Manufacturing Engineering

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http://etd.aau.edu.et/handle/123456789/217

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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.
Analytical and Numerical Modelling of Failure in Aluminum Matrix Composite for Connecting Rod Application
(Addis Ababa University, 2022-06) Ephrem Yemane; Desalegn Wogaso (PhD)
The failures in composites are due to failure in their matrix, re-enforcement parts, or both. Failure in the composite structure could cause pin failure, stress failure, fatigue failure, hydro lock as well as overheating of the connecting rod. Thus, the implementation of analysis and predicting tools is preferred to prevent failures. The objective of this thesis work is to predict and analyze the failure possibilities in automobile connecting rods. The connecting rods are made of an aluminum matrix with silicon carbide reinforcements which were modeled by varying the volume fraction of re-enforcements in the form of laminates and particulates. The laminate reinforced aluminum matrix composites were modeled by varying laminate orientation while the particulate reinforced ones were modeled by varying the composite aspect ratio. The connecting rod models passed through available failure criteria like Tsai-Hill or Tsai-Wu and Von-Mises stress values. Both models were analyzed using ABAQUS software. Additionally, the particulate reinforced composites were analyzed using representative volume element /RVE/ on DIGIMAT software. The results showed that the material properties of AA6061-SiC composites increased with an increasing reinforcement volume fraction by the reduction in thickness of the bulky connecting rod. Failure in the connecting rod was predicted to occur in stress-concentrated areas located at corners where the SiC reinforcements are found, as well as, areas of load application and the middle cross-section of the connecting rod. The particulate reinforced models were preferred than the laminate reinforced ones because they sustained higher load gradients prone to less failure. The aluminum MMC’S with a five percent SiC reinforcement volume fraction in particulate form, as well as, twenty percent volume fraction SiC in laminate form with 0o or 90o orientation were found suitable for automobile connecting rod application based on the parameters provided by the author.
Assessment, Evaluation and Enhancement of Operational Performance of Metal Fabrication Factory for Cargo Body, Van Body and Trailer Fabrication Through Lean Practice (A Case of KAKI PLC)
(Addis Ababa University, 2024-06) Lewutie Edmealem; Desalegn Wogaso (PhD)
This study aims at investigating on assessment, evaluation and enhancement of the operational performance of metal fabrication factory for cargo body, van body and trailer fabrication by using lean practice at case company of Kaki PLC which is located at Addis Ababa around Sebeta (alemgena). The factory has a huge capacity but has a low operational performance and a large waste. The assessment and evaluation are performed on selected three major product types of the case company based on their demand volume and product nature. Using value stream mapping assessment of the current fabrication process of each product and identify the major waste of the company which are waiting time, defect, unnecessary movement and inventory and large setup time. During the investigation the data are collected by direct observation and using stop watch and the company document is also referred. Then by using cause and effect diagram, further analysis is conducted to identify the root causes for the bottlenecks which is found the poor layout of the factory. The research work is proceeded to develop the solution standing from the assessment and evaluation result. The developed solution is designing new product lay out for three product mix namely NPR van, FSR cargo and trailer by using systematic layout planning, future value stream mapping as a model. In addition to product layout applying an oven in painting process and using simple press machine is the axle preparation in trailer fabrication process. Finally, the solution bring a significant operational performance improvement of the fabrication process of each product mix. The process efficiency of NPR van is improved by 25.4%, the process efficiency of FSR cargo improved by 31.9% and the process efficiency of trailer if improved by 32.42%. To conclude this research work is conducted the assessment and evaluation process by using value stream mapping and cause and effect diagram and also using questioner. Then design new product layout for the factory using systematic layout planning. That will bring a valuable operational performance improvement.
Design, Analysis, and Performance evaluation of Cellular Manufacturing System for Conventional Manufacturing Factory : A case of Addis Machine Spare Parts Manufacturing Industry
(Addis Ababa University, 2023-10) Paulos Girma; Desalegn Wogaso (PhD)
This thesis assessed the performance problems at the Addis Machine Spare Part Conventional Manufacturing Factory (ASPCMF) under the Ethio Engineering Group (EEG). The case factory has been faced a number of manufacturing system challneges according to the data collected from the operations department of the factory. After the analysis performed based on the existing layout evaluation, problems identified were higher idle time of machines and longer travel distances of parts that lead to lower performance. From the study of the previous performance survey done in 2021, the overall performance recorded was 38.03%. After analyzed the existing layout performance using FlexSim software 31.8% performance recorded. This lower performance identified necessitates the requirement to design a new layout and analyzed the performance based on machine utilization and travel distance of parts. Therefore, the purpose to assess the existing manufacturing system based on machine utilization and travel distance of parts led to design, analysis, and evaluate the performance by proposing a cellular manufacturing system. In the design work a 22 part family was created using the Optiz coding system, which was based on hybrid coding system. A method of machine grouping in an incident matrix was developed to form 20 cells. The rank Order clustering algorithm was used to cluster parts and machines within the cell. This minimized 45 duplicated machines in bottlenecks, while increasing the machine utilization of 43 machines in the cluster formed. The designed cell in the cluster was evaluated through grouping efficacy (GE) of parts allotted in cells to achieve optimal effectiveness in cell utilization which was 91% cell efficiency. The CRAFT algorithm used to identify the part flow within the department and the effectiveness of machine arrangement analyzed based on part travel distance that was reduced into 1,425 m from the existing layout 2,236.10 m which increased floor space available so that, an improved layout was proposed. The analysis was performed to evaluate the designed cell, the performance simulation shows that 88.37% of the proposed cellular layout demonstrates significant enhancemenent compared to the existing layout, which was only 31.8 %. The performance simulation was conducted using FlexSim software. Finally,the individual machine utilization percentage was determined and compared between the proposed layout and the existing layout.
Development and Characterization of Hybrid Flax -Banana Fiber Reinforced Epoxy Composite for Ceiling Fan Blade Application
(Addis Ababa University, 2023) Zodiac Simeneh; Desalegn Wogaso (PhD)
A fan blade is the major component of fans, it used for ventilation systems, cooling systems, refrigeration, boilers, and dust collection purposes. The materials used to fabricate ceiling fan blades are fabricated steel, cast or forged aluminum, plastic, fiberglass, or other exotic materials. The present work aims to develop and characterize the mechanical and water absorption properties of hybrid flax-banana fiber reinforced epoxy composite. In addition it examined the suitability of the composite material for ceiling fan blade application. The composite manufacturing process includes fibers extraction, fibers surface treatment, fibers property test, composite plate’s fabrication, composite specimen's mechanical and water absorption tests. Based on the experimental test result, the static structural analysis is performed to analyze the induced stress and deformation on the ceiling fan propellers. The fibers are extracted through water retting and manual extraction methods. The flax and banana fibers are treated with 5% and 3% of NaOH solution to increase the interfacial bonding between the fiber and matrix materials. The fibers are hybridized manually with 1:1, 3:1, and 1:3 fibers ratio. The composite plates are fabricated with eleven sub- composition of 60/40%, 70/30%, and 80/20% resin to fiber volume fraction. The tensile, flexural, impact, and water absorption property tests are conducted using ASTM D3039, ASTM D790, ASTM D6110, and ASTM D570-99 standards. The ceiling fan blade geometry and static structural analysis performed using Catia.V5 and Ansy’s 19.2 software. Overall, the experimental test results shows that 70/15/15% volume fraction exhibits the highest tensile strength of 68.9MPa and flexural strength of 169.14 MPa respectively. The highest impact strength result was observed on 60/20/20%volume fraction. The highest water penetration resistance was observed on 80/15/5%. Overall, the experimental test results shows 70/15/15% volume fraction has the highest tensile strength of 68.9MPa and flexural strength of 169.14 MPa. On the other hand, the highest impact strength result 10.83J is observed on 60/20/20%. In a water absorption test result, the least water absorption property is obtained on 80/15/5%. In addition, 70/15/15% has presented the second lowest water absorption property. Based on the structural analysis, HFBFREC exhibited the lower Von-misses stress of 2.4MPa and 0.9mm deformation.
Fabrication & Characterization of Hybrid Glass -Maize Stalk Fibers Reinforced Epoxy Composite for Bone Fracture Plate Application: An Experimental and Numerical Approach
(Addis Ababa University, 2024-06) Abeba Gachen; Desalegn Wogaso (PhD)
Femur bone fractures are a common injury resulting from high-energy trauma caused by traffic accidents and falls from heights. The conventional use of bone fixation plates presents a challenge due to their stiffness mismatch compared to human cortical bone, leading to the stress shielding effect. To address this issue, a hybrid fiber-based polymer composite with mechanical properties closest to human bone can be used. This research aims to fabricate and characterize the mechanical and physical properties of a new glass-maize stalk fiber reinforced epoxy hybrid composite for femur bone fracture plates applications. The hand-layup technique, coupled with light compression molding, was employed to create a composite material using 3 mm fiber lengths and a fiber-to-matrix weight ratio of 30% and 70%, respectively. Various mechanical and physical tests were carried out on specimens prepared in accordance with ASTM standards to assess the performance of the composite. The composite with a composition of 25% glass fiber with 5% maize-stalk fiber reinforced epoxy showed the promising results for femur bone plate application, with a tensile strength of 166.64MPa, compressive strength of 265.08MPa, flexural strength of 275.64MPa, impact strength of 16.67J, and micro hardness of 42.57HV. The physical properties including water absorption and density are determined for the selected composite and found to be a water absorption of 1.93% and density of 1.4235g/cm3 and these properties make the hybrid composite suitable for the intended application. Finite element analysis is carried out to validate the experimental findings using ANSYS 2021 R2 commercial software. The stress shielding effect has been reduced by using the hybrid composite, with a von Mises stress of 49.166MPa and total deformation of 4.4329mm. The results obtained from both experiments and FEA show that the glass fiber-maize stalk reinforced epoxy hybrid composite is a suitable alternative for bone plates, as it reduces the stress shielding effect associated with the use of metallic plates. Furthermore, the use of agricultural residue like maize stalk as a reinforcing material contributes to environmental sustainability.
Fabrication And Evaluation of Mechanical Properties of The Hybrid Coffee Husk and Enset Fiber-Epoxy Reinforced Composites
(Addis Ababa University, 2023-06) Shambel Dibaba; Desalegn Wogaso (PhD)
in modern times there is a growing concern about replacing polluting and not recyclable synthetic fibers, as well as rare wooden fibers, with sustainable lignocellulose fibers derived from agricultural leftovers for reinforcement bio-composites. Currently in Ethiopia, the accident rate of vehicles on the road is increasing. Along with that, Vehicle security is a significant topic of study to safeguard. not only structures but also occupants in the event of a crash. In the other side the fast increase of population and development of cities required demand for transport, hence to full fill the demand recently the vehicles are imported in large amounts at the same time which requires accessory’s for replacement of their parts, so the front bumper of those vehicle is the most parts demanded due to it is the most exposed part during crash. The Enset fiber and coffee husk were collected from Ethiopia's Southern Nations, Nationalities, and People's Region (SNNPR) Gedeo zone, Yirgachefe district. Sun-dried Eset and coffee husk were treated with a 5% sodium hydroxide mixture to remove more cellulose, hemicellulose, lignin, and additional fiber chunks to increase binding and facial shear strength. Following that, Enset-coffee husk fibers reinforced hybrid composite was created utilizing a hand layup method on the 40-60%, 30-70%, and 20-80% fiber weight percentages of matrix weight to total fiber volume. Tensile, compressive, its impact, flexural, and absorbance of water tests were then performed to determine which constituent of the composite had higher strength under load. While the mechanical and physical properties of the composites were assessed, the composite C5 with E20%-CH10%-E70% possessed the best mechanical and physical properties, with a tensile strength of 43.30MPa, flexural strength of 93.38 MPa, compression strength of 21.23MPa, impact energy of 3.5J, and water absorption percentage of 3.55%. In addition, the front bumpers was modeled in ANSYS 19.2 and composite C5, yielding an optimal von missed stress of 39.119MPa and distortion of 15.09mm. According to the findings and analyses, the chosen Enset-Coffee husk-Epoxy hybrid composite might be explored subsequently as a low-speed crash replacement material for the front bumper.
Fabrication, Characterization and Simulation of Flax-Sisal Fiber Reinforced Epoxy Hybrid Composite for Prosthetic Socket
(Addis Ababa University, 2021-07) Luna Geo; Desalegn Wogaso (PhD)
Prosthetic limb socket is the major part of a prosthetic leg and arm. It provides comfortable connection, transfers the load, ensures stability between the residual limb and the device. This study aims to investigate tensile, flexural, compression, impact and water absorption properties of Flax-Sisal Fiber Reinforced Epoxy Hybrid Composite. The research also targets to explore its application for prosthetic socket. Hand-layup method was utilized to fabricate thirteen composite specimens having 30mm fiber length and fiber-matrix volume percentages of 40-60, 30-70, and 35-65 according to ASTM standards. Eight composite specimens were treated with 5% NaOH. Comparing the thirteen composites, the result showed the treated composite with F25%-S15%-E60% had superior mechanical and physical properties with tensile strength of 68.40MPa, flexural strength of 145.7MPa, compression strength of 45.64MPa, impact energy of 10.83J and water absorption percentage of 3.66%. In addition, using ANSYS 2020, Prosthetic socket was modeled and loading conditions were applied on composition F25%-S15%-E60% from this, maximum von missed stress of 2.214MPa and deformation of 0.0064mm was obtained. Based on the results and analysis, the selected Flax-Sisal-Epoxy hybrid composite has the potential to be further developed as an alternative material of prosthetic socket.
Investigation of Properties of Hybrid Glass-Sisal Fibers Reinforced Polyester with Al2O3 Filler Composite for Wind Turbine Applications
(Addis Ababa University, 2024-06) Azeb Teklemariam; Desalegn Wogaso (PhD)
The purpose of this study is to examine and characterization of the mechanical and physical characteristics of glass reinforced with sisal fiber that has been filled with Al2O3. Due to their exceptional performance and customized qualities, fiber reinforced materials are extensively utilized in a wide range of engineering applications. These days, particular fillers and additives are added to composite materials to lower material prices, increase and adjust the composites' quality to some extent, and in certain situations, improve the product's performance and capacity to be processed. The creation, characterization, and examination of the mechanical and physical characteristics of a polyester hybrid composite reinforced with glass-sisal fibers and Al2O3 is the goal of this research. It also aims to evaluate the hybrid composite suitability for wind turbine blade material applications. In the present work Aluminum Oxide (Al2O3) with different weight fractions (0, 2, 4, 6, 8 and 10wt %) were studied .The HFRC samples are prepared using the hand lay-up method followed by light compression loading. The experimental results shows that the addition of Al2O3 improved the mechanical properties of the HFRC, with the optimal composition being 6% Al2O3, 22% glass fiber, 12% sisal fiber, and 60% polyester. This composition showed the highest tensile strength (93.66 MPa), flexural strength (176.29 MPa), and impact strength (22.17 kJ/m²). It also had the lowest water absorption (3.26%) and density (1.22 g/cm³).The experimental results were also analyzed using ANSYS software. The ANSYS analysis showed that the optimal HFRC composition could withstand the static loads that wind turbine blades are subjected to. Based on the experimental and ANSYS results, the HFRC with 6% Al2O3, 22% glass fiber, 12% sisal fiber, and 60% polyester has the potential to be used as an alternative material for wind turbine blades material.
Optimization of Machining Parameters in Drilling Hybrid Sisal – Cotton Fiber Reinforced Polyester Composite
(Addis Ababa University, 2021-07) Nurhusien Hassen; Desalegn Wogaso (PhD)
As compared to metals, composite materials machining is a challenge because the cutting tool needs to move through the matrix and fiber alternately, which have various properties. The objective of this work is to optimize the machining parameters in drilling hybrid sisal-cotton fiber reinforced polyester composite (HSCFRPC) to reduce the hole roundness error and surface roughness using Taguchi's method. The influence of machining parameters such as spindle speed, drill diameter, and feed rate on the surface roughness and roundness error of HSCFRPC during the drilling process on the vertical CNC milling machine have been analyzed using the methods of Taguchi’s design of experiment. A series of experiments based on 𝐿16 orthogonal arrays were established with different feed rates (10, 15, 20, 25 mm/min), spindle speeds (600, 900, 1200, 1600rpm), and drill diameter (6, 7, 8, 10mm). The measurement of roundness error and surface roughness have been carried out using ABC digital caliper and Zeta 20 profilometer respectively. The experimental values are gathered and analyzed using the MINITAB 19 commercial software program. To create a connection between the chosen drilling parameters and the quality attributes of the drilled holes, linear regression equations have been established. Signal to noise (S/N) ratio analysis and analysis of variance (ANOVA) were performed to identify the rank, percentage contribution and optimum values of these machining parameters such as spindle speed, drill diameter, and feed rate to reduce the roundness error and surface roughness. Based on the analysis the best combination of the optimum machining parameter values (1600rpm, 25 mm/min, and 6mm) are selected to reduce both roundness error and surface roughness of the composite. Finally, verification of the recommended machining parameters have been achieved and the values of roundness error and surface roughness obtained are 0.1mm and 64.8μm Ra respectively, which satisfies the objective of lowest roundness error and surface roughness. The verification result shows that the recommended machining parameter values to reduce roundness error and surface roughness based on Taguchi’s analysis were precise and fitted to the optimum values.

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