JPH0549935B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method and apparatus for evaluating the location of defects such as cracks, cavities, and dents occurring in an object to be measured.

[Conventional technology]

For example, if cylinder parts or piston parts used in the piston mechanism of an automobile engine have defects such as cracks, cavities, or dents, the piston mechanism will fail. Therefore, it is preferable that parts having defects such as cracks, cavities, dents, etc. can be detected on the parts manufacturing line before assembly of the engine. Then, if you can evaluate the location of the defect,
It also helps in investigating the cause of defects. By the way, conventional methods for detecting and locating defects of this type include methods using ultrasonic reflection;
Known methods include acoustic detection (AE) (acoustic emission), an observation method using a CCD camera, an X-ray photography method, and a color check method.

[Problem to be solved by the invention]

However, each of the above conventional methods has the following handling problems. In other words, for example, ultrasonic flaw detection is a method of detecting defects by bringing them into contact with the object to be measured and evaluating their positions.Due to the straightness of ultrasonic waves, only the area where the sensor is applied can be measured, and there may be misalignment on the sensor connection surface. The waveforms that appear differ due to reflections and slight angle differences,
It is not easy to distinguish. Furthermore, in the case of the AE method, it is a contact method like the ultrasonic flaw detection method, and it cannot be measured unless the crack is progressive. On the other hand, if the crack is progressive, the crack will be measured as it expands. In addition, the observation method using a CCD camera has the drawback that even if there are stains or patterns other than defects such as cracks or dents, the judgment will be disturbed, and it is not possible to detect or evaluate the position of cavities called "su" in castings etc. . In addition, X-ray photography is effective because it allows direct visual observation, but it is difficult to adjust the X-ray dose, making it impossible to observe, and it is not suitable for 100% inspection of objects to be measured, and is not suitable for inspection on a manufacturing line. In view of the above points, it is an object of the present invention to provide a defect position evaluation method and apparatus that are capable of detecting and positioning defects on a workpiece in a non-contact manner and are easy to handle.

[Means to solve the problem]

This invention applies vibration to the object to be measured at multiple locations along the circumference of the object to be measured, and calculates the peak value of the fundamental natural vibration spectrum of the natural vibration of the object to be measured at each vibration position, and This is a defect position evaluation method in which the position where the difference from the peak value of the spectrum of vibration due to a defect in the object is the maximum is evaluated as the position where the defect exists in the object to be measured. The present invention also provides: a vibrating means for sequentially vibrating a plurality of locations along the circumference of a measured object; a pickup means for picking up the vibration of the measured object and converting it into an electrical signal; receives an electric signal from
The natural vibration of the object to be measured is analyzed spectrally, and the difference between the peak value of the basic natural vibration spectrum of the object to be measured and the peak value of the spectrum of vibration due to defects in the object to be measured is calculated for each of the plurality of excitations. A defect position evaluation device comprising a means for determining the position, and a means for detecting an excitation position where the difference between the peak values at each of the plurality of excitation positions is maximum, and determining the vicinity of this excitation position as a defect position. be. Further, the present invention provides a method for measuring an object having a circular or elliptical cross section at a position along the cross section,
Angular spacing smaller than 90°/3 and 90°
n (n=0, 1, 2, 3) or 60°×m (m=1,
2, 3, 4, and 5), and pick up the vibrations of the object to be measured at each of the excitation positions, and from the picked up vibrations, calculate the vibration of the object at each of the excitation positions. The peak value of the spectrum of the fundamental natural vibration of the object to be measured or the peak value of the spectrum of vibration due to a defect in the object to be measured is detected, and from the locus drawn by the peak values at the plurality of excitation positions, the peak value of the spectrum of the fundamental natural vibration of the object to be measured is detected. This is a defect position evaluation method that evaluates possible positions of defects. Further, the present invention provides a method for measuring an object having a circular or elliptical cross section at a position along the cross section,
Then, the vibration is applied at a position shifted from the center of gravity, and the natural vibration of the object to be measured is analyzed spectrally at this vibration position. depending on whether it is paired with the fundamental eigenspectrum of , or with the fundamental eigenspectrum of a lower frequency position.
This defect position evaluation method is characterized by evaluating whether the position of the defect is above or below the center of gravity.

[Effect]

The vibrations of the excited object to be measured can be picked up without contact. As a result of research by the inventor of this invention, when the picked-up vibrations were analyzed in spectrum, it was observed that if the object to be measured has a defect, the spectrum of the natural vibration of the object to be measured splits into two. It turns out it can be done. Furthermore, although the sum of the energy of the basic natural vibration and the energy of the vibration of the defective part is constant regardless of the excitation position, the magnitude of both vibrations differs depending on the excitation position relative to the defect position. The ratio of the energy (peak value) of both vibration spectra differs depending on the excitation position. At the defect position, the difference between the peak value of the basic natural vibration spectrum and the peak value of the vibration spectrum due to the defect in the object to be measured is the largest, so this position is considered as the location where the defect in the object to be measured exists. can be evaluated. In addition, when the cross-sectional shape of the object to be measured is a circle or an ellipse, the peak value of the basic natural vibration spectrum and the peak value of the spectrum of vibration due to defects in the object to be measured are 90° for the first-order vibration. Every,
It repeats in a substantially sinusoidal manner, and the peak value of the fundamental natural vibration spectrum and the peak value of the spectrum of the vibration due to the defect in the object to be measured are out of phase by 45° from each other. In addition, the secondary vibration repeats almost sinusoidally every 60 degrees, and the peak value of the basic natural vibration spectrum and the peak value of the vibration spectrum due to the defect in the object to be measured are out of phase with each other. is shifted by 30°. Note that the second-order vibration can also be considered to be repeated every 120 degrees. By the way, in order to reproduce the change in the peak value of the spectrum, it is possible to detect the peak value of the spectrum at three or more different excitation positions for one period of change, so it is possible to reproduce the change in the peak value of the spectrum within a 90° angle range. , excite at three points,
The peak values of the spectrum at all positions along the cross-sectional circumference can be predicted from the peak value of the spectrum at the excitation position. Moreover, when the cross section is circular or elliptical, as mentioned above, the peak value of the fundamental natural vibration spectrum and the peak value of the vibration spectrum due to the defect may be out of phase by a certain angle. Since it is known, the difference between the peak values of the fundamental natural vibration spectrum or the peak value of the vibration spectrum due to defects will be large from the locus of change along the circumferential direction of the measured object. Any one of a plurality of positions (4 points for a penetrating defect, 6 points for a non-penetrating defect) can be evaluated as a position where a defect occurs. Note that the three or more vibration positions mentioned above exclude positions that are an integral multiple of 90° or an integral multiple of 60° where the same result can be obtained. Furthermore, if the object to be measured has a circular or elliptical cross section, such as a cylindrical object, if vibration is applied at a position shifted from the center of gravity in the central axis direction, the upper and lower halves of the object will be separated. When the weights are different, two basic natural vibration spectra appear, one with a higher frequency and the other with a lower frequency, depending on the weight of the upper and lower halves. Then, depending on whether the defect is located above or below the object to be measured, a pair of vibration spectra due to the defect appears in one of the two fundamental natural vibration spectra. When there is a defect between the top and bottom, the vibration spectrum due to the defect appears as a pair in both of the two basic natural vibration spectra. Therefore, this makes it possible to evaluate whether the defect is located above or below the object to be measured, or in the middle thereof.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. First, the principle of the defect detection method and apparatus according to the present invention will be considered. The method and device of this invention were created as a result of the inventor's research as described below. Now, let us consider, for example, a hollow cylindrical cylinder part made of a cast material as an object to be measured. Vibrations are then applied to the cylinder parts, such as by applying an impact, and these vibrations are picked up by displacement type or vibration detection sensors with sharp directivity. Then, in the case of a hollow cylinder with no defects such as cracks, cavities, or dents, when its natural vibration is analyzed by spectrum, as shown in Figure 1A,
Spectra each having one peak in each order, such as the first order, the second order, etc., are obtained. The frequency at which the peak appears in this spectrum is determined by the shape, material, and size of the object to be measured. On the other hand, if there is a crack penetrating the cylindrical wall of the object to be measured (hereinafter referred to as a crack), 1
When paying attention to the spectrum of odd orders such as the second and third orders, the peak of the spectrum can be observed as two separate peaks. This is because, as shown in Fig. 2, due to the presence of crack 1, the vibration waves propagating on the cylindrical side surface of cylinder 2 cannot pass through the crack 1 and are detoured as shown by dotted line 3 in the figure. This is because the propagation path of vibration becomes longer, and the vibration spectrum due to cracks is produced on the lower frequency side than the basic natural vibration spectrum of the cylinder parts. That is, when only a crack exists in the cylinder part, as shown in FIG. Appears separately. The sum of the energies of both spectra is equal to the energy of the primary spectrum in the case of no crack in FIG. 1A.
The secondary spectrum remains with one peak. In this case, the magnitude (length) of the crack is proportional to the frequency difference _K between the frequency positions of peaks 11 and 12 in the spectrum. Here, the size of the crack refers to the volume of the crack, but if the object to be measured is a cylinder, the thickness is constant and the width of the crack is so small that it can be ignored, so the length of the crack is It will appear. For the cylinder part of this example, it was determined that a frequency difference _K of 5 Hz indicates the presence of a 4 mm long clutch. In addition, when the crack is minute, the Q value of these odd-numbered spectra (= ( ₁ − ₂ ) / ₀ , the third
(see figure) becomes larger and wider. this is,
This is thought to be because the fundamental natural vibration spectrum and the spectrum of vibration caused by the crack are observed as a combination rather than separated due to the frequency resolution of the arithmetic unit. Therefore, the presence or absence of a crack can be determined by detecting the magnitude of the Q value of an odd-order, for example, first-order spectrum. Next, if there is a non-penetrating defect such as a blowhole or dent in the cylinder part of the object to be measured, and if there is no other crack that is a penetrating defect, then As shown, the odd-numbered spectrum, such as the first-order or third-order spectrum, is not divided into two, and non-penetrating defects such as blowholes cannot be detected by only focusing on the odd-numbered spectrum. This is because the vibration that appears as a primary spectrum is a vibration along the circumference, and if it does not penetrate the cylindrical wall, such as in a dent, there is no need for a detour and the vibration does not separate into two peaks. be. However, if we pay attention to the even-order spectrum, for example, the second-order spectrum, we can see that when viewed in the thickness direction, parts such as dents are
After all, you can think of a detour route, so
It can be observed that the spectrum is divided into two parts. In other words, Fig. 1C shows a case where only non-penetrating defects such as cavities and dents exist in the object to be measured, and the secondary spectrum has peak 13 of the basic natural vibration spectrum and peak 14 of the vibration spectrum due to the non-penetrating defect.
The peak is divided into two. In this case as well, the sum of both energies (amplitudes) is equal to that without a non-penetrating defect, and the spectrum of vibration due to a non-penetrating defect is larger than the second-order fundamental natural vibration spectrum for the same reason as above. Appears on the lower frequency side. Again, peaks 13 and 14 in both spectra
The frequency difference _H between the frequency positions where . When non-penetrating defects such as cavities and dents are minute,
As in the case of cracks, the vibration spectrum due to non-penetrating defects is hidden in the second-order fundamental natural vibration spectrum, but since its Q value becomes large, it is possible to detect micro-casting by determining the size of the Q value. It can detect nests and dents. Next, when a through defect such as a crack and a non-penetrating defect such as a cavity or dent exist at the same time (it is often the case that a dent follows a crack), the basic characteristic as shown in Figure 1D. When we look at the first-order spectrum and the second-order spectrum of vibration, both spectra have two peaks. Regarding the primary spectrum,
Peak 15 is the spectrum of the fundamental natural vibration,
A peak 16 below it is a spectrum of vibrations due to a penetrating defect such as a crack. Regarding the secondary spectrum, peak 17 is a spectrum of fundamental natural vibration, and peak 18 below it is a spectrum of vibration due to non-penetrating defects such as dents. However, the size of the non-penetrating defect in this case is
Since the spectrum due to non-penetrating defects is affected by the presence of cracks, which are penetrating defects, the frequency difference between the above two peak positions in the secondary spectrum is
It is obtained by subtracting the frequency difference _K between the two peak positions for the primary spectrum from _H. By the way, in the novel defect detection method described above, the peak value of the spectrum of the fundamental natural vibration and the peak value of the spectrum of vibration due to the defect differ depending on the excitation position relative to the defect position of the object to be measured. In other words, as mentioned above, when vibration is applied, the sum of the energy of the basic natural vibration and the vibration energy of the defective part is constant regardless of the position of vibration.
Since the magnitude of both vibrations differs depending on the excitation position with respect to the defect position, the ratio of the energy (peak value) of the spectrum of both vibrations differs depending on the excitation position. For example, when the object to be measured is a cylinder, considering the change in the peak value of the spectrum for primary vibration, as shown in Fig. For the top, part 1
When the peak value of the primary spectrum of the natural vibration of the object to be measured at each angular position of the circumference is plotted as the magnitude from the center 0 point of the circumference 5, the peak value of the spectrum of the fundamental natural vibration is The trajectory waveform will be a perfect circle if there are no defects (cracks).
If there is a defect in the object to be measured, the spectrum of vibration due to the defect will be as shown in trajectory waveform 6 in Figure 5, and the spectrum of vibration due to the defect will be as shown in trajectory waveform 7. Depending on the position, the peak of the vibration spectrum due to the defect becomes smaller, or vice versa. Both waveforms 6 and 7 repeat the same trajectory almost sinusoidally every 90 degrees, and the phase of change is 45 degrees.
It will be different every time. The reason why waveform 6 or 7 repeats almost the same waveform every 90 degrees is that when a cylindrical object is vibrated at one point, if there is no defect, the primary vibration will be as shown in the dashed line 8 as shown in Fig. 4. The vibration repeats a state like this and a state like the two-dot chain line 9, and the excitation position A
Position B, which is 180 degrees different from , vibrates in exactly the same way,
This is because positions C and D, which are different by 90 degrees from the excitation position A, vibrate in opposite phases. Therefore, each other 90
Even if the vibration is applied at any of the different positions A, B, C, and D, the results shown in FIG. 5 can be obtained. When vibration is applied at an angular position where a defect exists, the energy of the vibration due to the defect is minimized, while the energy of the fundamental natural vibration spectrum is maximized. Therefore, the position where a defect exists, in this case a crack which is a through defect, can be detected as the position where the difference between the two peak values is maximum. In the example of FIG. 5, a crack exists at the position indicated by arrow A. In this way, multiple points are sequentially excited along the circumference of the object to be measured, and the peak value PK1 of the basic natural vibration spectrum and the peak value PK2 of the spectrum of vibration due to cracks at each excitation position are determined, and both peak values are determined. The position where the difference (PK1-PK2) is maximum can be detected as the position where the crack exists. In this case, if the cross-sectional shape of the object to be measured is a circle or an ellipse, the possible positions of cracks are 90
The peak value of the basic natural vibration spectrum is the maximum at four locations with different degrees.
On the other hand, the peak value of the spectrum of vibration caused by cracks is at its minimum. Therefore, if either the locus of the peak value of the fundamental natural vibration spectrum or the locus of the spectrum of vibration due to the crack is known, it is possible to evaluate the four positions where the crack may exist. I can do it. Further, as described above, in the case of FIG. 5, the trajectory drawn by each peak value is repeated in a sine wave shape every 90 degrees. The reason why the locus of the peak value is distorted as shown in Fig. 5 is because the crack is oblique to the axial direction of the cylinder.If the crack is parallel to the axial direction, Draws an approximately equal trajectory every 90 degrees. In addition, you can tell which side the crack is bent by looking at the area occupied by the locus waveform in the repeating locus waveform every 90 degrees drawn by the peak value of the spectrum of vibration caused by the crack. It's curved. In Figure 5, the crack is bent to the right. As mentioned above, the trajectory drawn by the peak value repeats every 90 degrees, so by excitation in the 90 degree angular range, the trajectory waveform in that 90 degree angular range is obtained, and from this, the trajectory for one round is calculated. By estimating the waveform, it is possible to evaluate the location of the crack. That is, in order to reproduce a curved trajectory waveform as shown in FIG. 5, values at at least three points are required. We know that excitation positions 90 degrees apart will only give the same results, so we
If you choose three or more excitation points that are separated by an angle of 90 degrees/3 or less without taking points that are far apart from each other, you can draw a locus waveform of the peak value in the 90 degree angle range. From this, it is possible to infer the trajectory of 360 degrees around the object to be measured. Then, from the analogous waveform, it is possible to evaluate four positions where a crack may exist. Although primary vibration has been considered above, secondary vibration can be similarly performed, and the position of non-penetrating defects such as blowholes and dents can be evaluated. That is, FIG. 6 shows a locus waveform 60 of the peak value of the basic natural vibration spectrum for the secondary spectrum when there is a non-penetrating defect, and a locus waveform 70 of the peak value of the spectrum due to the non-penetrating defect. As is clear from FIG. 6, these trajectory waveforms 6
0,70 is a nearly sinusoidal waveform that repeats every 60 degrees, and the phase of the trajectory waveform of the peak value of the basic natural vibration spectrum and the trajectory waveform of the peak value of the spectrum due to the non-penetrating defect are 30 degrees different from each other. . In this case as well, the position where the difference (PK3 - PK4) between the peak value PK3 of the basic natural vibration spectrum and the peak value PK4 of the vibration spectrum due to the non-penetrating defect is maximum is detected as the location where the non-penetrating defect exists. can do. In the case of Figure 6, arrow B
The position indicated by is the position where the non-penetrating defect exists. Also, in the case of a non-penetrating defect, if the non-measurable object has a circular or elliptical cross-sectional shape, the repeatability of the locus waveform means that the non-measurable object has a cross section of at least 60 degrees. If it is possible to draw a trajectory waveform for the range, it is possible to determine from the trajectory waveform that there is a possibility that a non-penetrating defect exists6.
(360÷6) The location of the location can be evaluated.
In this case, in the case of secondary vibration, the same result will be obtained even if you vibrate at positions 60 degrees apart, so avoid positions that are integral multiples of 60 degrees and excite multiple places. . The waveform in Figure 6 can also be considered as a repeating waveform every 120 degrees, so if the vibration is applied at intervals of 90 degrees/3 or less as described above, the angular range of 120 degrees can be achieved. Since the peak values of the spectrum at four or more excitation points can be obtained, it is possible to draw the locus waveform in FIG. 6 by analogy. From the above, in the case of a measured object with a circular or elliptical cross-sectional shape, such as a cylinder, the angular distance between each other is 90°/3 or less, excluding integral multiples of 90° and integral multiples of 60°. Vibrate at three or more locations at regular intervals, detect the peak value of the spectrum of the fundamental natural vibration of the object to be measured at each excitation position, or the peak value of the spectrum of vibration due to a defect in the object to be measured. From the locus drawn by the peak value at the excitation position, it is possible to evaluate the possible position of a defect in the object to be measured. Next, an embodiment of an apparatus to which the defect position evaluation method described above is applied will be described with reference to the drawings. FIG. 7 shows an embodiment of a defect location identification device to which the method of the present invention is applied, and this example is an example in which a defect in a cylindrical cylinder component is detected and its position is evaluated. A cylinder component as an object to be measured 21 is carried onto a measurement stage 24 and placed thereon by a transfer device 23 controlled by a control device 22 having, for example, a microcomputer. The measurement stage 24 is made of, for example, hard rubber. This measurement stage 24
When it is detected, for example, by a sensor provided on the measurement stage 24 that the object to be measured 21 is placed on the Shake. In this example, the vibration device 25 applies, for example, an impulse impact to the object to be measured 21 with an impact object such as a weight in a pendulum shape. The weight drive mechanism is configured with a cam mechanism or the like so that the weight immediately separates from the object to be measured after the impact. In this case, the vibration device 25 is a cylindrical object to be measured 2.
1, a plurality of locations on its outer peripheral surface are sequentially impacted. These multiple points of impact are
Positions excluding positions separated by integral multiples of 90 degrees and integral multiples of 60 degrees. FIG. 8 is a diagram for explaining an example of a vibrating part of the vibrating device 25, in which FIG. 8A is a cross-sectional view of a cylindrical cylinder, and FIG. 8B is a vertical cross-sectional view. In this example, the object to be measured 21 is sequentially vibrated at five excitation positions P1 to P5 at intervals of 22.5 degrees, as shown in FIG. 8A. Therefore, in this example, the measurement stage 24 is rotatable in a horizontal plane, and the centerline position of the cylindrical object 21 is at the measurement stage 24.
It is aligned and placed so as to match the rotation center position of No. 4. First, the vibrator 25 excites the position P1 of the side surface of the object to be measured 21, and then the measurement stage 24 is rotated by 22.5 degrees, and the position P2 of the side surface of the object to be measured 21 is rotated by 22.5 degrees. The measuring stage 24 is further rotated by 22.5 degrees, and the position P3 of the side peripheral surface of the object to be measured 21 is vibrated, and so on. In addition, in this example, as shown in FIG. 8B, the vibrating part in the axial direction of the object to be measured 21 is located at a position shifted from the center of gravity (the theoretical center of gravity determined from the shape) G, for example, the object to be measured. The upper end position of the object 21 is set to P4. In this way, when vibration is applied at a position shifted from the center of gravity, the mass (weight) is different between the upper half and the lower half of the theoretical center of gravity determined by the shape (generally speaking, all materials are like this). ), another peak appears in the spectrum of the first-order and second-order natural vibrations in addition to the above-mentioned peaks. The frequency position of this peak depends on the mass of the upper and lower halves of the object to be measured 21, with the heavier one (for example, the lower half) at a higher frequency position, and the lighter one (for example, the upper half) at a lower frequency position. A spectrum appears at the position. When the defect is in the upper half, the vibration spectrum due to the defect appears as a pair in the fundamental natural vibration spectrum at the lower frequency position, and when the defect is in the lower half, the fundamental natural vibration spectrum at the higher frequency position appears as a pair. The spectrum of vibrations due to defects appears in pairs. Therefore, it can be determined whether the defect is in the upper half or the lower half of the object to be measured, depending on which fundamental natural vibration spectrum the paired defect spectrum appears in.
If the defect appears on both sides, it can be seen that the defect exists in the center of the object to be measured. As described above, the excited vibration of the object to be measured 21 is detected by the sensor 27 of the output vibration receiving device 26 without contact, converted into an electrical signal, and subjected to predetermined signal processing by the signal conditioner 28. will be done. Any sensor can be used as the sensor 27 as long as it can detect vibrations, and a displacement meter or the like can also be used. However, in order to avoid picking up noise vibrations from the surroundings as much as possible, it is preferable to use one that has sharp directivity in the direction of the object to be measured. The signal conditioner 28 amplifies the electrical signal and also removes unnecessary high and low frequency components (trend removal). In the case of the cast iron cylinder part in this example, the first spectrum of the basic natural vibration among the natural vibrations appears at 1.5kHz, and
This is because the next spectrum appears at about 4kHz, which is about 2.8 times that frequency. The electrical signal from the output vibration receiving device 26 is supplied to the arithmetic processing/determination device 30 via the transmission line 29 . The arithmetic processing/judgment device 30 has, for example, a microcomputer, and performs arithmetic processing and judgment operations, which will be described later, using software, and this processing is illustrated in functional blocks as shown in the figure. By the way, the vibration in question here is the natural vibration of the shape of the object to be measured. However, when the object to be measured is forced to vibrate, the forced vibration initially generates longitudinal waves similar to seismic waves, which are mixed with natural vibrations. If the defect is a fairly large crack or dent, the above method may be able to detect the defect even if vibrations other than these natural vibrations are present. However, normally, if we do not remove vibrations other than these natural vibrations as much as possible,
Defects are difficult to detect. So, in this example, we solve this problem as follows. That is, when exciting the object 21 to be measured, there are the sine wave method and the impulse impact method. In the case of the sine wave method, the object 21 to be measured is vibrated under certain conditions, and at a certain moment, Stop this. Then, vibration measurement is started after a short period of time has elapsed since the stop. In the case of the impulse impact method, measurement is started immediately after a short period of time has elapsed after the vibration is applied, such as by applying an impact. In this case, the time from when the vibration stops or when the impact starts until the measurement starts can be determined as follows. In other words, the velocity c of the sound wave traveling through the object to be measured 21 is its Young's modulus E (elastic modulus).
It depends on the density of the object and the density of the object, and is determined from the relationship c=E/ρ. For example, when using the impulse impact method in this example, if the object 21 is a cylindrical cast iron cylinder, the velocity of the longitudinal wave is 4560 m/s, the transverse wave is 1/1.8 of that, or about 2780 m/s, and the impact The time-series waveform of vibrations picked up immediately after is shown in Figure 9A. In this waveform, the transverse wave is detected after the fast longitudinal wave portion continues for about 26 μsec. Then, after the peak value of the vibration of the transverse wave is passed, the vibration decays exponentially and gradually stops. As can be seen from the waveform in Figure 9A, the vibration after excitation is the same as that of an earthquake wave, so there are both fast longitudinal waves and slow waves as described above, and the vibration Forced vibration remains and the object to be measured 21
It does not have a natural vibration waveform specific to the shape. It is thought that the natural oscillation waves specific to this shape are observed shortly before the spinning top stops, such as in the "sacrificial motion" of a top. Therefore, in this case, vibrations after the point where the transverse wave passes its peak value and begins to attenuate are extracted. For this reason, a rectangular wave window _W1 as shown in FIG. 9B is set, and a vibration wave is extracted in this example using this window _W1 . That is, the electrical signal input to the arithmetic processing/judgment processing device 30 is supplied to the gate means 31.
Then, the natural vibration component of the shape of the object to be measured 21 is extracted from the vibration of the object to be measured 21 after the vibration or impact, using the window signal W ₁ from the window W ₁ forming means 32 . In this example, the window _W1 is started 20 msec after the impact, and the window width is set to 200 msec. Therefore, the window W ₁ is formed in the window W ₁ forming means 32 based on the vibration start information from the control device 22 . As described above, the natural vibration component of the shape of the object to be measured ₁ is extracted using the window W1. Then, the natural vibration part is the A/D conversion means 3
3, it is converted into digital data and stored in the memory means 34.
will be written to. Then, this digital data from the memory means 34 is read out, and the waveform emphasizing means 35 uses an emphasizing window from the window _W2 forming means 36 for this digital data.
W ₂ is multiplied. This highlighting window _W2 is as follows. In other words, the object to be measured ₂₁ is
Even if you extract the natural vibration waveform part specific to the shape of the shape, minute cracks, dents, and cavities are likely to be hidden in the spectrum of the basic natural vibration, and as mentioned above, the only way to detect them is by using the Q value of the spectrum. . Therefore, it is conceivable to make the spread of the spectral waveform "base" of the fundamental natural vibration as small as possible to make it easier to identify cracks and blowholes. In order to do this, the spectrum waveform shown in Figure 3 must be corrected to suddenly attenuate from 50% of the peak (the Q value remains unchanged), as shown by the dotted line 19 in the figure. good. In this way, the "base" of the spectral waveform becomes narrower, and even if there is a minute crack or dent, the minute defect is treated not as the Q value of the spectrum, but as the fundamental natural vibration spectrum and the spectrum of vibrations caused by the defect. This increases the number of things that can be separated and detected. In order to emphasize the spectrum as described above,
It is sufficient to further apply a waveform enhancement window _W2 formed by the following equation to the picked-up vibration waveform. y=acos ² (xωt) +bcos ² (xωt+τ)+ ...+kcos ² (xωt+nτ)+C Here, τ indicates time delay, for example, λ/4
(λ is the wavelength). Also, in this example, a
=b=...=k. This highlighting window
W ₂ has a waveform as shown in FIG. 9C. Figure 10A shows the picked up object to be measured 21.
The above-mentioned natural vibration extraction window
The spectrum of the entire vibration before applying W ₁ and the enhancement window W ₂ is shown. Also, Figure 10B
shows the vibration spectrum extracted 20 msec after the vibration impact of the object to be measured 21 using the natural vibration extraction window _W1 , and separates the basic natural vibration spectrum from the vibration spectrum due to defects. It can be observed. Furthermore, Figure 10C
is the spectrum waveform after applying the above-mentioned enhancement window _W2 , and it can be seen that the fundamental natural vibration spectrum and the vibration spectrum of defects such as cracks or dents are more clearly separated. Similarly to the window W ₁ , the window W ₂ is also controlled by the control device 2 in the window W 2 forming means 36.
It is formed based on the information on the start of vibration from 2. The data thus emphasized is supplied to the spectrum analysis means 37 and subjected to spectrum analysis. FIG. 11A shows the first-order spectrum at the excitation position P1. In the figure, 41 is the object to be measured 2
The spectrum of the fundamental natural vibration for the upper half of 1, 42 is the spectrum of the defect paired with this,
43 is a basic eigenspectrum for the lower half of the object 21 to be measured. Moreover, FIG. 11B shows the first-order spectrum at the excitation position P2. 11th
In FIG. B, the peak value of the vibration spectrum 42 due to the defect has a larger amplitude than the peak value of the basic natural vibration spectrum 43. moreover,
When the measurement stage is rotated by 22.5 degrees and vibrated at position P3, the peak value of the spectrum of the basic natural vibration and the peak value of the spectrum of vibration due to cracks will correspond to the position of excitation to obtain a first-order spectrum. Obtainable. Similarly, FIG. 12A shows the second-order spectrum at the excitation position P1. Here, 51 is a spectrum of fundamental natural vibration for the upper half of the object to be measured 21, and 53 is a spectrum of fundamental natural vibration for the lower half of the object to be measured 21. In this case, defects such as dents are hidden in the spectrum of the fundamental natural vibration. FIG. 12B shows the secondary spectrum at the excitation position P2, which is 22.5 degrees away from the excitation position P1, and the vibration spectrum 52 due to defects is paired with the basic natural vibration spectrum 51 for the upper half of the object to be measured. appears with a large peak. Furthermore, in this case, the vibration spectrum 54 due to the defect appears as a pair in the basic natural vibration spectrum 53 for the lower half of the object to be measured, and the non-penetrating defect exists at an intermediate position in the axial direction of the object to be measured. I understand that. Furthermore, when the measurement stage is rotated by 22.5 degrees and vibrated at position P3, the peak value of the spectrum of the basic natural vibration and the peak value of the spectrum of vibration due to cavities and dents will correspond to the position of excitation. A secondary spectrum can be obtained. Then, the defect presence/absence determining means 38 uses the spectrum obtained as described above to determine the presence of a vibration spectrum due to a defect, for example, in the following manner, thereby determining the presence or absence of a defect. That is, the defect presence/absence determining means 38
As shown in the figure, for example, up to five peak values are determined from the spectrum waveform in the predetermined frequency range of the primary spectrum and frequency ranges d ₁ and d ₂ of the secondary spectrum, in descending order of amplitude. and store the frequency and peak value. Next, regarding the first and second order spectra,
The frequency range in which the spectrum of the fundamental natural vibration and the spectrum of the vibration of the defect are considered to be a pair.
d ₃ , d ₄ (d ₃ , d ₄ < d ₁ , d ₂ ) are determined in advance,
A search is made to see if there is a pair of frequency values of the five peak values within this frequency range d ₃ and d ₄ . Then, when the pair is detected for the primary spectrum, the higher frequency of the pair of lower frequencies is recognized as the primary fundamental natural vibration spectrum position, and the frequency width d is set based on that frequency position. It is determined whether or not there is a peak other than the basic natural vibration spectrum (of course, a pair of peaks may be used) within a predetermined frequency width _d5 that is narrower than ₃ , and if there is a peak, the object to be measured 21
It is determined that there is a crack. Similarly, when a pair of secondary spectra is detected, the higher frequency of the lower frequency pair is recognized as the secondary fundamental natural vibration spectrum position, and the frequency width is It is determined whether there is a peak other than the basic natural vibration spectrum within a predetermined frequency width _d6 narrower than _d4 , and if there is a peak, it is determined that the object to be measured 21 has a blow hole or a dent. . FIG. 14 shows the defect presence/absence determining means 3 described above.
8 shows a flowchart of the operation in 8. When the defect determination means 38 determines that there is a crack (through-hole defect) or a non-through-hole defect such as a cavity or a dent, the position evaluation means 39 evaluates the position. That is, focusing on either the peak value of the basic natural vibration spectrum or the peak value of the vibration spectrum due to a defect at the three excitation positions P1 to P3, the The trajectory waveforms of the peak values of the primary spectrum and secondary spectrum as shown in FIGS. 5 and 6 are estimated and drawn. Then, as described above, based on the trajectory waveform, in the case of a crack, the four positions of every 90 degrees where there is a possibility of its existence are evaluated, and in the case of a casting hole or dent, the existence of the crack is evaluated. Evaluate six possible 60 degree positions. Since the positions P1 to P3 of the defect possible positions evaluated in this way are known, for example, the angle of deviation of one possible defect position with respect to P3 is determined, and the measuring stage 24 is rotated by that amount. For example, by using a marker attachment means (not shown), a mark is printed with paint or the like on the corresponding location on the cylinder of the object to be measured. When printing markers at all four or six possible defect positions, the measurement stage is rotated every 90 degrees or every 60 degrees based on the determined one position, and each defect position is marked. Markers should be placed at possible positions. In this case, for example, a crack (through-hole defect) and a possible position of a non-through-hole defect can be identified by, for example, changing the color of the marker. In the above example, in order to perform evaluation quickly, the number of excitation positions is reduced to a small number, and multiple positions where defects are likely to exist are evaluated. It is also possible to specify the defect position by sequentially vibrating different positions at a predetermined angle over all of the parts. That is, the locus waveform of the peak value of each spectrum is determined in the position evaluation means 39 from the peak value of the basic natural vibration spectrum and the peak value of the spectrum of vibration due to the defect at each excitation position. and,
As described above, the position evaluation means 39 determines the position where the difference between the peak value of the basic natural vibration spectrum and the peak value of the vibration spectrum due to the defect is maximum from these trajectory waveforms, and determines that position as the defect position. It is evaluated as follows. As mentioned above, the spectrum of the fundamental natural vibration and the spectrum of vibration due to defects are divided into two depending on whether the frequency is higher or lower.
It is also possible to evaluate whether the defect is located in the upper half or the lower half of the cylindrical cylinder. In addition, although the above description has been made for the case where the object to be measured is a cylindrical cylinder, the object to be measured may be of any shape, even if it is a hexagonal or other polyhedron, or even a sphere. It's okay. Also,
The material does not matter. In addition, the vibration method is not an impulse impact method,
For example, various vibration excitation methods can be employed, such as fixing one end and biasing the other end to generate vibration.

【Effect of the invention】

As explained above, according to the present invention, the object to be measured is vibrated, the unique vibration of the object to be measured is detected in a non-contact manner by a sensor, and the vibration is spectral analyzed. Possible positions of defects can be easily evaluated. In addition, since this is a method and device that evaluates the defect position by detecting the inherent vibration of the object itself in a non-contact manner, diffused reflection due to misalignment when touching the sensor is avoided, as is the case when the sensor is in contact. The waveform is simple and easy to distinguish. That is,
When detecting the presence or absence of a defect occurring inside the object to be measured and evaluating the defect position, there are few factors that disturb the evaluation, and stable evaluation is possible. Furthermore, according to the present invention, even if the object to be measured has wrinkles or irregularities, as long as they can be distinguished from natural vibrations, defects such as cracks, cavities, dents, etc. can be detected and their positions can be evaluated. It has the characteristic of being able to Further, by simply exciting the object to be measured, it is possible to evaluate the defect position for the entire object to be measured, rather than just a portion of it.

[Brief explanation of the drawing]

FIG. 1 is a spectrum diagram for explaining the detection method according to the present invention, FIG. 2 is a diagram for explaining the detection principle of the present invention, FIG. 3 is a diagram for explaining the Q value, and FIG. 4 is a diagram for explaining the detection principle of the present invention. The figure is a diagram to explain primary vibration.
5 and 6 are diagrams showing examples of trajectory waveforms drawn by the basic natural vibration spectrum and the peak value of the spectrum of vibration due to defects, and FIG. 7 is a block diagram of an embodiment of the defect position evaluation device according to the present invention. Figure, 8th
The figure is an explanatory diagram of the vibrating part, Figures 9 and 10 are diagrams for explaining natural vibration extraction and emphasis,
11 and 12 are diagrams showing examples of spectrum analysis results, FIG. 13 is a diagram for explaining the operation of the example in FIG. 7, and FIG. 14 is an example of the operation of the example in FIG. 7. It is a flowchart. 6... Locus waveform of the peak value of the spectrum of the first-order fundamental natural vibration, 7... Locus waveform of the peak value of the spectrum of the crack vibration, 60... Locus waveform of the peak value of the spectrum of the second-order fundamental natural vibration. ,7
0... Locus waveform of the peak value of the spectrum of the vibration of the blowhole or dent, 11, 15... Spectrum of the first-order basic natural vibration, 13, 17... Spectrum of the second-order basic natural vibration, 12, 16... ... Spectrum of crack vibration, 14,18... Spectrum of vibration of blowholes and dents.

Claims (1)

[Claims] 1. At multiple locations along the periphery of the object to be measured,
Applying vibration to the object to be measured, and determining the peak value PK1 of the basic natural vibration spectrum of the natural vibration of the object to be measured at each vibration position, and the peak value PK2 of the spectrum of vibration due to defects in the object to be measured, From the peak values at each of the plurality of excitation positions, the locus of change in the peak value of the basic natural vibration spectrum and the locus of change in the peak value of the vibration spectrum due to defects in the object to be measured are determined, and the basic natural vibration Defect position evaluation characterized in that the position where the difference (PK1-PK2) between the peak value of the spectrum and the peak value of the spectrum of vibration due to the defect is maximum is evaluated as the position where the defect exists in the object to be measured. Method. 2. An excitation means that sequentially vibrates multiple points along the circumference of the object to be measured, a pickup means that picks up the vibration of the object to be measured and converts it into an electric signal, and a means that receives the electric signal from the pickup means. ,
At each of the excitation positions, the spectrum of the natural vibration of the object to be measured is analyzed, and the peak value PK1 of the basic natural vibration spectrum of the object to be measured and the peak value PK2 of the spectrum of vibration due to defects in the object to be measured are determined. means for determining, from each peak value at each of the plurality of excitation positions, a locus of change in the peak value of the basic natural vibration spectrum and a locus of change in the peak value of the vibration spectrum due to a defect in the object to be measured; And, from the trajectory obtained above, the difference between both peak values (PK1−
A defect position evaluation device comprising means for detecting a position where PK2) is maximum and determining this position as a defect position. 3. When measuring spectra of an object with a circular or elliptical cross section at positions along the cross section at angular intervals smaller than 90°/3 and at odd numbers, 90° x 90° from each other. n (n=0, 1, 2, 3),
In addition, when measuring spectra at even times,
deviated from 60°×m (m=1,2,3,4,5),
Excite three or more locations, pick up the vibrations of the object to be measured at each of the excitation positions, and calculate the peak value of the spectrum of the basic natural vibration of the object to be measured at each of the excitation positions from the picked up vibrations. Alternatively, the peak value of the spectrum of vibration due to the defect in the object to be measured is detected, and the possible position of the defect in the object to be measured is evaluated from the trajectory drawn by the peak value at the plurality of vibration positions. Characteristic defect location evaluation method. 4. A measured object having a circular or elliptical cross section is excited at a position along the cross section and offset from the center of gravity, and at this exciting position, the natural vibration of the measured object is Through spectrum analysis, the spectrum of vibration due to defects that appears paired with the fundamental eigenspectrum is determined by whether it is paired with the fundamental eigenspectrum at a high frequency position or with the fundamental eigenspectrum at a low frequency position.
A defect position evaluation method characterized by evaluating whether the position of the defect is above or below the center of gravity.