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    DETERMINATION OF OPTIMUM SHAKING FREQUENCY AND AMPLITUDE OF PROTOTYPE BODY SHAKER USED FOR MECHANICAL HARVESTING OF PISTACHIO
    (Agronomski Fakultet Sveucilista U Zagrebu, 2017) Polat, Refik; Guner, Metin; Erdogan, Dogan; Gezer, Ibrahim; Atay, Umran; Aktas, Turkan
    Important problems have been seen during harvesting of different fruit trees in Turkey. The highest cost in fruit growing constitutes harvesting process as 43.99% of total cost. In this research, a body shaker which was mounted to tractor three-point linkage system and driven by power take off system was designed and manufactured to decrease the cost of harvesting of tree fruits. A tractor with 70 BG power is enough to transport and operate this body shaker. This prototype was functioned with a system including a hydraulic pump taking movement from power take-off and hydraulic motor. Body shaker could be controlled by only one person. Harvesting tests using different frequencies and amplitudes were carried out with body shaker. Two pistachio tree cultivars namely Siirt and Kirmizi were used during the harvesting tests. Pistachio fruits which remained on the branch and leaved from branch were weighed separately to determine of harvesting efficiency. For this aim, performance of body shaker was determined. As a result, the best performance result was determined using 40 Hz frequency and 20 mm amplitude. The harvesting efficiency values in harvesting tests carried out using 40 Hz frequency and 20 mm were calculated 93.27% for pistachio cultivar of Siirt and 87. 06% for pistachio cultivar of Kirmizi.
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    Experimental and numerical study on micro-milling of CoCrW alloy produced by selective laser melting and casting
    (Sage Publications Ltd, 2024) Oymak, Mehmet Akif; Bahce, Erkan; Gezer, Ibrahim
    CoCrW can be produced using Additive Manufacturing (AM), while casting methods are commonly used for applications such as dental prostheses. However, rapid heating and cooling during AM production can lead to internal defects, micro-cracks, and shrinkage. Micro-milling can help enhance the material's structure and impart micro-scale properties. This study aimed to investigate the micro-milling properties of CoCrW products manufactured using AM and compare them with materials produced by casting. Numerical models and experimental studies were conducted to examine the differences. Results showed that CoCr alloys produced with AM exhibited 25%-30% lower burr formations, while CoCrW produced by casting had 2%-5% lower surface roughness. Micro-milling experiments demonstrated that a feed rate of 2.5 mu m/tooth resulted in 35%-40% more burr formation and surface roughness compared to a feed rate of 5 mu m/tooth in both SLM and casting methods, attributed to the cutting edge radius. The cutting temperature and top burr height were analyzed using finite element simulations and experimental methods. It was observed that the maximum temperature in CoCrW produced by casting was 6%-15% higher than that in the SLM method. The finite element analyses and experiments revealed a difference of 4%-7% in maximum temperatures and top burr height.
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    Production and Cleaning of Lattice Structures Used in the Space and Aerospace Industry with Metal Additive Manufacturing Method
    (Springer, 2022) Akbay, Ozgun Ceren; Bahce, Erkan; Uysal, Alper; Gezer, Ibrahim
    Thanks to additive manufacturing, the use of lattice structures in aviation and space industry, especially heat exchangers, fuel nozzles and turbo machines located at the front of airplanes has increased. The production of computer-designed parts with the desired precision and geometry is important for concepts such as assembly, wear and surface properties. Problems encountered in selective laser melting (SLM) such as porosity, powder particle adhesions, affect assembly and surface properties. For this reason, cleaning is inevitable in sensitive systems used in the aerospace industry to have ready-to-use products after production or to prevent dust particles from breaking and causing problems in the workflow. To this purpose, chemical washing process was applied to improve the surface quality of the lattice structures and the healing effects of the acids used on the surfaces were investigated. In the experiment, nine lattice structures were produced from CoCr alloy and the effects of three different acid solutions prepared using hydrofluoric acid, nitric acid, sulfuric acid and hydrochloric acid on surface cleaning capacity were examined. The changes in the models immersed in the acid solution using the controlled immersion method for 180 seconds are presented comparatively. As a result of the experiment, it was seen that especially the solution containing hydrofluoric acid contributed to the improvement of the surface properties after production.