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    Effect of Cementite Carbide Tool Coating Type and Tool Radius on Cutting Performance
    (Ieee, 2016) Yildiz, Tugce; Irez, Alaeddin Burak; Sur, Gokhan
    The present study represents an experimental investigation on machinability of Ti6Al4V titanium alloy by turning method. The effects of coating type (CVD and PVD coating) and cutting tool nose radius on dynamics of machining in particular the resultant cutting force and surface roughness were explored in dry cutting conditions and constant cutting depth. Cutting parameters were selected as two different cutting speed (75, 100 m/min), three different feed rate (0.15, 0.2, 0.25 mm/rev), three different nose radius (0.8, 1.2, 1.6 mm) and two different cementite carbide tool utilized (CVD and PVD coated tools) according to the literature survey and ISO 3685 standard. The components of cutting force (F-C, F-F, F-R) on cutting cementite carbide tool were measured by piezo-piezo-electric dynamometer and surface roughness measured by profilometer. It was seen that main cutting force (F-C) is the most prominent constituent of the resultant force. In addition, effects of feed rate and cutting speed to the machinability were verified experimentally. Experimental results showed that physical vapor deposition (PVD) coating causes more important resultant force values compared to chemical vapor deposition (CVD) coating for the cutting speeds 75 m/min, 100 m /min and CVD coated cutting tools causes rougher surfaces compared to PVD coated tools for the same cutting speeds. Furthermore, the resultant force decreases while the tool nose radius increases for CVD coated tools and surface roughness decreases while the tool radius increases for both CVD and PVD coated cutting tools.
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    Effect of foam structure on thermo-mechanical buckling of foam core sandwich nanoplates with layered face plates made of functionally graded material (FGM)
    (Springer Wien, 2023) Yildiz, Tugce; Esen, Ismail
    The present investigation involved the modeling and analysis of the thermomechanical buckling behavior of sandwich nanoplates with foam core layers. The study employed the utilization of the new higher order deformation theory and nonlocal strain gradient elasticity theory. The modeling of foam core involves separate consideration of uniform and symmetric open cell foam distribution types, while the face plates are predicted to exhibit FGM and isotropic layers. A total of six sandwich plate types were modeled and analyzed. The thermomechanical buckling behavior of sandwich nanoplates is significantly influenced by the sandwich type, volumetric foam ratio of the core layer, and its distribution along the foam core height, as demonstrated in prior analyses. The study revealed that the incorporation of foam structure resulted in an elevation of the buckling temperature during the thermo-mechanical response of the nanoplate. At low temperatures, the uniform foam model had lesser thermal buckling than the symmetrical foam model. However, this trend changed after reaching Delta T = 350-360 K levels. The study is expected to yield significant insights into the development and application of nanosensors, transducers, and nanoelectro mechanical systems that are designed to operate in high-temperature settings.
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    The effect of the foam structure on the thermomechanical vibration response of smart sandwich nanoplates
    (Taylor & Francis Inc, 2023) Yildiz, Tugce; Esen, Ismail
    This study aimed to model the thermomechanical vibration behavior of sandwich nanoplates consisting of a foam or solid core layer and smart surface layers. The sandwich plate's mechanical behavior is analyzed using the nano-size effect, nonlocal strain gradient theory, and sinusoidal higher-order plate theory. Hamilton's principle is employed to derive the equations of motion, which are subsequently solved using the Navier method. The impacts of temperature, foam structure, foam void ratio, smart materials, and the external electric and magnetic potentials applied to the surface layers on the thermomechanical behavior of a sandwich plate have been analyzed.
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    Investigation of drilling properties of AA7075/Al2O3 functionally graded materials using gray relational analysis
    (Sage Publications Ltd, 2021) Yildiz, Tugce; Sur, Gokhan
    The present paper reports an experimental study on the fabrication and characterization of aluminum-oxide-reinforced functionally graded aluminum composites and optimization of drilling parameters on thrust force and average surface roughness using gray relational analysis. For this purpose, AA7075/Al2O3 functionally graded materials were produced with three layers that have different ratios of Al2O3 via high-temperature isostatic pressing and powder metallurgy method. Hardness behaviors of the layers were determined. Further, microstructural characterizations of the layers were carried out. Functionally graded materials were machined at dry cutting conditions with a 6 mm uncoated cemented carbide drill bit. The drilling experiments were carried out under different conditions such as point angles, helix angles, and feed rates, while the 25 m/min cutting speed was kept constant. The effects of factors on thrust force and surface roughness were evaluated using analysis of variance and gray relational analysis in full factorial experimental design. The minimum thrust force was measured at 221 N in a 140 degrees point angle, 15 degrees helix angle, and 0.075 mm/rev feed rate. Results of the gray relational analysis showed that feed rate was the dominant factor on thrust force and average surface roughness. Consequently, the highest and lowest gray relational grades were obtained at 0.899 and 0.374, respectively.
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    Thermomechanical Vibration Response of Solid and Foam FGM Nano Actuator/Sensor Plates
    (Springer Heidelberg, 2024) Yildiz, Tugce
    Purpose In this study, the effect of foam structure on the thermomechanical behaviour of high void ratio porous FGM piezoelectric smart nanoplates is investigated. Method The material of the smart nanoplate consists of PZT-4 on the bottom surface and BaTiO3 on the top surface and is formed by functional grading of these two materials along the thickness of the plate. Four different foam distribution models are modelled to examine the foam structure of the highly porous smart nanoplate, which has become widespread in biosensor applications. For this reason, uniform, symmetrical, top symmetrical and bottom symmetrical foam distribution models are created up to 75% void ratio. To determine the nano size, equations of motion are obtained by using nonlocal strain gradient elasticity and sinusoidal shear deformation theories together, and these equations are solved by the Navier method according to general boundary conditions. Result and Conclusions As a result of the analysis, it is observed that the applied external electric potential creates a softening effect on the plates with the piezoelectric elasticity effect and therefore reduces the thermal buckling temperatures. It is observed that the presence of the foam structure significantly improves the thermal resistance of the material and increases the buckling temperatures. It is also observed that the foam distribution model has significant effects on the thermomechanical behaviour.