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- PublicationA study of punch-die misalignment in square cup deep drawing process using experiment and finite element analysis(2022-09-01)Abdul Ghafar, AlimiSquare deep drawing is a forming process that transforms a flat sheet metal to a seamless vessel by using a set of punch and die. Any misalignment in the punch -die assembly during the process can cause thinning, which can result in the tearing of the drawn part. The onset of thinning due to punch-die misalignment is yet to be explored fully, thus understanding the thinning initiation will be useful for process optimization. In this study, a series of comprehensive methods to identify the presence of punch-die misalignment in square cup deep drawing process is implemented. These methods are deployed at the pre-drawing, during the drawing process and at the post drawing stage. In the pre-drawing stage, an image processing technique is utilized forpre-drawiing inspection. The captured images are analysed to identify the severity of misalignment between the punch and the die. At the second stage (during forming), an in-situ method is used to observe the presence of punch-die misalignment. For this purpose, a customised die rig is fabricated and installed on a universal tensile machine (UTM). A Commercial Electrolytic Zinc-Coated Steel Sheet (SECC) was used as the specimen for the deep drawing process, and the effect of misalignment severity on drawing force and wall thickness distribution are investigated. For comparison, a finite element (FE) simulation is utilized as an early prediction of the punch-die misalignment. The simulation was conducted using Abaqus/Explicit FEA software, utilitising the Hill’48 model, to determine the stress-strain diagram and forming limit diagram (FLD) of the SECC material. Two conditions of misalignment were simulated, 1) single axis punch-die misalignment and 2) multi axes punch-die misalignment with the misalignment severity of 0.1 mm to 0.5 mm. At the post-drawing stage, the wall thickness distributions of the cup for each misalignment conditions were investigated. Variations in wall thickness distributions would indicate the severity of misalignment between the punch and die. Specifically, a novel methods are introduced for detecting the presence of punch-die misalignment in square cup deep drawing process. Both the FE and experimental results were in good agreement with regard to the drawing forces and thinning patterns due to punch-die misalignment. Greater misalignment severity was observed to increase the drawing force and thinning in the wall of the drawn cup. For both misalignment conditions, similar wall thickness distribution patterns were observed, with the maximum thinning occurring in the cup sidewall and minimal thinning at the bottom of the cup. For single axis misalignment, the maximum thickening up to 18% has occured at the lowest misalignment severity of 0.1 mm. On the other hand, for misalignment severity of 0.3 mm and above, the maximum thinning in the x-axis was higher as compared to the y-axis by average of 0.53% and 1.72% based on FE and experimental results, respectively. For multi axes misalignment, the maximum thickening averages at 15%, while the thinning was more pronounced in the rolling direction as compared to the transverse direction. As a conclusion, this study had contribute a positive signification implication in die making, especially punch-die alignment issue in deep drawing process. Alignment punch-die is essential in square cup deep drawing process. A series of comprehensive approach for identifying punch-die misalignment issue according to this study can be referred by researcher and industrial practioner in making high quality square cup deep drawn product.
- PublicationA study on low temperature synthesis of silicon carbide thermionic cathode and its electron emission analysis for thermionic energy converter(2020-07-01)Leong, Thye JienEnergy conversion of renewable and clean energy such as thermal energy is often related to solar cell and photovoltaic cell. These are the rising technology devices that generate electrical energy for the use in industrial and residential sectors. In order to seek for an alternative approach in meeting the growing energy demand and reducing the dependency on conventional energy resources such as biomass energy, another direct thermal energy to electricity conversion device namely Thermionic Energy Converter (TEC) is being studied. However, the technology involved in this device has one major limitation which is the unavailability of low cost cathode materials with low work function yet easily-obtained. This drawback has motivated the study of cathode material in term of lowering the work function by surface nanostructuring the thermionic cathode for TEC in the mentioned research direction. By using atmospheric pressure chemical vapor deposition (APCVD) method, a low temperature (600°C) synthesis thermionic cathode was developed, as validated by the literature (Xi et al., 2006). In this approach, silicon carbide (SiC) nanostructures were synthesized on the silicon substrate. This method was optimized based on two parameters which are controlling the thickness of catalyst (Magnesium) and the amount of precursors (silicon tetrachloride and 2-ethoxyethanol) used in the experiments. Some material characterization techniques, such as SEM, EDX, and FESEM were performed to the thermionic cathode to support the proposed synthesis method. Besides, a new in-house built TEC system that is equipped with a vacuum chamber, CO2 laser heating system, turbomolecular pump, and digital nanoammeter was developed, which can manipulate temperature of the thermionic cathode. The electron emission analysis of thermionic cathode was performed at different temperature ranges where a copper plate (4.7eV) was used as the anode. Based on the results, a total reduction of ~0.36 eV to the work function of the p-type silicon (111) with ~4.84 eV is achieved by the as-synthesized SiC nanowires thermionic cathode using M200SC3 - ~4.48 eV sample. Lastly, the Schottky effect is proven showing an enhancement to the current density of the SiC nanowires thermionic cathode by compromising a small deviation of the work function of ~0.02 eV. These findings prove that the presence of SiC nanostructures on the thermionic cathode has achieved higher current density, 87 nA cm-2 with the presence of applied voltage at 4000 V/cm and 71.8 nA cm-2 at zero field effect, as compared to 14.4 nA cm-2 for the control sample in this TEC study.
- PublicationAnalysis of void formation for no-flow underfill process using numerical simulation and machine learning-based methods(2022-09-01)Nashrudin, Muhammad NaqibThe no-flow underfill process has been developed as an alternative to the conventional capillary flow underfill. It offers low cost and lead time production effectively due to the integration of simultaneous reflow of solder interconnect and cure of underfill material. Somehow, no-flow underfill also faces the same reliability issue which is the potential void formation during the process. The research on the void formation issue in no-flow underfill has been found scarce. In addition, the research works on no-flow underfill focused on the experimental method which is costly and very limited to study the root cause of the issue. Therefore, this research presents a numerical simulation study of the no-flow underfill which has the ability to track dynamically the movement of the flow of underfill in real time during the process. This research investigates and predicts the possible void formation of no-flow underfill. Three major parameters were selected to align with industry requirements which are chip placement speed, bump pitches and viscosity of underfill. Subsequently, previous literature of no-flow underfill experiment, industrial no-flow underfill experiment and current scaled-up imitated flip-chip experiment were compared in term of flow and void formation percentage to validate with the current numerical simulation. Overall, the current numerical simulation produced low discrepancy which is less than 15% error among all the experiments and affirmed the capability and accuracy of the numerical simulation model. It was found that the void formation rate increases with the chip placement speed but decreases with the increase in bump pitch. The highest chip placement speed of 14 mm/s produces 4-6% meanwhile, the low chip placement speed (2-5 mm/s) produces around 2-3.5% of void formation. Moreover, several supervised machine learning prediction-based methods such as linear regression, decision forest regression and neural network regression were implemented to train the numerical values and to investigate further the most significant parameter that affects the void formation in the chip. It is observed that linear regression, decision forest regression and neural network regression produced mean absolute errors between 0.1588, 0.176375, and 0.1818, respectively. The neural network regression is the preferred algorithm method of machine learning in the study since it shows the least error with a high R2 value of 0.95159. Based on permutation feature importance, the most significant parameter that affect the formation of void in the no-flow underfill was chip placement speed compared to bump pitches and underfill’s viscosity with a score of 1.7916, 0.2962 and 0.000878, respectively. This research provided engineers in the microelectronic industry with a deep understanding of the void formation and expected to provide an appropriate guide to minimize the failure for the development of no-flow underfill in the future.
- PublicationBio-based and hybrid based polymer composites for enclosures of memory storage device application(2022-08-01)Janakiraman, Vishnu ChandarA large proportion of consumer electrical and electronic packaging applications were made up of thermoplastics. Casings or enclosures are generally used in circuit boards, and data storage which is made up of plastic to ensure the appliances are mobile, lightweight while being tough and durable and at the same time, the plastics used in these applications are very high and also not biodegradable. This research aims to reduce the usage of plastics in storage applications via two approaches, i.e., bio-based and hybrid-based polymer composites. In this work, pure polymer [polylactic acid (PLA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), cellulose acetate (CA)] and its bio-based composite ((PLA/Aluminium oxide (Al2O3)/Boron Nitride (BN)), PLA/BN/Graphene tubes (GT), PHBV/Al2O3/BN, PHBV/BN/GT, CA/Al2O3/BN, CA/BN/GT) sheets with different concentration of hybrid filler [(Aluminium oxide (Al2O3)/Boron nitride (BN), BN/Graphene tubes (GT)] were fabricated. Similarly, pure thermoplastics (polyoxymethylene (POM), polypropylene(PP), polycarbonate (PC)) and its hybrid-based composite POM/PHBV/Al2O3/BN, POM/PHBV/BN/GT, PP/cellulose fiber (CF)/Al2O3/BN, PP/CF/BN/GT, PC/basalt fiber (BF)/Al2O3/BN, PC/BF/BN/GT) sheets with different concentration of hybrid fillers were fabricated using internal mixer equipment and compression molding method. The effect of fillers on the structural, optical, thermal, thermophysical, mechanical, surface, electrical properties of the pure polymer and its bio-based and hybrid-based polymer composite sheets were studied, compared, and suggested for electronic packaging applications. XRD results confirm the presence of polymers and fillers (ceramic, carbon, and natural) in the prepared bio-based and hybrid-based composites. The prepared bio-based (PLA/BN/GT, PHBV/BN/GT, CA/BN/GT) and hybrid-based (POM/PHBV/BN/GT, PP/CF/BN/GT, PC/BF/BN/GT) polymer composites exhibit high UV-VIS-NIR absorption, thermal conductivity (0.29 - 0.51 W/mK and 0.35 – 0.53 W/mK), flexural strength (34.2 – 66.4 MPa and 59.1 –74.8 MPa), flexural modulus (1088 – 3239 MPa and 1313 – 3424 MPa), storage modulus (726 – 2130 MPa and 1492 – 3132 MPa), scratch hardness (0.43 – 0.73 GPa and 0.44 – 1.19 GPa), and low CTE (17 - 42.9 µm/m ºC and 38.6 – 114 µm/m ºC), ESD (<10V to <100V and <10V) compared to composites with Al2O3/BN filler and pure polymer that may be due to the high thermal conductivity, mechanical strength and synergetic effect of BN and GT filler. As for dielectric permittivity, Al2O3/BN reinforced composites exhibit favourable dielectric constant (3.02 - 4.74 and 2.72 –3.37) and loss (< 0.02), whereas BN/GT reinforced polymer composites shows higher values at a lower frequency. Like bio-based, hybrid-based polymer composites also follows the same trend in dielectric permittivity. On comparing the bio-based composites, CA/BN/GT polymer composites are suitable for USB products with high storage capacity as per the obtained melting, glass transition temperature, CTE, ESD, mechanical, and scratch performance, whereas PLA/BN/GT and PHBV/BN/GT polymer composites are suitable for USB products with very low storage capacity and can ultimately reduce 98% of plastics. Similarly, the prepared hybrid-based polymer composites (POM/PHBV, PP/CF, PC/BF) with BN/GT filler are suitable for USB, SSD, and HDD products with both low and high capacity as per the obtained thermal, ESD, mechanical, and scratch performance and can ultimately reduce 15-40% of plastics in enclosure applications.
- PublicationDiscrete phase model simulation and optimization of different types nano-reinforced solder fillet using taguchi analysis and neural network method(2021-12-01)Muhamed Mukhtar, Muhamed Abdul FatahRecently, the electronic industry required electronic components to become reliable, lightweight, and miniature. In order to ensure the functionality of electronic devices, advanced joining through the nano-reinforced solder material was required. In previous studies, the addition of different types of nanoparticles to lead-free solders has been studied. One of the strengthened elements added, such as NiO and TiO2, helps the solder fillet to have better mechanical properties. Nevertheless, there is still a large research gap in the miniaturized part assembly processes through nano-reinforced solder paste on the actual surface mount devices. Hence, this research aims to investigate the advanced joining of ultra-fine packages using the nano-reinforced solder paste. Nanoparticles material name, TiO2, Fe2O3, and NiO with (0.01wt. %, 0.05 wt. %, and 0.15 wt. %) were selected to be reinforced with lead-free solder paste (SAC 305 type 5) to form three different types of nanoparticles samples. The nano-reinforced solder paste was contrasted with the pure SAC305 solder paste in terms of material and mechanical properties. In the current analysis, a two-way interaction is implemented using both the fluid volume method (VOF) and the disperse phase method (DPM) to account for the interaction between both the nanoparticles and the molten solder. DPM simulation is capable of viewing the comprehensive trajectory of nanoparticles as it undergoes thermal reflow from SAC305 based on the comparison of the simulation the experimental result. Additionally, for all cases of nanoparticles being used, strong agreement can be seen between both experimental and simulation data collected. By using different experimental techniques, the microstructure, fillet height, hardness and Modulus Young were investigated. The experimental results showed that the presence of nanoparticles generally strengthened the ultra-fine solder joint's material and mechanical properties. The reflow soldering process parameters were optimized by Taguchi technique based on Taguchi’s L16 orthogonal array. The optimum weighted percentage and nanoparticle material types were determined, and their percentage of contribution was estimated by applying the signal-to-noise ratio and analysis of variance. By adding 0.15 wt. % of TiO2, Fe2O3, and NiO, respectively, it increased the hardness and shear strength of the solder joint. The optimal configuration and the highest mean value of hardness and the modulus Young were obtained by 0.15 wt. % of SAC305+TiO2 nanoparticles were0.2875GPa and 89.65GPa. Meanwhile, optimal configuration and the highest mean for fillet height were obtained by 0.05 wt. % of SAC305+NiO nanoparticles was 0.1719mm. Quasi Newton method of Neural Network (NN) was used to train the experimental values. In comparison between experimental and neural network model results, the percentage error of predictive models for fillet height, hardness, and modulus Young were -0.046% , 1.077% ,and 20.420 %. This research provides engineers with a deep understanding of the ultra-fine package features of the nano-reinforced solder joint in the microelectronics industry. The results are expected to provide an appropriate guide and reference for the electronics industries in order to develop nano-reinforced solder joints of miniaturized electronic packages in the future.
- PublicationEffect of aperture filling parameters of solder paste on stencil printing process(2020-05-01)Rusdi, Mohd SyakirinThe stage that causes major concern compared to the other stages in Surface Mount Technology (SMT) is known as the stencil printing stage. The study of pre-stencil printing is performed using simulation software to minimize fabrication costs and time. Therefore, this research focuses on the 3D simulation of aperture filling using lead-free solder during the stencil printing process via the usage of CFD simulation. The aperture filling of a solder paste at a varying squeegee pressure, squeegee speed and separation speed were studied using a commercial solder paste printer (DEK 265), and a 3D solder paste scanner (KOH YOUNG Aspire 2). A PCB that measures at 183 mm × 133 mm with 2 mm thickness was used in the experiment. Optimization of the process was done via Response Surface Methodology (RSM) where optimum solder filling volume, solder paste height and solder area coverage were obtained during the printing process. The optimum values suggested by RSM were squeegee pressure = 0.69 MPa, squeegee speed = 35 mm/s, and separation speed = 0.498 mm/s, and the optimal responses were volume = 0.783 mm3, height = 0.121 mm, and area = 6.481 mm2. The optimized parameters then were used as the validating data to carry out other extending studies. Anton Parr Physica MCR 301 Rotary Rheometer machine was used to conduct experiments on solder paste rheology (shear rate and viscosity). Parallel-plate (PP) and Cone-plate (CP) spindle were used to carry out five different tests consisting of different spindle type and setting. The volume filled under different squeegee speeds found that PP of 0.5mm gap exhibited the lowest average discrepancy value at 5.4% while CP1° and PP 0.5mm at 11.6% for different aperture sizes. The average discrepancy was the comparison between experiments and simulations results. Then, the studies were further extended to simulate the stencil printing process by using ANSYS Fluent 19. VOF method with Cross viscosity model was selected to undergo the numerical simulation. The volume filled by the solder paste at different aperture size according to the experiment and simulation results were compared. For different aperture size, all the results showed a similar trend with an average discrepancy of 11.6%. Furthermore, another study was added to investigate the stencil printing process efficiency at different squeegee speed and aperture size. The performance of the solder pastes for stencil printing is then compared with different lead-free solder paste (SAC105, SAC307, SAC305, SAC405 and SN100C). Leaded solder paste (Sn62Pb36Ag2) was also included in the analysis to demonstrate how well the lead-free solder pastes perform in comparison to the leaded solder paste. The research results were analyzed by comparing the effects of different angles, stencil thickness and aperture size. Results showed that the SAC305 gives the best result compared to other lead-free solder pastes and also leaded solder paste.
- PublicationEffect of sintering temperature on the properties of magnesium substituted biphasic calcium phosphate(2020-05-01)Marahat, Muhammad HanifBiphasic calcium phosphate (BCP) is a bioceramic material which are known to have two distinguish phases which is hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP). The aim of this research is to improve the limitation in mechanical properties of BCP by the addition of 0.025 wt% of Mg. The addition of Mg was able to increase the densification of BCP by stabilizing the β-TCP phase and delay the formation of α-TCP at high sintering temperature. Therefore, this study emphasizes on the effect of Mg substitution on BCP upon densification through sintering process. BCP and MgBCP powder was synthesized via wet precipitation method using the ratio of (Ca+Mg)/P 1.61. The obtained as-synthesized powder was pressed in pellet shape and sinter at temperature 900oC, 1000oC and 1100oC. The analysis is separated into two part which covers the unsintered as-synthesized powder and sintered pellet. The as-synthesized powder shows that Mg substitution improved the crystallinity peak from XRD analysis. For sintered pellet, the result for porosity of BCP have shown that the porosity of BCP have decreases from 40% at 900oC to 25% at 1100oC respectively. The trend also decreases as Mg was added, from 39% (900oC) to 22% (1100oC). Moreover, the result for mechanical testing shows that the MgBCP pellet is having higher mechanical strength compared to BCP pellet. The highest compressive strength for BCP pellet is at 5.02 MPa and MgBCP is at 9.41 MPa. The same trend with Vickers hardness testing which record BCP (0.82 GPa) and MgBCP (0.93 GPa). Overall trend shows that sintering at 1100oC gives better mechanical strength. Moreover, in term of biological analysis, MgBCP pellet gives more formation of apatite layer on its surface under FESEM observation due to more dissolution process for apatite to growth.
- PublicationEnhanced liquid mixing in 2d channel with different fin configurations(2022-08-01)Tan, Sak JieIn microfluidic devices, narrow channels lead to low Reynolds number flows, thereby restricting the fluid flow in a laminar flow condition, a long mixing channel length is thus needed to achieve a complete mixing. The research on liquid mixing enhancement in the channel shall be explored to reduce the required mixing length. The assessment of liquid mixing in the channel was performed to investigate the fluid flow in the channel with augmented design. The experiment on channels with the augmented designs was performed in the study to mimic the mixing behavior in the channel. The combination of different inlet designs, for example, Cross-inlet and T-inlet integrated with staggered fins, were modelled to numerically investigate the mixing performance. It is found that the implementation of obstacles within the channel can significantly enhance the mixing performance. The numerical investigation on the effects of geometric parameters and flow parameters on the Cross-mixer and T-mixer were performed in this study. Several fin arrangements, such as staggered fin arrangement, in-line fin arrangement, and Tri-fin arrangement on T-mixer, were proposed to enhance the mixing performance on the mixer. At 𝑥/𝐻 = 10, 𝑀 of 0.8905 is attained with staggered fin arrangement. Meanwhile, 𝑀 = 0.8509, 0.8498, and 0.7443 are yielded with in-line fin, Tri-fin and basic mixer, respectively, at the same axial position. Among these designs, T-mixer with staggered fin arrangement yielded the best mixing performance, in the practical range of Reynolds numberinvestigated. Besides, the comparison between Cross-mixer and conventional mixers was also examined. The results show that well-mixed fluid can be achieved with only a one-quarter channel length using Cross-mixer as compared with conventional mixers (T-mixer and Y-mixer) under the same flow condition. The correlation equation for T-mixer and Cross-mixer is proposed to predict the mixing length based on the Péclet number. The correlations are in good agreement with the simulation results. The effect on Péclet number and the validity of 3D mixers were also presented to validate the proposed correlations. Apart from that, the proposed correlation equation for Cross-mixer is validated by comparing the experimental results of the Cross-mixer at Re = 12 to 67. The correlation formulation proposed is found to be in good agreement with the experimental results. The deviation between numerical simulation and proposed correlation for T-mixer and Cross-mixer are 1.69 % and 0.89 %, respectively. These correlations shall be useful for researchers in predicting the mixing length without the need to perform numerical simulation.
- PublicationInversed unnormalized distance-weighted k-nn: a kinect human motion classification model based on skeletal joints features(2021-12-01)Lee, Pui YiHuman motion (HM) classification remains an active research field due to its wide applications in surveillance, robotics and medical disciplines. HM is commonly recognized from skeletal joint (SJ) coordinates extracted from videos, images sequence, or marker-based motion capture devices. Microsoft Kinect V1 (MKV1) is among the frequently used tool for its low-cost and capable marker-less motion tracks via sensors. Its datasets were captured in image sequence or video output at 30 fps recorded in RGB (red, green, blue) format, depth images, and SJ data (text file) forms. The SJ data includes coordinates for 45 (3D 15 joints) or 60 (3D 20 joints) (features × the total action captured). Previous studies have revealed that MKV1 is a reliable tool having excellent test-retest reliability, and valid for HM patterns assessments based on SJ detection. MKV1 dataset’s big dimensionality requires efficient Feature Selection (FS) analysis to achieve high classification efficiency in a short running time. Nevertheless, no study has applied FS based on Cronbach’s alpha analysis despite wide growth in FS algorithms’ applications. Additionally, previous works which considered the human SJ suffers from low classification accuracy and inconsistent performances across MKV1 datasets. Therefore, the present study aims to assess the reliable SJ indicators captured in MKV1, to determine the optimal subset of SJ for human motion FS, and to develop a human motion classification model of high accuracy and lowest running time. Each dataset’s reliability analysis was established on three indicators: internal consistency, inter-rater reliability, and intra-rater reliability. FS (FSSJFCA) was performed using the exhaustive search strategy and hybrid method. Filter was initially applied to obtained SJ feature combination based on Cronbach’s alpha reliability indicator for subsequent cross-validation mode classification. The Inversed Unnormalized Distance-Weighted k-NN classification algorithm was developed to segregate Kinect SJ data into motions’ classes. The strategy was deployed on three case studies: two datasets from public domains (UTKinect-Action3D and Florence 3D Actions) and an experimental dataset (USMKinect) involving nine to 16 simple daily HM activities. Findings show that the FSSJFCA improves classification accuracy (reduces total runtime) by 0% (54.63%), 0.1% (25.56%) and 0% (52.69%) in UTKinect-Action3D, Florence 3D Actions, and USMKinect dataset, respectively. The Inversed Unnormalized Distance-Weighted k NN developed achieved classification accuracy above 98% at a low total runtime ((2 - 3 seconds) and (40 seconds) for (31 × 6028) and (31 x 30693) dimension Kinect HM dataset respectively). The newly developed model, a combination of FSSJFCA and Inversed Unnormalized Distance-Weighted k-NN, outperformed 11 existing algorithms applied to UTKinect-Action3D and/or Florence 3D Actions datasets by 0.49% to 17.87% classification accuracy. The newly developed model has high practicability to classify human motion applicable in Artificial Intelligence, Machine Vision, Biomechanics, Image Processing, and Pattern Recognition.
- PublicationInvestigation of tribological properties and engine performance of tire pyrolysis oil for diesel engine applications(2022-03-01)Yaqoob, HaseebThe application of tire pyrolysis oil (TPO) as an alternative fuel has attained attention owing to the exponentially raised demand and price of fossil fuels, environmental impacts, and landfilling of the waste tires. Globally, the pyrolysis process has become the leading solution by converting the waste tires to the TPO. Waste tire pyrolysis oil was purified by using the distillation process. DT10 (Diesel 90%-TPO 10%), DB10 (Diesel 90%-Biodiesel 10%), and diesel fuel were used in this study. The experimental study was conducted to compare the combustion, performance, emission, and tribological characteristics. Furthermore, the comparative assessment of the energy, exergy, economic, and sustainability analysis of a diesel engine fueled with tire pyrolysis oil (TPO)-diesel blends was carried out by using the experimental data, and the findings were compared with biodiesel–diesel blended fuel and pure diesel. The engine was a four-cylinder four-stroke, turbocharged diesel engine, and the experiments were performed at different crankshaft speeds ranges 1000–3500 rpm with the increment of 500 rpm. Moreover, the tribological experiment study was conducted over 300 s at 40, 50, 63, and 80 kg load, 1800 rpm constant speed, and 27 °Ctemperature of all fuels on the ASTM D2266 standard. The results show that the cylinder pressure and heat release rate is comparable, especially at 3500 rpm. The torque, brake power, and brake thermal efficiency of DT10 is greater than the DB10 and diesel fuel due to its high calorific value and oxygen share. DT10 indicates the 3.3% and 4.2% reduction in nitrogen oxides (NOx) emission at 3500 rpm relative to diesel and DB10 fuel, respectively. Meanwhile, the highest reduction of 20.2% in smoke opacity was found using DT10 compared to diesel fuel at the engine speed of 2000 rpm. Subsequently, the results reveal that at 3000 rpm, DT10 shows the highest energy efficiency, 37.12%, and exergy efficiency, 39.6%, respectively. DT10 provides the lowest thermoeconomic parameters and highest sustainability index value 1.65. Furthermore, TPO demonstrated better antiwear behavior in terms of higher load]-carrying capacity as compared to diesel fuel. DT10 and BT10's wear scar diameter was 22.35% and 23.99% smaller than diesel and biodiesel, respectively at 80 kg load. Scanning electron microscope micrographs show that the TPO, DT10 and BT10 have less wear than the diesel fuel. Finally, it is concluded that the DT10 shows better tribological and engine performance results, so it is suitable as an alternative fuel for automotive applications.
- PublicationOptimization of customized twist drill geometry for single-shot drilling of composite-metal stack(2020-09-01)Hassan, Muhammad HafizDrilling a composite-metal stack in a single shot is a challenging process, as the drill bit needs to pass through two different materials in a short time. Currently, twist drill bit is widely used in the field of drilling due to its economical state. However, the existing twist drill bits exhibits quick wear and tear upon drilling stacked up plates. This leads to frequent drill bit replacement and thus incurring additional costs to the company. This issue is further exacerbated by the lack of knowledge on suitable drilling speed and feed rate during the drilling of stacked up materials. This study focused specifically on the optimization of customized twist drill bit geometry for the production of good holes quality during a singleshot drilling process of composite-metal stack materials. First of all, an initial study was performed to identify which geometries of the drill bit and drilling parameters influence the hole quality the most. This step involved drilling a stacked-up plate at different feed rates of 0.05 mm/rev to 0.1 mm/rev and spindle speeds of 1500 rev/min to 2600 rev/min using customized twist drill bit of different geometries. The geometries of the drill bit were varied based on its helix angle, primary clearance angle, point angle, and chisel edge angle. The performance of the twist drill bit was assessed based on the drilling thrust force, hole surface roughness, burr formation and hole integrity (delamination, diameter error and hole circularity). The results were subsequently evaluated using the analysis of variance (ANOVA) to determine the influence of the drill geometry and drilling parameters on the maximum thrust force and the quality of the drilled hole. The results from initial study indicated that the any interaction of drill geometry parameters with the 2600 rev/min and 0.05 mm/rev produced a good drilled hole quality. For the drill geometry parameter, the interaction with drilling at the helix angle of 30° contributed to minimum drilling thrust force, hole surface roughness, burr formation and good hole integrity. For the point angle parameter, drilling with 130° was proven to reduce the burr formation by 89%. Other parameters like primary clearance angle and chisel edge angle were further analysed in the extended study since both parameters have interaction with the other drilling parameters. Later on, an extended investigation was carried out to study the effect of drill geometry on thrust force and hole quality comprising of chisel edge angle, primary clearance angle, and point angle at helix angle of 30°, 2600 rev/min, and 0.05 mm/rev. Twenty different drill designs with varied chisel edge angle, primary clearance angle, and point angle were fabricated and tested on the drilling of stacked up materials. The range of point angle parameters was extended from 130° to 140° in order to observe the impact of hole integrity. From the extended study, the most significant parameter affecting the drilling thrust force and hole surface roughness is the primary clearance angle followed by the chisel edge angle. For burr formation, the most significant parameter is the chisel edge angle, followed by the point angle. Through statistical analysis, the selected optimum drill geometry angles that scored the highest desirability based on the helix angle of 30° and drilling at 2600 rev/min and 0.05 mm/rev were chisel edge angle of 45°, primary clearance angle of 6°, and point angle of 130°. The new optimum drill design was fabricated and followed by a set of validating experimental works that produced errors in range of 6.64% to 9.23% for maximum thrust force, hole surface roughness, and burr formation. This confirmed its validity. For the hole integrity, the delamination factor for all trial was observed in range of 1.0038 and 1.0196 and the hole circularity achieved below 30 μm for all trials. The current study provides practical guidelines for machinists in selecting the right geometry angles to achieve suitable design for customised twist drills which are not readily available from standard drill catalogue in the market.
- PublicationParametric analysis of the heat transfer behavior during the annealing process of the wafer vertical furnace(2022-05-01)Tan, Siew AunNowadays, the wafer fabrication process often demands energy efficient equipment. It is thus of great significance to study furnace process chamber key components of semiconductor diffusion equipment. A furnace running at 1123 K for the annealing process was studied both experimentally and numerically in the present study. The experiment was carried out on a vertical furnace which consists of a process chamber, quartz boat, pedestal, heater element, and 175 silicon wafers. Five zones of nickel-made thermocouples were used to measure the temperature in the furnace. Meanwhile, an infrared meter is used to measure the temperature at the process door and top header. In terms of thermal modeling of furnace, three-dimensional modeling was employed to simulate the annealing process in the vertical furnace that operates at temperature 1123 K. The numerical results have been validated and compared with experimental results, and the results show a good agreement. Among all five zones, the experimental study revealed that the bottom zone of the heater needs the highest power consumption of 70 % or equivalent to 18 kW of power consumption. The temperature difference between Spike and Profile temperature for the bottom one shows a difference of 74 K. Besides, the experimental works were also extended to explore the power consumption of two types of heater elements: standard heater and augmented heater with different ceramic insulation composition. Results show that the heater with higher consumption of Al2O3 for insulation ceramic material shows significant energy saving for the bottom zone with the maximum difference of 54 % or equivalent to 13.94 kW of power consumption. By utilizing the numerical model, the change of heater temperature, environment inert gas, and different flow rates of inlet gas study were examined in the present study. In addition, the influence of thickness of top header and process door is also evaluated. The results show that the bottom process door dissipates 33 % more heat than the top header of a furnace. The study on the wafer uniformity for different designs was conducted. Numerical results suggest that a furnace with a full boat cover design could yield better wafer temperature uniformity and thus more even temperature distribution could be attained along the stacked wafers. Moreover, the full cover design also gives a reduction of 28 % and 22 % heat loss through the top and bottom end of the furnace. In addition, a lower nitrogen flow rate would be preferred based on flow analysis from the simulation study. In summary, a thicker top header and a better thermal insulated process door with a full boat cover are suggested to reduce the heat losses in the semiconductor furnace.
- PublicationProfit optimization of preventive maintenance frequency, lot size and buffer for a two stages serial system(2020-05-01)Hwang, Jia QiIn the manufacturing industry, a complex and mutual relationship exists between the maintenance and production functions due to its shared resource consumption and the influence on profit. However, the assumptions of considering only one type of machine failures and good quality output during the in-control state affect the realism of a production model. The dependency between the machines in the multi-stages system and its impact on the production and maintenance planning are often overlooked as well. Hence, this research aims to optimize the number of Preventive Maintenance (PM) activities, lot size and buffer size for the machines in a serial configuration that has different characteristics using a profit maximization approach. A model was constructed in Discrete Event Simulation (DES) software, WITNESS Horizon 21.0. The production cost including the manufacturing cost and inventory cost, the maintenance cost of PM, minimal repair and restoration together with the losses due to defective output and lost sales are included in the profit maximization model. Then, the model was validated based on the data from a carton box production line followed by the optimization with WITNESS Experimenter. From the result of the numerical experimentation, the near-optimal profit point (5305.963k mu) is the result of the combination of 2200 units of lot size, 20 units of buffer size, seven PM activities for M1 and five PM activities for M2. This result is the second-highest profit in the exhaustive search of the decision variables. Moreover, the xperimentation time is 85.6% lower than the computation time of all the combinations of the decision variables. And so, the proposed model can be used as a guide for decision making involving maintenance and production in the industry for its capability to determine a near-optimal point at a shorter computational time than the time needed to simulate all the value of decision variables.
- PublicationSteam/co2 gasification of palm biochar using natural catalyst under microwave irradiation(2020-08-01)Ahmad, AzlinaStudies on the effect of steam as gasifying agent with CO2 in char gasification is an important mechanism in gasification for fuel gas conversion. The current work aims at mitigating CO2 as greenhouse gas (GHG) in char gasification with steam addition to improve char reactivity and produce combustible gases during gasification reaction. In this study, steam/CO2 mixture gasification reactivity of oil palm shell (OPS) char using microwave energy has been investigated. Microwave assisted steam - CO2 gasification was characterized in the temperature range of 700- 850°C and steam/CO2 ratio in the range of 0.014 - 0.043. Surface composition and morphology of char embedded with ash were examined at different temperatures using scanning electron microscope and energy dispersive spectrometry (SEM/EDS). Optimum operation was achieved at a steam/CO2 ratio of 0.028 and temperature of 850°C with 92% and 85% CO2 and char conversions, respectively. Increasing steam flow at maximum temperature increased the H2/CO ratio by 22% and synthesis gas (syngas) heating value by 6%. The catalysts loaded OPS char used natural catalyst produce from rubber seed shell ash (RSS- ash), bamboo whole ash (BW-ash) and corn cob ash (CC-ash), which are rich in potassium to enhance CO2 gasification reactivity of OPS char. The results show that the highest gasification reactivity was achieved for 6.5% BW ash loaded char. The GC and SEM–EDX analyses confirmed the successful loading of natural catalyst of 6.5% BW ash on OPS char which contributed to promoting the gas yield up to 98% from without them.
- PublicationStudy on space charge suppression for thermal electronic energy conversion(2020-07-01)Khalid, Kamarul Aizat AbdulElectricity may be produced in an efficient way from thermal energy sources using thermionic energy converters (TICs). Unlike conventional generators that utilize moving parts to generate electricity, TICs provide an opportunity for converting heat directly and statically by utilizing electrons as the working fluid. Despite having huge potential as an efficient direct energy conversion device, the development of TICs have been held back due to their low conversion efficiency. There are mainly two obstacles for achieving highly efficient TICs; the strict need for low emitter and collector work functions in order to achieve maximum conversion efficiency and the mutual repulsion of electrons within the inter electrode gap, known as the space charge effect. The space charge effect is the formation of electrons within the electrodes that dramatically reduces the current densities thereby disrupting the performance of the device. In this thesis, a new configuration has been proposed based on simulation of recent concepts that attempt to reduce or even eliminate the decelerating forces produced by the space charge cloud, namely the thermoelectronic energy conversion. This method uses an electrostatic field generated by a gate electrode to pull electrons away from the condensed space charge cloud. A magnetic field is also applied to guide electrons away from the gate electrode. Unlike the original scheme, this work will be focusing on improving the performance of thermoelectronic energy converters (TECs) with the intention of reducing the parasitic thermal radiation losses suffered in the current concept of TEC. This design will provide some modifications by intentionally making use of cylindrical geometric emitter coupled with rotor-like design collector to maximize the effective surface area to give more space and time for electrons to travel towards the collector and the electrodes do not have to be facing each other and the heat transfer will be minimized. Apart from that, accelerating gate electrodes will be inserted to attract electrons thus manipulating the pathways of electrons and reducing crossover between them. In this work, three dimensional (3D) simulations were generated and the electrostatic potential within the inter electrode space was calculated. Apart from that, the assessment of attainable output powers and efficiencies was accomplished in this work. An extrapolation of the system performance gives strong evidence that practically high output power densities and conversion efficiencies exceeding 10% compared to the previous system may be achieved if the requirement of low work function emitter and collector can be fulfilled.
- PublicationVertical line edge image-based fuzzy control of a two wheeled mobile robot(2020-09-01)Neoh, Hock SengCurrent research involving the use of edge images for fuzzy control of mobile robots are based on the utilization of steer angle magnitudes for actuation. This necessitates the fine tuning of the steer angle magnitudes to respond to certain feature points of its environment to perform a certain control action. This required training processes which could be time consuming. In this research, an edge image based fuzzy control system for a two wheeled mobile robot (2-WMR) which utilized the vertical line (VL) displacement was introduced. No fine tuning of the consequent sets was required. The steering control action was based on responding to the deviation of the VL in pixel counts. The standard deviation produced was 22-pixel counts from the center of the edge image. The tracks produced showed that the fuzzy control always directed the 2-WMR towards its landmark of interest in its various stages of movements. A fuzzy set with a threshold value determined the number of steps in each stage of movement. In addition, the fuzzy view descriptor was incorporated to provide the 2-WMR cognitive capabilities. The fuzzy view descriptor enabled the 2-WMR to ascertain its environment and select the appropriate VL at a certain stage of movement as a reference point to steer towards a landmark. A set of special registers determined the switching of the 2-WMR to consecutive view areas (VA). In this way the 2-WMR was able to steer from one landmark to another. Another novelty was the introduction of a new fuzzy edge detector to improve upon the conventional fuzzy edge detector. The new fuzzy edge detector demonstrated its improved robustness and efficiency to detect edges in various lighting conditions at various distances from the landmarks of interest. Since the new fuzzy edge detector maximizes the permutation of the masks in four direction, there was no need to further increment the fuzzy rules. This prevented the fuzzy rule explosion problem.