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Öğe Biomechanical Analysis of C5-C6 Spinal Unit with Prosthetic Disc by Finite Element Method(Polish Acad Sciences Inst Physics, 2019) Ozmen, R.; Gunay, M.; Demir, T.Spinal fusion and total disc arthroplasty are used in the surgical treatment of cervical disc degeneration. When mobility is desired in the functional spinal unit, total disc arthroplasty is preferred instead of fusion. In this research, the effects of artificial disc prosthesis on the biomechanical behaviour of the C5-C6 functional spinal unit were investigated via finite element method. Firstly, three-dimensional CAD models of C5 and C6 vertebrae were created by using a computerized tomography images of a healthy human neck via 3D Slicer computer software. The mobility of the healthy model consisting of intervertebral disc, joints, and soft tissues was validated by previously published experimental studies in the field. On the second step, a ball and socket type artificial disc was defined using connector elements between C5-6 functional spinal unit to simulate the total disc arthroplasty method. Finally, to investigate the effect of prosthesis core radius changes on the biomechanical properties of functional spinal unit, healthy and implanted models were analysed via finite element method.Öğe Effect of zinc supplementation on lipid peroxidation and lactate levels in rats with diabetes induced by streptozotocin and subjected to acute swimming exercise(2012) Bicer, M.; Gunay, M.; Baltaci, A.K.; Uney, K.; Mogulkoc, R.; Akil, M.Objective: The present study aims to explore the effect of zinc supplementation on lipid peroxidation and lactate levels in rats having diabetes induced by streptozotocin and subjected to acute swimming exercise Method: A total of 80 adult male rats of Sprague-Dawley type were equally allocated to 8 groups: Group 1, general control. Group 2, zinc-supplemented group. Group 3, zinc-supplemented, diabetic group. Group 4, swimming control group. Group 5, zinc-supplemented swimming group. Group 6, zinc-supplemented diabetic swimming group. Group 7, diabetic swimming group. Group 8, diabetic group. At the end of the 4-week study, blood samples were collected to determine MDA, GSH, GPx, SOD, lactate and zinc levels. Results: The highest MDA values were found in group 7 and 8 (p<0.001). GSH values in groups 5 and 6 were higher (p<0.001). The highest GPx values were established in groups 2, 5 and 6 (p<0.001). SOD values were the highest in groups 5 and 6 (p<0.001) and lowest in groups 2, 3 and 8 (p<0.001). The highest plasma lactate levels were found in group 7 (p<0.001). The highest zinc levels were obtained in groups 1, 2 and 5 (p<0.001), and the lowest zinc levels were found in groups 7 and 8 (p<0.001). Conclusion: Results of the study reveal that zinc supplementation prevents the increase in free radical formation, suppression of antioxidant activity and muscle exhaustion, all of which result from diabetes and acute exercise. Zinc supplementation may contribute to health and performance in diabetes and acute exercise.Öğe Effects of process parameters on fatigue behavior and surface integrity of tool steel produced by electrical discharge turningAuswirkungen von Prozessparametern auf das Ermudungsverhalten und die Oberflachenintegritat von durch Funkenerosionsdrehen hergestelltem Werkzeugstahl(Wiley-V C H Verlag Gmbh, 2023) Cakiroglu, R.; Gunay, M.Electrical discharge machining is used in the production of countless parts with complex geometries and micro dimensions, from many elements of industrial molds to parts of motors and pumps. Also, most of these parts are cylindrical and it is always more meaningful to study their rotational fatigue behavior to predict their response during their operation. This study concentrated on the impacts of machining parameters on the surface quality and fatigue behavior of tool steel shaped by electrical discharge turning. The results based on Taguchi methodology have shown that discharge current affects R-a and R-z more, and pulse duration more affects the mean spacing of profile irregularities, S-m. As a result of the heat affected depth in the machined region, which changes in proportional with the processing parameters, the microhardness decreased from the sample surface to the core. The maximum hardness was measured at current of 12 A, pulse duration of 3 mu s and pulse interval of 7 mu s. According to the fatigue tests, it was found that the fatigue life decreased with the increase in R-z and S-m values. Moreover, high microhardness and thick recast layer reduced the fatigue strength of the samples with relatively smooth surface topography.Öğe Effects of Severe Plastic Deformation on the Mechanical Properties of Welded ST37-2 Steel(Dr D. Pylarinos, 2020) Sahhal, A.; Gunay, M.Cold treatment techniques are used to enhance the mechanical properties of metal alloys, whose most important characteristics are strength, roughness, and microstructure. The aim of this research is to test the effect of Conventional Shot Peening (CSP) and Severe Shot Peening (SSP) on the mechanical properties of ST37-2 steel. The results of the experiments showed enhancements in surface roughness and tensile strength. However, shot peening decreased the ductility of the metal and caused changes in its microstructure that are indicated in the XRF and XRD tests. Results’ data are provided as an original contribution to the literature while they are compared with the existing data. © 2020, Dr D. Pylarinos. All rights reserved.Öğe Finite element modeling of tool stresses on ceramic tools in hard turning(Kaunas Univ Technol, 2017) Gunay, M.; Korkmaz, M. E.; Yasar, N.Hard turning process has been developed as a possible alternative instead of more expensive cylindrical grinding operations. This process involves many cutting conditions like traditional turning such as machining parameters, nose radius and tool geometry. This study aims that cutting force components (F-f, F-r, F-c) and cutting tool stresses depending on cutting conditions which are cutting speed, depth of cut and feed rate have been investigated in hard turning of DIN 1.2344 tool steel using uncoated ceramic tools. The experiments of hard turning were performed based on full factorial design. The distributions of cutting tools stresses were analyzed based on finite element method by using ANSYS software. ANOVA results showed that the most important factor on all cutting force components is the depth of cut while cutting speed has insignificant effect. In the results of study, it is shown that cutting tool image taken from ANSYS via finite element analysis and tool microscope are very similar. It is possible to say that the boundary conditions for loading of cutting force components are correct and the prediction of cutting tool stresses by finite element analysis can be determined in hard tuning processes.Öğe Mechanical Properties of Powder Metallugry (Ti-6Al-4V) with Hot Isostatic Pressing(Dr D. Pylarinos, 2020) Abdulla, Elfghi, M.; Gunay, M.Titanium alloys are widely used due to their high performance and low density in comparison with iron-based alloys. Their applications extend to aerospace and military in order to utilize their high resistance for corrosion. Understanding the mechanical properties and microstructure of titanium alloys is critical for performance optimization, as well as their implications on strength, plasticity, and fatigue. Ti-6Al-4V is an %+' two-phase alloy and is considered one of the most commonly used titanium alloys for weight reduction and high-performance. To avoid manufacturing defects, such as porosity and composition segregation, Hot Isostatic Pressing (HIP) is used to consolidate alloy powder. The HIP method is also used to facilitate the manufacturing of complex structures that cannot be made with forging and casting. In the current research, Ti-6Al- 4V alloys were manufactured with HIP and the impact on heat treatment under different temperatures and sintering durations on the performance and microstructure of the alloy was studied. The results show changes in mechanical properties and microstructure with the increase of temperature and duration. © 2020, Dr D. Pylarinos. All rights reserved.Öğe Protective effect of melatonin on lipid peroxidation in various tissues of diabetic rats subjected to an acute swimming exercise(Comenius Univ, 2012) Bicer, M.; Akil, M.; Baltaci, A. K.; Mogulkoc, R.; Sivrikaya, A.; Gunay, M.; Akkus, H.Background: The present study aimed to explore the effect of melatonin administration on lipid peroxidation in various tissues of rats with streptozocin induced diabetes and subjected to an acute swimming exercise. Methods: The study used 80 adult male rats, which were equally allocated to 8 groups: Group 1, general control; Group 2, melatonin-administered control; Group 3, melatonin-administered diabetic control; Group 4, swimming control; Group 5, melatonin-administered swimming; Group 6, melatonin-administered diabetic swimming; Group 7, diabetic swimming; Group 8, diabetic control. Diabetic rats were administered 3 mg/kg/day ip melatonin for 4 weeks. At the end of the study, the animals were decapitated to collect samples from liver, lung and spleen tissues, which were then analyzed to determine levels of liver MDA (nmol/gram/protein) and GSH (mg/g/protein). Results: The highest MDA values in liver, lung and spleen tissues were obtained in the Group 7. The values in the Group 8 were lower than those in the Group 7, but higher than in all other groups. The Group 5 and 6 had the highest liver, lung and spleen GSH values. Conclusion: Results obtained from the study indicate that the increase in free radical production and the inhibition of antioxidant activity in diabetes and acute exercise are both prevented by melatonin administration (Tab. 2, Ref. 30). Full Text in PDF www.elis.sk.
