JP6432238B2 - Vibration analysis apparatus and vibration analysis method - Google Patents

Description

  The present invention relates to a vibration analysis apparatus and a vibration analysis method.

  Mechanical devices and electronic devices can be damaged by vibrations and shocks. For this reason, it is a common practice to set standards for anticipated vibrations and shocks and conduct tests in advance. Various devices have been developed for performing tests under conditions that satisfy the specifications.

  For example, Patent Document 1 discloses a device that strikes a plate on which an electronic device is mounted and analyzes acceleration data of the plate. In this technique, a vibration system composed of a weight and a spring is added to the plate. Then, by adjusting the spring and the weight, the natural frequency of the vibration system can be set to a predetermined value.

JP-A-3-287045

  However, the impact tester disclosed in Patent Document 1 has a problem that the natural frequencies that can be set are discrete. Since the natural frequency is adjusted by the combination of the spring and the weight, the natural frequency that can be set is naturally limited.

  The present invention has been made in view of the above problems, and an object thereof is to provide a vibration analyzing apparatus capable of continuously adjusting the natural frequency.

  In order to solve the above-described problem, the vibration analyzing apparatus of the present invention adjusts the distance from the rod-shaped column, the fixing unit that fixes a predetermined position of the column, the plate-shaped plate, and the fixing unit. Fastening means for fastening the plate to the column and vibration analysis means for analyzing the vibration of the plate.

  The effect of the present invention is that the natural frequency of the vibration system can be easily adjusted to an arbitrary value.

It is a perspective view which shows the 1st Embodiment of this invention. It is a side view for demonstrating the 2nd Embodiment of this invention. It is a side view which shows the 3rd Embodiment of this invention. It is a side view of another surface of the 3rd Embodiment of this invention. It is a side view which shows the 4th Embodiment of this invention. It is a side view which shows the 5th Embodiment of this invention. It is a top view which shows the 6th Embodiment of this invention. It is sectional drawing which shows the 7th Embodiment of this invention. It is a block diagram which shows the 8th Embodiment of this invention. It is a block diagram which shows the 9th Embodiment of this invention. It is a graph which shows an example of SRS specification. It is a graph which shows SRS of the acceleration waveform of a single frequency.

Hereinafter, the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a perspective view showing the first embodiment. The vibration analysis apparatus includes a rod-shaped column 1, column support means 2 that fixes a predetermined position of the column 1, and a plate-shaped plate 3. The fastening means 4 fastens the plate 3 to the column 1 by arbitrarily adjusting the distance from the fixing means 2. And it has the vibration analysis means 5 which analyzes the vibration of the plate 3. In FIG. 1, the vibration analysis means 5 is depicted as having a sensor of a type that contacts the plate 3, but is not limited to FIG. 1, and various methods can be taken. For example, for the acceleration measurement, mechanical displacement measurement, optical displacement measurement, vibration change measurement, or the like can be used. And the analysis according to each can be performed. That is, the present embodiment is not limited to a specific vibration analysis method.

In the above configuration, the torsion spring constant of the column 1 is changed by adjusting the distance between the column fixing unit 2 and the fastening unit 4. Along with this, the natural frequency in the torsional direction of the support column 1 changes. The longer the distance, the smaller the torsion spring constant and the natural frequency, and the shorter the distance, the larger the torsion spring constant and the natural frequency. That is, it is possible to easily and continuously adjust the natural frequency of the vibration system and analyze the vibration.
(Second Embodiment)
FIG. 2 is a side view of a vibration system for explaining the second embodiment. Here, the distance between the support fixing means 2 and the fastening means 4 (plate 3) is L, the torsion spring constant of the support 1 is k, and the inertia moment of the plate 3 is J. Consider the torsion spring vibration of the column 1 in this system.

Here, when the torsion angle per unit length of the column 1 is θ, the equation of motion of torsional vibration is as follows.

Since this is an equation of simple vibration, it can be solved and the natural frequency f is as follows.

Assuming here that the support column 1 is a homogeneous round bar having a perfect cross section, the torsion spring constant k can be calculated from the torque required to twist the support column 1. k is expressed by the following equation, where G is the elastic coefficient of the column.

That is, the torsion spring constant k is inversely proportional to the distance L. Then, by substituting Equation 3 into Equation 2, the following equation is obtained.

From the equation (4), it can be seen that the natural frequency f is proportional to L ^−1/2 . Therefore, it is possible to adjust so that f is decreased by increasing L and f is increased by decreasing L.

As is clear from equation (4), f can also be changed by changing the column 1 to a material having a different G. If G is increased, f increases, and if G is decreased, f decreases. The material of the support | pillar 1 is various metal materials, such as an aluminum material and steel materials, for example. A material having G suitable for the test can be selected.
(Third embodiment)
FIG. 3 is a side view showing a specific example of the vibration system. The support column 1 is fixed to a support column fixing means 2 fixed to the base surface 6 and supported by guides 7 and 8. The plate 3 is fastened at a distance L from the support fixing means 2 by fastening means 4. A scale 9 is engraved on the column 1. The scale 9 is marked with a mark by printing or marking at regular intervals. By using the scale 9, the adjustment of the distance L is made easier. In this example, the column fixing means 2 is fixed to the base surface 6, and the guides 7 and 8 can move along the base surface 6 at the time of L adjustment. The distance L can be adjusted by adjusting the position of the column 1 held by the column fixing unit 2 and the fastening unit 4.

FIG. 4 is a side view of the vibration system as viewed from the upper surface direction of the plate 3 (the right direction in FIG. 3). A sliding means 10 such as a low friction member or a bearing is provided on the support portion of the guide 8 so as not to hinder torsion of the support. In this configuration, when an impulse 11 directed in the in-plane direction of the plate 3 is applied as shown in FIG. 4, a torsional vibration is generated in the vibration system including the plate 3 and the column 1. This vibration is analyzed by the vibration analysis means 5. At this time, if the specimen 12 is fixed to the plate 3, the vibration and impact tests of the specimen 12 can be performed. As described above, in the present invention, the natural frequency of torsional vibration can be continuously adjusted. Therefore, the impulse 11 and the natural frequency can be adjusted, and the vibration and impact test can be performed under the conditions suitable for the specifications of the specimen 12.
(Fourth embodiment)
FIG. 5 is a side view showing the fourth embodiment. In the present embodiment, the support column 1 is disposed perpendicular to the base surface 6 and the plate 3 is disposed parallel to the base surface 6. In order to prevent the plate 3 from bending due to gravity, the lower portion of the plate 3 is supported by a jack 13. Sliding means 14 such as a low friction member or a ball roller is provided at the upper end of the jack 13 so as not to hinder the movement of the plate 3.

  As shown in FIG. 5, torsional vibration is generated in the torsional direction of the support column 1 by applying an impulse 11 directed in the in-plane direction of the plate 3. Similar to the third embodiment, by adjusting the distance L and impulse 11, it is possible to perform a vibration and impact test that conforms to the specifications of the specimen 12.

In this embodiment, since the plate 3 is arranged in parallel with the base surface 6, workability is good.
(Fifth embodiment)
FIG. 6 is a side view showing the present embodiment. This embodiment is a modification of the fourth embodiment. The guide 7 and the guide 8 support the support 1 so that the support 1 does not move in any direction other than the twisting direction. The guides 7 and 8 are supported by a guide base 15. Although not shown in the figure, sliding means is provided on the support portions of the guides 7 and 8.

In the present embodiment, since the movement of the column 1 other than the twisting direction is suppressed, a test with higher accuracy can be performed.
(Sixth embodiment)
FIG. 7 is a plan view showing this embodiment. In the present embodiment, a specific example of the cross-sectional shape of the column 1 and the fastening means 4 of the plate 3 is shown. The fastening means 4 has a split fastening structure having a gap 16 and a split 16 into which the support column 1 is substantially fitted. The plate 3 is fastened to the column 1 by fitting the column 1 into the gap and narrowing the split 16 with the bolt 17.

  7A shows an example in which the cross section of the column 1 is circular, FIG. 7B shows an ellipse, FIG. 7C shows a rectangle, and FIG. 7D shows a polygon (octagon). When the cross section of the column 1 is circular as in (a), there is no local concentration of stress. In addition, it is easy to calculate the moment of inertia, torsion spring constant, natural frequency, and the like. Therefore, a highly accurate test can be performed. On the other hand, there is a risk that the fastening will shift if a large impulse is applied. On the other hand, in the case of FIGS. 7B, 7 </ b> C, and 7 </ b> D, there is an advantage that the fastening is not easily shifted even with a large impulse. In addition, although a solid (homogeneous to the inside) support | pillar was illustrated here, a hollow support | pillar may be sufficient. Moreover, it is also possible to use the support | pillar with cross sections, such as L shape and H shape.

If the cross-sectional shape is complicated, the torsion spring constant and the natural frequency may not be calculated, but the relationship between the length L and the natural frequency may be obtained from an experiment. Since there is no change in the characteristic that the natural frequency f decreases as L increases, f can be continuously adjusted by adjusting L in this case as well.
(Seventh embodiment)
FIG. 8 is a cross-sectional view showing a seventh embodiment. The vibration analysis apparatus according to the present embodiment has a mechanical lock 18 as the fastening means 4. The mechanical lock 18 includes an inner ring 18a, an outer ring 18b, and a bolt 18c.

  The outer ring 18b is fitted to the counterbore of the plate 3, the inner ring 18a is fitted to the outer ring 18b, and the bolt 18c is tightened in a state where the column 1 is passed through the inner ring 18a. Is done.

  According to the present embodiment, since the plate 3 can be firmly fastened to the support column 1, the accuracy of vibration and impact tests can be increased. It should be noted that the fastening strength is slightly reduced, but the counterbore of the plate may not be provided.

In the sixth and seventh embodiments, two specific examples of the fastening means 4 are illustrated, but the fastening means applied to the present invention is not limited to this, and a known technique can be applied as appropriate.
(Eighth embodiment)
FIG. 9 is a block diagram showing the eighth embodiment. In the present embodiment, specific configurations of the vibration analyzing means 5 and the entire vibration analyzing apparatus are shown. As the vibration system, the column 1, the plate 3, and the fastening means 4 are provided as in the other embodiments. The vibration analysis unit 5 includes an acceleration pickup 19, a data collection unit 20, and a data analysis unit 21. The vibration analysis apparatus also includes impulse input means 30 for inputting impulse 11 to the plate 3.

  The impulse input means 30 applies an impulse 11 directed in the in-plane direction to the plate 3. The impulse input means 30 is, for example, a hammer, a collision object, a vibration generator, or an explosive.

  Although not shown, the impulse input portion on which the plate 3 receives impulses may be provided with various metal materials, resin materials such as rubber and plastic. It is possible to change the impulse input time by changing the material of the impulse input portion.

  The acceleration pickup 19 generates a signal corresponding to the acceleration of the plate. For measurement of acceleration, mechanical displacement measurement, optical displacement measurement, vibration change measurement, or the like can be used.

  The data collection unit 20 accumulates the signal acquired by the acceleration pickup 19 in the memory. Moreover, analog-digital conversion etc. are performed as needed.

  The data analysis unit 21 performs vibration analysis based on the signal received from the data collection unit 20. The vibration analysis unit 21 is realized by a computer such as a personal computer, and can include a display unit and other input / output units.

According to the present embodiment, it is possible to configure the vibration analysis device using general-purpose components and devices.
(Ninth embodiment)
FIG. 10 is a block diagram showing the ninth embodiment. The present embodiment has the same basic configuration as the eighth embodiment. And it is the structure suitable for a shock response spectrum (Shock Response Spectrum, SRS) test. For this purpose, the impulse input means 30 has an impact force input means 31 for inputting an impact force. The vibration analyzing means 21 has an SRS analyzing means 22.

  Here, SRS will be described. An electronic device that receives a large impact such as a satellite-mounted device needs to be evaluated for impact resistance. For this evaluation, a method expressed by SRS is used.

  SRS is expressed by a horizontal axis frequency and a vertical axis acceleration. The SRS for a predetermined impact acceleration waveform is obtained by the following procedure. First, a predetermined shock acceleration waveform is applied to a one-degree-of-freedom spring / mass / damper system having a certain natural frequency, and the maximum acceleration generated at this time is obtained. Next, the maximum acceleration generated when the same shock acceleration waveform is applied to a one-degree-of-freedom spring / mass / damper system having another natural frequency is obtained. SRS is obtained by performing similar calculations for various natural frequencies, and plotting the natural frequency on the horizontal axis and the maximum acceleration on the vertical axis. For example, when the SRS indicates 1000 G at 1000 Hz, the impact means that a maximum acceleration of 1000 G is applied to the mass portion of the one-degree-of-freedom spring-mass-damper system having a natural frequency of 1000 Hz.

  FIG. 11 is an example of the SRS specification. Such SRS specifications are given in three directions of X, Y, and Z. In the SRS specification, the inclination, the break frequency, the maximum acceleration, and the width called tolerance are mainly designated. This specification is obtained in advance by experiment and analysis. In the impact test, an impact that satisfies the test specification is generated and the test is performed.

  Although it has been stated that the SRS specification is specified by inclination, bending point frequency, and maximum acceleration, these values are determined by the impact waveform. In particular, the break frequency is determined by the dominant frequency of the shock waveform. As an example, an SRS of a single frequency acceleration waveform is shown in FIG. Here, an example of an acceleration waveform having an acceleration amplitude of 1 G and a vibration frequency of 800 Hz (FIG. 12A) and an SRS waveform at that time (FIG. 12B) is shown. When different breakpoint frequencies are specified as test specifications, it is necessary to change the shock frequency.

  Next, an impact test procedure based on the SRS specification will be described. Here, it is assumed that the support column 1 is a solid round bar with a perfect cross section.

  1) First, the break frequency is read from the SRS of the test specification. Let this frequency be fa.

2) Next, an adjustment specimen having the same mass as that of the specimen 12 is fixed to the plate 3. The distance L _b of the fixing means 2 and the fastening portion 4 at this time is recorded. Then, using equation (3) of the second embodiment, to calculate the torsion spring constant k _b at this time.

  3) Thereafter, the impact force of the test specification is applied to the impact input portion of the plate 3 by the impact force input means. As an impact input method, for example, a collision object such as a hammer or a bullet is collided, or an explosive is installed in an impact input unit to cause an explosion.

4) Next, the frequency _fb and the maximum acceleration are calculated from the actually measured data. The frequency is calculated by, for example, fast Fourier transform. Then, using the equation (2) of the second embodiment, the moment of inertia J including the specimen for adjustment is obtained.

5) Substituting the obtained J and the target natural frequency f _a into equation (2) of the second embodiment to obtain _a torsion spring constant ka for realizing f _a .

5) Next, La for realizing k _a is obtained using Equation 3 of the second embodiment.

  6) Next, the distance L between the support fixing means and the fastening means is adjusted so as to be La.

  7) Next, an impact force is applied to the plate 3 again to confirm that the frequency is the target frequency fa.

  8) Next, the specimen for adjustment is replaced with the specimen 12 to be tested and fixed to the plate 3, and an impact test is performed. Thereby, the impact test is completed.

  As described above, according to the present embodiment, the test can be performed by adjusting the test conditions so as to match the SRS specifications.

  In addition, when the cross section of the support | pillar 1 is other than a perfect circle, the same adjustment can be performed by calculating each suitable, or calculating | requiring the relationship between L and f experimentally.

  The present invention has been described above using the above-described embodiment as an exemplary example. However, the present invention is not limited to the above embodiment. That is, the present invention can apply various modes that can be understood by those skilled in the art within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 support | pillar 2 support | pillar fixing means 3 plate 4 fastening means 5 vibration analysis means 6 base surface 7, 8 guide 9 scale 10 sliding means 11 impulse 12 specimen 13 jack 14 sliding means 15 guide base 16 split 17 bolt 18 mechanical lock 19 acceleration pickup 20 data collection means 21 data analysis means 22 SRS analysis means 30 impulse input means 31 impact force input means

Claims (8)

A rod-shaped column and fixing means for fixing a predetermined position of the column;
A plate-shaped plate;
Fastening means for adjusting the distance from the fixing means to fasten the plate to the support;
Vibration analysis means for analyzing the vibration of the plate;
A vibration analysis device comprising impulse input means for inputting impulse in an in-plane direction of the plate . The column has a circular cross-sectional shape;
The vibration analysis apparatus according to claim 1. The column has an elliptical or polygonal cross-sectional shape;
The vibration analysis apparatus according to claim 1. It has a guide that suppresses movement other than the torsional direction of the column,
The vibration analysis apparatus according to any one of claims 1 to 3, wherein Plate support means for supporting the plate with low friction;
The vibration analysis apparatus according to any one of claims 1 to 4, wherein the vibration analysis apparatus according to any one of claims 1 to 4 is provided. The impulse input means includes impact force input means;
The vibration analysis means has SRS analysis means;
The vibration analysis apparatus according to any one of claims 1 to 5, wherein the vibration analysis apparatus according to any one of claims 1 to 5 is provided. Fix the predetermined position of the rod-shaped support,
Adjust the distance from the predetermined position to fasten the plate to the column,
Input impulse in in-plane direction of the plate
A vibration analysis method comprising analyzing vibrations of the plate. An impact force is input in the in-plane direction of the plate to perform SRS analysis.
The vibration analysis method according to claim 7.

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