JPH0361833A - Measuring method for vibration mode - Google Patents

Abstract

PURPOSE:To make it possible to measure a two-dimensional vibration mode which is generated on a vibrating surface visually by imparting thermal insulation to a body, vibrating the body, optically detecting infrared radiation energy which is emitted from the body, and displaying the result as a thermal display. CONSTITUTION:Thermal insulation is imparted to a body 2 by depositing a thermal insulating material 1. The image of the surface of the body 2 is sensed by use of a thermo-tracer 4 containing an infrared-ray detector 3. Then the thermal image having temperature distribution exactly corresponding to the vibration mode of the body 2 is displayed on a screen 5 of the tracer. The vibration mode of the body 2 can be displayed by the definite change in colors in this measuring method. The two-dimensional image of the vibrating body 2 in the vibration mode can be directly observed visually by remote sensing in real time.

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]

It is extremely important to know how the vibration mode of a structure or material behaves when it is vibrated in the design of machines and artifacts.

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, subjects the data to Fourier transform, and analyzes the vibration mode of the vibrating 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 and requires a large amount of numerical calculations, and it cannot be compared with the actual vibration modes that occur in the target structure. often 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 thermal insulation added to it, and The system optically detects the emitted infrared radiation energy and displays the distribution of temperature changes on the vibrating surface as heat is generated in each part of the object's surface as a thermal image, corresponding to the vibration mode.

[Principle/effect]

If the vibrations that occur in a sample when it is vibrated are converted into heat, the magnitude of the vibrations can be measured as the amount of thermal change. The object is
It emits electromagnetic waves with a strength corresponding to its surface temperature.
As the temperature of an object increases, the radiant energy increases and the radiant energy of short wavelengths increases relatively0
-40 to 1, which is usually considered as the target of temperature measurement.
The wavelength of radiant energy at 600℃ is approximately 2-13μ
m infrared rays. 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. When shaken, the vibrational energy applied to an object is converted into thermal energy, increasing the object's temperature. Since the vibration energy is large at the antinode of the vibration mode and small at the nodes, a temperature distribution occurs according to the vibration mode. Therefore, as shown in FIG. 1, when the surface of an object 2, which has been given thermal insulation properties by applying a thermal insulation material 1, is imaged by a thermotracer 4 with a built-in infrared detector 3, the vibration mode of the object 2 can be accurately detected. A thermal image having a corresponding temperature distribution is displayed on the screen 5. In the present invention, the thermal insulating material 1 does not necessarily need to be formed on the side on which the object 2 is imaged, but may be formed on the surface opposite to the imaging surface. Even when heat insulating material 1 is piled up, if the vibration energy generated by excitation is converted into heat and the temperature of the object rises due to that heat, the same effect will occur no matter which side is insulated. . Thermal insulating material is not necessarily applied by piling it up; it can also be applied by painting, pasting, integral molding, etc. The lower the thermal conductivity of the thermal insulating material, the lower the mobility of heat, so it can be applied depending on the heat generation temperature of the object. A rapid temperature gradient occurs in each part, and the thermotracer clearly shows a color pattern of temperature distribution that corresponds to the vibration mode. However, if the object to be measured itself is made of a material with high thermal conductivity, it is meaningless to add thermal insulation to the object.

〔Example〕

Examples of the present invention are shown below.

In FIG. 2, a heat insulating material 12 was uniformly arranged to a thickness of 3rn on one side of an iron plate 11 forming a substantially equilateral triangle with a negative side of 300 cm.

Hereinafter, this laminated plate will be referred to as the sample plate, and the thermal insulation material 1
2 is a sample plate ■ using a thermoplastic material (A-57) (damping c/cc 3-4% thermal conductivity 0.4 w/m-k) manufactured by Nippon Electric Environmental Engineering ■ and a thermal insulation material 12. The company's thermosetting material (DP-020) (damping c/cc 3-4% thermal conductivity 14 w/shin/k)
) and two types of sample plates (■) were prepared, and the central part of each of the sample plates (■ and ■) was connected to the vibration exciter 1 using the screw 13.
4 was installed horizontally. On the other hand, the sample plate was vibrated at the resonance frequency of its bending moment, and a thermotracer (6T61 manufactured by NEC Sanei ■) 15 was installed directly above the sample plate.
The thermal image of the sample plate obtained on the screen 16 of the thermotracer 15! IIA. Note that the room temperature was 24°C. In the thermotracer used in the example, the temperature of the subject is displayed as a color change, and as the temperature rises, the temperature changes in the order of blue B - green G - yellow Y - red R. Ru.

In the non-vibration state, both sample plates (■) and (2) exhibited a green color G indicating the room temperature range, but at approximately 30 (G) around 250H2, which corresponds to the resonance frequency of the sample plate's primary bending mode, 0.
When the voltage was applied for 5 minutes, as shown in Figure 3(a), sample plate ■ had a temperature of +1.0 to +1.5°C above room temperature in the center area of sample plate ■ and in a wide range from the center area to the center of each side.
A red color R indicating a high temperature range was displayed in a thick band shape, and a certain area around the periphery showed a yellow color Y which was 0.5° C. higher than room temperature. On the other hand, in sample ■, as shown in FIG. 3(b), only a small area in the center of the sample plate ■ exhibited red R, and yellow Y appeared in a thick band shape from the periphery of red R to the center of each side.

This color pattern represents the shape of the primary mode specific to the shape of the sample plate. As can be seen by comparing FIGS. 3(a) and 3(b), the shape of the vibration mode can be more clearly expressed by using a thermal insulating material with a lower thermal conductivity. The reason why the thermal conductivity is low is that the heat generated in the vibrating part of the sample plate is retained at the generated part and not dispersed, resulting in a clear temperature difference between the vibrating part and the non-vibrating part.

〔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 by effectively utilizing the properties of the thermal insulation material, and therefore, the vibration mode of the object being excited can be detected in real time and remotely. This allows the two-dimensional image of the vibration mode to be directly observed visually.

Therefore, the method of the present invention can be used not only in the fields of civil engineering and construction, but also in the field of aerospace machinery, as it is non-contact, vibration mode data on moving automobiles and ships, as well as vibration mode data on flying objects in the fields of space and aviation. The present invention has the effect that it is possible to obtain and easily evaluate vibration mode data of a surface (such as an IC) that is so small that it is impossible to attach an acceleration sensor.

[Brief explanation of drawings]

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 actual example, and Figures 3 (a) and (b) are diagrams showing color changes of vibration modes in the example. be. 1... Heat insulation material, 2... Object. 3...Infrared detector, 4...Thermotracer 5...Screen.

Claims (1)

[Claims] (1) Vibrate at least a part of the object, including the structure or material to be measured, with thermal insulation, and optically detect the infrared radiation energy emitted from the object. A vibration mode measurement method characterized by displaying the distribution of temperature changes on a vibration surface as a thermal image due to heat generation in various parts of an object surface.