School of Mechanical and Industrial Engineering

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A Heuristics and Discrete Event Simulation for Optimized Layout Design in Agricultural Machinery Maintenance - A Case Study of Wereta International Business Plc.
(Addis Ababa University, 2024-07) Fitsumberhan Hailemeskel; Ameha Mulugeta (PhD); Ayele Legesse ((Mr.) Co-Advisor
Agricultural machineries play a vital role in agricultural processes and help in the production of food and non-food items. The efficient layout of agricultural machinery maintenance facilities is crucial for minimizing process times and maximizing throughput. This paper deals with the development and optimization of an agricultural machinery maintenance facility using discrete event simulation considering Wereta International Business Plc.’s agricultural machinery maintenance facility layout as a case. The development of the facility layout is done in a way that introduces flexibility of departments and also that combines the different services given in the facility, maintenance, training (customer & staff) and pre-delivery inspection processes. The research tries to construct a new facility layout that decreases the travel distance, considers the relationship between departments using the CORELAP facility layout construction method. The newly constructed facility layout has been optimized using facility layout improvement technique, CRAFT (excel add-in) to further enhance the optimality of the facility layout by enhancing the material flow between departments to minimize the material handling cost. Finally, an improved facility layout, with 15 departments that include main and supporting facilities and also combines the services and training facilities is developed. The proposed facility layout reduces that has been constructed from scratch and then optimized decreases the distance traveled between departments by 2,015.11 meter (a reduction of 33.66%) and the total monthly material handling cost by 531,093.14 Birr per month (a reduction of 86.85%). The entity output of the existing system is 40 units and for the proposed layout, the entity output is 67, an increase by 67.50%. Also, the system output from the existing simulation model is 125.30 units and the proposed layout simulation modeling system output increased by 58.85% to 199.04 units.
Abrasive Wear Behavior of Bamboo Reinforced Polymer Composite with PTFE
(Addis Ababa University, 2020-06) Sentayehu, Worku; Eyasu, Woldesenbet (Prof.)
The aim of the present work is to study the abrasive wear behavior of composites made by reinforcing bamboo fibers with the addition of PTFE and thermoset resin matrix. The fibers are extracted by hand and manual process and the composite samples were prepared to a maximum of 30% volume of fiber. Wear tests were carried out in dry conditions on a pin-ondisc which is modified by me and the machine at a constant sliding distance of 1000 m with sliding velocities of 2m/s and 4m/s and normal loads of 15N and 30N. The effect of PTFE content on abrasive wear properties of composites were investigated and compared with pure BPC composites made under the similar testing conditions. It is observed that the wear loss of composites increase with increase of normal load whereas the specific wear rate decreases. The optimum weight loss and specific wear rate for bamboo fiber reinforced composites were obtained at 30% volume of pure composite.
Adoption of Additive Manufacturing for Auto Parts Production: Case of Bishoftu Automotive and Manufacturing Industry
(Addis Ababa University, 2023-10) Sultan Asefa; Ameha Mulugeta (PhD)
This study investigates the adoption of additive manufacturing in the Bishoftu Automotive Industry in Ethiopia. The study applies an integrated framework of Diffusion of Innovation (DOI) and Technology-Organization-Environment (TOE). This study also used combined data from primary and secondary sources using quantitative and qualitative methodologies to allow for the exploration of the factors and constraints influencing the decision to adopt additive manufacturing. Additionally, the research undertakes a thorough literature analysis of Adoption theories such as DOI, TOE, and factors affecting additive manufacturing adoption. Five point Likert scale was the method used to collect the useful information for this study. The questionnaire was distributed to managers, engineers, and technicians in the Bishoftu Automotive and Manufacturing Industry. Subsequently, the collected data was subjected to analysis through the application of descriptive statistics and partial least squares structural equation modeling (PLS-SEM) utilizing SPSS version 27 and SmartPLS version 4.0.9.6 software. The study outcomes revealed that several critical determinants significantly impact the adoption of additive manufacturing (AM) in the automotive sector. These determinants encompass relative advantage, compatibility, complexity, trialability, observability, technology-related factors, and organizational as well as environmental factors The results of this study enhance our understanding of the adoption of additive manufacturing and provide valuable practical guidance for decision-makers within the Bishoftu Automotive Industry. Drawing from these findings, recommendations have been formulated to facilitate the effective integration of AM in the automotive sector. Additionally, this study identifies potential areas for future research in this field.
Adoption of Nanotechnology in case of Ethiopian Textile Industry
(Addis Ababa University, 2023) Biruk Wondemneh; Birhanu Beshah (PhD); Gebrewold Teklay (Mr.) Co-Advisor
Nanotechnology provides plenty of efficient tools and techniques to produce desirable fabric attributes, mainly by engineering modifications of the fabric surface. Due to the advancement of Nanotechnology in the manufacturing of fiber or yarns including the development of fabric finishes, the applications and scopes are widespread in the area of textiles for the last few decades. According to this research study the existence and the application of Nano technologies with in Ethiopian textile industries are very minimal or we can say it does not exist. So we listed enablers which will introduce Nanotechnology and used a multi criteria decision making method MCDM to rank which is more effective to implement Nanotechnology among the listed enablers and according to the research result the government is highly capable to introduce and implement Nanotechnology within the Ethiopian textile industries. Government can mobilize market, technical, financial institution and socio economic activities to introduce Nano technology within textile manufacturing industries. The introduction and implementation of Nano technology by the government with in textile manufacturing industries could be easier than the other alternatives. The implementation of Nano technology within textile manufacturing industries enhances the quality of the textile and the development of manufacturing industries.
Aerothermodynamics Analysis of Axial Flow Aircraft Gas Turbine Engine Compressor
(Addis Ababa University, 2009-10-05) Tilahun, Nigussie; Tesfaye, Dama (PhD)
The axial flow type compressor is one of the most common compressor types in use today. It finds its major application in large aircraft gas turbine engine like those that power today’s jet aircraft. Early axial flow aircraft engine compressors had pressure ratio of around 5:1 and require about 10 stages. Over the years the overall pressure ratios available exceed 30: 1 due to continued aerodynamic development that resulted in a steady increase in a stage pressure ratio with reduced number of stages. There has been in consequence a reduction in engine weight for a specific level of performance, which is particularly important for aircraft engines. These potential gains have now been fully realized as the result of intensive research into the Aero-thermodynamics Analysis of Axial Flow Aircraft Gas Turbine Engine Compressor. Therefore, careful design of compressor blading based on aero-thermodynamic theory, experiment and computational fluid dynamic (CFD) analysis is necessary not only to prevent useful losses but also to insure a minimum of stalling troubles. The complete analysis of this thesis is done to provide some part of design of an axial compressor suitable for a simple low-cost and low weight turbojet Aircraft Gas Turbine Engine Compressor by using different research work on the aero-thermodynamic analysis of the compressor. Details of CFD analysis on the models of the compressor, using a commercial software “FLUENT”, will be presented. The CFD simulation predictions were validated quantitatively against the experimental data and the theoretical (calculated values) were then used to obtain further insights into the characteristics of the flow behaviors. To calculate the work and power required by the compressor to sustain the flight, the blades of the compressor will be modeled, and the required equations will be developed. Finally a small scale computer program will be developed to calculate the power (work) required by the compressor and to determine other performance measuring parameters.
Alleviating Scheduling Problems in Anbessa City Bus Service Enterprise
(Addis Ababa University, 2009-09) Hailu, Gemechu; Tafesse, Gebresenbet (PhD)
The transport sector is a key element for the development of a country. Almost every item or human being participating in the national economy needs to be transported from one location to another. Thus a problem in the transport sector implies impediment of the development of the socio-economic status of the country. It has become very common that globally emphasis is given to the transport sector. Hence, the modes of transport are diverse, efficient and effective in many countries. City Trains, city Buses, Midi Buses, Taxies, Express Cabs are among the transport means that facilitate city transport services. However, the existences of all these modes of transport dose not guarantee satisfactory transport service. The modes of transport shall address the customers by making themselves available at the time and place they are required. To keep the time and place of destination and departure of means of transport different measures are taken by different countries. Among these are; using different bus lanes on streets, and making appropriate scheduling and time tabling of the different modes of transport. However, the case in our country, specifically, the capital city Addis Ababa, is different in that there is no city train service, the road ways are narrow and not well maintained, they are also un proportional to the number of vehicles available in the city, there is no bus lane, etc. Moreover, the city bus service is the only public transport having a specific route of travel and governed by governmental development agency. The private transport sector is not controlled under a specified route and gives service based on the best advantage of the owner rather than the public. Consequently, the public is suffering from shortage of transport to make its daily activities. These factors have aggravated the problem of city transport in Addis Ababa. The main objective of this thesis is to alleviate the problems of city transport described above through improving the scheduling system of Anbessa City Bus Service Enterprise. The paper gives emphasis on the way that the public gets the required transport service on the time and place which the customer specifies and on the continuity or dependability of the schedule insuring this service. This is done by identifying the core problem of the public transport in relation to the city bus service through delay data collection, questionnaire distributed and interviews conducted to the customers. Finally, appropriate method of data collections and trip time determination for making schedules, timely updating of the existing data for keeping the schedule dependable, consideration of all route disruption factors for sustainability of the feasibility of schedules are recommended. The result of the study can improve the service delivered by the enterprise and shift the customers who are dissatisfied by the private transport sector to Anbessa buses increasing the market share of the enterprise in the city transport service. It will also improve the mobility of resources which is a key factor for improving the socioeconomic status of the city.
Analysis and minimization of sand- cast defects for casting aluminum A356 alloy through Pro CAST simulation
(2024-06) Tibebu Mulatu; Desalegn Wogaso (PhD)
In this research analysis of the existing casting process through scientific tools at the case company, Selam Children Village Tsehayi Roschili Industrial and Agricultural Engineering in Addis Ababa Ethiopia is conducted. Inside foundry shop of case company defect becomes the most series problem, which makes the product to reject due to certain quality and bad surface finish. From different products, pulley product are selected using failure mode analysis and further analysis is conducted on it. In this investigation, various casting process parameters such as mold initial temperature, molten metal flow rate, newly designed model with three different scenario and pouring temperature considered. Then simulation are conducted according to Taguchi L18 orthogonal array. 3D model for the product designed on solid work 2022 and imported to Pro-CAST software for simulation. Different real time parameters given as input and various simulation carried out. From meticulous simulation, it is achieved a remarkable 100 percent void-free casting process. This outcome ensures structural integrity and enhances the reliability of the final components. Hotspot occurrences also reduced from an initial 35 points to an impressive 14 points. This optimization mitigates localized stress concentrations and enhances overall part performance. On further investigation, total volumetric of shrinkage porosity is also successful decreased from 5.67% to 4.77%. This improvement has direct impact on material density and mechanical properties of products. Additionally total defect distance on the ISO surface of product was significantly minimized from 55.62 cm to 25.59 cm. Finally, from selected trial according to Taguchi method and grey relational analysis with Minitab 21.2 software 52.22% total defect minimization is achieved. Depending on the simulation result, selected pulley part fabricated inside foundry shop from aluminum A356 metals. Comparison between previous fabricated products with ought casting simulation software and new product that made after simulation result done and result of sample tested under scanning electron microscope machine presented.
Analysis and Optimization of Passenger Waiting Time: In Case Anbessa City Bus
(Addis Ababa University, 2018) Dobosha, Abbelti; Eshetie, Berhan (PhD)
In public transportation providing the fast transport service is the main concern to satisfy the passenger demand. The bus service accessibility in response to the passenger demand is deferent from route to route. This deference resulted in short passengers waiting time for high frequency and long passengers waiting time for the route of low bus service frequency. The long passengers waiting time is one of the measure of poor public transit service quality. In this thesis mathematical modeling was developed based on the dynamic passengers demand and bus service operational constraint to optimize passengers waiting time at bus terminals of Addis Ababa city in case of Anbessa bus transport using the data collected during literature review, interview, field study and secondary data collected from ACBSE. Mixed Integer Non-Linear Programing MINLP and Mixed Integer Linear Programing MILP model were developed for static and dynamic passenger demand. The dynamic passenger demand was solved as Mixed Integer Linear Programing MILP model by discretizing the bus planning horizon into small time (in minutes) to linearize and make the model tractable to solve it using software. LINGO software was used to solve the model. The result was evaluated with bus headway, bus frequency and bus capacity. The evaluation shows that the overall average bus departure time reduction is 39.62% and 37.74% for DAF or rigid Bishoftu bus and articulated bus respectively. The improved average frequency for DAF or rigid and articulate bus is 62.44% and 60.67% of actual bus frequency. The total average passengers waiting time for the DAF and Bishoftu bus was 8.03% more than the passengers waiting time for articulated bus. The overall average passengers waiting time reduction is 39.62% and 37.74% for DAF or rigid Bishoftu bus and articulated bus respectively, through the proposed mathematical optimization models.
Analysis and Optimization of Process Parameters for Friction Stir Welding of Dissimilar Aluminum 6061 and Commercial Pure Titanium Metal
(Addis Ababa University, 2024-06) Dawit Gebeyehu; Henok Zewdu (Mr.)
Friction stir welding (FSW) is a solid-state weld process were invented in 1991 that broadly used by industries and preferred rather than other weld process due to its capability to weld similar and dissimilar materials under high quality. FSW offers a number of advantages over other weld methods, including being automatic, suitable for most materials, able to be performed in any position, having minimal distortion, and not requiring filler or shielding gas., can be employed under water, and environmentally friendly. In this research, a joint between 6061 aluminium alloy and commercially pure titanium Gr-1 was butt welded by using friction stir welding. at a speed of rotation (1100, 1400, 1600) rpm , a transfer (welding) speed at (50, 60, 80) mm×min-1, a tool pin profile (cylindrical, square, conical), and a dwell time of (5, 10, 15) sec. welded material microstructure and mechanical properties were assessed using the tensile test, the hardness test, and optical microscopy (OM), respectively. Tensile testing, hardness testing, and optical microscopy (OM) were used, respectively; to assess the mechanical characteristics and interfacial microstructure. The numbers of welding experiments were determined using both of the Taguchi and Grey relation analysis approaches. The strength of friction welded dissimilar joints and effect of parameters were analysed using ANOVA (analysis of variance) on Minitab 20 software. After the materials are welded successfully, their tensile strength and hardness were evaluated at room temperature. According to the results, the cylindrical pin profile, 1100-rpm rotational speed, 80 mm/min transverse speed and 15 sec dwell time are the optimal conditions for combining these different joints. In the stir zone, strengthening precipitates were distributed finely and uniformly.
Analysis Effect of Surface Roughness, Material Removal Rate and Tool Life in Turning of Mild Steel Material
(Addis Ababa University, 2017-05) Muluken, Tesfaye; Daniel, Tilahun (PhD)
This Experimental work presents a technique to determine the better productive quality by Analysis of Effect Surface Roughness, Material Removal Rate and Tool Life in Turning of Mild Steel by controlling cutting experiment. Turning Experiments on Laze Machine were conducted with Spindle Speeds: 530, 700, 860 rev/min, Feeds: 0.5, 0.6, 0.7 mm/rev and Depth of cuts: 0.5, 1.0, 1.5 mm. Thus the three input process parameters such as Spindle Speed, Depth of Cut and Feed Rate have been selected to minimize the Surface Roughness, maximize Material Removal Rate and Tool life simultaneously The present work focused by using L9 Orthogonal Array (OA) on the processing steps to get the optimal values with the help of Minitab software using main effects graph, and Analysis of variance (ANOVA) was employed to investigate the characteristics and experimental results are provided the effectiveness of this approach. This technology has met the current needs of Industry owing to its shorter design cycles and improved the design of quality using Taguchi Method. The results revealed that the feed rate (68.7%) is only significant to minimize surface roughness and optimum values are (530rpm, 0.5mm/rev, 0.5mm) secondly spindle speed (48.7%) the major significant parameter for Maximize Material Removal Rate and the Optimum values are (860rpm, 0.7mm/rev, 1.5mm) lastly spindle speed (75.3%) is Highly significant parameter for maximize Tool life and the optimum values are (530rpm, 1mm/rev, 0.5mm), Finally, the relationship between cutting parameters and the performance measures ( Surface Roughness, Material Removal Rate and Tool life) were developed by using multiple regression analysis.
Analysis of Fatigue Crack Propagation and Life Estimation of Pelton Turbine Bucket by Finite Element Method
(Addis Ababa University, 2020-11) Tadele, Libay; Mulugeta, Habtemariam (PhD)
The Pelton turbine bucket is subjected to different loads under the turbine operating conditions of high rotational speed. One of the most catastrophic failures that could occur in a Pelton turbine is the fracture of the bucket, where the hydraulic jet force is at its maximum and applied for various cycles. The continual application of this cyclic load will result in nucleation and then fatigue crack propagation. This failure of Pelton turbine bucket has a great influence on durability of the turbine. The aim of this thesis is to analyze fatigue crack propagation and estimating the life of Pelton turbine bucket. To do this, a governing equation for crack propagation and life estimation was derived and a Pelton turbine bucket was designed. The three-dimensional model of Pelton turbine bucket was modeled by commercial software SOLIDWORKS. The modeled bucket was then imported to ANSYS 19 workbench. Finite Element analysis was done after meshing, boundary conditions and applying load. Then, static stress analysis and fatigue crack propagation of the turbine bucket was investigated using stress intensity factors. The stress-intensity factor was evaluated for each increment of crack depth and it was related with fatigue crack growth rate. The fatigue crack life was then calculated for each crack increment. As the result obtained, analysis of fatigue crack propagation and life estimation of the bucket are discussed. And few recommendations are made for the future study.
Analysis of Fluid Flow and Losses in Regenerative Flow Compressors Using Cfd
(Addis Ababa University, 2008-04) Te fe ri, Kas s a; Edessa, Dribssa (PhD)
Regenerative flow compressors are rotodynamic machines capable of producing high heads at very low flow rates. With comparable tip speed, they can produce heads equivalent to that of several centrifugal stages from a single rotor. They have found many applications for duties requiring high heads at low flow rates but the compression process is usually with very low efficiency which is their major drawback. Even though there are several factors that can be considered to improve the efficiency of these machines in this thesis various models will be developed with different blade and flow channel geometries to investigate their effect on performance. Details of CFD analysis on the models of the compressor, using a commercial software “FLUENT”, will be presented. And based on simulation results of the different models a blade and channel geometry that gives significant improvement on performance will be suggested.
Analysis of Mechanical Properties of Automotive Disc Brake by Finite Element of Method (FEM)
(Addis Ababa University, 2018-06) Oliyadi, Dereje; Daniel, Tilahun (PhD); Muluken, Maseresha (Mr.) Co-Adviser
Excellent control of braking system in automobile is the essential for safety of braking performance. The brake disc is affected by type of friction material of brake pad. The determination of mechanical interaction that happen between brake disc of automobile and brake pads are very important in design consideration of braking system of automobiles. For this investigation, the TOYOTA HIACE minibus taxi of 12 seats that used in Ethiopia City is taken as a sample. While, the problem occurred in this automobile is most of time failure of brake pads when braking is applied, and wear and fade of brake disc is occurred. Due to this kind of problem some time accident is happen; so the cause of this kind of problem happens in brake disc and brake pad of automobiles of TOYOTA HIACE minibus taxi that used in Ethiopian City is the idealization of selection of good performance friction material of brake pad with corresponding brake disc. Further, due to lack of consideration for selecting best friction material of brake pad with environmental friendliness, in the case of TOYOTA HIACE automobiles dust is produced from friction material of brake pad during braking time affect the aquatic life. Thus, the study of mechanical properties of brake disc with interface of brake pad by finite element method with the help of ANSYS software and experimental investigation of friction materials of brake disc used in local City taxi is very important regarding to best braking performance of automobiles and environmental protection. Hence, as result obtain from analysis of finite element method with the help of software and experimental result of laboratory test; for safe environmental protection, reducing (or) free of Copper in brake pad of automobile especially in brake pad of TOYOTA-HIACE minibus 5L. And the use of Al-MMC brake disc with Ceramic brake pad is best for braking performance of automobiles rather than other interface.
Analysis of Stresses in Helical Gears by Finite Element Method
(Addis Ababa University, 2007-10) Alemu, Negash; Tesfaye, Tamrat (phD)
Gears are one of the most critical components in mechanical power transmission systems. The bending and surface strength of the gear tooth are considered to be one of the main contributors for the failure of the gear in a gear set. Thus, analysis of stresses has become popular as an area of research on gears to minimize or to reduce the failures and for optimal design of gears. This thesis investigates the characteristics of an involute helical gear system mainly focused on bending and contact stresses using analytical and finite element analysis. To estimate the bending stress, three-dimensional solid models for different number of teeth are generated by Pro/Engineer that is a powerful and modern solid modeling software and the numerical solution is done by ANSYS, which is a finite element analysis package. The analytical investigation is based on Lewis stress formula. This thesis also considers the study of contact stresses induced between two gears. Present method of calculating gear contact stress uses Hertz's equation. To determine the contact stresses between two mating gears the analysis is carried out on the equivalent contacting cylinders. The results obtained from ANSYS are presented and compared with theoretical values. Face width and helix angle are important geometrical parameters in determining the state of stresses during the design of gears. Thus, in this work a parametric study is conducted by varying the face width and helix angle to study their effect on the bending stress of helical gear.
Analysis of Supply Chain Performance Measurement System in Addis Ababa: The Case of Selected Shoe Factories
(Addis Ababa University, 2017-06) Sentayehu, Wehibe; Mengist, Hailemariam (PhD)
Supply chain performance measure has a vital role in the improvement of the organization’s overall performance. As a result, different measurement factors were employed and performance frameworks have been changed rapidly due to the effect of today’s competitive global market over a period of time. Although Ethiopia’s manufacturing sector has been developing in a way to fit in a global arena, it is still struggling at an infant stage, this show these factories has problem in their supply chain performance which indicates the presence of problems needs further improvement. This happens due to lack of holistic performance measurement approaches employed for their supply chain performance measurement. The overall objective of this study was to investigate the supply chain performance measurement practices of Ethiopian footwear companies using holistic measurement factors in combination of macro processes and decision making level within performance measurement framework. The study was conducted in three shoe manufacturing companies using a predesigned Likert scale type questionaries’ for purchasing, production and marketing department each companies. Hypothesis was also developed and its significance was tested using SPSS. Additionally, AHP model was employed to check for the desirability of the measurement factors using MATLAB. For checking the internal consistency of the items under study, Cronbach’s alpha was employed and it was learnt that the data were reliable. The results in between groups and within groups are compared using analysis of variances ANOVA. The priority given for each measurement factors were also measured using AHP model. Then, the result of the study shows that the majority of the performance measurement factors differ among the three manufacturing companies at a 5% significant level. Similarly, measuring factors which were given more priority or which are more desirable than other factors to be used for measuring supply chain performance in the case shoe companies were also identified. Moreover areas which need further improvement were also identified, As a result, it was devised that shoe factories should have to give due attention for developing green supplier selection policy, safe and advanced working environment, optimal inventory policy, proper waste management, proper management of obsolete raw material, proper operation of information technology and assessing on degree of bottleneck for managing bottlenecks to achieve best performance in their supply chain and to be competitive in global market.
Analysis of Traffic Accident In Addis Ababa: Traffic Simulation
(Addis Ababa University, 2006-06) Samson, Fanueal; CHANDRA (PhD)
This paper discusses the growing problem of road traffic crashes, particularly in Addis Ababa with particular reference to the magnitude, risk factors, interventions and research priorities. The 2004 World Health Report shows that of the 1.2 million people killed in road crash worldwide, 85% are in developing countries. The traffic police reports human error, road environment and vehicle factors as the main causes of road crashes. However, little documentation is available on the broader underlying factors such as deficiencies in the breviaries changes, ineffective road safety legislation and enforcement, systems for data collection and management, and inadequate medical infrastructure for post-injury management. Although a variety of road safety interventions have been successfully applied, little attempt has been made to promote and implement them. Every year, around 300 people are killed on Addis Ababa's roads and 1500 are light and seriously injured [Federal Police Central Bureau]. The governments have launched several campaigns, such as “Think!” and Road Safety Campaign (RSC), to help people become aware of road safety issues and try to reduce road accident. This study tries to analyze the traffic accidents, and develop a computer-based traffic simulation for the route selection. This thesis has two main functions. Firstly, the aim is to provide users with an understanding of the major causes of traffic accidents and present using several Statistical tools. At the second function, it will apply an innovative, hybrid statistical model for route selection based on accident prediction to traffic police office data. The system, if developed to include the whole network in Addis Ababa, will support several target groups, viz. all road users, Traffic Police and the Emergency and Fire Service through to insurance companies, and local government. The ideal system will Analysis of road traffic accidents in Addis Ababa: Traffic simulation iii give people useful suggestions about how to improve road planning and traffic management. In this paper, a survey is done on current prediction models and visualization techniques. A prototype system is developed using these theories. The functions in the prototype system are limited. More data is required to actualize the system on real terms. The study consists of two major parts: the first part gives detail about the road traffic accident, and Ant Based Control Algorithm implemented for road traffic management. The second part, customization of research empirical equations and experiences to our local conditions and simulate/ forecast the future trend and also with the help of software developed, route selection at the pick hours is managed for the specific path in Addis Ababa. In conclusion, the paper highlights the background of the growing problem of road traffic injuries in the city and provides some basis for optimism in tackling it.
Analysis of Wear Resistance of Wheel-Rail Contact Surface Materials: In the Case of Addis Ababa Light Rail Transit
(Addis Ababa University, 2020-01) Teshome, Meku; Daniel, Tilahun (PhD); Muluken, Masresha (Mr.) Co-Advisor
The purpose of this thesis is to study wear resistance of wheel-rail contact materials of Manganese steel and Pearlite steel. The wheel-rail contact is a critical interface in the railway technology and study of failures in most railways may cause due to wear of wheel-rail contact surfaces. Application of this thesis is on railway technology in the specific area of Addis Ababa Light Rail Transit. It is a new railway technology in Ethiopia. So researches on this area are needed to identify the existing problems and to avoid such problems from the start. The method of this thesis is numerical and analytical analysis of wear resistance of Manganese and Pearlite steels. Based on this method wear and wear resistance of wheel-rail contact materials are evaluated. Using the results of wear and wear resistance of Manganese Steel (current material of Addis Ababa Light Rail Transit) is compared with Pearlite Steel (new material). Since, wear volume of Manganese steel and Pearlite is 0.00169 m 3 3 and 0.00141m respectively at maximum load and maximum distance traveled and wear rate value of Manganese steel is 0.00000335 m 3 /m and Pearlite steel is 0.00000205m 3 /m. On the other hand wear resistance value of Manganese steel and Pearlite steel is 3.98e 5 5 3 and 4.88e m/m respectively. And also wear index value of Manganese steel is 1846.43 and 1599.97 for Pearlite steel. Results of this wear analysis shows that there is less amount of wear volume, wear rate and wear index in Pearlite steel than Manganese steel. On the other hand wear resistance of Pearlite steel has higher than Manganese steel. Finally, this thesis verified that Pearlite steel is better in hardness than Manganese steel.
Analysis of Wheel/Rail Contact Geometry and Applied Load Conditions on the Rail Head Surface
(Addis Ababa University, 2012-10) Addisu, Negash; Daniel, Tilahun (PhD)
Now a day the railway transport infrastructure in Ethiopia is the major issues in relation to the development of the country. To strengthen this infrastructure, related researches must be conducted at the beginning of the construction of the sector. This paper which mainly concerned about the analysis of wheel/rail contact is done to predict and minimize failures caused by improper wheel/rail contact. The objective of this research is to determine the optimum wheel/rail contact and to identify the position of contact, which is basic to justify the way of load distribution on the contacting interface. In this paper the analysis of wheel/rail contact is based on the X, Y, and Z coordinate systems. With the help of these coordinates the type and place of contact on the wheel/rail interface and the way of stress distribution on the rail head surface is identified. Throughout the whole wheel/rail contact analysis, the Hertz contact theory assumptions are basically considered. Therefore based on Hertz contact theory and analytical results (mathematical models developed), the type of contact between wheel and rail is identified as point contact. The positions of the contact point is on the center of rail head where the rail lateral surface parameter ��2��=0 and varies across the wheel lateral surface depending on the position and arrangement of the wheelset. During the analysis of wheel/rail contact the parameters considered are axle load, wheel and rail profiles. By using these parameters the maximum pressure applied throughout the contact point is calculated to be 794.9 MPa. From MATLAB (7.6) and ANSYS (13) simulation results the main failure causes due to maximum pressure applied are principal and shear stresses having their own direction of application on the rail head surface under axle load applied. The shape of the contact patch on the rail head surface is elliptical. The shape identified is practically matched with the assumptions taken from Hertz contact theory. However the size of elliptical patch depends on the size of load applied. The stress distribution throughout the area of contact patch and the neighboring surfaces depends also on the size and direction of applied load.
Analytical and Finite Element Analysis of Surface Wear on Disc Brake Rotor
(Addis Ababa University, 2015-04) Shegaw, Hailemariam; Tilahun, Daniel (PhD))
A particular type of dry contact condition, known as disc and pad brake in contact, in which exposed to wear. In this thesis the wear analysis of disc brake is analyzed by using analytical and finite element method during short brake condition. One particular existing disc brake design for a SUV car of model DD6470C is selected for the study. The dimensions, material property and maximum allowable speed and variable applied brake pressure of this car are used as an input both for analytical and finite element method. Analytical analysis of distribution of contact temperature along in radial direction of disc brake caused by applied heat flux is solved by using separation of variable method. Finite element model of disc and pad brake assembly is done using the CATIA software. Finite element simulation for contact pressure and von misses stress using ANSYS workbench for the case of the structural analysis of disc brake is done by applying only brake pressure and angular velocity. But, in the case of thermal-structural analysis the maximum contact temperature value of disc and pad is considered in addition to applied brake pressure. The contact pressure and von misses stress are calculated analytically and ANSYS workbench results are presented in contour plot and numerically. Contact pressure, von misses stress and wear depth are increasing as increasing of both brake pressure and contact temperature of disc in case of thermal-structural analysis. The structural analysis is less effect than that of thermal-structural analysis in all contact pressure, von misses stress and wear. Based upon the analytical and ANSYS workbench analysis, an analytical model of dry sliding wear was developed. A multi-aspect comparison between analytical and ANSYS workbench results were made. A good agreement between analytical and ANSYS workbench results shows that model provided a reliable prediction of the tribological systems of disc-pad contact. The critical point of contact for disc in contact with pad in the case of structural analysis is near to inner and outer radius of disc brake while thermal-structural is at 95.859mm along radial direction from its center. Thus, this study provides effective reference for design and engineering application of brake disc and brake pad. Key words: Analytical analysis, finite element method, contact pressure, wear
Analytical and Numerical Analysis of Adhesive Joints for Vehicle Application
(Addis Ababa University, 2018-12) Sura, Keneni; Ermias, G. Koricho (Assis Prof.); Araya, Abera (Mr.)
Adhesively joining technique becomes very important due to capability like joining dissimilar material, lighter vehicle design, and composite material assembly than mechanical fastening. During combining dissimilar or similar materials together there must be adequate understanding of the behavior of multi-material adhesively bonded joints to ensure efficiency, safety and reliability of such joints. This may include adhesive thickness, bond length, amount of load to be applied, type material to be joined, type adhesive to be used and other factors used in analysis parameters. Using Elastomeric adhesives such as polyurethanes Sikaflex 265 as adhesive and steel, aluminum, glass and composite as adherend, analytical and numerical analysis has been done on single lap joint for elastic limit. In analytical, derivation of analytical equation that describe peel and shear stress profiles along adhesive length which is to be validated by comparing to numerical analysis done by Finite Element commercial package ABAQUS for metals. By varying the parameters used in stress equation derivation the effect they have on strength of joint also shown on failure load determination for steel, glass and aluminum. For all metals the analysis done is valid for elastic Range only. Effect of fiber orientation of glass fiber reinforced polymer (GFRP) composite on the joint also analyzed. Selecting suitable failure criteria then failure load for each combination of joint parameters are done.

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