Session: 01-08-01: Passive, Semi-Active, and Active Noise and Vibration Control

Paper Number: 141227

141227 - Vibration Transmission Characteristics of Multi-Materials With Hard and Soft Layers Utilizing Photo-Patterning Polymerization 

In recent years, there has been an increasing demand for lightweight materials that are highly effective in reducing the noise and vibration. To achieve this goal, we verified the vibration-reduction effect of a polymer sheet created to mimic the surface shape and properties of a lady bugged leg. The epidermis of insect limbs is not uniformly hard but has a heterogeneous distribution of areas where the hardness differs by more than 103 orders of magnitude, such as GPa and MPa. We believe that this enables the insect epidermis to be lightweight and strong with low vibration, and we aimed to reproduce this extremely different state of hardness and softness using polymer sheets. Therefore, we created polymer sheets with extremely different hardness and softness values using a technique called photopatterning polymerization and investigated the vibration-reducing effect of these sheets through vibration tests. When designing a polymer sheet, the hard-soft distribution must be determined. The material has hard and soft portions, but its shape, dimensions, and ratio must be determined before it can be fabricated. In this study, the hardness-softness distribution required to produce a material with a high vibration transmission reduction effect was determined beforehand by numerical analysis using the finite element method. Finite element analysis was performed on a model of a polymer sheet with soft layers divided into a square lattice, and it was found that the 4- and 9-soft layer polymer sheets were better. Therefore, polymer sheets with four, nine, and 25 soft layers were fabricated, and vibration tests were conducted using random vibrations from 0 to 5000 Hz. Polymer sheets with four and nine soft layers reduced the amount of vibration transmission over a wide frequency range. Although there was qualitative agreement with the numerical results in that the vibration was smaller when the number of soft layers was smaller, the optimum number of soft layers could not be determined from the numerical analysis. This may be owing to the difference between the numerical analysis and experimental methods, particularly the method of vibration application and excitation. Although the optimal number of soft layers found in the numerical analysis did not agree quantitatively with the experimental results, those with four or nine soft layers had some advantages over those without soft layers or a single hardness sheet with no soft layers. Soft layers 4 and 9 reduced the vibration transmitted from the shaker to the weight plate, especially in the higher frequency range, compared with the case where nothing was inserted or a single hard sheet with no soft layers (all soft/all hard) was inserted. Therefore, it is considered effective in reducing vibrations in objects where the transmission of vibration over a wide range of frequencies is an issue. Finally, the polymer sheet was placed under the feet of an occupant in a car to investigate its effectiveness in reducing the transmission of vibration to the occupant when the subframe of the car was subjected to vibration. The vibration of the subject's feet was measured using a vibration accelerometer attached to the subject's shoe when the subject sat on a car seat and the subframe vibrated in the vertical direction of the car body. The effective value of the vibration acceleration generated in the subframe by the shaker was 4.8 m/s², and the vibration frequency was 50 Hz. The results of the experiment showed that the O.A. value of the vibration acceleration at frequencies between 50 and 2500 Hz was reduced by 6.1 dB in the vertical direction of the vehicle body when the subject's feet were vibrated compared with the case in which nothing was placed under the feet. In addition, the vibration acceleration was reduced by 3.1 dB compared to the case when a single hardness sheet (all soft) was inserted under the feet.

Presenting Author: Tatsuya Inoue Toyama Prefectural University

Presenting Author Biography: Tatsuya Inoue received the B.E. degree from Toyama Prefectural University Japan, in 2023. He is now in the graduate school of Mechanical Systems Engineering in Toyama Prefectural University. He specializes in noise and vibration. He is a member of the Society of Automotive Engineers of Japan and the Japan Society of Mechanical Engineers.

Authors:

Tatsuya Inoue Toyama Prefectural University
Koichi Fukuno Toyama Prefectural University
Haruka Fukunishi Nagoya Institute of Technology
Osamu Terashima Toyama Prefectural University
Mikihiro Hayashi Nagoya Institute of Technology
Shuho Yamada Toyama Prefectural University