The damping and vibration reduction design of electronic equipment is based on the working environment conditions of the instrument and equipment, some special requirements of itself and the possibility and reality of implementing these requirements. By making use of the relationship between the parameters of damping structure and each other, the main parameters are adjusted properly. The damping and damping design can be roughly summarized as follows:
1. Determine the type of structural damping and the damping form of the whole machine.
2. Determine the elastic element material of damping structure.
3. Determine the viscoelastic damping material.
4. Estimate and measure the dynamic characteristics of damping structure.
In modern electronic control equipment, the whole system is designed for structural damping, which is usually designed for hierarchical structure damping. This is mainly based on the characteristics of some modern electronic control equipment, such as small size, light weight, good air tightness, high reliability, complex and variable shape. The so-called hierarchical structure damping design treatment means that the structural damping design treatment is carried out for several key parts of the whole instrument, or the whole instrument is composed of several damping structural parts. Thus, the vibration response of each important part of electronic equipment is limited within the allowable range.
（1） The first stage damping system of the base plate of the rectangular damping structure
The design features of the damping system are: simple, economic, easy to operate, and has good damping effect. It is suitable for the design of electronic control instruments with moderate protection requirements for broadband random vibration. The concrete method is: on a multi-layer damping structure base plate composed of three layers of Constrained Viscoelastic Damping material and four layers of aluminum alloy Mei. Install a cast aluminum structure instrument shell, and install important components such as printed circuit board in the shell. Since a damping structure base plate is added at the bottom, a considerable part of the vibration energy can be dissipated through it, so the resonance transmission rate of the basic vibration mode of the instrument with damping base plate can be reduced by 4? 5 times compared with that without damping base plate. In addition, the damping base plate reduces the resonance frequency of the instrument system, so it has a good isolation effect on the excitation frequency greater than 110hz. The vibration damping effect in X and Z directions is also ideal. In addition to the above characteristics, the electronic system with damping structure base plate for the first stage damping and vibration reduction can easily maintain the independent sealed shell structure of the instrument, provide a good working environment for the electronic system, and further improve the working reliability of the instrument. Many electronic instruments and equipments use polymer damper to isolate vibration
（2） Multi stage damping system of four ear damping structure base plate
The main feature of the design of multi-level damping system is that it can limit the maximum vibration transmission rate to about 2, which can improve the working environment of the instrument to the greatest extent. The specific method of damping treatment of printed circuit board for electronic equipment is to paste a certain thickness of damping material on the non printed circuit surface of ordinary printed circuit board (as the base), and then paste a piece of damping material the same as the base material By comparing the vibration data of PCB before and after damping treatment, it can be clearly seen that the resonance frequency is reduced from 400Hz to 220hz, and the resonance transmission rate is reduced from the original 18 to 3.2, which provides an ideal working environment for electronic components and improves the damping effect of electronic equipment system.
There are two types of PCB structure for electronic equipment: symmetrical type and asymmetric type. They are mainly different damping measures according to the specific situation and needs of engineering design. Due to the limitation of the internal space of the equipment, the printed circuit board installed with electronic components should adopt asymmetric damping structure. The loss factor of asymmetric damping structure is almost the same as that of symmetric damping structure, that is to say, there is no significant difference in the vibration transfer rate between them. It is very convenient for our design work to use this feature skillfully sometimes
（3） Integrated application system of structural damping and USS reduction
The comprehensive application of viscoelastic shear damping and shock absorber is also one of the effective methods to control vibration. It can also make modern electronic equipment have the ability of highly controlling vibration and impact in the whole frequency range of excitation frequency, and provide a better working environment for electronic equipment. Here are some examples;
1. Local damping treatment and comprehensive application of shock absorber
There are often such cases, some modern electronic control equipment, their own volume and weight are not large, but they are in a very bad mechanical environment, so effective vibration control measures must be taken. However, the shape and installation of these equipment are very special. If only using structural damping treatment, it is more difficult, and there is no more effect on the further reduction of equipment volume and weight. However, the volume and weight of the small shock absorber system are not increased much, which is easy to realize, but the resonance control ability is poor. Therefore, it is an appropriate way to control the vibration of these equipments by using the local structure of shock absorber to damp the comprehensive structure. This shows that damping is not the only effective method of vibration control. In the vibration design of modern turn mill equipment, flexible and effective measures should be taken according to different situations. The typical system of comprehensive application of local structural damping of shock absorber Qi is shown in Fig. 60. It takes the instrument shell as the lacquer reducer bracket (structural damping treatment is adopted, so the vibration excitation degree of the isolated part of K57 is different, and the vibration environment is relatively improved. Several damping structure printed circuit boards are hung in the vibration isolation system composed of four small rubber shock absorbers through the combination of support probes (both stiffness and mass are not large), which provides good resonance control and high frequency vibration isolation ability for electronic equipment, reduces multi peak resonance response, and improves the j working ring Environment, to meet the needs of engineering design.
Damping is one of the main technical measures for vibration protection of modern electronic control equipment. It is necessary to use damping technology in modern electronic equipment, and its damping effect is remarkable.
In order to obtain the best damping effect, the ideal damping material with a high loss factor of 8 and a proper shear modulus of G should be possessed first. In addition, the optimal damping design must be made. Therefore, it is necessary to adjust some parameters properly to achieve the purpose of all design requirements by pre calculation and analysis, using the relationship between parameters in damping structure design.
When evaluating the design effect of a damping system, although the magnitude of the system loss factor and the control ability of the system vibration transmission rate are some main indexes, it is not allowed to regard obtaining the maximum composite structure damping as the only criterion, but should be measured comprehensively and considered comprehensively. For example, in addition to comprehensive consideration of the loss factor gate of the structure, the shear parameter X. , geometric parameter Y, optimal design parameter (besides, the ambient temperature and boundary conditions shall not be neglected. Although the half width temperature at0.7 is required to be as large as possible when choosing damping materials, the temperature range that can effectively dissipate the vibration kinetic energy is still limited. In addition, with the different boundary conditions, the effect of the damping characteristics of the structural system is not the same, so the optimal temperature range, the optimal frequency range, certain boundary conditions, as high as possible damping, appropriate strength and rigidity must be considered in the design of damping structure The degree and weight factors are optimized so that 'the best damping effect can be achieved.
The test and engineering design practice also proved that the comprehensive use of damping vibration reduction technology and vibration isolation technology, foam plastic damping and various forms of dampers and damping pads can also achieve ideal vibration control effect under certain conditions.