Chiroiu V., Munteanu L.

Eliminating vibrations and controlling dynamics in macro-, meso- and nano-world are subjects must addressed to applications in macroelectromechanical, microelectromechanical and nanoelectromechanical structures. One of the major obstacles to miniaturization and to build useful micro- and nano-sized devices, involves dramatic change to mechanical properties that can occur as the size of a system shrinks below the macroscale toward to mesoscale, and below the mesoscale toward the atomic. It is of special interesting the fact it is not possible to grow materials without dislocations and/or other defects or disturbances to crystalline order, such as vacancies, interstitials, or impurities at the meso- and nano-scales. The damaged materials exhibit interesting damping properties. In this paper we study the damping across the nanoscopic scale, mesoscopic scale, and macroscopic scale, by considering the simplest instrument for the study of material damping, the pendulum. The pendulum was studied by Galileo, Huygens, Newton, Hooke and all the best known scientists in the world. It served to establish collision laws, conservation laws, the nature of Earth's gravitational field, it was the basis for Newton's two-body central force theory. In this paper, the pendulum is an important research instrument for studying damping across the length scales. The free transverse vibrations of a pendulum consisting of a bob suspended from a wire are studied in two cases: (1) a molecule suspended from a carbon nanotube with a single wall, and (2) a bob suspended from a rod with miscrostructure. The decay of vibrations is not a pure exponential for both problems, and the quality factor becomes time-dependent. For a damaged nano pendulum, the equilibrium position is shifting during vibrations. After vibrations died out, the equilibrium position remains shifted. So, we believe that the pendulum is still important in a fundamental sense of understanding the damping properties of materials