Dynamic analysis of a marine electronic display an

2022-10-15
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Dynamic analysis of a marine electronic display and control console

Abstract: the finite element model of a marine electronic display and control console is established by using the finite element method. Through modal analysis and calculation, the vibration modes and natural frequencies of each order are obtained, and the vibration resistance is analyzed according to the calculation results. Some of the conclusions have certain reference value for engineering design

key words: electronic display and control console; Finite element method; Modal analysis

1 Introduction

as a marine electronic equipment, the electronic display and control console will inevitably be affected by various mechanical forces such as vibration and impact in the actual working environment. They may cause instability in the working state of the electronic display and control console, or damage the whole equipment. Therefore, anti vibration and buffer design is an important part of the structural design of marine electronic display and control console. At present, in the anti vibration design of marine electronic display and control console, various engineering research and development units have mastered some more feasible design methods, but generally speaking, they still stay in the empirical design, and carry out a more perfect theoretical analysis on the anti vibration design of electronic display and control console. Some design methods and test means also lack theoretical basis. For example, in engineering applications, the final inspection of the vibration resistance of the electronic display and control console mainly depends on routine tests. In general, when doing vibration test on the electronic display and control console, the test sensor is placed outside the cabinet with good rigidity. In fact, the test data measured by this method can only reflect the overall vibration of the electronic display and control console, and can not truly reflect the anti vibration performance of its internal structural parts. In fact, the internal structure of the electronic display and control console is relatively complex, and there are at least thousands of elements in the experimental force measurement range of 1% - 100% (equivalent to 5 gears). Moreover, the rigidity of its internal mechanical structural parts is also very different. If the rigidity of some parts is not good, the vibration produced by these parts in the future may cause fatigue damage to the electronic components installed on them, resulting in the failure of the equipment to work normally

therefore, a deeper understanding of the stiffness of the cabinet and its internal main components through the method of theoretical analysis has a positive guiding significance for the structural design of the electronic display and control console. In this paper, the finite element method is applied to the modeling and modal analysis of an electronic display and control console. Finally, the vibration resistance is analyzed according to the calculation results

2 structural form of electronic display and control console

the electronic display and control console analyzed in this paper is a naval shipborne tactical platform, which is composed of four units, from top to bottom are raster scanning display and operation console, which are connected to the side wall of the disk, and there are 10 or 6 slot receivers and computers with different widths. Among them, the raster scanning display, receiver and computer are plug-in boxes, which can be pulled out by the guide rail installed inside the cabinet to facilitate maintenance. The operation console is an independent part, which is firmly connected with the cabinet by screws

the cabinet of the electronic display and control console adopts a plate structure of aluminum alloy casting, which is common in the installation equipment of naval ships at present. The framework of this cabinet is mainly composed of four parts: top box, base, left board and right board. They are all made of aluminum alloy and machined. Finally, 12 M12 screws are used to rigidly connect the two side plates with the top box and the base to form a cabinet, as shown in the figure manufacturing and manual assembly of the dual fuselage vehicle as the air launch platform 1. The main characteristics of this structural form are good strength, high rigidity, flat, beautiful and good processability outside the cabinet, which is suitable for single piece and small batch production of military products

the three plug-in boxes of the electronic display and control console are made of aluminum alloy plates. The weight of the three plug-in boxes is 65kg for the upper plug-in box, 8kg for the middle plug-in box and 20kg for the lower plug-in box. The operation console is of aluminum alloy casting structure, with a weight of 14kg. In addition, a wire support plate is installed between the upper plug-in box and the middle plug-in box, and between the middle plug-in box and the lower plug-in box. The supporting plate is made of 2mm thick rolled steel sheet, with flanging all around. The left and right sides are respectively fastened with the left and right plates of the cabinet with screws. The back of the cabinet is equipped with a rear cover plate. The rear cover plate is also made of 2mm thick steel plate, with stiffeners in the middle, and is connected with the cabinet frame by screws around

the total weight of the electronic display and control console is 260kg, and a total of six GF Yazhen brand composite damping vibration isolators produced by the state-owned 612 factory are selected. Four of them are installed at the bottom of the cabinet with a rated load of 700n, and two are installed at the upper position of the back of the cabinet with a rated load of 500N. The outline of the electronic display console is shown in Figure 2

3 establishment of finite element model of electronic display and control console

as mentioned above, the electronic display and control console is mainly composed of four extensions and cabinet skeleton. In the process of establishing the finite element model, this paper strives to maintain the geometric characteristics of the original structure and improve the authenticity of the analytical mechanics model. Therefore, following the principle of mass and inertia equivalence, the electronic display and control console is simplified into a composite structure with beam, rod and plate elements. The simplified finite element model of the electronic display and control console has 593 nodes, 3558 degrees of freedom, and 15 groups of elements. The finite element model is shown in Figure 3

4 structural modal analysis of electronic loss display platform

after the above data is prepared, modal analysis and calculation are carried out with finite element analysis software, and the first 100 natural frequencies and vibration modes are intercepted. Some typical vibration modes are shown in Figure 4. By analyzing the vibration mode diagrams one by one, the deformation position and frequency range corresponding to each mode of the electronic display and control console can be obtained (see Table 1)

5 analysis of vibration isolation effect of electronic display and control console

after the above modal analysis, the first 100 main modes are intercepted, and their frequency range is 2.38 ~ 113.8hz, with frequency intensive characteristics. It can be seen from the vibration mode diagram and table 1 that the first to eighth modes of the electronic display and control console (frequency range 2.38 ~ 8.3Hz) correspond to the deformation of the vibration isolator, which proves that the natural frequency of the composite damping vibration isolator is low, which is beneficial to the impact resistance of the electronic display and control console. According to the basic theory of vibration isolation transmissibility, the vibration isolator has no vibration isolation effect on low-frequency foundation excitation lower than 8.3 [KF (]2[kf)]hz, and has vibration isolation effect on excitation higher than 8.3 [KF (]2[kf)]hz. The weakened high-frequency vibration will still cause local resonance in the plug-in box, wire support plate and other structures. Special attention should be paid to such structures with dense natural frequencies. Therefore, in the anti vibration design, we should make full use of damping to suppress the resonance. (in fact, the damping of the vibration isolator in the resonance region is very large, which basically ensures that the amplification factor is less than 3)

the 9th to 18th order modes (frequency range 11.9 to 17hz) of the electronic display and control console correspond to the deformation of the wiring board and plug-in box inside the cabinet. Their natural frequencies are low and their stiffness is poor. The reason is that the supporting plate is made of 2mm thick rolled steel sheet, with a large area of about 620mm × 500mm, and there is no stiffener in the middle. Compared with the middle and lower plug-in boxes, the upper plug-in box has larger volume and mass, so its rigidity is weak

the 22nd mode corresponds to the deformation of the rear cover plate, and its natural frequency is 25Hz. Although both the rear cover plate and the wire support plate are made of 2mm thick steel plates, the stiffness of the rear cover plate is greatly improved due to the arrangement of stiffeners on the rear cover plate. The natural frequency of its corresponding mode is 13Hz higher than that of the corresponding mode of the support plate. It can be seen that the use of stiffeners plays an important role in improving the rigidity of mechanical structural parts

the modal number corresponding to the deformation of the top box is greater than 27 orders. The natural frequency of its corresponding mode is greater than 30.9hz. The modal number corresponding to the deformation of the base, side plate, console, etc. is greater than 39 orders, and the natural frequency corresponding to its modal is greater than 41.5hz. To a large extent, the improvement of the rigidity of such members also depends on the longitudinal and transverse stiffeners arranged on their walls

based on the above analysis, the following conclusions can be drawn:

(1) when designing the anti vibration performance of marine electronic display and control console, full attention should be paid to the selection of vibration isolators. Only selecting vibration isolators with excellent performance can ensure the normal operation of the electronic display and control console in various frequency ranges. Due to its low natural frequency and large damping in the low-frequency resonance region, GF composite damping vibration isolator is a kind of vibration isolator with good performance that can be selected for marine electronic display and control console at present

(2) the electronic display and control console analyzed in this paper adopts the cabinet in the form of aluminum alloy casting, which has good rigidity, and the natural frequency of the corresponding mode of its skeleton is above 30Hz. The rigidity of the cable tray and the plug-in box inside the electronic display and control console is poor, and the natural frequency of the corresponding mode is about below 17hz, so measures need to be taken to improve the rigidity. For example, the stiffness can be improved by setting stiffeners on the wire support plate and each plate of the upper plug-in box

references

1 division Zhang Azhou, Yao Qihang, etc Vibration control engineering Beijing: Aviation Industry Press, 1989, 12 ~ 13

2 Dai Depei Engineering application of damping technology Beijing: Tsinghua University Press, 1991, 157 ~ 158

3 Gan Shunxian Finite element technique and program Beijing: Beijing University of Technology Press, 1988, 243 ~ 299

4 Gou Houyu Compound damping vibration isolator Noise and vibration control 1986, 8 (4):20 ~ 27

5 state owned 612 factory Yazhen brand compound damping vibration isolator product manual 1994(end)

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