JPH03285143A - Method and apparatus for detecting part different in hardness in measured object - Google Patents

Abstract

PURPOSE:To detect the presence of the different hardness part in an object to be measured by detecting that a spectrum is separated into two spectra from the vibration applied to the matter to be measured and picked up therefrom. CONSTITUTION:The object to be measured placed on a measuring stage 24 is vibrated by a vibrator 25 and the vibration thereof is detected in a non- contact state by the sensor 27 of an output vibration receiving apparatus 26 to be converted to an electric signal. The inherent signal of the object to be measured is subjected to spectrum analysis on the basis of the electric signal by an operational processing/judging apparatus 30 and it is judged whether the peak of the spectrum of vibration due to the different hardness part in the object to be measured is present in the vicinity of the peak of the fundamental inherent vibration spectrum of the object to be measured. When there is a different hardness part in the object to be measured in this spectrum analysis, the spectrum processed by the inherent vibration of the object to be measured in separated into two spectra and, therefore, by detecting said spectra, the presence of the different hardness part can be detected.

Description

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

The present invention relates to a method and apparatus for detecting portions of different hardness in an object to be measured, and is suitable for detecting cracks and chips occurring in the object in advance.

[Conventional technology]

For example, cylinder parts and piston parts used in the piston mechanism of an automobile engine are made of cast metal, but if these parts have defects such as cracks, cavities, or dents, the piston mechanism will fail. Therefore, conventionally, parts having defects such as cracks, cavities, dents, etc. are detected in the parts manufacturing line before assembly of the engine, and are discarded as defective products. Conventionally, methods for detecting and locating this type of defect include:
Method using reflection of ultrasonic waves, detection method using sound when a crack occurs using AE (acoustic emission), CCD
Observation methods using cameras, X-ray photography methods, color check methods, etc. are known.

[Problem to be solved by the invention]

However, even if there are no defects,
For example, if the graphite contained in cast iron is locally spheroidized and has a higher hardness than other parts, there is a risk that the hard part will crack or chip when the part is used, for example, as a piston part. and is dangerous. However, as described above, there has been no method or device for detecting locally high hardness parts in advance, and it has been impossible to remove such parts from the production line. Further, for example, a rolling roller used in a rolling mill has a central portion made of soft iron, and an outer portion that comes into pressure contact with molten high-temperature iron is made of forged iron. This forged iron contains carbon to increase its hardness, but even if there were no unevenly distributed areas of hardness in this forged iron part, the carbon becomes spheroidized due to high heat and pressure.
(diamond formation), resulting in localized hardness areas with high hardness. When a portion of different hardness occurs in this manner, cracks or chips will eventually occur in that portion, resulting in breakage of the rolling roller. However, conventionally, there is no means for detecting the presence of a different hardness portion due to spheroidization in the rolling roller, so conventionally the rolling roller has been replaced after being used for a predetermined period of time in consideration of a safety factor. However, even if a safety factor is taken into account, in some cases, the rolling roller may crack and break due to the occurrence of portions of different hardness before being replaced. Once the rolling roller is broken, it takes a lot of effort and time to restore the rolling mill. Therefore, by detecting the presence of parts with different hardness in the rolling roller,
It is desirable to be able to reliably prevent the rolling roller from breaking. In view of the above points, it is an object of the present invention to provide a method and a device that can detect when there is a portion of a measured object that has a hardness different from other portions.

[Means to solve the problem]

The detection method according to this invention applies vibration to the object to be measured, picks up the vibration,
By detecting that the spectrum of the natural vibration of the object to be measured is divided into two from the picked up vibrations, it is detected that a portion of different hardness exists in the object to be measured. Further, the detection device according to the present invention includes: an excitation means for vibrating the object to be measured; a pickup means for picking up the vibration of the object to be measured and converting it into an electric signal; receiving an electric signal from the pickup means; Analyze the spectrum of the natural vibration of the object to be measured, and determine whether or not there is a peak in the spectrum of vibration due to different hardness parts in the object to be measured, near the peak of the basic natural vibration spectrum of the object to be measured. and means to do so. It is also possible to evaluate the position of a portion of different hardness in the object to be measured, and this method involves applying vibration to the object at multiple points along the circumference of the object, and applying vibration at each excitation position. a peak value PKI of the basic natural vibration spectrum of the natural vibration of the object to be measured;
The peak value PK2 of the vibration spectrum due to the different hardness portions in the object to be measured is determined, and the difference (PKI- The method is characterized in that the position where PK2) is maximum is evaluated as the position where a portion of different hardness exists in the object to be measured. In addition, the device for position evaluation includes an excitation means that sequentially vibrates multiple points along the circumference of the object to be measured, and a pickup means that picks up the vibration of the object to be measured and converts it into an electrical signal. , receives the electrical signal from the pickup means, spectrally analyzes the natural vibration of the object to be measured at each of the excitation positions, and calculates the peak value PKI of the basic natural vibration spectrum of the object to be measured, and the peak value PKI of the basic natural vibration spectrum of the object to be measured. a means for determining a peak value PK2 of a spectrum of vibration due to different hardness portions; a locus of change in the peak value of the basic natural vibration spectrum from each peak value at each of the plurality of excitation positions; A method for determining the locus of change in the peak value of the vibration spectrum due to parts of different hardness, and a method for determining the difference between both peak values (PKl, -PK2) from the locus determined above.
) is at a maximum, and is characterized by comprising means for evaluating this position as a position where a portion of different hardness exists in the object to be measured.

[Effect]

The vibration of the excited object to be measured can be picked up without contact. As a result of the research conducted by the inventor of this invention, when the picked up vibrations are spectral analyzed, if there are parts of different hardness (including foreign objects) in the object to be measured, the spectrum of the natural vibration of the object to be measured is It turned out that it was possible to observe the separation into two parts. This means that the propagation speed of vibration varies depending on the hardness of the material.
This is due to the fact that the higher the hardness, the faster the propagation speed becomes. In other words, if there is a locally high hardness part in the object to be measured, the vibration propagation speed becomes faster in that part, and the energy of the natural vibration of the object to be measured is equal to the energy of the basic natural vibration and the part with high hardness. The vibrational energy is separated into the vibrational energy containing the vibrational energy. Therefore,
As mentioned above, the spectrum of the natural vibration of the measured object is 2
It will be observed separately. Therefore, if a part of the object to be measured is harder than other parts, the spectrum of the natural vibration of the object to be measured will appear divided into a basic natural vibration spectrum and a spectrum on the higher frequency side. Similarly, if a part of the object to be measured is softer than other parts, the spectrum of the natural vibration of the object will be divided into the spectrum of the fundamental natural vibration and the spectrum of lower frequencies. This is what is observed. In this way, the presence or absence of a portion of different hardness in the object to be measured can be detected depending on whether the spectrum of the natural vibration of the object to be measured can be observed separately into two parts. The sum of the energy of the basic natural vibration and the energy of the vibration caused by the different hardness parts is constant regardless of the excitation position, or the magnitude of both vibrations varies depending on the excitation position relative to the position of the different hardness parts. different. Therefore, the ratio of the energy of the spectrum of both vibrations (the peak value of the spectrum) differs depending on the excitation position. When the vibration is applied at the position of the different hardness part, the energy of the vibration due to the different hardness part becomes almost 0, so the peak value of the basic natural vibration spectrum and the peak value of the vibration spectrum due to the different hardness part are different. The difference becomes maximum, and this position can be evaluated as the location of the different hardness portion in the object to be measured.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. First, the principle of the 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 a shock, and these vibrations are picked up by a displacement meter or a vibration detection sensor with sharp directivity. Then, in the case of a hollow cylinder whose hardness is not unevenly distributed, the spectrum analysis of its natural vibration shows that each order is 1st, 2nd, etc., as shown in Figure 12A. A spectrum with one peak is 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, for example, the graphite becomes spheroidized and this part 1 becomes locally extremely hard ( Hereinafter, this part 1 will be referred to as the connected different hardness part 1), 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 existence of the connected different hardness portion 1, the vibration wave 3 propagating on the cylindrical side surface of the cylinder 2 passes through this different hardness portion 10 faster than other parts. This is because the propagation path of vibration passing through 1 becomes shorter, and the spectrum of vibration due to this linked different hardness portion 1 occurs on the frequency side higher than the basic natural vibration spectrum of the cylinder component. That is, when the linked different hardness part 1 exists in the cylinder part 2, as shown in FIG. The peaks 12 of the vibration spectrum due to the different hardness portion 1 appear separately. Here, the sum of the energy of both spectra is equal to the energy of the primary spectrum when there is no different hardness portion in FIG. 1A. 2
In the next spectrum, one peak remains. In this case, the size (length) of the linked different hardness portion is proportional to the frequency difference fK between the frequency positions where peaks 11 and 12 of the spectrum stand.Here, the size of the linked different hardness part is the linked different hardness Refers to the volume of the partial portion. In addition, when the connected different hardness portion is minute, the Q value of these odd-order spectra (= (f + f: )/f
o, see Figure 3) becomes larger and wider. This is thought to be because the fundamental natural vibration spectrum and the spectrum of vibration due to the linked different hardness parts are observed as a combination rather than separated due to the frequency resolution of the arithmetic device. Therefore, by detecting the magnitude of the Q value of the odd-order, for example, first-order spectrum, it is possible to determine the presence or absence of a connected different hardness portion. Next, if there is an unconnected different hardness part in the cylinder part of the object to be measured that is not connected to the cylinder wall surface, if there is no connected different hardness part, as shown in Figure 1C, Odd-numbered spectra, such as first-order or third-order spectra, do not separate into two, and if you focus only on the odd-numbered spectrum, you will not be able to detect uncoupled different hardness portions. This is 1
The vibration that appears as the next spectrum is a vibration along the circumference, and in cases where the vibration does not penetrate the cylindrical wall, such as a non-connected portion of different hardness, the vibration can propagate without passing through this portion of different hardness. This is because the spectrum does not separate into two peaks. However, if we pay attention to the even-order, for example, second-order spectrum, we can consider the path that passes through the unconnected different hardness parts when viewed in the thickness direction.
It can be observed that the spectrum is divided into two. That is, FIG. 1C shows a case where only a non-coupled different hardness part exists in the measured object, and the secondary spectrum is a combination of the peak 13 of the basic natural vibration spectrum and the peak 14 of the vibration spectrum due to the non-coupled different hardness part. The peak is divided into two. In this case as well, the sum of both energies (amplitudes) is equal to that in the case where there is no non-coupled different hardness part, and the spectrum of vibration due to the non-coupled different hardness part is a quadratic fundamental eigenvalue for the same reason as above. It appears higher in frequency than the vibration spectrum. In this case as well, the frequency difference fH between the frequency positions where the peaks 13 and 14 of both spectra stand is proportional to the size of the non-coupled different hardness portion. When the non-coupled differential hardness portion is minute, the spectrum of vibration due to the non-coupled differential hardness portion is hidden in the second-order fundamental natural vibration spectrum, as in the case of the coupled differential hardness portion, but its Q value is Therefore, by determining the magnitude of the Q value, it is possible to detect minute non-coupled different hardness portions. Next, when a connected different hardness part and a non-linked different hardness part exist at the same time, looking at the primary spectrum and secondary spectrum of the fundamental natural vibration, as shown in the first diagram,
Both result in spectra with two peaks. Regarding the primary spectrum, peak 15 is a spectrum of fundamental natural vibration, and peak 16 located above it in terms of frequency is a spectrum of vibration due to linked different hardness parts. Regarding the secondary spectrum, peak 17 is a spectrum of fundamental natural vibration, and peak 18 located below it in terms of frequency is a spectrum of vibration due to non-coupled different hardness parts. however,
In this case, the size of the non-coupled different hardness part is determined from the frequency difference fH between the two peak positions in the secondary spectrum, since the spectrum due to the non-coupled different hardness part is affected by the presence of the linked different hardness part. , is obtained by subtracting the frequency difference fK between the two peak positions for the primary spectrum. By the way, in the novel detection method described above, the peak value of the spectrum of the basic natural vibration and the peak value of the spectrum of vibration due to the different hardness portion differ depending on the excitation position with respect to the position of the different hardness portion of the object to be measured. In other words, as mentioned above, when the vibration is applied, the sum of the energy of the basic natural vibration and the energy of the vibration passing through the part with different hardness is constant regardless of the position of vibration, but when the vibration is applied to the position of the part with different hardness, Since the magnitude of both vibrations differs depending on the 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 the first-order vibration, the fifth
As shown in the figure, the excitation position is set on the circumference 5 along the outer circumference of the cylinder, and the peak value of the primary spectrum of the natural vibration of the object to be measured at each angular position for one circumference is calculated as follows:
When plotted as the size from the center 0 point of the circumference 5, the locus waveform of the peak value of the spectrum of the fundamental natural vibration will be a perfect circle unless there is a different hardness part (in this case, a connected different hardness part) Become. If the object to be measured has a portion of different hardness, the trajectory waveform 6 in FIG.
At an excitation position where the peak of the spectrum of the fundamental natural vibration is large, the peak of the spectrum of vibration passing through a portion of different hardness becomes small, or vice versa. And both waveforms 6
and 7 repeat the same locus almost sinusoidally every 90 degrees, and the phases of change differ from each other by 45 degrees. 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 are no parts with different hardness, the primary vibration is - as shown in Figure 4. The vibration repeats the state shown by the dotted chain line 8 and the state shown by the double dotted chain line 9, and the position B is 180 degrees different from the excitation position A.
vibrates in exactly the same way, and the position C1D, which is 90 degrees different from the excitation position A, vibrates in the opposite phase. Therefore, even if the vibration is applied at any of the positions A, B, C, and D that are different from each other by 90 degrees, the result shown in FIG. 5 can be obtained. When vibration is applied at an angular position where a portion of different hardness exists, the energy of the vibration due to the portion of different hardness becomes minimum, while the energy of the fundamental natural vibration spectrum becomes maximum. Therefore, the position where the different hardness portion, in this case, the linked different hardness portion, exists can be detected as the position where the difference between the two peak values is maximum. In the example shown in FIG. 5, a connected different hardness portion exists at the position indicated by arrow A. In this way, a plurality of locations are sequentially excited along the circumference of the object to be measured, and the peak value PKI of the basic natural vibration spectrum at each excitation position and the peak value PK2 of the spectrum of vibration due to the linked different hardness parts are determined, Difference between both peak values (PK
The position where I-PX3) is maximum can be detected as the position where the connected different hardness portion exists. In this case, if the cross-sectional shape of the object to be measured is a circle or an ellipse, as shown in FIG. At these four locations, the peak value of the basic natural vibration spectrum is the maximum, while the peak value of the vibration spectrum due to the linked different hardness portion is the minimum. Therefore, if either the locus of the peak value of the basic natural vibration spectrum or the locus of the spectrum of vibration due to the linked different hardness part is known, then the four positions where the linked different hardness part may exist can be determined. can be evaluated. 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 trajectory of the peak value is distorted as shown in Figure 5 is because the connected different hardness portion is oblique to the axial direction of the cylinder, and the connected different hardness portion is parallel to the axial direction. If it is, approximately equal trajectories are drawn every 90 degrees. In addition, to which side the connected different hardness parts are bent,
In the repeating locus waveform every 90 degrees drawn by the peak value of the vibration spectrum due to the connected different hardness portion, it can be determined by the area occupied by the locus waveform, and the larger the area, the more curved the connected different hardness portion. In FIG. 5, the connected different hardness portions are curved 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 connected different hardness portion. 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 can use 90 degrees, 180 degrees, 27 degrees,
Avoid taking points that are 0 degrees apart from each other, (90
÷3) If you select 3 or more excitation points with angle layers under the measurement, 9
It is possible to draw a trajectory waveform of the peak value in the 0 degree angle range, and from this it is possible to infer a trajectory of 360 degrees around the object to be measured. Then, from the analogous waveform, it is possible to evaluate four positions where there is a possibility that a connected different hardness portion exists. Although the above discussion has focused on primary vibration, the same applies to secondary vibration, and the position of non-coupled and different hardness parts can be evaluated. In other words, in Fig. 6, 2 when there is a non-connected different hardness part.
A locus waveform 60 of the peak value of the basic natural vibration spectrum for the next spectrum and a locus waveform 70 of the peak value of the spectrum due to the non-coupled different hardness portion are shown. As is clear from FIG. 6, these trajectory waveforms 60 and 7
0 repeats a nearly sinusoidal waveform every 60 degrees, and 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-coupled different hardness portion have a phase difference of 30 degrees from each other. ing. In this case as well, the position where the difference (PX3-PX4) between the peak value PK3 of the basic natural vibration spectrum and the peak value PK4 of the spectrum of vibration due to the non-coupled different hardness part is the maximum is selected for the non-coupled different hardness part. It can be detected as the location. In the case of FIG. 6, the position indicated by arrow B is the position where the non-coupled differential hardness portion exists. In addition, in the case of non-coupled different hardness parts, if the object to be measured has a circular or elliptical cross-sectional shape, the repeatability of the trajectory waveform can be evaluated in the same way as in the case of the linked different hardness parts. If it is possible to draw a locus waveform with an angular range of at least 60 degrees, it is possible to evaluate from the locus waveform the positions of 6 (-360÷6) locations where non-coupled different hardness portions may exist. 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 Fig. 6 can also be considered as a repeating waveform every 120 degrees, so as mentioned above, the waveform is repeated every 120 degrees.
If the vibration is applied at intervals of 3 or less angles, the peak values of the spectrum at 4 or more vibration points can be obtained in an angular range of 120 degrees, so draw the locus waveform in Figure 6 by analogy. It is possible. From the above, in the case of a measured object with a circular or elliptical cross section, such as a cylinder, the angular interval between them is an integral multiple of 90 degrees and 6
Excite at least three locations at angular intervals of 90@/3 or less, excluding integral multiples of 0 degrees, and calculate 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 the fundamental natural vibration of the object to be measured at each excitation position. By detecting the peak value of the vibration spectrum due to the different hardness portion, it is possible to evaluate the possible existence position of the different hardness portion in the object from the locus drawn by the peak values at the plurality of excitation positions. Next, an embodiment of an apparatus to which the method of detecting a portion of different hardness and the method of evaluating the position of a portion of different hardness described above is applied will be described with reference to FIG. 7 and subsequent figures. FIG. 7 shows an embodiment of a device for detecting a portion of different hardness to which the method of the present invention is applied. This example is an example of detecting a portion of different hardness in a cylindrical cylinder part and evaluating its position. be. A cylinder component as an object to be measured 21 is carried onto a measurement stage 24 and placed thereon by a transport device 23 controlled by a control device 22 having, for example, a microcomputer. The measurement stage 24 is made of, for example, hard rubber. Then, the n1 constant object 2 is placed on 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, the control device 22 drives the vibration device 25 to vibrate the object to be measured 21. In this example, the vibration device 25 applies, for example, an impulse shock to the object to be measured 21 with an impact object such as a weight. 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 configured to sequentially impact the cylindrical object 21 at a plurality of locations on its outer peripheral surface. This multiple impact points are integral multiples of 90 degrees and 6
This is a position excluding positions that are an integer multiple of 0 degrees away. FIG. 8 is a diagram for explaining an example of a vibrating part of the object to be measured 21 in the vibration excitation device [25], in which FIG. 8A is a cross-sectional view of a cylindrical cylinder, and FIG. 8B is a longitudinal 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 cylindrical object 21 is positioned and mounted so that its center line matches the rotational center position of the measurement stage 24. placed. First, the position P1 of the side peripheral surface of the object to be measured 21 is excited by the vibration device 25, and then the measurement stage 24
is rotated 22.5 degrees, and the position P2 of the side circumferential surface of the object to be measured 2 is
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 2 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, this is the case with all materials). ), 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 is
It depends on the mass of the upper and lower half of , and the heavier one (
For example, the lower half of the spectrum appears at a higher frequency position, and the lighter side (for example, the upper half) appears at a lower frequency position. Then, when the different hardness part is in the upper half, the vibration spectrum due to the different hardness part appears as a bare part in the basic natural vibration spectrum at the low frequency position, and when the different hardness part is in the lower half, , the vibration spectrum due to the different hardness portion appears as a bare spectrum in the basic natural vibration spectrum at a high frequency position. Therefore, depending on which fundamental natural vibration spectrum the spectrum of the bare different hardness portion appears, it can be determined whether the different hardness portion is in the upper half or the lower half of the object to be measured. If it appears in both, it can be seen that a portion of different hardness exists in the axially intermediate portion of the object to be measured. The vibration of the object to be measured 21 excited in the above manner is
It is detected in a non-contact manner by the sensor 27 of the output vibration receiving device 26, converted into an electrical signal, and sent to the signal conditioner 28.
Predetermined signal processing is performed at . As the sensor 27, any sensor can be used as long as it can detect vibrations, and a displacement meter or the like may 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. In the signal conditioner 28, the electrical signal is amplified, and unnecessary high and low acid components are removed (trend removal). In the case of the cast iron cylinder part in this example, the primary spectrum of the fundamental natural vibration appears at, for example, 1.5kHz, and the secondary spectrum appears at about 2.5kHz.
This is because it appears at approximately 4kHz, which is eight times as high. 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 shown 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 it is a considerably large connected or non-coupled different hardness portion, it may be possible to detect the different hardness portion by the above method even if vibrations other than these natural vibrations are mixed. However, it is usually difficult to detect portions of different hardness unless vibrations other than these natural vibrations are removed as much as possible. So, in this example, we solve this problem as follows. In other words, when exciting the object 21 to be measured, there are the sine wave method and the impulse impact method, but in the case of the sine wave method, the object 21 to be measured is vibrated under certain conditions, and at a certain moment, the object 21 is vibrated. stop. 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 from the time of impact to the start of measurement can be determined as follows. That is, it is determined from the fact that the velocity C of the sound wave traveling through the object to be measured 21 depends on its Young's modulus E (elastic modulus) and the density of the object, and there is a relationship of V 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, and the velocity of the transverse wave is 1/1.8 of that.
The velocity was approximately 2780 m/s, and the time-series waveform of vibrations picked up immediately after the impact was as shown in Figure 9A. In this waveform, one minute of only the fast longitudinal wave is about 26 μsec.
After c, a transverse wave is detected. 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 a natural vibration waveform specific to the shape of the object to be measured 21 is not formed. 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. So, in this case,
The vibrations after the point where the transverse wave reaches its peak value and begins to decay are extracted. For this reason, a rectangular wave window WI as shown in FIG. 9B is set, and a vibration wave is extracted in this example using this window WI. That is, the electrical signal input to the arithmetic processing/judgment processing device 30 is supplied to the gate means 31. Then, using the window signal W1 from the window W and forming means 32, 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. In this example, 20111se immediately after the impact
Start window W1 after c elapses and set 200
Set the m5ec window width. Therefore, the window W and the forming means 32 form the window W□ 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 converted into digital data by the A/D conversion means 33 and written into the memory means 34. Then, this digital data is read from the memory means 34, and in the waveform emphasizing means 35, an emphasizing window W2 from the window W2 forming means 36 is applied to this digital data. This emphasis window W2 is as follows. That is, even if the natural vibration waveform part specific to the shape of the object to be measured 21 is extracted using the window W1, the minute linked different hardness parts and unlinked different hardness parts are likely to be hidden in the spectrum of the basic natural vibration. As mentioned above, the only way to detect it is to use the Q value of the spectrum. Therefore, the spectral waveform of the fundamental natural vibration should be
It is conceivable to make the width of the "base" smaller to make it easier to judge connected and uncoupled different hardness parts. To do this, the spectrum waveform as shown in Figure 3 should be started from 50% of the peak (Q
(The value does not change) You can apply a correction to rapidly attenuate it. In this way, the "base" of the spectral waveform becomes narrower, and even if there is a minute linked or non-coupled different hardness part, that minute different hardness part is used instead of the Q value of the spectrum.
In many cases, it is possible to separate and detect the basic natural vibration spectrum and the vibration spectrum due to different hardness parts. 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-acos2 (xωt) +bcos2 (x tt)t+r)+---+k
cos 2 (x ω t+nr) + smile, τ
indicates a time delay, for example, λ/4 (λ is wavelength). Further, in this example, it is set to a-b-...-. This emphasis window W2 has a waveform as shown in FIG. 9C. FIG. 10A shows the spectrum of the entire vibration before applying the above-mentioned natural vibration extraction window W and emphasis window W2 to the vibration of the picked up object 21 to be measured. In addition, FIG. 10B shows the spectrum of vibration extracted from the natural vibration extraction window WI after 20 m5 ecu from immediately after the impact of the vibration of the object to be measured 21, showing the basic natural vibration spectrum and the vibration due to different hardness parts. Separation from the spectrum can be observed. Furthermore, the 10th
Figure C shows the spectrum waveform after applying the above-mentioned emphasis window W2, and it can be seen that the fundamental natural vibration spectrum and the vibration spectrum due to the linked different hardness part or the non-linked different hardness part are separated more clearly. . Similarly to the window W1, the window W2 is also formed by the window front 2 forming means 36 based on the vibration start information from the control device 22. The data thus emphasized is supplied to 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 spectrum of the basic natural vibration of the upper half of the object to be measured 21, 42 is the spectrum of the different hardness portion which is bare from this spectrum, and 43 is the basic natural spectrum of the lower half of the object to be measured 21. Also, the first
FIG. 1B shows the first-order spectrum at the excitation position P2. In Fig. 11B, the peak value of the vibration spectrum 42 due to the different hardness portion or the basic natural vibration spectrum 43
The amplitude is larger than the peak value of . 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 the linked different hardness portion, or the peak value of the spectrum of vibration due to the linked different hardness portion, or A first-order spectrum can be obtained. Similarly, FIG. 12A shows the second-order spectrum at the excitation position P1. Here, 51- is a spectrum of basic natural vibration for the upper half of the object to be measured 21, and 53 is a spectrum of basic natural vibration for the lower half of the object to be measured 21. In this case, the uncoupled hardness portion is hidden in the spectrum of the fundamental natural vibration. FIG. 12B shows the second-order spectrum at the excitation position P2, which is 22.5' apart from the excitation position P1. The spectrum 52 appears as a bare spectrum with a large peak. In addition, in this case, the vibration spectrum 54 due to the different hardness portion appears as a bare spectrum in the fundamental natural vibration spectrum 53 of the lower half of the object to be measured, and the non-coupled different hardness portion is located in the axial direction of the object to be measured. It can be seen that it exists in the position. Furthermore, when the measurement stage is rotated 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 the non-coupled different hardness portion change according to the position of excitation. It is possible to obtain a secondary spectrum that is useful. Then, the different hardness portion presence/absence determination means 38 uses the spectrum obtained as described above to determine the presence of a vibration spectrum due to the different hardness portion, for example, in the following manner, and determines the presence or absence of the different hardness portion. . That is, as shown in FIG. 13, the different hardness portion presence/absence determining means 38 determines the amplitude within the predetermined frequency range of the primary spectrum and the frequency range of the secondary spectrum d, d2 from the spectrum waveform. For example, five peak values are determined in descending order of frequency and the peak values are stored. Next, regarding the first-order and second-order spectra, the frequency range d3 is considered to be bare between the spectrum of the basic natural vibration and the spectrum of the vibration of the different hardness portion. d4 (d3.d4 <d,. d2) is determined in advance, and this frequency range d3°d4
A search is made to see if there is a bare frequency value among the five peak frequency values. When that bear is detected for the primary spectrum, the lower frequency of the bears with lower frequencies is recognized as the position of the primary fundamental natural vibration spectrum, and the frequency width d3 is set based on that frequency position. a narrower predetermined frequency width d. It is determined whether or not there is a peak other than the basic natural vibration spectrum (of course, a bare peak may be used), and if there is a peak, it is determined that the object to be measured 21 has a connected different hardness portion. Similarly, for the secondary spectrum, when the bear is detected, the lower frequency of the lower frequency bears is
It is recognized as the next basic natural vibration spectrum position, and based on that frequency position, it is determined whether there is a peak other than the basic natural vibration spectrum within a predetermined frequency width d6 narrower than the frequency width d4. , if there is a peak, it is determined that the object to be measured 21 has a non-coupled, different hardness portion. FIG. 14 shows the different hardness portion presence/absence determining means 38 explained above.
A flowchart of the operation in is shown. When the different hardness portion presence/absence determining means 38 determines that there is a connected different hardness portion or that there is a non-connected different hardness portion,
The position evaluation means 39 evaluates the position. However, if the different hardness portion presence/absence determining means 38 determines that there is a different hardness portion, the object to be measured may be considered a defective product and removed from the line at this stage. The position evaluation means 39 focuses on either the peak value of the basic natural vibration spectrum at the three excitation positions P1 to P3 or the peak value of the vibration spectrum due to the different hardness portion, and calculates the value of the cylinder that is the object to be measured. The trajectory waveforms of the peak values of the primary spectrum and secondary spectrum as shown in FIGS. 5 and 6 for the side peripheral surface are estimated and drawn. Then, as mentioned above, from the trajectory waveform,
In the case of connected parts with different hardness, there are 9
Four positions at every 0 degrees are evaluated, and in the case of a non-coupled differential hardness portion, 611 positions at every 60 degrees where there is a possibility of its existence are evaluated. Then, since the positions P] to P3 of the positions where the different hardness part can exist evaluated in this way are known, for example, the angle of deviation of one possible position of the different hardness part with respect to P3 from the current position is calculated. , the measurement stage 24 is rotated by that amount, and, for example, a mark is printed with paint or the like on the corresponding location on the cylinder of the object to be measured using a marker attachment means (not shown). When printing markers at all four or six locations where parts with different hardness can exist, rotate the measuring stage every 90 degrees or every 60 degrees based on the determined one location. A marker is attached to a position where a portion of different hardness can exist. In this case, for example, the possible locations of the connected different hardness portions and the non-linked different hardness portions can be identified by, for example, changing the color of the marker. In the above example, in order to quickly perform evaluation, the number of vibration positions is reduced to a small number, and multiple positions where parts of different hardness can exist are evaluated. It is also possible to specify the position of a portion with different hardness by sequentially vibrating different positions by a predetermined angle over the entire circumference. 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 at each excitation position and the peak value of the vibration spectrum due to the different hardness portion. Then, from these trajectory waveforms, 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 different hardness portion is maximum, and determines the position. The position is evaluated as a position of a part with different hardness. As mentioned above, the spectrum of the basic natural vibration and the spectrum of vibration due to different hardness parts are divided into two because
Depending on whether the frequency is higher or lower, it can also be evaluated whether there is a different hardness portion in the upper half or the lower half of the cylindrical cylinder. Note that the above explanation is based on the case where the object to be measured is a cylindrical cylinder, but the object to be measured may be of any shape, such as a hexagonal or other polyhedron, or even a sphere. It's okay. Moreover, the material does not matter. Further, even if the different hardness portion is not a portion harder than other portions as described above, but a portion softer than other portions, detection and position evaluation can be performed. In that case, the spectrum of vibration due to the different hardness portion appears lower in frequency than the spectrum of the fundamental natural vibration, since the speed of vibration passing through this soft different hardness portion is slow. Furthermore, the present invention is applicable even if the different hardness portion is a foreign object having a hardness different from that of the object to be measured. In addition, the vibration method is not an impulse impact method, and various vibration methods can be used, such as fixing one end and applying a bias to 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 sensor detects the inherent vibration of the object itself in a non-contact manner, and the spectrum analysis of the vibration is performed to detect parts of different hardness. The presence or absence of can be easily detected. Therefore, even if there are no defects such as cracks in appearance,
Quality control can be performed by predicting the occurrence of cracks in the future. In particular, if this invention is applied to the maintenance and inspection of rolling rollers, which gradually develop cracks and cracks during use during use, it is possible to ensure that the parts of different hardness are removed before cracks occur. By detecting the occurrence of parts, it is possible to prevent damage to the parts. Moreover, this invention allows detection and position evaluation of parts of different hardness without contact, simply by vibrating the object to be measured, so even if the object to be measured is difficult to remove, such as a rolling roller, It is possible to easily check the detection of parts with different hardness. Further, according to the present invention, by exciting multiple locations around the object to be measured and performing spectrum analysis of the vibration data at each location, it is possible to easily evaluate the location of a portion with different hardness or the possible location of a portion with different hardness. be able to. In addition, by detecting the inherent vibration of the object to be measured without contact, it is possible to detect parts with different hardness and evaluate their positions.
There is no diffuse reflection due to misalignment when the sensor contacts, and the waveform is simple and easy to distinguish. That is, when detecting the presence or absence of a portion of different hardness occurring inside the object to be measured and evaluating the position of the portion of different hardness, 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, if they can be distinguished from natural vibrations, a portion of different hardness can be detected without being affected by the wrinkles or irregularities, and the position thereof can be evaluated. It has the characteristic of being able to Further, by simply vibrating the object to be measured, it is possible to evaluate the position of a portion with different hardness for the entire object to be measured, rather than just a portion thereof.

[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. The figure is a diagram for explaining primary vibration, Figures 5 and 6 are diagrams showing examples of locus waveforms drawn by the basic natural vibration spectrum and the peak values of the spectrum of vibration due to different hardness parts, and Figure 7 is a diagram for explaining primary vibration. , a block diagram of an embodiment of the device for detecting a portion of different hardness according to the present invention, FIG. 8 is an explanatory diagram of the vibrating part, FIGS.
Figure 1 is a diagram for explaining natural vibration extraction and emphasis.
1 and 12 are diagrams showing examples of spectrum analysis results, FIG. 13 is a diagram for explaining the operation of the example in FIG.
FIG. 4 is a flowchart of an example of the operation of the example in FIG. 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 vibration passing through the connected different hardness portion 60; Locus waveform of the peak value of the spectrum of the second-order fundamental natural vibration 70 ; Trajectory waveform of the peak value of the spectrum of vibration passing through the uncoupled hardness portion 11.15; Spectrum of the first-order fundamental natural vibration 13.1
7; Spectrum of second-order basic natural vibration 12.16; Spectrum of vibration due to connected different hardness parts 1.4.18 + Spectrum of vibration due to unlinked different hardness parts

Claims (4)

[Claims] (1) By applying vibration to the object to be measured, picking up the vibration, and detecting from the picked up vibration that the spectrum of the natural vibration of the object to be measured is divided into two, A method for detecting a portion of different hardness in an object to be measured, which detects the presence of a portion with a hardness different from that of the object to be measured. (2) an excitation means for vibrating the object to be measured; a pickup means for picking up the vibration of the object to be measured and converting it into an electrical signal; and means for analyzing the spectrum of vibration and determining whether or not a peak of a spectrum of vibration due to a portion of different hardness in the object to be measured exists in the vicinity of a peak of a basic natural vibration spectrum of the object to be measured. A device for detecting parts of different hardness in the object to be measured. (3) Vibration is applied to the object to be measured at multiple locations along the circumference of the object to be measured, and the peak value PK of the fundamental natural vibration spectrum of the natural vibration of the object to be measured at each vibration position
1 and the peak value PK2 of the vibration spectrum due to the different hardness portions in the object to be measured, and the difference between the peak value PK1 of the basic natural vibration spectrum and the peak value PK2 of the vibration spectrum due to the different hardness portions. (PK1-PK2
) is the maximum position is evaluated as the location of the different hardness portion in the object to be measured. (4) Excitation means that sequentially vibrates multiple points along the circumference of the object to be measured; Pick-up means that picks up the vibrations of the object to be measured and converts them into electrical signals; and Electric signals from the pickup means. Then, at each of the excitation positions, the natural vibration of the object to be measured is analyzed spectrally, and the peak value PK1 of the basic natural vibration spectrum of the object to be measured and the spectrum of vibration due to different hardness parts in the object to be measured are determined. a means for determining a peak value PK2 of the above-mentioned basic natural vibration spectrum from each peak value at each of the plurality of excitation positions; A means for determining the locus of change in peak value, and the difference between both peak values (PK1-PK2) from the locus determined above.
1. An apparatus for detecting a portion of different hardness in an object to be measured, comprising means for detecting a position where the hardness is at a maximum, and evaluating this position as a position where a portion of different hardness exists in the object to be measured.