JP2003307510A - Object inspection method and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an object inspection device for detecting even an invisible very small defect, easy in handling, and inexpensive compared to an X-ray flaw detector. <P>SOLUTION: This device is composed of an exciting means for exciting an inspection object by transmitting vibration changing in a frequency stepwise, a vibration detecting means for detecting the vibration of the inspection object at exciting time, a natural frequency extracting means for determining a natural frequency of the inspection object from this detected vibration, and a determining means for determining the existence of the defect of the inspection object by comparing the extracted natural frequency of this inspection object with an already known normal natural frequency. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object inspection method and an apparatus therefor, and more particularly, to an object inspection method and an apparatus therefor, the quality of which depends on the presence or absence of scratches such as cracks on the object. It is about.

[0002]

2. Description of the Related Art Non-destructive inspection, which inspects the quality of an object without destroying the object, is capable of 100% inspection. Therefore, the need for non-destructive inspection is increasing. An X-ray flaw detector is typical of this nondestructive inspection. This X-ray flaw detector detects when a molded object made of metal, ceramic, plastic, etc. has a defect such as a crack such as a crack, even if the defect is very small and invisible. Can have excellent performance.

[0003]

However, since the X-ray flaw detector uses radiation called X-rays,
When using the device, it is necessary to consider safety, it is difficult to handle, and the cost is high.
Therefore, there is a demand for an object inspection method and an apparatus thereof that can detect even a very small invisible defect, are easy to handle, and have a lower cost than an X-ray flaw detector. The present invention has been made to address such a demand.

[0004]

The present invention utilizes the fact that when an object has scratches such as scratches and cracks, the resonance frequency of this object is different from the resonance frequency when there are no such scratches. Yes, a vibration whose frequency fluctuates in a stepwise manner is applied to the object to determine its natural frequency, which is its resonance frequency, and this is compared with the normal natural frequency of a known good product to determine the quality of the object. To do.

That is, the object inspection method of the present invention excites an object to be inspected by transmitting a vibration whose frequency fluctuates in stages, and at the same time detects the vibration of the object to be inspected and inspects the detected vibration from the detected vibration. It is characterized by determining the natural frequency of the object and comparing the obtained natural frequency of the inspected object with a known normal natural frequency in advance to determine the quality of the inspected object. .

The object inspecting apparatus of the present invention comprises an exciting means for exciting vibration of an object to be inspected by transmitting a vibration whose frequency fluctuates stepwise, and a vibration detecting means for detecting vibration of the object to be inspected at the time of excitation. From the detected vibration, the natural frequency extraction means for obtaining the natural frequency of the object to be inspected, and the natural frequency of the extracted object to be inspected, by comparing with a known normal natural frequency, It is characterized by having a determining means for determining whether or not there is a defect in the inspected object.

In the above-mentioned object inspection apparatus, by using not only the basic natural frequency but also a high-order natural frequency as the natural frequency and the normal natural frequency, it is possible to improve the accuracy of the presence / absence of a defect. .

An acoustic emission sensor (AE) is used as a vibration detecting means used in the above object inspection apparatus.
Sensor) is recommended.

When inspecting a plate-shaped object to be inspected,
The above-mentioned object inspection apparatus is configured by a ring-shaped magnet whose axial direction is vertical, an excitation unit including an excitation coil arranged coaxially with the magnet, and two magnetic bodies which vertically sandwich the base end of the inspection object. And an upper core whose lower surface provided on the upper surface side of the object to be inspected is horizontal, and an upper core provided on the lower surface side of the object to be inspected is horizontal and which is placed horizontally on the excitation unit. The object-to-be-inspected object holding section and the excitation means are configured, and the other end of the object-to-be-inspected is placed on the upper surface of the vibration isolation table whose upper surface is a horizontal surface having the same height as the upper surface of the lower core. At the same time, it is desirable that the vibration detecting end of the vibration detecting means is pressed against the upper surface of the other end of the inspected object.

Further, in the case of inspecting an object to be inspected having a general shape, the above-mentioned object inspecting apparatus is provided with an exciting section including a ring-shaped magnet whose axial direction is vertical and an exciting coil arranged coaxially with the magnet. The top surface of the object to be inspected is composed of a horizontal upper surface placed on the same horizontal surface and a metallic object-to-be-inspected plate on which the object to be inspected is placed and the excitation means. In addition, it is desirable that the vibration detecting end of the vibration detecting means is in pressure contact.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. The present invention, as described above, when the object has scratches such as scratches and cracks,
By utilizing the fact that the resonance frequency of this object is different from the resonance frequency when there are no such scratches, the object is given a vibration whose frequency fluctuates in stages, and the natural frequency that is the resonance frequency is calculated. The quality of the object is judged by comparing this with the normal natural frequency of a known good product. Therefore, prior to the implementation of the present invention, a non-defective model and a defective defective model were set for the object to be inspected, and simulation was performed by calculation based on the inspection principle of the present invention. Next, the results of this simulation will be explained, and then examples of the present invention will be explained.

FIG. 10A shows a model of the object to be inspected used in the simulation.
(B) is the sectional view. In FIGS. 10A and 10B, the model of the object to be inspected has a width of 150 mm and a length of 15 mm.
It is a silicon plate 41 having a thickness of 0 mm and a thickness of 0.3 mm. The silicon plate 41 is horizontally arranged, and the base end of the silicon plate 41 is vertically contacted with the vibrating wall surface 43, and the vibrating wall surface 43 is vibrated in the vertical direction, so that the silicon plate 41 is a model of the object to be inspected. The plate 41 is excited to obtain the resonance frequency of the silicon plate 41. The other end of the silicon plate 41 is a free vibration end.

A non-defective model is a silicon plate 41 having no scratches anywhere. The silicon plate 41 having a linear crack parallel to the vibrating wall surface 43 is a defective model of the silicon plate 41. 10A and 10B show an example of this defective product model. In the simulation, the normal natural frequency, which is the resonance frequency of the non-defective product, and cracks in different states
This is done by calculating the natural frequency, which is the resonance frequency of a plurality of defective products provided in 1. As the state of cracks, three types of forms were used. As described above, these crack forms are linear cracks parallel to the vibrating wall surface 43 provided at the center of the silicon plate. In the first crack form, the crack position is the center of the silicon plate 41, the crack length is 150 mm, the crack width is 0.01 mm, and the crack depth is changed. The second crack morphology has a crack length of 150 mm, a crack width of 0.01 mm and a crack depth of 0.15 mm.
Then, the crack position is located at the center of the silicon plate 41 and at a position close to the vibrating wall surface 43 from this center (from the center to the vibrating wall surface 4
3 is represented by a minus), and a position away from the center in the opposite direction to the vibrating wall surface 43 (a distance from the center is represented by a plus). The third crack morphology is
The crack position is the center of the silicon plate 41, and the crack length is 15
The crack width is 0 mm and the crack depth is 0.15 mm.

FIG. 11 is a graph showing the result of simulation in the first crack morphology, where (a) is the first resonance frequency which is the lowest resonance frequency, and (b) is the first natural frequency.
The second natural frequency which is the next highest resonance frequency of the next natural frequency, and (c) is a graph relating to the third natural frequency which is the second highest resonance frequency of the second natural frequency. In the figure,
A crack depth of 0 mm indicates a good product. In the case of this first crack mode, the natural frequency of the defective product is the natural frequency of the non-defective product, that is, both the primary natural frequency and the secondary natural frequency,
It is well below the normal natural frequency. Also, the third natural frequency does not exist in non-defective products, but exists in defective products. In any case, it is understood that the quality of the inspected object can be determined by obtaining the natural frequency of the inspected object and comparing it with the normal natural frequency.

FIG. 12 is a graph showing the result of the simulation in the second crack mode. Like FIG. 11, (a) is the primary natural frequency, (b) is the secondary natural frequency, and FIG. (C) is a graph regarding the third natural frequency. In the figure, no crack indicates a good product. In the case of this second crack form, the natural frequency of the defective product is much lower than the normal natural frequency of the good product in the primary natural frequency. However, the second natural frequency may be larger or smaller than the normal natural frequency, or may be very close to the normal natural frequency, such as at the plus 50 mm position. The third natural frequency is much higher than the normal natural frequency. From the result of the second crack morphology, it can be seen that in some cases, the natural frequency of the defective product and the normal natural frequency may be very close to each other. Therefore, in the measurement of the natural frequency of the object to be inspected, the first natural frequency which is the lowest resonance frequency, that is, not only the basic natural frequency but also the higher natural frequency is measured, By using these results in combination, it is possible to make a highly accurate pass / fail determination of the object to be inspected.

FIG. 13 is a graph showing the result of the simulation in the third crack mode. As in FIG. 11, (a) is the first natural frequency, (b) is the second natural frequency, and FIG. (C) is a graph regarding the third natural frequency. In the figure, a crack width of 0 mm indicates a non-defective product. In this case, the natural frequency of the defective product is much lower than the normal natural frequency in both the primary natural frequency and the secondary natural frequency. Also, the third natural frequency does not exist in non-defective products, but exists in defective products. In any case, it is understood that the quality of the inspected object can be determined by obtaining the natural frequency of the inspected object and comparing it with the normal natural frequency.

Next, an object inspection apparatus according to the first embodiment of the present invention will be described. FIG. 1 shows the configuration of the object inspection apparatus according to the first embodiment of the present invention. The object inspection apparatus of the first embodiment is an apparatus for inspecting a plate-shaped object to be inspected. In FIG. 1, this apparatus is composed of an excitation unit 1, an inspected object holding unit 2, a vibration isolation table 4, an AE sensor 5, an AE sensor holding mechanism 6, and a control unit 7.

The excitation unit 1 is composed of a ring-shaped magnet 1a whose axial direction is vertical and an excitation coil 1b arranged coaxially with the ring-shaped magnet 1a. The ring-shaped magnet 1a has an N pole on the inside and an S pole on the outside.
It is composed of a station, and an exciting coil 1b is arranged inside the station. The excitation unit 1 transmits the vibration generated by the electromagnetic force of the excitation coil 1b to the inspection target object 3 via the inspection target object holding unit 2 described below, and thus the inspection target object 3
It has a function to excite. The inspected object holding unit 2 is made of ferrite and is composed of an upper core 2a and a lower core 2b which are arranged vertically, and the lower surface of the upper core 2a and the upper surface of the lower core 2b have a horizontal shape. The base end of the plate-shaped object 3 to be inspected is sandwiched between the lower surface of the upper core 2a and the upper surface of the lower core 2b. Since the inspected object holding portion 2 is made of ferrite and is a magnetic body and is placed on the upper surface of the excitation portion 1, it is attracted to the ring-shaped magnet 1a of the excitation portion 1 and firmly attached to the excitation portion 1. Is fixed. Therefore, the inspection object 3 held by the inspection object holding portion 2
Can be firmly fixed to the excitation unit 1. The anti-vibration table 4 supports the other end of the object 3 to be inspected so that the object 3 to be inspected is horizontal, and the upper surface thereof is a horizontal plane having the same height as the upper surface of the lower core.

An AE sensor 5 is arranged above the other end of the object 3 to be inspected. The AE sensor 5 is composed of a vibration transmission rod 5a and a vibration detector 5b, and has a function of measuring a natural frequency which is a resonance frequency of the inspected object 3. The vibration transmitting rod 5a is preferably a non-magnetic and electrically insulating inorganic solid so that an eddy current is generated inside and does not vibrate by acting with an external magnetic field. Among the inorganic solids, both insulating and hard to electromagnetic fields are hard. In terms of having both, non-magnetic and electrically insulating ceramics are preferable,
Fine ceramics using high-purity alumina are particularly preferable. Further, the diameter of the vibration transmission rod 5a is about 3 in order to prevent generation of noise caused by the lateral vibration of the vibration transmission rod 5a.
It is preferable that the length is set to mm or more, and it is preferable that the tip end portion of the vibration transmission rod 5a is formed in a round shape. The vibration detector 5b has a vibration sensor inside, and the vibration sensor is elastically urged downward using a spring so that the vibration sensor and the vibration transmission rod 5a integrally press the upper surface of the inspected object 3. is doing. The AE sensor holding mechanism 6 has a function of holding the AE sensor 5 at a fixed position, and the position of the AE sensor 5 can be adjusted up and down according to the thickness of the inspected object 3. The control unit 7 includes the excitation coil 1 of the excitation unit 1.
It has a function of determining the quality of the inspected object 3 by supplying a current to b to excite the excitation coil 1b and receiving an output signal of the AE sensor 5 for processing.

Next, referring to FIG. 2, the excitation coil 1b
The control unit 7 which determines the quality of the inspected object 3 by supplying a pulse current to the inspected object and obtaining the natural frequency which is the resonance frequency of the inspected object 3 will be described in detail. FIG. 2 shows the control unit 7.
3 is a block diagram showing a schematic configuration of FIG. In FIG. 2, reference numeral 1 is an excitation part, 1a is a ring magnet, 1b is an excitation coil, 5 is an AE sensor, 5a is a vibration transmission rod, and 5b.
Indicates a vibration detector.

The control unit 7 has an exciting circuit 11 for supplying a pulse current to the exciting coil 1b, an amplifier circuit 12 for amplifying the output signal of the vibration detector 5b, and an A- for converting the output signal of the vibration detector 5b into a digital signal. A D converter 13, a CPU 14 for controlling these, a RAM 16, a ROM 15 in which a program for executing various processes according to a predetermined procedure is stored, and data such as a known normal natural frequency of a non-defective item of an object to be inspected are stored. It has a rewritable EEPROM 21, a display means 17 for displaying inspection results and the like, an input means 18 for inputting condition settings and the like, and an interface circuit 20 through connection with an external device 19 such as a computer.

In the excitation circuit 11, a sharp rising or falling pulse voltage as shown in FIG. 3 is applied to the excitation coil 1b under the control of the CPU 14, whereby a pulse current is supplied to the excitation coil 1b. In this embodiment, a rectangular wave is suitable as the pulse voltage, but the present invention is not limited to this, and another pulse wave may be used. The excitation frequency of such pulse current is controlled by the CPU 14 as follows.
It can be changed stepwise in units within the range of 1 Hz to 20 Hz. For example, when the frequency starts from the maximum value of 50 kHz, the frequency is gradually reduced in units of 10 Hz to the desired minimum value. In this way, one cycle time for changing the excitation frequency stepwise from the maximum value to the minimum value is 1
Call it a cycle. When such a pulse current is supplied to the excitation coil 1b, the vibration detector 5b detects the longitudinal vibration of the inspected object 3 and outputs an oscillation signal having a waveform as shown in FIG.

Further, exemplifying in the time chart of FIG. 5, in the nth or (n + 1) th measurement cycle, the CP
U14 controls the timing of the excitation signal output from the excitation circuit by the signal output time τ according to the waveform of FIG. 5 (a), and the signal input timing of capturing the output signal of the vibration detector is shown in FIG. 5 (b). Signal output time τ according to the waveform
It is controlled by the terminal time t1 in.

In each measurement cycle, a pulse signal having a constant frequency as shown in FIG. 3 is supplied to the exciting coil 1b during the signal output time τ according to the waveform of FIG. During that period, a pulse signal having a constant frequency that is 10 Hz less than the previous frequency is supplied to the excitation coil 1b, and the like is repeatedly executed, and the excitation frequency is gradually reduced. In this way, the excitation frequency is stepwise reduced from the maximum value to the minimum value, as shown in FIG. The vibration detector 5b detects the object 3 to be inspected according to each excitation frequency.
The oscillation signal is detected and the oscillation signal is output.
During the termination time t1 shown in FIG. 5 (b), the AD converter 13
After being converted into a digital signal by the CPU, it is taken into the CPU 14. Such an oscillating signal has a waveform as shown in FIG. 6A and forms a peak when the excitation frequency matches the resonance frequency. Thus, the signal output time τ
Is set and a pulse current is supplied to the excitation coil 1b at an excitation frequency that changes stepwise, so that the oscillation signal corresponding to the excitation frequency can be detected and identified extremely accurately during the signal output time τ. It is possible.

At the end of each measurement cycle, CP
U14 processes the digitally converted oscillation signal (digital input signal) during the signal processing time t2 according to the control signal of FIG. 5C to obtain the resonance frequency. Specifically, the value of the digital input signal is processed by the CPU 14 and temporarily stored in the storage table together with the corresponding excitation frequency and cycle. Next, the resonance frequency calculation means is called from the program stored in the ROM 15, the storage table is referred to, and the waveform data shown in the envelope waveform 22 of the waveform of FIG. 6A is shown as shown in FIG. 6B. Then, the peak value is found, and the oscillation frequency corresponding to this peak value is set as the resonance frequency, that is, the natural frequency. Such processing is performed every measurement cycle. The number of measurement cycles may be once or plural times. The average value of the resonance frequencies may be calculated from a plurality of measurement cycles.

Next, the inspected object quality evaluation means is called from the program stored in the ROM 15, and the normal natural frequency of a known good object of the inspected object stored in the EEPROM 21 is called by this means. The quality of the inspected object 3 is determined by comparing it with the natural frequency obtained above. That is, if the normal natural frequency and the natural frequency determined above match, it is determined to be good, and if they do not match, it is determined to be defective. After the quality determination is completed, the quality of the inspected object 3 may be displayed on the display unit 17, or may be displayed on a display lamp (not shown) according to the quality, or from a speaker (not shown). A tone sound may be output. Also,
By connecting to an external device 19 such as a computer via the interface circuit 20 shown in FIG. 4, it is possible to combine the device with a higher-level system such as a production management system.

The vibration detector 5b does not always output a waveform having a clear peak as shown in FIG. 6A, but outputs a waveform having a plurality of peaks as shown in FIG. 6C. , It may be difficult to identify the peak value corresponding to the resonance frequency. In such a case, a group of peak waveforms having a peak (waveform group) is selected, and a waveform synthesizing process is executed in each waveform group as shown in FIG.
It is preferable to generate 3a and 23b, find the maximum value from the peak values of the combined waveforms 23a and 23b, and set the corresponding oscillation frequency as the resonance frequency. The combined waveform of FIG. 6D is displayed in a slightly reduced size as compared with the waveform of FIG. 6C.

Table 1 shows a sample of the plate-like object 3 to be inspected, which is a non-defective good product (No. 1) and a defective product having scratches such as scratches (No. 2 to No. 6). The object inspection apparatus shows the result of measuring the fundamental natural frequency, which is the lowest resonance frequency, that is, the first natural frequency five times. Further, FIG. 7 is a graph of the average values in Table 1. In this sample, in the case of non-defective product, its resonance frequency is between 83.038kHz and 83.294kHz, which is the normal natural frequency. In the case of a defective product, as can be seen from FIG. 7, its fundamental natural frequency is lower than this normal natural frequency. Therefore, by comparing the basic natural frequency and the normal natural frequency obtained by measurement,
The quality of the object to be inspected can be determined.

[0029]

[Table 1]

Table 2 shows non-defective products (No. 3) and defective products (No. 1, No. 2, No. 4, No. 5) for other plate-shaped samples.
It is the result of measurement similar to the above, and FIG. 8 is a graph of the average value of Table 2. In this sample, in the case of non-defective product, its resonance frequency is between 35.406kHz and 35.434kHz, which is the normal natural frequency. Also in this sample, in the case of a defective product, as can be seen from FIG. 7, the fundamental natural frequency is lower than the normal natural frequency. Therefore, similarly to the above, the quality of the inspected object can be determined by comparing the fundamental natural frequency obtained by the measurement with the normal natural frequency.

[0031]

[Table 2]

According to the above-mentioned object inspection apparatus, vibrations of which the frequency fluctuates step by step are applied to the object to be inspected, and the natural frequency which is the resonance frequency thereof is obtained. Since the quality of the object to be inspected is determined by comparing with the frequency, it is possible to detect a very small defect that cannot be seen. Further, since dangerous radiation such as X-rays is not used, it is possible to provide an object inspection device that is easy to handle and has a lower cost than an X-ray flaw detector. In addition, a ring-shaped magnet is used for the excitation part that excites the object to be inspected, and an upper core and a lower core made of ferrite, which are magnetic materials, are used for the object to be inspected holding part that holds the object to be inspected. Since the upper core and the lower core are attracted to the ring-shaped magnet, the object to be inspected is firmly fixed to the excitation unit, and the vibration generated by the excitation unit can be accurately transmitted to the object to be inspected. Therefore, an accurate measurement can be realized. Further, using an upper core and a lower core for vertically sandwiching the base end portion of the plate-shaped object to be inspected, and a vibration isolation table supporting the other end of the object to be inspected,
The plate-shaped object to be inspected can be easily and accurately inspected.

In the first embodiment described above, the acoustic emission sensor (AE sensor) is used as the means for detecting the vibration of the object to be inspected, but the invention is not limited to this and other sensors may be used. Further, although the exciting coil is arranged inside the ring-shaped magnet, it may be arranged outside. Further, in the above-described first embodiment, only the fundamental natural frequency that is the lowest resonance frequency, that is, only the first-order natural frequency is measured, but as described above, not only this fundamental natural frequency, By measuring the high-order natural frequency,
By using these results in combination, it is possible to make a highly accurate pass / fail determination of the object to be inspected.

Next, the object inspection apparatus of the second embodiment for inspecting a general inspected object which is not a plate will be described. FIG. 9 is an explanatory diagram showing the configuration of the object inspection device of the second embodiment. As shown in FIG.
1, a metal plate 32, an AE sensor 34, an AE sensor holding mechanism 35, and a control unit 36. The object inspection apparatus according to the second embodiment removes the object-to-be-inspected holding unit and the vibration isolation table from the object inspection apparatus according to the first embodiment, and the excitation unit 3
The object to be inspected 33 is placed on the upper surface of the metal plate 32 placed on the upper surface of the device 1, the AE sensor 34 is disposed above the object 33, and the AE sensor 34 is held by the AE sensor holding mechanism 35. , Excitation unit 31, AE sensor 34, AE
The sensor holding mechanism 35 and the control unit 36 are configured similarly to the first embodiment. That is, the excitation unit 31 is composed of the ring-shaped magnet 31a and the excitation coil 31b, the AE sensor 34 is composed of the vibration transmission rod 34a and the vibration detector 34b, and the lower end of the vibration transmission rod 34a is the object 33 to be inspected. A point on the top surface of is pressed. Further, the configuration of the control unit 36 is exactly the same as that of the first embodiment.

The object inspection apparatus according to the second embodiment described above performs a measurement on a general object to be inspected, which is not in the form of a plate, by the same method as that of the object inspection apparatus according to the first embodiment.
The quality of the inspected object 33 is determined by the same principle as that of the embodiment.

[0036]

According to the invention of claim 1 or 2,
The vibration of which the frequency fluctuates in a stepwise manner is applied to the inspected object to obtain the natural frequency, which is its resonance frequency, and this is compared with the normal natural frequency of a known good product to determine whether the inspected object is good or bad. Therefore, it is possible to detect a very small defect that cannot be seen. Further, since dangerous radiation such as X-rays is not used, it is possible to provide an object inspection device that is easy to handle and has a lower cost than an X-ray flaw detector.

According to the third aspect of the present invention, not only the fundamental natural frequency but also the high-order natural frequency are measured as the natural frequency and the normal natural frequency. Therefore, these measurement results are used together. By making the above determination, it is possible to make a highly accurate pass / fail determination of the inspection object.

According to the fifth aspect of the present invention, a ring-shaped magnet is used for the exciting portion for exciting the inspected object, and the ferrite, which is a magnetic material, is used for the inspected object holding section for holding the inspected object. The upper and lower cores made of steel are used, and the upper and lower cores are attracted to the ring-shaped magnet, so that the object to be inspected is firmly fixed to the excitation part and the vibration generated by the excitation part is suppressed. The object to be inspected can be accurately transmitted. Therefore, an accurate measurement can be realized. In addition, an upper core and a lower core that sandwich the base end portion of the plate-shaped object to be inspected vertically and a vibration isolation table that supports the other end of the object to be inspected are used to inspect the plate-shaped object to be inspected. Can be performed easily and accurately.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an object inspection device according to a first embodiment.

FIG. 2 is a block diagram of a control unit of the object inspection apparatus of the first embodiment.

FIG. 3 is a diagram showing an example of a pulse voltage output from an excitation circuit of the object inspection device of the first embodiment.

FIG. 4 is a diagram showing a vibration waveform output by a vibration detector of the object inspection device of the first embodiment.

FIG. 5 is a time chart showing various signals of the object inspection device of the first embodiment.

FIG. 6 is a schematic diagram showing an oscillation signal and its processed signal of the object inspection device of the first embodiment.

FIG. 7 is a graph of measurement results of a sample of a plate-shaped inspected object.

FIG. 8 is a graph of measurement results of another sample of the plate-shaped inspected object.

FIG. 9 is a diagram showing a configuration of an object inspection device according to a second embodiment.

FIG. 10A is a diagram showing a model of an object to be inspected used for simulation, and FIG. 10B is a sectional view thereof.

FIG. 11 is a graph showing the result of simulation in the first crack morphology, where (a) is the first natural frequency, (b) is the second natural frequency, and (c) is the third natural frequency. It is a graph regarding a frequency.

FIG. 12 is a graph showing a result of simulation in a second crack form, where (a) is the first natural frequency, (b) is the second natural frequency, and (c) is the third natural frequency. It is a graph regarding a frequency.

FIG. 13 is a graph showing a result of simulation in a third crack form, where (a) is the first natural frequency, (b) is the second natural frequency, and (c) is the third natural frequency. It is a graph regarding a frequency.

[Explanation of symbols]

1 Excitation section 1a Ring magnet 1b Excitation coil 2 Inspected object holder 2a Upper core 2b Lower core 3 Inspected object 4 Vibration isolation table 5 AE sensor 5a Vibration transmission rod 5b Vibration detector 6 AE sensor holding mechanism 7 control unit 11 Excitation circuit 12 amplifier circuit 13 A-D converter 14 CPU 15 ROM 16 RAM 17 Display means 18 Input means 19 External equipment 20 Interface circuit 21 EEPROM 22 Envelope waveform 23a composite waveform 23b Synthetic waveform 31 Excitation section 31a ring-shaped magnet 31b Excitation coil 32 metal plate 33 Inspected object 34 AE sensor 34a Vibration transmission rod 34b Vibration detector 35 AE sensor holding mechanism 36 Control unit 41 Silicon plate that is the model of the object to be inspected 42 crack 43 Vibration wall

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Keisuke Yoshimura             2-502 Minami-ochiai, Suma-ku, Kobe-shi, Hyogo             −803 (72) Inventor Yu Sakai             1-403 Nakaochiai, Suma-ku, Kobe City, Hyogo Prefecture             −505 F-term (reference) 2G047 AB04 BA04 BA05 BC04 BC07                       CA02 EA10 GC01 GF11 GG33                       GG37

Claims (6)

[Claims] 1. A vibration of a stepped frequency is transmitted to excite an object to be inspected, and at the same time, a vibration of the object to be inspected is detected, and a natural frequency of the object to be inspected is detected from the detected vibration. An object characterized in that the quality of the inspected object is determined by comparing the obtained natural frequency of the inspected object with a known normal natural frequency. Inspection method. 2. Exciting means for exciting vibration of an object to be inspected by transmitting vibration whose frequency fluctuates stepwise, vibration detecting means for detecting vibration of the object to be inspected during the excitation, and the detected vibration. By comparing the natural frequency of the extracted object with the natural frequency extracting means for obtaining the natural frequency of the object to be inspected from the vibration, a normal frequency known in advance is used to An object inspection apparatus, comprising: a determination unit that determines whether or not there is a defect in an object to be inspected. 3. The object inspection apparatus according to claim 2, wherein not only the fundamental natural frequency but also a high-order natural frequency is used as the natural frequency and the normal natural frequency. 4. The object inspection apparatus according to claim 2, wherein an acoustic emission sensor is used as the vibration detecting means. 5. The object to be inspected is plate-shaped, a ring-shaped magnet whose axial direction is vertical, and an excitation unit including an excitation coil arranged coaxially with the magnet, and a base end portion of the object to be inspected vertically. An upper core, which is made up of two magnetic materials sandwiched between the two, and has a horizontal lower surface provided on the upper surface side of the inspected object, and an upper surface provided on the lower surface side of the inspected object is horizontal; Of the object to be inspected consisting of a lower core horizontally placed on the upper part and the excitation means, and the upper surface of the vibration isolation table having a horizontal surface at the same height as the upper surface of the lower core. The object according to claim 4, wherein the other end of the object to be inspected is placed on the upper surface, and the vibration detecting end of the vibration detecting means is pressed against the upper surface of the other end of the object to be inspected. Inspection device. 6. An exciting part including a ring-shaped magnet whose axial direction is vertical and an exciting coil arranged coaxially with the magnet, an upper surface placed on the same horizontal surface is a horizontal surface, and the upper surface is covered with the object to be covered. The excitation means is composed of a metallic inspection object mounting plate on which an inspection object is mounted, and the vibration detecting end of the vibration detecting means is pressed against the top surface of the inspection object. Item 4. The object inspection device according to item 4.