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    Comparison of the Effect of Diameters and Numbers of Cannulated Screws and Headless Compression Screws on the Reduction Stability in Transverse Patellar Fractures: A Finite Element Model Study
    (Amer Scientific Publishers, 2017) Ugur, Levent; Karadeniz, Selami; Yıldız, Aytaç
    Background: Patella fractures constitute 1% of skeletal trauma. Transverse patella fractures are the most common types of patellar fractures. A fracture gap more than 2-3 mm or irregularities in cartilage require surgical treatment. There are various surgical options available, and one of these options is the screw fixation. This study aims to investigate the effect of the diameter and number of cannulated screws and headless compression screws on the reduction stability of transverse patellar fractures. Methods: In this study, the knee joint with normal anatomy and the knee joint with transverse patellar fracture were modeled using longitudinal lower extremity computerized tomography (CT) images taken in DICOM format. In the knee model with transverse patellar fracture, two circle divide 3.5 mm cannulated screws and one circle divide 4.5 mm cannulated screw, two circle divide 3.5 mm and one circle divide 4.5 mm headless compression screws were inserted respectively; and the maximum equivalent stresses (MES) occurred in the screws and the stability of the patella were examined in a total of 16 models at 30 degrees, 45 degrees and 60 degrees flexion angles and in the normal position (0 degrees) of the knee. The analysis was performed non-linearly and dynamically using ANSYS (version 17) and the same boundary conditions were applied in all models. Results: As a result of the analysis, the maximum stresses on the screws in the models with cannulated screws and headless compression screws were compared. When the maximum stresses in the screws were examined, it was observed that the maximum stress was lesser in the model with two circle divide 3.5 mm headless compression screws, and the maximum stress was found to increase in the single circle divide 4.5 screws. Sixteen different models were analyzed with the help of the Taguchi method and the most suitable model and parameters were determined according to the maximum equivalent von Mises stress value. Conclusions: The use of a single screw in the treatment of transverse patella fractures can lead to loss of reduction. If screw treatment is preferred, it was observed that the 2-screw application was more stable and the fixation with the headless compression screw was found to be more stable compared to the cannulated screw at various degrees of flexion.
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    Investigation of effect on energy consumption of surface roughness in X-axis and spindle servo motors in slot milling operation
    (Elsevier Sci Ltd, 2019) Ozturk, Burak; Ugur, Levent; Yıldız, Aytaç
    The energy cost is a significant expense in the machining companies, and the reduction of energy consumption has a critical prescription in the industry. To increase energy efficiency, machine producers have contributed by developing advanced functions for machines. Besides these, one of the main purposes of machining is to bring the desired surface roughness to the best level. In this study, it is aimed to optimize cutting parameters to minimize the surface roughness and the energy consumption in the process of the 7075-aluminium material, which is commonly used in manufacturing industry, in CNC milling machine under dry cutting conditions. Therefore, a test list was created with Taguchi L9 experiment design the surface roughness and the power consumption of the machining centre were measured by processing in the CNC milling machine according to the tool diameter, cutting depth, cutting speed and feed rate parameters. The measured values were analyzed in the Minitab 17 program for the Taguchi method. According to the results of the analysis, X axis servo motor's P-cutting value is affected by the amount of depth of 82%. However, the spindle servo motor's P-cutting value was determined to be affected by the highest 34% cutting speed. The SEC (Specific Energy Consumption) value of both servo motors is affected by the maximum amount of depth. It is the amount of SCEC (Specific Cutting Energy Consumption) allows us to characterize machinability of the materials according to results from energy consumption. SCEC value is affected by the cutting speed 53% rate in the axis servo motor. In addition, it is affected by the feed rate of 43% in the spindle servo motor. (C) 2019 Elsevier Ltd. All rights reserved.