Gürol Önal

Regression Modeling of Surface Roughness in Grinding

Grinding is a widely used manufacturing method in state of art industry. By realizing needs of manufacturers, grinding parameters must be carefully selected in order to maintain an optimum point for sustainable process. Surface roughness is generally accepted as an important indicator for grinding parameters. In this study, effects of grinding parameters to surface roughness were experimentally and statistically investigated. A complete factorial experimental flow was designed for three level and three variable. 62 HRC AISI 8620 cementation steel was used in grinding process with 95-96% Al2O3 grinding wheel. Surface roughness values (Ra, Rz) were measured at the end of process by using depth of cut, feed rate and workpiece speed as input parameters. Experimental results were used for modeling surface roughness values with linear, quadric and logarithmic regressions by the help of MINITAB 14 and SPSS 16 software. The best results according to comparison of models considering determination coefficient were achieved with quadric regression model (84.6% for Ra and 89% for Rz). As a result, a reliable model was developed in grinding process which is a highly complex machining operation and depth of cut was determined as the most effective parameter on grinding by variance analysis (ANOVA). Obtained theoretical and practical acquisitions can be used in various areas of manufacturing sector in the future.

Sedimentation of Clays prior to Ceramic Production

Sedimentation of concentrated clays has always been difficult and taken long times due to their nature and having small particle sizes. Sedimentation behaviors of clay mixtures, taken from Kalemaden A.Ş., prior to being used in the ceramic production, were investigated. The effects of pulp density, flocculant addition and ultrasonic treatment on the sedimentation of clays were examined and discussed in relation to their chemical and physical properties. Introduction In Kalemaden A.Ş., which is one of the most important clay preparation and concentration plant in Turkey, four different types of clay mixtures namely a mixture of clays from Balıkesir-Düvertepe and Istanbul-Şile (Clay 244), a mixture of clays from Ukraine and Balıkesir-Düvertepe (Clay 248), Söğüt-Kadıkelimesi (Clay 261), a mixture of clays from Söğüt and Istanbul-Şile(Clay 262) and a kaolin from Balıkesir-Düvertepe region of Turkey (Kaolin 143) are concentrated before their use in ceramic production. Dewatering is the important step in those types of concentration plants. Concentrated clays have usually small particle sizes and thus their sedimentation has always been difficult and taken long times. Flocculants can be used to enhance the sedimentation, but they are not preferred by the ceramic industry since they affect the quality of ceramic products. For this purpose ultrasonic treatment is used in the sedimentation of clays in order to solve the problems encountered related to the ceramic industry. Experimental In this experimental study, clay samples were brought from the plant (Kalemaden A.Ş.-Clay and Kaolin Concentration Unit) as pulps in containers and thoroughly mixed with a stirrer before sedimentation experiments. The chemical and size analyses of the samples used in the tests were made by Kalemaden A.Ş. laboratories and results are given in Table I. A two liter graduated cylinder and an ultrasonic bath (with 25 kHz frequency and 0.5 KW power) were utilized in the tests. According to the preliminary studies Superfloc A-120 was found the most effective flocculant and thus used in the tests [1]. Superfloc A-120 (0.1% concentration) is an anionic type flocculant with a molecular weight of 10-15.10, 150 cP viscosity and 26-32 degree of charge. The settling distance was reported against the settling time during the experiments. Initial and final pulp densities were also determined. The effects of several parameters such as pulp density, flocculant addition, and ultrasonic treatment on the sedimentation of clays were investigated and the results were represented in terms of settling distance versus settling time. Results and Discussions Sedimentation curves of of clay mixtures in natural and ultrasonic media (both experiments were run at the initial pulp density of 9%) are plotted in Figure 1 and Figure 2, respectively. As it seen from both figures that clay mixtures examined here have different sedimentation rates in both media. Clay 261 and Kaolin 143 samples have the highest settling rates among them. These samples have the lowest K2O contents (0.13-0.59%) as compared to the others (1.49, 2.56, 2.49%), as seen in Table 1. On the other hand, Al2O3 contents of the clays having higher settling rates are about 32Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 1439-1442 doi:10.4028/www.scientific.net/KEM.264-268.1439

HHO HÜCRE PERFORMANSININ BULANIK MANTIK YÖNTEMİ İLE BELİRLENMESİ

Bu calismada, Hidroksi (HHO) hucre performanslari, kural tabanli Mamdani tipi bulanik modelleme teknigi ile gerilim, akim ve sicaklik parametreleri bakimindan modellenmistir. Giris parametreleri plaka sayisi ve zaman (t), cikis parametreleri gerilim (V), akim (A) ve sicaklik (oC); Kural Tabanli Mamdani Tip Bulanik Mantik (KTMTBM) tarafindan tanimlanmistir. Giris ve cikis parametrelerinin sayisal verileri bulaniklastirmistir. Bunlar; cok cok dusuk (L1), cok dusuk (L2), dusuk (L3), negatif orta (L4), orta (L5), pozitif orta (L6), yuksek (L7), cok yuksek (L8) ve cok cok yuksek (L9)’dir. Bu sistem icin 2 giris degeri bulunmakta ve her bir cikis degeri icin 9x9 matrisinden 81 kural olmak uzere toplam 243 kural elde edilmistir. Sistemin girisi ile cikisi arasindaki iliskiyi tanimlayan ve bulanik mantik denetleyicinin davranislarini tespit eden denetim kurallarinin bir sonucu olarak, deneysel calismadan elde edilen her bir deger ayni zamanda bulanik mantik ile belirlenmistir. Bulanik mantik yontemiyle olusturulan modelden elde edilen sonuclar ile deneysel calismada tespit edilen sonuclar determinasyon katsayisi yontemi (R2) kullanilarak karsilastirilmistir. R2 yonteminde, voltaj, akim ve sicaklik icin sirasiyla %98,29; %99,5; %96,47 degerleri tespit edilmistir.Ayrica, deneysel calismada yapilmamis degerler BM modeli sayesinde tahmin edilmistir. Bu calisma, HHO hucresinin performansinin belirlenmesinde, bulanik mantik yonteminin basariyla uygulanabildigini gostermistir.

Modeling of the Effects of Cyclic Voltammetry (CV) Using Fuzzy Logic with Different Membership Functions for Proton Exchange Membrane Fuel Cell (PEM) with Polyvinyl Alcohol/Nano Silver (PVA/Ag)

In this study, the effects of cyclic voltammetry (CV) has been modeled with Rule-based mamdani-type fuzzy (RBMTF), by using experimental data for proton exchange membrane fuel cell with PVA/AG. In the system developed, RBMTF apply input parameters are CV, scan rate and time, output parameters are current density and voltage. 12300 values for experimental study also obtained with RBMTF. Membership functions (MFs) are the building blocks of fuzzy set theory, i.e., fuzziness in a fuzzy set is determined by its MF. Accordingly, the shapes of MFs are important for a particular problem since they effect on a fuzzy inference system. They may have different shapes like triangular, trapezoidal, Gaussian, etc. When the results obtained from RBMTF and statistical analyses of experimental data have been compared, it has been determined that the two groups of data are coherent, and that there is not a significant difference between them. As a result, this study indicates that RBMTF with different membership functions can be safely used for CV.

Investigation of Electrical Conductivity of Polyacrylonitrile (PAN) Nanofibers/Nano Particul (Ag,Cu, CNT and GNR)

In this study 1% Ag (silver), Cu (copper), CNT (carbon nanotube) and graphene nanoribbon (GNR) nanoparticle reinforced PAN fibers were prepared and the effects of nanoparticle reinforcements upon electrical conductivity were investigated. In experimental study, graphene nanoribbon powders were produced from multiwalled carbon nanotube (MWCNT) through using the chemical approach of Hummers method. Fiber layer was dissolved at room temperature in magnetic mixer with Polyacrylonitrile (PAN) and Dimethil Formamide (DMF) which was at the rate of 10 % by mass. Thus, a viscou gel solution was obtained then nanoparticles were added to the PAN/DMF solution and the solution was vigorously stirred for one hour at room temperature. After stirring that solution was continued for 15 m in ultrasonic bath. The polymeric solution was first transferred to a 5 mL syringe, which was connected to a capillary needle with an inside diameter of 0,8 mm. A copper electrode was attached to the needle, a DC power supply produces 25 kV against a grounded collector screen distant 15cm. With the syringe pump set at 2 mL/h, the electric force overcomes the surface tension of the solution at the capillary tip, and a jet emerges. Produced fibers were collected on the rotary collector which spins at 250 rpm. Nanofiber was dried at 60 °C for 12 h in vacuum oven. Eventually, nanofiber of polyacrylonitrile (PAN) reinforced by metallic nanoparticles and graphene nanoribbon (GNR) were prepared by electro spinning process. Electrical conductivity of the obtained nanofiber were studied by measuring the electrical resistance thanks to home-made plate electrodes.