As an installation and protection device for electrical and electronic components, a shipboard cabinet is a typical multiplate structure. In order to study the impact environment distribution laws of such structures, impact testing was carried out on a shipboard cabinet under four working conditions in this paper. In addition, the impact response characteristics of such a multiplate structure were determined by numerical simulation and theoretical analysis. The impact environments of some pivotal points in cabinet were measured and some laws of dynamic response were found. The impact environment of central position was more severe on a single plate because of the first vibration modal. For different plates, the responses were usually similar at low-frequency band and a little different at high-frequency band. The theoretical analysis of the single degree of freedom oscillator was carried out, and the sensitivity of the response to the different characteristic frequencies was discussed based on the shock spectrum theory. A new method of calculating the response at a special frequency was proposed and verified.
With the development of various antiship weapons, a ship’s ability to resist load impact is becoming more and more important in the research of battleships’ viability [
As a typical frame structure, the multiplate cabinet provides impact protection for its internal electric equipment to ensure their normal working. The impact environment in cabinet is closely related to the impact resistance of electronic components and has some specific rules. Since the scale of electronic devices is far less than the scale of cabinet plates, different electronic components in different plates and different positions may experience different impact environments. Shen [
Considering the above, this paper provides a shock test method for shipboard equipment, and the data obtained can be directly used as the impact input for ship-borne electrical equipment. This paper took a shipboard cabinet as the research object and used the impact machine as the loading equipment. The experiments were conducted under four different working conditions, and the impact environment distributions were obtained. At the same time, the impact environment of the electrical equipment of the cabinet was obtained via finite element simulation. This paper provides not only a reference for the research of the impact environment of such frame structure but also the basis for the installation and protection of the ship electrical equipment.
In this paper, a shipboard cabinet was used as the experimental research object. Some electrical components such as control circuit, IGBT component, capacitance, inductance, transformer, and relay were fixed on the cabinet plates by bolts. The electronic cabinet was a frame structure composed of a main frame, front panel, and rear panel. The geometry of the shipboard cabinet is shown in Figure
Programmer of the impact experiment.
Size of the shipboard cabinet.
Length(mm) | a | b | c | d | e |
---|---|---|---|---|---|
400 | 500 | 330 | 430 | 240 |
When testing, the accumulator produced a great power and force impact hammer to move upward. The impact hammer hit on impact table and gave a shock to testing equipment. The applied loads were half sine waves. The buffer cylinder was used to control strength of the loads. Twelve measuring points were chosen, among which 2 points were arranged on the bench table diagonally, 5 points on the bottom plate, and the other 5 on the upside plate. Acceleration sensors were stacked at these 12 points. The whole experimental method is shown in Figure
Arrangement of the impact experiment. (a) Measuring points on the impact table. (b) Measuring points in the cabinet.
According to the experimental requirements of the national military standard GJB1060.1-91 [
The spectrum velocity method is usually used to represent the destructive potential of impact [
It is shown in Figure
Comparison of measuring points 1 and 2 under working condition 1. (a) Acceleration curves with of measuring points 1 and 2. (b) Shock spectrums of measuring points 1 and 2.
For verifying the reliability of the experimental data, an impact simulation was carried out. As shown in Figure
Finite element model of shipboard cabinet.
The results comparison of numerical simulation and experiment.
For exploring the difference of impact environments from edge measuring points to central measuring points, the acceleration curves are compared and shown in Figures
Acceleration curves of edge points under working condition 1. (a) Bottom plate. (b) Upside plate.
Acceleration curves of edge point and central point under working condition 1. (a) Bottom plate. (b) Upside plate.
As is shown in the above figures, the acceleration response of each point in the cabinet shows exponential decay trend. For the bottom plate, there exist many large peaks in the curve of central point. But for the upside plate, there was no obvious difference between the edge measuring points and the central point. That is because the upside plate can be seen as a whole when impact load is transmitted to upside plate. In order to explain the relationship of dynamic response and frequency, the shock spectrums of measuring points are given in Figures
Impact environment in the single plate under working condition 1. (a) Bottom plate. (b) Upside plate.
Impact environment in the single plate under working condition 2. (a) Bottom plate. (b) Upside plate.
As seen in Figures
Not only the impact environment from edge to center in single plate, but also the difference of impact environments of different plates was explored in this paper. The impact environments of measuring points 1, 7, and 12 are compared under four working conditions in Figure
Impact environments of different plates under four working conditions. (a) Working condition 1. (b) Working condition 2. (c) Working condition 3. (d) Working condition 4.
Figure
In order to explore the difference of shock responses of plates, Figure
Model of multiplates frame structure.
The responses of all plates are shown in Figure
Shock spectrums of five plates when frequency of load is 20 Hz. (a) Load with low amplitude. (b) Load with high amplitude.
It can be seen from Figure
Shock spectrums of five plates when frequency of loads is 40 Hz.
In general, the electronic component installed on plate (Figure
The plate and electric equipment.
In this paper, the central position of the plate was simplified as a single degree of freedom system and was loaded with a sine wave of
The shock spectrums are shown in Figure
Response at same specific frequency under different loads.
According to the computing method of shock response spectrum, the spectrum displacement can be obtained by Duhamel integration, thus,
For the undamped system,
Thus, the spectrum velocities were gained
This paper defines
Therefore,
When
The curve of
Actually, the load usually is an irregular wave and can be seen as a composition of infinite sine waves. In this paper, for reducing the computation cost, it was decomposed to 10 sine waves by the empirical mode decomposition method [
In order to prove the theoretical analysis, a comparison of values obtained by the two methods was carried out and the error is shown in Table
Comparison and error of spectrum velocities.
Working condition | 1 | 2 | 3 | 4 |
---|---|---|---|---|
Experimental value (m/s) | 3.65 | 5.34 | 7.95 | 10.84 |
Theoretical value (m/s) | 3.24 | 4.68 | 6.54 | 8.98 |
Error (%) | 11.2 | 12.4 | 17.7 | 17.2 |
From Table
For the purpose of providing impact input for electronic equipment, the impact environment of each plate in the cabinet was analyzed based on the impact experiment and numerical simulation of a certain type of warship cabinet. The following conclusions were drawn. For the bottom plate, no matter how the load is, the impact environment of center on plate is obviously more severe. But for the upside plate, the impact environments of edge points and central point are basically the same. In the cabinet, when the frequency of load is far away from the frequencies of plates, the impact environments of different plates are the same. When the frequency of load is close to the frequencies of plates, the impact environment of the plate whose vibration frequency is most close to frequency of load is most severe. Therefore, when assessing such electrical components, the location should be considered along with the frequency of load. The theoretical analysis of the single degree of freedom oscillator is carried out, and the sensitivity of the response to the different frequencies of load is discussed based on the shock spectrum theory. A new method of calculating the response at the special frequency of plate is proposed and verified.
The data used to support the findings of this study are included within the article.
The authors declare that they have no conflicts of interest.
This study was funded by “Special Fund of the Ministry of Industry and Information Technology, China (No. 2018287).”