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Öğe ANN prediction of impact toughness of ship steel/ stainless steel plates produced by explosive welding(University of Kuwait, 2020) Kaya, Y.; Kalyon, A.; Kahraman, N.In this study, ship steel/stainless steel plates were produced by joining ship steel with stainless steel using explosive welding process. The characterization of the joining interface of the plates was carried out by optical microscopic examination. Charpy impact tests were conducted at different temperatures to determine the impact toughness of the ship steel/stainless steel plates and the effect of the rolling on the impact toughness. In addition, after the Charpy impact test, the fractured surfaces of the specimens were investigated via scanning electron microscopy (SEM). Using the data obtained as a result of the impact toughness tests, an artificial neural network (ANN) model was improved for the prediction of the impact toughness. Five different material types, two different rolling directions, and eight different temperatures were used as the input parameters of the Charpy impact tests. The impact toughness values obtained at the end of the tests were used as the output parameters of the generated prediction model. The high R2 value obtained in the developed prediction model demonstrated that it could be successfully used for predicting impact toughness. © 2020 University of Kuwait. All rights reserved.Öğe Effect of Continuous and Pulsed Currents on Microstructural Evolution of Stainless Steel Joined by TIG Welding(Carl Hanser Verlag, 2015) Durgutlu, A.; Findik, T.; Gulenc, B.; Cevik, B.; Kaya, Y.; Kahraman, N.In this study, AISI 316L series austenitic stainless steel sheets were joined by tungsten inert gas welding method in continuous and pulsed currents. Regarding microstructural investigation and hardness values of weld metal, samples were welded to investigate the effect of current type on grain structures of weld metal. Results showed that samples welded by using pulsed current had considerable different properties compared to the samples welded by using continuous current. While the weld metals of joinings obtained by using continuous current displayed a coarse-grained and columnar structure, weld metals obtained by using pulsed current had a finer-grained structure. It was also found that hardness values of samples, which were welded with continuous and pulsed current, were quite different.Öğe The effect of modifiable lifestyle factors on semen quality(Ediciones Doyma, S.L., 2020) Kaya, C.; Aykaç, A.; Kaya, Y.; Tas, M.Introduction and objectives: To examine the association between lifestyle factors (body mass index, smoking, alcohol consumption, coffee intake, physical activity, sauna and cell phone usage, wearing tight-fitting underwear), and conventional semen parameters. Materials and methods: 1311 participants who attended the Andrology Clinic were included in the study. All participants were separated into two groups as men with normozoospermia and dysspermia. All participants answered a questionnaire which contains questions about the modifiable lifestyle factors. The total risk scores were calculated after all the positive lifestyle factors had been counted. Results: Men with normozoospermia and dysspermia consisted of 852 (65.0%) and 459 (35.0%) participants respectively. A negative relationship between the wearing of tight underwear and having normal semen parameters was detected between the two groups (p = 0.004). While going to a sauna regularly was negatively related to semen concentration, wearing tight underwear was also related to both lower motility, normal morphology as well as semen concentration (p < 0.05). While the total score of all participants was 5.22 ± 1.34 point, there were no statistical differences between the two groups (p = 0.332). It was found that having 3 more or fewer points was not related to any type of semen parameters and results of a spermiogram. Conclusion: The clinicians should give advice to infertile male patients about changing their risky lifestyle, for infertility, to a healthy lifestyle for fertility. Better designed studies, with larger sample sizes using conventional semen analysis with sperm DNA analysis methods, should be planned to identify the possible effects of lifestyle factors on semen quality. © 2019 Asociación Española de Andrología, Medicina Sexual y ReproductivaÖğe An investigation into the joining of titanium with copper through diffusion welding/bonding(2013) Aydin, K.; Hidiroglu, M.; Kaya, Y.; Kahraman, N.In this study, Ti-6Al-4V and copper were joined through different welding temperatures (825 and 850 °C) and holding time (15, 30 and 60 min) diffusion welding/bonding method under argon shielding. The welded joints were subjected to hardness and shearing tests in order to determine their interfacial strength. In addition, microstructural properties of the joined interface were examined using optical and scanning electron microscope (SEM). EDS graphs and diffusion maps of the interface were obtained by carrying out line and elemental analyses. The shearing tests revealed that increasing welding temperature and holding time increased the shearing strength of joined parts. The hardness tests indicated that hardness values increased with increasing distance from titanium to the interface and decreased with increasing distance from the interface to the copper. EDS analyses showed that different reaction areas took place in the welded parts depending on the temperature and holding time.Öğe An investigation on joinability of the AISI 304 and AISI 430 stainless steel by TIG, MIG and shielded metal arc welding methods(2010) Kaya, Y.In this study, AISI 430 ferritic stainless steel and AISI 304 austenitic stainless steel sheets with 3 mm thickness were joined by Tungsten Inert Gas (TIG), Metal Inert Gas (MIG) and shielded metal arc welding methods. Mechanical properties of the welded samples were investigated in terms of tensile strength, notch impact strength, microhardness and microstructure. The results of the tensile test indicated that fracture occurred at theHAZ of the ferritic stainless steel side in the all samples. The highest tensile strength in welded samples were obtained in the samples joined with TIG welding. According to the notch impact test, impact energy of the samples joined with TIG and MIG is higher than that of the samples joined with shielded metal arc welding. Microhardness test showed that the highest hardness was obtained in the HAZ at the AISI 430 stainless steel for all welding condition used in this work. According to microstructure investigation, it was observed that grain growth occurred in the HAZ of the AISI 430 ferritic stainless steel.Öğe A novel approach to diffusion bonding of copper to stainless steel(Sage Publications Ltd, 2012) Kaya, Y.; Kahraman, N.; Durgutlu, A.; Gulenc, B.In this study, austenitic stainless steel and copper materials were bonded through the diffusion welding method, one of the solid-state welding processes. The welding process was carried out at 875 degrees C temperature for 30 minutes under 3MPa pressure. Two different methods were employed in the welding process. In the first method, the conventional diffusion welding procedure was followed. In the second one, an external electrical current was applied to the parts to be joined with the help of a system that was added to the conventional system. By doing so, the aim was to determine the diffusion amount and length for the specimens obtained with and without current. The weld quality of the diffusion welded specimens was examined using the tensile and hardness test. In addition, microstructural analyses were done using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The highest hardness value was obtained in regions next to the interface and it was decreased gradually as the distance from the interface increased on both sides of the interface. The results indicated that the highest interface strength was obtained for the specimens joined when the external current was applied. According to the EDS and EDS line element analyses results, it can be seen that the specimens joined by applying the external current had a higher amount of diffusion and length than the specimens joined by the conventional technique.Öğe Production of wire reinforced composite materials through explosive welding(Elsevier Urban & Partner Sp Z O O, 2016) Gulenc, B.; Kaya, Y.; Durgutlu, A.; Gulenc, I. T.; Yildirim, M. S.; Kahraman, N.Explosive welding is a solid state welding process, which uses a controlled explosive detonation to force two metals together at high pressure. The process has been fully developed with large-scale applications in the manufacturing industry. The explosive bonding technique has an ability to bond a variety of similar and dissimilar materials, and has been applied to fabricate the clad materials and some composites such as multilayered and wire-reinforced materials. In this study, aluminum plates were explosively welded by placing a steel wire mesh between them in order to produce wire mesh reinforced composite materials. The steel wire meshes were placed at two different orientations (45 degrees and 90 degrees). The wire mesh was used to improve the mechanical properties of the explosively welded aluminum plates. Hardness, tensile strength, toughness, bending and microstructure of the explosively welded composite materials were evaluated. The tensile and toughness tests results showed that the 45 wire mesh reinforced composites exhibited higher strength than unreinforced explosively bonded Al plates. No separation was observed in the interface of the welded composite materials after three-point bending. The highest hardness value was measured for the area near the joining interface. (C) 2015 Politechnika Wroclawska. Published by Elsevier Sp. z o.o. All rights reserved.
