Yazar "Husem, Fazil" seçeneğine göre listele

Listeleniyor 1 - 11 / 11
  • Küçük Resim Yok
    Öğe
    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.
  • Küçük Resim Yok
    Öğe
    Effects of constrained groove pressing, severe shot peening and ultrasonic nanocrystal surface modification on microstructure and mechanical behavior of S500MC high strength low alloy automotive steel
    (Elsevier, 2021) Karademir, Ibrahim; Celik, Mustafa B.; Husem, Fazil; Maleki, Erfan; Amanov, Auezhan; Unal, Okan
    S500MC high strength low alloy automotive steel is exposed to bulk severe plastic deformation (SPD) via constrained groove pressing (CGP) and surface severe plastic deformation (S2PD) via severe shot peening (SSP) and ultrasonic nanocrystal surface modification (UNSM). SSP and UNSM could create a nanocrystallization layer till 50-100 mu m away from outmost surface. EBSD investigations showed average nano-grain size obtained via SSP and UNSM was found to be below 100 nm regime. The strength was improved via 1st to 4th pass of CGP, but elongation percentage decreased abruptly. UNSM achieves both strength-ductility improvement with gradient structure. SSP improves the total elongation however a slight decrease on strength is observed. SSP and UNSM showed better wear and friction resistance particularly at lower loads compared to CGP and untreated specimens. Nevertheless, wear and friction behavior at higher loads showed better responses for Bulk-SPD applications regardless of pass numbers. The frictional load increase played a detrimental role in removing a nano crystallization surface layer and diminishing the positive influence of SSP and UNSM.
  • Küçük Resim Yok
    Öğe
    Effects of conventional shot peening, severe shot peening, re-shot peening and precised grinding operations on fatigue performance of AISI 1050 railway axle steel
    (Elsevier Sci Ltd, 2022) Unal, Okan; Maleki, Erfan; Karademir, Ibrahim; Husem, Fazil; Efe, Yusuf; Das, Turan
    In this study, effects of conventional shot peening, severe shot peening, re-shot peening and precised grinding were performed to AISI 1050. By two-stage operations (SSP + RSP), residual stress depth and the magnitude on the surface were quite high. While deepest compressive stress was measured in A24 + G, maximum stress was observed in A24 + N14. Grinding and re-shot peening powerfully reduced the roughness. The increase in SP intensity improved the hardness considerably, besides the most effective hardness depth was observed after A36. N7 and N14 contributed effective results in the low cycle fatigue, whereas A24, A18, A18 + N14 and A36 in high cycle fatigue.
  • Küçük Resim Yok
    Öğe
    Effects of static load on microstructural and mechanical performance of AISI 1050 medium carbon steel subjected to ultrasonic nanocrystal surface modification
    (Elsevier Science Sa, 2022) Unal, Okan; Husem, Fazil; Maleki, Erfan; Karademir, Ibrahim; Efe, Yusuf; Das, Turan
    In this study, the effects of mild (M1, M2, M3), moderate (O1,O2), and severe (S1, S2, S3) static loads of ultrasonic nanocrystal surface modification (UNSM) on AISI 1050 steel were investigated. The layer affected by severe plastic deformation at moderate and severe static loadings became much thicker and the nanocrystalline layer became dominant around the surface region. The layer thickness influenced by the UNSM reached approximately 350 mu m. UNSM had a positive effect on the surface roughness and morphology via reducing the Ra between 0,3 mu m and 0,8 mu m excluding the highest static loads. Oxidation formation was observed on the surface at severe static load conditions. The microhardness showed a significant improvement independently of static loads, and the hardness depth reached up to approximately 250 mu m after the UNSM. Remarkable alteration in surface hardness was observed by increasing static load. Higher static loads ensured both deposition the compressive residual stress to the surface and propagation towards interior. The compressive stress of-700 MPa and a stress depth of over 1 mm were obtained by severe static loading. The processes implemented by moderate and severe static loads showed better performance over both low and high-cycle fatigue behavior.
  • Küçük Resim Yok
    Öğe
    Enhancement in microstructural and mechanical performance of AA7075 aluminum alloy via severe shot peening and ultrasonic nanocrystal surface modification
    (Elsevier, 2020) Efe, Yusuf; Karademir, Ibrahim; Husem, Fazil; Maleki, Erfan; Karimbaev, Ruslan; Amanov, Auezhan; Unal, Okan
    In this experimental study, AA7075 aluminum alloy was subjected to pure severe shot peening (SSP), pure ultrasonic nanocrystalline surface modification (UNSM) and the combination of these two treatments. The treated specimens were analyzed with detailed microstructure analysis, micro-hardness, surface roughness, XRD investigations and wear-friction tests. The results demonstrated that UNSM exhibited fine surface finish and provided minimum surface roughness with the Ra value of 0.8 limo Moreover, UNSM played an important role in the reduction of Ra as a secondary treatment. Electron back scatter diffraction (EBSD) analysis, full width at half maximum (FWHM) evaluations and compressive residual stress (CRS) measurements showed that the deformed layer structure was converted into a nanocrystallized and compressively stressed zone via SSP and UNSM. The hardness on the topmost layer was effectively enhanced by UNSM + SSP and SSP + UNSM processes. The wear and friction performance were particularly improved by two-stage operations of UNSM + SSP and SSP + UNSM. The performance was also compatible with the hardness, residual stress and nanocrystallization investigations.
  • Küçük Resim Yok
    Öğe
    Fatigue crack growth rate of AISI 4140 low alloy steel treated via shot peening and plasma nitriding
    (Pergamon-Elsevier Science Ltd, 2023) Ozturk, Mehmet; Husem, Fazil; Karademir, Ibrahim; Maleki, Erfan; Amanov, Auezhan; Unal, Okan
    In this study, the effects of conventional shot peening (CSP), severe shot peening (SSP), and plasma nitriding (PN) on the fatigue crack growth (FCGR) of AISI 4140 low alloy steel were investigated. FCGR tests were performed on axial fatigue equipment, associated with slow-motion camera and COD gauge. As a result of the experiments, an improvement of 8% in CSP, 15% in SSP, and 5,5% in the PN operations were observed on the number of cycles of all specimens at 30 mm crack length. Particularly for SSP treatments, hardness, compressive stresses, and the creation of nano-crystallization on the surface provide the most effective improvement in FCGR behavior. Additionally, for PN, formation of nitrogen diffusion and effective hardness improvement showed positive results in FCGR behavior. CSP and SSP (particularly SSP) behaved dominant on the improvement of FCGR performance compared to PN treatment. The formation of two-phase brittle structural white layer on the surface prevented the effective FCGR improvement.
  • Küçük Resim Yok
    Öğe
    The formation of gradient nanostructured medium carbon steel via mild, moderate, and severe ultrasonic nanocrystal surface modification options: Assessment on wear and friction performance
    (Elsevier, 2022) Unal, Okan; Maleki, Erfan; Karademir, Ibrahim; Husem, Fazil; Efe, Yusuf; Das, Turan
    In this study, the effect of UNSM applied under different static loads on the microstructure and friction-wear performance were detected. A significant correlation was noticed between the increase of the static load and nanocrystalline layer thickness. Both nanocrystallization layer and deformation depth increased significantly after UNSM. The grain size was measured under 500 nm for M series and 100 nm for O and S series of UNSM static loads. Surface integrity improved remarkably after mild (M) and moderate (O) UNSM (Ra values are 0.25 mu m and 0.7 mu m, respectively). The roughness was achieved approximately under 1 mu m for M and O types and 2 mu m for S types of operations. A 65% increase in hardness emerged by severe UNSM with a surface hardness of approximately 375-430 HV. UNSM demonstrated remarkable results on friction-wear performance by providing higher microhardness and residual compressive stress improvements with lower surface roughness.
  • Küçük Resim Yok
    Öğe
    Influence of aging on mechanical properties, wear and residual stress of a Heusler Al-Cu-Fe alloy
    (Carl Hanser Verlag, 2019) Husem, Fazil; Tezel, Fatma Meydaneri; Turan, Muhammet Emre
    In this study, the ferromagnetic Heusler alloy Al-Cu-Fe was aged at a temperature of 300 degrees C for 0.5 h, 1 h, 1.5 h, 2 h and 2.5 h, respectively. The mechanical and structural properties, residual stress state and wear performance of the specimens were investigated. The results show that precipitation has a crucial influence on the mechanical properties and wear performance of a Heusler alloy. The hardness and wear resistance of the specimens improve with an increase of precipitation density. These precipitates are associated with Cu-rich and Al-Cu lamellar structures. The density of these precipitates reveal two certain Al2Cu peaks at an aging time of 90 minutes, and 150 minutes for the annealed specimens.
  • Küçük Resim Yok
    Öğe
    Investigation of nanostructured surface layer of severe shot peened AISI 1045 steel via response surface methodology
    (Elsevier Sci Ltd, 2019) Unal, Okan; Maleki, Erfan; Kocabas, Ibrahim; Yilmaz, Haluk; Husem, Fazil
    Shot peening (SP) and also severe shot peening (SSP) provide high level compressive residual stress on a certain thickness just beneath the surface. By exposing severe plastic deformation (SPD) via SSP, the nanocrystallization is formed without any chemical alteration and the structure is to be hardened by fully mechanized process. The difference among SP, SSP and repeening (RP) is only related with the selection of the input parameters. Most of the input parameters combination constructs the Almen intensity which is the most powerful condition to be made the decision on the final shot peening of real parts. AISI 1045 medium carbon steel is selected for the optimization of input parameters (shot size, peening duration and air pressure at constant coverage-100%) by investigating the output responses (residual stress, hardness) using response surface methodology. Optimum SP parameters are introduced by response optimizer and the model is verified by the confirmation tests. (C) 2019 Elsevier Ltd. All rights reserved.
  • Küçük Resim Yok
    Öğe
    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.
  • Küçük Resim Yok
    Öğe
    Surface Severe Plastically Deformed Nanostructured AA7075 Alloy: Assessment on Tribological and Axial Fatigue Behaviors
    (Springer, 2020) Efe, Yusuf; Karademir, Ibrahim; Husem, Fazil; Maleki, Erfan; Unal, Okan
    AA7075 alloy is exposed to severe shot peening (SSP) with an Almen intensity of 20A. The microstructure is analyzed via FEGSEM and EBSD microscopy. X-ray diffraction (XRD) analysis is used to evaluate the crystallite size in terms of FWHM measurements. The residual stress measurements show a thicker compressed layer (600 mu m) formed by SSP. Microhardness improvements are observed as 30% on topmost surface and releases substantially after 600 mu m. Coefficient of friction (COF) of treated material remains higher throughout the sliding distance, however, is reduced particularly in the early stage of sliding distance for the wear load of 20 N. The effect of SSP is vanished particularly at lower loads with longer sliding distances. Besides, improvement on fatigue behavior is observed after SSP despite the increase of roughness remarkably.