JP2500344B2 - Ultrasonic measurement method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic measuring method, and more particularly to an ultrasonic measuring method for nondestructively measuring the inside of an object having a rough surface.

[0002]

2. Description of the Related Art In ultrasonic flaw detection, which is a typical example of ultrasonic measurement, ultrasonic waves are reflected due to the existence of interfaces between dissimilar materials in an object and spaces due to cracks, and the intensity of the reflected wave and the transmitted wave. The state of the interface, the position of the crack, and the like are measured by measuring the time (path length) from the time of sending (or detecting the surface reflected wave) to the detection of the reflected wave. The ultrasonic waves used for this measurement are sent from the ultrasonic probe toward the subject. Therefore, FIG. 3 shows a schematic diagram for explaining a relational state between the ultrasonic probe and the subject in the conventional ultrasonic measurement. Here, 1 is a subject, 2 is an ultrasonic probe,
Reference numeral 7 is water, and 8 is (the image display of) the transmitted ultrasonic waves.

In the air, most of the ultrasonic waves are reflected at the interface between the ultrasonic probe and the air, and the energy of the ultrasonic waves incident on the subject 1 becomes very small. Water 7 is used as a medium for efficient transmission, and both the subject 1 and the ultrasonic probe 2 are submerged in water during ultrasonic measurement. In this state, the ultrasonic wave 8 (the wave image of which is indicated by a chain double-dashed line in the figure) transmitted from the focus type ultrasonic probe 2 is focused on the focal point and propagates through the water 7 so that the subject 1 To the surface 1a of the
It propagates through the inside and reaches the defect F in the subject 1.

The defect F is usually a void, and its acoustic impedance is significantly different from the original acoustic impedance of the subject 1. Therefore, the ultrasonic waves are reflected by the defect F,
The reflected wave is transmitted in the reverse order of the above-mentioned transmission path and reaches the ultrasonic probe. In this way, the measurement result of the echo reception signal of the ultrasonic waves reflected by the defect F in the subject 1 or the surface, the bottom surface, etc. is displayed as, for example, an A scope image, and the waveform is observed, The inside of the subject can be inspected and measured without destroying the subject.

[0005]

In such a conventional ultrasonic measuring method, ultrasonic waves are sent from the outside of the subject to the surface of the subject in order to measure the internal state of the subject by the ultrasonic waves. To be done. At this time, the surface of the subject, which is usually an individual, is not always flat, and in particular, in nondestructive inspection, the subject has a surface with its original surface roughness. Then, between the ultrasonic probe and the subject, water or the like, which is a liquid, exists so as to exclude air or the like.

Generally, since the acoustic impedance of a substance is unique to the substance, it is rare that the acoustic impedance of water or the like coincides with the acoustic impedance of the subject. Since the ultrasonic wave is a kind of wave, when it is transmitted to another medium having different acoustic impedance, the ultrasonic wave has a property that the traveling direction is refracted at an interface which is not orthogonal to the traveling direction. Furthermore, for the same reason, ultrasonic waves have the property that the limit of measurement resolution due to ultrasonic waves is limited by their wavelength. Specifically, the measurement result with higher accuracy can be obtained when the ultrasonic wave of the short wavelength is used than when the ultrasonic wave of the long wavelength is used.

From these facts, when the wavelength of the ultrasonic wave used for measurement is close to or less than the surface roughness of the object, the ultrasonic wave is dispersed on the surface and cannot proceed normally. The ultrasonic waves are dissipated (see the chain double-dashed line 8a in FIG. 3). Therefore, measurement becomes impossible. Therefore, in order to avoid such a situation, the surface roughness of 10 is practically used.
Ultrasounds with double or more wavelengths are used.

However, in the case where the surface roughness of the surface of the object is rough, using ultrasonic waves of a long wavelength corresponding to this surface roughness is inconvenient because the measurement resolution becomes poor. In particular, a defect whose size is close to or smaller than the surface roughness of the test object cannot be detected at all, which is a problem. An object of the present invention is to solve such a problem of the prior art, and to realize an ultrasonic measurement method capable of measuring the inside of a subject with high resolution without damaging the subject.

[0009]

In order to achieve this object, an ultrasonic measuring method according to the present invention uses an ultrasonic wave sent from the outside of a subject to the surface of the subject to determine the internal state of the subject. In the ultrasonic measurement method for measuring the object, the object is ultrasonically measured through a mixture attached to the surface of the object with a release agent or a release film interposed therebetween. This mounting is performed under the following conditions or treatments.

The release agent is thinly applied to the surface of the subject, or the release film is thin and applied to the surface of the subject. The mixture, first, with a mixing ratio at which the acoustic impedance after mixing is substantially equal to the acoustic impedance of the subject,
The first mixing material and the second mixing material are substantially uniformly mixed and made. The first mixed material has an acoustic impedance larger than the acoustic impedance of the subject. The second mixed material has an acoustic impedance smaller than the acoustic impedance of the subject. The mixed mixture is then pressure-bonded to the subject from the release agent or release film, and solidified,
The surface is a flat surface having a surface roughness smaller than that of the surface of the subject.

[0011]

In the ultrasonic measuring method of the present invention having such a structure, the mixture is attached to the surface of the object having a rough surface condition. This mixture is such that its acoustic impedance closely matches that of the subject. Ultrasonic waves are hardly reflected at such a continuous acoustic impedance, that is, at the surface of the subject with the mixture. Therefore, with respect to ultrasonic measurement, the existence of the original surface of the test object can be ignored, so it is possible to consider the test object with the mixture as one and test it as one test object. .

Further, the surface condition of the mixture applied to the object, that is, the surface condition of the object regarded as one is
It is flatter than the original surface of the subject. Ultrasonic waves do not dissipate on a flat mixture surface. Therefore, in measuring the subject with the mixture, it is possible to use ultrasonic waves having a shorter wavelength than before. Moreover, as described above, the limit of the resolution of ultrasonic measurement is determined by the wavelength of this ultrasonic wave. Therefore, the inside of the subject can be measured with high resolution by the ultrasonic waves of short wavelength without being affected by the roughness of the surface of the subject.

Further, a thin release agent or a thin release film exists between the mixture and the subject. Therefore, the mixture and the subject can be easily separated with a relatively small force without destroying both. Furthermore, after the separation, the surface of the sample is washed with a solvent for the mold releasing agent or the like, whereby the mold releasing agent or the like is easily removed without damaging the sample, and the surface of the sample is returned to its original state. Since the thickness of the release agent or the like is much thinner than the surface roughness in question, the release agent or the like does not affect the measurement. Therefore, the ultrasonic measurement method of the present invention can measure the inside of the subject with high resolution without damaging the subject.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a schematic diagram for explaining a relational state between an ultrasonic probe and a subject in the ultrasonic measurement method of the present invention. Here, 1 is a subject, 2 is an ultrasonic probe, 7 is water, 8 is a transmitted ultrasonic wave (image), 9 is a peeling agent, and 10 is a mixture. The ultrasonic probe 2 is shown as a focus type in this example. However, regarding the problems of ultrasonic wave scattering on the surface of the subject and the measurement resolution, the same applies to the non-focus type. is there.

The subject 1 is a heat-resistant tile used in, for example, a nuclear power generator or a space shuttle, and has a thermal spray coating for improving heat resistance. For this reason, the roughness of the surface thereof is about several tens of μm to several hundreds of μm. Of course, it is used in a harsh environment,
Precise inspection needs to be performed nondestructively. The release agent 9 may be used for a mold when molding a plastic product such as a bucket, for example, and it is easy to use a release agent that is placed in a spray can in a state in which a fluorine resin is dissolved in a solvent. . Since it is used for injection molding or the like, it has a certain degree of heat resistance (100 ° C. to 300 ° C.) and is not strongly adhered / bonded to plastic or the like. Then, the surface of the subject 1 is sprayed thinly and coated. Its thickness is usually several μm or less.

The mixture 10 is a mixture of tungsten powder and plastic powder. Here, tungsten has a relatively large acoustic impedance (10
Since it is 4 × 1000000 Kg / m ² s), it is suitable as a mixed material having an acoustic impedance larger than the acoustic impedance of the subject 1. On the other hand, plastic has a relatively low acoustic impedance (3 x 1000000 Kg / m ² s)
Therefore, it is suitable as a mixed material having an acoustic impedance smaller than the acoustic impedance of the subject 1. Other mixed materials may be used as long as the magnitude relationship of the acoustic impedance is satisfied. Also,
As for the method of producing powder, a method of spray-cooling molten metal and the like have been put into practical use, and powder of 1 μm or less is also common.

The mixing ratio of the tungsten and the plastic is determined so that the acoustic impedance after mixing matches that of the subject 1. Since the acoustic impedance of the mixture changes the value between that of tungsten and that of plastic depending on the mixing ratio, there always exists a suitable mixing ratio. The mixture 10 uniformly mixed at this mixing ratio is applied to the subject 1 coated with the release agent 9, and is pressed and heated by an iron-like object having a flat pressing surface. As a result, the heat-softening plastic is melted and the mixture 10 adheres to the subject 1. Then, when the plastic cools and solidifies, the mixture 1
0 and the test object 1 are a test object having a flat surface with the release agent 9 interposed therebetween as one body.

The plastic is not limited to powder and may be in a fluid state. Further, the material is not limited to the one that is heat-softening, and may be one that is thermosetting, one that hardens by volatilizing a solvent, or one that cures by aging by reacting two liquids. Further, the flattening of the surface of the mixture 10 can be performed by performing mechanical processing although the above-described molding method is simple. In this way, a surface roughness of about several μm or less than 1 μm can be easily obtained.

In this state, the ultrasonic waves 8 of short wavelength (for example, (20 μm)) transmitted from the focus type ultrasonic probe 2 (the wave image of which is indicated by a chain double-dashed line in the figure) are focused on the focus. Then, it travels through the water 7, reaches the surface of the mixture 10, and enters it. The surface roughness of this mixture 10 is several μ.
Since it is less than or equal to m, the ultrasonic wave 8 propagates in the mixture 10 with almost no disturbance. Further, when the surface of the subject 1 is reached, the thickness of the peeling agent there is 1 μm or less, and the acoustic impedance of the mixture 10 and the subject are the same. The ultrasonic waves are transmitted to the subject 1 without being disturbed. Then, it propagates through the subject 1 and reaches the defect F in the subject 1 (see the image of 8b).

The ultrasonic wave reflected by the defect F follows the transmission path in the reverse order to the ultrasonic wave and is transmitted to the ultrasonic probe to be measured as an echo reception signal. As described above, since the ultrasonic wave having a shorter wavelength than the conventional one can be used for the measurement, it is possible to measure the defect F having the same size as the surface roughness of the subject 1. Further, after the measurement, the separation agent 9 easily separates,
The release agent 9 may be removed from the subject 1 using a solvent or the like. Therefore, the subject 1 is not damaged.

FIG. 2 is a block diagram showing a schematic configuration of an example of an ultrasonic measuring device for measuring the inside of a subject by such an ultrasonic measuring method. Where 1 is the subject, F
Is its internal defect, 2 is the probe, 3 is the pulsar receiver,
Reference numeral 4 is a sampling circuit, 5 is a device control circuit, and 6 is a display unit. As described above, the probe 2 emits an ultrasonic transmission wave to the subject 1 and detects the reflected wave.
It is an ultrasonic transducer. The pulsar receiver unit 3 receives the pulsar activation signal a ″ and outputs an electric signal for operating the probe 2, and the pulsar receiver unit 3 receives a detection signal from the probe 2 and performs amplification and the like to receive an echo. And a receiver section for outputting as a signal e (RF signal or detected signal).

The sampling circuit 4 receives the sampling activation signal a, generates the pulser activation a ", and
The sampling of the echo reception signal e is started, and a predetermined amount of sampling data is stored in the memory. Device control circuit 5
Is responsible for overall control of the device such as generation of the sampling activation signal a. Further, the MPU control signal b and the MPU address signal c are sent to the sampling circuit 4 and the memory is supplied via the sampling circuit 4. The sampling data stored in is read as an MPU data signal, and processing for display such as range selection and enlargement is performed,
It is displayed on the display unit 6.

With such an ultrasonic measuring device, an echo reception signal in which an ultrasonic wave having a shorter wavelength than before is reflected by the defect F or the like in the subject 1 is measured. Then, the measurement result is displayed on the display unit 6 as, for example, an A scope image or the like, and by observing the waveform, the inside of the subject can be inspected and measured with high resolution without destroying the subject. . Although the release agent 9 of this embodiment is described as being in the form of a liquid or a fluid, if it is in the form of a thin and soft film, it may be used instead of the liquid or fluid. Is possible.

[0024]

As can be understood from the above description, in the ultrasonic measuring method of the present invention, a thin mixture of a mold release agent and a flat mixture is attached to the surface of an object having a rough surface condition. To be Moreover, the acoustic impedance of this mixture substantially matches that of the subject. Due to the matching of the acoustic impedances, the presence of the original surface of the subject can be ignored for ultrasonic measurement, and the flat surface state of the mixture attached to the subject prevents ultrasonic waves from being dissipated by conventional methods. It becomes possible to use ultrasonic waves having a shorter wavelength. Therefore, the inside of the subject can be measured with high resolution by the ultrasonic waves of short wavelength without being affected by the roughness of the surface of the subject.

Further, the presence of the release agent or the release film makes it possible to easily separate the mixture and the test substance without damaging either of them. Therefore, the inside of the subject can be measured with high resolution without damaging the subject. In particular, even when the surface roughness of the object is rough, it is possible to detect even defects having a size close to or less than the surface roughness of the object.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an embodiment of an ultrasonic measuring method having a configuration of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of an ultrasonic measurement device used for carrying out an ultrasonic measurement method.

FIG. 3 is an explanatory diagram of a conventional ultrasonic measurement method.

[Explanation of symbols]

 1 Test Subject 2 Probe 3 Pulser Receiver 4 Sampling Circuit 5 Device Control Circuit 6 Display 7 Water 8 Ultrasonic Wave (Image Display) 9 Stripping Agent 10 Mixture

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Nishimori Inventor Hiroyuki Nishimori 650 Kuchidatecho, Tsuchiura City, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant (72) Inventor Kazuo Fujishima 650 Jinmachicho, Tsuchiura City, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura Factory (56) Reference JP-A-1-142456 (JP, A) JP-A-3-163355 (JP, A) Actual development Sho 59-158055 (JP, U)

Claims (1)

(57) [Claims] 1. An ultrasonic measuring method for measuring an internal state of the subject by means of ultrasonic waves sent from the outside of the subject to the surface of the subject, wherein the value of the ultrasonic impedance is larger than the acoustic impedance of the subject. The first mixing material having an acoustic impedance and the second mixing material having an acoustic impedance smaller than the acoustic impedance of the subject are almost uniformly mixed, and the acoustic impedance after mixing is the same as that of the subject. Of the subject, which is made to have an acoustic impedance, and which is applied to the surface of the subject with a release agent thinly applied to the surface of the subject or a thin release film that has been applied on the surface of the subject. An ultrasonic measurement method comprising ultrasonically measuring the subject through a mixture having a flat surface having a surface roughness smaller than the surface roughness of the surface.