ceramic coatings. TiO2 in an Al2O3 coating had increases the wear resistance which has contributed to an increase in the fracture toughness and decrease in the coefficient of friction. The specific wear rates of pure TiO2 coatings are found to be ranging from 1.62×10−5-4.19×10−5 cm3/N.m whereas the Al2O3/TiO2 coatings are in the range of 2.0×10−3 cm3/N.m to 28.0×10−3 cm3/N.m. This concludes that the TiO2 coatings are most preferable in improving wear resistance.
Materials & Design, 2015
ABSTRACT The microstructural and dry sliding wear characteristics of thixoformed A319 aluminium a... more ABSTRACT The microstructural and dry sliding wear characteristics of thixoformed A319 aluminium alloy are investigated and compared with those of a conventional mould cast alloy. Cooling slope technique was employed to produce thixoforming feedstock with pouring temperatures between 620 and 640 C, plate lengths between 300 and 500 mm and 60 inclined angle. The optimum rheocast alloy was thixoformed at 50% liquid fraction. A pin-on-disc tribometer was used to conduct tribological tests under dry sliding conditions at 1.0 m/s sliding speed, under three loads of 10, 50 and 100 N and 9 km distance. The dendritic microstructure in the conventionally cast alloy transforms into a globular or rosette-like microstructure using cooling slope method with optimum conditions of 630 C pouring temperature and 400 mm plate length, which gives a grain size of 34 lm and shape factor of 0.75. Thixoformed alloy microstructure shows a fine globular primary phase, fragmented and uniformly distributed silicon and intermetallic compounds. Also the thixoformed alloy exhibits improved wear resistance and lower friction coefficient in comparison to the cast alloy particularly at low load. The dominant wear mechanism is a combination of abrasive and adhesive wear at low load and plastic deformation followed by adhesive wear at high load.
International Journal of Modern Physics B, 2009
This article studies about the mechanical strength of different functionalized Carbon nanotubes (... more This article studies about the mechanical strength of different functionalized Carbon nanotubes (CNTs) reinforced Polyethylene (PE) fiber composite fabricated by melt spinning. There are four types of CNTs used, which are called as produced, carboxylated, octadecylated, polymer wrapped CNTs. Influence of mechanical drawing (melt spinning) on the mechanical strength of fibers is measured by direct comparison with mechanical strength of bulk type functionalized CNTs polymer composites, which fabricated using hot press. Dispersion and interfacial bonding strength/adhesion of CNTs with PE matrix are investigated through fracture surfaces image analysis. Functionalized CNTs composites show a significant improvement of mechanical strength of pure polymer than non functionalized CNTs polymer composite. Whereas polymer wrapped CNTs polymer composite give the highest mechanical strength in this study. Mechanical strength of bulk composites are significantly increased after mechanical drawing process indicates that melts spinning may influence on the crystallization of polymer. Fracture surface analysis revealed that additional functionalized CNTs enhanced dispersion and interfacial bonding with polymer matrix.
This paper discusses the fractography observation in crack propagations of Al6061 under a fatigue... more This paper discusses the fractography observation in crack propagations of Al6061 under a fatigue spectrum loading. Most of the real components and engineering structures are subjected to stress of variable amplitude. The load sequences in variable amplitude loading condition can have a very significant effect on the fatigue crack propagation rate. Fatigue crack propagation tests were performed according to ASTM E647 standard using a 100 kN servo-hydraulic fatigue testing machine. Random loading signals were obtained from the engine mount bracket of an automobile while driven at almost constant velocity onto different surface conditions, i.e. on the residential area and highway road. These random loadings were converted to constant amplitude loading (CAL), high to low and low to high spectrum loadings in order to study the effect of loading sequence on the crack propagation rates. The fatigue fracture surfaces were then analysed using a high magnifying tabletop microscope to identify the fracture behaviour under particular load sequences. Results showed that the fatigue fractography behaviours were influenced significantly by the load interaction and the sequence effect, which can be related to the crack propagation rate of Al6061 under fatigue spectrum loadings.
ABSTRACT Semi-metallic friction composites (SMFC) consist of epoxidised natural rubber with 50 mo... more ABSTRACT Semi-metallic friction composites (SMFC) consist of epoxidised natural rubber with 50 mol % epoxidation (ENR50), alumina nanoparticle, steel wool, graphite and benzoxazine were prepared by melt mixing using Haake internal mixer at 90°C and 60 rpm rotor speed. The composites were vulcanized using different crosslinking systems, namely, sulfur and electron beam (EB) crosslinking. The samples were subjected for friction test in order to determine friction and wear properties of SMFC. The friction–wear properties of the SMFC crosslinked by electron beam irradiation and sulfur vulcanization system were compared. The friction coefficient in normal and hot condition of irradiated SMFC were higher than those of sulphur vulcanized samples at all applied doses. On the other hand the specific wear rates of irradiated samples were lower than the sulfur vulcanized samples at all applied doses. The sample crosslinked by EB irradiation at 150 kGy dose found to exhibit the best tribological property, as evident from the higher friction coefficient (about 0.461) and lower wear achieved at 150 kGy irradiation as compared to sulphur vulcanization of the SMFC.
This paper discusses the fatigue strain signal behaviour of different road surface conditions and... more This paper discusses the fatigue strain signal behaviour of different road surface conditions and its relationship to the fatigue damage of an engine mount bracket. Two different sets of fatigue strain signals were obtained from an engine mount bracket of an automobile: when the automobile was driven on a highway surface and on a residential area road surface. The behaviour of the strain signal was then analysed and classified using both statistical and signal processing tools. Damage values as a result of the corresponding fatigue strain signals also determined using commercial finite element software. The fatigue strain signal behaviour was influenced by the road surface conditions, which affected the damage to the engine mount bracket. The integrated kurtosis-based algorithm for the Z-filter and power spectral density calculation were found to be the most suitable signal analysis approaches to correlate the fatigue strain signal behaviour with the engine mount bracket damage.
International Journal of Modern Physics B, 2009
This paper presents the performance of uncoated carbide cutting tool when machining cast iron in ... more This paper presents the performance of uncoated carbide cutting tool when machining cast iron in dry cutting conditions. Experiments were conducted at various cutting speeds, feed rates, and depths of cut according to Taguchi method design of experiment using a standard orthogonal array L9(3 4 ). The effects of cutting speeds (100-146 m/min), feed rates (0.20-0.35 mm/tooth) and depths of cut (1.0-2.0 mm) on the tool life, surface roughness and cutting forces were evaluated using ANOVA. Results showed that the effects of cutting speed, depth of cut and the feed rate were similar affecting the failure of the carbide cutting tools within the range of tested machining parameters. The contribution of cutting speed, feed rate, and depth of cut in controlling the tool life were 32.12%, 38.56% and 29.32% respectively. Whereas, the cutting speed was the main factor influencing the average surface roughness (Ra) value followed by feed rate. These factors contribute 60.53% and 35.59% respectively to the Ra value. On the other hand, cutting forces generated were greatly influenced by the depth of cut (66.52%) and the feed rate (32.6%). Cutting speed was found insignificant in controlling the generated cutting forces.
course, which has been introduced in 2010 in the Department of Mechanical & Materials Engineering... more course, which has been introduced in 2010 in the Department of Mechanical & Materials Engineering, of Universiti Kebangsaan Malaysia (UKM). The course is only available for students who register KKKJ 6004 (Project 1) in the first semester, which would be then continued in the following semester as KKJ 6008 with greater credit units. It argues that the students value the implementation of the course being embedded in Project 1 (semester 1) but suggests that the course needs to be offered in the following semester (semester 2) as well in order to assist them in producing better quality project reports. Furthermore, they strongly agree that the requirement for submitting an Executive Summary during the project assessment (viva-voce) is a good practice, primarily because the summaries can give better understanding to the viva-examiners on their work.
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Papers by mariyam ghazali