Experimental Research On Viscoelastic Damping Material And Damping Performance Of Its Abnormal Shaped Constraint Damping Structures

At present, the research of constrained damping structure is mainly focussed on improving the performance of the damping material itself and on the optimization design of constrained damping structure. Among the above, the constraint damping structure optimization design research is mainly raleted to structures of regular rules like beam and slab, but rarely to the abnormal shaped constraint damping structures. This paper has carried out the characterization of the conventional properties and the damping properties of a new type of polyurethane viscoelastic damping material, which mainly includes the curing time, solid content, hardness, tensile strength, elongation at break and dynamic mechanical properties. The physical properties and damping properties of the material itself has been analyzed in this way. Then the arc type and annular type of abnormal shaped constrained damping structures have been designed with the above-mentioned material in the damping layer. Through the hammer vibration experiment, the damping performance and the main influencing factors of the structures have been studied.The main conclusions of the paper are as follows:Firstly, the conventional performance of viscoelastic damping materials,including curing time, solid content and basic mechanical properties, have been characterized. Meanwhile, energy storage modulus, loss modulus and the relationship between loss factor and temperature or frequency have been obtained throngh DMA test. The results showed that, gel time of the measured viscoelastic damping materials was 172 s, the tack time was 16 min, and the hard dying time was 54 min. Solid content was 92.02%. Shore A hardness was 53. Development cycle was 15 d. Tensile strength and elongation at break was 8MPa and 360% respectively. When the frequency was invariant, with the rise of temperature, energy storage modulus decreases consistently. Glass-transition temperature of the metarial tested was about-40℃~20℃.Secondly, the function of viscoelastic damping materials in arc constraint damping structure and variation trend of arc constraint damping structure with the stiffness of its constraint layer changed have been studied. The results showed that, Viscoelastic damping material made vibration time and vibration acceleration amplitude of the arc structure reduced by 50% and 26.7% respectively. And natural frequency of 1~5 order decreased while composite loss factors increased. Total vibration total value was reduced by 10.42 dB. When stiffness of the constraint layer changed from 21.60×109Pa and 35.5×109Pa, vibration time length of arc constrained damping structure were all about 0.06 s, while vibration acceleration amplitude increased slowly from 8m/s2 to 11m/s2. The enhanced stiffness of the constraint layer could increase the natural frequency and compound loss factor under each order of constraint damping structure. But their growth rates were gradually reduced with the increase of constraint layer stiffness. The stiffness of constraint layer had more effect on higher order natural frequency and compound loss factor, but rarely affacted that of the lower order. Vibration acceleration level and total vibration value increase with the increase of the stiffness of constraint layer.Lastly, the function of viscoelastic damping materials in annular constraint damping structure and the effect of thickness of damping layer on annular constraint damping structure have been researched. The results showed that, Viscoelastic damping material made vibration time and vibration acceleration amplitude of the annular structure reduced by 35.7% and 13.3% respectively. composite loss factor of 1~3 order were all enhanced, while Total vibration value was reduced by 10%. Decreasing amplitude was more obvious under medium frequency. When the thichness of the damping layer changed from 1mm to 3mm, vibration acceleration amplitude, high order natural frequency, total vibration value and low-midium-frequency vibration acceleration level were all reduced, while compound loss factor increased. When the thickness of damping layer increased to more than 3mm, the damping performance of annular constraint damping structure had decreasing dependence on the thickness of damping layer.Through the above study, the effect of viscoelastic damping material on abnormal shaped constraint damping structure and main effect factors on the damping performance of abnormal shaped constraint damping structure were discussed, aiming to provide certain experiment basis for the appliance of abnormal shaped damping structure to the vibration and noise reduction projects.