207 球形シェルの減衰評価における解析法の検討

Abstract

An analysis for vibration of spherical shells with a constrained viscoelastic layer and metal layers is presented. In this paper, vibration damping properties of three layered spherical shells with viscoelastic material are analyzed from both of SEM (Strain energy method) and CEM (Complex eigenvalue method). Eigenvalue and eigenvector (displacement functions) are analyzed based on the Ritz method, when natural frequency, modal loss factor and strain energy are obtained. In CEM, the elastic modulus of viscoelastic material is dealt with complex quantity considering material loss factor. In SEM, modal loss factor is defined as a ratio of damping energy (strain energy consumed in viscoelastic layer) dissipated during a vibration cycle and total strain energy of the shell. The accuracy and validity of the present results from two methods are illustrated through investigation of convergence and comparison with the established results from the literature. Numerical results are presented for different parameters, such as the opening-angles, material loss factors and circumferential wave numbers.