Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 2Citation - Scopus: 2Numerical Investigation of the Role of Volumetric Transformation Strain on the Relaxation Stress and the Corresponding Hydrogen Interstitial Concentration in Niobium Matrix(Hindawi Ltd, 2017) Bal, BurakThe effects of relaxation stress on the hydrogen concentration in Niobium-(Nb-) H media were investigated by iterative numerical modeling approach. To calculate the transformation strain, relaxation stress, and corresponding relaxed hydrogen concentration around an edge dislocation, a new third-order polynomial formulation was utilized in the model. With the aid of this polynomial, hydrogen induced relaxation stress never exceeds the dislocation stress, which indicates that the total stress field never turns to compressive state and diverges the results. The current model calculates the hydrogen concentration not only in the vicinity of an edge dislocation but also far away from the dislocation. Furthermore, the effect of relaxation stress on the interaction energy was also captured in the model. Overall, the current findings shed light on the complicated hydrogen embrittlement mechanisms of metallic materials by demonstrating that hydrogen induced relaxation has a significant effect on the hydrogen atom concentration and the interaction energy between the existing internal stress field and the solute hydrogen atom.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: 14Citation - Scopus: 15Lateral Angular Co-Extrusion: Geometrical and Mechanical Properties of Compound Profiles(MDPI, 2020-08-28) Thuerer, Susanne Elisabeth; Peddinghaus, Julius; Heimes, Norman; Bayram, Ferdi Caner; Bal, Burak; Uhe, Johanna; Klose, Christian; Thürer, Susanne ElisabethA novel co-extrusion process for the production of coaxially reinforced hollow profiles has been developed. Using this process, hybrid hollow profiles made of the aluminum alloy EN AW-6082 and the case-hardening steel 20MnCr5 (AISI 5120) were produced, which can be forged into hybrid bearing bushings by subsequent die forging. For the purpose of co-extrusion, a modular tooling concept was developed where steel tubes made of 20MnCr5 are fed laterally into the tool. This LACE (lateral angular co-extrusion) process allows for a variation of the volume fraction of the reinforcement by using steel tubes with different wall thicknesses, which enabled the production of compound profiles having reinforcement contents of either 14 vol.% or 34 vol.%. The shear strength of the bonding area of these samples was determined in push-out tests. Additionally, mechanical testing of segments of the hybrid profiles using shear compression tests was employed to provide information about the influence of different bonding mechanisms on the strength of the composite zone.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.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: 4Citation - Scopus: 6Functional Surfaces of the Future: Integrating Texturing and Coatings for Superior Performance(Elsevier Sci Ltd, 2025-09) Yuan, Yanjie; Louhichi, Borhen; Heidarshenas, Behzad; Alrasheedi, Nashmi H.; Bal, Burak; Hussain, GhulamCurrent surface texturing and coating methods exhibit performance improvements but face significant limitations, including inconsistent durability, scalability restrictions, and inadequate integration of their properties. Integrating these approaches can effectively address these challenges. Modern methods, such as laser machining and additive manufacturing, are paving the way for mainstream applications, offering the opportunity to develop new high-performance surfaces in various fields. For instance, combining laser texturing and advanced coating can address durability issues by developing precise patterns and strong adhesion. The combination of surface texturing and coating improves tribological performance and enhances service maintenance by overcoming the limitations of conventional methods. This offers advanced capabilities for various applications, including medical implants and marine environments. In this context, the synergistic application of texturing and coating technologies is expected to be crucial in developing high-performing advanced materials suitable for various applications. This study reviews the progress on synchronizing texturing and coating approaches. Governing mechanisms and controlling factors are identified and discussed. The benefits of applying synergetic approaches to surface performance are recorded. Optimum conditions to realize the best results are determined. Current challenges, emerging trends, and potential solutions to address these issues are proposed.Article Citation - WoS: 4Citation - Scopus: 5Effect of Pre-Rolling Temperature on the Interfacial Properties and Formability of Steel-Steel Bilayer Sheet in Single Point Incremental Forming(Sage Publications Ltd, 2020-10-14) Hassan, Malik; Hussain, Ghulam; Ali, Aaqib; Ilyas, Muhammad; Malik, Sohail; Khan, Wasim A.; Bal, BurakThe aim of this research was to investigate the effect of pre-rolling temperature on the interfacial properties in delamination modes 1 and 2; and formability in Single Point Incremental Forming (SPIF) of Steel-Steel (St-St) bilayer sheet prepared by roll bonding process. The roll bonding process was performed at three pre-rolling temperatures, 700 degrees C, 800 degrees C, and 950 degrees C, with a constant thickness reduction ratio of 58%. The bond strength and critical strain energy release rate (CSERR) were measured to characterize the interface of St-St bilayer sheet. T-peel test for mode 1 and tensile shear test for mode 2 were conducted to determine the interfacial properties. The formability of St-St bilayer sheet in SPIF was measured in terms of maximum wall angle. The results showed that the increase in pre-rolling temperature from 700 degrees C to 950 degrees C enhanced the bond strength and CSERR, in both mode 1 and 2. The enhancement in bond strength with an increase in pre-rolling temperature was 149.5% and 203% in mode 1 and 2, respectively. However, the increase in CSERR in mode 1 and 2 was 115% and 367%, respectively. The formability of St-St bilayer sheet also showed an increasing trend with an increase in pre-rolling temperature. Moreover, a consistent relation between formability and interfacial parameters was observed. It was also found that to successively deform the bilayer sheet into the desired shape, it is necessary for the sheet to be heated above the critical temperature during fabrication to facilitate good bonding between two sheets.Article Comprehensive Optimization of Shot Peening Intensity Using a Hybrid Model With AI-Based Techniques via Almen Tests(Walter de Gruyter Gmbh, 2025-06-03) Karaveli, Kadir Kaan; Bal, BurakShot peening is a crucial surface treatment technique that significantly improves the mechanical properties of metallic components, particularly their fatigue resistance and ability to withstand corrosion cracking. This study aims to optimize the shot peening process for aviation applications by evaluating and comparing various mathematical modeling and optimization techniques. Seven mathematical models were analyzed using a neuro-regression method (NRM), among which the second-order trigonometric non-linear (SOTN) model exhibited the highest reliability, achieving R2 values of 0.93 and 0.90 for training and testing datasets, respectively. To improve the model's robustness, four optimization algorithms - differential evolution (DE), simulated annealing (SA), Nelder-Mead (NM), and random search (RS) - were applied to the SOTN model. Although each technique offered valuable insights, performance fluctuations across different intensity ranges necessitated the development of a hybrid optimization model that combines the strengths of all four methods. The hybrid model achieved a mean error of approximately 2.69 %, outperforming individual approaches and demonstrating strong potential for reliable shot peening optimization across a wide range of target intensities. These findings provide a comprehensive methodology for AI-based optimization of surface treatment processes in engineering applications.