Theses & Dissertations

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  • 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.
  • Publication
    Experimental and numerical investigations of the performance of three concentric pipes heat exchanger
    ( 2010)
    Saqab S. Jarallah
    The three concentric pipes heat exchanger is a slightly modified version of double tube heat exchanger. Although the heat exchanger designs have shown extensive progress, they are generally limited to few of many possible flow arrangements and mostly restricted on two fluid heat exchangers. A three concentric pipes heat exchanger is fabricated wherein three fluids, namely hot water, cold water, and normal water flow with different temperatures and also with different mass flow rates. Experiments were conducted for different mass flow rates of the hot, cold, and normal fluids for co-current and counter-current flow arrangements under insulated and non-insulated conditions of the heat exchanger. Two flow combinations for the fluids are taken, first when the cold water flows through the outer annulus, and the normal water flows through the inner pipe, and the second when the cold water flows through the inner pipe and normal water flows through the outer annulus, by allowing the hot water to flow through the inner annulus in both combinations. It is found that the temperature variation in the first combination is better than the second one where the drop in outlet temperature of the hot water is higher. Finite element method is used to predict the temperature variation of the three fluids along the length of heat exchanger by developing a computer program using MATLB software. It is found that the numerical predictions of the temperature variation of the three fluids by using the finite element method follow closely to those obtained from experiments both in magnitude and trend. The analytical expression available in the literature to predict the crossover point in terms of its location is found to be satisfactory in the present investigation. Finally, from the parametric analysis of the insulated heat exchange, it is found that the 1 R and NTu affect strongly on the thermal performance ,Similarly, from the parametric analysis carried out for the noninsulated heat exchanger, it is found that there is a pronounced effect of ¥ NTu on the temperature variation of the three fluids especially on the outlet temperature of cold water for the range of the surrounding ambient temperature considered in the present analysis. For ¥ NTu 0.05, the percentage change in outlet cold water temperature is found to be 12.42% when the dimensionless ambient temperature varied from -0.25 to 0.5. This percentage change increases to 23.29% when ¥ NTu is further increased to 0.1 while, for other design parameters, the percentage change in temperatures are nearly constant.
  • Publication
    A study of quality tools and techniques employed in Perlis and Kedah manufacturing companies
    ( 2010)
    Che Padzilah Yaacob
    Quality tools and technique can be used to achieve continuous improvement of quality in the manufacturing industry. This research is focused on manufacturing companies located in the states of Perlis and Kedah. The study examines whether manufacturing companies employ quality tools and techniques in their daily operations. In addition, it identifies the problems and challenges faced during the implementation of the tools and techniques on the manufacturing shop floor. The study uses mail questionnaires and structured interviews as its main instruments of data collection. In this study four hypotheses are developed based on the theoretical framework, of which the variables are in the categories of independent, dependent and moderating variables. Independent variables comprise of company location, number of years the company has been operating (referred to as “level of maturity”), annual sales turnover, number of full time employees, product(s) of the company, and quality standard certification. Meanwhile, the dependent variables are the issues in the implementation of quality tools and techniques, and how quality tools and techniques help the companies. Moderating variables in this research are the actual use of quality tools and techniques and information regarding the respondents who answered the questionnaire on behalf of the company. Data was analysed using independent T-Test and one-way analysis of variance (ANOVA) and the results helped to identify the problems and challenges faced during the implementation of the tools and techniques. The findings of this study reveal that quality tools and techniques are indeed being used by the companies but each with varying degree. The results reveal that companies that implement ISO 9000 quality system tend to use more quality tools and techniques compared to companies without quality systems. The study indicated that high sales turnover has no impact on planning, budget and training as well as the implementation of quality tools and techniques. It also indicates that the level of maturity does not have any bearing on the implementation of quality tools and techniques. Lastly, higher numbers of work forces do not necessarily bring about issues of communication and teamwork in order to implement quality tools and techniques in the company. In conclusion, the overall results from this study show that training, teamwork, communication, planning, and budgeting have no impact at the companies in Perlis and Kedah.
  • Publication
    Study of plasma cutting efficiency with different operating parameters
    ( 2010)
    Masita Raja Mohammad
    Plasma, a fourth state of matter distinct from solid or liquid or gas and present in stars and fusion reactors; a gas becomes plasma when it is heated until atoms lose all their electrons, leaving a highly electrified collection of nuclei and free electrons. The usage of advanced machining, such as Plasma Arc Cutting machine to cut Mild Steel, Copper Alloy and Aluminium was very limited in the industry. Selco Genesis 90 Plasma Arc Cutting machine was used to cut Copper Alloy, Aluminium and Mild Steel in this study. The usage of Taguchi approach Design of Experiments from the designing steps until the analyzing phase from the experiment was used. In this study, Design of Experiment L-9 (34) layout is used. In this study, the parameters determined were the air pressure [bar], current flow rate [A], cutting speed [mm/min] and arc gap [mm]. These parameters used to analyze the setting required for optimizing the process variables for Plasma Arc Cutting machine to gain the best combination. The effect of these factors was the calculation of Material Removal Rate (MRR) and Surface Roughness (Ra). Confirmation test must be done to confirm the value estimated through the software. The confirmation run was done by using the setting gain from the software. The estimated optimum value and the actual value obtained from the confirmation test that is allowed are in range 10%.
  • Publication
    Effect of heat treatment on hardness and wear properties of an aluminum alloy of motorcycle piston
    ( 2010)
    Mohd Fizam Zainon
    The present study was undertaken to investigate the effect of heat treatment on the microstructure, hardness and wear of aluminum alloys piston and with the aim to improve the mechanical properties by using heat treatment method. The material is from aluminum alloys piston; produced by one of Malaysian piston manufacturer and using on four-stroke of “National Motorcycle” engine. The as received piston contains alloying elements of Al, Si, Cu, Mg, Ni and Fe alloys with 8wt% Si. The solution treatment was performed at 500⁰C for 5 hours and then quenched in water at room temperature. Aging treatments were carried out at 130⁰C, 170⁰C and 210⁰C for 1 hour to 6 hours to observe the effect of aging condition on microstructure and mechanical properties. Microstructural analysis was carried out by using an optical microscope equipped with digital camera and a Scanning Electron Microscope (SEM). The hardness measurement was carried out by using a Vickers microhardness tester. A dry sliding wear test has been conducted by using pin on disk test. Volume loss, wear rate and wear coefficient were evaluated under un-lubricated conditions at loading conditions 10 N, sliding speeds 1.0 m/s, and sliding distances of 0.1, 0.25, 0.5, 1 and 2 km. The results showed, after full heat treatment the microstructure consists hard participates such as Al6Cu3Ni, β (Al5FeSi) and Mg2Si. The structure of Si particles form as acicular plate (rounded shape).Compare to as received, the results on microhardness after aging at 130⁰C show increases from 12.67% to 34%. While aging at 170⁰C shows increases from 28.06% to 46% and aging at 210⁰C shows increases from 25.29% to 44.36%. The result on wear test on the aged shows that was a reduction in wear rate 14.01% to 56.63% compared to that of as received. While, the wear coefficient of aging samples show lowest 3.09% to 42.15% from as received. The results showed that aging temperature of 170⁰C for 2 hr is the best condition the highest hardness and wear resistance of the aluminum alloys piston.
  • Publication
    Design and development of a dynamic-active cloth washing process
    ( 2010)
    Heap Yee Nean
    This thesis describes washing performance of a new introduced washing process. A laboratory washing model is developed to simulate the dynamic-active cloth washing process. It is the mechanical washing principle which combines deflection and abrasion actions due to hydrodynamic and impact water jet working liquid to wash the cloth. Complex dynamic fluid motion creates direct interaction between working liquid and washed cloth hence produce active washing. In the washing machine research area, engineer is interested in improving the washing performance by investigating its washing time, temperature and the mechanical action that depend on motion of rotating force or agitation effect acting on the washed cloth. The purpose of this study is to find the major contributing factor to optimum washing of the washing process. Data comparison in term of the washing efficiency has been performed between the laboratory developed model and the commercial washing machine modelled Samsung WA91U3. Result shows that the most significant factor contributes to optimum washing for developed model is washing time while the commercial washing machine depends major on the washing speed. Soil removal test indicates dynamic-active cloth washing process of developed laboratory model is about 50% more efficient than the current washing machine compared.
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  • Publication
    Classification of stainless steel and mild steel using vibration technique
    ( 2011)
    Intan Maisarah Abd Rahim
    The production of material in industry must attain some standard such as the standard required by American Society for Testing and Materials (ASTM) International. The requirement of the material standard is important in some crucial field such as aerospace, engineering and automotive. This research presents a development of a material classification scheme with non-destructive testing on the material to classify the material type. The classification of the material can be useful in post-production verification. Many testing methods have been developed to reach the standard of the material production. The testing of the material mechanical properties using vibration technique could determine the natural frequencies, the damping ratio and mode shapes of the structure. The testing method chose to be implemented in this research is impact hammer testing. Frequency Response Function (FRF) signals obtained from the testing and natural frequencies of the materials are extracted from FRF signals. In this research, the features considered as the input data for the algorithm training are the natural frequencies of the material and its amplitude. Later, the input data obtained are classified using Artificial Neural Network (ANN) with Levenberg-Marquardt Backpropagation and k-Nearest Neighbor (k-NN). Each of the classifier produced a different classification rate depending on the performance of the training input data set. The result from the classification system shows that k-NN is giving the accuracy of 99.69% with the k value of 3. While, Levenberg-Marquardt Backpropagation is giving the best classification rate of 99.43%.
  • Publication
    Methodology development for ccalculating productivity and its losses to determine optimization regime in assembly line
    ( 2011)
    Abdul Rahman Riza
    Modern manufacturing system requires high rate productivity with low cost unit price to maintain its competitiveness in global market. To achieve these goal common investigation of productivity in manufacturing especially in assembly line environment consist of two main purposes: (1) To determine potential reserve of productivity in actual production condition, and (2) To provide initial parameter for planning a new process arrangement based on prior experience of actual operating arrangement. The calculation of productivity itself shall easily be applied for various kind of assembly type such manual, automatic or hybrid and also may cover the complexity of various models of products its produces. By using chronometric analysis as the statistical basis, the formulation for productivity calculation must cover all its complexity mathematically. The result of productivity calculation should be compared to graph of price per unit under the same domain to determine the range of optimization regimes. The final result is reliable important data for corporate decision makers to choose the optimum configuration between the most economical configuration and the most productive configuration.
  • Publication
    Numerical simulation of roadside safety barrier for crashworthiness assessment
    ( 2011)
    Rahmad Paruhum Nasution
    Nowadays, even with modern traffic safety regulations, some high risk accidents still occur. Many fatal injuries or even death accidents occur to road users. The research of safety levels for all road users has been developed over the years. Roadside safety barrier is one of the systems that have been developed to reduce number of fatal injuries. In order to employ the suitable safety barrier at a referred location several test must be perform. Many of these tests only focused in a high velocity impact because it is considered that high speed impact can cause major injury to the occupant, damage to the safety barrier structure and also vehicle. Because of this consideration minor research has been perform for low vehicle velocity. However low velocity impact can also cause injuries to the occupants and damage to the vehicle and safety barrier structure. The objective of this study is to perform impact simulation on low vehicle velocity and analyze the occupant injury risks, safety barrier structure and concrete foundation failure criteria. The crash simulation is between W-beam type safety barrier to a light vehicle applied with three types of impact velocities (40, 60 and 80 m/hour). The situation model of the crash refers to a real road profile located at Jamin Ginting Street, Medan, Indonesia. The simulation models consist of four main parts that are roadside safety barrier, concrete foundation, light vehicle and the road. American Association of State Highway and Transportation Officials (AASHTO) specification was used to develop the safety barrier models. All the main parts were developed from CAD software then exported to Finite Element Analysis (FEA) software. The simulations are carried out using LS DYNA, commercial FEA software. The foundation of the W–Beam barrier and the occupant injury risks were analyzed. During the impact the maximum load that occurred at the foundation was below the allowable load. The Acceleration Severity Index (ASI) value of all impact velocities was still at the acceptable range.
  • Publication
    Effects of filler components on mechanical properties and machinability characteristic of palm oil based wax
    ( 2011)
    Mohd Faizal Hamid
    This thesis presents, a comprehensive study on the blends of palm oil based wax with filler components such as linear low polyethylene (LLDPE) and high density polyethylene (HDPE). The work targets the development of cheap industrial wax made from palm oil. The blends studied comprised of commercial industrial wax for prototyping Computer Numerical Control (CNC) machining purpose. Morphological analysis also has been carried out to investigate microstructure before composing filler and after filler compositions. The experiment results show that different kind of filler will affect mechanical properties and will attribute to strength of blends materials. The effectiveness of compatibility filler was evaluated using different techniques like thermal, mechanical and scanning electron microscopy via morphology study. Best compatibilization effect was found in the blend at loading of 30%wt LLDPE + 20%wt raw palm oil based wax + 0%wt palm oil fiber for LLDPE filler and 70%wt HDPE + 20%wt raw palm oil based wax + 0%wt palm oil fiber for HDPE filler where at these compositions, the tensile strength is at the highest level. LLDPE filler blends was awarded best smooth surface after obtain 1.966μm (Ra) value.
  • 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
    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
    Design and development of an impeller wind turbine
    ( 2013)
    Ahmed Younus Qasim
    In the area of wind turbine design, there is still scope of improvement. Today, wind energy - mainly by wind screw turbines - produces less than 1.0% of the total energy used worldwide. Practically, the efficiency of the standard three-blade wind screw turbines is around 30%. This type of turbine is based on the wind lift force on rotating turbine. These turbines are quite expensive due to the complex aerodynamic shape of blades that are made of composite materials. A vertical axis wind turbine can be designed with high value of the drag factor. The present work relates to the design of a new impeller type vertical axis wind turbine, which is uses wind energy more effectively. This design presents a special frame design with vanes. The frame wind turbine is designed to increase the output of a wind turbine that uses kinetic energy of the wind. Five different models of the vertical axis wind turbine are fabricated and tested in a wind tunnel in the present work. They are three frame movable vane cavity shape, three frame movable vane cavity shape with amplifier gear, three frame fixed vane cavity shape, four frame movable vane cavity shape and three frame movable vane flat plate shape. The vanes are located on vertical bars installed in hinges of the frames. Such a design enables the rotation of the bars with frames under the action of wind force simultaneously at one direction and independently at other directions. The frames are connected with the shaft, of which one end is connected with the electric generator. The frames are designed with angular inclinations of vanes that create cavities when vanes are closed. On the other side of the impeller, when the movable vanes are open, and the frame is under wind action, the air passes freely through the frame, and decreases the negative torque. In all the models using cavity shaped vanes, 45˚vane angle is used.The results are presented in the form of drag coefficient, power coefficient, tip speed ratio for wind velocities varying from 5 m/sec to 17 m/sec. It is found that a three-frame movable vane cavity shape model has a maximum power coefficient (Cpmax) of 0.32 at a wind velocity 8 m/s and tip speed ratio 0.31. All other models give the values of Cpmax lower than this value for the same range of wind velocity. The proposed new impeller type vertical axis wind turbine can be used worldwide due to its high efficiency, simple construction, and simple technology. Further, the proposed wind turbine can also be made from cheap materials.
  • Publication
    Reliability analysis based on Weibull distribution and failure mode effect and criticality anaysis
    ( 2013)
    Suhaireza Md. Isa
    In manufacturing industry breakdown due to machine failure affect the product quality, customer satisfaction and product performance. However it is important more over difficult to control and decreasing failure due to unplanned failure. This situation gives a big impact since it leads to product defect, decreasing of performance and increasing of maintenance cost. One of the strategies is using the reliability analysis as the medium to develop a proper maintenance. This reliability analysis identified the characteristics of the failure and the reliability of the machine. For this research two method of reliability analysis used are Weibull distribution and failure mode effect and criticality analysis. For Weibull distribution the quantitative data of the time to failure is applied. Time to failure data is the range of time from the first failure to the next failure to happen. Where in failure mode effect and criticality analysis the data used are the failure mode, failure cause and effects and its probability. These data based on failure data provided from three critical machines on the Camshaft line of automotive manufacturing industry in Malaysia. For this reliability analysis, Weibull distribution analysis ends up the results with the state of characteristics and behaviour of the machine failure. State of the failure characteristics are able to use as the guideline for future analysis of proper maintenance development. Moreover, the value of parameter on the characteristics and behaviour of the failure state leads to estimation of mean time to failure. Meanwhile, from the failure mode and failure cause and effects results leads to identification, classification and clarification of the failure mode and its criticality ranks. In the criticality matrix the degree of seriousness for the critical failure mode is more clearly viable. The criticality matrix leads to decision of corrective action taken with the consideration of safety factor and occurrence of failure. Therefore, the combination of reliability analysis and failure mode and failure cause and effects on machine failure presents more clear and specifics results.
  • Publication
    Optimization of MIG welding process parameters on mechanical properties of Al-MS-SS materials
    ( 2013)
    Nik Nur Fatihah Che Hassan
    Applications of welding process in the industry mostly involve the resistance of an object to resist the force applied. As such, the tensile strength and hardness of welding must be considered. The Metal Inert Gas welding is used to joint two plates of Aluminum, Mild Steel and Stainless Steel in butt joint type based on the selected parameters. The specimens used are 3mm thickness. Analysis of tensile strength using Ultimate Tensile Machine and hardness (Vickers Hardness Test) has been carried out on the surface of welding area. The highest values of tensile strength and hardness test were recorded. Taguchi method is used for design of experiment in order to obtain the optimum value for each analysis tested. The highest of Signal-to-Noise ratio graph for each parameter provide results of optimal values for each type of material. Analysis of Variance was carried out to identify the percentage of parameters contributions to the tension of a material. Confirmation tests carried out on the basis of optimum parameter which has been analyzed and found there was an error between predictions of optimal value and the actual experimental values. However, microstructure analysis has been done to support the results of the experiment. The images of penetration shown by Scanning Electron Microscope for Mild steel specimen are the highest penetration than others. The findings of the optimal value and table of results obtained can be used as a reference for various applications for metal inert gas welding in industry.
  • Publication
    Optimization of machining processes by using criteria of maximum productivity and minimum cost
    ( 2013)
    Aead M. Ahmed
    In manufacturing, the machining process by using norms of the maximum productivity and minimum cost is knotted. In many cases, the increase of machining modes leads to an increase in productivity, and the machining cost also increases. The present thesis formulates a set of mathematical models that enable the setting of maximum productivity and minimum cost parameters on machine tools. Three new mathematical approaches have been developed to achieve this objective. In the first approach, maximum productivity is given as a function of the increase of cutting speed at (x) time equal 0.93. The second approach focuses on optimizing multi tool machining process with simultaneous actions. Here, the maximum productivity at (k) factor, which is 1.28 of changing the cutting speed, has been derived. Whereas in the third approach, maximum productivity and minimum cost for single and multi tools are presented. The equations are useful in modeling and predicting the processing mode that will give maximum productivity and minimum cost. By keying in the developed mathematical expressions in MATLAB, the productivity of the machine tool is calculated. This work has been carried out under dry conditions. The results give the optimum cutting speed (Vopt) at maximum productivity for a single cutting tool for high speed steel and carbide as a theoretical. Whereas by keying a diameter of work piece is 25mm, depth of cut 2mm and feed rate 0.21mm/rev, which are achieved experimentally, the proper cutting speed for HSS of the tested materials is 50 m/min. whereas the optimum cutting speeds of cutting tool machining process of the different materials as a theoretical of maximum productivity for cemented carbide is 95 m/min. whilst for the multi cutting tool of the same materials the maximum theoretical productivity is obtained at 80 m/min. whereas the optimum cutting speeds for the multi cutting tool machining process of the same materials as an experimental for maximum productivity at 75 m/min. However, increasing the machining regimes leads to an increase in both of machining cost and productivity. In the minimum cost approach, which is a proper cutting speed of the tested materials is 46 m/min. The convenient range values of multi-cutting speed for both productivity and cost obtained in this work is 40 to 90m/min, and a favorable range of cutting speed is 40 to 60 m/min to get the minimum cost. The appropriate range of cutting speed of the mathematical model for the productivity for single and multi -cutting tool for intermediate hardness of work piece material is 35 to 69 m/min, 50 to 90m/min, respectively. Although both theoretical and experimental data sets show similar behavior, there are slight deviations within acceptable range for the two data set values.
  • 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
    Stress corrosion cracking behavior of austenitic stainless steels in natrium chloride solutions
    ( 2013)
    Samir Milad Elsariti
    Stress Corrosion Cracking is an environmentally assisted failure caused by contact to a corroding while under a sustained tensile stress. Stress Corrosion cracking is most often rapid, unpredictable and catastrophic. Failure can occur in as little as a few hours or take years to happen. Most alloys are susceptible to Stress Corrosion Cracking in one or more environments requiring careful consideration of alloy type in component design. In aqueous chloride environments austenitic stainless steels and many nickel based alloys are known to perform poorly. One of environment is Natrium Chloride. This contains natrium chloride with concentration 3.5wt% NaCl and 9.35wt% NaCl. Austenitic stainless steel is usually used in distillation construction tank and pipe line in many different industries especially petroleum. So, Austenitic stainless steel has been used as a substitute for carbon steel in corrosive environments, however, brittle type failures were encountered due to stress corrosion cracking. Stress Corrosion Cracking in natrium chloride solution is one of the most prevalent forms of Stress Corrosion Cracking in Austenitic Stainless Steels. Component life prediction requires Stress Corrosion Cracking initiation and failure time from published data, however, such data are limited. In this research, experimental equipments were used for gathering data on the incubation period and the crack time about last of 70 days for types 304, 310 & 316 Austenitic Stainless Steels immersed in 3.5wt% & 9.35wt% NaCl solutions at room temperature which is similar to Sea water and Sabkha (salt-flat). The use of the equipment was verified by conducting a standardized test. The experiment uses a spring loaded fixture type and is based on ASTM G49 for experiment method, and E292 for geometry of specimen. The stress corrosion cracking of the austenitic stainless steels of types 304, 310 and 316 in natrium chloride solution at room temperature is investigated as a function variation of chloride concentration, using a constant load method with one of initial tensile stress as 90% yield strength. Potential scans of selected types of Austenitic Stainless Steels were performed in an attempt to determine the Stress Corrosion Cracking and also they were tested to conduct their mechanical and chemical properties by using such as Scanning Electronic Microscopy and Universal Testing Machine. Detail equipment being used and justification of results obtained are explained in full details in this thesis. In production process, concentration of natrium chloride in sea water and sabkha (salt-flat) become more effective to those industries since those are the surrounded environment. And that reason is that the experiment is conducted in natrium chloride concentration such as 3.5wt% and 9.35wt% NaCl. Pitting corrosion occurs on the surface of specimen’s notch area in different stages on different types of those selected Austenitic Stainless Steels. Austenitic Stainless Steel 304 was more susceptible for all conditions. In natrium chloride solution with concentration of 3.5wt%, all specimens do not show any cracking for first stage of 404 hour of test time. The higher concentration natrium chloride and the same stress level, the crack speed increase with same time failure. And recommendations for future experimental work are presented herein.
  • Publication
    Inspection model development for production machines based on downtime record
    ( 2013)
    Nur Hazirah Sa'ari
    In the production line, the main objective of the machines to provide the good quality of products at the time given and follow the customer requirement to accomplish customer’s satisfaction. To reach the objective, the production line should running in smooth flow without or less breakdown. Nevertheless, the real production with the ineffective maintenance strategy becomes barrier to the production to achieving the objective. Reasonably, this problem contributes to high production lost, production defect due to reject product (if the breakdown occurs during the machine is operating) and increasing the maintenance cost. Inspection is one of the Preventive Maintenance (PM) strategies that can be used to reduce machines breakdown problem in the production line. Conversely, the application of inspection in term of how many times of the inspection should be done at the unit of time (such as per month) is the main issue. To answer this question, an adequate maintenance analysis based on inspection must be accomplished. Most of the existing study is focus to inspection of single machine at the state of constant failure rate. There is no consideration for machine in the state of decreasing and increasing failure rate. Hence, the inspection strategy introduce to the machine at decreasing failure rate state to give extra value to the production machines by reducing machines breakdown due to continuous monitoring the machine condition and do correction or maintenance if needed. In this research, an inspection model of maintenance analysis by considering the failure time of the machines is developed in order to determine the optimal inspection frequency of the critical machines in the production line. In addition, the inspection strategy that used can maximize the output of production machines in term of product and service. In order to confirm this model, a case study was carried out on the automotive industry in Malaysia. The result from failure analysis have identified that all the critical machines in the state of decreasing failure rate and the failure characteristic information was used for the next analysis. Result shows that the machine follows the Weibull distribution and for inspection modeling also used the Weibull function to identify the inspection frequency for the critical machines. Therefore, the result shows that have relationship between two inspection model base on profit and downtime.
  • Publication
    Optimization of cutting parameters for surface roughness in CNC turning machining with aluminum alloy 6061 material
    ( 2014)
    Ali Abdullah Mohammed Ahmed
    Machining process involves many process parameters. Achieving accurate dimensions, good surface quality, and maximized metal removal are of utmost importance. This research work describes the optimization of cutting parameters for the surface roughness in CNC turning machining with aluminum alloy 6061 material. Controlling the required surface quality is necessary. In this study, Taguchi method is used to find the optimal cutting parameters for surface roughness in turning. L-9 orthogonal array, signal-to-noise ratio, and analysis of variance are employed to study the performance characteristics in the turning operations of aluminum alloy 6061 using uncoated inserts. A precise knowledge of these optimum parameters would facilitate reduction of machining costs and improve product quality. The current study on turning process applies a response surface methodology on the most effective process parameters, namely, feed, cutting speed, and depth of cut, which are optimized considering the surface roughness and material removal rate. The results of the machining experiments were used to characterize the main factors affecting surface roughness by the Analysis of Variance (ANOVA) method. Feed rate and speed of cutting founds to be a most influencing parameter for the surface roughness in the shaping process whereas depth of cut is found to be significantly affecting the MRR.