JPS623901B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an ultrasonic transducer used for the purpose of detecting ultrasonic waves emitted due to deformation or destruction of solid materials and converting them into electrical signals. This paper relates to a longitudinal wave sensitivity calibration method.

[Conventional technology]

It is known that when solid materials deform or break, weak ultrasonic waves are emitted as a form of energy release.

This phenomenon is called acoustic emission (abbreviated simply as AE) or stress wave emission, and is considered to be applied to materials research and as a means of ensuring the safety of various structures. It is being

In the ultrasonic flaw detection method, which has traditionally been known as a non-destructive testing method, the overall longitudinal wave sensitivity of the equipment used for ultrasonic flaw detection is calibrated using a standard test piece containing a reference flaw. By doing so, it is possible to achieve that purpose.

On the other hand, in the case of AE measurement, the ultrasonic transducer for detection is used exclusively for the purpose of receiving waves, so in order to quantitatively evaluate AE, the ultrasonic transducer is used for detection. It becomes necessary to quantitatively understand the sensitivity of longitudinal waves.

Conventionally, to calibrate the longitudinal wave sensitivity of an ultrasonic transducer used for AE detection, a method has been used to measure the response when the ultrasonic transducer is excited by a pseudo AE source generated by electric sparks, sandblasting, etc. has been used a lot.

However, since the absolute value of the ultrasound level and the frequency spectrum of these pseudo sound sources are not necessarily clear, they are used as the primary standard for the sensitivity calibration of the longitudinal waves of ultrasound, or are used for quantitative longitudinal wave sensitivity calibration. It has the disadvantage that it cannot be used directly for this purpose.

In order to perform quantitative longitudinal wave sensitivity calibration of an ultrasonic transducer, a diffuse sound field in a metal block or a surface wave sound field in a metal plate is used as a sound field for longitudinal wave sensitivity calibration. To this end, a method of longitudinal wave sensitivity calibration has been proposed that applies the principle of the mutual calibration method used in the fields of underwater acoustics and aerial acoustics.

However, conventional means using these methods require huge metal blocks, metal plates, and even two There was a practical difficulty in that it required the use of a large aquarium measuring 3 meters square.

[Problems with conventional technology]

In this way, with conventional means, the metal blocks, metal plates, and even water tanks that provide the sound field become huge.As mentioned above, in addition to reducing the influence of reflected ultrasonic waves, This is because not only longitudinal ultrasonic waves but also transverse waves are generated in the sound field, and these longitudinal waves and transverse waves are received by the ultrasonic transducer and output without being distinguished.

The present invention was devised to solve the drawbacks and problems of the conventional examples described above, and it eliminates the generation of transverse waves, forms a sound field that can excite longitudinal waves, and uses this sound field. Therefore, the technical objective is to provide a method for calibrating the longitudinal wave sensitivity of an ultrasonic transducer that can be widely used in practice.

[Means and actions for solving problems]

Hereinafter, the method of the present invention will be explained with reference to drawings showing embodiments of the method of the present invention.

In the sensitivity calibration method of an ultrasonic transducer according to the present invention, an ultrasonic transducer 3 for longitudinal wave sensitivity calibration is attached to one end of a rod-shaped solid body 1 having a length and a diameter equal to or less than one wavelength of ultrasonic waves. , an ultrasonic transducer 2 as a reference is attached to the other end, and this rod-shaped solid 1 is used as an ultrasonic propagation medium, and the ultrasonic level or applied voltage E1 of the ultrasonic transducer 2 as a reference is calibrated, and the sensitivity of longitudinal waves is calibrated. This is achieved by calculating the output voltage E0 of the ultrasonic transducer 3 which performs the following.

That is, when the reference ultrasonic transducer 2 is operated as an ultrasonic transmitter by applying an applied voltage E1, the ultrasonic transducer 3 that operates as a receiver calibrates the sensitivity of longitudinal waves. When the output voltage E0 is output from , the longitudinal wave sensitivity M of the ultrasonic transducer 3 operated as a receiver is quantitatively given by the following equation.

M=E0/E1·1/S (1) where S is the quantitative longitudinal wave sensitivity of the ultrasonic transducer 2 operated as a transmitter. Also, E
0 and E1 are output voltages and applied voltages, but these are not limited to voltages, and may be other electrical signal levels such as output currents, applied currents, output power, or applied power.

In the above equation (1), if the longitudinal wave sensitivity S of the ultrasonic transducer 2 is not quantitatively determined in advance, the principle of the mutual calibration method that is practically used underwater where only longitudinal waves propagate is used. By applying the longitudinal wave sensitivity calibration method according to the invention, this transmitting sensitivity S is determined quantitatively.

That is, three ultrasonic transducers whose transmitting and receiving sensitivities for longitudinal waves are unknown are combined in order and the transmitting and receiving sensitivities of each ultrasonic transducer in the three combinations are calculated. By finding the relational expressions and combining these relational expressions, it is possible to determine the desired transmitting sensitivity S of the ultrasonic transducer 2.

On the other hand, if the receiving sensitivity M when operating as a receiver is determined quantitatively, it can be obtained from equation (1), S=E0/E1・1/M......from (2) , the transmission sensitivity S can be determined quantitatively.

Furthermore, if there is an ultrasonic generator 12 that is a suitable ultrasonic generator and the sound pressure V1 of the ultrasonic waves excited by this ultrasonic generator is known, the longitudinal wave transmission sensitivity S Regardless of the applied voltage E2, the longitudinal wave reception sensitivity M of the ultrasonic transducer 3 can be determined by M=E0/V1 (3).

In addition, in equation (3), V1 is the ultrasonic generator 1
The sound pressure was set to 2, but this V1 is the ultrasonic generator 1
The output value is not limited to the sound pressure of 2, but may be a known output value of another ultrasound generator 12, such as displacement, displacement speed, or even acceleration of the output ultrasound.

As described above, the method of the present invention transmits ultrasonic waves from the ultrasonic transducer 3 or the ultrasonic generator 12 through the rod-shaped solid 1 having a length and a diameter equal to or less than one wavelength of the excited ultrasonic waves. The wave is transmitted to the ultrasound transducer 3 and the longitudinal wave receiving sensitivity M of the ultrasound transducer 3 is measured. When the thickness and diameter of the rod-shaped solid 1 that propagates sound waves becomes larger than the length corresponding to one wavelength of the propagated ultrasound, the proportion of the radial component of the ultrasonic vibrations propagated through the rod-shaped solid 1 increases. becomes large, making it difficult to perform highly accurate longitudinal wave sensitivity calibration.

In other words, when the diameter of the rod-shaped solid 1 becomes larger than the length of one wavelength of the ultrasonic wave being propagated, not only longitudinal waves but also transverse waves are generated in the ultrasonic wave propagated through the rod-shaped solid 1. At the same time, the radial component in the longitudinal wave increases, which becomes a standing wave and interferes with the proper longitudinal wave component, resulting in the ultrasonic transducer 3
This makes the reception sensitivity M of the longitudinal waves measured in 1.

On the other hand, if the thickness and diameter of the rod-shaped solid 1 is set to a value smaller than the length of one wavelength of the ultrasonic wave being propagated, the ultrasonic wave propagating through the rod-shaped solid 1 becomes almost linear, and the transverse wave component is Naturally, the radial component of the longitudinal wave will disappear, so
This allows the ultrasonic transducer 3 to receive longitudinal waves without interference from standing waves.

Therefore, by the method of the present invention, the longitudinal wave receiving sensitivity M
When calibrating, even if a conventional cross-calibration method is used or an ultrasound generator 12 with a known sound pressure V1 is used, the diameter of transverse waves and longitudinal waves in the propagated ultrasound waves must be calibrated. Ultrasonic transducer 3 from only its output voltage E0 without considering the directional component at all.
This means that the reception sensitivity M of longitudinal waves can be accurately and easily calibrated.

〔Example〕

The embodiment shown in FIG. 1 uses three ultrasonic transducers whose longitudinal wave reception sensitivity M and longitudinal wave transmission sensitivity S are unknown, and one of the three ultrasonic transducers is used. This shows the case where the reception sensitivity M of longitudinal waves of a certain ultrasonic transducer 3 is determined using the mutual calibration method. Three sets are made, and by using these combinations, the longitudinal wave reception sensitivity M of the target ultrasonic transducer 3 is measured according to the principle of the above-mentioned mutual calibration method.

Note that when using the mutual calibration method shown in Figure 1, there is no need to assume a longitudinal wave sensitivity component in the longitudinal wave reception sensitivity M of each ultrasonic transducer that performs wave reception operation; Since all of the detected received wave values can be used as the received wave sensitivity M, calculation thereof is extremely simple, and there is no need to assume uncertain values, so high accuracy can be obtained.

Further, the illustrated embodiment in FIG. 2 shows an embodiment of the method of the present invention using an appropriate ultrasonic generator 12 whose sound pressure V1 is known, and in this case, the above-mentioned formula (3) Accordingly, the longitudinal wave reception sensitivity M of the ultrasonic transducer 3 can be directly measured and calibrated.

In the illustrated embodiment, a straight rod-like body with a uniform diameter is used as the rod-like solid 1.
The structure is not limited to the above structure, and as long as the thickness and diameter of each part is smaller than the length of one wavelength of the propagated ultrasound, the thickness and diameter of each part do not need to be uniform, and the thickness and diameter of each part do not need to be uniform. It does not have to be a hollow tube, and it may be partially or entirely hollow.

Furthermore, it goes without saying that the use of the ultrasonic transducer, which is the object of the longitudinal wave sensitivity calibration method according to the present invention, is not limited to the detection of AE.

Furthermore, the material of the rod-shaped solid 1 is not limited, and ceramic can be used in addition to metal materials such as aluminum and iron. By molding this rod-shaped solid body 1 using a material that can be used as a material, the reception sensitivity of longitudinal waves can be set with high precision. However, the material of this rod-shaped solid 1 is not limited, but it goes without saying that it must be made of a uniform material throughout.

〔Effect of the invention〕

As is clear from the above description, the present invention allows the longitudinal wave sensitivity of an ultrasonic transducer to be calibrated using a small and lightweight rod-shaped solid. This can be easily performed on the user side, and as a result, the reliability of measurement can be greatly improved. Since longitudinal wave reception is achieved without standing wave interference due to directional components, longitudinal wave reception sensitivity can be easily calculated without the need for troublesome correction of measured values, and accuracy can be improved. Since the material of the rod-shaped solid material is not limited, the ultrasonic transducer to which the longitudinal wave reception sensitivity is measured can be actually attached to the rod-shaped solid material. By molding the transducer with the same material used to mold other objects, it has many excellent effects, such as being able to more accurately calibrate the practical longitudinal wave sensitivity of this ultrasonic transducer.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention,
This figure shows a case where longitudinal wave sensitivity calibration of a target ultrasonic transducer is performed using a mutual calibration method.
FIG. 2 shows another embodiment of the present invention,
This is a case where the longitudinal wave reception sensitivity of the target ultrasonic transducer is calibrated using a suitable ultrasonic generator whose ultrasonic sound pressure, displacement, displacement velocity, acceleration, etc. are known. be. Explanation of symbols: 1; Rod-shaped solid; 2; Ultrasonic transducer; 3; Ultrasonic transducer; 12; Ultrasonic generator;
E1: applied voltage, E0: output voltage, M: longitudinal wave reception sensitivity, S: longitudinal wave transmission sensitivity, V1: sound pressure.

Claims (1)

[Claims] 1 Attach an ultrasonic transducer for longitudinal wave sensitivity calibration to one end of a rod-shaped solid having a thickness and diameter less than or equal to one wavelength of ultrasonic waves, and attach an ultrasonic transducer for reference to the other end. Using the rod-shaped solid as an ultrasound propagation medium, calculation is made from the ultrasound level or applied electrical signal level of the ultrasound transducer used as the reference and the output electrical signal level of the ultrasound transducer that performs sensitivity calibration of the longitudinal waves. Sensitivity calibration method for ultrasonic transducers.