Mohd Hamdi Abd Shukor - Profile on Academia.edu (original) (raw)

Papers by Mohd Hamdi Abd Shukor

ASEAN Engineering Journal, Sep 15, 2012

Joining of dissimilar materials especially in the case of polymer and metal structure is signific... more Joining of dissimilar materials especially in the case of polymer and metal structure is significantly challenging due to the difference in chemical, mechanical and thermal properties of materials. Traditionally, metal and plastics are joined together either mechanically or by using adhesives. However, these techniques have limited use in joining small sized and intricately shaped parts. To address this limitation, constant effort on the development of reliable joining processes for polymer-metal structures are currently being explored. This article provides a brief review of joining polymer and metal using laser joining technique. A summary of relevant works carried out in recent years, the choices of lasers available, the most suitable laser technique, the mechanism of joining and significant findings by selected researchers are presented in this article.

Ti-based Ceramic Composite Processing Using Hybrid Centrifugal Thermite Assisted Technique

Mechanical Properties and Performance of Engineering Ceramics and Composites X, 2015

A fundamental study was conducted to investigate Ti-C system when it is exposed to a hybrid react... more A fundamental study was conducted to investigate Ti-C system when it is exposed to a hybrid reaction between thermite and elemental powders of titanium and carbon under centrifugal acceleration. A pellet of Ti+C was fixed in an offset position relative to the surrounding steel tube in the reaction chamber, which was filled with thermite mixture. The aluminothermic mixture was ignited; it generated a massive amount of heat and was able to initiate a secondary reaction. The secondary Ti+C reaction was affected by the high temperature. Several byproducts were formed, including intermetallics contents. A microstructure and phase analysis of the synthesized product are investigated in this paper, revealing 27% formation of a new product with 796 MPa hardness. The study explains how the Ti+C behaved at the time of short and sudden heating environment.

Effect of Curvature and Thickness of Aluminum Shells on the Energy Absorption in Low Velocity Impact

Advanced Materials Research, 2012

ABSTRACT The objective of this study is to investigate the behavior of Aluminum shells AA5083-H11... more ABSTRACT The objective of this study is to investigate the behavior of Aluminum shells AA5083-H116 under low energy impact and the effects of curvature and thickness were assessed under different impact velocities (5.6, 7.5, 9.5, 11.5 m/s). LS-DYNA software was used to evaluate the amount of absorbed energy by the Aluminum shell during impact under different curvature parameter c. The results showed that the amount of absorbed energy incereases with increasing curvature in a linear relationship which make it possible to predict the amount of absorbed energy for this aluminum alloy under different impact energy. Aslo, the amount of absorbed energy has a direct linear relation with the rise of impact energy. The slopes of curves for absorbed energy with respect to the imapct energy are similar for all curvatures. Shell thickness has inverse effect on the amount of absorbed energy and the relation shows similar ternds with diffrent curvatures. However thick shells show significant increase in maximum force and better stability in the dynamic behavior with less fluctuations in the impact force as the cuvature increases.

The Evaluation of EOR Methods for a Heavy-oil Reservoir With the AHP Method: The Case of Ferdowsi Reservoir

Petroleum Science and Technology, 2013

ABSTRACT Enhanced oil recovery (EOR) strategies for development of heavy oil reservoirs is a very... more ABSTRACT Enhanced oil recovery (EOR) strategies for development of heavy oil reservoirs is a very complex process because it involves a great amount of money and parameters and it is necessary to consider the risk associated with geological, economical, and technological uncertainties. On the other hand the wrong strategies risk time and national capital, especially in Iran. Therefore, it is very important to choose the proper strategy to improve the quality of the results and to accelerate the process. The authors applied the analytic hierarchy process to evaluate five alternatives for EOR of a heavy oil reservoir in one Iran's heavy oil fields. This method helps reservoir management team to structure the fundamental hierarchy model, which is suited for the Ferdowsi reservoir in Iran's situation.

Journal of the Mechanical Behavior of Biomedical Materials, 2010

It is generally accepted that calcium phosphate (CaP) is one of the most important biomaterials i... more It is generally accepted that calcium phosphate (CaP) is one of the most important biomaterials in implant coating applications mainly because of its excellent bioactivity. However, its relatively poor mechanical properties limits its application. This entails that a better understanding of the mechanical properties of a CaP coating is a must especially its behavior and the mechanisms involved when subjected to stresses which eventually lead to failure. The mechanical properties of the coating may be evaluated in terms of its adhesion strength. In this study, a radio frequency-magnetron (RF-MS) sputtering technique was used to deposit CaP thin films on 316L stainless steel (SS). The coatings were subjected to series of microscratch tests, taking careful note of its behavior as the load is applied. The adhesion behavior of the coatings showed varying responses. It was revealed that several coating process-related factors such as thickness, post-heat treatment and deposition parameters, to name a few, affect its scratching behavior. Scratch testing-related factors (i.e. loading rate, scratch speed, scratch load, etc.) were also shown to influence the mechanisms involved in the coating adhesion failure. Evaluation of the load-displacement graph combined with optical inspection of the scratch confirmed that several modes of failure occurred during the scratching process. These include trackside cracking, tensile cracking, radial cracking, buckling, delamination and combinations of one or more modes.

Dental Materials Journal, 2011

This study aimed to compare the biomechanical behaviour of functionally graded structured posts (... more This study aimed to compare the biomechanical behaviour of functionally graded structured posts (FGSPs) and homogenous-type posts in simulated models of a maxillary central incisor. Two models of FGSPs consisting of a multilayer xTi-yHA composite design, where zirconia and alumina was added as the first layer for models A and B respectively were compared to homogenous zirconia post (model C) and a titanium post (model D). The amount of Ti and HA in the FGSP models was varied in gradations. 3D-FEA was performed on all models and stress distributions were investigated along the dental post. In addition, interface stresses between the posts and their surrounding structures were investigated under vertical, oblique, and horizontal loadings. Strain distribution along the post-dentine interface was also investigated. The results showed that FGSPs models, A and B demonstrated better stress distribution than models C and D, indicating that dental posts with multilayered structure dissipate localized and interfacial stress and strain more efficiently than homogenous-type posts.

Jurnal Kejuruteraan

Hydroxyapatite (HA), a ceramic phosphate with good biocompatibility, has been extensively used in... more Hydroxyapatite (HA), a ceramic phosphate with good biocompatibility, has been extensively used in the field of bone replacement, both in orthopedics and in dentistry. Desired molded part of HA is fabricated by using powder injection molding (PIM) method. Powder loading, rheological properties and sintering atmosphere can significantly affect the quality of molded HA. The effect of these factors on the microstructure and mechanical properties of powder injection molded HA were investigated. Different powder loading of HA (54, 55 and 56 vol%), were mixed with binder 40 wt.% of palm stearin and 60 wt.% polyethylene. The temperature injection were set at 150°C, 160°C and 170°C with the pressure injection of 12 bar. The green body were then sintered in the furnace at temperature of 1100°C, 1200°C and 1300°C for 4 hours. Analysis of variance (ANOVA) is used to determine the optimization of injection molding. Based on the analysis, it was found that 56 vol% powder loading, temperature inje...

Performance evaluation of different types of cutting fluid in the machining of aisi 01 hardened steel using pulsed jet minimal quantity lubrication system

ASEAN Engineering Journal, Jul 22, 2011

ABSTRACT This paper presents the performance evaluation of three different cutting fluids used in... more ABSTRACT This paper presents the performance evaluation of three different cutting fluids used in a minimal quantity lubrication (MQL) system. The MQL system, developed in-house at the University of Malaya, was capable of delivering high velocity cutting fluid in narrow pulsed jet forms at a rate of 2 ml/min and a pressure of 20 MPa. The three cutting fluids chosen were neat oil, soluble oil and semi-synthetic cutting fluids. The experiments were designed to evaluate the performance of the fluids at various cutting velocities of 20,40 and 60 m/min and feed rates of 0.05,0.06 and 0.07 mm/tooth. The results were measured in terms of the average surface roughness of the machined workpiece, the cutting forces and the maximum flank wear. In addition, the resultant chip formations were also observed. Analysis of the results has shown that in general, neat oil had performed the best in low cutting velocities and feed rates. On the other hand, soluble oil gave the lowest cutting forces and flank wears at high cutting velocities and feed rated as compared to neat oil and synthetic cutting fluid. It was observed that performance of soluble oil does not drastically change with variation to the cutting velocities and feed rates. Thus, the choice of soluble oil would be most appropriate for general machining usage. With suitable machining parameter selection, water-mixed cutting fluids (soluble oil and semisynthetics) performed comparatively well to deliver low surface roughness results. Therefore, this can be an economical choice for use in industrial production processes.

Advanced Materials Research, 2012

This work details the characterization of anatase nanoTiO2particles synthesized from Malaysian mi... more This work details the characterization of anatase nanoTiO2particles synthesized from Malaysian mineral precursors using the XRD and EDXRF. The properties that were analyzed were its crystallite sizes, relative crystallinity, phases, and chemical composition. It was determined that the crystallite size was quite small (15.6 nm), although the crystallinity of the sample is relatively low. The anatase phase seems to be dominant (100%), although in some cases when the processing parameters were changed or heat treatment were conducted, the existence of rutile is detected. The chemical composition showed that TiO2is the majority compound in the sample (~96%), although some metallic and non-metallic impurities are present (Zr, Nb, and S). It is concluded that Malaysian mineral precursors are capable of producing relatively high quality nanoTiO2.

36th International Electronics Manufacturing Technology Conference, 2014

The microstructural and mechanical properties of Sn-3.0Ag-0.5Cu lead-free solders added with a po... more The microstructural and mechanical properties of Sn-3.0Ag-0.5Cu lead-free solders added with a porous Cu interlayer were investigated. Two types of porous Cu, P15 and P25 with the diameter of ϕ1.7 mm and ϕ1.0mm respectively were used in this study. The porous Cu was arranged in a sandwich-liked layer in between Sn-3.0Ag-0.5Cu solder alloys with rod Cu as a substrate metal. Solder joint without porous Cu interlayer were also prepared as the control sample. Three soldering temperatures of 267ºC, 287ºC and 307ºC with soldering time of 5 minute were applied. Tensile test was performed to evaluate the joint strength of the solder alloy. The result shows that the joint strength increased proportionately with increasing soldering temperature and smaller pore size of porous Cu. Microstructure and fracture surface were observed by using optical microscopy (OM) in order to understand the failure behavior of the joint. It is found that penetration of molten solder alloy into the various pore sizes of porous Cu interlayer significantly influenced fracture morphology and strength of the joint.

Surface and Coatings Technology, 2013

Highly oriented titania nanotube arrays are formed by self-organizing anodization of Ti foil in o... more Highly oriented titania nanotube arrays are formed by self-organizing anodization of Ti foil in organic electrolytes in the presence of fluoride ions. The effects of tube length and the tube wall stratified layer on the electrochemical capacitance of these bamboo-type nanotubes are investigated. Field emission scanning electron microscopy (FESEM) is used to characterize the surface morphology, while cyclic voltammetry is used to investigate the pseudocapacitive properties of these nanostructured electrodes. The bamboo-type titania nanotube array with a higher aspect ratio shows a higher specific capacitance value of 52 μF cm -2 in 1 M Na 2 SO 4 with excellent reversibility characteristics. The introduction of surface defects by annealing in NH 3 increased the specific capacitance value to 118 μF cm -2 . This simple and cost-saving binder-free electrode is considered a promising candidate for supercapacitor applications.

Ceramics International, 2014

Porous three-dimensional hydroxyapatite (HA) scaffolds were prepared using bovine cortical bone d... more Porous three-dimensional hydroxyapatite (HA) scaffolds were prepared using bovine cortical bone derived HA (BDHA). Analyses of the morphology, chemical composition, and phase purity of the scaffold were performed using scanning electron microscopy (SEM), micro-computer tomography (micro-CT), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). SEM images revealed the rough and porous surface of the scaffold, while micro-CT showed the average porous volume of 76.7 70.6% and pore size of 0.04-0.25 mm. Single phase corresponding to standard HA was observed using XRD, and FTIR confirmed the presence of functional groups similar to HA. The EDX analysis revealed a Ca/P ratio of 1.61, which was comparable with HA stoichiometry. Compressive strength of the BDHA scaffold was found to be 1.37 0.09 MPa. After 14 days of human bone marrow stromal cells (hBMSCs) seeding, SEM and confocal analysis revealed cell attachment to the surface and infiltration into the pores. Alamar blue and alkaline phosphatase assays showed significantly increased cell proliferation and differentiation in the BDHA scaffold, when compared with that in the monolayer (p o0.01). In addition, quantitative real-time polymerase chain reaction (qPCR) data confirmed the up regulation of genes involved in osteogenic differentiation of mesenchymal stem cells. Our findings indicate that BDHA scaffold provides a favorable physiological environment for enhanced cell attachment, proliferation, and osteogenic differentiation of hBMSCs.

Arabian Journal for Science and Engineering, 2012

A nano-titanium dioxide (nano-TiO 2 ) powder, with Zr (0.5-1 %) and Nb (0.5-1 %) impurities, is f... more A nano-titanium dioxide (nano-TiO 2 ) powder, with Zr (0.5-1 %) and Nb (0.5-1 %) impurities, is fabricated using a modified hydrothermal method, with lowgrade mineral precursors. Samples were then sintered at 600, 800, and 1,000 • C, then analysed using XRD (crystallite size and phase conversion temperature), scanning electron microscope (SEM) (morphology), N 2 adsorption-desorption isotherms (surface area), and UV-vis-NIR (absorbance and optical transmission) to study the effects of sintering on the structural and optical properties of the synthesized nanopowders. It was discovered that sintering to 1,000 • C reduces the surface area by 99 %, and increases the crystallite size by almost 2,000 %. Meanwhile, the phase conversion temperature of this sample is 33.3 % higher than that reported in the literature for 600 • C. SEM shows an extensive agglomeration and uneven distribution of nano-TiO 2 particles before sintering. However, the sintered sample shows uniformity in particle size and distribution, and even though it is reduced significantly, agglomeration is still present. The absorbance of the samples is red-shifted towards the visible region (i.e., 380-700 nm), with the optical band-gap reduced by 10 %,

Development of Magnesium-Doped Biphasic Calcium Phosphatethrough Sol-Gel Method

IFMBE Proceedings

ABSTRACT Calcium phosphate is an interesting material for bone implant applications, as it shows ... more ABSTRACT Calcium phosphate is an interesting material for bone implant applications, as it shows biocompatibility and bioactivity to tissue bone. Among calcium phosphate-based materials, biphasic calcium phosphate (BCP), a mixture of non-resorbable hydroxyapatite (HA) and resorbable tricalcium phosphate (TCP), has shown to possess unique characteristics appropriate for bone replacement. Doping of magnesium ions into BCP will bring biological improvement. Magnesium ion was found to cause the acceleration of nucleation kinetics of bone minerals. Magnesium depletion adversely affects all stages of skeletal metabolism, leading to decrease in osteoblastic activities and bone fragility. Therefore, the incorporation of magnesium ions into the calcium phosphate structure is of great interest for the development of artificial bone implants. Here we present magnesium-doped biphasic calcium phosphate (Mg-BCP) using chemical doping process through a solgel method. Mg-BCP was produced using calcium nitrate tetrahydrate and di-ammonium hydrogen phosphate as the precursors for calcium and phosphorus, respectively. Magnesium nitrate was used as the source of the dopant. An ammoniacal solution of the monomers was heated until a white gel was obtained. The obtained gel was then dried and subsequently subjected to calcinations. The change in physicochemical properties has been evaluated by using XRD, FTIR, TG/DTA, and FESEM. Individual particles are of less than 100 nm in size, spherical shapes and tightly agglomerated. XRD measurement shown that the powder is Mg-doped BCP with 100% purity, and crystallinity increased with increased of Mg content. FTIR spectroscopy measurement also showed that the increment of crystallinity is directly proportional to the amount of dopant leading to the conclusion that magnesium acts as a sintering additive. This result is in good agreement with the analysis of FESEM where the particles of the Mgdoped BCP are larger as the amount of dopant increased as a result of more progressive fusion of particles.

Optimizing the cutting parameters for better surface quality in 2.5D cutting utilizing titanium coated carbide ball end mill

International Journal of Precision Engineering and Manufacturing, Nov 29, 2012

Novel uses of SiO2 nanolubrication in end milling of medium carbon steel for higher compressive residual stress measured by high-energy X-ray diffraction data

Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, Oct 13, 2015

Milling is a machining process that removes any desired material from the surface by using relati... more Milling is a machining process that removes any desired material from the surface by using relative motion between a work piece and a rotating cutter where the cutting tool intermittently enters and leaves the work piece. The milling process operates in two modes, namely, conventional (up) mode and climb (down) mode. Both modes are known for their significant effects on surface integrity due to the entering movement of the cutting tool and the formation of the chips during cutting process. Use of flood lubrication can improve the residual stress and surface quality of the component. It controls the temperature in cutting zone, reduces the power required, washes away chips, and reduces friction between chips, tools, and workpieces. Moreover, it has a great effect on the environment too. Minimum quantity lubrication can be used as an alternative of lubrication for clean machining. With an addition of nanoparticles into the minimum quantity lubrication, it is expected to enhance the machining performance that meets the environmental friendly purposes. Residual stresses remain in a solid material in the absence of external loading or thermal gradients, which is sometimes undesirable. The presence of compressive residual stresses is beneficial, while the presence of tensile stresses is detrimental. In order to study the residual stress and its relation with the surface quality (after milling process), the effects of reduced oil consumption in minimum quantity lubrication and the addition of SiO2 nanoparticles in minimum quantity lubrication for clean machining are presented in this research. Results indicate that there is an improvement in residual stresses and surface quality especially during conventional (up) milling under minimum quantity lubrication and minimum quantity lubrication–SiO2 nanolubrication condition.

Enhanced surface roughness of AISI D2 steel machined using nano-powder mixed electrical discharge machining

The International Journal of Advanced Manufacturing Technology, 2017

Conventional methods of building CNC machine tools involve using linear motors and ball screw dri... more Conventional methods of building CNC machine tools involve using linear motors and ball screw drives to obtain table motion. The double opposite sync motion design is an improvement over traditional CNC machines. In this work, an enhanced CNC gantry machine design is proposed, which exhibits a double motion mechanism. The new design is based on a rack and pinion system such that both the gantry tool and worktable are movable. The gantry's natural frequency was designed at 202 Hz in the first vibration mode, enabling it to work at higher speeds of up to 11,530 rpm, which makes the gantry suitable for both rough cutting and fine finishing. A prototype of the multi-mode motion CNC gantry milling machine was developed to investigate the machining performance and efficiency of the double opposite sync system. Performance analysis was done using ball bar precision tests on the different modes of CNC gantry operation. Validation tests were carried out to determine the effects of the motion of the machine parts on the dimensional accuracy and surface finish of the machined parts. The results indicated that the straightness of the developed machine was reduced from 176.3 to 114.6 μm, which occurred due to the reduced total distance travelled by the tool and worktable. Moreover, the circularity increased from 338.7 to 667.0 μm. This increase could be attributed to the combination of errors arising from both the gantry and table.

PLOS ONE, 2015

Titanium carbide-graphite (TiC/C) composite was successfully synthesized from Ti and C starting e... more Titanium carbide-graphite (TiC/C) composite was successfully synthesized from Ti and C starting elemental powders using self-propagating high-temperature synthesis technique in an ultra-high plasma inert medium in a single stage. The TiC was exposed to a high-temperature inert medium to allow recrystallization. The product was then characterized using field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Rietveld refinement, nanoindentation, and microhardness to determine the product's properties. The recorded micro-hardness of the product was 3660 HV, which is a 14% enhancement and makes is comparable to TiC materials.

Optimizing the cutting parameters for better surface quality in 2.5D cutting utilizing titanium coated carbide ball end mill

International Journal of Precision Engineering and Manufacturing, 2012

ASEAN Engineering Journal, Sep 15, 2012

Joining of dissimilar materials especially in the case of polymer and metal structure is signific... more Joining of dissimilar materials especially in the case of polymer and metal structure is significantly challenging due to the difference in chemical, mechanical and thermal properties of materials. Traditionally, metal and plastics are joined together either mechanically or by using adhesives. However, these techniques have limited use in joining small sized and intricately shaped parts. To address this limitation, constant effort on the development of reliable joining processes for polymer-metal structures are currently being explored. This article provides a brief review of joining polymer and metal using laser joining technique. A summary of relevant works carried out in recent years, the choices of lasers available, the most suitable laser technique, the mechanism of joining and significant findings by selected researchers are presented in this article.

Ti-based Ceramic Composite Processing Using Hybrid Centrifugal Thermite Assisted Technique

Mechanical Properties and Performance of Engineering Ceramics and Composites X, 2015

A fundamental study was conducted to investigate Ti-C system when it is exposed to a hybrid react... more A fundamental study was conducted to investigate Ti-C system when it is exposed to a hybrid reaction between thermite and elemental powders of titanium and carbon under centrifugal acceleration. A pellet of Ti+C was fixed in an offset position relative to the surrounding steel tube in the reaction chamber, which was filled with thermite mixture. The aluminothermic mixture was ignited; it generated a massive amount of heat and was able to initiate a secondary reaction. The secondary Ti+C reaction was affected by the high temperature. Several byproducts were formed, including intermetallics contents. A microstructure and phase analysis of the synthesized product are investigated in this paper, revealing 27% formation of a new product with 796 MPa hardness. The study explains how the Ti+C behaved at the time of short and sudden heating environment.

Effect of Curvature and Thickness of Aluminum Shells on the Energy Absorption in Low Velocity Impact

Advanced Materials Research, 2012

ABSTRACT The objective of this study is to investigate the behavior of Aluminum shells AA5083-H11... more ABSTRACT The objective of this study is to investigate the behavior of Aluminum shells AA5083-H116 under low energy impact and the effects of curvature and thickness were assessed under different impact velocities (5.6, 7.5, 9.5, 11.5 m/s). LS-DYNA software was used to evaluate the amount of absorbed energy by the Aluminum shell during impact under different curvature parameter c. The results showed that the amount of absorbed energy incereases with increasing curvature in a linear relationship which make it possible to predict the amount of absorbed energy for this aluminum alloy under different impact energy. Aslo, the amount of absorbed energy has a direct linear relation with the rise of impact energy. The slopes of curves for absorbed energy with respect to the imapct energy are similar for all curvatures. Shell thickness has inverse effect on the amount of absorbed energy and the relation shows similar ternds with diffrent curvatures. However thick shells show significant increase in maximum force and better stability in the dynamic behavior with less fluctuations in the impact force as the cuvature increases.

The Evaluation of EOR Methods for a Heavy-oil Reservoir With the AHP Method: The Case of Ferdowsi Reservoir

Petroleum Science and Technology, 2013

ABSTRACT Enhanced oil recovery (EOR) strategies for development of heavy oil reservoirs is a very... more ABSTRACT Enhanced oil recovery (EOR) strategies for development of heavy oil reservoirs is a very complex process because it involves a great amount of money and parameters and it is necessary to consider the risk associated with geological, economical, and technological uncertainties. On the other hand the wrong strategies risk time and national capital, especially in Iran. Therefore, it is very important to choose the proper strategy to improve the quality of the results and to accelerate the process. The authors applied the analytic hierarchy process to evaluate five alternatives for EOR of a heavy oil reservoir in one Iran's heavy oil fields. This method helps reservoir management team to structure the fundamental hierarchy model, which is suited for the Ferdowsi reservoir in Iran's situation.

Journal of the Mechanical Behavior of Biomedical Materials, 2010

It is generally accepted that calcium phosphate (CaP) is one of the most important biomaterials i... more It is generally accepted that calcium phosphate (CaP) is one of the most important biomaterials in implant coating applications mainly because of its excellent bioactivity. However, its relatively poor mechanical properties limits its application. This entails that a better understanding of the mechanical properties of a CaP coating is a must especially its behavior and the mechanisms involved when subjected to stresses which eventually lead to failure. The mechanical properties of the coating may be evaluated in terms of its adhesion strength. In this study, a radio frequency-magnetron (RF-MS) sputtering technique was used to deposit CaP thin films on 316L stainless steel (SS). The coatings were subjected to series of microscratch tests, taking careful note of its behavior as the load is applied. The adhesion behavior of the coatings showed varying responses. It was revealed that several coating process-related factors such as thickness, post-heat treatment and deposition parameters, to name a few, affect its scratching behavior. Scratch testing-related factors (i.e. loading rate, scratch speed, scratch load, etc.) were also shown to influence the mechanisms involved in the coating adhesion failure. Evaluation of the load-displacement graph combined with optical inspection of the scratch confirmed that several modes of failure occurred during the scratching process. These include trackside cracking, tensile cracking, radial cracking, buckling, delamination and combinations of one or more modes.

Dental Materials Journal, 2011

This study aimed to compare the biomechanical behaviour of functionally graded structured posts (... more This study aimed to compare the biomechanical behaviour of functionally graded structured posts (FGSPs) and homogenous-type posts in simulated models of a maxillary central incisor. Two models of FGSPs consisting of a multilayer xTi-yHA composite design, where zirconia and alumina was added as the first layer for models A and B respectively were compared to homogenous zirconia post (model C) and a titanium post (model D). The amount of Ti and HA in the FGSP models was varied in gradations. 3D-FEA was performed on all models and stress distributions were investigated along the dental post. In addition, interface stresses between the posts and their surrounding structures were investigated under vertical, oblique, and horizontal loadings. Strain distribution along the post-dentine interface was also investigated. The results showed that FGSPs models, A and B demonstrated better stress distribution than models C and D, indicating that dental posts with multilayered structure dissipate localized and interfacial stress and strain more efficiently than homogenous-type posts.

Jurnal Kejuruteraan

Hydroxyapatite (HA), a ceramic phosphate with good biocompatibility, has been extensively used in... more Hydroxyapatite (HA), a ceramic phosphate with good biocompatibility, has been extensively used in the field of bone replacement, both in orthopedics and in dentistry. Desired molded part of HA is fabricated by using powder injection molding (PIM) method. Powder loading, rheological properties and sintering atmosphere can significantly affect the quality of molded HA. The effect of these factors on the microstructure and mechanical properties of powder injection molded HA were investigated. Different powder loading of HA (54, 55 and 56 vol%), were mixed with binder 40 wt.% of palm stearin and 60 wt.% polyethylene. The temperature injection were set at 150°C, 160°C and 170°C with the pressure injection of 12 bar. The green body were then sintered in the furnace at temperature of 1100°C, 1200°C and 1300°C for 4 hours. Analysis of variance (ANOVA) is used to determine the optimization of injection molding. Based on the analysis, it was found that 56 vol% powder loading, temperature inje...

Performance evaluation of different types of cutting fluid in the machining of aisi 01 hardened steel using pulsed jet minimal quantity lubrication system

ASEAN Engineering Journal, Jul 22, 2011

ABSTRACT This paper presents the performance evaluation of three different cutting fluids used in... more ABSTRACT This paper presents the performance evaluation of three different cutting fluids used in a minimal quantity lubrication (MQL) system. The MQL system, developed in-house at the University of Malaya, was capable of delivering high velocity cutting fluid in narrow pulsed jet forms at a rate of 2 ml/min and a pressure of 20 MPa. The three cutting fluids chosen were neat oil, soluble oil and semi-synthetic cutting fluids. The experiments were designed to evaluate the performance of the fluids at various cutting velocities of 20,40 and 60 m/min and feed rates of 0.05,0.06 and 0.07 mm/tooth. The results were measured in terms of the average surface roughness of the machined workpiece, the cutting forces and the maximum flank wear. In addition, the resultant chip formations were also observed. Analysis of the results has shown that in general, neat oil had performed the best in low cutting velocities and feed rates. On the other hand, soluble oil gave the lowest cutting forces and flank wears at high cutting velocities and feed rated as compared to neat oil and synthetic cutting fluid. It was observed that performance of soluble oil does not drastically change with variation to the cutting velocities and feed rates. Thus, the choice of soluble oil would be most appropriate for general machining usage. With suitable machining parameter selection, water-mixed cutting fluids (soluble oil and semisynthetics) performed comparatively well to deliver low surface roughness results. Therefore, this can be an economical choice for use in industrial production processes.

Advanced Materials Research, 2012

This work details the characterization of anatase nanoTiO2particles synthesized from Malaysian mi... more This work details the characterization of anatase nanoTiO2particles synthesized from Malaysian mineral precursors using the XRD and EDXRF. The properties that were analyzed were its crystallite sizes, relative crystallinity, phases, and chemical composition. It was determined that the crystallite size was quite small (15.6 nm), although the crystallinity of the sample is relatively low. The anatase phase seems to be dominant (100%), although in some cases when the processing parameters were changed or heat treatment were conducted, the existence of rutile is detected. The chemical composition showed that TiO2is the majority compound in the sample (~96%), although some metallic and non-metallic impurities are present (Zr, Nb, and S). It is concluded that Malaysian mineral precursors are capable of producing relatively high quality nanoTiO2.

36th International Electronics Manufacturing Technology Conference, 2014

The microstructural and mechanical properties of Sn-3.0Ag-0.5Cu lead-free solders added with a po... more The microstructural and mechanical properties of Sn-3.0Ag-0.5Cu lead-free solders added with a porous Cu interlayer were investigated. Two types of porous Cu, P15 and P25 with the diameter of ϕ1.7 mm and ϕ1.0mm respectively were used in this study. The porous Cu was arranged in a sandwich-liked layer in between Sn-3.0Ag-0.5Cu solder alloys with rod Cu as a substrate metal. Solder joint without porous Cu interlayer were also prepared as the control sample. Three soldering temperatures of 267ºC, 287ºC and 307ºC with soldering time of 5 minute were applied. Tensile test was performed to evaluate the joint strength of the solder alloy. The result shows that the joint strength increased proportionately with increasing soldering temperature and smaller pore size of porous Cu. Microstructure and fracture surface were observed by using optical microscopy (OM) in order to understand the failure behavior of the joint. It is found that penetration of molten solder alloy into the various pore sizes of porous Cu interlayer significantly influenced fracture morphology and strength of the joint.

Surface and Coatings Technology, 2013

Highly oriented titania nanotube arrays are formed by self-organizing anodization of Ti foil in o... more Highly oriented titania nanotube arrays are formed by self-organizing anodization of Ti foil in organic electrolytes in the presence of fluoride ions. The effects of tube length and the tube wall stratified layer on the electrochemical capacitance of these bamboo-type nanotubes are investigated. Field emission scanning electron microscopy (FESEM) is used to characterize the surface morphology, while cyclic voltammetry is used to investigate the pseudocapacitive properties of these nanostructured electrodes. The bamboo-type titania nanotube array with a higher aspect ratio shows a higher specific capacitance value of 52 μF cm -2 in 1 M Na 2 SO 4 with excellent reversibility characteristics. The introduction of surface defects by annealing in NH 3 increased the specific capacitance value to 118 μF cm -2 . This simple and cost-saving binder-free electrode is considered a promising candidate for supercapacitor applications.

Ceramics International, 2014

Porous three-dimensional hydroxyapatite (HA) scaffolds were prepared using bovine cortical bone d... more Porous three-dimensional hydroxyapatite (HA) scaffolds were prepared using bovine cortical bone derived HA (BDHA). Analyses of the morphology, chemical composition, and phase purity of the scaffold were performed using scanning electron microscopy (SEM), micro-computer tomography (micro-CT), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). SEM images revealed the rough and porous surface of the scaffold, while micro-CT showed the average porous volume of 76.7 70.6% and pore size of 0.04-0.25 mm. Single phase corresponding to standard HA was observed using XRD, and FTIR confirmed the presence of functional groups similar to HA. The EDX analysis revealed a Ca/P ratio of 1.61, which was comparable with HA stoichiometry. Compressive strength of the BDHA scaffold was found to be 1.37 0.09 MPa. After 14 days of human bone marrow stromal cells (hBMSCs) seeding, SEM and confocal analysis revealed cell attachment to the surface and infiltration into the pores. Alamar blue and alkaline phosphatase assays showed significantly increased cell proliferation and differentiation in the BDHA scaffold, when compared with that in the monolayer (p o0.01). In addition, quantitative real-time polymerase chain reaction (qPCR) data confirmed the up regulation of genes involved in osteogenic differentiation of mesenchymal stem cells. Our findings indicate that BDHA scaffold provides a favorable physiological environment for enhanced cell attachment, proliferation, and osteogenic differentiation of hBMSCs.

Arabian Journal for Science and Engineering, 2012

A nano-titanium dioxide (nano-TiO 2 ) powder, with Zr (0.5-1 %) and Nb (0.5-1 %) impurities, is f... more A nano-titanium dioxide (nano-TiO 2 ) powder, with Zr (0.5-1 %) and Nb (0.5-1 %) impurities, is fabricated using a modified hydrothermal method, with lowgrade mineral precursors. Samples were then sintered at 600, 800, and 1,000 • C, then analysed using XRD (crystallite size and phase conversion temperature), scanning electron microscope (SEM) (morphology), N 2 adsorption-desorption isotherms (surface area), and UV-vis-NIR (absorbance and optical transmission) to study the effects of sintering on the structural and optical properties of the synthesized nanopowders. It was discovered that sintering to 1,000 • C reduces the surface area by 99 %, and increases the crystallite size by almost 2,000 %. Meanwhile, the phase conversion temperature of this sample is 33.3 % higher than that reported in the literature for 600 • C. SEM shows an extensive agglomeration and uneven distribution of nano-TiO 2 particles before sintering. However, the sintered sample shows uniformity in particle size and distribution, and even though it is reduced significantly, agglomeration is still present. The absorbance of the samples is red-shifted towards the visible region (i.e., 380-700 nm), with the optical band-gap reduced by 10 %,

Development of Magnesium-Doped Biphasic Calcium Phosphatethrough Sol-Gel Method

IFMBE Proceedings

ABSTRACT Calcium phosphate is an interesting material for bone implant applications, as it shows ... more ABSTRACT Calcium phosphate is an interesting material for bone implant applications, as it shows biocompatibility and bioactivity to tissue bone. Among calcium phosphate-based materials, biphasic calcium phosphate (BCP), a mixture of non-resorbable hydroxyapatite (HA) and resorbable tricalcium phosphate (TCP), has shown to possess unique characteristics appropriate for bone replacement. Doping of magnesium ions into BCP will bring biological improvement. Magnesium ion was found to cause the acceleration of nucleation kinetics of bone minerals. Magnesium depletion adversely affects all stages of skeletal metabolism, leading to decrease in osteoblastic activities and bone fragility. Therefore, the incorporation of magnesium ions into the calcium phosphate structure is of great interest for the development of artificial bone implants. Here we present magnesium-doped biphasic calcium phosphate (Mg-BCP) using chemical doping process through a solgel method. Mg-BCP was produced using calcium nitrate tetrahydrate and di-ammonium hydrogen phosphate as the precursors for calcium and phosphorus, respectively. Magnesium nitrate was used as the source of the dopant. An ammoniacal solution of the monomers was heated until a white gel was obtained. The obtained gel was then dried and subsequently subjected to calcinations. The change in physicochemical properties has been evaluated by using XRD, FTIR, TG/DTA, and FESEM. Individual particles are of less than 100 nm in size, spherical shapes and tightly agglomerated. XRD measurement shown that the powder is Mg-doped BCP with 100% purity, and crystallinity increased with increased of Mg content. FTIR spectroscopy measurement also showed that the increment of crystallinity is directly proportional to the amount of dopant leading to the conclusion that magnesium acts as a sintering additive. This result is in good agreement with the analysis of FESEM where the particles of the Mgdoped BCP are larger as the amount of dopant increased as a result of more progressive fusion of particles.

Optimizing the cutting parameters for better surface quality in 2.5D cutting utilizing titanium coated carbide ball end mill

International Journal of Precision Engineering and Manufacturing, Nov 29, 2012

Novel uses of SiO2 nanolubrication in end milling of medium carbon steel for higher compressive residual stress measured by high-energy X-ray diffraction data

Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, Oct 13, 2015

Milling is a machining process that removes any desired material from the surface by using relati... more Milling is a machining process that removes any desired material from the surface by using relative motion between a work piece and a rotating cutter where the cutting tool intermittently enters and leaves the work piece. The milling process operates in two modes, namely, conventional (up) mode and climb (down) mode. Both modes are known for their significant effects on surface integrity due to the entering movement of the cutting tool and the formation of the chips during cutting process. Use of flood lubrication can improve the residual stress and surface quality of the component. It controls the temperature in cutting zone, reduces the power required, washes away chips, and reduces friction between chips, tools, and workpieces. Moreover, it has a great effect on the environment too. Minimum quantity lubrication can be used as an alternative of lubrication for clean machining. With an addition of nanoparticles into the minimum quantity lubrication, it is expected to enhance the machining performance that meets the environmental friendly purposes. Residual stresses remain in a solid material in the absence of external loading or thermal gradients, which is sometimes undesirable. The presence of compressive residual stresses is beneficial, while the presence of tensile stresses is detrimental. In order to study the residual stress and its relation with the surface quality (after milling process), the effects of reduced oil consumption in minimum quantity lubrication and the addition of SiO2 nanoparticles in minimum quantity lubrication for clean machining are presented in this research. Results indicate that there is an improvement in residual stresses and surface quality especially during conventional (up) milling under minimum quantity lubrication and minimum quantity lubrication–SiO2 nanolubrication condition.

Enhanced surface roughness of AISI D2 steel machined using nano-powder mixed electrical discharge machining

The International Journal of Advanced Manufacturing Technology, 2017

Conventional methods of building CNC machine tools involve using linear motors and ball screw dri... more Conventional methods of building CNC machine tools involve using linear motors and ball screw drives to obtain table motion. The double opposite sync motion design is an improvement over traditional CNC machines. In this work, an enhanced CNC gantry machine design is proposed, which exhibits a double motion mechanism. The new design is based on a rack and pinion system such that both the gantry tool and worktable are movable. The gantry's natural frequency was designed at 202 Hz in the first vibration mode, enabling it to work at higher speeds of up to 11,530 rpm, which makes the gantry suitable for both rough cutting and fine finishing. A prototype of the multi-mode motion CNC gantry milling machine was developed to investigate the machining performance and efficiency of the double opposite sync system. Performance analysis was done using ball bar precision tests on the different modes of CNC gantry operation. Validation tests were carried out to determine the effects of the motion of the machine parts on the dimensional accuracy and surface finish of the machined parts. The results indicated that the straightness of the developed machine was reduced from 176.3 to 114.6 μm, which occurred due to the reduced total distance travelled by the tool and worktable. Moreover, the circularity increased from 338.7 to 667.0 μm. This increase could be attributed to the combination of errors arising from both the gantry and table.

PLOS ONE, 2015

Titanium carbide-graphite (TiC/C) composite was successfully synthesized from Ti and C starting e... more Titanium carbide-graphite (TiC/C) composite was successfully synthesized from Ti and C starting elemental powders using self-propagating high-temperature synthesis technique in an ultra-high plasma inert medium in a single stage. The TiC was exposed to a high-temperature inert medium to allow recrystallization. The product was then characterized using field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Rietveld refinement, nanoindentation, and microhardness to determine the product's properties. The recorded micro-hardness of the product was 3660 HV, which is a 14% enhancement and makes is comparable to TiC materials.

Optimizing the cutting parameters for better surface quality in 2.5D cutting utilizing titanium coated carbide ball end mill

International Journal of Precision Engineering and Manufacturing, 2012