Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Article Citation - WoS: 11Citation - Scopus: 14Quasi-Static and Dynamic Compression Behaviour of an Fptm Alumina-Reinforced Aluminium Metal Matrix Composite(Springer Verlag, 1998) Güden, Mustafa; Hall, Ian W.An aluminium metal matrix composite reinforced with continuous unidirectional α-alumina fibres has been compression tested at quasi-static and dynamic strain rates. In the transverse direction, the composite showed increasing flow stress (at 5% strain) and maximum stress within the studied strain rates, 10−3−3 × 103 s−1. In the longitudinal direction, the maximum stress of the composite increased similarly with increasing strain rates within the range 10−5−7 × 102 s−1. It is shown that, if brooming of the sample ends can be suppressed, the failure stress of the composite in longitudinal compression increases significantly. Metallographic observations reveal the typical modes of damage initiation in the composite.Article Citation - WoS: 88Citation - Scopus: 92Material Parameters of Quaternary Iii–v Semiconductors for Multilayer Mirrors at 1:55 Μm Wavelength(IOP Publishing Ltd., 1996) Güden, Mustafa; Piprek, JoachimNine quaternary (Al,Ga,In) - (P,As,Sb) semiconductor compounds lattice matched to InP are investigated theoretically. Direct bandgap, refractive index at wavelength, and thermal conductivity are calculated as a function of the composition. These material properties are important, e.g. in distributed Bragg reflectors of vertical-cavity lasers. The alloy systems AlGaAsSb, AlGaPSb and GaInPSb are found to promise better performance of those mirrors than the common InGaAsP system.Article Citation - WoS: 37High Strain-Rate Compression Testing of a Short-Fiber Reinforced Aluminum Composite(Elsevier Ltd., 1997) Güden, Mustafa; Hall, Ian W.Compression behavior of 15–26 Vf% Saffil™ short-fiber reinforced Al-1.17wt.%Cu alloy metal matrix composites has been determined over a strain-rate range of approximately 10−4 to 2×103 s−1. The strain-rate sensitivity of composite samples at 4% strain, tested parallel and normal to the plane of reinforcement, was found to be higher than that of unreinforced alloy in the strain-rate range studied. Quantitative analysis of fiber fragment lengths from samples tested to different strain levels showed that, at small strains, high strain-rate testing induced a relatively shorter fiber fragment length distribution in the composite compared to quasi-static testing. At quasi-static strain rates, the fiber strengthening effect was found to increase with increasing Vf% and was higher in samples tested parallel to the planar random array. The observed anisotropy of the composite at quasi-static strain rates was also observed to continue into the high strain-rate regime. Microscopic observations on composite samples tested quasi-statically and dynamically to a range of strains showed that the major damage process involved during compression testing was fiber breakage followed by the microcracking of the matrix at relatively large strains. Fiber breakage modes were found to be mostly shearing and buckling.Article Citation - WoS: 4Citation - Scopus: 5High Strain Rate Properties of an Sicw/2124-t6 Aluminum Composite at Elevated Temperatures(Elsevier Ltd., 1998) Güden, Mustafa; Hall, Ian W.Metal matrix composites, (MMC’s) provide several important advantages over unreinforced metals and alloys. Among these, higher moduli and yield stresses and enhanced thermo-mechanical properties are normally considered important in structural applications of MMC’s. It is also possible that MMC’s may be exposed to loading conditions involving high strain rates during service, for example, components of a car in collision with another or turbine blades hit by ingestion of foreign objects. In such situations of rapidly increasing loading conditions, the material property response may be considerably different from that which applies during slow loading of normal quasi-static testing and, consequently, dynamic mechanical properties are of increasing interest and importance.Article Citation - WoS: 10High Strain Rate Behavior of a Sic Particulate Reinforced Al2o3 Ceramic Matrix Composite(Elsevier Ltd., 1998) Hall, Ian W.; Güden, MustafaThe high strain rate deformation behavior of composite materials is important for several reasons. First, knowledge of the mechanical properties of composites at high strain rates is needed for designing with these materials in applications where sudden changes in loading rates are likely to occur. Second, knowledge of both the dynamic and quasi-static mechanical responses can be used to establish the constitutive equations which are necessary to increase the confidence limits of these materials, particularly if they are to be used in critical structural applications. Moreover, dynamic studies and the knowledge gained form them are essential for the further development of new material systems for impact applications. In this study, the high strain rate compressive deformation behavior of a ceramic matrix composite (CMC) consisting of SiC particles and an Al{sub 2}O{sub 3} matrix was studied and compared with its quasi-static behavior. Microscopic observations were conducted to investigate the deformation and fracture mechanism of the composite.Article Citation - WoS: 10Electrolysis of Mgcl2 With a Top Inserted Anode and an Mg-Pb Cathode(Springer Verlag, 1994) Güden, Mustafa; Karakaya, İshakHigh energy consumption in the production of magnesium by molten salt electrolysis is mainly due to the recombination of magnesium and chlorine. The large interelectrode distance used, in conventional techniques, to reduce the extent of ‘back reaction’, results in a significant potential drop. A laboratory cell that enables the operation with smaller interelectrode distance and easy separation of electrode products has been used to study electrolytic magnesium production. The cell features a top inserted graphite anode and a Mg-Pb alloy cathode at the bottom. Current efficiency and power consumption were determined at 690° C using a current density of 0.48 A cm−2. Experiments were performed to study the effects of MgCl2 concentration and anode-cathode distance (a.c.d.) on cell operation. Results indicated that an electrolyte containing 20% MgCl2 (equiweight NaCl:KCl and 1 % NaF) with a 3 cm a.c.d. reduced the cell voltage to 3.72 V. This value corresponds to an energy consumption of 11.3 kWh kg−1 including the refining of Mg-Pb alloy produced at the cathode. This cell performance is more energy efficient compared to conventional magnesium cells.Article Citation - WoS: 44Dynamic Properties of Metal Matrix Composites: a Comparative Study(Elsevier Ltd., 1998) Güden, Mustafa; Hall, Ian W.Three distinctly different metal matrix composites have been tested at strain rates from quasi-static to ≈3000 s−1. It was found that the high strain rate response of each composite was determined primarily by (a) the response of the matrix in the absence of any reinforcement and (b) the damage formation and accumulation processes during deformation. High strain rate behavior of the short fiber composite was dominated by the matrix behavior at low strains but by fiber damage at high strains. The behavior of a whisker reinforced composite was dominated by the matrix properties at all strains. Re-loading tests produced increased fracture strains, indicating that adiabatic heating accelerates fracture of composites by permitting the development of local strain instabilities.Article Kapalı Hücreli Alüminyum Köpük Metallerin Üretim Metodları ve Mekanik Özellikleri(TMMOB Metalurji ve Malzeme Mühendisleri Odası, 1999) Elbir, Semih; Yılmaz, Selahattin; Güden, MustafaKapali hücreli alüminyum köpük metallerin üretim metodları, mikroyapisi, mekanik özellikleri ve uygulama alanları özetlenmiştir. Bu malzemelerin en önemli mekanik özelliklerinden birisi basma altında yüksek miktarda enerji emme kapasiteleridir. Fraunhofer Research Center tarafından toz metalurjisi ile üretilen değişik yoğunluktaki alüminyum köpük metallerine basma testleri yapılmıştır. Basma gerilmesi yoğunluğun artmasıyla yükselmiştir. Fakat enerji emme kapasiteleri yoğunluğun artması ile azalmıştır. Köpük metal hücre duvarlarının oksit tabakası ile kaplı olduğu gözlenmiştir.Article Metal Matrisli Kompozitlerin Yüksek Deformasyon Hızlarında Davranışları(TMMOB Metalurji ve Malzeme Mühendisleri Odası, 1999) Güden, Mustafa; Hall, Ian W.Süreksiz katkılarla kuvvetlendirilmiş Alüminyum Metal Matris Kompozit'lere düşük ve yüksek deformasyon hızlarında basma deneyleri uygulanmıştır. Düşük hızlarda (10'3/S) basma deneyleri instron makinasi ile yapılmıştır. Split Hopkinson Pressure Bar teknigi yüksek hızlarda (>100 Is) basma deneylerinde kullanılmıştır.Parçacık, whisker ve kısa fiberlerle kuvvetlendiriimiş farklı matris (alüminyum) alaşımlı kompozitler test edilmiştir. Kuvvetlendiricinin deformasyon hızına bağlı gerilmeye etkilerini araştırmak için kompozitlerin kuvvetlendirilmemiş matris alaşımlarıda benzer deformasyon hızlarında test edilmiştir. Kuvvetlendiricinin boyutu ve dağılımının, matris alaşımı ve uygulanan Isıl işlemin test edilen kompozitlerde deformasyon hızına bağlı gerilmeleri etkilediği bulunmuştur.