Mechanical, Wear and Thermal Behaviors of Graphene Reinforced Titanium Composites

Mevlüt Gürbüz,Tuğba Mutuk,Pınar Uyan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.4

In this study, the effects of graphene content (0.15, 0.30, 0.45 and 0.60 wt%) on the mechanical, tribological and thermalproperties of titanium matrix composites were investigated. The experimental results showed that the highest ultimatecompressive strength (845 MPa), tensile strength (613 MPa), lowest mass loss (0.6 mg for 10 N), and lowest wear rate(WR = 286 × 10−5 mm3/Nm for10 N) were obtained for Ti-0.15GNPs compared with pure titanium (652 MPa, 413 MPa,1 mg and 5 × 10−5 mm3/Nm, respectively). The wear rate of composites deteriorates with increasing applied load. Fromthe thermal analysis results, the best thermal conductivity (16 W/mK) and diffusivity (7.1 mm2/s) were performed for Ti-0.30GNPs composites at room temperature. The thermal behavior of the composites was decreased with increasing graphenecontent and temperature. It concluded that graphene is an effective reinforcement to develop the mechanical, wear and thermalbehavior of titanium matrix composites.

Numerical Evaluation on the Steel Plate Shear Wall Design Parameters for Improved Cyclic Behavior

Muhammed Gürbüz,İlker Kazaz 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.2

In previous studies, the relationship between the collapse behavior of steel plate shear walls (SPSW) and the design parameters beyond the design drift limits is not addressed in the same framework. In this study, the eff ects of design parameters, such as the column fl exibility parameter, axial load level on boundary columns, column-to-beam stiff ness ratio, plate thickness and plate aspect ratio, on the deformation capacity and failure modes of steel plate shear walls are investigated in a parametric study using the fi nite element models of three-story SPSWs with rigid beam-column connections (moment-resisting frames). Models are analyzed under monotonic and cyclic loading. The ranges of parameters in combination leading to poor, moderate and improved displacement capacity, failure mechanism and energy dissipation capacity of SPSWs are identifi ed. A formula is developed to estimate the ultimate drift ratio of SPSWs using design parameters. The infi ll plate-frame interaction is investigated and it is determined that 25% of the total shear force resisted by the frame component is necessary for desired seismic behavior of SPSWs.

Sintering of 94Na0.5Bi0.5TiO3-6BaTiO3 with SPS and conventional methods for crystal growth

Mevlüt Gürbüz,Erhan Ayas,Aydin Dogan 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.1

In this study, lead-free 94Na0.5Bi0.5TiO3-6BaTiO3 (94NBT-6BT) piezoelectric ceramics and embedded single crystals inpolycrystalline 94NBT-6BT matrix were sintered by conventional (CS) and spark plasma sintering (SPS) techniques. Theeffects of SPS and CS on the microstructure of the 94NBT-6BT ceramics were discussed and compared. Theoretical densityof the CS and SPS treated samples were found to be 94% and almost 99.9%, respectively. High porosity and weak seed-matrixinteraction at 1180 oC for 2 h were obtained from CS sintered ceramics. On the other hand, sintered samples with SPS showednon-porous polycrystalline matrix, and quite strong seed-matrix interface bonding at 950 oC for 5 min. Also, dielectricproperties of sintered ceramics with SPS gave better results than CS. Therefore, SPS assisted 94NBT-6BT samples can be usedto grow high quality and high performance single crystals using solid state single crystal growth.

Tectonic Geomorphology of the North Anatolian Fault Zone in the Lake Sapanca Basin (Eastern Marmara Region, Turkey)

Alper Gürbüz,Ömer Feyzi Gürer 한국지질과학협의회 2008 Geosciences Journal Vol.12 No.3

In this study the spatial variations of the Plio-Quaternary tectonic activity and deformation of different fault segments of the North Anatolian Fault Zone (NAFZ) in the eastern Marmara region around Lake Sapanca, are assessed using geomorphic, morphometric and bathymetric approaches. Lake Sapanca is an E-W-trending structure located in the zmit-Sapanca Corridor. This region is bounded to the north and to the south by the series of mountain ranges. Geomorphic and morphometric data provide evidence for variations between the two mountain front faults regarding levels of tectonic activity. These studies suggest a relatively high degree of tectonic activity along the Sapanca front in the south, in contrast with a low degree of tectonic activity along the E me front in the north of the study area. This pattern is also consistent with field evidence and seismic data of the study area. Bathymetric profiles of the lake show that the lake basin consists of different fault segments that slipped in the 1999 Kocaeli earthquake. All these data suggest that the zmit-Sapanca Corridor is an asymmetric pull-apart basin associated with displacement along the NAFZ in the Late Pliocene. Lake Sapanca also occurs as a pull-apart basin created by the cross-basin fault of the asymmetric pull-apart basin in the Middle Pleistocene.

Foramen Magnum Decompression and Duraplasty is Superior to Only Foramen Magnum Decompression in Chiari Malformation Type 1 Associated with Syringomyelia in Adults

Mehmet Sabri Gürbüz,Mehmet Zafer Berkman,Emre Ünal,Elif Akpınar,Şevki Gök,Metin Orakdöğen,Salih Aydın 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.5

Study Design: Retrospective cohort study. Purpose: To compare surgical results of foramen magnum decompression with and without duraplasty in Chiari malformation type 1 (CM-1) associated syringomyelia (SM). Overview of Literature: The optimal surgical treatment of CM-1 associated with SM is unclear. Methods: Twenty-five cases of CM-1 with SM were included. There were 12 patients (48%) in the non-duraplasty group and 13 patients (52%) in the duraplasty group. The rate of improvement, state of postoperative SM size, amount of tonsillar herniation, preoperative symptom duration, complications and reoperation rates were analysed. Results: The rate of clinical improvement was significantly higher with duraplasty (84.6%) than without (33.3%, p <0.05). The rate of postoperative syrinx regression was significantly higher in the duraplasty group (84.6%) than in the non-duraplasty group (33.3%, p <0.05). One case in the duraplasty group needed a reoperation compared with five cases in the non-duraplasty group (p =0.059). Conclusions: Duraplasty is superior to non-duraplasty in CM-1 associated with SM despite a slightly higher complication rate.

Fully Endoscopic Interlaminar Detethering of Spinal Cord in Tethered Cord Syndrome: A Case Report and Technical Description

Mehmet Sabri Gürbüz,Salih Aydín,Deniz Bozdoğan 대한척추신경외과학회 2015 Neurospine Vol.12 No.4

A 19-year-old man presented with long lasting significant back and bilateral leg pain, and hypoesthesia on the lateral side of both his thighs for which he had undergone several courses of medication and bouts of physical therapy treatment. His urodynamic parameters were normal and lumbar magnetic resonance imaging (MRI) revealed a low-lying conus at the L2-3 level with a thickened fatty filum, and he was diagnosed as having tethered cord syndrome (TCS). The patient underwent a fully endoscopic detethering through an interlaminar approach with intraoperative neurophysiological monitoring. The thickened filum terminale was located and then the filum was coagulated and cut. The patient showed a significant improvement in his preoperative symptoms, and reported no problems at 2-year follow-up. Detethering of the spinal cord in tethered cord syndrome using a fully endoscopic interlaminar approach provides the advantages of minimal damage to tissues, less postoperative discomfort, early postoperative recovery, and a shorter hospitalization.

Application of unilateral rhomboid intercostal and subserratus plane block for analgesia after laparoscopic cholecystectomy: a quasi-experimental study

Ökmen Korgün,Gürbüz Hande,Özkan Hakan 대한마취통증의학회 2022 Korean Journal of Anesthesiology Vol.75 No.1

Background: Interfascial plane block can be used to treat postoperative pain after laparoscopic surgery. This study aimed to investigate the effect of ultrasound-guided unilateral rhomboid intercostal and subserratus plane (RISS) block after laparoscopic cholecystectomy on the amount of analgesic consumption.Methods: Fifty patients who underwent laparoscopic cholecystectomy were included in this quasi-experimental study. Patients fulfilling the inclusion criteria were analyzed in two groups: RISS group (RISS block with 20 ml of 0.25% bupivacaine + intravenous patient-controlled analgesia [IV-PCA] tramadol [n = 25]); and Control group (IV-PCA tramadol [n = 25]). The primary outcome was the total amount of tramadol used over 24 h. Secondary outcomes included side effects, additional analgesic use, and postoperative pain (at rest and during activity) at 2, 6, 12, and 24 h according to numerical rating scale (NRS) scores.Results: Postoperative tramadol consumption at 24 h was significantly lower in the RISS group than in the Control group (P < 0.001). Resting NRS scores at 2 h and 6 h were significantly lower in the RISS group. NRS scores during movement in the RISS group were significantly lower at 2, 6, and 12 h postoperatively. There was no statistically significant difference in the rate of side effects and additional analgesic use between the groups (P > 0.05). Conclusions: Unilateral RISS block was an effective method for pain management after laparoscopic cholecystectomy and can be used as a part of multimodal analgesia.

Investigation on Mechanical Properties and Microstructure of B4C/Graphene Binary Particles Reinforced Aluminum Hybrid Composites

Mahmut Can Şenel,Mevlüt Gürbüz 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

In the present study, boron carbide and graphene-reinforced aluminum hybrid composites with various boron carbide (1,3, 6, 9, 12, 15, 30 wt%) and graphene nanoplatelets (GNPs) content (0.15, 0.30, 0.45 wt%) were produced by the powdermetallurgy method. The method consists of mixing, ultrasonic dispersing, mixing, fltering, drying, pressing, and sinteringprocesses. The apparent density, compressive strength, and Vickers hardness of the fabricated composites were determined bydensity meter, universal test machine, and micro Vickers hardness measurement device, respectively. The phase and microstructural analysis of the fabricated composites were analyzed using an X-ray difraction device and scanning electron microscope, respectively. The maximum apparent density (2.54±0.005 g/cm3), the highest Vickers hardness (109.8±1.5 HV),the best compressive strength (244±5 MPa), and minimum porosity (4.0%) were obtained at Al-30%B4C-0.15%GNPscomposite. The enhancement in Vickers hardness and compressive strength of Al-30%B4C-0.15%GNPs composite wasdetected as +293% and +190% compared with pure aluminum. In conclusion, it was detected that the mechanical strengthof Al-30B4C-GNPs composites improved up to 0.15 wt%GNPs content. After 0.15 wt%graphene content, the mechanicalstrength of Al-30B4C-GNPs composites decreased due to the agglomerated graphene nanoparticles.

Braking performance and noise in excessive worn brake discs coated with HVOF thermal spray process

Ali Öz,Habib Gürbüz,Ali Kemal Yakut,Selami Sağiroğlu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2

In this paper, two excessive worn brake discs of a light commercial vehicle were coated with High velocity oxygen fuel (HVOF) thermal spray process for reuse. The coated discs were compared with uncoated Original equipment manufacturer (OEM) D1 disc in terms of braking performance and noise. The D2 disc was coated with tungsten-carbide-cobalt (88 %WC-12 %Co) powder and NiCr (80/20) binder, and 500 µm thick coating was obtained. The D3 disc was coated with Colmonoy-88 (Ni-W-Cr-B-Si) powder and NiCr (80/20) binder and 600 µm thick coating was obtained. Several test procedures (e.g. bedding, vibration, and structural-strength tests) was applied to three discs using inertia brake dynamometer. Results showed that coated D2 disc with tungsten carbide cobalt provided lower brake noise and higher brake performance compared with OEM disc. Considering the coefficient of friction and temperature, coated D3 disc has approximately equal braking performance with OEM D1 disc despite the high braking noise value.

Effect of MAP and Vacuum Sealing on Sensory Qualities of Drysalted Olive

Nurcan Değirmencioğlu,Ozan Gürbüz,Ali Değirmencioğlu,Yasemin Şahan,Hasan Özbey 한국식품과학회 2011 Food Science and Biotechnology Vol.20 No.5

The ‘Gemlik’ olive, grown in Turkey, is the main variety used in the production of commercial table olives. The aim of the present work was to determine the effect on sensory qualities of dry-salted olives of the ‘Gemlik’ cultivar packed with vacuum sealing or modified atmosphere packaging and stored at 4 or 20^oC. Storage temperature did not have a significant effect on the sensory profile (p>0.05). However, with the exception of the color attribute, somewhat higher overall scores were given to samples stored at 4^oC. In both vacuum sealing and modified atmosphere packaging (MAP) samples stored at 4^oC, the lack of oxygen and dipping the olives in 10 ppm chlorine solution before dry-salting, prevented the growth of yeast and mold and therefore both rancidity and softness attributes scored higher points by panelists.