1980 年 36 巻 4 号 p. 185-193
The graphical expression of the internal structure on the problem of elastic dynamics written in stress tensor and velocity vector, makes the consideration of the performance of elastic systems easy. This paper is concerned with the equivalent electrical circuit expressions and wave equations of the elastic systems. The spatial distributed electrical circuit corresponding to the equation of motion and the equation of equilibrium for a three dimensional isotropic elastic medium, is introduced by mobility analogy. The equivalent circuit expressions are made for longitudinal waves and transverse waves propagating through infinite medium, for those waves in plates, for those waves and torsional waves in bars, and for transverse waves in the stiff strings and in the plates on elastic medium. From these expressions the wave equations are derived. By neglecting some components of the equivalent circuit according to the condition of the medium, methods of simplifying the wave equation are shown. The equivalent circuits including loss factors are discussed. As computer simulation of the equivalent circuits can be realized by means of the finite difference method, the numerical solution of the problem of the vibration written in wave equation can easily be obtained.