JPH02141626A - Method for measuring vibration mode - Google Patents

Abstract

PURPOSE:To measure the two-dimensional vibration mode generated on a vibration surface by exciting an object by imparting damping properties thereto to optically detect infrared emitting energy emitted from the object and displaying the temp. change of each part of the vibration surface as a heat image. CONSTITUTION:A pasty damping material 12 based on an epoxy resin is built up on one surface of an iron plate (300X32X5mm) in a uniform thickness (5mm) and this iron plate is used as a sample plate and the central part thereof is horizontally mounted on an exciter 14 by a rivet 13 and a thermotracer 15 is arranged just above said exciter 14. The sample plate is excited at the resonance frequency of the bending moment thereof and the heat image obtained on the picture 16 of the tracer 15 is visually observed. For example, when the frequency of 1,218Hz corresponding to the secondary bending mode of the sample plate is applied to the sample plate 11 for 10min under gravity of 150G, a red color appears on the central region and the regions on both sides thereof of the sample plate and a yellow color appears between the red regions and both ends show a green color. That is, the loop part of a vibration waveform large in displacement appears at two places and a typical vibration secondary mode is clearly displayed on the picture 16 by a color change.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for visually measuring vibration modes caused by vibrations applied to structures or materials.

[Conventional technology]

fiM is the best way to know what the vibration mode of a structure or material looks like when it is vibrated! This is extremely important in the design of the artifact.

Conventionally, there has been no method for directly detecting vibration modes; for example, in order to measure the vibration modes occurring in a structure, acceleration sensors are attached to various locations on the surface of the structure, and the measurement is carried out by so-called multi-point measurement. This method collects the measured values obtained at each measurement point, performs Fourier transform on the data, and analyzes the vibration mode of the vibration surface using modal analysis through software processing.

[Problem to be solved by the invention]

Therefore, when using the above method, it is necessary to use a large number of acceleration sensors or perform large-scale numerical processing by repeatedly measuring each point, and the measurement work is complicated, such as installing sensors and wiring cables to acquire data. There are drawbacks that are extremely troublesome.

Moreover, the data obtained is limited to instantaneous data or when vibration is applied regularly for a long period of time, and it is not possible to follow vibrations that change from moment to moment.

On the other hand, the finite element method is known as a method for determining vibration modes through calculations, but this is only a simulation, requires a large amount of numerical calculations, and is not accurate to the actual vibration modes that occur in the target structure. In many cases, they do not necessarily match.

The purpose of the present invention is to solve the above-mentioned problems and to reduce the
The object of the present invention is to provide a method for visually measuring dimensional vibration modes.

[Means to solve the problem]

In order to achieve the above object, in the vibration mode measurement method according to the present invention, at least a part of an object including a structure or material whose vibration mode is to be measured is vibrated with damping properties, and The system optically detects the emitted infrared radiation energy and displays the distribution of temperature changes at various parts of the vibrating surface as a thermal image, which corresponds to the vibration mode and is used to dampen vibrations on the object's surface.

[Principle/effect]

If the vibrations that occur in a sample when it is vibrated are converted into thermal changes, the magnitude of the vibrations can be measured as the amount of thermal change. Objects emit electromagnetic waves whose intensity corresponds to their surface temperature, and as the temperature of the object increases, the radiant energy increases, and the radiant energy of short wavelengths increases relatively. -40 to 1, which is usually considered as a target for temperature measurement
, the wavelength of radiant energy at 600°C is approximately 2-1
This is 3 μf infrared radiation. Therefore, by measuring the amount of radiated infrared rays, it is possible to know the temperature of an object without contact.Using this principle, the infrared rays emitted from the object are detected, and this is converted into an electrical signal to display the temperature of the object. Thermotracers have been put into practical use that have built-in infrared radiation thermometers and imaging functions, including optical systems, to display the temperature distribution of each part of an object's surface as a thermal image on a screen.

Therefore, if you image an object using a thermotracer, you can obtain a thermal image that shows the temperature distribution at each part of the object's surface.
Even if this object is vibrated as it is, the thermal image will not change according to the vibration mode of the vibrating surface. However, if the surface of the object is made of damping material such as epoxy resin,
When a paste-like vibration damping material (DPO20 manufactured by NEC Environmental Engineering Co., Ltd.) containing a filler is added to this material and it is vibrated, the object receives a damping effect and the vibration energy is converted into thermal energy, causing the temperature of the object to rise. The six vibration energy that increases the vibration mode has a large antinode part and a small node part, so a temperature distribution occurs according to the vibration mode. Therefore, as shown in Fig. 1, when the surface of an object 2 that has been given damping properties by applying damping material 1 is imaged with a thermotracer 4 equipped with an infrared detector 3, it will accurately correspond to the vibration mode of the object. A thermal image having a temperature distribution is displayed on the screen 5. In the present invention, the vibration damping material 1 does not necessarily need to be formed on the surface on the side where the object 2 is imaged. Even when the damping material 1 is placed on the surface opposite to the imaging surface, if the vibration energy generated by the excitation is converted to heat and the temperature of the object rises due to the heat, which surface can be suppressed? The same thing happens when you shake it. Damping materials are not necessarily limited to being piled up. Painting, pasting.

A method such as integral molding may also be used. The higher the damping performance of the damping material, the higher the temperature rise of the object due to damping, and therefore the striped pattern of temperature distribution corresponding to the vibration mode appears more clearly. However, if the object to be measured itself is made of a material with high vibration damping properties, it is meaningless to add vibration damping properties to the object.

〔Example〕

Examples of the present invention are shown below.

In Figure 2, 300 x 32 mm x 5 iron plates 11
A damping material (DPO20 manufactured by NEC Environmental Engineering Co., Ltd.) 12 is evenly arranged on one side to a thickness of 5111 fI. Hereinafter, this laminated plate will be referred to as a sample plate. The center portion of this sample plate was horizontally attached to a vibrator 14 with screws 13. On the other hand, the sample plate was vibrated at the resonant frequency of its bending moment, a thermotracer (6T61 manufactured by NEC Sanei) 15 was installed directly above the sample plate, and the thermotracer 1
A thermal image of the sample plate obtained on the screen 16 of No. 5 was observed. Note that the room temperature was 24°C. In the thermotracer used in the example, the temperature of the subject is displayed by color change, and as the temperature rises, the temperature changes in the order of blue B - green G - yellow Y - red R. be done.

In the non-vibration state, the entire surface of the sample plate exhibited blue color B, which indicates the temperature range of 23.1 to 23.4°C, as shown in Figure 3(a), but at the resonant frequency of the primary bending mode of the sample plate. When the corresponding 223Hz was applied at 150 (G) for 10 minutes, the central area of the sample plate became 29~29cm as shown in Figure 3(b).
A red R indicates a temperature range of 31℃, a yellow Y indicates a temperature range of 25 to 27℃ on both sides, and a green G indicates a temperature range of 22 to 23℃ at both ends. The primary mode waveform of was clearly appeared by the color change.

Next, 1218Hz, which corresponds to the secondary bending mode of the sample plate.
was applied for 10 minutes at 150 (G), as shown in Figure 3 (C), a red color R appears in the medium heat area and the areas on both sides of it, yellow Y appears between each red area, and green color appears at both ends. G
It showed. That is, a typical vibration secondary mode waveform in which antinodes of a vibration waveform with large displacement appear at two locations was clearly displayed on the screen by changing the color.

[Comparative example]

A steel plate of the same size as that used in the example was attached as it was to the vibrator as in the example, and 201 Hz, which corresponds to the resonance frequency of the -order bending mode, was applied at 200 (G) for 20 minutes. As shown in Figure (d), the overall appearance was green G, and yellow Y only appeared irregularly in some areas, and no clear color change corresponding to the vibration mode was observed.

〔Effect of the invention〕

As described above, according to the present invention, the vibration mode of an object can be displayed by a clear color change, and therefore, a two-dimensional image of the vibration mode of the vibrating object can be visually visualized in real time and by remote sensing. can be directly observed through

Therefore, the method of the present invention can be applied not only to the fields of civil engineering and construction and IR machinery, but also to data on vibration modes of moving automobiles and ships, as well as vibrations of flying objects in the fields of space and aviation. mode data, as well as surfaces that are too small to mount an acceleration sensor (IC
This has the effect of making it possible to easily obtain and evaluate vibration mode data of (e.g.) vibration modes.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the principle of the method of the present invention, Figure 2 is a diagram showing the apparatus used in the example, and Figures 3 (a) to (d) are diagrams showing color changes in vibration modes in the example and comparative example. FIG. 1... Damping material, 2... Object. 3...Infrared detector, 4...Thermotracer 5...Screen. 4 Thermo-Traser - Patent Applicant Nippon Electric Environmental Engineering Co., Ltd. No. 1 Figure 15 Thermotraser / Figure 2 (α) (b) (C) Figure 3

Claims (1)

[Claims] (1) Vibrate at least a part of the object, including the structure or material whose vibration mode is to be measured, by imparting vibration damping properties, optically detect the infrared radiation energy emitted from the object, and measure the vibration mode. A method for measuring vibration modes characterized by displaying the distribution of temperature changes at various parts of a vibration surface as a thermal image as a result of damping vibrations on an object surface.