DSpace Collection: Thesis - Mechanical Engineering

Effect of Change of Contact Ratio on Contact Fatigue Stress of Spur Gears

Fri, 08 Mar 2013 12:22:29 GMT

Title: Effect of Change of Contact Ratio on Contact Fatigue Stress of Spur Gears

Authors: Michael, G/mariam

Abstract: The present research work dealt on the effect of change of contact ratio on the contact fatigue stresses generated on meshing spur gear teeth during power transmission. In the study different cases of six contact ratio gearing between 1.6 and 2.0 have been analyzed. For the different contact ratios considered the rate of load sharing and angular and radial position of load were determined on the involute profile of meshing tooth of each gearing. In addition to that the different stress conditions of this tooth for critical position (at the instant when the generated contact stress is at the maximum state) are determined. To come up at the result CATIA and Solid Works software involute spur gear models have been applied for stress analysis on ANSYS Workbench (FEM). From this study it is clear that, the higher contact ratio resulted in the higher generated tooth fatigue contact stresses life (i.e. the highest load carrying capacity). This is because of the decrease in value, and the change in location and direction of load applied on tooth involute in mesh to transmit power. At last the results obtained from ANSYS WB are compared with results of the AGMA gear formula results. They are comparable to each other.

BIOGAS PRODUCTION SYSTEM DESIGN FOR CONDOMINIUM AND ITS FEASIBILITY

Tue, 05 Mar 2013 06:20:07 GMT

Title: BIOGAS PRODUCTION SYSTEM DESIGN FOR CONDOMINIUM AND ITS FEASIBILITY

Authors: Bekele, Gaddisa

Abstract: The research is concerned with designing of Biogas Production System for Condominium and studying its Feasibility by crosschecking field survey and information from literatures. The field survey data support the opinion about the importance of constructing biogas plant for Condominium where the average family members’ number is five with average monthly energy cost for cooking is Birr 385 per family. The study indicates that at optimum condition 43.2 m3 day of biogas is obtained from the substrate collected from 10 blocks of Condominium. Based on present energy consumption, 43.2 m3 day biogas fulfills the cooking energy requirement for 43 households. If households use biogas instead of kerosene only, it can serve the cooking energy need for 115 households. Compressing biogas reduces storage requirements, concentrates energy content and increases pressure to the level needed to overcome resistance to gas flow. As the result of installing compressor for this system, 43.2m3 of biogas volume is stored in 7m3 of pressure vessel and the pressure increased to 11bar from 1.106bar. In this study, it was possible to see that the Biogas System Design for Condominium is financially as well as economically feasible as the NPV is positive and benefit cost ratio is greater than one. As financial analysis shows the 40 households will save annually Birr 121,175 or Birr 3,029 per family as a result of using biogas instead of other cooking energy sources & using biogas only instead of kerosene, the 115 households save Birr 1,067 per family per annual. This result is obtained if households construct a 96 m3 biogas plant with daily loading 1.5m3 of night soil in to digester.

Low Carbon Steel Characterization under Quasi-Static Strain Rate for Bumper Beam Application

Thu, 21 Feb 2013 08:49:00 GMT

Title: Low Carbon Steel Characterization under Quasi-Static Strain Rate for Bumper Beam Application

Authors: Dawit, Bogale

Abstract: This paper investigates the mechanical behavior of three selected steel materials which are considered to be the bulk material of front most bumper beam of a vehicle that is suddenly loaded in the quasi-static range. Thirty-six constant strain rate uniaxial tension tests were performed. The test was performed on a HUALONG Electro-hydraulic Universal testing machine at four strain rates The FEM which is ABAQUS/CAE is used to simulate the bumper subsystem using three low carbon steel. The outcome shows that UTS increase with an increase in strain rate and HAS material has the maximum mean UTS. The FEA in the post - processing stage gives the minimum displacement and maximum strain energy for HAS material when compared to the other two materials. Finally from both experimental and ABAQUS explicit analysis the result shows HAS material is better suit for the bumper beam application.

Feasibility Study and Performance Evaluation (Simulation) of Solar Drye Hand Tools Share Company Moulding Sand Drying Mechanism.

Wed, 06 Feb 2013 06:22:31 GMT

Title: Feasibility Study and Performance Evaluation (Simulation) of Solar Drye Hand Tools Share Company Moulding Sand Drying Mechanism.

Authors: Aschenaki, Tadesse

Abstract: Silica sand is sand that is used for molding processes. When a catalyst is added to it, it develops the bonding characteristics of the raisin, which binds the silica sand together. Its moisture content (17.24% initial and 0.5% final moisture content) is extremely critical sand additive that can be greatly impact casting quality. In this study flat plate solar collector was used because, it is the most important type of solar collector and it is simple in design, has no moving parts and requires little maintenance. The analysis of heat transfer coefficient (losses) through flat plate collector was discussed and the techniques that used to reduce these losses also mentioned (by using insulation). Mathematical modeling of solar dryer and drying chamber was described. This paper presents designs and performance evaluation of solar dryer for silica sand with its cost estimation. In the dryer, the heated air from a separate solar collector is passed through a tray, and at the same time, vertical blackened wall of the drying chamber, which is exposed to solar radiation. The results obtained during the test period revealed that the temperatures, moisture removed, drying rate and drying efficiency through dying chamber were decreasing during its upraise path. Initial cost of model solar dryer was estimated (2805 ETB). The number of dryer required is eleven so the total cost is equal to 30855ETB.