Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 40Citation - Scopus: 43The Role of Hydrogen in the Edge Dislocation Mobility and Grain Boundary-Dislocation Interaction in Α-Fe(Pergamon-Elsevier Science Ltd, 2021-09) Kapci, Mehmet Fazil; Schoen, J. Christian; Bal, Burak; Schön, J. ChristianThe atomistic mechanisms of dislocation mobility depending on the presence of hydrogen were investigated for two edge dislocation systems that are active in the plasticity of alpha-Fe, specifically 1/2<111>{110} and 1/2<111>{112}. In particular, the glide of the dislocation pile-ups through a single crystal, as well as transmission of the pile-ups across the grain boundary were evaluated in bcc iron crystals that contain hydrogen concentrations in different amounts. Additionally, the uniaxial tensile response under a constant strain rate was analyzed for the aforementioned structures. The results reveal that the presence of hydrogen decreases the velocity of the dislocations -in contrast to the commonly invoked HELP (Hydrogen-enhanced localized plasticity) mechanism-, although some localization was observed near the grain boundary where dislocations were pinned by elastic stress fields. In the presence of pre-exisiting dislocations, hydrogen-induced hardening was observed as a consequence of the restriction of the dislocation mobility under uniaxial tension. Furthermore, it was observed that hydrogen accumulation in the grain boundary suppresses the formation of new grains that leads to a hardening response in the stress-strain behaviour which can initiate brittle fracture points. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Article Citation - WoS: 13Citation - Scopus: 14The Effect of Strain Rate on the Hydrogen Embrittlement Susceptibility of Aluminum 7075(ASME, 2022-11-22) Baltacioglu, Mehmet Furkan; Cetin, Baris; Bal, BurakThe 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.Book Part Citation - Scopus: 2Potential Effects of Short-Range Order on Hydrogen Embrittlement of Stable Austenitic Steels—A Review(Springer Science and Business Media Deutschland GmbH, 2021) Koyama, Motomichi; Bal, Burak; Canadinc, Demircan; Habib, Kishan; Tsuchiyama, Toshihiro; Tsuzaki, Kaneaki; Akiyama, EijiHere, we present a review of the hydrogen embrittlement behavior of face-centered cubic (FCC) alloys with short-range order (SRO) of solute atoms. In this paper, three types of FCC alloys are introduced: Fe–Mn–C austenitic steels, high-nitrogen steels, and CoCrFeMnNi high-entropy alloys. The Fe–Mn–C austenitic steels show dynamic strain aging associated with Mn–C SRO, which causes deformation localization and acceleration of premature fracture even without hydrogen effects. The disadvantageous effect of dynamic strain aging on ductility, which is associated with the deformation localization, amplify plasticity-assisted hydrogen embrittlement. Cr–N and Co–Cr–Ni SRO effects in high-nitrogen austenitic steels and high-entropy alloys enhance the dislocation planarity, which causes stress concentration in the grain interior and near the grain boundaries. The stress concentration coupled with hydrogen effects causes quasi-cleavage and intergranular fractures. © 2021 Elsevier B.V., All rights reserved.Conference Object Parameter Analysis of a Biomass Based SOFC-Engine Polygeneration System for Cooling, Heating and Power Production(Scanditale AB, 2020) Zhu, Pengfei; Guo, Leilei; Yao, Jing; Ren, Jianwei; Kapci, Mehmet Fazil; Bal, Burak; Zhang, Z. X.In order to meet the demand of clean and efficient energy conversion technology, a novel combined cooling, heating and power (CCHP) system fueled by biomass is proposed. This system is consists of biomass gasification unit, solid oxide fuel cell, IC engine unit and absorption refrigeration chiller. Thermodynamic model of the CCHP system are developed and then parameter analysis is adopted to optimize the performance of this system. The effect of air equivalent ratio (ER), steam biomass ratio (S/B) and the fuel utilization factor of SOFC (μ) on the performance of the entire system are studied. The results show that increase of S/B and μ will prompt the electrical efficiency, while the increase of ER has a negative effect on electrical efficiency. The exergy analysis shows that the exergy destruction of biomass gasification process and engine is larger, which is 454.5 kW and 207.2 kW respectively. On the contrary, exergy destruction of SOFC and absorption refrigeration chiller are 15.9 kW and 52.8 kW, respectively. © 2024 Elsevier B.V., All rights reserved.Article Citation - WoS: 11Citation - Scopus: 13On the Detailed Mechanical Response Investigation of PHBV/PCL and PHBV/PLGA Electrospun Mats(IOP Publishing Ltd, 2019-03-29) Bal, Burak; Tugluca, Ibrahim Burkay; Koc, Nuray; Isoglu, Ismail AlperIn this study, electrospun mats of pristine poly(epsilon-caprolactone) (PCL), Poly(D, L-lactide-co-glycolide) (PLGA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), as well as PHBV/PCL blends and PHBV/PLGA blends in different ratios (80:20, 75:25, 50:50, 25:75, 20:80, 10:90, 5:95%, w/w) and Centella Asiatica (CA) loaded (1, 5, 10%, w/v) PHBV/PCL and PHBV/PLGA polyester blends were prepared. Electrospun mats were characterized by scanning electron microscopy (SEM) in order to show uniform and bead and defect-free fiber structure with average diameter. The blend ratio and strain rate dependencies of mechanical behavior of these electrospun membranes were investigated under tensile loading. The tensile tests were conducted at an initial strain rates of 10(-1) s(-1), 10(-2) s(-1), 10(-3) s(-1) and 10(-4) s(-1) at room temperature and the best and worst combinations of PHBV/PLGA, PHBV/PCL blend ratios for both stress and ductility required applications were specified for each strain rate. The effects of blend ratios on the tensile strength and Young's modulus were also investigated. Moreover, the effects of Centella Asiatica on the electrospun membranes' mechanical behavior were demonstrated at different strain rates. Consequently, this study constitutes an important guideline for the selection and usage of the aforementioned electrospun membranes as a wound dressing material in terms of mechanical response at different loading scenarios.Article Citation - WoS: 14Citation - Scopus: 16Lowering Strain Rate Simultaneously Enhances Carbon- and Hydrogen-Induced Mechanical Degradation in an Fe-33Mn Steel(Springer, 2019-01-02) Tugluca, Ibrahim Burkay; Koyama, Motomichi; Shimomura, Yusaku; Bal, Burak; Canadinc, Demircan; Akiyama, Eiji; Tsuzaki, KaneakiWe investigated the strain rate dependency of the hydrogen-induced mechanical degradation of Fe-33Mn-1.1C steel at 303K within the strain rate range of 10(-2) to 10(-5)s(-1). In the presence of hydrogen, lowering the strain rate monotonically decreased the work hardening rate, elongation, and tensile strength and increased the yield strength. Lowering the strain rate simultaneously enhanced the plasticity-related effects of hydrogen and carbon, leading to the observed degradation of the ductility.Article Citation - WoS: 3Citation - Scopus: 3Investigations of Strain Rate, Size, and Crack Length Effects on the Mechanical Response of Polycaprolactone Electrospun Membranes(Sage Publications Ltd, 2021-06-18) Bayram, Ferdi C.; Kapci, Mehmet F.; Yuruk, Adile; Isoglu, Ismail A.; Bal, BurakThe effects of strain rate, size (height x width), and pre-existing crack length on the mechanical response of polycaprolactone electrospun membranes were investigated by tension tests conducted at room temperature. In particular, tensile tests were performed with three different strain rates for strain rate effect tests, seven different geometries for elucidating the size effect, and three different initial notch lengths for crack growth experiments. The electrospun membranes were produced by the electrospinning technique using a polycaprolactone solution prepared in 1, 1, 1, 3, 3, 3-hexafluoro-2-propanol as the solvent. Scanning electron microscopy was utilized to show the continuous fiber structure without bead formation. The average fiber diameter was calculated as 1.113 +/- 0.270 mu m by using scanning electron microscopy images of the membranes. The chemical structure of polycaprolactone was analyzed by Fourier transform infrared spectroscopy, and the toxicity and cell viability of the electrospun membranes were shown by CellTiter 96(R) Aqueous One Solution Cell Proliferation Assay (MTS test). It was observed that the ultimate tensile strength and Young's modulus decreased, and the elongation at failure value increased as the strain rate decreased from 10(-1) to 10(-3) s(-1). Besides, positive strain rate sensitivity was observed on the mechanical response of electrospun polycaprolactone membranes. Moreover, the dependency of mechanical response on the size geometry has been well studied, and the optimum height and width combinations were specified. Also, crack growth was studied in terms of both macroscopic and microstructural deformation mechanisms and it is observed that individual fiber deformations and interactions are highly effective on the mechanical behavior and also propagation of the crack. Consequently, in this study, the size and strain rate effects and crack growth on the mechanical response of electrospun polycaprolactone membranes have been investigated extensively, and the results presented herein constitute an essential guideline for the usage of polycaprolactone electrospun membranes at different loading scenarios.Conference Object Investigation of Temperature and Pressure Effect on the Hydrogen Sorption Kinetics in the Interface of Mg/MgH2 by Molecular Dynamics(International Association for Hydrogen Energy, IAHE, 2022) Kapci, Mehmet Fazil; Wu, Zhen; Bal, BurakMolecular dynamics simulations were performed in order to analyze the hydrogen sorption kinetics between αMgH<inf>2</inf> and hcp Mg structures under different temperatures and pressures. Results showed that hydrogen desorption from magnesium hydride and absorption by hcp magnesium increase at the higher temperatures. During the hydrogen desorption from magnesium hydride and absorption into hcp magnesium, crystallographic orientation change in the magnesium atoms was observed. At 400 °C, the pressure was found to have a negative impact during the hydrogen desorption from magnesium hydride due to the prevention of recrystallization. © 2023 Elsevier B.V., All rights reserved.Article Hydrogen Susceptibility of Al 5083 Under Ultra-High Strain Rate Ballistic Loading(Walter de Gruyter Gmbh, 2024-09-25) Baltacioglu, Mehmet Furkan; Mozafari, Farzin; Aydin, Murat; Cetin, Baris; Oktan, Aynur Didem; Teoman, Atanur; Bal, BurakThe 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 degrees 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.Article Citation - WoS: 21Citation - Scopus: 27High-Concentration Carbon Assists Plasticity-Driven Hydrogen Embrittlement in a Fe-High Mn Steel With a Relatively High Stacking Fault Energy(Elsevier Science SA, 2018-02) Tugluca, Ibrahim Burkay; Koyama, Motomichi; Bal, Burak; Canadinc, Demircan; Akiyama, Eiji; Tsuzaki, KaneakiWe investigated the effects of electrochemical hydrogen charging on the mechanical properties of a Fe-33Mn-1.1C austenitic steel with high carbon concentration and relatively high stacking fault energy. Hydrogen pre charging increased the yield strength and degraded the elongation and work-hardening capability. The increase in yield strength is a result of the solution hardening of hydrogen. A reduction in the cross-sectional area by subcrack formation is the primary factor causing reduction in work-hardening ability. Fracture modes were detected to be both intergranular and transgranular regionally. Neither intergranular nor transgranular cracking modes are related to deformation twinning or simple decohesion in contrast to conventional Fe-Mn-C twinning induced plasticity steels. The hydrogen-assisted crack initiation and subsequent propagation are attributed to plasticity-dominated mechanisms associated with strain localization. The occurrence of dynamic strain aging by the high carbon content and ease of cross slip owing to the high stacking fault energy can cause strain/damage localization, which assists hydrogen embrittlement associated with the hydrogen-enhanced localized plasticity mechanism.
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