Pusat Pengajian Kejuruteraan Mekanikal - Tesis

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A Model For The Fuzzy Front End Of New Product Development Process
(2016-01)
Abd Rahman, Md Nizam
In general, New Product Development (NPD) methodology can be broken down into five phases, Strategic Planning. Idea Generation, Pretechnical Evaluation, Technical Development, and Commercialization. The first three steps are known as the front end and the last two are known as the back-end of the NPD methodology. The scope of this research work is limited to the first two steps of the NPD methodology, which are strategic planning and idea generation. The objectives of this research work are I) to piece together the various steps required in executing strategic planning process to ensure its effectiveness and 2) to define guidelines in selecting idea generation techniques that are suitable for a given set of conditions. Through analyzing case studies on thirty cornpapies that have been proven successful in NPD programs, the main factors that have significant impact on the success of NPD strategic planning process are verified and guidelines for selecting suitable idea generation techniques for a given set of conditions are developed.
Attenuation of humming type noise and vibration in vehicle hvac system using a tuneable dynamic vibration absorber
(2023-06-01)
Muhammad Safwan Bin Abdul Aziz
The purpose of this research is to study the effect of a Tuneable Dynamic Vibration Absorber (TDVA) in reducing the humming type noise and vibration that originating from the Heating, Ventilation and Air Conditioning (HVAC) system of a Proton Exora vehicle. In this study, a lab-scale experimental rig of Proton Exora HVAC system was built to represent the system inside the vehicle. On top of that, the study also been conducted on the Proton Exora vehicle itself for the data comparison. The TDVA was designed and tuned according to the natural frequencies of the Air Conditioning (AC) pipe structure obtained from Experimental Modal Analysis (EMA) of both the system and vehicle level with natural frequency values of 148 Hz and 173 Hz respectively. Two TDVA, with the length of 5.53 cm and 4.98 cm were fabricated and applied at both lab scale test rig and vehicle level, respectively. The humming type noise and vibration characteristics of the HVAC components were recorded and compared, with and without the implementation of TDVA. The implementation of TDVA into the system was found to reduce the vibration level of the AC Pipe by 80 % and subsequently reducing the noise and vibration level of the whole HVAC system inside the cabin area by 1.5 dBA. It also been observed that the applied TDVA has an effective frequency range of 100 – 500 Hz for the vehicle level and 75 – 250 Hz for the lab scale test rig.
Combustion characterization and optimization of mixture biomass producer gas and methane in a constant volume combustion chamber system for fuel combustion efficiency enchancement
(2023-03-01)
Teh Jun Sheng
Most of the world’s energy requirements are still derived from natural resources. This will result in a catastrophic energy crisis with negative environmental consequences. The increased energy supply will result in greater consumption of non-renewable sources. The production of biomass producer gas (BPG) from biomass gasification has received significant attention for reducing global emissions as an alternative fuel because of the depletion of non-renewable resources. The properties of biomass feedstocks significantly influence combustion characteristics. The objective of this experimental study was to determine the combustion characteristics: flame propagation speed, chamber pressure trace and emissions of BPG at different equivalence ratio to obtain the lower chamber peak pressure and greenhouse gas emissions. Using the direct visualization technique, an optical constant volume combustion chamber (CVCC) was developed to measure combustion characteristics. Liquid petroleum gas (LPG) was used to compare chamber pressure and flame propagation speed in the CVCC calibration. In comparison to wood pellet (WP), coconut husk (CH), and palm kernel shell (PKS), the chamber peak pressure at 𝜙 equal to 1 of CH for the combustion of BPG is the lowest at 20.84 bar. At 𝜙 of 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, and 1.3, the chamber peak pressure of CH was discovered to be around 17.77, 18.12, 18.81, 20.84, 20.39, 17.25, and 16.37 bar. Compared to the other two types of BPG, CH produces the lowest emission of CO2 and CO, at 2.03% and 0.02%, respectively. From the literature review, increasing CH4 content in the fuel can increase the mole fraction of H, O2, and OH radicals and reaction rates in the flame, further accelerating the flame of the mixtures. Therefore, an optimization study is needed to determine the higher performance combustion of BPG with an increase in the composition of methane. The combustion experiment study was optimized with 17 designed experiments, 0.9 to 1.1 equivalence ratio, and the 0 to 0.1 mole fraction of methane fuel. The BPG-methane-air mixture, according to optimization analysis, achieves the fastest flame propagation speed and the lower chamber peak pressure at 𝜙 equal to 1 and a mole fraction of methane fuel of 0.083. Compared to the BPG-air mixture (𝜙 equal to 1), which had a chamber peak pressure of 20.84 bar, the average results of the optimum configuration parameters reveal a lower peak pressure was 18.97 bar. Comparison of the chamber peak pressure between BPG-methane-air mixture and BPG-air mixture varied by approximately 9.39%. In this context, the gross heat release rate (HRR) is observed to be around 94.44 kW, which represents a 20% reduction when compared to CH fuel. However, there is a slight increase in the emissions of CO and CO2, with a rise of 0.01% and 5%, respectively. In conclusion, the optimal mixture of BPG and methane fuel provides the optimum flame propagation speed with lower chamber peak pressure than BPG.
Data mining for service industry: branch classification of a malaysia retail bank
(2023-01-01)
Chong Siu Hou
The on-going customers’ behavioural shifts from assessing physical banking services to virtual banking services have made retail banks continually review their physical banking network strategies. Such exercise allows the retail banks to maintain their competitive advantages over their competitors while balancing their business portfolios between online banking service needs, optimizing physical clientele coverage, and minimizing costs in running a physical branch network. The research objective is to develop a suitable classification model in decision-making that can mimic experts’ opinions on retail bank branch operational status using a case study on a Malaysian retail bank. Seventy-four branch attributes were used to build a classification model in which experts’ opinions are included as an attribute to allow the data mining (DM) application to emulate experts’ decision-making. The research methodology involves collecting the experts’ opinion through an expert survey to determine the feasibility of a branch remaining open or closing permanently as part of the bank’s network rationalization strategy. The value obtained from the survey was converted into a variable termed “aggregate closure possibility” in this study and then discretized into target class datasets. Then ten classification models were constructed, including ZeroR, Decision Tree, Random Forest, Naïve Bayes etc. Next, three experiments were conducted. The first experiment examined the effect of hyperparameter tuning on classification accuracy. The second experiment studied the impact of changes in the number of target classes on classifier accuracy and then highlighted the best-performing classifier. When the number of target classes was optimized, the accuracy of classifiers improved drastically, of which, three classifiers (Decision Table, J48, and JRip) were the most accurate classifiers. The third experiment studied the effect of attribute selection and instance reduction in optimizing classification performance. It was observed that the accuracy of most classifiers improved proportionate to the reduction of numbers of attributes and instances where Decision Table, J48, BayesNet, and JRip were the best performing classifiers in the third experiment. The result shows that JRip was the best performing classifier in all three experiments. Attribute selection and instance reduction optimized the classification accuracy in encompassing efficient datasets. The study also showed that the DM application could emulate expert opinion in decision-making in retail banking sector. In conclusion, the study has successfully achieved its research objectives. The study contributes to research knowledge on how DM capabilities could improve management decision-making in a real-world application.
Development and performance analysis of hydraulic hybrid regenerative braking system for passenger vehicle
(2022-01-01)
Idris, Khairul Anuar
The global fuel consumption of passenger vehicles has been rising dramatically over time. Since fossil fuel is non-renewable energy, there is a need to improve the passenger vehicles efficiency. Therefore, the hydraulic regenerative braking system (HRBS) is introduced to recapture the lost energy during the deceleration. This study aims to develop HRBS and determine its performances. The experimental work involved designing and fabricating a test rig of the HRBS in a parallel configuration. The performance of the developed system was determined in terms of efficiencies of hydraulic motor and pump. The study findings developed a mechanical efficiency map for the hydraulic motor for different pressures. It was found that the efficiency gradually increased with the increase in pressure from 20 to 80 bar, but a slight drop was seen with further increase in pressure above 80 bar. The highest efficiency recorded by pump and motor were 83 % and 74 %, respectively. Meanwhile, hydraulic pump’s mechanical efficiency maps in terms of pressure were determined for four different speeds. The efficiency was steadily increasing from the pressure 20 to 75 bar. The optimum operating pressure was 65 bar for both the pump and motor. The optimum operation also played a crucial role in establishing the higher mechanical efficiency for the motor and pump, subsequently affecting the overall performance of the developed HRBS system.
Effect of cold deformation on properties of aluminium alloy fabricated using wire arc additive manufacturing technique
(2023-04-01)
Muhammad Ajwad Bin Roslee
Additive manufacturing (AM) owns a huge potential in repair and remanufacturing industries due to its advantage of minimizing waste while having the abilities to produce complex shapes without mold. Current technique to obtain net shape is limited due to strength and lead time issues. AM also provides low cost solution for repairs with wire arc additive manufacturing (WAAM) which use common welding technique. However, this method produces parts with lower strength and hardness due to the high heat input and porosity. In this study, WAAM produced parts was constructed using manual TIG welding at different orientation and welding direction and new strategy was proposed, where cold forging process is introduced as a post deposition treatment, where the parts are subjected to different thickness reduction. The main aim of this study is to evaluate the tensile properties and hardness of forged AA4043 wire arc additive manufacturing (WAAM) constructed at different welding orientation and direction. Result discovered that the ultimate tensile strength (UTS) increased by 44%, from average UTS of 160 MPa to 200 MPa, and hardness value increases by 70%, from average hardness of 43 HV to 73 HV. Using SEM analysis, it is discovered that forging reduced the porosity sizes by 90%. Even with the improvement made by forging, upright orientation still suffer from interlayer strength, producing lower UTS compared to other parameters. Keywords: WAAM; AA4043; strain hardening; cold forging; repair
Effect of cold deformation on tribological performance of additive manufactured aluminum alloy er 5356
(2023-09-01)
Muhammad Faris Akmal Bin Md. Azlin
As a result of severe sliding wear, the automotive parts are often sent to landfills instead of being repaired or remanufactured. Metal additive manufacturing is now an alternative for reconstructing the damaged section. Despite that, the properties of the part may be affected due to heat during welding. Post-weld deformation, like cold deformation, is known as one of the property enhancement methods used to retain mechanical properties. The effect of cold deformation on the wear performance of aluminum alloy ER 5356 was investigated in this study using MIG-based wire arc additive manufacturing (WAAM). The cold forging process was conducted at room temperature and deformed using a 100-ton mechanical press machine. Unforged and forged specimens were compared to obtain specific wear rates for dry and wet sliding. It was observed that forged specimens have a lower specific wear rate than unforged specimens for both dry and wet cases at various speeds with applied loads. The range of the specific wear rate (mm3/Nm) for unforged specimens for dry sliding was 4.25 x 10-5 to 6.29 x 10-5 mm3/Nm, while for wet sliding, the specific wear rate ranges between 8.91 x 10-6 and 1.41 x 10-5 mm3/Nm. On the other hand, for forged specimens, the ranges of the specific wear rate in dry and wet sliding cases were 2.89 x 10-5 to 5.28 x 10-5mm3/Nm and 2.07 x 10-6 to 4.68 x 10-5 mm3/Nm, respectively. The coefficient of friction (COF) for unforged and forged specimens in dry sliding for all speeds and applied loads decreases as the specific wear rate increases. However, COF for wet sliding is lower for both unforged and forged samples. The cold forging process provides a lower specific wear rate and COF for wet and dry cases compared to unforged samples. Based on this study, cold forging shows a good and potential alternative to reverse the properties such as the tribological performance for part repair or remanufacturing.
Effect of fuel injection strategies and intake air supply control on performance, exhaust emission, and combustion characteristics of diesel engine fuelled with biodiesel fuel
(2023-06-01)
Leong Hau
Split injection strategies were generally agreed to be a promising strategy to achieve simultaneous nitrous oxide (NOx) and soot reduction. The air intake channel of a commercial diesel engine is designed for maximum airflow rate under severe load conditions. At medium load, excessive airflow may contribute to NOx formation. Therefore, air intake restriction with exhaust gas recirculation (EGR) might be a viable option to couple with a split injection scheme when the engine operates in part load. The study comprises of three parts. Firstly, an engine test rig has been built, which consists of a dynamometer, exhaust gas analyser, and an engine coupled with an in-house built electronic fuel injection control unit (ECU). Secondly, the effect of biodiesel blend on engine performance and emission has been studied, and the most desired fuel blend and engine operating condition was used in the next step. Thirdly, the effect of the double and triple split injection with different timing and injection ratio coupled with EGR and intake air throttling has been studied. It has been found that B60 POME blend at 2000rpm and 80 Nm were the optimize mid load engine condition. Where 5050 double split injection with 12CA was the optimize split injection strategies. Intake air throttling has been found to enhance EGR's beneficial impact by driving more exhaust gas via the EGR path. A response surface methodology (RSM) study was performed to optimise air control and split fuel injection strategies to maximise engine performance and minimise exhaust emissions The optimum parameter appears at 12 °CA dwell angle, -4°ATDC SOI timing, 40% intake throttle opening, 6.75% EGR, 800 bar fuel injection pressure, and 50% split injection ratio.
Effect of ternary fuel blends of bio -ethanol / propanol, diesel and palm biodiesel on engine performance, emissions and combustion characteristics of a compression -ignition engine
(2023-10-01)
B Navaneetha Krishnan
Malaysia, one of the key palm oil producers in the southeast Asian region, currently uses palm biodiesel mixed with diesel and it aims provide a higher palm biodiesel concentration in diesel fuel. Prior studies on biodiesel fueled compression ignition engines show a higher oxides of nitrogen emission formation when compared to engine operation with diesel fuel. In order to control this particular pollutant formation without any physical modifications to the powertrain, alcohol-based fuels such as ethanol and propanol can be added to the existing palm biodiesel – diesel fuel blend. The test was done on a Kirloaksar TV1 engine having rated power of 5.2 kW at 1500 rpm. The initial test phase was carried out using reference fuels such as Diesel, B100 and B40D60 and later continued with ethanol and propanol based ternary blends namely B40D50E10, B40D40E20 and B40D30E30 and B40D50P10, B40D40P20 and B40D30P30. Analysis of test results revealed that Diesel possessing the highest CV amongst all tested fuels resulted in giving the highest BTE value of 29.9% and in the case of alcohol based ternary blends, utilizing B40D50P10 and B40D50E10 as fuels were seen to result in 27.8% and 27.3% BTE respectively. Similar to the trend of BTE, fuelling CI engine using Diesel fuel gave CP of 71.91 bar which was observed to be the highest among the tested fuels. Using ternary blends B40D50E10 and B40D50P10 resulted in CP value of 69.29 bar and 69.80 bar which in comparison is lower than diesel but higher than ternary blends having more alcohol content. For the tested fuels, the trend for both BSCO and BSHC are observed to be similar and in it the lowest emission BSCO and BSHC values were observed for B100 at 0.132 g/kWh and 0.069 g/kWh respectively. Whereas for alcohol based ternary blends, the lowest BSCO and BSHC values were recorded for B40D50E10 at 0.131 g/kWh and 0.110 g/kWh while for B40D50P10 at 0.119 g/kWh and 0.100 g/kWh respectively. When comparing emission results obtained with ternary fuel blends, the lowest SM and BSNOX emissions value of 60.1% and 4.672 g/kWh for B40D30P30 and 63.6% and 4.504 g/kWh for B40D30E30 were recorded respectively. Among the ternary blends, the fuel type designated as B40D50P10 and B40D50E10 are seen to be more suitable for utilization in CI engines they show enhanced performance and lower emission characteristics in comparison to ternary fuel blend with higher alcohol concentration.
Effects of pitch size, cu pillar diameter, and height during reflow soldering using thermal fluid-structure interaction analysis
(2023-07-01)
Lee Jing Rou
The copper (Cu) pillar with solder cap interconnection has been introduced as an alternative for the solder bump interconnection in electronic packaging. This is because of their ability to tackle limitations such as the collapsing nature and larger pitch size of the solder bump. However, the thermal and mechanical performances of Cu pillar bumps are a concern for achieving reliable electronic products. Hence, this study aims to develop a one-way fluid-structure interaction (FSI) thermal coupling method to model the reflow soldering process of the Cu pillar bumps, and study their thermal and mechanical behaviours. The experimental work was used as a benchmark for developing the numerical model, then the simulated reflow temperature was compared with the experiment result, which was in good agreement. When comparing the reflow temperature profiles, the Cu pillar bumps were found to have comparable thermal performance to solder bumps, showing that Cu pillar bumps are an alternative option. Furthermore, the fluid and thermal analysis were conducted in ANSYS FLUENT, whereas the structural analysis was performed in ANSYS STATIC STRUCTURAL. The thermal loads obtained from the FLUENT were applied on the STATIC STRUCTURAL using one-way FSI thermal coupling method. The simulated flow field also showed that radiation is the dominant heat transfer mode in the oven. The heat transfer was affected by the airflow circulation and leaded to uneven temperature distribution, causing temperature deviation between each bump. Besides, an in-depth study using the simulation approach revealed that the thermal and mechanical performances of the Cu pillar bumps were dependent on several parameters, which were pitch size, Cu pillar diameter and Cu pillar height. From the parametric studies, the simulation result revealed that the overall reflow temperature, the temperature difference between the coldest and hottest bumps, deformation, and stress and strain distribution, influenced the Cu pillar bump reliability. Based on the results of these parametric studies, the suggested configuration for the Cu pillar bump was proposed, with 0.40 mm pitch size, 0.20 mm diameter and 0.09 mm height. Thus, this study provides a comprehensive guide for monitoring the temperature distributions on Cu pillar bumps and its capability to resist deformation and stress, which are crucial criteria for achieving high-quality bonding and reliable electronic products.
Encapsulation process of polymer for led packaging
(2021-12-01)
Alim, Md. Abdul
Several developments and innovations have reported strengthening the reliability and efficiency of these devices to speed up the LED packaging industry for the past few years. To develop a sustainable LED packaging process, die attachment and encapsulation shape are key factors. Epoxy based non-conductive adhesive (NCA) is popular die attachment material. Though NCA have many benefits so, an investigation on the suitable shear strength, adhesive thickness, and adhesion area are essential for die attachment process. Normally, high viscous epoxy resin is used as encapsulation material. A proposed low viscosity epoxy encapsulation shape can represent a new milestone for low-cost LED fabrication. In this work, the relationship between adhesive thickness and shear strength developed in chip and substrate joint is evaluated by using different adhesive applicator. Surface morphology of chip and substrate are also studied by using the SEM, EDS, and image processing software. The result indicated that the suitable shear strength 37.42 N/mm2 obtains at 24 µm thickness of the adhesive layer. A new moldless dispensing method for forming dome shaped encapsulation is studied. Luminous intensity of LED is determined by mixing verity of weight % of phosphor with the epoxy and variation in shape of encapsulation The results show that this method can produce the lenses with high aspect ratio (height over radius) on substrates of different sizes. The improvement of light output was found about 2.37% for dome shaped (average H/R value 0.71) encapsulation. This experimental work is a good guideline to master the geometric shape of encapsulation for further development and to choose technological criteria for LED packaging.
Experimental study on macro voiding minimization in solder joint thermal pad of qfn package
(2023-02-01)
Muhammad Syahir Bin Mahyuddin
Voiding in solder joints is a common problem that occur in electronic packaging, specifically for bottom terminated component (BTC). Quad Flat No-Lead (QFN) is a good example of BTC component that susceptible to void. Thus, QFN component thermal pads were used as the test vehicle in this voiding assessment. The objectives of this study are to analyze the influence of the variables from every parameter evaluated in the experiment on voiding area in QFN thermal pad solder joint and obtain the best combination of variables that can minimize the total void area percentage inside QFN thermal pad solder joint down to below 5%. In this study, several variables and their impacts on voiding based on the literature review were studied. No clean lead-free solder paste of SAC305 composition was employed in this experiment. Various stencil patterns were tested, including Window-Pane, Round, and Triangle/Polygon. The influence of pad surface finishing of the test board on the voiding reduction was analyzed in this study. The effects of convection reflow of various profiles and atmospheres were also considered. All the variables were setup for the experiment execution which begins by solder paste printing, solder paste inspection, component pick & place, convection reflow soldering, Xray inspection, void data extraction & analysis, and finally void results compilation. The results shown that reflow profile Ramp-To-Spike (RTS) Long Reflow Time High Peak Temperature gave lesser void area % than Ramp-Soak-Spike (RSS) Long Soak and RTS Normal profiles. Reflow with nitrogen atmosphere found to yield lesser void area % than air. It was shown that Organic Solder Preservatives (OSP) and Immersion Silver (Im-Ag) PCB pad finishes gave much lesser void area % than Electroless Nickel Immersion Gold (ENIG) finish. The stencil designs of window-pane, round and triangle/polygon shown that all three of them have insignificant difference of impact on void area %. From the results, it can be proposed that combining the pad finishing with OSP and Im-Ag, RTS Long Reflow time high peak temperature reflow profile, and nitrogen atmosphere can significantly reduced the void, regardless of the stencil design used.
Finite element modeling of warpage molded printed circuit board in a reflow process
(2022-05-01)
Sek, Chun Hei
A printed circuit board (PCB) consists of multi-layer materials that allow electrical current flow. Each material layer has its own specific coefficient thermal expansion (CTE), such as Young’s modulus, Poisson’s ratio, etc. A conventional PCB board consists of polymer, silicon, copper, and dielectric. With each layers having different CTE values, this causes PCB to warp.In the semiconductor industry, PCB warpage has greatly impacted assembly process yield and solder joint reliability. The present study explores the warpage changes of molded PCB during the reflow process. Warpage behavior on molded PCB models has been investigated experimentally and numerically. Experimental set-up employs Shadow Moiré technique to measure real-time warpage measurement for a benchmark model with the size of 10 × 10 ×1 mm. Temperature profile with progressive heating from 25 ℃ to 300 ℃ with an interval of 50 ℃ is employed. Then, the sample undergoes a cooling process until it reaches the room temperature. Numerically, ANSYS FEA simulation was carried out to investigate the warpage on different sizes of PCB models. In addition, thermal stress induced by CTE mismatch is studied to understand its impact on PCB warpage. The results revealed that the experiment and the FEA simulation results are in a good agreement, in particularly at the peak temperature of 300 ℃, with less than 5 % deviation between both results. Moreover, the overall package warpage had also been influenced by package size in the reflow temperature. In addition, the results lead to the suggestion that the thermal stress exerted on the contact surface between different material types could lead to PCB warpages. The present research has established FEA that obtaining good warpage prediction model. The insights attained from this study would be beneficial for PCB design improvement, by optimizing materials and dimensions of PCB, in the attempt to minimize the warpage occurrence.
Ginger seed growth recognition using mask region based convolutional neural network (mask r-cnn)
(2023-01-01)
Tong Yin Syuen
As a plant that poses unique culinary and medical uses, ginger has emerged as a valuable commodity in Asia. Among the critical processes in the production of ginger is ginger seed preparation. It is particularly important to monitor the growth and quality of ginger seeds before they are being sown in growing media to ensure germination. However, to date, the ginger seed monitoring process remains manual and is reliant on human experts, despite the growing demand for more effective and accurate monitoring. In this work, a total 1,746 images consisting 2,230 sprout instances were collected from 282 ginger seed samples. In order to realize the automatic monitoring of ginger seeds, deep learning architectures were employed to detect the ginger seed sprouts in three stages from the digital images. This work assessed and compared the instance segmentation task using end-to-end Mask R-CNN models built by different strategies. Then, a two-stage hybrid detector-classifier model was also proposed to benefit from model task specialization concept. Specifically, an end-to-end binaryclass Mask R-CNN and multi-class classifier were combined to be compared to an end-to-end multi-class Mask R-CNN. The experimental results indicate that the use of the hybrid detector-classifier model developed in this work achieved mAP0.50 of 84.27% at inference time of 0.383 second per image in the detection of 402 images consisting of 514 sprout instances. Besides, substantial confusion between object classes in the model was also observed to be in line with the human expert’s perception in data annotation.
Integration of through-the-road parallel architecture hydraulic hybrid vehicle
(2023-07-01)
Tan Pe Hao
This study focuses on the installation of the hydraulic hybrid drive train into a conventional vehicle and fuel economy performance of the Through-The-Road (TTR) Hydraulic Hybrid Vehicle (HHV). TTR is a type of parallel hybrid architecture that connects the conventional drive train and the hybrid drive train via road. The hydraulic hybrid drive train that was previously on a test rig was installed into the vehicle to be road-tested. The fuel economy is compared by testing the vehicle with and without the hydraulic hybrid mode. Different tests were conducted including acceleration and deceleration test as well as drive cycle test. From the acceleration and deceleration test, the optimum charging pressure was determined as 140 bars, where the acceleration test shows 7.8% improvement in fuel economy while comparing to the conventional vehicle. The drive cycle test at 100 bars charging pressure shows hydraulic Hybrid On mode provides 8% fuel economy improvement comparing to the Hybrid Off mode
Investigation of tool coated with tetrahedral amorphous carbon nanocomposite for single-shot drilling of cfrp/aluminium stack
(2023-08-01)
Jebaratnam Joy Mathavan
Drilling through a composite-metal stack in a single pass is a challenging process, as the drill bit must penetrate through two distinct materials simultaneously. Though tungsten carbide (WC) drill bits are commonly used in this field due to their better performance than high speed steel (HSS) tools and cost effectiveness compared to poly crystalline diamond (PCD) tools, they tend to create defects such as diameter variation, circularity error, surface roughness, delamination and burr formation. To address these issues, this study aims to coat the tungsten carbide drill bits with tetrahedral amorphous carbon (Ta-C) nanocomposite layers such as micro-Ta-C, Ta-C+Cr, and Ta-C+Ti. The holes were drilled using a 4.85 mm diameter twist drill, with a feed rate of 0.05 rev/min and a spindle speed of 2600 rev/min. The Physical Vapor Deposition (PVD) method was used for coating development, and triple rotation was employed to achieve a thin film thickness of 2.5 μm. The micro-Ta-C coating exhibited 28.9% and 53.6% higher maximum bonding strengths and resist 61.37% and 90.47% higher maximum frictional forces than Ta-C+Ti and Ta-C+Cr coatings, respectively. It also had 6.08% higher HV0.005 hardness compared to the uncoated tool. The Ta-C+Cr coating had the lowest coefficient of friction (<0.05), followed by the Ta-C+Ti coating (<0.09). All tools produced an average stack up diameter error below H9 tolerance and hole circularity error below 30 μm. Surface roughness in aluminium panel by all the tools required further improvement. All coated tools achieved better average CFRP surface roughness below 3.2 μm, with Ta-C+Ti coating performing 22.3% better than uncoated tool. Micro-Ta-C and Ta-C+Ti coated tools showed 35.26% and 16.67% better exit delamination, respectively compared to the uncoated tool. The average exit burr height from all tools was below 150 μm, with Ta-C+Cr and Ta-C+Ti coated tools showed 23.93% and 6.45% better burr height results compared to micro-Ta-C coated tools, respectively. Based on coating characterization, experimental results, and process capability six-pack statistical analysis, the Ta-C+Ti coated tool is the preferred choice.
Moisture diffusion during solder reflow processes of electronic packages
(2022-01-01)
Elwin Heng, Chia Jie
The modern electronic packages has evolved and become so complex while the size has continued to shrink. packages continues to shrink. As a result, modern days electronic has become complex in manufacturing yield and reliability defect has become a huge concern. Moisture induced quality and reliability defect are not new to electronics industries. But the complexity of the modern days packages has caused moisture induced defect to become a huge concern. Hydroscopic materials in electronic packages are capable to absorb moisture upon exposure to environment throughout storage, manufacturing process and transport phase. Although moisture is supposed to be desorb when going through high temperature reflow process, but the presences of hydrophobic material in the structure could possibly obstruct and hinder the moisture desorption, causing residue moisture to continue reside in electronic packages. The internal moisture will develop high internal vapour pressure when going through high temperature loading. This vapour pressure can cause void, delamination, cracking to electronic packages internal structure, which can be detrimental to electronic packages. The moisture diffusion is very difficult to be analyse as electronic packages often made up from multiple components with different material properties, causing the moisture diffusion very difficult to be modelled can calculated. This paper will utilize Direct Concentration Approach (DCA) to model the moisture diffusion accurately to analyse the effect from moisture diffusion. Aside from the pressure develop from moisture, the high temperature subjected to electronic packages will also causing thermal stress. The typical electronic package with hydrophobic material could obstruct moisture desorption and causing moisture residue found to be 36% higher in vapour pressure compared to bi-material model, going beyond saturate vapour into superheated vapour or compressed liquid, which expose electronic package to higher pressure. The maximum Von-Misses syress induced by moisture significantly increase on package with hydrophobic material by 115% compared to model with hydrophilic material. With the use of Direct Concentration Approach, the effect of moisture diffusion and coupling with thermal stress in the aspect of Fluid Structural Interaction will be able to be studied.
Numerical Simulation And Experimental Investigations On The Effect Of Polypropylene Rheology In The Injection Molding Process
(2014-11)
Rusdi, Mohd Syakirin
The design and fabrication of the mold are costly for the injection molding machine. Prior to the fabrication process, the prior to molding analysis is important to investigate the flowability of molten plastic in the mold design. The pre-molding analysis is carried out using simulation software, with the purpose to reduce the fabrication cost and time. Numerical simulation has been proven as a good tool and cost effective way for pre-molding analysis. Therefore, this research focuses on the unsteady three-dimensional (3D) simulation of mold filling during the thermoplastic injection molding process using ANSYS FLUENT 14 software. Common Polypropylene (PP) and medical grade materials are considered in the study. Commercial single screw injection molding machine (Battenfeld TM750/21 O) is used to study the flow front advancement of the common polypropylene at different injection pressures and melt temperatures ofa single cavity of the tray. GOTfFERT Rheograpb25 Capillary Rheometer machine is employed to perform the experiments on the rheological behavior of the polypropylene (i.e., shear rate and viscosity) at different melt temperatures. The rheological results are compared with those obtained by numerical simulation.
Optical 3-d inspection and defect detection in silicon wafers using phase-measuring deflectometry
(2023-05-01)
Lim Meng Lip
Accurate three-dimensional (3-D) surface profiling on silicon wafers is becoming significant because 3-D defects on silicon wafers can ruin the product. Thus, the study aims to develop an optical 3-D inspection and defect detection system for silicon wafers using phase-measuring deflectometry (PMD). The measurement setup consists of a projector, a camera, and an acrylic projection screen. Sinusoidal fringe patterns were projected onto the screen, and images of specimens encoded with the reflections of the sinusoidal fringe patterns were captured by the camera. Phase demodulation, phase unwrapping, slope calculation, and height reconstruction algorithms were developed to compute the surface profiles of the specimens from the captured images. The algorithms were tested on spherical concave and convex mirrors before being applied to measure light-emitting diode (LED) silicon wafers. Studies were also conducted to correct perspective distortion, intensity errors of the fringe patterns, and color intensity errors of color-coded fringe patterns. The results show that the PMD system can measure the surface profiles of the concave and convex mirrors with micrometer-level accuracy. Sub-micrometer level height differences were achieved for verification using stylus profilometry. Reductions in phase error and height error were demonstrated when perspective distortion and intensity errors in the projected fringe patterns, and color-intensity errors in the color-coded fringe patterns, were mitigated. The capability of the developed PMD system in detecting and measuring 3-D surface defects on silicon wafers are demonstrated.
Performance characteristics of air steam gasification in biomass downdraft gasifier– combustor
(2023-10-01)
Mohammad Junaid Khan
Nowadays, the world is promoting renewable energy through implementing the use of green energy. Gasification technology has been widely investigated since it provides output gaseous fuel known as producer gas (PG). The aim is to produce alternative renewable gas fuel to replace natural gas. This goal, however, is not attainable when using air as the gasification agent due to the severe dilution with N2. To overcome the N2 contamination in PG, steam can be used as the gasification agent. The main obstacle for steam-gasification is the highly endothermic reaction nature. This study investigated biomass steam gasification in a new medium-scale annular reactor design with gas heating jacket. This experimental study used two steam injection configurations: bottom and top. Temperature varied in the range of 300-600°C for first configuration, while steam to biomass (S/B) varied from 1.7 to 2.6. Peak H2% was 27.7% and higher heating value (HHV) of gas was 7 MJ/Nm3. Using top injector enhanced the heat transfer which elevated the temperature range (700-950°C) and reduced S/B ratio in the range of 1.3-2.2. Highest H2% was 44% at the best steam flow rate of 30 g/min with HHV of 12.8 MJ/Nm3. Tar contamination was reduced from 13,6 g/m3 to 7.4 g/m3 with the increase of S/B. The effect of different fuels including coconut shells charcoal (CSC), palm kernel shells (PKS), and Empty fruit bunch (EFB) on hydrogen production was also investigated. H2% was 47.7% for CSC, followed by 46.3% for PKS and 44.7% for EFB. Finally, the sustainability of the reactor was tested by switching from LPG heat input start-up into PG fuel. The reactor was not able to sustain the operation at maximum temperature when using 100% PG fuel. Therefore, the reactor was tested with air flow to provide a small portion of the heat input in air-steam gasification mode. The reactor was characterized in air-steam gasification mode using 4 air flow rates of 25, 50, 75 and 100 LPM flow rates

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Browsing Pusat Pengajian Kejuruteraan Mekanikal - Tesis by Type "master thesis"

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