Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Language: search.filters.language.enSubject: search.filters.subject.Aluminum foam

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Now showing 1 - 7 of 7
  • Master Thesis
    Investigation of Compression Mechanical Behaviour of Aluminum Foam Filled Metal Tubes
    (Izmir Institute of Technology, 2004) Kavi, Halit; Güden, Mustafa
    Novel crash element designs, composing of packing of foam-filled multi tubes, were investigated through compression testing at quasi-static deformation rates. Multi-tube designs involved the hexagonal and cubic packing of Al foam-filled deep drawn Al tubes inside rigid cylindrical and rectangular dies. For comparison purposes, empty Al tubes, Al and polystyrene foam-filled single tubes, Al and polystyrene foam-filled bitubular tubes and empty multi-tube designs of hexagonal and cubic packing were also tested under the similar test conditions. The Al-closed cell foams used for the filling of tubes were prepared in house using a patented foaming process. For each tube geometry investigated the average crushing load and specific energy absorption was calculated and the results were compared.It was shown that although foam filling resulted in higher energy absorption than the sum of the energy absorptions of the tube alone and foam alone, it was not more effective in increasing the specific energy than simply thickening the tube walls. The lower specific energy absorptions of the Al-foam filled single tubes based on the equal mass criterion were due to the relatively lower plateau stresses of the filler material used. The experimental results have further shown that both multi-tube and bitubular geometries exhibited higher specific energy absorption capabilities than those of foam-filled single tubes. The increased strengthening coefficients of the multi-tube geometries with foam filling were solely due to the frictional loads between the adjacent tube walls, tube walls and die wall and constraint effect of die itself. The frictional loads were also found to increase the specific energy absorption of empty multi-tube geometries. The effect of Al foam density was found to increase the specific energy absorption in multi-tube geometries.
  • Master Thesis
    Preparation and Characterization of Aluminum Composite Closed-Cell Foams
    (Izmir Institute of Technology, 2001) Elbir, Semih; Güden, Mustafa
    An experimental study has been conducted to investigate the feasibility of the production of SiC-particulate (SiCp) reinforced Al (Aluminum) closed-cell foams using the foaming from powder compacts process and to determine the effect of SiCp addition on the foaming behavior of Al compacts and the mechanical properties of Al foams.The foaming behavior of SiCp/Al composite powder compacts and the compression mechanical behavior of SiCp/Al composite foams were determined and compared with those of pure Al compacts and Al foams prepared by the same processing parameters.Composite and Al powder compacts were prepared by hot uniaxial compaction inside a steel die at 425 oC for 1/2 hour under a constant die pressure of 220 MPa.Compacts of 99 % dense with a small amount of blowing agent of TiH2 (0.5 wt%) were heated above the melting temperature of Al inside a pre-heated furnace. During heating, as the TiH2 decomposed and released hydrogen, the compact expanded uniaxially. Foamed/partially foamed samples were taken from the furnace at the specified furnace holding times and their heights were measured in order to calculate linear expansion.Initial foaming experiments with Al compacts at 750 and 850 oC have shown that foaming at the former temperature was slower and more controllable, although linear expansion was similar at both temperatures. From these experiments, it was also found that rapid cooling of the liquid metal was necessary in order to maintain the liquid foam structure in the solid state.Foaming experiments of SiCp/Al and Al compacts at 750 oC have shown that SiCp addition a) increased linear expansion of the powder compacts and b) reduced the extent of liquid metal drainage. SiCp addition also increased the plateau stress and energy absorption capability of the Al foams. These results have shown the potential of composite foams for tailoring energy absorption of Al foams for varying levels of impact stresses.Foaming experiments have also been conducted on aluminum oxideparticulate/Al and SiC-whisker/Al composites compacts prepared using the same compaction parameters and foamed at the same temperature, 750 oC.
  • Master Thesis
    Crushing Behaviour of Aluminum Foam-Filled Composite Tubes
    (Izmir Institute of Technology, 2005) Yüksel, Sinan; Güden, Mustafa
    An experimental study has been conducted in order to determine the effect of Al-foam filling on the composite and hybrid (Al metal and composite) composite tubes.Tubes and fillers used in the experiments were prepared using the tube rolling and foaming from powder compacts methods, respectively. The composite was prepared using E-glass fiber fabric (2x2 twill fiber construction of 165 g/m2 areal density) and polyester matrix with a 45/45 fiber angle to the tube axis. The quasi-static crush tests were conducted axially on the empty, hybrid and foam filled tubes at 25 mm/min crosshead speed. The deformation sequences of the tubes were further recorded during the tests in order to identify the crushing modes of the tubes. Two failure mechanisms literally known as progressive crushing and catastrophic failure (compression shear) were observed during the crushing of empty composite tubes. The progressive crushing mode leaded to higher crushing loads hence Specific Absorbed Energies (SAE). The predominant progressive crushing mode of empty tubes of thinner wall section was attributed to the surface end defects introduced during sectioning of the tubes. In hybrid tubes, the deformation mode of Al tube was found to be a more complex form of the diamond mode of deformation, leading to higher SAE values than the sum of the SAEs of empty composite and empty metal tube. The increased load and SAE values ofhybrid tubes were attributed to the constraining effect of the composite to the metal tube folding. Results further showed that when the progressive crushing mode was taken into account hybrid tubes had lower SAE values than those of empty composite tubes. The foam filling of the composite tubes however showed two different results. It increased the foam filled tube crush loads over the sum of the crush loads of empty composite tube and foam. In the latter case it was not effective in increasing crush loads over the sum of the crush loads of empty composite tube and foam in the progressive crushing region. These two effects were discussed in terms of possible interactions between composite tube and foam.
  • Master Thesis
    The Application of Aliminum Foam for the Heat and Noise Reduction in Automobiles
    (Izmir Institute of Technology, 2005) Akseli, Ilgaz; Güden, Mustafa
    An 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
    Inertial Effect in Aluminum Metal Foams
    (Izmir Institute of Technology, 2011) Kocatürk, Onur; Güden, Mustafa
    In this study, Al tubes, Al foams of different types, Al sandwich plates of various configurations (orientations) and brittle glass foam samples were quasistatically reloaded in order to assess any micro inertia effect on the deformation stresses. Al foams tested quasi-statically were further reloaded (interrupted test) in Split Hopkinson Bar (SHPB) at dynamic strain rates in order to see effect of strain rate on micro inertia effect. Al empty tubes experienced micro inertia independent (Type I) deformation behavior in lateral compression and micro inertia dependent (Type II) deformation behavior in axial compression. The lack of strain rate sensitivity of the tested Alulight (AlSi10) closed cell Al foams (Al/Si) produced through powder route within the studied strain rate regime was attributed to the foam cell wall fracture during cell wall buckling. While Al foams with and without SiC addition showed micro inertia effect through progressive cell wall bending. In accord with these observations, Al and Al/SiC foams showed the strain rate sensitive, while Alulight foams showed strain rate insensitive plateau stress in the SHPB compression tests. The layer configuration/orientation was shown to affect Al sandwich plate deformation. Progressive bending of the interlayer fins resulted in strain rate depending crushing stress, while shearing of the interlayer resulted in strain rate insensitive deformation stress. As was expected, the strength enhancement was not seen in glass foam specimens tested as the cell walls were fractured under compressive loads. Finally, a simple testing method was shown to investigate micro inertia effect in hollow and cellular Al structures.
  • Master Thesis
    The Projectile Impact Responses of the Composite Faced Aluminum Foam and Corrugated Aluminum Sandwich Structures: a Comparative Study
    (Izmir Institute of Technology, 2011) Odacı, İsmet Kutlay; Güden, Mustafa
    The projectile impact and energy absorption characteristics of the corrugated aluminum cored E-glass/polyester composite sandwich structures were determined at the impact velocities of 150 m/s. For comparison, E-glass/polyester sandwich structures cored with aluminum foam were also investigated. The test conditions were kept the same for each structure in order to identify the impact properties at the similar test conditions. The composite and the foam core composite sandwiches were produced by vacuum assisted resin transfer molding and the mechanical tests were performed on the composite and core samples based on ASTM. High strain rate tests were performed using a compression type Split Hopkinson Pressure Bar and drop weight test set-up. It was found that aluminum foam sandwich structures had higher ballistic limit and energy dissipating performance than corrugated aluminum sandwich structures; however, as the thickness of the face sheets increased the corrugated aluminum cores were observed to be more effective. The results showed that corrugated aluminum structures had the potentials to be used as core material in composite sandwich structures.
  • Master Thesis
    The Effects of Light-Weight Interface Material on the Stress Wave Propagation in the Multilayered Composite Armor System
    (Izmir Institute of Technology, 2011) Tunusoğlu, Gözde; Taşdemirci, Alper
    The main purpose of the current study is to investigate the effect of interlayer material on the ballistic performance of composite armor and stress wave propagation both experimentally and numerically. Three different interlayer materials, EPDM rubber, Teflon and Aluminum metallic foam, were tried. Relatively large pieces of the ceramic around the impact axis in the rubber interlayer configuration were observed while the ceramic layer was efficiently fragmented in Aluminum foam and Teflon interlayer configurations. Accordingly, more significant amount of delamination in composite layer of without interlayer, larger and deeper delamination in EPDM rubber configurations was observed while fewer amounts were observed on Teflon and Aluminum foam configurations .Also, all interlayers caused reduction in the magnitude of the stress transmitted to the composite backing plate, particularly Aluminum foam. However, EPDM rubber did not cause delay in the initial stress build-up in the composite layer, whereas Teflon (~15 ms) and Aluminum foam (~25 ms) caused a significant delay. Also, as ceramic was efficiently fragmented in Teflon and Aluminum metallic foam interlayer configurations, greater amount of projectile kinetic energy was absorbed in this layer, as a consequence, the remaining energy which was transmitted to composite backing plate was decreased. At this point, the effectiveness of Aluminum foam and Teflon were validated with conducting ballistic tests and corresponding numerical simulations and impact chamber tests. After this validation, the ballistic performance of aforementioned materials was compared at equal areal densities. Finally, Aluminum foam was found to be more effective interlayers in reducing the stress values transmitted to the composite backing plate and reduction of the damage imparted to this layer.