JP2012013522A - Method and apparatus for low frequency vibration excitation using ultrasonic wave - Google Patents

Abstract

A vibration method using an ultrasonic sensor capable of oscillating a low frequency by using a plurality of high frequency ultrasonic sensors and a structure thereof are provided.
According to the low frequency vibration excitation method using ultrasonic waves of the present invention, a plurality of ultrasonic oscillators are attached to a target structure to generate ultrasonic waves and cause a beating phenomenon. A low frequency is extracted and a physical property value of the target structure is measured. As a result, it is possible to oscillate a low frequency using a plurality of high frequency ultrasonic sensors. By using a relatively small high frequency ultrasonic sensor, not only flat plates and pipes, but also any shape can be freely used. Can be applied to. Further, since the vibration can be applied to a specific frequency in the acceleration region, the present invention can be applied to a region where the signal-to-noise ratio is not good.
[Selection] Figure 2

Description

  The present invention relates to a low-frequency vibration excitation method and apparatus using ultrasonic waves, and more specifically, since a low frequency can be oscillated by using a plurality of high-frequency ultrasonic sensors, By using a sonic sensor, it can be freely applied regardless of the shape of a flat plate or piping. In addition, the present invention relates to a low-frequency vibration excitation method and apparatus using ultrasonic waves that can be applied even in a region where the signal-to-noise ratio is not good because vibration can be performed at a specific frequency in the acceleration region.

  FIG. 1 is a graph showing a dispersion curve in a flat plate. As shown in the figure, the higher the frequency, the more complicated the mode is. However, since there is only an asymmetric a0 wave in the low frequency region, using this region makes it possible to obtain a great variety of information such as pipe thickness prediction, defect detection, and physical property value prediction.

As an example, according to Korean Registered Publication No. 10-817617, filed and registered by the present applicant, “Structure Thickness and Physical Property Inspection Device, Inspection Method and Thickness Reduction Monitoring Method”, the target structure is low. A group velocity based on the delay time is calculated by a pair of vibration wave measurement units that are excited at a certain frequency along the direction of travel on the surface of the structure, and the object between the measurement units The thickness of the structure can be predicted.
In addition, the thickness or physical property value of the target structure can be applied to a flat plate, piping, or other structures of various shapes in this way, especially for piping used in the turbine generator system of a nuclear power plant. It is also possible to predict the degree of wall thickness reduction by applying pipe thickness information.

  However, an ultrasonic sensor is generally used for exciting a vibration wave, but generally, a low-frequency ultrasonic sensor has a disadvantage in that it is large in size due to structural characteristics. Therefore, there is a problem that it is difficult to apply to small structures such as flat plates and pipes. Therefore, research on a method of exciting a low frequency using a relatively small size high frequency ultrasonic sensor is required.

Republic of Korea Registered Publication No. 10-817617

  Accordingly, an object of the present invention to solve the above-mentioned problems is to provide an excitation method using an ultrasonic sensor capable of oscillating a low frequency using a plurality of high frequency ultrasonic sensors and a structure thereof. .

  Another object of the present invention is to apply a vibration method using an ultrasonic sensor that can be freely applied regardless of the shape, including bent pipes such as flat plates and pipes, by using a relatively small size high-frequency ultrasonic sensor. And providing its structure.

  Another object of the present invention is to provide an excitation method using an ultrasonic sensor and a structure thereof that can be applied even in a region where the signal-to-noise ratio is not good because the vibration can be applied to a specific frequency in the acceleration region. It is to provide.

  In order to achieve the object of the present invention as described above, the low frequency vibration excitation method using ultrasonic waves according to the present invention includes a plurality of ultrasonic oscillators attached to a target structure to generate ultrasonic waves and the beating phenomenon. And a physical property value of the target structure is measured by extracting a frequency lower than the frequency of the ultrasonic oscillator.

  The low frequency vibration excitation method using ultrasonic waves according to the present invention induces a beating phenomenon using two ultrasonic oscillators, and extracts only the frequency difference of the ultrasonic oscillators in the acceleration region to obtain the target structure. It is characterized by measuring the physical property value.

  The low-frequency vibration excitation method using ultrasonic waves according to the present invention includes a target structure, a first ultrasonic oscillator that applies ultrasonic waves of a first frequency to the target structure, and the target structure. A second ultrasonic oscillator that vibrates ultrasonic waves of a second frequency similar to the first ultrasonic wave, and extracts the difference between the first frequency and the second frequency by a beating phenomenon, and the target structure It is characterized by measuring physical property values of physical properties.

  Such a target structure can be a flat plate, a pipe, or various types of structures, and the measured physical property values may vary in thickness.

  As a result, a plurality of high frequency ultrasonic sensors can be used to oscillate a low frequency, so a relatively small high frequency ultrasonic sensor can be used to shape bent pipes such as flat plates and pipes. Nevertheless, not only can it be applied freely, but it can also be applied to a region where the signal-to-noise ratio is not good because vibration can be applied to a specific frequency in the acceleration region.

  According to the present invention, it is possible to oscillate a low frequency using a plurality of high frequency ultrasonic sensors.

  Further, by using a relatively small size ultrasonic sensor for high frequency, it can be freely applied regardless of its shape, including bent pipes such as flat plates and pipes.

  Further, since vibration can be applied to a specific frequency in the acceleration region, there is an effect that can be applied even in a region where the signal-to-noise ratio is not good.

It is a graph which shows the dispersion | distribution curve in a flat plate. It is the schematic of the experimental apparatus which applied the low frequency vibration excitation method using the ultrasonic wave which concerns on this invention to the flat plate. It is a graph which shows the acceleration signal and ultrasonic signal in a measurement point with a flat plate. It is a graph which shows the spectrum of an ultrasonic signal. It is a graph which shows the spectrum of an acceleration signal. It is the schematic of the experimental apparatus which applied the low frequency vibration excitation method using the ultrasonic wave which concerns on this invention to piping. It is a graph which shows the acceleration signal and ultrasonic signal in a measurement point with piping. It is a graph which shows the spectrum of an ultrasonic signal and an acceleration signal.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited or limited by the embodiments.

  It is a known fact that a beating phenomenon appears when two sine waves having adjacent frequencies are generated simultaneously. This is a kind of interference phenomenon caused by two waves, and the wave generated by beating proceeds at a frequency having an intermediate value between the two wave frequencies before, and the amplitude changes to a relatively slow new period.

  This will be described in more detail as follows. Two sine waves are defined as Equation 1 and Equation 2.

  If two sine waves are generated and summed at the same time, the following equation 3 is derived.

  Here, k is a wave number, w is a frequency, and t is time.

  As shown in Equation 3, if two sine waves are combined, the center frequency is the average of the two frequencies, but the overall wave shape vibrates with a period that is half the difference between the two frequencies. I understand. That is, it can be seen that if the frequencies of the two sine waves are appropriately adjusted, vibration can be made to a lower frequency.

  From the above description, the ultrasonic sensor generates a high frequency of several hundred KHz, but if the frequency is appropriately adjusted using two ultrasonic sensors, a sine wave of several KHz that is an acceleration field region may be generated. It implies something.

  In order to verify such a method, the following experiment was conducted. FIG. 2 is a schematic view of an experimental apparatus in which a low-frequency vibration excitation method using ultrasonic waves according to the present invention is applied to a flat plate.

  In order to confirm that a low frequency is vibrated using the beating phenomenon of an ultrasonic oscillator that vibrates two high frequencies, in this experiment, two high frequency ultrasonic oscillators 110 and 120 are mounted on a flat plate 10 and each is mounted. 400 kHz and 430 kHz sine waves were vibrated. The ultrasonic oscillators 110 and 120 are connected to each oscillation device 130. At the measurement point, the ultrasonic sensor 150 and the acceleration field 140 were provided at the same position to acquire a signal. Data acquisition modules 160 and 170 for acquiring each signal are connected to the ultrasonic sensor 150 and the acceleration field 140. The experiment was conducted with the distance (L) between the ultrasonic oscillators 110 and 120, the ultrasonic sensor 150, and the acceleration field 140 being 0.1 m in this experiment.

  Such results are shown in FIGS. 3 is a graph showing the acceleration signal and the ultrasonic signal at the measurement point on a flat plate, FIG. 4 is a graph showing the spectrum of the ultrasonic signal, and FIG. 5 is a graph showing the spectrum of the acceleration signal.

  As shown in FIG. 3, it can be confirmed that a beating phenomenon occurs in a high-frequency signal having a similar frequency of 400 kHz and 430 kHz, and referring to Equation 3, the center frequency is 415 kHz, and the magnitude of two frequencies. It can be confirmed that it vibrates with a period that is half the difference.

  As shown in FIG. 4, the ultrasonic waves generate high frequencies of 400 kHz and 430 kHz, but as shown in FIG. 5, only 30 kHz corresponding to the difference between the two frequencies is detected in the acceleration field signal. I understand. That is, it can be seen from such experiments that a beating phenomenon can be generated using an ultrasonic sensor that vibrates two high frequencies on a flat plate, and a low frequency signal can be generated in the acceleration region.

  Next, the following experiment was conducted regarding whether or not the vibration method according to the present invention was applied to piping. FIG. 6 is a schematic diagram of an experimental apparatus in which a low-frequency vibration excitation method using ultrasonic waves according to the present invention is applied to piping.

  The same experiment as the flat plate experiment is performed, and the same apparatus as in FIG. 2 is given the same reference numeral in FIG. 6 and is omitted for the sake of simplicity. However, in the experiment applied to the pipe 20, the excitation frequency of each ultrasonic sensor was set to 300 kHz and 308 kHz.

  The experimental results applied to the piping are shown in FIGS. FIG. 7 is a graph showing the acceleration signal and the ultrasonic signal at the measurement point in the pipe, and FIG. 8 is a graph showing the spectrum of the ultrasonic signal and the acceleration signal.

  As shown in FIG. 7, it can be confirmed that a beating phenomenon occurs in high-frequency signals having similar frequencies as 300 kHz and 308 kHz. In FIG. 8, portions indicated as 300 kHz and 308 kHz indicate ultrasonic signals as 8 kHz. The part represents the acceleration signal. That is, it can be confirmed that only 8 kHz of the difference between the two high frequencies can be detected in the acceleration region. In conclusion, as in the flat plate experiment, it can be seen that if a high frequency having a similar frequency is vibrated, a low frequency signal can be generated in the acceleration region by the beating phenomenon. Furthermore, if the vibration method according to the present invention is used, vibration can be applied to a specific frequency in the acceleration region, so that it can be applied even in regions where the signal-to-noise ratio is not good.

  That is, a low frequency can be oscillated using a small high frequency sensor without using a relatively large ultrasonic sensor for low frequency oscillation. Can be used by applying to things. As described above, it can be used for measuring physical properties such as the thickness of the target structure and structural characteristics using such a vibration method.

  As described above, the preferred embodiments of the present invention have been described with reference to the preferred embodiments of the present invention. However, those skilled in the relevant art will not depart from the spirit and scope of the present invention described in the claims. Thus, it will be understood that the present invention can be variously modified and changed. In other words, the technical scope of the present invention is defined based on the claims, and is not limited by the best mode for carrying out the invention.

10: Flat plate 20: Piping 110, 120: Ultrasonic oscillator 130: Oscillator 140: Acceleration field 150: Ultrasonic sensor 160, 170: Data acquisition module

Claims (9)

  A plurality of ultrasonic oscillators are attached to a target structure to generate a beating phenomenon by oscillating ultrasonic waves, and a physical property value of the target structure is measured by extracting a frequency lower than the frequency of the ultrasonic oscillator. A low-frequency vibration excitation method using ultrasonic waves.   The low-frequency vibration excitation method using ultrasonic waves according to claim 1, wherein the target structure is one of a flat plate and a pipe.   The low-frequency vibration excitation method using ultrasonic waves according to claim 1, wherein the physical property value is a thickness of the target structure. The target structure,
A first ultrasonic oscillator that vibrates ultrasonic waves of a first frequency to the target structure;
A second ultrasonic oscillator that vibrates ultrasonic waves of a second frequency similar to the first ultrasonic waves to the target structure,
A low-frequency vibration excitation apparatus using ultrasonic waves, wherein a physical property value of the target structure is measured by extracting a difference between the first frequency and the second frequency by a beating phenomenon.   The low-frequency vibration excitation apparatus using ultrasonic waves according to claim 4, wherein the target structure is one of a flat plate and a pipe.   The low-frequency vibration excitation apparatus using ultrasonic waves according to claim 4, wherein the physical property value is a thickness of the target structure.   A low frequency using ultrasonic waves characterized in that a beating phenomenon is induced using two ultrasonic oscillators, and only a difference in frequency of the ultrasonic oscillators is extracted in an acceleration region to measure a physical property value of a target structure. Vibration excitation method.   The low-frequency vibration excitation method using ultrasonic waves according to claim 7, wherein the target structure is one of a flat plate and a pipe.   The low-frequency vibration excitation method using ultrasonic waves according to claim 7, wherein the physical property value is a thickness of the target structure.

Images