Browsing by Author "Cetin, Baris"

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Development of an optical measurement system for surface depth measurements and study of focus effect on determination of steel inclusion content by EN-10247
(SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98225, 2021) Durkaya, Goksel; Kurtuldu, Huseyin; Cetin, Baris; Bal, Burak; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Bal, Burak
Surface inspections are important in steelmaking processes to characterize the final product's quality. We present a method to measure surface depth profile using laser scattering geometry. This technique is used to analyze the focus effect on microscopic analyses of steel inclusions using the EN-10247 standard. The results presented herein offer promising new perspectives for the metal manufacturing industry through cost-effective solutions that attain quasi in-line process inspection capabilities. (C) 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)
Effect of hydrogen on fracture locus of Fe-16Mn-0.6C-2.15Al TWIP steel
(PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND, 2020) Bal, Burak; Cetin, Baris; Bayram, Ferdi Caner; Billur, Eren; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü
Effect of hydrogen on the mechanical response and fracture locus of commercial TWIP steel was investigated comprehensively by tensile testing TWIP steel samples at room temperature and quasi-static regime. 5 different sample geometries were utilized to ensure different specific stress states and a digital image correlation (DIC) system was used during tensile tests. Electrochemical charging method was utilized for hydrogen charging and microstructural characterizations were carried out by scanning electron microscope. Stress triaxiality factors were calculated throughout the plastic deformation via finite element analysis (FEA) based simulations and average values were calculated at the most critical node. A specific Python script was developed to determine the equivalent fracture strain. Based on the experimental and numerical results, the relation between the equivalent fracture strain and stress triaxiality was determined and the effect of hydrogen on the corresponding fracture locus was quantified. The deterioration in the mechanical response due to hydrogen was observed regardless of the sample geometry and hydrogen changed the fracture mode from ductile to brittle. Moreover, hydrogen affected the fracture locus of TWIP steel by lowering the equivalent failure strains at given stress triaxiality levels. In this study, a modified Johnson-Cook failure mode was proposed and effect of hydrogen on damage constants were quantified. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
The Effect of Strain Rate on the Hydrogen Embrittlement Susceptibility of Aluminum 7075
(ASME, 2023) Baltacioglu, Mehmet Furkan; Bal, Burak; Cetin, Baris; 0000-0002-7389-9155; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Baltacioglu, Mehmet Furkan; Bal, Burak
The effects of changing the strain rate regime from quasi-static to medium on hydrogen susceptibility of aluminum (Al) 7075 were investigated using tensile tests. Strain rates were selected as 1 s(-1) and 10(-3) s(-1) and tensile tests were conducted on both hydrogen uncharged and hydrogen charged specimens at room temperature. Electrochemical hydrogen charging method was utilized and the diffusion length of hydrogen inside Al 7075 was modeled. Material characterizations were carried out by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) and microstructural observations of hydrogen uncharged and hydrogen charged specimens were performed by scanning electron microscope (SEM). As opposed to earlier studies, hydrogen embrittlement (HE) was more pronounced at high strain rate cases. Moreover, hydrogen enhanced localized plasticity (HELP) was the more dominant hydrogen embrittlement mechanism at slower strain rate but coexistence of hydrogen enhanced localized plasticity and hydrogen enhanced decohesion was observed at a medium strain rate. Overall, the current findings shed light on the complicated hydrogen embrittlement behavior of Al 7075 and constitute an efficient guideline for the usage of Al 7075 that can be subject to different strain rate loadings in service.
Hydrogen susceptibility of Al 5083 under ultra-high strain rate ballistic loading
(Walter de Gruyter GmbH, 2024) Baltacioglu, Mehmet Furkan; Mozafari, Farzin; Aydin, Murat; Cetin, Baris; Oktan, Aynur Didem; Teoman, Atanur; Li, Yang; Bal, Burak; 0000-0001-8218-4410; 0000-0002-7389-9155; 0000-0001-6476-0429; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Baltacioglu, Mehmet Furkan; Mozafari, Farzin; Bal, Burak
The effect of hydrogen on the ballistic performance of aluminum (Al) 5083H131 was examined both experimentally and numerically in this study. Ballistics tests were conducted at a 30° obliquity in accordance with the ballistic test standard MIL-DTL-46027 K. The strike velocities of projectiles were ranged from 240 m s−1 to 500 m s−1 level in the room temperature. Electrochemical hydrogen charging method was utilized to introduce hydrogen into material. Chemical composition of material was analyzed using energy dispersive X-ray (EDX) analysis. Instant camera pictures were captured using high-speed camera to compare H-uncharged and H-charged specimen ballistics tests. The volume loss in partially penetrated specimens were assessed using the 3D laser scanning method. Microstructural examinations were conducted utilizing scanning electron microscopy (SEM). It was observed that with the increased deformation rate, the dominance of the HEDE mechanism over HELP became evident. Furthermore, the experimental findings were corroborated through numerical methods employing finite element analysis (FEM) along with the Johnson–Cook plasticity model and failure criteria. Inverse optimization technique was employed to implement and fine-tune the Johnson–Cook parameters for H-charged conditions. Upon comparing the experimental and numerical outcomes, a high degree of consistency was observed, indicating the effective performance of the model.