Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis The Application of Aliminum Foam for the Heat and Noise Reduction in Automobiles(Izmir Institute of Technology, 2005) Akseli, Ilgaz; Güden, MustafaAn experimental study has been conducted to investigate the effective thermal conductivity and sound absorption coefficient of Al and SiCparticle/Al closed-cell foams.The foams were prepared using the foaming of powder compact processes developed by Fraunhofer CMAM. The foaming of powder compact process has been extended for the foaming of composite compacts containing 10 weight percent of SiC particles. Effective thermal conductivity measurements were performed using the temperature distribution for steady state conduction through a uniform plane wall method. The sound absorption coefficient measurements were conducted using the standing wave ratio method. The effect of hole drilling on the sound absorption coefficient of foams was also investigated. The measured effective thermal conductivities of the foams were also fitted to the previously developed effective thermal conductivity models of metal foams.The effective thermal conductivities of studied Al foams were then expressed as function of percent porosity with the best-fitted model equation. The effective thermal conductivity values of Al foams were also compared with those of Alporas closed and ERG open cell foams produced by the foaming of Al melt and investment casting methods, respectively. The sound absorption coefficients of Al and SiC/Al foams were found relatively low and similar at lower relative densities and frequencies. Hole drilling was found to be effective in increasing sound absorption values of foam above400 Hz. The sound absorption in Al and SiC/Al foams was further explained based on the viscous losses and thermal damping effects.Master Thesis Processing and Mechanical Testing of Ti6a14v Foams for Hard Tissue Implant Applications(Izmir Institute of Technology, 2005) Akar, Egemen; Güden, MustafaSintered Ti6Al4V alloy powder foams were prepared using atomized spherical powders in the porosity range of 52-72 %. For increasing porosity range, space holder was used. Spherical powder foams were cold compacted at (200, 300, 400, 500 MPa) compaction pressures and then sintered at 1200 °C for 2 h and 1300 °C for 2-4-6 h. The final porosities and average pore sizes were determined as functions of the applied compaction pressure and sintered time.The mean pore size of the foams varied between 94 and 148 mm depending on the particle size range of the powders used and the compaction pressure applied.Microscopic studies of sintered powder foams showed that sintering at high temperature (1200°C and 1300°C) and subsequent relatively slow-rate cooling in the furnace transformed the microstructure of spherical powder from the acicular alpha to the Widmansttten microstructure.In compression testing, at quasi-static, the foams failed primarily by shear band formation along the diagonal axis 45 to the loading direction. Microscopic analyses of deformed but not failed and failed spherical powder foam samples further showed that fracture occurred in a ductile (dimpled) mode consisting of void initiation and growth in alpha phase and/or at the alpha/b interface and macrocraking by void coalescence in the interparticle bond region.The strength of the sintered foams was further shown to satisfy the strength requirements for cancellous bone replacement. The strength of the compacts having porosity level of 40% and/or lower was comparable with that of human cortical bone.Compared to Ti powder compacts of previous studies, Ti6Al4V powder compacts provided higher strength and increased porosity level of the foams suitable for cortical bone replacement.