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Vibration absorption performance of polyurethane

Views: 240 Update date: Jun 09,2020

 Vibration absorption polyurethane The effect of polyurethane elastomer on alternating stress shows obvious hysteresis. In this process, part of the energy of the external force is absorbed by the internal friction of the elastomer molecules, which is converted into heat energy. This property is called the vibration absorption property of the material, which can also be called the damping property. The vibration absorption performance is usually expressed by damping coefficient. The attenuation coefficient represents the percentage of energy that the deformed material can absorb. It is not only related to the properties of materials, but also to the ambient temperature and vibration frequency. The higher the temperature is, the lower the attenuation coefficient is. The higher the vibration frequency is, the greater the absorbed energy is. When the frequency is close to the relaxation time of macromolecules (the same order of magnitude), the energy absorbed is the largest. At room temperature, polyurethane elastomer can absorb 10% - 20% of vibration energy, which is better than butyl rubber. It is suitable for absorbing large impact force when the deformation amplitude is small and small impact force when the deformation amplitude is large.

 

  In addition, it should be pointed out that the lag phenomenon produces endothermic heat, which makes the elastic temperature rise. Due to the increase of elastic temperature, its resilience is improved and its damping performance is decreased. Therefore, the performance balance must be considered in the design of vibration damper. The following suggestions can be used for reference.


The hardness of the damper shall match the static load and impact load. Under the static load, the vibration damper is basically not deformed and will not be damaged due to deformation under the impact load.


The vibration frequency has a great influence. If the vibration frequency is small, the compression ratio of the damper can be larger; otherwise, the compression ratio should be smaller. In addition, it is necessary to select the appropriate vibration damper elasticity according to the vibration frequency, the vibration frequency is high, and the elasticity of the vibration damper is better, so as to reduce the internal heat generation. If the vibration frequency is small, the elasticity of the shock absorber is lower. If the spring back is less than 40%, it can absorb more vibration energy and improve the shock absorption performance.


In order to reduce the internal heat of elastomers, polyurethane elastomers and metal springs are used together, which often get good results. There are many kinds of designs used at the same time. The purpose is to give full play to their advantages and overcome their shortcomings. In addition, in order to reduce the internal heat, improve the heat dissipation effect and reduce the cost, polyurethane microporous elastomer is also a good choice. It has been widely used as the sole, car damping parts (such as stop blocks) and high-speed iron damping pads.


     Polyurethane elastomer with small internal heat and good dynamic performance can be selected for some cushioning parts with high safety and comfort requirements, such as polyurethane elastomer prepared by NDI, PPDI and chdi, but the cost will be greatly increased.




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