Browsing by Author "Bal, B."

Now showing 1 - 8 of 8

Citation - WoS: 9
Citation - Scopus: 12
The Precise Determination of the Johnson-Cook Material and Damage Model Parameters and Mechanical Properties of an Aluminum 7068-T651 Alloy
(ASME, 2019) Bal, B.; Karaveli, K. K.; Cetin, B.; Gumus, B.
Al 7068-T651 alloy is one of the recently developed materials used mostly in the defense industry due to its high strength, toughness, and low weight compared to steels. The aim of this study is to identify the Johnson-Cook (J-C) material model parameters, the accurate Johnson-Cook (J-C) damage parameters, D-1, D-2, and D-3 of the Al 7068-T651 alloy for finite element analysis-based simulation techniques, together with other damage parameters, D-4 and D-5. In order to determine D-1, D-2, and D-3, tensile tests were conducted on notched and smooth specimens at medium strain rate, 10(0) s(-1), and tests were repeated seven times to ensure the consistency of the results both in the rolling direction and perpendicular to the rolling direction. To determine D-4 and D-5 further, tensile tests were conducted on specimens at high strain rate (10(2) s(-1)) and temperature (300 degrees C) by means of the Gleeble thermal-mechanical physical simulation system. The final areas of fractured specimens were calculated through optical microscopy. The effects of stress triaxiality factor, rolling direction, strain rate, and temperature on the mechanical properties of the Al 7068-T651 alloy were also investigated. Damage parameters were calculated via the Levenberg-Marquardt optimization method. From all the aforementioned experimental work, J-C material model parameters were determined. In this article, J-C damage model constants, based on maximum and minimum equivalent strain values, were also reported which can be utilized for the simulation of different applications.
Citation - WoS: 33
Citation - Scopus: 38
Fracture Behavior of Novel Biomedical Ti-Based High Entropy Alloys Under Impact Loading
(Elsevier Science SA, 2021) Gurel, S.; Yagci, M. B.; Canadinc, D.; Gerstein, G.; Bal, B.; Maier, H. J.
This paper focuses on the mechanical properties and fracture behavior of newly developed body-centered-cubic structured TiTaHfNb, TiTaHfNbZr and TiTaHfMoZr high entropy alloys (HEAs) under impact loading as part of an effort to evaluate their potential utility as implant materials. The experimental findings showed all three Ti based HEAs have lower Young's modulus as compared to the conventionally used implant materials. Fractography analysis revealed that the TiTaHfNb HEA demonstrated significant ductility with the highest energy absorption capacity, while the TiTaHfNbZr and the TiTaHfMoZr alloys exhibited mixed mode fracture with relatively low ductility. Specifically, the reduction of ductility and energy absorption capacity under impact loading was attributed to the addition of Zr and Mo into Ti-based HEA system, which facilitates formation of additional dislocations in the microstructure due to increased lattice distortion. The current findings demonstrate that, from a mechanical point of view, the TiTaHfNb HEA could be considered as an alternative implant material for applications demanding high wear and corrosion resistance, such as hip or knee implants, and thus, warrant further investigation of the biomedical performance of this alloy.Y
Citation - WoS: 32
Citation - Scopus: 37
Assessment of Biocompatibility of Novel TiTaHf-Based High Entropy Alloys for Utility in Orthopedic Implants
(Elsevier Science SA, 2021) Gurel, S.; Nazarahari, A.; Canadinc, D.; Cabuk, H.; Bal, B.
This paper presents the findings of experimentally observed corrosion response of novel TiTaHf-based high entropy alloys (HEAs) in fetal bovine serum (FBS) to evaluate their biocompatibility in presence of proteins and potential to be used as implant materials. Particularly, TiTaHfNb, TiTaHfNbZr and TiTaHfMoZr HEAs were subjected to static immersion experiments in FBS media, and both the HEA samples and the immersion fluids underwent thorough characterization. The findings presented herein show that Zr and Mo addition to the TiTaHf solid solution increased the total ion release from the resulting HEAs in FBS, while the TiTaHfNb HEA became prominent in terms of biocompatibility owing to the reduced ion release in FBS. Moreover, hydroxy apatite (HA) formation was evident on the surfaces of all three HEAs upon immersion in FBS, indicating the potential of the three TiTaHf-based HEAs to form desired binding with the human bone. Considering the fact that passive oxide layer formation facilitating lower susceptibility to corrosion in long-term applications was also observed in the studied HEAs, further elaboration on their mechanical and biological responses is warranted for the sake of a comprehensive assessment regarding their utility as orthopedic implant materials.
Citation - WoS: 5
Citation - Scopus: 5
Experimental Investigation on Chloroprene and Acrylonitrile Butadiene Rubber Types Reinforced With Nano-Materials
(IOP Publishing Ltd, 2019) Dogan, O.; Esat, V.; Bal, B.
In this research, the effects of three different nano-materials (Nano-Carbon Black, Nano-ZnO, and Multi-Walled Carbon Nanotubes (MWNTs)) on two different rubber types (Chloroprene Rubber (CR), and Acrylonitrile Butadiene Rubber (NBR)) were experimentally investigated. In order to achieve this purpose, mechanical tests and detailed aging tests (in air, oil and fuel) were conducted conforming to international standards. Three different nano-materials were added to rubber with different combinations. A good dispersion of MWNTs within the polymer matrix was monitored by using field-emission Scanning Electron Microscopy (FE-SEM). It was observed that nano-materials both have positive and detrimental effects on hardness, tensile strength, ductility and aging tests performance. It was observed that nano-material reinforced rubber composites are thermally more stable than current products. Most significantly, it was seen that compression set value, which is a critical property for rubber grade, decreased with the addition of MWNTs. Therefore, rubber products with higher sealing capacity and longer service life can be obtained by adding MWNTs.
Citation - WoS: 118
Citation - Scopus: 142
Microstructure and Tribological Properties of TiTaHfNbZr High Entropy Alloy Coatings Deposited on Ti-6Al Substrates
(Elsevier Sci Ltd, 2019) Tuten, N.; Canadinc, D.; Motallebzadeh, A.; Bal, B.
We report on the microstructure and tribological behavior of equimolar TiTaHfNbZr high entropy alloy (HEA) thin films deposited on the biomedical Ti-6Al-4V substrates by RF magnetron sputtering. Results of nanoindentation and sliding wear experiments were evaluated along with the microstructure and topographical information obtained from scanning electron microscopy and atomic force microscopy. The findings clearly demonstrate that the TiTaHfNbZr HEA not only forms a homogenous and dense coating mechanically compatible with the Ti-6Al-4V substrates, but also provides a significantly enhanced surface protection against wear and cracking, which could prove valuable especially in long-term orthopedic implants that bear dynamic contact loading, such as in the cases of hip or knee joints.
Citation - WoS: 3
Citation - Scopus: 4
On the Utility of Crystal Plasticity Modeling to Uncover the Individual Roles of Microdeformation Mechanisms on the Work Hardening Response of Fe-23Mn TWIP Steel in the Presence of Hydrogen
(ASME, 2018) Bal, B.; Koyama, M.; Canadinc, D.; Gerstein, G.; Maier, H. J.; Tsuzaki, K.
This paper presents a combined experimental and theoretical analysis focusing on the individual roles of microdeformation mechanisms that are simultaneously active during the deformation of twinning-induced plasticity (TWIP) steels in the presence of hydrogen. Deformation responses of hydrogen-free and hydrogen-charged TWIP steels were examined with the aid of thorough electron microscopy. Specifically, hydrogen charging promoted twinning over slip-twin interactions and reduced ductility. Based on the experimental findings, a mechanism-based microscale fracture model was proposed, and incorporated into a visco-plastic self-consistent (VPSC) model to account for the stress-strain response in the presence of hydrogen. In addition, slip-twin and slip-grain boundary interactions in TWIP steels were also incorporated into VPSC, in order to capture the deformation response of the material in the presence of hydrogen. The simulation results not only verify the success of the proposed hydrogen embrittlement (HE) mechanism for TWIP steels, but also open a venue for the utility of these superior materials in the presence of hydrogen.
Citation - WoS: 50
Citation - Scopus: 58
Corrosion Behavior of Novel Titanium-Based High Entropy Alloys Designed for Medical Implants
(Elsevier Science SA, 2020) Gurel, S.; Yagci, M. B.; Bal, B.; Canadinc, D.
This paper reports on the corrosion behavior of three TiTaHf-based high entropy alloys (HEAs) in simulated body fluid (SBF) and artificial saliva (AS) in order to assess their potential utility as implant materials. Specifically, TiTaHfNb, TiTaHfNbZr and TiTaHfMoZr HEAs were subjected to static immersion experiments in SBF and AS, and both the surfaces of the samples and the immersion fluids were thoroughly examined with the state of the art techniques. The experimental results presented herein revealed that the presence of Zr and Nb in the TiTaHf-based samples enhanced corrosion performance with reduced ion release and better surface properties, while Mo addition resulted in an inhomogeneous microstructure, leading to dendrite structures and significant amount of ion release upon immersion in both media. Furthermore, a protective passive layer formation or crystallization was present on all HEA surfaces, implying that corrosion resistance can be sustained in long-term applications. Overall, the set of findings presented herein constitute an early indication of the potential of the TiTaHf-based HEAs to be utilized as implant materials.
Citation - WoS: 99
Citation - Scopus: 108
Effect of Strain Rate on Hydrogen Embrittlement Susceptibility of Twinning-Induced Plasticity Steel Pre-Charged With High-Pressure Hydrogen Gas
(Pergamon-Elsevier Science Ltd, 2016) Bal, B.; Koyama, M.; Gerstein, G.; Maier, H. J.; Tsuzaki, K.
The effects of tensile strain rate on the hydrogen-induced mechanical and microstructural features of a twinning-induced plasticity (TWIP) steel were investigated using a Fe-23Mn-0.5C steel with a saturated amount of hydrogen. To obtain a homogeneous hydrogen distribution, high-pressure hydrogen gas pre-charging was performed at 423 K. Similar to previous studies on hydrogen embrittlement, the deterioration in the tensile properties became distinct when the strain rate was decreased from 0.6 x 10(-3) to 0.6 x 10(-4) s(-1). In terms of microstructural features, hydrogen-precharging decreased the thickness of deformation twin plates, and it localized dislocation slip. Moreover, facets of the hydrogen induced quasi-cleavage feature on the fracture surface became smoother with decreasing strain rate. In this study, we proposed that a combined effect of hydrogen segregation, slip localization, and thinning of twin plates causes the hydrogen embrittlement of TWIP steels, particularly at a low strain rate. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.