Ünker, Faruk; Cuvalci, Olkan

In this study, a gyroscopic damper model consisting of a built-in column has been developed. The objective of this study is determining the required angular momentum with the optimum ratio of natural frequency for the gyroscopic vibration absorber under sinusoidal excitation. This damper model is investigated experimentally and theoretically for different angular momentums of the gyroscope and different frequency ratios of the structure and damper on a single-story structure. As a result of the study, the displacement of the structure at the 1st mode frequency for a given angular momentum of the gyroscope is fairly reduced. Besides, at a notable frequency ratio of the damper and the structure, the effect of the angular momentum is improved. Even if the disk mass of the gyroscope decreases, it is possible to obtain a certain angular momentum by increasing the disk speed. Thus, lighter and less bulky gyroscopic vibration dampers can be designed. The cooperation of the required angular momentum with the optimum ratio of natural frequencies should be considered to obtain a highest attenuation of the building vibration. In addition, the equations of motion obtained according to the 1st mode and the theoretical results overlapped.

Kaplan, Erdar; Sukuroglu, Ebru Emine; Cuvalci, Olkan

This paper investigates the tribological effects of composite oxide coatings grown on ZA-27 surfaces under dry sliding condition. Coating processes were conducted using three different electrolytic solutions through micro-arc oxidation (MAO) method. The base electrolytic solution without any particles as additives was labeled as MAO-Coated, whereas electrolytic solution labeled as Coated-A contained graphite particles and Coated-B contained hexagonal boron nitride (h-BN) particles incorporated into base solution. The morphology of each coated samples were analyzed using a Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD). The friction and wear tests were conducted using a pin-on-disc tester in order to evaluate the tribological behavior. Results indicated the friction coefficients of both Coated-A and Coated-B samples were lower when compared to that of uncoated ZA-27 alloy. Further comparative studies showed Coated-A samples containing graphite particles resulted in the lowest friction coefficient.