Wyniki wyszukiwania - Biblioteka Nauki

1

Investigating surface water pollution by integrated remotely sensed and field spectral measurement data: a case study

100%

Gursoy O. , Atun R.

Polish Journal of Environmental Studies

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2019

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tom 28

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nr 4

EN

Water quality assessment using remote sensing and its terrestrial components is carried out in short time for larger areas. Another issue that is as important regarding water availability is access to quality water. It is important to investigate the availability of the analysis of remotely sensed data instead of environmental and chemical analysis that determines water quality and usability. To examine the detection of water qualities without taking water samples in situ, spectral library data was used in the Hafik Region. In this context we used spectral measurement data of water samples previously taken from İmranlı, where the Kızılırmak River originates, and used for spectral classification of water quality. Matched filtering was used for integrating spectral data and CHRIS Proba image as the spectral classification method. To conduct an accuracy analysis, chemical oxygen demand measurement was carried out at 10 points determined as 1st and 2nd water quality in the study area on the river and lakes according to the Ministry of the Environment and Urbanization. The overall accuracy of the classification was calculated as 70%. The results of this study have shown the importance of spectral classification of satellite imagery in evaluating water quality and monitoring water resources.

2

Evolution of Aluminium Melt Quality of A356 After Several Recycling

80%

Gursoy O. , Erzi E. , Tur K. , Dispinar D.

Archives of Foundry Engineering

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2020

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tom Vol. 20, iss. 4

61--66

EN

Recyclability is one of the great features of aluminium and its alloys. However, it has been typically considered that the secondary aluminium quality is low and bad. This is only because aluminium is so sensitive to turbulence. Uncontrolled transfer and handling of the liquid aluminium results in formation of double oxide defects known as bifilms. Bifilms are detrimental defects. They form porosity and deteriorate the properties. The detection and quantification of bifilms in liquid aluminium can be carried out by bifilm index measured in millimetres as an indication of melt cleanliness using Reduced Pressure Test (RPT). In this work, recycling efficiency and quality change of A356 alloy with various Ti additions have been investigated. The charge was recycled three times and change in bifilm index and bifilm number was evaluated. It was found that when high amount of Ti grain refiner was added, the melt quality was increased due to sedimentation of bifilms with Ti. When low amount of Ti is added, the melt quality was degraded.

3

Evolution of Aluminium Melt Quality of A356 After Several Recycling

71%

Gursoy O. , Erzi E. , Tur K. , Dispinar D. , Gursoy O. , Erzi E. , Tur K. , Dispinar D.

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tom 20

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nr 4

4

Challenges in Producing Reliable Tensile Properties by SIMA 7075

70%

Erzi E. , Gursoy O. , Yüksel Ç. O. K. , Kirtay S. , Dispinar D.

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tom Vol. 18, iss. 3

71--75

EN

Aluminium alloys are one of the preferred materials especially for land and air transportation because of their high strength and low-density properties. Although production using casting method is economical yet it has some disadvantages. Shrinkage which is occurred due to the density difference between the solid and liquid metal is prevented by feeders which need to be calculated. Liquid metal should be transferred to the mould without any turbulence. As a result, sprues are needed to be designed precisely. On the other hand, aluminium alloys can also be shaped by forging at semi-solid temperatures. There are some advantages compared to the traditional forging methods of improving die life due to the lower tonnage values. In this study, semi-solid produced 7075 aluminium alloy die filling capabilities were investigated. To achieve semisolid structure strain induced melt activated method (SIMA) was used. The desired structure was achieved at 635°C and 30 minutes of duration of heat treatment. After determining the optimum parameters, metallographic analysis, density calculations, porosity distribution and tensile tests were carried out. It was found that the reproducibility of SIMA produced 7075 alloy was quite low. A proper tensile test result was achieved only 7 of the total 15 tests and the mean value was 386 MPa. The main reason for this scattered in mechanical properties could be the chemical composition of the alloy and the rapid solidification of the liquid eutectic phases. It is important to define the best fitting process parameters and controlling them precisely will be the most important factors for future studies.

5

Role of Metal Quality and Porosity Formation in Low Pressure Die Casting of A356: Experimental Observations

61%

Gursoy O. , Nordmak A. , Syversten F. , Colak M. , Tur K. , Dispinar D.

Archives of Foundry Engineering

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2021

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tom Vol. 21, iss. 1

5--10

EN

Porosity is one of the major problems in casting operations and there are several discussions in the literature about the porosity formation in aluminum castings. Bifilms are the defects that are introduced into the melt by turbulence. They can be detected with reduced pressure test and presented numerically by measuring bifilm index. The measure of bifilm index is the sum of total oxide length given in millimeters from the cross-section of reduced pressure test sample solidified under 0.01 MPa. In this work, low pressure die casting (LPDC) unit was built in an attempt to enhance the producibility rate. The unit consists of a pump housing that was placed inside the melt in the melting furnace where the pressure was applied instead of the whole melt surface. It was observed that the melt quality of A356 alloy was deteriorated over time which had led to higher porosity. This was attributed to the increased oxide thickness of the bifilm by the consumption of air in between the folded oxides. A relationship was found between bifilm index and pore formation.

6

Prediction of Fracture Stress with Regard to Porosity in Cast A356 Alloy

57%

Sahin H. , Atik M. , Tezer F. , Temel S. , Aydin O. , Kesen O. , Gursoy O. , Dispinar D. , Sahin H. , Atik M. , Tezer F. , Temel S. , Aydin O. , Kesen O. , Gursoy O. , Dispinar D.

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7

Role of Metal Quality and Porosity Formation in Low Pressure Die Casting of A356: Experimental Observations

57%

Gursoy O. , Nordmak A. , Syvertsen F. , Colak M. , Tur K. , Dispinar D. , Gursoy O. , Nordmak A. , Syvertsen F. , Colak M. , Tur K. , Dispinar D.

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nr 1

8

Prediction of Fracture Stress with Regard to Porosity in Cast A356 Alloy

51%

Sahin H. , Atik M. , Tezer F. , Temel S. , Aydin O. , Kesen O. , Gursoy O. , Dispinar D.

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tom Vol. 21, iss. 4

21--28

EN

Production of the defect-free casting of aluminium alloys is the biggest challenge. Porosity is known to be the most important defect. Therefore, many cast parts are subjected to several non-destructive tests in order to check their acceptability. There are several standards, yet, the acceptance limit of porosity size and distribution may change according to the customer design and requirements. In this work, the aim was targeted to evaluate the effect of size, location, and distribution of pores on the tensile properties of cast A356 alloy. ANSYS software was used to perform stress analysis where the pore sizes were changed between 0.05 mm to 3 mm by 0.05 mm increments. Additionally, pore number was changed from 1 to 5 where they were placed at different locations in the test bar. Finally, bifilms were placed inside the pore at different sizes and orientations. The stress generated along the pores was recorded and compared with the fracture stress of the A356 alloy. It was found that as the bifilm size was getting smaller, their effect on tensile properties was lowered. On the other hand, as bifilms were larger, their orientation became the dominant factor in determining the fracture.