Yazar "Aydin, Hakan" seçeneğine göre listele

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    A parametric study on weld zone shape of resistance spot welded 22MnB5 steel
    (Taylor & Francis Ltd, 2023) Tuncel, Oguz; Aydin, Hakan; Gonul, Alisan
    The resistance spot welding of 22MnB5 with different weld currents, weld times, and quenching conditions is investigated in the current study. A Kriging Response Surface Methodology-based local sensitivity analysis is performed to investigate the effect of weld current, weld time, and quench condition on weld zone morphology and tensile shear load (TSL). When welding current, welding time, and quenching conditions are varied between the minimum and maximum values, the geometry of the weld zone was influenced by 40-60%, 20-40%, and 0-20%, respectively, according to sensitivity studies. It is also found that increasing values of welding current are the most effective welding parameter, increasing TSL by about 45%. In order to better understand the TSL variation at different welding parameters, various hardness measurements are applied for each specimen in the fusion zone and the heat-affected zone (HAZ) regions of the weld zone. Based on the location, the HAZ was divided into three regions: the inner, middle, and outer. The middle HAZ had hardness values 12% higher than the base material, while the outer HAZ had hardness values up to 36% lower than the base material. Also, macro-and microstructure images of the sample produced by combining the quenched and non-quenched materials are obtained to demonstrate how the hardness zones are identified.
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    Detection and Molecular Characterization of Kobuviruses: An Agent of Canine Viral Diarrhea
    (Springer, 2024) Timurkan, Mehmet Ozkan; Aydin, Hakan; Polat, Erdal
    Clarifying the etiology of diarrhea cases of unknown cause is important in the fight against enteric infections. In this study, we aimed to investigate the role of canine kobuvirus (CaKoV), in cases of diarrhea of unknown origin in dogs. A total 121 swab samples from dogs with diarrhea were collected. Molecular analyses of the samples were performed. For this purpose, after the sequence reaction, a phylogenetic tree was created, and bioinformatics analyses were performed. The prevalence rate of CaKoV in the sampled population was determined as 16.5% (20/121). The presence of parvovirus and coronavirus, which are common viral agents in CaKoV-positive dogs, was determined as 35% (7/20) and 10% (2/20), respectively. The rate of dogs with only CaKoV detected was 65% (13/20). Phylogenetic analysis of CaKoV strains clustered together closely related to reference strains. There are very limited studies on the role of CaKoV in the etiology of diarrhea cases of unknown cause in dogs around the world. So far, only one study has been done on CaKoV in Turkey. In this report which includes molecular characterization and epidemiological data on CaKoV determined the importance of CaKoV in cases of diarrhea of unknown origin. More comprehensive studies are needed to better understand the pathogenesis, epidemiology, and biology of CaKoV and to determine effective strategies to combat it.
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    Effect of heat input on HAZ softening in fiber laser welding of 22MnB5 steel
    (Elsevier Sci Ltd, 2023) Tuncel, Oguz; Aydin, Hakan; Davut, Kemal
    This study investigates the effects of heat input on the heat-affected zone (HAZ) softening in fiber laser welding of quenched 1.1 mm thick 22MnB5 steel. Laser power (1500-2500 W) and welding speed (40-120 mm/s) parameters are considered as the input process variables. Depending on the input parameters, the applied heat input varied between 12.5 and 62.5 J/mm. The results indicate that a minimum heat input of 50 J/mm is required for full weld penetration. Microhardness findings revealed that the drop in hardness in the HAZ region relative to the base material (BM) reached 39% due to grain coarsening caused by an increase in heat input under the welding conditions. Grain coarsening (prior austenite grains) is also detected in SEM analysis. In addition, grain coarsening at high heat input was also determined quantitatively in EBSD analyses. The proportion of 8.91 mu m grain size in the sample with high heat input is 4.2%, while it is 1.2% in the sample with low heat input. When the heat input increased from 12.5 to 62.5 J/mm, the width of the softened zone with the lowest hardnesses in the HAZ grew from 0.2 mm to 2.2 mm.
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    Effect of rotational speed and dwell time on mechanical properties of dissimilar AA1050-AA3105 friction stir spot welded joints
    (Carl Hanser Verlag, 2014) Aydin, Hakan; Tuncel, Oguz; Yuce, Celalettin; Tutar, Mumin; Yavuz, Nurettin; Bayram, Ali
    Friction stir spot welding is a newly developed joining technology which is expected to be used in the automotive industry for joining body parts made of aluminum sheets. The effect of the rotational speed and dwell time on the mechanical properties of dissimilar friction stir spot welded aluminum sheet alloys was investigated in this study. In the experimental studies, macro-structural characterization, micro-hardness tests and tensile shear tests were conducted. The experimental results showed that the tensile shear load and tensile deformation of the friction stir spot welded joints decreased roughly by 20 % and 25 %, respectively, when the rotational speed increased from 1000 rpm to 2000 rpm. On the other hand, when the dwell time increased from 3 s to 11 s, the tensile shear load increased roughly by 7 %, while the tensile deformation decreased roughly by 19 %, respectively. © Carl Hanser Verlag GmbH & Co.
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    Effect of tool pin profile on the hook geometry and mechanical properties of a friction stir spot welded AA6082-T6 aluminum alloy
    (Canadian Science Publishing, 2021) Aydin, Hakan; Tuncel, Oguz; Tutar, Mumin; Bayram, Ali
    AA6082-T6 alloy was joined by friction stir spot welding using five different pin profiles, namely cylindrical, conical, triangular, hexagonal, and cylindrical with two grooves, at different dwell time. The joints welded by cylindrical pins had larger effective weld width. However, grooves on the cylindrical pin decreased the effective weld width. In the weld made with the hexagonal pin, the hook was bent downward from the interface of the sheets and had the smallest effective weld width. When the conical pin was used, the effective weld width increased with increasing dwell time. In the case of using tools with cylindrical and conical pins, HAZ hardness was relatively lower. With increasing dwell time, HAZ hardness of the joints made with the conical pin decreased. Effective weld width determined the weld strength under the tensile shear loading condition: larger effective weld width resulted in higher weld strength. Weld strength of the joints made with cylindrical pins was higher. The joints fabricated with hexagonal pins had the lowest weld strength. In general, higher dwell time led to higher weld strength. The welds with the higher strength experienced both brittle and ductile fractures, while the joints with the lower strength exhibited completely brittle fracture.
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    Investigation of the effects of welding parameters on mechanical properties and microstructure of triple joined FEP05/DP600/FEP05 steel sheets joined by electrical resistance spot welding
    (Gazi Univ, Fac Engineering Architecture, 2024) Selova, Levent; Tuncel, Oguz; Cavusoglu, Oktay; Dindar, Cigdem; Aydin, Hakan
    Nowadays, resistance spot welding of two or triple joints and of similar or dissimilar sheet metals is widely used in the automotive industry. In the a-, b-, and c-pillars of car bodies, dual-phase (DP) 600 steels and FEP05 steels are commonly welded together. This study investigated the impact of resistance spot welding process parameters such as welding current, welding time, and electrode force on the tensile shear load, elongation, nugget diameter, and indentation depth of triple welded sheet joints (FEP05 + DP600 + FEP05). To determine the mechanical properties of the welded joint, tensile tests and micro-hardness measurements were performed. Microstructural characterization was also used to analyze the weld quality. Additionally, it was demonstrated that welding time, welding current, and electrode force are important factors in triple welded joints. As a result, it has been seen that FEP05 + DP600 + FEP05 sheets can be successfully combined with triple electrical resistance spot welding by choosing the welding parameters appropriately. A shows the relationship of the welding current with the indentation depth and the nugget diameter.