The vibration isolators used in engineering practice mainly include metal spring isolator, wire rope isolator, rubber isolator, metal rubber isolator, and air spring isolator.
1.Metal spring isolator
The metal spring isolator is one of the earliest types of isolators. Cylindrical coil spring isolators, conical coil spring isolators, and butterfly spring isolators are used in engineering. The spring material is generally selected from manganese steel, silicon manganese steel, and chromium vanadium steel. Due to the ideal elasticity of steel springs, the stress and strain are linear over a wide range, and the material and structural parameters can be changed within a wide range, which can adapt to different loads, deformations and lower resonance frequency requirements. In addition, the coil spring isolator has the advantages of low cost, no corrosive environment, high temperature resistance and the like. However, the coil spring isolator is less damped and does not provide sufficient damping to suppress vibration, and the high frequency vibration isolation performance is poor.
2. Rubber isolator
Rubber vibration isolators are the most widely used type of vibration isolator. It is widely used in the field of vibration isolation of rolling stock, ships, automobiles, airplanes, bridges and meters. The rubber vibration isolator uses the elastic deformation of the viscoelastic damping structure to achieve the vibration damping effect, converts the vibration energy into the internal friction energy of the damping material, and has high conversion efficiency. It can be used in either a compressed state or a sheared state. In the application, if the rubber material and damping structure parameters are selected reasonably, good damping and vibration isolation can be achieved. Rubber isolators are the most widely used vibration isolators because of their advantages:
(1) It can be vulcanized into various shapes to meet the requirements of space. By adjusting the rubber formulation components to control the hardness, it can meet the requirements of rigidity and strength in all directions.
(2) It has sufficient internal damping, which is suitable for the case where the static displacement is small and the dynamic displacement is short but large. The vibration isolation effect is good, which is beneficial to overcome the resonance region and attenuate high-frequency vibration and noise.
(3) The modulus of elasticity is much smaller than that of metal, which produces a large elastic deformation.
(4) It has no sliding parts and is easy to maintain.
(5) It is small in quality and easy to install and disassemble.
However, in practical applications, rubber vibration isolators also have the following disadvantages:
(1) It is resistant to high, low temperature and oil resistance than metal materials.
(2) It cannot be directly exposed to the external environment and is prone to aging.
(3) It creeps and lags when used for long loads.
(4) It has poor vibration isolation performance at low frequencies.
The wire rope vibration damper was first developed by the United States in the late 1970s and is a typical nonlinear vibration isolator. Its damping characteristics are related to deformation and have good vibration isolation performance. When the amplitude is sufficiently large, the wire rope vibration damper is a vibration isolator that absorbs and dissipates vibration energy by dry friction damping between the respective strands. When the amplitude is small, the wire ropes of the wire rope vibration damper do not produce dry friction damping, relying on the elastic vibration isolation of the wire rope components. The wire rope vibration damper is a new generation of novel elastic components, and its advantages have been gradually recognized by people, and it has been confirmed in practical use in the fields of ships, aerospace and other fields. The prospects for application are very broad. The outstanding advantages are as follows:
(1) The three functions of the elastic support element for vibration isolation, buffering, and reduction of high-frequency structure noise are considered.
(2) Stainless steel wire rope and stainless steel splint are used, which can be used in harsh environmental conditions.
(3) It has stable performance and long life, and generally does not need to be replaced.
(4) Its unique rope structure suppresses high-frequency fluctuation effects that are difficult to avoid with ordinary metal vibration isolators.
(5) It has obvious nonlinear characteristics and has excellent characteristics that cannot be achieved by other vibration isolators in terms of impact resistance and passive vibration isolation.
Wire rope vibration damper produces large dynamic displacements that attenuate strong shocks while absorbing and dissipating large amounts of low frequency and high frequency vibrations. However, the wire rope vibration damper has a small dry friction damping and a poor vibration isolation effect at resonance.
4. Rubber metal isolators
The rubber metal isolator is a new type of vibration isolator. The new type of vibration isolator is made of several steps such as spiral forming, elongation, winding blank, and molding. The internal structure is a spatial network structure formed by interlacing the wires together, and at the same time has the elasticity and damping properties similar to those of the polymer rubber material. When deformed by the load, slippage, friction, extrusion, and elastic deformation occur between the fine metal wire hook chain structures. The dry friction damping dissipates a large amount of vibration energy and acts as a damping buffer. Since metal rubber is a non-continuous pore material, it increases with the number of vibrations under certain conditions. It does not break down like a continuous metal material and fails, but the internal wire breaks locally to cause cumulative damage. Since the metal rubber is made of a spiral metal wire, it not only has the same good elasticity as the rubber material, but also has the characteristics of corrosion resistance, radiation resistance, high and low temperature resistance, corrosion resistance, and aging resistance of the metal material. Therefore, the rubber metal isolator is suitable for use under special environmental conditions. Metal rubber also has the advantages of being easy to be formed into various shapes, various relative densities, light weight, adjustable stiffness, and high dynamic and static strength. At present, rubber metal isolators
are widely used in the fields of automobile ships, aerospace and the like.
5. Air spring isolator
The principle of action of the air spring is to flush compressed air into a sealed container, and the compressibility of the gas reflects the action of the spring. The commonly used air spring isolators consist of a spring body, an additional air chamber and a height controller.