Akio Sugimoto

Reduction of radiated sound from a continuum using low‐damping vibration absorbers

When reducing the sound radiated from a resonant structure, it is necessary to ensure that the driving frequency does not correspond to any of the system resonance frequencies. In addition, it may be desirable to use dynamic vibration absorbers to reduce the response at the driving frequency. In this paper, a low‐damping vibration absorber is studied for solving noise radiation problems from a resonant, light‐gauge structure driven by a force whose frequency and amplitude are constant and whose frequency does not match any of the system natural frequencies. When the driving frequency and the structures natural frequency are different, the structure cannot be represented by as a SDOF system. Therefore, the conventional design method, based on equivalent mass, is inapplicable. In this paper, a design method based on the mobility of the structure is proposed. By means of the proposed method, the sound power radiated from a simply supported beam with an attached absorber is calculated and it leads to the fol...

Micromechanical Analysis of Vibration Damping Properties of A Polymer Based Composite Material

A tangent delta of a polymeric material, which influences the vibration damping capacity strongle, is high in value nearby the glass transition temperature of the material. Therefore, when the constituents of a polymer-based composite material are various in their glass transition temperatures, the magnitude of the macroscopic tangent delta of such a composite is expected to be high in wider range in temperature. In the present study, a shape memory polymer (SMP) particle/SMP matrix is used as a sample material and its macroscopic complex modulus and tangent delta are derived explicitly by using the equivalent inclusion method and the Mori-Tanakas theorem. For the case of a four mode type of distribution of the glass transition temperatures of particles, the value of the macroscopic tangent delta becomes higher than that of the monolithic SMP at any temperature and it becomes constant in the temperature range from 20°C to 60°C.