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    The effect of head hardening process on the residual stress of rails
    (Sage Publications Ltd, 2018) Turan, Muhammet E.; Ozcelik, Sait; Husem, Fazil; Ahlatci, Hayrettin; Sun, Yavuz; Tozlu, Ibrahim
    In this study, the head hardening process was employed, by using a mixture of air and water under laboratory conditions, to improve the residual stress behavior of R260 grade rails . For this purpose, three types of specimens were selected. One group of rails was heated up to the austenite stage and then cooled for 20 s; the next group was heated up to the austenite stage and then cooled for 40 s and the third group was not exposed to any heat treatment. The hardness results showed that the specimens cooled for 40 s had excessive hardness; the specimens cooled for 20 s exhibited similar properties as that of R350HT rail standards, which are especially preferred in the lower radius of curvature bends in railways, but not that of R260. According to the analysis of residual stress, all samples had compressive residual stress, but the specimens cooled for 20 s had the highest stress value.
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    Mechanical Properties of Pattern Welded 1075-15N20 Steels
    (Carl Hanser Verlag, 2014) Ozkan, Furkan; Kirdan, Hakan; Kara, Ismail Hakki; Husem, Fazil; Ozcelik, Sait; Akinay, Yuksel; Cug, Harun
    Forged welded (damascus) steels are produced by traditional methods and mostly used in the design of decorative tools. These steels are well-known for their good mechanical properties. The process for making forged welded (damascus) steel consists of stacking alternating sheets of different kinds of steel on top of each other and then forge welding them together. In this study, the steels 1075 and 15N20 were used for the forging and folding procedure. The effect of fold numbers on the microstructure and mechanical behavior were investigated. The steel consisted of both materials, 54 and 250 layers, respectively, produced by forge welding. The pattern layers are homogeneous and regular, but after the process sections with up to 54 pattern layers were irregular. Steel 1075 has a pearlitic microstructure, while steel 15N20 has a ferritic microstructure. The impact toughness and tensile strength of the folded steels improved with increasing the number of folds.
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    RESIDUAL STRESS MEASUREMENT IN RAILS BY DESTRUCTIVE AND NON DESTRUCTIVE METHOD
    (Tanger Ltd, 2015) Turan, Muhammet Emre; Ozcelik, Sait; Zengin, Huseyin; Ahlatci, Hayrettin; Turen, Yunus; Tozlu, Ibrahim; Sun, Yavuz
    Residual stress is an elastic stress in remaining part after the various stages of production. If residual stress values in rails are known, mechanical properties of rails and their effects in railway can be predicted. For this purpose, residual stresses of rails which had same casting number were measured by cutting and X-ray diffraction method in this study. Five rails were used for measurement. Firstly, according to the EN 13674-1 which is railway rails standard, strain gauge that is an electrical apparatus were used and one meter long rails were cut. After cutting, Hooke law was applied and residual stress values of rails were found. The residual stress values were around between 115 MPa and 180 MPa. In addition to standard residual stress measurement, X-ray diffraction method was used to compare between destructive and nondestructive techniques. Five specimens were taken from five rails in the appropriate size for X-ray device. In this method stress values were around between 200 and 400 MPa. After residual stress measurement, Brinell's hardness test was applied to three samples and microstructure of rail which has biggest residual stress value was examined by SEM. The results show that, residual stress values in cutting method were different from X-ray diffraction method and residual stress could affect the rails hardness.