(2) Damping function: the dynamic spring constant KD should be low enough for the required frequency;
(3) Anti-vibration function: In order to control the increase of conductivity during * * * vibration (inevitable), it should have high enough damping.
At the required frequency, the ratio of dynamic spring constant Kd to static spring constant Ks is called dynamic scaling factor. The smaller the ratio, the better the vibration reduction performance, but usually KD/KS > 1. In order to reduce the dynamic scale factor, it can also be discussed from the aspects of rubber matching or materials. It is effective to use high damping materials in improving the anti-vibration performance. For ordinary vulcanizates, Kd will inevitably increase with the increase of Ks. Therefore, it is necessary to discuss rubber blending from Kd and Ks.
Compared with other rubbers, natural rubber is characterized by its low dynamic proportional coefficient, so it is the most widely used. When the amount of carbon black is increased in natural rubber compound, high damping can be obtained, but at the same time, the dynamic ratio will increase. When the amount of sulfur increases, the dynamic magnification will decrease, but at the same time the damping will also decrease. There have been many discussions about rubber mixing. A patent introduced that 60% bromobutyl rubber was mixed with natural rubber, and hexamethylenetetramine was added as the curing agent of modified phenolic resin. Compared with before addition, although the hardness and static elastic modulus are greatly increased, the dynamic magnification is below the same level, the loss coefficient is increased and the damping is high. When talc powder (SiO _ 2 10mg0) or clay (SiO _ 2 10mg 1203) is added into the 60/40 (parts) natural rubber/PVC mixture, low dynamic magnification and high attenuation can be obtained. When silicon carbide (whisker) or boron nitride (powder with many acute angles or concave-convex shapes on the surface) is added to the carbon black blending system of chloroprene rubber, low dynamic magnification and high damping can be achieved, and the dependence of loss coefficient on temperature is relatively small, and the characteristics of stability in a wide temperature range can be obtained [1].
In addition, Wang Xiaoluoge et al. [4] used poly (aromatic olefin-copolymer maleimide) * * polymer, maleated alkyl olefin and alkyl diamine to form polyolefin grafted poly (aromatic olefin-copolymer maleimide) * * polymer under the condition of sufficient drying, and mixed this material with rubber to prepare high damping materials. The insulating rubber material for vibration reduction formed by [5,6] aromatic vinyl monomer such as Kentaro and butadiene * * * polymer has good anti-vibration and anti-noise characteristics, and this material also has good bending fatigue performance. Toshiaki et al. [7,8] used a mixture of unvulcanized isoprene-styrene block polymer and vulcanized p-methylstyrene-isobutylene * * polymer in the ratio of 80: 20 to 25: 75. When it was applied to damping rubber formulation, the loss factor Tanδ of this material was greater than 0.5. At the same time, the change of loss factor Tanδ is less than 0.5 in the range of -30℃ to 20℃, which makes the material not only have good vibration reduction performance, but also have good vibration reduction stability, and at the same time, the material also has good oxidation resistance and ozone oxidation resistance; Masashi et al. [9] used brominated vinyl polymer rubber (with 0.2-5% Br content), NR and isobutylene rubber as damping rubber materials, which had good thermal aging resistance, tensile fatigue performance and ozone cracking performance. After treatment at 90℃ for 65,438 0,000 hours, the tensile strength remained 62% and the compression set remained 39%. Okada et al. [10] made rubber * * * mixture with unsaturated polymer formed by unsaturated ethylene, aromatic olefin and non * * yoke olefin in a certain proportion, which made the vibration damping rubber have good mechanical properties, heat resistance, aging resistance, vibration damping performance, vibration loss and bending fatigue resistance.
Rubber shock absorber has many advantages [2]: 1) By designing the structure and adjusting the rubber properties, it can meet the requirements of stiffness in all directions; 2) It has both attenuation and energy absorption capacity, good vibration reduction effect, and is easy to cross the * * * vibration zone; 3) The elastic modulus is much smaller than that of metal, which can produce large elastic deformation; 4) there is no sliding part, so there is no wear and easy maintenance; 5) Light weight and convenient installation and disassembly.