Vibration analysis and damping design method of electronic equipment

Vibration Analysis and Vibration Reduction Design Methods of Electronic Equipment Lin Jie Seventh Research Institute Fuyang 3400, Zhejiang Abstract This paper analyzes the motion laws of passive vibration isolation of electronic equipment and proposes several specific methods for vibration reduction design.

1 Introduction Electronic equipment in the actual working environment will be subjected to various forms of mechanical force, such as vibration and centrifugal force and friction caused by the movement of the mechanism. Among them, the most harmful to electronic equipment is vibration and shock. This article will discuss the harmful motion law of vibration in combination with the actual work, and put forward several specific vibration reduction design methods.

2 Harm of vibration Electronic equipment will resonate under certain excitation frequency, and its amplitude will become larger and larger. Finally, the electronic equipment will be destroyed due to the vibration acceleration exceeding the device's limit acceleration or the equipment will be damaged due to the long-term stress caused by vibration acceleration Fatigue damage. No matter what kind of cause of equipment damage, the final result will lead to the failure of electronic equipment functions, thus causing the entire equipment to malfunction and fail to work properly.

3 Analysis of passive vibration isolation of electronic equipment When electronic equipment is working, the vibration of the working environment can be regarded as the basic excitation for the equipment. The following is the rigidity of the electronic equipment exempt from vibration isolation device; the damping coefficient of the system.

Assuming that the excitation mode is a differential equation of motion, the normalized equation of the above formula is the general solution of substituting 1 into 3 and 4 with 4 as the general solution where 21 is the transient solution of the equation and 22 is the steady-state solution of the equation. Using the complex modulus operation, the amplitude is the transmission rate, where 2 = 0 claws, = .2; the damping coefficient can be drawn by the formula 7; 7 curves, 2. It can be seen that no matter what the value is, the 77 curve has two of 771 At frequency, 7 is called the vibration isolation zone.

At 0.81.1, it is called the resonance zone. In this interval, an increase in the damping ratio of 0 is beneficial to suppress resonance. When the value tends to infinity, there must be 1. in the 71 interval.

After 7, the damping ratio is increased, which is harmful to the vibration isolation effect.

This is due to the increased resistance transmitted through the damper. Therefore, when 5 = 0 in the vibration isolation area, there is a minimum transfer rate of 77. From the above discussion, it can be concluded that the stiffness of the vibration isolator of the ideal vibration isolation transmission rate of the vibration isolation system should be as low as possible, so that it can enter at a lower frequency Vibration isolation area.

Vibration isolators have variable damping characteristics, in the range of 071, make 7 1; and when Wan enters the vibration isolation zone, it should be made to approach the curve with this transmission rate characteristic to 7, called the resonance-free peak transmission rate curve, its transmission Rate curve 3.

4 Commonly used vibration damping design methods for electronic equipment in order to prevent vibration from harming electronic equipment. Vibration damping design is usually considered in the design. Commonly used vibration damping design methods include vibration isolation design structure rigid design decoupling design and damped structure design.

4.1 Vibration isolation design Vibration isolation buffer devices are used to reduce or avoid the harmful effects of the external environment on electronic equipment for large and medium-sized electronic equipment, which is a cost-effective and effective measure. The principle of vibration isolation can be explained clearly in the previous analysis of the motion law, so it will not be repeated here. There are many types and models of vibration isolators. Here is a kind of commonly used vibration isolator without resonance peak vibration isolator. It is a new type of vibration isolator designed according to the variable stiffness and damping characteristics required by the vibration isolation buffer technology. It adopts stiffness fitting technology and dry friction damping technology to achieve a low inherent Frequency, no resonance amplification, and can take into account the buffer function. The test proves that the electronic equipment using this vibration isolator has no resonance points in the vertical, left and right, front and back directions. The stability is good in the stability check. In the vibration resistance test and the shock vibration test, the equipment performance is normal, and the test result reaches National standard and military standard requirements.

4.2 Rigid structure design The excitation frequency of the working environment usually ranges from a few Hz to a few tens of Hz. In order to keep the natural frequencies of electronic devices and components away from the resonance region, we can increase the natural frequency of the product structure by enhancing the rigidity of the product, and make the vibration isolation transmission rate close to 7 so that the device can work normally. In fact, the reinforcement design of the weak links of electronic equipment commonly used in engineering is to strengthen the rigid design of the product structure. Of course, the whole welding of the cabinet frame can also be adopted; the wires in the cabinet are braided up and fixed in sections with wire clips; the leads of the resistance-capacitance components are cut and welded; the reinforcing ribs and locking devices are used for the printed boards in the electronic equipment In other ways, to increase the rigidity of the structure to achieve the purpose of vibration reduction, for example, after experimental comparison and practical application, the number of reinforcement ribs and the frequency of the installation side are found. 44 kinds of schemes, after experimental testing, their natural frequencies from small to large are scheme 1 scheme 2 scheme 3 scheme 4.

4.3 For designing electronic devices are equipped with many components. In addition to the natural frequency of the device itself, each component has its own frequency.

During the vibration, there will be coupling between each other, so that the natural frequency distribution is very wide. Therefore, in the design, consideration should be given to making the component structural parts evenly distributed so that the center of mass and the center of rigidity coincide to achieve the purpose of vibration reduction. For example, the position of the components on the printed board is reasonably arranged so that the components are evenly distributed. 5. The natural frequency of the printed board of Scheme 2 is obviously higher than that of Scheme 1.

Scheme 2 Damping material. In this way, when vibrating, the intermediate layer produces periodic shear strains, so that the mechanical energy becomes thermal energy to obtain high damping characteristics. In addition, in the electronic equipment, the vibration of the fan will generate noise. You can use rubber pads on the surface of the fan and the chassis to reduce the noise by controlling the vibration.

4.4 Adopt damped structure According to statistics, half of the failure resistance capacitance of electronic equipment is caused by the resonance of the printed substrate, not at their own resonance frequency.

In order to overcome the above-mentioned shortcomings, the printed substrate currently uses a layered structure, that is, a viscous 5 concluding measure is sandwiched between the layers. Through the vibration reduction design, the anti-vibration ability of the electronic device is improved, thereby also improving the reliability of the electronic device.

1 Wang Hongfang. Zhao Mei, Xu Xiao, Shi Zhaochang. Improvement of printed board structure based on dynamic characteristics. Vibration and Shock, 2000, 1912 Ji Xin. Vibration analysis and testing of electronic equipment. Nanjing Southeast University Press, 1992 3 Fu Zhifang. Vibration modal analysis and parameter identification. Beijing Machinery Industry Press, 1990 4 Nanjing Institute of Technology. Electronic equipment structure design principles. Nanjing Jiangsu Science and Technology Press, 1983

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