Yazar "Kocyigit, Fatih" seçeneğine göre listele

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    A comparative study on the high temperature dry sliding wear behavior of TiN and AlTiN/TiSiN coatings fabricated by PVD technique
    (Emerald Group Publishing Ltd, 2019) Altas, Emre; Erdogan, Azmi; Kocyigit, Fatih
    Purpose This study aims to investigate the high-temperature wear behavior of the TiN- and AlTiN/TiSiN-coated WC materials. Design/methodology/approach The coating process was carried out using the physical vapor deposition (PVD) method. Wear tests were performed by a ball-on-disc wear device with a high-temperature wear module. In microstructural investigation of the materials, it was benefited from traditional characterization methods such as, SEM, EDX analysis and microhardness measurement. Findings The best wear performance was obtained with AlTiN/TiSiN-coated WC materials at all loads and temperatures, followed by TiN-coated and uncoated WC samples. An important wear was not observed on the samples tested at room temperature tests. It was found that the temperature increase is an effective parameter on the decrease of the wear resistance of the samples. In addition, it was seen that the increasing load and temperature change the wear mechanism on the uncoated WC sample. The wear mechanisms observed at high temperatures were delamination and oxidation for the WC, fatigue for AlTiN/TiSiN-coated WC and micro-scratch and micro-spalling for TiN-coated WC. Originality/value The results of the experimental studies demonstrated that hard coatings improving wear resistance of WC.
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    Dry-sliding wear behavior of AISI 4140 barrel steel at elevated temperatures
    (Carl Hanser Verlag, 2020) Kocyigit, Fatih; Yildiz, Fethullah; Gok, M. Sabri; Cay, Vedat Veli
    In this study dry sliding wear behavior of AISI 4140 steel at given elevated temperatures was examined. The experiments were performed on a heat-modulated ball-on-disc wear device under 3, 5, 7 and 10 N loads at room temperature, 100, 200, 300 and 450 degrees C. 3D optical microscopy was performed for determining the volume loss of the worn samples. SEM (scanning electron microscopy) was used to determine the morphology of the worn surfaces of the samples while Raman spectrometry was used for determining oxide types occurring as a result of wear. Experimental applications showed that volume loses slightly increased as a function of indenter load elevation. The experiments performed at 300 degrees C, the volume loss ratios were found to be lower compared to all other samples. The highest volume loss was obtained in the experiments performed at 450 degrees C. Volume loss decreased in all samples under 10 N load. A tribological layer formed on the surface of samples subjected to a dry-sliding process. In the experiments performed at 100 degrees C and 200 degrees C, the delamination type was the dominant wear mechanism at all loads.
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    The Effect of Natural Resin on Thermo-physical Properties of Expanded Vermiculite-Cement Composites
    (Springer/Plenum Publishers, 2020) Kocyigit, Fatih; Cay, Vedat Veli
    This study focuses on production of lightweight concrete that presents thermal insulation property. Lightweight concretes were produced using resin-added cement and expanded vermiculite. The rates of expanded vermiculite were determined as 20%, 40%, 60%, and 80% of the total volume in the mixture. The amount of tragacanth resin in the mixture was detected as 0%, 0.5% and 1% of the total weight of cement and expanded vermiculite. Thermal, mechanical and microstructure properties of the samples produced were determined. Porosity ratio increased by 15.01% to 55.22%, 0.5% and 1% in samples without resin and by 18.97% to 57.88% and 19.64% to 60.73% in resin-added samples, respectively. As the resin increased, density, thermal conductivity, compressive strength decreased and porosity, abrasion loss and water absorption rates increased. Similarly, when expanded vermiculite rate of the samples without resin in the mixture was increased from 20% to 80%, density, thermal conductivity, and compressive strength decreased at the rates of 14.13% to 21.29%, 14.32% to 24.36%, and 31.37% to 39.82%, respectively, compared to 0.5% resin samples and the rates of 12.34% to 13.05%, 12.37% to 19.59%, and 17.65% to 35.29% compared to 0.1% resin samples. Also, the water absorption rates of the samples were found to be lower than 30%, which is the critical value. It was shown that expanded vermiculite and tragacanth resin-added lightweight concrete samples would provide a good performance in non-load bearing places in the buildings, in the partitions instead of bricks, in the ceiling and floor covering, and as plaster and gypsum.
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    Experimental analysis and modeling of the thermal conductivities for a novel building material providing environmental transformation
    (Taylor & Francis Inc, 2020) Kocyigit, Fatih; Unal, Fatih; Kocyigit, Sermin
    In this study, a mathematical equation was developed to determine the thermal conductivity of the materials by producing porous heterogeneous materials with expanded vermiculite aggregates, waste basalt powder, and the mixture of molten tragacanth added building materials. Experimental thermal conductivity of the samples was determined by using the hot wire method. Experimental thermal conductivity of the samples produced varied between 0.196 W/mK and 0.522 W/mK depending on the expanded vermiculite ratio, the ratio of waste basalt powder, and the ratios of tragacanth and cement. In addition, the developed mathematical thermal conductivity ranges from 0.201 W/mK to 0.455 W/mK. The experimental values deviated from the values in the developed model in the range of 3-19%. This equation was developed based on the porosity ratio of the produced samples, the density and thermal conductivity of the materials in the samples. The thermal conductivity results obtained by the experimental and theoretically developed equation were compared with each other and it was observed that the results were compatible.
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    Impact of a low thermal conductive lightweight concrete in building: Energy and fuel performance evaluation for different climate region
    (Academic Press Ltd- Elsevier Science Ltd, 2020) Ustaoglu, Abid; Kurtoglu, Kubra; Gencel, Osman; Kocyigit, Fatih
    Evaluation of energy performance of a proposed lightweight concrete, a structural component, in a building application is a novel approach and significant attempt for the future of energy-efficient buildings. Buildings are one of the largest energy consumers in the world. Thermal protection in a building is the most effective way for energy saving. Many stimulatory measures for the spreading of energy savings technologies have been recently applied into the building sectors. In this study, an investigation was carried out based upon an experimental investigation to decide the thermal properties of the lightweight concrete with different ratios of vermiculite. Moreover, analytical simulation to evaluate the energy consumption in a real building application was carried out for various fuels and different climate regions of Turkey. The results show that the most significant reduction in the total heat need occurs in the 4th region, with about 5.6 kWh/m(2)-year for a thickness of 0.2 m. An energy-saving of 7.5% can be achieved in the 1st region. The proposed concrete can provide a significant reduction in energy consumption and can reduce the carbon emission related to the lower energy need of the buildings. The annual saving can increase to 0.61 $/m(2) for LPG in the 4th region. The payback period varies between 1.4 years and 9 years, depending on the fuel. Many OECD countries having a high population pay higher prices for electricity and natural gas compared to Turkey. It means that such an energy-efficient material can save more price due to their higher fuel cost.
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    Investigation of Energy Saving Potential in Buildings Using Novel Developed Lightweight Concrete
    (Springer/Plenum Publishers, 2020) Akan, Ahmet Erhan; unal, Fatih; Kocyigit, Fatih
    In this study, three different composite materials were produced from mixtures of natural and waste materials in different proportions. The produced composites were used to determine the insulation thickness of exterior walls of buildings located in 12 provinces selected from the four different climate zones of Turkey. The selection of provinces was made according to Turkish standard TS 825. The produced materials are thermal insulation elements that can be used instead of construction elements, such as brick, on the exterior walls of the buildings. In this study, only the heating of the buildings was considered and the number of heating degree days of the provinces was taken into account to determine the insulation thickness. The life cycle cost analysis method was used to determine the optimum insulation thickness. It was determined that the optimum insulation thickness values calculated for four different fuel types for the selected provinces varied between 0.170 m and 1.401 m. The annual energy requirement for the unit surface area of the exterior walls of the insulated buildings was determined to be 11,213-965,715 kJ center dot m(-2) per year. Moreover, it was determined that the insulation costs ranged between $ 22,841 m(-2) and $ 114,841 m(-2), and the payback period ranged from approximately 2.5 to 6.5 years. It was concluded that using these new types of materials in the determined regions were advantageous in terms of thermal insulation, fire resistance, mechanical properties, production costs, extra labor costs, and optimum insulation thickness.
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    Investigation of Thermal and Strength Properties of a Novel Composite Developed for Insulation as Building Material
    (Springer/Plenum Publishers, 2020) Kocyigit, Fatih
    The aim of the present study is to produce novel developed composite materials which provide thermal insulation by using waste and natural materials in construction applications. Composite construction samples were prepared using an expanded perlite aggregate of 15 % wt., 30 % wt., and 45 % wt., which had the grain sizes of 0-3 mm, 3-5 mm and 5-8 mm, as well as waste marble dust of 5 % and 15 % filtrated from a 300 mu m sieve, combined with molten tragacanth of 0 %, 0.5 % and 1 %, and CEMI 42.5 N-type portland cement. The microstructure of the composite samples was examined by the SEM analysis. Density, thermal conductivity, compressive strength, abrasion loss, water absorption, compressive strength after high temperature, and compressive strength after freeze-thaw tests were performed on these composite samples. It was found that the density values of composite materials decreased from 1.983 g center dot cm(-3) to 0.933 g center dot cm(-3). It was observed that their porosity ratios up to 43 % were improved by increasing the amount of waste marble dust, expanded perlite and molten tragacanth, additionally, while their compressive strengths decreased. Thermal conductivity of the porous samples decreased from 0.468 W center dot m(-1)center dot K-1 to 0.167 W center dot m(-1)center dot K-1 by raising their porosity, which corresponds to a reduction of 36%. It was observed that as the rates and sizes of the materials used in the samples, their thermal conductivity, compressive strength and density values decreased, and the abrasion loss and water absorption increased.