||Itsuki Nakashima, Takumi Inoue, Ren Kadowaki, S. Oberst et al. (eds.), Vibration Engineering for a Sustainable Future, Chapter 7 Classification of Characteristic Modes for Vibration Reduction, Springer Nature Switzerland AG2021, DOI:10.1007/978-3-030-48153-7_7, Vol.2, 51-57., 2021.04, The finite element method (FEM) is useful for vibration analysis. However, it takes time to evaluate and reduce vibrations of large-scale structures such as au-tomobile bodies. Especially, when treating coupled modes that consist of global and local deformations, it is necessary to reinforce respective parts that relate to each deformation. This is because applying incorrect reinforcement settings con-tribute to vibration increase. The purpose of this study is to classify each charac-teristic mode into groups depending on approaches for vibration reduction. Espe-cially for structures such as automobile bodies, it is effective to focus on global and local deformations of each mode. Focusing on these deformations, we classi-fied the characteristic modes of an automobile underbody structure into three groups: global modes, local modes and coupled modes. By means of the classifi-cation, we proposed effective vibration reduction approaches for each mode group. Furthermore, the effectiveness of the presented classification and vibration reduction method for each mode group is demonstrated..
||Ren Kadowaki, Takumi Inoue, Kentaro Kameda, Kazuhisa Ohmura, S. Oberst et al. (eds.), Vibration Engineering for a Sustainable Future, Chapter 30 A New Testing Method for Bolt Loosening with Transmitted Ultrasonic Pulse, Springer Nature Switzerland AG2021, DOI:10.1007/978-3-030-48153-7_30, Vol.2, 227-233., 2021.04, Diagnosis of the bolt loosening is an important testing in many fields. This study aims to develop a new non-destructive testing method for the bolt loosening us-ing ultrasonic pulse projected to the side of the bolt. This method focuses on a transmitted pulse which travels across the bolt. This paper represents a demon-stration of the proposed method and discusses its mechanism through a geomet-rical identification of the transmission paths of the ultrasonic pulses. In the basic experiment with an aluminum block and a stainless steel bolt, tightening torque of the bolt could be evaluated via the amplitude of the transmitted wave which con-sisted of two pulses. Especially, the second pulse was sensitive to the tightening torque. On the other hand, geometrically, we identified 6 transmission paths in the block. Especially, two paths of them were relatively long, and traveled across two load flanks, whose transmittance was strongly affected by the tightening torque. This result suggest that the two pulses which traveled along these paths corresponded with the second pulse in the experiment. And the proposed method is qualitatively demonstrated..