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https://hdl.handle.net/20.500.12587/18123

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Effect of sintering temperature on pore ratio and mechanical properties of composite structure in nano graphene reinforced ZA27 based composites
(SPRINGER, 2020) Pul, Muharrem
Nano graphene platelet (Gr) reinforced nano composites with a zinc-aluminum alloy (ZA27) matrix were produced by powder metallurgy at four different mass ratios (0.5wt%, 1.0wt%, 2.0wt% and 4.0wt%) and three different sintering temperatures (425, 450, and 475 degrees C). In order to investigate the effect of sintering temperatures and nano graphene reinforcement materials on the composite structure, the microstructures of the composite samples were investigated and their densities were determined with a scanning electron microscope. Hardness, transverse rupture, and abrasion wear tests were performed to determine the mechanical properties. According to the test results, the porosity increased and the mechanical strength of the nano composites decreased as the amount of nano graphene reinforcement in ZA27 increased. However, when the composites produced in different reinforcement ratios were evaluated, the increase in sintering temperature increased the mechanical structure by positively affecting the composite structure.
Investigation of the tool wear, surface roughness, and chip formation in the machining of ZrO2-reinforced aluminum composites
(SPRINGER HEIDELBERG, 2020) Pul, Muharrem
The aim of this study is to reveal how ZrO2(zirconia) contributes to the machinability of aluminum 1050. In the first stage of this study, composite materials were produced by the vortex method by adding different amounts of ZrO2(5%, 10%, 20%, and 30%) into commercial aluminum of 99.5% purity. Then, microstructure images of composite materials were taken under the scanning electron microscope (SEM), and the hardness of these composite materials was measured. In the last stage, the machinability tests of the composite materials were performed on the lathe under dry machining conditions at 125, 175, and 225 m/min cutting speeds and 0.03-0.06 and 0.12 mm/rev feed rates, with 1.5 mm constant depth of cut. Uncoated cementite carbide cutting tool inserts were used in machining tests. SEM images of the cutting tool inserts were taken, and the roughness values of the machined surfaces were measured. Chip samples were taken and investigated. It was observed that all the cutting tools had a Built-Up Edge (BUE) formation. Surface roughness and BUE formation increased as the feed rates were increased and decreased with increasing cutting speed. The roughness values decreased slightly and then increased again depending on the ZrO(2)ratio. As the feed rates increased, a transition from ribbon chip type to the helical and saw-toothed forms was observed. It was also observed that the chip formation changed depending on the amount of ZrO(2)in the composite structure.
Investigation of Mechanical Properties of B4C / SiC Additive Aluminum Based Composites and Modeling of Their Ballistic Performances
(Gazi Univ, 2020) Pul, Muharrem; Baydaroglu, Volkan
In this study, 7075 grade aluminum-based composites reinforced with SiC (silicon carbide) and B4C (boron carbide) were produced with powder metallurgy at 40%, 20% and 10% reinforcement ratios. The mechanical properties of the composite samples produced in the first stage experiments were investigated. For this purpose, density, hardness, cross fracture and abrasive wear tests were performed. The results of the experiments were evaluated together with the microstructure and the microscope images of the composite samples. In the second stage of the study, the composite samples were modeled and their ballistic performance was examined by the finite element method. In ballistic analysis, 10% reinforced composites could not perform, while ballistic performance was obtained in increasing reinforcement ratios. When the production, hardness, wear and ballistic analyzes of the samples were evaluated together, it was seen that the reinforcement rate of 40% was high in such composites and not suitable for mechanical properties, 20% of the reinforcement ratio was both productibility and ballistic optimum result.
Effect of sintering on mechanical property of SiC/B4C reinforced aluminum
(Iop Publishing Ltd, 2019) Pul, Muharrem
In this study, SiC (silicon carbide) and B4C (boron carbide) added Al 7075 based composites were prepared at 40%, 20% and 10% reinforcement ratios. Using powder metallurgy, composite sample with 9 different structures were produced at 700 MPa pressing pressure, at 550 degrees C in 90, 120, 150 min applying three different sintering times. According to Archimedes principle, theoretical densities of composite samples were calculated. Then, the hardness measurements and transverse rupture tests were conducted. Lastly, wear tests were conducted using the Pin on Disc Method. Images of composite samples were taken at optical microscope and Scanning Electron Microscope (SEM), and the microstructures were examined. It was determined that increase in SiC and B4C reinforcement ratios decreased the fracture resistance. However, when every reinforcement ratio was evaluated separately, it was observed that increase in sintering time affected the fracture resistance positively. Increase in sintering time also increased the density values, and the hardening values and wear resistance decreased. Increase in reinforcement ratios and sintering time affected the composite wear behavior negatively. Increase in reinforcement ratio in composite structure decreased the density; however, hardening values increased. In conclusion, in such type of composites, reinforcement ratios in definite proportions (similar to 20%) affect mechanical features positively, and excess in that ratio affect mechanical features negatively. Especially 40% reinforcement ratio was high for such type of composites and was not suitable for mechanical features.
Investigation of cutting tool wear behaviors in machining of silicon carbide and magnesium oxide reinforced aluminum 2024 matrix composites
(Iop Publishing Ltd, 2019) Pul, Muharrem
In this study, first Silicon Carbide (SiC) and Magnesium Oxide (MgO) powders of <= 105 micron particle size were mixed in equal amounts. Then, the powder mixture was reinforced by using vortex method in liquid Al2024 aluminum alloy in three different ratios (3%, 6% and 12%) to produce composites. Finally, on composite samples, machinability tests were carried out with a uniform cutting tool at constant cutting depth (1 mm) and dry cutting conditions. Three different cutting speeds (100, 150, 200 m min(-1)) and three different feed values (0.03; 0.06; 0.12 mm/rev) were used in the machining experiments. Machinability tests were performed on a Computer Numerically Controlled (CNC) lathe. Wear behavior of cutting tools were examined by using SEM microscope images. In all of the cutting tools, built-up edge (BUE) was observed while small amount of flank wear occurred. It was concluded that the selected cutting tool and cutting parameters maybe suitable for the machining of such composite materials.
Effect of B4C Reinforcement Ratio and Sintering Temperature on the Mechanical Behavior in Al-B4C Composites
(Int Inst Science Sintering (I I S S), 2018) Pul, Muharrem
In this study, powders of Al 1070 and B4C were prepared by volume in three different reinforcement ratios 4 % B4C, 8 % B4C and 16 % B4C compacted under the pressure of 500 MPa with cold pressing method then sintered under the temperatures of 500, 550 and 600 degrees C. Then the hardness was measured and wear test was performed using pin-on-disk method. In the results of tests, the compression pressure of 500 MPa was not sufficient for composite structure to achieve the required density. The highest hardness values were achieved at sintering temperature of 550 degrees C and in 8 % B4C reinforced composite. The highest wear rate was measured in 4% B4C reinforced composite specimen sintered at 600 degrees C. It is determined that a sintering temperature above 550 degrees C had adverse effects on the mechanical properties.
An Investigation on the Microstructure and Wear Properties of TiB2 Reinforced AA2014 Aluminium Alloy Produced by Vacuum Infiltration
(Walter De Gruyter Gmbh, 2015) Araz, Sule Ocak; Çalın, Recep; Pul, Muharrem; Bican, Osman; Okur, Onur
In this study, microstructural, mechanical and wear properties of TiB2 reinforced Al 2014-based composites produced by vacuum infiltration were investigated under different production temperatures. It was observed that the microstructures of the composites consisted of Al matrix and TiB2 particles. TiB2 particles exhibit various shapes such as cubic, triangle and spherical. It was observed that the hardness and porosity of the composites increased with increasing TiB2 content. It was also observed that the production temperature has an important effect on the porosity and hardness of the produced composites. The highest wear resistance was obtained from Al 2014-8% TiB2 composite among the materials tested. It was observed that the production temperature and hardness are effective parameters on wear of produced composites. Evaluation of microstructural and mechanical test results suggest that it would be beneficial to keep the production temperature around 800 degrees C and Al 2014-8% TiB2 composite can be recommended for engineering applications where the hardness and wear resistance are considered to be significant factors.
The Effect of Reinforcement Volume Ratio on Porosity and Thermal Conductivity in Al-Mgo Composites
(Univ Fed Sao Carlos, Dept Engenharia Materials, 2012) Çalın, Recep; Pul, Muharrem; Pehlivanli, Zuhtu Onur
In this study, the effects of reinforcement volume ratios (RVR) on composite structure and thermal conductivity were examined in Al-MgO reinforced metal matrix composites (MMCs) of 5%, 10% and 15% RVR produced by melt stirring. In the production of composites, EN AW 1050A aluminum alloy was used as the matrix material and MgO powders with particle size of -105 mu m were used as the reinforcement material. For every composite specimen was produced at 500 rev/min stirring speed, at 750 degrees C liquid matrix temperature and 4 minutes stirring time. Composite samples were cooled under normal atmosphere. Then, microstructures of the samples were determined and evaluated by using Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis. In general, it was observed that the reinforcement exhibited a homogeneous distribution. Furthermore, it was determined that the increase in the RVR increased porosity. From the Scanning Electron Microscope images, a thermal Ansys model was generated to determine effective thermal conductivity. Effective thermal conductivity of Al-MgO composites increased with the decrease in reinforcement volume ratio.
Artificial neural network analysis of heat pumps using refrigerant mixtures
(Pergamon-Elsevier Science Ltd, 2004) Arcaklioglu, E; Erisen, A; Yilmaz, R
In this study, we have investigated the performance of a vapor compression heat pump with different ratios of R12/R22 refrigerant mixtures using artificial neural networks (ANN). Experimental studies were completed to obtain training and test data. Mixing ratio, evaporator inlet temperature and condenser pressure were used as input layer, while the outputs are coefficient of performance (COP) and rational efficiency (RE). The back propagation learning algorithm with three different variants and logistic sigmoid transfer function were used in the network. It is shown that the R-2 values are about 0.9999 and the RMS errors are smaller than 0.006. With these results, we believe that the ANN can be used for prediction of COP and RE as an accurate method in a heat pump. (C) 2003 Elsevier Ltd. All rights reserved.

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