The Concept of Vibration Reduction and Isolation
is the main means to prevent vibration hazards in engineering. Vibration reduction can be divided into active vibration reduction and passive vibration reduction. Active vibration reduction considers eliminating or reducing the energy or frequency of vibration sources when designing. It is widely used in precision instruments, aerospace equipment, large turbogenerator units and high-speed rotating machinery, but it is expensive and seldom used in general construction machinery. Passive vibration reduction includes vibration isolation
and absorption. Vibration isolation can be divided into active vibration isolation and passive vibration isolation.
In order to prevent or limit the harm and influence caused by vibration, various measures have been adopted in modern engineering, which can be summarized as follows:
1. Reducing or eliminating vibration sources (active vibration reduction)
This is a positive radical measure. If the vibration is caused by the eccentricity of the rotating parts, the unbalanced centrifugal inertial force can be reduced by improving the accuracy of dynamic balance. For reciprocating machines such as air compressors, attention should also be paid to the balance of inertia force.
2. Away from the source of vibration (passive isolation)
This is a negative protective measure. For example, precision instruments or equipment should be as far away as possible from factories or workshops with large power machinery, pressure processing machinery and vibration machinery, as well as busy railway and highway transportation.
3. Improve the anti-vibration ability of the machine itself (active vibration reduction)
Dynamic stiffness is a common index to measure the anti-vibration ability of machine structures. The dynamic stiffness is equal to the dynamic force required for generating unit amplitude of machine structures. The greater the dynamic stiffness, the smaller the vibration of the machine structure under the dynamic force.
4. Avoid Resonance Zone
According to the actual situation, the natural frequency of the system (active vibration reduction) or the working speed of the machine (passive vibration reduction) can be changed as far as possible, so that the machine does not work in the resonance zone.
5. Adequate increase of damping (damping and vibration absorption)
Damping the energy absorbed by the system can rapidly attenuate the amplitude of the free vibration and restrain the amplitude of the forced vibration, especially in the resonance region.
6. Dynamic Vibration Absorption (Passive Vibration Absorption)
For some measuring or monitoring instruments on some equipment, the method of installing dynamic vibration absorber under the instrument can stabilize the instrument's pointer and improve the measurement accuracy.
7. Vibration isolation measures
A flexible isolator is used to isolate the vibration machine (vibration source) from the ground so as to reduce the influence of the vibration source on the surrounding equipment through the ground, that is, active vibration isolation or active vibration isolation; or the precise equipment to be protected from the vibration of the ground, so as not to be affected by the surrounding vibration source, that is, passive vibration isolation.