Theses & Dissertations

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https://hdl.handle.net/20.500.14170/1590

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Browsing Theses & Dissertations by Department "Universiti Malaysia Perlis"
  • Publication
    An energy absorption characterization of improved circular thin-walled tubes under dynamic loading
    ( 2013)
    Masniezam Ahmad
    Thin-walled tube is one of the energy absorber devices designed to dissipate energy and increase the efficiency of a crashworthiness structure in an impact event. During an accident, thin-walled tube dissipates the kinetic energy of the structure and converts the kinetic energy into the other form of energy thus minimize the impact experienced by the occupant. This research examines the thin-walled tube subjected to axial dynamic crushing experiment by using a drop weight impact tester. A nonlinear finite element model for the tube crushing has been developed by using LS-DYNA software and a good agreement has been achieved between the finite element model and experimental results. The parametric studies of the thin-walled tubes have been performed by using the validated FE model. The analysis of energy absorption characteristics includes the energy absorption capacity, initial peak load, specific energy absorption (SEA) and crush force efficiency (CFE) results. The shape, material and geometry of the tube are varied to investigate the effect of using these parameters to the energy absorption characteristics. As a result, circular tube is capable to provide better energy absorption characteristics compared to the square tube. The tubes designed by three different materials which are aluminium alloy AA6061-T6, carbon steel S1214 and magnesium alloy AZ31B-O has been developed in LS-DYNA. It was found that the magnesium alloy AZ31B-O is highly potential to be created as the thin-walled tube material instead of aluminium alloy and carbon steel since it has excellent result in initial peak load, SEA and CFE. However, when the applications neglect the damage of the structure and does not involving human, carbon steel is the best material as it can absorb most energy capacity and high mean crushing force. The effect of length, diameter and thickness of the tube to the energy absorption characteristics has been investigated. It was concluded that initial peak load and CFE are optimum in thicker and larger tube. Energy absorption capacities are optimum in thicker, larger and longer tube while SEA result is optimum in thicker, smaller and shorter tube. At the end, the modifications performed on the original tube shows an improvement in the energy absorption characteristics compared to the current tube designs. A combination of conical tube with flat end cap was proposed as the best modified tube since it has excellent results on initial peak load, CFE and SEA with moderate results on the energy absorption capacity. Research information provided in this study will serve as a guide to design the thin-walled tube in the future.
  • Publication
    Design and development of integrated transplanter and weedermmachine for system of rice intesification (SRI) cultivation in Malaysia
    ( 2015)
    Mohd Syedi Imran Mohd Dawi
    System of rice intensifications (SRI) was practiced by community in Lembah Organik Lentang, Kampung Lentang since 2010. Throughout the years, the paddy plots began to grow in number. Since most of the SRI practices needed to be done manually especially planting the seedlings and using conventional tools to kill weeds and loaming the soil, the demand of machinery was inevitable. This is due to time consumed and numbers of manpower needed to carry out the task. For example, weeding process need to be done 4 times for one season. A new chassis that is able to support mechanical weeder and transplanter for SRI was developed. This project was designed to support SRI practices among Malaysian farmers. Product design specifications were gained from rice farmers situated at Kampung Lentang, Belantek, Kedah. Several concepts were generated and the best was choosen for further development and analysis. New chasiss was developed to replace the current agriculture tractor. The chassis was fit with small petrol engine and one main wheel. It was designed to pull SRI weeder and transplanter mechanism. The weeder mechanism was designed to loam three rows at once and able to be use for weeding process up to 40 days of age. Finite element analysis software was used to identify potential failures and subsequent rectification of the problem at the design stage. Some calculation was done to determine force and torque that may act on design. Steel was chosen as material to reduce fabrication cost. Stainless steel and aluminum were also initially considered as suitable material for the design but was not chosen due to the cost is high. For the rice transplanter, the transplanting mechanism uses linkage to drop rice seedlings on top of the soil. This fits the SRI practices for transplanting the young seedling. It is not just able to plant one seedling at one location but also plant the seedlings without removing it from nursery soil, thus, eliminate possibilities to injure the seedlings. Motion analysis was done to analyze the linkage movement. Finite element analysis also was done to determine maximum stress for each linkage part. Two of the designed products were built into prototype which are SRI Chassis and SRI Weeder and tested in actual working environment at paddy field. The field trial shows SRI Weeder was able to reduce manpower by 67%, working time by 42% and save 60% of overall operating cost.
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  • Publication
    Development and characterisation of hybrid napier/glass fibre reinforced epoxy composites
    ( 2016)
    Mohd Ridzuan Mohd Jamir
    Owing to serious environmental concerns in recent years, researchers have been driven to investigate the use of sustainable materials as a substitute for common polymer composites manufactured with synthetic fibres, such as glass, carbon, and aramid. This has generated increased interests in the development of natural fibre-reinforced composites. However, natural fibre composites have some limitations such as poor resistance to moisture absorption and possess lower impact strength. To further enhance the properties of natural fibre composites, reinforcements such as glass, carbon, and aramid fibres are hybridized into natural-fibre composites. The mechanical properties of hybrid Napier/glass fibre reinforced epoxy composites and, their durability under elevated temperatures and moisture exposure were characterised and investigated. The 5% alkali-treated fibre had achieved the maximum ultimate tensile stress of single fibre test. The hybrid composites with 5% alkali-treated Napier fibres exhibited the greatest tensile and flexural strengths. Observing the impacted surfaces, it can be noticed that the hybrid composites with untreated Napier fibres present less damage area. The moisture absorption of the hybrid Napier/glass fibres reinforced epoxy composites increased with the water-immersion period of the samples. As the temperature approached Tg, at >60 °C, the fibre would deboned from the matrix and consequently reduced the tensile and flexural strength of the material. This study is expected to provide evidence to support the development and application of this material.
  • Publication
    Development of a framework for the reduction of manufacturing defects in a composite material process
    ( 2008)
    Muhammad Iqbal Muhammad Hussain
    Reduction of defects is a critical issue in manufacturing operations. It goes without saying that defect reduction leads to manufacturing cost reduction, and this translates to increased profitability for the organization. Company A is a manufacturer of high technology composite materials. Of late, it has been experiencing high levels of defects from its manual hand lay-up and autoclave processes that generate products coded ‘L’and ‘T’in this thesis. Thus, a study that integrates the use of ‘statistical design of experiments’(SDE), ‘failure mode and effect analysis’(FMEA), several side experiments, control charts, and certain process controls is carried out. The study combines time-tested industrial problem-solving and process-improvement methods in a way that is both regimented as well as flexible, in line with the numerous uncertainties that inevitably present themselves in any live manufacturing environment. This culminates to the development of a generic framework, of which its execution enables the determination of the best process set-up that gives the minimum number of defects in the final product. Taking into account the circumstances under which the processes operate, fractional factorial design (2^ (4-1) resolution IV design) is used in production line ‘L’, and , a two-level factorial blocked design with 24 runs and eight center points is used in production line ‘T’. These designs give much insight into this line’s defect-causing variables, and enables the examination of important process parameters such as geometry of core, temperature, pressure, and cooling rates, to name a few. Consequently, after the entire research process is carried out, it is seen that the number of defects is greatly reduced (from 30 panels/month to 3 panels/month for wrinkles, 18 panels/ month to 4 panels/month for delamination in production line ‘L’, and from 25 © This item is protected by original copyright xxviii panels/month to 5 panels/month for delamination in production line ‘T’), leading to tremendous cost savings on the shop floor.
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  • Publication
    Dynamic modelling and adaptive PID control of palm oil biodiesel engine
    ( 2013)
    Azuwir Mohd Nor
    The use of biodiesel seems set to become a popular alternative fuel for transportation to replace the high price petroleum fuel. To successfully implement the usage of biodiesel in transportation requires good understanding of the engine dynamics and reliable controller to manage the engine. Hence, this study is aimed at the development of mathematical models and adaptive controller of automotive engine fuelled with palm oil methyl esters (palm oil biodiesel). The process modelling investigation started with linear discrete-time single-input-single-output (SISO) dynamic mathematical models representing the relationship between engine speed and engine throttle of a diesel engine test-unit. Both deterministic and stochastic model types are derived and validated. Three parameter estimation techniques of Recursive Least Squares (RLS), Recursive Extended Least Squares (RELS) and Differential Evolution (DE) are used to estimate the engine parameters. Then, the nonlinear dynamic model of the engine type is derived and validated. Orthogonal Least Squares (OLS) estimation technique together with Error Reduction Ratio (ERR) procedures are used in the selection of the parsimonious model structure and parameter estimation for nonlinear ARX (NARX) model. The accuracy of linear and nonlinear dynamic models are compared and analyzed. The results show that all models derived are stable and good in predicting the engine output. Next, adaptive PID speed controller based on pole assignment method was designed, developed, tested and simulated before implemented in real-time on the engine test-unit. The adaptive controller is designed to track and regulate set-point speed as well as reject the disturbance introduced to the system. Throughout the investigation the control algorithm developed is tested at various engine set-point speeds and load disturbances. The results show that the algorithms produce very good dynamic output responses of the palm oil biodiesel engine. The algorithms have successfully achieved the control objective of tracking and regulating the engine speed. Furthermore, the experimental results also proved the disturbance rejection capability of the controller. The performance of the adaptive controller is compared with tracking, regulating and rejecting disturbance of automotive engine fuelled with petroleum diesel. In both cases, the controllers performed very well and proved to be reliable for both types of fuel. This study has significantly proved that adaptive PID speed controller developed performed effectively in controlling automotive engine speed fuelled with palm oil biodiesel and petroleum diesel without engine modification.
  • Publication
    Ergonomic intervention in harvesting process in oil palm plantation
    (Universiti Malaysia Perlis (UniMAP), 2016)
    Roejhan Md Kawi
    Most fannworkers in the small and medium Oil palm industry are using conventional method for harvesting works. Therefore, they are extremely exposed to the risk of shoulder muscle injury which is one of the musculoskeletal disorders (MSDs) problems. Referring to the Rapid Upper Limb Assessment (RULA), conventional harvest works was highly risk to undergo shoulder muscle problem due to extreme harvest posture with the repetitive and high of loading. Based on the body score result, there were 100% of respondent proven suffering shoulder problem. Hence the aim of this project is to identify proper working posture with design of palm oil harvesting ergonomic intervention device in order to replace the use of long arm sickle in conventional harvest. A comprehensive field study was conducted which focusing on conventional harvest posture by using Electromyography (EMG). Five male subjects volunteered to demonstrate these harvest posture conditions with four selected muscle activity and recorded by EMG and the signal data then plotted into scatterplot. By these findings, the analytical expression developed with proper harvest posture basis as a motivation in designing the intervention. The intervention is developed into prototype with mechanism system. A prototype field evaluation has been conducted to monitor the muscles activities with focus on same selected muscle by using EMG. Volunteered farmworkers is randomly picked to demonstrate the hruvesting process. The result shows reduction of selected muscle activity as compared to the conventional method due to working posture improvement. The Human Activity Analysis (HAA) was study to investigate the posture of the farmworkers during conventional and intervention harvest. There are five body conditions were simulated: L4- L5 compression, body load compression, axial twist compression, flex/ext compression and L4-L5 joint shear. Besides, the RULA's also shows better score as concrete evidence in improving body posture during harvesting work with this new method. As conclusion, optimized working posture along with the assistance of intervention prototype in oil palm harvesting process is suggested since the data provided in this research shows it could decrease the risk of shoulder muscle pain. This research also encourage of generating the innovation in designing new tools to increase the agriculture workers petformance.
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  • Publication
    Evaluation of shrinkage and weld line strength on thick flat part in injection moulding process
    ( 2016)
    Mohd. Nasir Mat Saad
    Mechanical properties such as strength of moulded part is critical predominantly for parts that require a sufficient strength for the functionality of the product. One of the main concerns that affects the mechanical properties is weld line defect which occurs when two or more gates are used during the injection moulding process. In addition, the dimensions of the part are also crucial in terms of precision of the product. Thus, the shrinkage of the moulded parts also needs to be controlled. Most of the previous studies focus on the weld line strength or the shrinkage of the moulded part separately and it is rare to find studies that incorporate both of these aspects. Therefore, the current study evaluates both shrinkage and strength of weld line using Design of Experiment (DOE) and Response Surface Methodology (RSM) in multi-objectives optimisation utilizing the injection moulding parameters. The mould was successfully designed and fabricated complete with gating system, cooling system, core and cavity of a thick flat part based on ISO standard. The variable parameters used in this study are coolant inlet temperature, melt temperature, packing pressure and cooling time. Simulation process was conducted to determine the recommended setting of injection moulding parameters and the range of the variable parameters. The acceptable range of coolant inlet temperature was set between 50°C and 70°C, while the melt temperature was between 250°C and 270°C. The range of packing pressure was set between 50 MPa to 70 MPa and cooling time between 8 s and 12 s. Experimental works were conducted according to the experimental design where regression models were established to predict the shrinkage and weld line strength. An optimal setting parameter of the process was established to achieve the optimum shrinkage and weld line strength of the moulded part. The results of shrinkage and weld line strength using an optimal setting after optimisation process were compared with the results obtained using the recommended setting. It was found that, the shrinkage in the normal and parallel directions to the melt flow were reduced by 5.97 % and 4.91 % by predicted model generated using RSM. On the other hand, the weld line strength was improved by 3.76 % as compared to the weld line strength obtained from the recommended setting.
      1  4
  • Publication
    Experimental and analytical study of drilling hybrid glass/carbon fibre reinforced epoxy composite
    ( 2016)
    Tan Chye Lih
    Hybrid composites have become increasingly attractive in research and development activities in recent times due to the capabilities to tailor their mechanical performance or characteristics to specific needs. Current research and innovation in the field of hybrid composites include processing, development and testing of metal matrix hybrid composites as well as the synthetic and natural fibre hybrid composites. Nonetheless, a number of complications arise in the manufacturing processes, particularly in machining such as drilling, of these multiphase laminated materials. The fact is that machining of composites or hybrid composites presents a great challenge due to anisotropic nature of the material, lack of plastic deformation and abrasiveness of the fibre reinforcements. According to the previous statistic studies, unqualified holes leads to approximately 60 % part rejections during the final assembly process. Therefore, this research study pursues an experimental and analytical approaches to extend the fundamental knowledge in drilling hybrid fibre reinforced polymer (FRP) composites. Prior to the drilling tests, the evaluations of the mechanical performance of hybrid FRP composite have been attempted. Specifically, the hybrid effect of the plain woven carbon and E-glass fibres hybrid composites within an epoxy polymer matrix was experimentally evaluated. It was evident that the physical properties and mechanical strength of monolithic fibres composite were enhanced 48 % by hybridising carbon fibres into the glass FRP composites. In addition, theoretical analysis through the rule of mixture reveals that the hybrid FRP composites have exhibited a positive hybrid effect in term of tensile and flexural behaviors. Even though fabrication technology for the hybrid FRP composites has well advanced in the production of near-net shape components, the secondary machining process is vital for completing the postmanufactured of these materials. Thus, the desired setting for minimising the delamination damage and surface roughness were determined using the Taguchi methodology and statistical analyses.
  • Publication
    Fabrication and characterization of microwave sintered PM Fe-Cr-Y₂O₃ composite
    ( 2013)
    Marina Marzuki
    This research is focused on assessing the feasibility of the innovative microwave sintering technology for fabricating iron – chromium composites via powder metallurgy route. The microwave sintered composites were compared with their conventionally sintered counterparts in terms of physical and mechanical properties (micro Vickers hardness and compressive strength). Microwave sintering is proved feasible to consolidate the composite. The result also revealed that the microwave sintered iron chromium composites possess improved density, micro hardness and compressive strength compared to the conventionally sintered composites. Process evaluation also revealed that microwave assisted sintering can lead to reduction of 70% of sintering time when compared to conventional sintering. Another aims of this research is to study the effect adding varying weight fraction of yttria reinforcement to the iron chromium composites. For this purpose iron-chromium composites is reinforced with 5, 10, 15 and 20 wt.% of the ceramic particulates. From the study it is observed that the mechanical properties of microwave sintered iron – chromium composites improved with the addition of 5 wt.% ceramic content. For the conventional sintered composites, highest micro hardness and compressive strength were obtained from the 10 wt.% reinforced composites.The highest hardness value is given by microwave sintered composite. Other physical properties such as density was decreased as the reinforcement content increased. This is due to the increasing presence of porosity in the composites. However, microwave sintered composites exhibit better density relative to theoretical density and densification behaviour.
  • Publication
    Fracture mechanic analysis of multiple edge cracks in a finite plate using kerf to emulate crack interaction
    ( 2015)
    Ahmad Faizal Annuar
    Multiple cracks with different or similar geometries that coexist on the same plane will affect its neighbouring counterpart’s Stress Intensity Factor (SIF) value due to interaction effect. The interaction effect is much related to the change of stress distribution profile that produced by neighbouring crack. The study had been proven true over the past years through various Finite Element Analysis FEA software packages and formulation, but an actual experiment and raw data acquisition is rather scarce in literature. This could well mean that the process to prepare multiple cracks study is hard to emulate physically as oppose to single crack study. The main intention of this study attempts to simulate and find a possibility to replace subsequent crack interaction to primary crack with kerf, incise in Electric Discharge Machining (WEDM) wire cut, by evaluating the longitudinal stress distribution component. Current regional technology of WEDM permits kerf gap machining at 0.050mm. This research, focuses on emulating two parallel edge cracks’ interaction as initial attempt to prove that kerf provides similar interaction on primary crack’s SIF. Through simulation using ABAQUS Computer Aided Engineering (CAE), values of non-uniform stress distributions produced by kerf within the potential primary crack region was analysed and compared to non-uniform stress distributions that produced by a crack as validation. Absolute error tabulation of stress distribution that produced by kerf suggests that it is fit to replace subsequent crack for further study of interaction in multiple cracks. A nonconventional method to determine Normalised SIF of crack, 𝑌𝑎 , using Multiple Reference State (MRS) Weight Function was chosen given its capability in complex computation of crack geometries that includes non-uniform stress distribution values in finite bodies. The 𝑌𝑎 values from FEA models of double edge cracks which were used as reference points exhibits decent agreement with data trend line from those conceived by MRS Weight Function Method. Experiments are carried out with three (3) specimens, made from Aluminium Alloy 6063 T6, which contains a crack, a, at varying length and 10mm kerf, b, each at similar edge surface at similar separation of 10mm to observe further growth of crack under presence of kerf. The three conditions of the specimens are designed as followed; i) a≈b, ii) a=1.5b, and iii) a=2b. This is to highlight the existence of interaction between crack and kerf under circumstance where primary crack at different conditions attempts to grow under loading. This research contributes the knowledge of kerf’s non-uniform stress distribution trend under tension loading and its influence to primary crack’s growth in which the results are comparable to those produced by subsequent crack. The study of kerf in this research is significant as it disclose characteristic of kerf and crack interaction and allows anticipation in the events structural failure for engineers and research in order to avoid potential disasters.
  • Publication
    Identification of cultivated rice MR 263 seed and weedy rice seed variants using CCD camera based-machine vision system
    ( 2015)
    Aimi Athirah Aznan
    The main purpose of this study was to develop rice seed identification research prototype system to classify cultivated rice and weedy rice seeds variants using machine vision system through the extraction of morphological, colour, and textural features of the seeds. Five different types of weedy rice seeds variants samples of open panicle, close panicle and awn type were collected from several commercial farms in Kedah. The MR 263 seed was obtained from a commercial rice seed bag from a local supplier. In this study, seed samples were consisted of 600 seeds of MR 263 and 600 seeds from weedy rice seed variants group. Images of the rice seed samples were acquired using a charge coupled device (CCD) colour camera. Laboratory Virtual Instrument Engineering Workbench (LabVIEW) development environment was used to program the image processing, features extraction and the classification analysis. There was 12 morphological, 6 colour and 5 textural features were extracted from the seed images. Four types of classification model namely morphology, colour, texture and morphologycolour- texture models were established based on the extracted data. Each of the models was analyzed for feature selection using stepwise discriminant analysis (SDA) to develop the optimized features model. Then, the original and optimized features models were analyzed using 3 classifiers; discriminant function analysis (DFA), support vector machine (SVM) and neural network (NN). Analysis of variance (ANOVA) was conducted on the 3 classifiers to evaluate the mean classification accuracy levels of the 8 extracted features models developed. The ANOVA showed that there is no significant difference of mean classification accuracies between the 3 classifiers. The classification results using morphology-colour-texture features model was found to obtain higher classification accuracy levels as compared to the single feature models. An identification system was developed in the LabVIEW to classify the cultivated rice MR 263 and weedy rice seed groups using optimized features of the morphology-colourtexture model in DFA. The developed system was able to classify both seed groups at 99.4% accuracy level using testing data set.
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  • Publication
    Improved models for impact of Viscoplastic bodies
    ( 2018)
    Masniezam Ahmad
    Impact between two bodies is a complex phenomenon commonly occurs in many areas such as sports, automotive, geology and many more. Until now, modeling an impact is still a challenging task due to inherent imprecision of constitutive laws for the impact mechanics. Previously, impulse-momentum method was used as general principle to solve this dynamic problem. Then, impact is modeled by employing a lumped-parameter, which is represented by the spring and/or dashpot elements as a compliance at a small contact region around the point of contact. Through this method, the mechanics of contact during a short interval of impact event can be calculated. Formulation of the model using elastic, viscoelastic, elastoplastic or viscoplastic constitutive material behavior is employed as a contact law for the compliance at the small deforming region. At a very low impact velocity, an elastic model based on Hertz contact theory and the viscoelastic Hunt & Crossley model have accurately predicted impact responses. However, at higher impact velocities, a significant part of the initial kinetic energy is dissipated due to plastic deformation, stress wave propagation, sound, heat and other effects. An elastoplastic impact model can be used to predict the elastic-plastic deformation of the impacted bodies, however the effect of stress wave propagation is not considered in this model. This problem has been addressed by adopting a viscoplastic model that can predict the impact response which encompasses both elastic and plastic deformation and also considers the energy dissipated due to wave propagation. This study proposes two viscoplastic impact models that were developed from modification of previous viscoplastic models; Yigit and Ismail & Stronge models. The proposed model provides an alternative method to predict the impact responses by employing a linear spring element or combining a linear and nonlinear spring element in restitution phase of the compliance. The impact responses for several types of balls have been also studied by drop test experiments and finite element analysis. In experiment, various tests have been conducted to ensure accurate measurements of force and velocity for drops of different sports balls. On the other hand, an accurate finite element model (FE model) was developed and it was validated with previous FE model. As a result, the impact responses obtained from the proposed models have been validated with both experiment and FE analysis. In general, the proposed models can predict the maximum force and contact time with percentage error of less than 20 % and 11 % respectively. The proposed model was successfully improved the accuracy of impact response prediction for normal impact between two compact bodies. For the case of elastic impact, the proposed model gives the smallest energy loss of any of these previous models. Thus, it provides good estimation of contact forces and deformations, compared to the other viscoplastic models. Besides that, the impact responses for impact of different materials, sizes and impact velocities of the body have been obtained from the FE analysis. In overall, new developments for viscoplastic impact model and impact responses for colliding bodies were presented.
  • Publication
    Machines condition analysis based on output machining parameter and vibration signal monitoring
    ( 2015)
    Mohd Shuhidan Saleh
    This dissertation reports an investigation on the machine condition for a group of similar milling machines based on vibration signal and surface roughness quality. This study is motivated by an issue in maintenance field where an appropriate technique has to be applied to monitor the condition of a machine. In this work, the machining system studied are the group of milling machines within the laboratory in the School of Manufacturing Engineering, Universiti Malaysia Perlis. To further understand the subject of studies, the extensive literatures has been done related to condition monitoring, vibration analysis and also the effect to the surface roughness. The application of fishbone analysis in identifying the possible causes of the problem also has been included in the review. In this work, the vibration level have been measured at three different points of the machines (ram, spindle and vertical head). These vibration level is then analysed to determine the causes of inaccuracy in the machining quality. From the experimental results, it is found that surface quality is strongly affected by the vibration. Machine 2 is found in critical state due to the highest level of vibration as compared to the other machines. Machine 1 and 8 have demonstrated the unusual condition where the vibration level is moderate however the surface roughness value is high and does not synonym to vibration trend. In the present work, the root cause for vibration and poor surface quality are performed by using fishbone analysis for the affected machine. The findings are discussed and the conclusions reached in this project and recommendations for future work are enclosed
  • Publication
    Microwave sintered of 10Hydroxyapatite-Yttria stabilized Zirconia-Alumina bioceramics composites for biomedical applications
    ( 2015)
    Nur Liyana Mohd Rosli
    The minimal biocompatibility features and consequence implant loosening are the crucial issues in orthopedic implant complication. The prime requirements of medical implant are acceptable mechanical properties which impart excellent interaction with the surrounding tissue without elicit an adverse response. The remarkable biocompatibility properties of hydroxyapatite (HAP) acknowledged as the most practical implant materials. The bioactive hydroxyapatite encountered with poor mechanical properties.The presence of YSZ and Al2O3 areas an inert and physically strong bioceramics with high level of biocompatibility. The research associated with this bioceramics had been proven over the past years through the conventional sintering, but processing this bioceramics composites using microwave hybrid heating is rather scarce in literature. This research is specifically concerned with the effect of microwave sintered 10HAP-YSZ-Al2O3 composites towardsdifferent sintering temperatures and the various compositions of YSZ and Al2O3to 10 wt. % of HAP. Comparative sintering was performed at temperatures of 900ºC, 1000 ºC and 1100 ºC. Composites containing 60 wt. % microwave sintered at temperature of 1000 ºC exhibited the greatest properties, due to incorporation of YSZ and Al2O3which overcome the inherent brittleness of HAP. The 10HAP-60YSZ-Al2O3 composites indicated an increase in density to 2.88g/cm3, Vickers hardness and compressive strength results as 5.68GPa and 36.31MPa respectively.
  • Publication
    Modeling of the winding coil temperature in a compact permanent magnet wind generator
    ( 2018)
    Nor Zaiazmin Yahaya
    Wind energy harvesting has existed since ancient civilization. Nowadays, wind energy is harvested to generate electricity using a wind generator. With the recent reduction in the price of high-performance permanent magnet, it is made possible to construct a highefficiency compact generator. One of the problems with the compact generator is temperature management. Hence, this study aims to develop empirical models in estimating the winding coil temperature for natural and forced convection cooling. The modeling process was started with conducting experiments at various operating conditions while observing temperatures at several locations on the wind generator. One of the challenges in conducting the experiment is that it consumed a lot of time for the temperature to reach its steady state condition. Thus, this study proposes a method to reduce the experimental time by estimating the settling time using a control system engineering modeling technique. By using the method, the experimental time reduces by 55% with the difference of 1% between the predicted temperature and the steady state temperature. Due to several limitations of the experimental equipment, experiments with high current output (more than 1 amp) cannot be conducted, this leads to the alternative of simulation experiments. The challenges of simulation experiments started with the difficulty to acquire parts dimension. A method is proposed to acquire the dimension by using an image processing technique. The next challenge is to generate a quality mesh during the electromagnetic modeling process. To tackle this problem, an adaptive meshing technique is used which resulted in magnetic flux value increases by 5.3% compared to an automatic meshing method. The electromagnetic modeling was successfully implemented and validated with the difference of less than 4.0% in Vrms (volt) between simulation and experimental results. The electromagnetic results were then transferred to Ansys Fluent for computational fluid dynamic analysis. The Ansys Fluent software was used to simulate heating and cooling effects via natural and forced convection at the wind generator. Two empirical models were developed to predict the winding coil temperature with the difference of less than 10.7% in the natural convection cooling results compared to the experimental results. As for the forced convection empirical model, it was used to estimate the maximum current output and temperature at various operating conditions. This study has proven that an empirical model can be used to predict the winding coil temperature at various operating condition with a good accuracy.
  • Publication
    New empirical formula for reduction factor of head garment
    ( 2017)
    Muhammad Aiman Ahmad Fozi
    Pressure garment is one of non-surgical method in pressure therapy treatment, which uses pressure as healing mechanism for hypertrophic scars caused from burn injuries. Previous studies proposed a fabrication method based on the modified Laplace`s Law to predict pressure outputs. From the Laplace`s Law, reduction factor is calculated using parameters of modulus elasticity of the fabric, body circumferences, and the targeted pressure. However, most of the previous studies conducted based on lower and upper limbs body parts (arms and legs) which consist more like cylindrical shapes with limited studies conducted for head segment. The aim of this study is to investigate the effectiveness of current methods used for pressure therapy treatment at facial area. Based on investigation and analysis from the current methods in terms of pressure performances, a new fabrication method of head garment is introduced which capable to produce optimum pressure needed for the treatment. This study uses digital design approaches such as 3D scanning, computer aided design and additive manufacturing in design and development phases. Based on the previous reduction factor equation from literature, the produced head garment was tight and not suitable for the treatment. Hence, a new head garment fabrication method is proposed based on empirical approach to determine the reduction factor at particular circumferences of the body parts.
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  • Publication
    Optimal control of the attitude maneuvering for RazakSAT class satellite based on rigid and flexible model
    ( 2018)
    Teoh Vil Cherd
    The increase in demand for performance for satellite capabilities has pushed the design of the system to be more and more power consuming. This is the case for RazakSAT-2, which is a new satellite program that will be equipped with bigger solar panel to generate sufficient power. Thus, this translates to a higher flexibility in the satellite. Satellite mission is known to be highly sensitive to the flexible motions and it is time constrained. Hence, understanding the behavior of the system is required to solve the time constrain flexibility problem. The Floating Reference Frame is applied to obtain the mathematical model of the system which consists of three solar panels. In addition, the model for the actuator is also developed for a four-reaction-wheel system and the Eigen-axis Quaternion Feedback control is also derived. The obtained model is simulated using the MATLAB and ANSYS software for verification of the model. The obtained Percentage Root Mean Square Error falls between 2.015% to 4.841% which is low. Hence, this signifies that the model is sufficient to describe the dynamic of the system. From the model, the control of the minimum time optimal control is developed to minimize the time to achieve desired orientation while minimizing the amplitude of the flexible solar panel. GPOPS toolbox is applied to obtain the optimal control solution. The optimal control is shown to decrease the maneuver time by 3.49% to 25.11% depending on the Eigen Axis of the rotation compared to the conventional Eigen-axis Quaternion Feedback controller. This phenomenon is contributed by two factors. Firstly, the optimal control is able to fully utilize the all the capacity of the reaction wheel while the Eigen-axis Quaternion Feedback controller is plagued by the pseudo-inverse limitation which allows a maximum 35% increases in performance. Secondly, the application of optimal control allows the trajectory to deviate from the effective Eigen axis to achieve faster maneuver by utilizing the torque that is unavailable to the effective Eigen axis maneuver. In terms of the performance of the rigid and flexible model in the optimal control, it shown that the flexible motion converges at 10.53% faster for the flexible model. The primary factor that affects the maneuver time is the natural frequency of the system. The effect of the natural frequency is observed in this section and is shown that maneuver times increase when the natural frequency decreases. For future works, additional parameters such as the stiffening effect, external disturbances and the imbalance mass distribution on the rigid and flexible due to the deflection are studied. This can contribute to a more refined flexible model that would further increase the accuracy of the model.
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  • Publication
    Optimization of processing parameters for physical, mechanical and chemical properties of Khaya senegalensis fuel pellets
    ( 2024)
    Ras Izzati Ismail
    Flourishing even in less-than-ideal conditions, the rapid growth of the Khaya senegalensis (khaya) tree requires regular pruning, presenting a challenge in waste management. To address this, the study proposes repurposing the pruning waste to manufacture energy pellets, offering an eco-friendly solution to waste removal. Pellets offer improved energy density, bulk density, moisture content, and homogeneity, thereby reducing storage, handling, and transportation costs. Notably, there is a lack of scientific gap on using Khaya senegalensis wood for fuel pellet production. To produce high-quality solid fuel, it is essential to comprehend the properties of wood fuel. Due to this necessity, the current study examines the effects of pelletization temperature, pressure, particle size, feedstock moisture content and binder percentages on fuel pellet properties, particularly on their physical, mechanical and combustion characteristics. In this study, the methodology involved determining the fuel characteristics of Khaya senegalensis wood biomass, including bulk density and calorific value, followed by the fabrication of fuel pellets from varying feedstock parameters. The effects of these parameters on pellet properties were analyzed through a parametric study, and response surface methodology was employed to optimize the processing conditions for enhanced pellet quality. The study achieves its first objective by comprehensively assessing the fuel characteristics of Khaya senegalensis wood, with bulk density measured at 258 kg/m³, moisture content (26.06 %), ash content (5.38 %), volatile matter (83.07 %), fixed carbon (15.46 %), and calorific values (16.11 MJ/kg). The second objective involves a parametric study, investigating the effects of pelletizing parameters on mechanical strength and combustion characteristics. The study successfully establishes relationships and optimized conditions for various parameters, presenting statistically significant findings in response analysis. The third objective employs response surface methodology to optimize pelletizing variables for ideal mechanical and combustion characteristics, resulting in well-validated models and predicted optimized values. Design Expert 13 revealed that khaya pellets performed optimally with factor settings of pelletization temperature at 110 °C, pressure at 5 tonnes, and a binder percentage of 9 %. The optimized values for various responses include axial compressive strength at 55.66 MPa, diametral compressive strength at 9.604 MPa, moisture content at 6.93 %, volatile matter at 87.83 %, ash content at 6.54 %, fixed carbon at 5.31 %, calorific value at 19.08 MJ/kg, durability at 99.93 %, and unit density at 1309.37 kg/m³. In conclusion, all the objectives have been successfully achieved, and the research provides valuable insights into repurposing khaya wood waste for sustainable energy pellet production. Understanding wood biomass, solid fuel qualities, and pelletization parameters for this crop could streamline the production of premium-quality pellets from khaya wood, addressing global energy demands efficiently.
  • Publication
    Parametric investigation for single sided and double sided friction stir welding of aluminium alloy 6061-t6 and s275jr mild steel butt joint
    ( 2019)
    Wan Mohd Syafiq Wan Sulong
    Friction stir welding (FSW) is a solid-state joining technique capable of joining aluminum and steel together, which is beneficial to multiple industries such as the automotive, aerospace and chemical industry is attributed by the combined high strength and toughness of steel as well as the corrosion resistance and low density of aluminum alloys. However, joining these two materials together has proven to be a difficult undertaking due to a strong tendency to form large amounts of brittle and hard intermetallic compounds (IMC) at the interface as a result of mutual diffusion during welding. While the growth of IMC layer is minimized in FSW due to the low process temperature, investigation on the influence of welding parameters on IMC layer formation as well as other joint properties such as tensile strength and hardness is required. The appearance of FSW-related joint defects such as tunnel defects, insufficient welding and root defects are also of interest due to its negative effect on joint strength. The influence of double sided FSW (DS-FSW) on joint properties of aluminum-to-steel joints as well as its ability to fix root defects also require evaluation. Several welding parameters were studied and their effects on joint properties investigated: tool offset, tool rotation direction, tool plunge depth, tool travel speed and tool tilt angle. Joints were evaluated based on their microstructural characterizations such as weld zones, IMC layer thickness, grain size in the stir zone and properties such as hardness and tensile strength. Defects formed on the joint such as excessive material flash, insufficient bonding, tunnel defect and root defect were scrutinized. The thickness of IMC layer at the top and middle region of the joint were measured for all joints. Tool plunge depth was seen to substantially influence heat generation and downwards pressure, evidenced by the appearance of tunnel defects at 0.1 mm and thick IMC layers at 0.3 mm and 0.5 mm tool plunge depth. At very low (30 mm/min) and very high (110 mm/min) tool travel speed, tunnel defects were formed. At 1° low tool tilt angle, welding was successfully performed. IMC layer formed in the joint was thinner than ones in a joint produced at 3° tool tilt angle, however at the topmost region of the joint it was thicker. Root defect was observed in all the welded joints. Removing the root defect from tensile specimens of several joints by machining was found to substantially increase the joint strength as fractures no longer initiate at the root defect. However, several joints without root defect still fractured at the interface, which was determined to be caused by thick IMC layer at the crown. Double sided FSW (DS-FSW) was investigated as a possible method to eliminate root defects without material removal by machining. It was found that using DS-FSW with a 4.5 mm and 4.0 mm tool pin length was successful in removing the root defect, however joints still fractured at the interface. It was found that thick IMC layers were formed at the 1st side crown of the joint. By performing DS-FSW using shorter tool pins of 3.5 mm and 3.0 mm, root defects were successfully removed and the joint fractured away from the interface, signifying satisfactory bonding. The IMC layer thickness along the depth of joints were measured to investigate DS-FSW’s effects. It was observed that longer tool pins resulted in thicker IMC layer and vice versa.
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  • Publication
    Performance evaluation of shell-and-double concentric tube heat exchanger
    ( 2016)
    Mohd Shahril Shariff
    Shell-and-tube heat exchangers (STHEX) have been used for several decades. Conventionally to increase the thermo-hydraulic performance of classical heat exchangers, overall length of tubes has to be increased. This contributes major disadvantage in term of classical heat exchangers design particularly considering economical aspect. In this study, the thermo-hydraulic performance analysis of a shelland-double concentric tube heat exchanger (SDCTHEX) is carried out using commercially the available Computational Fluid Dynamic (CFD) software ANSYS FLUENT 14.0. A 3D realizable k–ε turbulence model with scalable wall function treatment is used for the whole numerical simulations. Validation on heat transfer coefficient and pressure drop are done, where the Bell-Delaware method, Gnielinski, and Haaland correlations are compared with CFD simulation values of SDCTHEX and classical STHEX. The SDCTHEX model is then compared with classical STHEX model for their thermo-hydraulic performances for different mass flow rates of the hot fluid. Next, the effects of different inner tube diameters and different arrangement (counter and parallel flows) flows of working fluids flows on the performance of SDCTHEX are investigated. Other than that, the effects of the heat transfer and pressure drop of Al2O3/water nanofluid at different Al2O3 nanoparticle volume concentrations and flow rates flowing inside annulus side of SDCTHEX are also analysed. It is observed that, the percentage of overall heat transfer rate per overall pressure drop of SDCTHEX with inner tube diameter equal to 8/12 mm/mm, is increased nearly 343 % higher than that of STHEX. Also, the overall heat transfer rate per overall pressure drop of SDCTHEX is sensitive to inner tube diameter. It is found that Φ/ΔP for the mass flow rate of 22.5 kg/s is for to be maxed about 400 % higher at inner tube diameter of 12/16 (mm/mm) with respect to the STHEX. On the other hand, the thermo-hydraulic performance for counter flow arrangement of working fluid is also found higher than that of parallel flow arrangement of working fluid at any hot fluid mass flow rate. For the nanofluid effect, the results obtained showed that at the same Re, the heat transfer performance increases by increasing the nanoparticle volume concentration and it’s valued higher when compared with water. But when compared at the same mass flow rate, the nanofluid at any nanoparticle volume concentration does not show any enhancement on heat transfer when compared with water.