Study On Viscoelastic Damping Material And Dynamic Performance Of Constrained Damping Structure

Constrained damping structure which is formed by viscoelastic damping material, base structure and constrained layer is an effective way to reduce vibration and noise. So it’s particularly important to research the dynamic performance of constrained damping structure. This paper has characterized the common performances and dynamic mechanical properties of an modified polyurethane viscoelastic damping (hereinafter referred to as viscoelastic damping material), and the data fittings were obtained by MATLAB. This work designed the modal strain energy finite element analysis by ANSYS to consider the infection of temperature and frequency. And then, the dynamic mechanical properties of the constrained damping structure has been investigated by combining finite element method and modal vibration test. And the influential factors of the structure’s dynamic properties were discussed.The main conclusions of the paper are as follows:Firstly, the common performance of viscoelastic damping material was characterized. The density was0.9625g/cm3which showed this material had negligible impact on the vibration pattern.The gel time, tack time and hard drying time were158s,46min and178min respectively. The solid content was up to92.71%. The above figures suggested that viscoelastic damping material was a high solid content environment-friendly and rapid solidified material. The Shore A hardness was30.The tensile strength and elongation at break were8MPa and360%respectively.Secondly, according to the studies on damping properties, with dynamic thermo-mechanical analysis(DMA),the glass transition temperature (Tg) was measured20℃～40℃and the peak of loss factor was above0.7. At the same frequency, with temperature rised, the storage modulus reduced and the loss factor firstly increased and then decreased.The peak loss factor existed in Tg. At the same temperature, the higher frequencies resulted in the higher storage modulus.The test data of DMA was accomplished by MATLAB software to obtain the curve functional expressions. The sum of squares for error (SSE) and the R-square of storage modulus-frequency fitting were1.319and0.9998respectively. The SSE and the R-square of loss factor-frequency fitting were0.0001103and0.9996respectively. It had a high fitting accuracy.Thirdly, finite element analysis indicated that, the modal strain energy method without considering the influence of temperature had acceptable precision. The maximum error of natural frequency was0.038and the the maximum error of structural loss factor was0.127.The first five natural frequencies were46.90Hz,104.32Hz,202.57Hz,355.83Hz,452.90Hz. The first five natural frequencies and structural loss factors of experimental module were calculated by the modal strain energy finite element analysis method considering the iterations of frequency. The frequency values were46.90Hz,104.32Hz,202.57Hz,355.83Hz,452.90Hz. The structural loss factor values were0.138,0.139,0.144,0.143,0.141.Fourthly, damping research of the modal vibration test showed that the first five natural frequencies of experimental module were45Hz,90Hz,180-190Hz,370-380Hz,482/466Hz. The first five structural loss factors were0.120-0.123,0.122,0.124～0.127,0.123～0.126,0.123. Self-power spectrum analysis of the modal vibration test indicated that from OHz to1000Hz, resonance was most likely to occur at the two frequencies of45Hz and190Hz.The results of finite element analysis were consistent with the results of modal vibration test. The two data of first five natural frequencies matched well in the lower modes while the difference was less than20Hz in the higher modes.Fifthly, the boundary conditions, ambient temperature, damping layer’s thickness and stiffness, constraining layer’s thickness and stiffness were all influential to the dynamic performances of constrained damping structure. Under different boundary conditions, the strain energy of damping layer was smaller in the constrained edges and displacement peak. The strain energy of damping layer was greater in none displacement. With the boundary layers value increasing, both the structural natural frequencies and loss factor increased. With the constraint effect increasing, the natural frequencies increased and the loss factor decreased. With temperature increasing, the natural frequencies reduced and the loss factor firstly increased and then decreased for structures having the same thickness. The loss factor peaked at Tg. For different thickness of damping layer structure,it suggest that When temperature below Tg, the larger the thickness, and the the higher the natural frequency. If temperature was above Tg, temperature had less influence on structural natural frequencies.With the thickness of damping layer increasing, both the natural frequency and the loss factor increased but the growth rates decreased. With the thickness and stiffness of damping layer increasing, the natural frequency increased with a decreasing velocity and the loss factor firstly increased and then decreased. With the stiffness of constraining layer increasing, both the natural frequency and the loss factor increased with a decreasing velocity.Through the above theoretical analysis, analogue simulation and experimental study, this paper provided a high-precision dynamic performance analysis method of constrained damping structures, obtained the changing regularity of the structure’s dynamic performance, and supplied guidance to the practical application of damping structures.