WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394

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Now showing 1 - 8 of 8
  • Article
    Tuning Mechanical Performance of PCL Scaffolds: Influence of 3D Bioprinting Parameters, Polymer Concentration, and Solvent Selection
    (IOP Publishing Ltd, 2025-09-01) Ceylan, Saniye Aylin; Baltacioglu, Mehmet Furkan; Bal, Burak; Bayram, Ferdi Caner; Isoglu, Ismail Alper
    The mechanical performance of three-dimensional (3D) bioprinted scaffolds is susceptible to printing parameters and material formulation. In this study, poly (epsilon-caprolactone) (PCL) scaffolds were fabricated using four different polymer concentrations (10%, 25%, 50%, and 75% w/v) to investigate how these variations, along with process parameters, influence mechanical behavior. Maintaining the structural integrity of bioprinted constructs requires careful optimization of polymer concentration and precise control over parameters such as printing speed, pressure, and infill density. Tensile tests were conducted to evaluate the effects of these variables. Among the tested conditions, a 50% (w/v) concentration allowed for a broader operational window, enabling fabrication across a range of printing speeds and pressures. At a printing speed of 5 mm s-1, PCL-DCM exhibited a Young's modulus of 39.0 MPa, while PCL-CF samples printed at 10 mm s-1 achieved the highest modulus of 32.0 MPa. Notably, when the printing speed was kept constant, applying higher pressures led to an increase in Young's modulus, suggesting that pressure plays a key role in enhancing scaffold stiffness. When comparing the 50% and 75% (w/v) polymer concentrations, the 50% (w/v) formulation stood out by offering both higher elongation and greater stiffness, which makes it particularly suitable for load-bearing applications. These findings provide a quantitative framework for optimizing extrusion-based bioprinting of PCL scaffolds, with implications for customized biomedical implants and regenerative medicine.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Prediction of the Diffusible Hydrogen Concentration After Electrochemical Charging Utilizing Artificial Intelligence
    (IOP Publishing Ltd, 2025-09-01) Sivesoglu, Abdurrahman; Li, Yang; Bal, Burak
    The concentration of diffusible hydrogen in a material is of high importance as it helps to predict the hydrogen embrittlement effect in the material, and the amount of mechanical properties' degradation after reaching a critical concentration. Despite that, a simple experimental setup is not available to measure hydrogen concentration at service. In this paper, a multi-layer perceptron (MLP) model is developed using weight initialization, which can estimate the diffusible hydrogen concentration of Face-Centred-Cubic (FCC) metals after electrochemical charging. The input properties of the model include the electrochemical charging parameters of current density, temperature, and charging time as well as the grain size of the specimen. The MLP model with and without the weight initialization was validated and tested with unseen test dataset. The model in both cases showed an excellent predictive performance with a higher accuracy and faster convergence when using weight initialization. A linear correlation of 89% between the experimental and predicted hydrogen concentration was observed. This demonstrates that for the family of FCC metals under electrochemical charging, the estimation of diffusible hydrogen concentration is a feasible path for material safety design analysis.
  • Article
    Citation - WoS: 13
    Citation - Scopus: 14
    The Effect of Strain Rate on the Hydrogen Embrittlement Susceptibility of Aluminum 7075
    (ASME, 2022-11-22) Baltacioglu, Mehmet Furkan; Cetin, Baris; 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.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 13
    On 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 Alper
    In 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: 2
    Citation - Scopus: 3
    Investigation of Hydrogen Diffusion Profile of Different Metallic Materials for a Better Understanding of Hydrogen Embrittlement
    (Gazi Univ, 2023-12-01) Kapci, Mehmet Fazil; Bal, Burak
    In this study, hydrogen diffusion profiles of different metallic materials were investigated. To model hydrogen diffusion, 1D and 2D mass diffusion models were prepared in MATLAB. Iron, nickel and titanium were selected as a material of choice to represent body-centered cubic, facecentered cubic, and hexagonal closed paced crystal structures, respectively. In addition, hydrogen back diffusion profiles were also modeled after certain baking times. Current results reveal that hydrogen diffusion depth depends on the microstructure, energy barrier model, temperature, and charging time. In addition, baking can help for back diffusion of hydrogen and can be utilized as hydrogen embrittlement prevention method. Since hydrogen diffusion is very crucial step to understand and evaluate hydrogen embrittlement, current set of results constitutes an important guideline for hydrogen diffusion calculations and ideal baking time for hydrogen back diffusion for different materials. Furthermore, these results can be used to evaluate hydrogen content inside the material over expensive and hard to find experimental facilities such as, thermal desorption spectroscopy.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 7
    Experimental and Molecular Dynamics Simulation-Based Investigations on Hydrogen Embrittlement Behavior of Chromium Electroplated 4340 Steel
    (ASME, 2021-06-17) Dogan, Ozge; Kapci, Mehmet Fazil; Esat, Volkan; Bal, Burak
    In this study, chromium electroplating process, corresponding hydrogen embrittlement, and the effects of baking on hydrogen diffusion are investigated. Three types of materials in the form of Raw 4340 steel, Chromium electroplated 4340 steel, and Chromium electroplated and baked 4340 steel are used in order to shed light on the aforementioned processes. Mechanical and microstructural analyses are carried out to observe the effects of hydrogen diffusion. Mechanical analyses show that the tensile strength and hardness of the specimens deteriorate after the chrome-electroplating process due to the presence of atomic hydrogen. X-ray diffraction (XRD) analyses are carried out for material characterization. Microstructural analyses reveal that hydrogen enters into the material with chromium electroplating process, and baking after chromium electroplating process is an effective way to prevent hydrogen embrittlement. Additionally, the effects of hydrogen on the tensile response of alpha-Fe-based microstructure with a similar chemical composition of alloying elements are simulated through molecular dynamics (MD) method.
  • Article
    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 - Society of Photo-Optical Instrumentation Engineers, 2021-10-27) Durkaya, Goksel; Kurtuldu, Huseyin; Cetin, Baris; 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)
  • Article
    Citation - WoS: 9
    Citation - Scopus: 12
    A Study of Different Microstructural Effects on the Strain Hardening Behavior of Hadfield Steel
    (Korean Soc Steel Construction-KSSC, 2018-03) Bal, Burak
    The effects of the initial texture, velocity gradient, strain increment and type of interaction tensor on the strain hardening response of Hadfield steel were investigated. To observe their influences on mechanical response, crystal plasticity computations were carried out with the aid of the Visco-Plastic Self-Consistent (VPSC) algorithm. Specifically, uniaxial deformation response of Hadfield steel was modeled based on the experimental deformation response at a strain rate of 1x10(-1) s(-1) and corresponding Voce hardening parameters were calculated. The same Voce hardening parameters were utilized with different boundary conditions in the VPSC simulations to identify the roles of the aforementioned microstructural properties. The current results demonstrate the importance of these microstructural properties for reliable predictions of the strain hardening response of Hadfield steel and constitute an important guideline for the proper selection of them.