Reconstruction of damping properties for bended specimen

Abstract

A general machine or structure is manufactured by combining a plurality of members, and these members may be used as they are in a simple shape or may be used after being shaped. When performing the dynamic design of such machines or structures by Finite Element Method, it is necessary to input the dynamic properties of the structural members. Here, there is no idea on the effect of the processed part on the overall dynamic properties when the member is shaped. In this study, a steel strip-shaped specimen was used as the target member, and the effect of bending of the member on the modal property was experimentally investigated. And the modal property was reconstructed by Finite Element Analysis with a local damping model at the bending part. As a result, the following conclusions were obtained. From the experiment, for the plain specimen, the relationship between the frequency and the structural damping coefficient was qualitatively and quantitatively constant regardless of the length of the specimen. On the other hand, it was found that the frequency-structural damping coefficient of the L-shaped specimen was not quantitatively constant and could not be expressed by a single function. In order to reconstruct the behavior by FEM, we proposed a method of locally adding a damping element to the bending part. It was found that the relationship between the frequency and the structural damping coefficient of the experimental results can be reconstructed regardless of the length of the specimen and the bending position if the local damping parameter was set appropriately. That is, the validity of the proposed local damping property addition model was confirmed.

Keywords

• experimental modal analysis
• identification
• shape processing
• modal properties
• local damping model