Rubber shock absorbers are widely used in mechanical equipment, automobiles and other fields. The dependence of its dynamic modulus and damping characteristics on frequency is the key factor in determining the shock absorption effect. This frequency dependence stems from the unique viscoelasticity of rubber. Its mechanical behavior has the characteristics of both elastomers and viscous fluids. Under vibration loads of different frequencies, it exhibits different energy storage and dissipation capabilities.
The viscoelastic nature of rubber determines the frequency response of its dynamic modulus and damping characteristics. When the vibration frequency is low, the rubber molecular chain has enough time to adjust its conformation to adapt to changes in external forces. At this time, the elastic properties of rubber dominate, and it can store and release energy like a spring. The relative movement between molecular chains is relatively smooth, and the energy loss is small. Therefore, the dynamic modulus is relatively stable and the damping characteristics are also weak.
As the vibration frequency increases, the external force action time is shortened, and the movement of the rubber molecular chain gradually cannot keep up with the rhythm of external force changes. The internal friction of the molecular chain segments increases, and the relative movement between the segments is restricted, which makes it difficult for the rubber to quickly recover to its original state when absorbing energy, and part of the energy is dissipated in the form of heat energy. At this time, the dynamic modulus of the rubber begins to increase significantly, and the damping characteristics are also enhanced, which is manifested as better vibration attenuation ability.
The formula composition of rubber has an important influence on its frequency dependence. The addition of compounding agents such as fillers and plasticizers will change the interaction between rubber molecular chains. For example, fillers can form physical cross-linking points inside the rubber to limit the movement of molecular chains. This makes it more difficult for the rubber molecular chain to respond to external force changes under high-frequency vibration, the dynamic modulus is more significantly improved, and the damping characteristics are also enhanced accordingly. Different types and contents of compounding agents will make the rubber shock absorber present different characteristics in frequency response.
The actual working environment of the shock absorber will also affect its frequency dependence performance. There is an equivalent relationship between temperature and frequency, and the mechanical response of rubber in low temperature environment is similar to high-frequency loading. Therefore, when designing a rubber shock absorber, it is necessary to comprehensively consider the temperature range and vibration frequency distribution in the use scenario. Even for the same rubber material, its dynamic modulus and damping characteristics will have significant differences under different temperature and frequency combinations, which requires designers to make targeted optimization according to actual working conditions.
In the engineering design of shock absorbers, the frequency dependence of dynamic modulus and damping characteristics must be fully considered. For equipment that mainly bears low-frequency vibration, such as the suspension system of automobiles, it is necessary to select rubber materials with low dynamic modulus and moderate damping characteristics in the low-frequency band to ensure riding comfort; while for high-frequency vibration environments, such as industrial motor equipment, materials with stronger damping characteristics in the high-frequency band should be selected to enhance the ability to attenuate vibration. By adjusting the rubber formula and shock absorber structure, the frequency response characteristics of the product can be matched with the actual working conditions.
With the development of technology, the research on the frequency dependence of rubber shock absorbers has been continuously deepened. The development of new rubber materials and the application of intelligent control technology have provided new directions for the optimization of shock absorber performance. For example, magnetorheological rubber can adjust the damping characteristics in real time through an external magnetic field, so that it can achieve ideal shock absorption effect at different frequencies. In the future, with the deepening of the understanding of the characteristics of rubber materials, rubber shock absorbers will develop in the direction of being more efficient, smarter, and adaptable to more complex working conditions.
