Experimental Investigation of Porous Bearings Under Different Lubricant and Lubricating Conditions

Durak, Ertugrul The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.9

The performance of porous bearing under different lubricants and lubricating conditions was experimentally investigated in this study. In order to carry out the experiments, a new test rig was designed to determine the tribological properties of based sintered bronze journal bearings that were manufactured by powder metallurgy (P/M) techniques. To determine the effects of lubricating conditions with and without oil supplement (OS) on the tribological characteristics of these bearings under static loading and periodic loadings, some experiments were carried out using different lubricants. In the tests, pure base oil (SAE 20W50), two fully formulated commercial engine oils (SAE20W50) and lubricating oils with commercial additive concentration ratio of 3% were used. The worn surfaces of test bearings were examined using optical microscopy. Experimental results showed that the change in friction coefficient was more stable and in smaller magnitude under static loading than that of periodic loading. In addition, the friction coefficient and the wear rate conducted with base oil resulted in higher values than those of fully formulated oils with and without OS lubricating conditions. The experimental results obtained in this study indicated that the correct selection of lubricant and suitable running conditions were very important on the tribological characteristics of porous bearings.

Magneto‑Impedance in Co35Fe65/Cu/Co35Fe65 Single and Bi‑layer Thin Films

G. Durak Yüzüak,E. Yüzüak,V. Nevruzoğlu 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.5

The magneto-impedance response in Co35Fe65/Cu/Co35Fe65 thin film magneto-impedance cells deposited by the thermalevaporation method has been studied with single and bilayer structures at the substrate temperature 300 K and 150 K. Whilethe thin film deposited at 300 K has BCC structure, the amorphous character is dominant for 150 K deposited ones. Entirefilms show soft magnetic behavior with high saturation magnetization (MS) and low coercive field (HC). Bilayer thin filmstructure reveals higher magneto-impedance values than single-layer thin films. The relation between the magneto-impedanceeffect and layered structure is discussed in terms of structural growing mechanism and scattering effect. The highest magnetoimpedancesensitivity (η) 37%/Oe is observed for the Co35Fe65/Cu/Co35Fe65 bilayer thin film. The HCand remanence ratio(MR/MS) values for single layer at 300 K, single and bilayer cells at 150 K are measured as 51, 158 and 253 Oe—0.48, 0.78,and 0.80, respectively. When η with the Soliton wave model is compared with the sample at room temperature, an increaseof over 1700% is observed. The difference between the classical growing method at 300 K and the Soliton wave model at150 K is the evidence of the logic of the work performed and its accuracy. The relatively high sensitivity is connected withinterlayer usage and low temperature-smaller particle size in Soliton model growth. The observed findings are of practicalimportance to develop future technological magnetic sensor applications with high sensitivity.

Experimental Investigation of Porous Bearings Under Different Lubricant and Lubricating Conditions

Ertugrul DURAK 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.9

The performance of porous bearing under different lubricants and lubricating conditions was experimentally investigated in this study. In order to carry out the experiments, a new test rig was designed to determine the tribological properties of based sintered bronze journal bearings that were manufactured by powder metallurgy (P/M) techniques. To determine the effects of lubricating conditions with and without oil supplement (as) on the tribological characteristics of these bearings under static loading and periodic loadings, some experiments were carried out using different lubricants. In the tests, pure base oil (SAE 2OW50), two fully formulated commercial engine oils (SAE2OW50) and lubricating oils with commercial additive concentra­tion ratio of 3% were used. The worn surfaces of test bearings were examined using optical microscopy. Experimental results showed that the change in friction coetlicient was more stable and in smaller magnitude under static loading than that of periodic loading. In addition, the friction coefficient and the wear rate conducted with base oil resulted in higher values than those of fully formulated oils with and without as lubricating conditions. The experimental results obtained in this study indicated that the correct selection of lubricant and suitable running conditions were very important on the tribological characteristics of porous bearings.

2005년 국제 ITA/EA 컨퍼런스 : 전자정부의 전략적 시사점: 두 개의 국제도시를 중심으로

압둘라두락 ( Abdullah DURAK ) 한국ITA학회 2005 학술대회 Vol.2005 No.-

Thickness induced magnetic anisotropic properties of Tb-Fe-Co thin films

Yüzüak G. Durak,Yüzüak E.,Ennen I.,Hütten A. 한국물리학회 2021 Current Applied Physics Vol.29 No.-

The influence of Tb25Fe61Co14 thin film thicknesses varying from 2 to 300 nm on the structural and magnetic properties has been systematically investigated by using of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, magnetization, and magneto-optic Kerr effect microscopy measurements. Thin film growth mechanism is pursued and controlled by ex-situ X-ray refractometry measurements. X-ray diffraction studies reveal that the Tb25Fe61Co14 films are amorphous regardless of thin films thicknesses. The magnetic properties are found to be strongly related to thickness and preferred orientation. With an increase in film thickness, the easy axis of magnetization is reversed from in-plane to out-of-plane direction. The change in the easy axes direction also affects the remanence, coercivity and magnetic anisotropy values. The cause for the magnetic anisotropy direction change from in-plane to out-of-plane can be related to the preferred orientation of the thin film which depends on the large out-of-plane coercivity and plays an important role in deciding the easy axes direction of the films. According to our results, up to the 100 nm in-plane direction is dominated over the whole system under major Fe-Fe interaction region, after that point, the magnetic anisotropy direction change to the out-of-plane under major Tb-Fe/Tb-Co interaction region and preferred orientation dependent perpendicular magnetic anisotropic properties become more dominated with 2.7 kOe high coercive field values.

Friction and Wear Properties of Cu and Fe-based P/M Bearing Materials

Tufekci Kenan,Kurbanoglu Cahit,Durak Ertugrul,Tunay R. Fatih The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.4

The performances of porous bearings under different operating conditions were experimentally investigated in this study. Material groups studied are 90%Cu + 10%Sn bronze and 1%C + % balance Fe iron-based self-lubricating P/M bearings at constant (85%) density. In the experiments, the variation of the coefficient of friction and wear ratio of those two different group materials for different sliding speeds, loads, and temperatures were investigated. As a result, the variation of the friction coefficient-temperature for both constant load, and constant sliding speed, friction coefficient-average bearing pressure, PV-wear loss and temperature-wear loss curves were plotted and compared with each other for two materials, separately. The test results showed that Cu-based bearings have better friction and wear properties than Fe-based bearings.

An Intradiscal Granuloma Due to a Retained Wooden Foreign Body

Aladag, Mehmet Arif,Durak, Mehmet Akif The Korean Neurosurgical Society 2017 Journal of Korean neurosurgical society Vol.60 No.2

We report a patient with a wooden foreign body granuloma in the intervertebral disc space being symptomatic 17 years after a paraspinal penetrant trauma. According to the our result of the search for wooden foreign body granulomas, this is the first case suffered from a wooden foreign body granuloma in the intervertebral disc space that reported in the literature. In this report, we emphasized the importance of rigorous examination and follow up in paraspinal wooden penetrant traumas.

부분 푸리에 영역과 선형 시간-주파수 분포의 옮김 불변 특성

두락루트피에,강현구,윤석호,이주미,권형문,최상원,송익호,Durak Lutfiye,Kang Hyun Gu,Yoon Seokho,Lee Jumi,Kwon Hyoungmoon,Choi Sang Won,Song Iickho 한국통신학회 2005 韓國通信學會論文誌 Vol.30 No.11c

시간 영역과 주파수 영역을 사이의 공간을 뜻하는 부분 푸리에 영역으로 (fractional Fourier domains) 선형 시간-주파수 분포의 옮김 불변 특성을 일반화한다. 다른 선형 사주파수 분포와 달리 짧은 시간 푸리에 변환은(short time Fourier transform: STFT) 부분 푸리에 영역에서 크기 (magnitude-wise) 옮김 불변을 지니는데, 이 짧은 시간 푸리에 변환을 쓰면 분포를 좀더 쉽게 해석할 수 있다. 특히, 부분 푸리에 영역에서 크기 옮김 불변인 선형 분포는 짧은 시간 푸리에 변환뿐이라는 것을 밝힌다. In this paper, we generalize the shift-invariance properties of linear time-frequency distributions to the fractional Fourier domains that interpolate between the time and frequency domains. Magnitude-wise shift invariance in arbitrary fractional Fourier domains distinguishes the short-time Fourier transform (STFT) among all linear time-frequency distributions and simplifies the interpretation of the resultant distribution. We prove that the STFT is the only linear distribution that satisfies the magnitude-wise shift-invariance property in the fractional Fourier domains.

Friction and Wear Properties of Cu and Fe-based P/M Bearing Materials

Kenan TUFEKCI,Cahit KURBANO?LU,Ertu?rul DURAK,R. Fatih TUNAY 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.4

The performances of porous bearings under different operating conditions were experimentally investigated in this study. Material groups studied are 90%Cu+10%Sn bronze and 1%C+% balance Fe iron-based self-lubricating P/M bearings at constant (85%) density. In the experiments, the variation of the coefficient of friction and wear ratio of those two different group materials for different sliding speeds, loads, and temperatures were investigated. As a result, the variation of the friction coefficient - temperature for both constant load, and constant sliding speed, friction coefficient - average bearing pressure, PV - wear loss and temperature-wear loss curves were plotted and compared with each other for two materials, separately. The test results showed that Cu-based bearings have better friction and wear properties than Fe-based bearings.

Biodiversity and technological properties of yeasts from Turkish sourdough

Arici, Muhammet,Ozulku, Gorkem,Yildirim, Rusen Metin,Sagdic, Osman,Durak, M. Zeki 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.2

In this study, yeasts were isolated and characterized from twelve traditional sourdough samples which belongs to Black Sea and Aegean regions of Turkey. Twenty six yeast species were isolated and identified by both 26S rDNA sequencing and FTIR spectroscopy. Saccharomyces cerevisiae (50%), Torulaspora delbrueckii (40%) and Kluyveromyces marxianus (10%) were found in 12 Turkish traditional sourdough samples. S. cerevisiae was found to be the most dominant species in Aegean region while T. delbrueckii was the most frequently isolated species in Black Sea region. Some technological properties of isolated yeast species such as acidity development, resistance to NaCI and potassium sorbate, and yeast effect on bread quality were investigated. Breads were prepared by S. cerevisiae TGM38 strain demonstrated the highest bread volume compared the other yeasts used in the study. This study showed the yeast diversity and technological properties of traditional Turkish sourdough breads fermented by chosen yeast species.