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Öğe A COMPARATIVE STUDY ON THE MECHANICAL AND CORROSION PROPERTIES OF THE ZM20 AND ZM21 ALLOYS AFTER CASTING AND ROLLING(Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2022) Goren, Haul Ahmet; Unal, Mehmet; Turen, Junus; Ahlatci, Hayrettin; Sun, YavuzIn this study, the effects of grain refinement and production methods on the corrosion, corrosive wear and mechanical properties of the as-cast and as-rolled Mg-2 wt.% Zn (ZM20) and Mg-2 wt.% Zn-0,51 wt.% Mn (ZM21) alloys were examined by using OM, XRD, SEM, hardness and uniaxial tensile test. Additionally, the potentiodynamic polarization, immersion corrosion test and corrosive wear properties of the ZM20 and ZM21 alloys were compared. According to the XRD results, MgZn and MgZn2 phases were found in the alloys and also MnZn3 phase occurred in the ZM21 alloy with the addition of manganese. Both during solidification forming nucleation points with the added manganese and during rolling the broken secondary phase particles distributed into the matrix prevented grain growth and led to the formation of a more refined structure. The tensile test results showed that the strength of the as-cast ZM21 alloys were better than that of the as-cast ZM20 alloys and further improvement in mechanical properties occurred with the rolling of the both alloys. The most superior hardness was found in the as-rolled ZM21 alloy. In the total 400-m recipro-cal corrosive wear test in the 3.5% NaCl solution, the lowest mass loss was in the as-rolled ZM21 alloys. In the potentiodynamic corrosion test, the highest corrosion resistance was occurred by the as-cast ZM20 alloy.Öğe Effect of applied load on adhesive wear and corrosive wear behaviours of two aluminium bronze (Cu-Al-Fe) alloys(Sage Publications Ltd, 2025) Metin, Meric; Unal, Mehmet; Goren, Halil AhmetIn this study, the microstructure, adhesive (dry) wear and corrosive wear properties of cast C95200 and C95300 aluminium bronze alloys were investigated. The most important difference for these two alloys is that C95200 alloy contains 8.67% Al and 2.51% Fe while C95300 alloy contains 10.10% Al and 0.93% Fe. Both alloys contain 0.11% Zn and trace amounts of Sn, Ni, Si, Pb. The equilibrium element that completes 100% of these two alloys is Cu. First, 99.9% pure copper was loaded into the graphite crucible of the induction furnace and the temperature was raised to 1155 degrees C. Then 99.9% pure iron filings were added, waited for 30 min and the molten metal was gently stirred with a graphite propeller shaft. At 1140 degrees C, 99.9% pure aluminium was added. A protective flux containing fluoride and chloride was used to cut off contact with the atmosphere. The melted alloys were poured without waiting into a permanent mould heated to 250 degrees C. Microstructure, SEM (Scanning Electron Microscopes), EDS (Energy-dispersive X-ray spectroscopy), XRF (X-ray fluorescence), corrosive wear, adhesive (dry) wear test samples were prepared from the appropriate regions of these alloys. The corrosive wear test was carried out with a back and forth wear system in a salt water environment containing 3.5% by weight NaCl. In the corrosive wear test, at a distance of 1000 m, alloy C95200 lost 381.48% and 152.27% more weight than alloy C95300 under 10 and 20 N load, respectively, but lost 11.98% less weight under 40 N load. When the SEM and EDS results after corrosive wear were examined, it was observed that there were cracked bright parts on the surface of the C95300 alloy. When the Adhesive dry wear results under 10, 20, 40 N loads at 8000 m distance were examined, C95200 alloy lost 5.91% more weight than C95300 under 10 N load but lost 37.25%, 60.03% less weight under 20, 40 N load respectively.Öğe Sağlıklı Kişilerde Lomber Vertebralar (L2-L3-L4) Üzerine Yüksek Hızlı Düşük Amplitüdlü Tekniği ile Yapılan Kayropraktik Manipülasyonun Hamstring ve Kuadriseps Kas Gücü Üzerine Olan Etkisinin Değerlendirilmesi: Deneysel Çalışma(2023) Atesoglu, Zulal; Ozden, Ali Veysel; Altunok, Mehmet Kaan; Hatık, Sefa Haktan; Demir, Fırat; Bildik, Celaleddin; Unal, MehmetAmaç: Bu çalışmada, sağlıklı kişilerde lomber vertebralar (L2-L3-L4) üzerine Yüksek Hızlı Düşük Amplitüdlü [High Velocity Low Amplitude (HVLA)] tekniği ile yapılan kayropraktik manipülasyonun (KM) hamstring ve kuadriseps kas gücü üzerine olan etkisi değerlendirildi. Gereç ve Yöntemler: Gönüllü ve sağlıklı 54 birey, KM ve sham gruplarına ayrıldı. Katılımcıların ölçüm ve testleri 24 saat arayla olmak üzere toplam 2 kez tekrarlandı. KM grubunun L2- L3-L4 vertebralarına kayropraktik HVLA teknikleri uygulanırken, sham grubunda pozisyonlama yapılıp herhangi bir itme manevrası uygulanmamıştır. Her iki grubun da uygulama öncesi ve sonrası; gonyometrik ölçümler ve Schober testi ile lomber bölge eklem hareket açıklığı, izokinetik dinamometre (CSMI Humac- Norm) ile kuadriseps ve hamstring kas kuvveti ölçüldü. Katılımcıların cihazı denemeleri ve anlamaları için test seçeneği aktifleştirilerek iki tekrar ayarlanıp protokol kaydedildi. Bulgular: KM grubunda incelenen bütün değişkenlerde tedavi sonrası tedavi öncesine göre istatistiksel olarak anlamlı artışlar tespit edilirken (p<0,05); kontrol grubunda gövde fleksiyonu ve ekstansiyonu açı değeri, Schober testi, hamstring-sol 60°/sn ve hamstring-sol 240°/sn açısal hızda kas kuvveti hariç anlamlı farklılık görülmedi (p>0,05). KM grubunda düz bacak kaldırma [straight leg raise (SLR)]-sağ, SLR-sol, Schober, kuadriseps-sağ 60°/sn, kuadriseps- sol 60°/sn, kuadriseps-sağ 240°/sn, kuadriseps-sol 240°/sn, hamstring-sağ 60°/sn, hamstring-sağ 240°/sn parametrelerinde, kontrol grubuyla kıyaslandığında tedavi sonrası tedavi öncesine göre anlamlı artış olduğu tespit edildi (p<0,05). Sonuç: Kuadriseps ve hamstring kas kuvveti üzerindeki olumlu etkinin diz eklemini koruyarak olası yaralanmaları önleyebileceği, lomber eklem hareket açıklığındaki artışın ve sağlıklı vertebra diziliminin omurga dejenerasyonunu geciktirebileceği kanısına varılmıştır.Öğe Stability in nonlinear delay Volterra integro-differential systems(Int Scientific Research Publications, 2014) Raffoul, Youssef; Unal, MehmetWe employ Lyapunov functionals to the system of Volterra integro-differential equations of the form x'(t) = Px(t) - integral(t)(t-r) C(t, s)g(x(s))ds, and obtain conditions for the stability of the of the zero solution. In addition, we will furnish an example as an application. (C)2014 All rights reserved.Öğe The effects of Nd, La, and Ca addition on the corrosion properties of as-cast and as-rolled ZM21 Mg alloys(Edp Sciences S A, 2024) Unal, Mehmet; Goren, Halil AhmetIn this study, the effects of Nd, La, and Ca elements added to ZM21 alloy was investigated in terms of parameters such as microscopic, mechanical, and corrosion properties. The content of each of the elemental constituents was 0.5% by weight. The microstructural and mechanical behaviours of the investigated alloys were examined by XRD, EDX, SEM, OM, hardness surveys, tensile tests, and corrosion experiments. According to the XRD results, Ca5Zn3, Ca2Mg6Zn3, LaZn2, LaMg3, Mg41Nd5, and Mg12Nd phases emerged on the investigated alloys. The grain sizes of the alloys were refined by element addition and rolling process, thus increasing their mechanical properties. Ca increased the hardness of the ZM21 alloys, but this had a negative effect on the rolled specimens. The tensile value of ZM21 alloy as cast decreased by 39.702%, 48.080%, 45.678% with the addition of (0.5% La+0.5% Nd), (0.5% La+0.5% Ca), (0.5% La+0.5% Nd+0.5% Ca), respectively. The tensile value of ZM21 alloy with (0.5% La+0.5% Nd) addition increased by 58.302% as rolled. Tensile test could not be performed because the rolled alloys with 0.5% Ca addition were fragmented during rolling. Ca contributed positively to the corrosion behaviour of the casting ZM21 alloy, but it worsened it in the rolled alloys. White oxide areas on the surface of the rolled alloys indicated an increased degree of corrosion formation.
