JPH11326289A - Method and apparatus for ultrasonic flaw detection of cylindrical body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and an apparatus in which the flaw of a cylindrical body as a whole can be detected with uniform sensitivity in a short time and with good efficiency, by a method wherein an array-type probe which is constituted by arraning a plurality of ultrasonic vibrators is used as a surface- wave probe. SOLUTION: For example, four ultrasonic flaw detection circuits 31 to 34 are connected to a surface-wave probe 20. Twenty ultrasonic vibrators are divided into four groups I to IV while five adjacent elements are used as a unit. Five elements inside every group are connected to one common ultrasonic flaw detection circuit. The four ultrasonic flaw detection circuits 31 to 34 are synchronized, they transmit electric pulses used to transmit surface waves to the four groups I to IV simultaneously, and they simultaneously receive signals captured by the four groups I to IV so as to be amplified to a proper level. An irregularity in the intensity of a surface-wave beam which is transmitted to, and received from, the surface-wave probe 20 is hardly generated, and the flaw of a cylindrical body can be detected with uniform sensitivity in the range of a wide beam width of about 30 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detection method and apparatus for detecting defects such as cracks or the like existing on the surface or directly below a surface of a metal cylinder such as a rolling roll or a roller by surface waves. .

[0002]

2. Description of the Related Art Defects such as cracks existing on the surface of a metal cylindrical body such as a rolling roll or a roller or directly below the surface are detected as described in JP-A-4-27647 and JP-A-5-288734. An ultrasonic flaw detection method using waves (referred to as surface wave flaw detection) has been used. In this surface wave inspection,
A surface wave probe (contact) is brought into contact with the surface of the rotating cylindrical body through a couplant such as water, and the surface wave is propagated from the surface wave probe in a direction opposite to the rotating direction of the cylindrical body. The couplant film is removed from the surface of the cylindrical body where the surface wave propagates, and defects existing on the surface of the cylindrical body or directly below the surface are detected.
In this surface acoustic wave flaw detection, an ultrasonic probe composed of a single-plate ultrasonic transducer and a wedge is usually used as a surface acoustic wave probe.

The above-mentioned Japanese Patent Application Laid-Open Nos.
In the surface wave flaw detection shown in FIG. 288734, a surface wave probe (not shown) is applied to the surface of the rotating cylindrical body 100, and the surface wave probe is scanned in the axial direction of the cylindrical body.
The entire surface of the cylinder is being inspected. At this time, the trajectory drawn by the surface acoustic wave probe on the surface of the cylindrical body 100 has a spiral shape as shown in FIG. 9, and is hereinafter referred to as a spiral scan.

The pitch P of the spiral scan as shown in FIG.
It is determined by the rotational speed R (rpm) of the cylindrical body 100 and the feed speed V (mm / sec) of the probe in the axial direction, and is represented by the following equation.

P = V × 60 / R (1)

For example, when the rotational speed R is 25 rpm and the feed speed V is 5 mm / sec, the pitch P is 12 mm.

[0007]

A surface wave beam transmitted and received from a surface acoustic wave probe composed of a single-plate ultrasonic transducer and a wedge has, for example, a beam intensity within a range of 6 dB or less with respect to the peak intensity. The beam width W needs to be larger than the pitch P of the helical scan in order to thoroughly inspect the surface of the columnar body 100 for flaws. In order to perform flaw detection efficiently in a short time, the larger the beam width W is, the better.

FIG. 10 shows a conventional surface acoustic wave probe (2Z10 × 30) composed of a single-plate ultrasonic flaw detector and a wedge.
It is the result of actually measuring the beam width of the surface wave beam transmitted and received from S) using a vertical drill hole. The range where the beam intensity is within 6 dB with respect to the peak intensity is about 20 mm, and the beam width W can be said to be about 20 mm. However, the fluctuation of the beam intensity within this range is large, and flaw detection is performed with uniform sensitivity. It is hard to say that there is. Further, in order to perform flaw detection with as uniform sensitivity as possible, for example, if a range where the beam intensity is within 3 dB from the peak intensity is defined as a beam width, in the case of FIG. 10, this range is divided into two. However, the beam width becomes an extremely small value.

As described above, in the flaw detection using the surface acoustic wave probe composed of a single-plate ultrasonic vibrator and a wedge, it is actually difficult to detect flaws with uniform sensitivity. If this is to be performed, it is necessary to make the feed pitch P of the spiral scan extremely small, and there is a problem that time-consuming and ineffective flaw detection is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and is intended to detect a defect such as a crack existing on the surface of a metal cylindrical body such as a rolling roll or a roller or just below the surface by a surface wave. Another object of the present invention is to efficiently detect flaws in the entire cylindrical body with uniform sensitivity in a short time.

[0011]

According to the present invention, a surface wave probe for transmitting and receiving a surface wave via a couplant is brought into contact with the surface of a rotating cylindrical body, and the surface wave probe applies the surface wave to the cylindrical body. The ultrasonic wave flaw detection method for detecting a defect by detecting a defect by transmitting a surface wave in a direction opposite to the rotation direction and receiving a reflected wave from a defect existing immediately below the surface of the cylinder or the surface. This problem has been solved by using a linear array type probe in which a plurality of ultrasonic transducers are arranged as a probe.

Further, the plurality of ultrasonic transducers are divided into groups, and ultrasonic waves are transmitted and received simultaneously for each corresponding transducer in each group, thereby enabling particularly quick flaw detection.

[0013] The present invention also relates to a rotating cylindrical body,
A surface wave probe that transmits and receives surface waves via a couplant is brought into contact with the surface wave probe, and the surface wave propagates from the surface wave probe to the cylinder in a direction opposite to the rotation direction, and exists on the surface of the cylinder or directly below the surface. By receiving a reflected wave from a defect to be detected, in the cylindrical ultrasonic inspection device for detecting the defect, the surface acoustic wave probe, a wedge, and a transducer array configured by arranging a plurality of ultrasonic transducers. The above-mentioned problem is also solved by using a linear array type probe composed of:

Further, preferably, the wedge has a bottom surface brought into contact with the surface of the cylindrical body via a couplant, and a normal line to the normal line of the bottom surface is represented by the following equation: θi = sin ⁻¹ (Cw / Cr) (2) (Cw: velocity of the ultrasonic wave in the wedge, Cr: velocity of the surface wave in the cylindrical body) having an inclined surface intersecting at an incident angle θi. The ultrasonic transmitting / receiving surface of the ultrasonic vibrator is attached.

As shown in FIG. 1, a surface acoustic wave probe 20 used for ultrasonic inspection according to the present invention is mainly composed of an ultrasonic transducer array 22 and a wedge 24 made of, for example, a resin. A material 26 is used.

The ultrasonic transducer array 22 includes, for example, lead niobate porcelain, lead titanate porcelain, lithium niobate porcelain, barium titanate porcelain, lead zirconate titanate porcelain, and type 0-3. Composite vibrator (piezoelectric rubber), 1-3 type composite vibrator (vibrator with many small columnar PZTs arranged in epoxy resin plate), 3-1 type composite vibrator (through hole in PZT plate) A piezoelectric vibrator having a low mechanical Q, such as a vibrator hardened by pouring an epoxy resin or the like therein, can be used. Here, the mechanical Q value is an amount representing the sharpness of the resonance vibration, and the longer the Q value, the longer the duration of the vibration.

When the damping material 26 is used,
An object obtained by mixing a powder having a large specific gravity, such as tungsten, with an epoxy resin or the like and hardening the same is attached to the back surface of the ultrasonic vibrator array 22, and the ultrasonic vibration generated in the ultrasonic vibrator array 22 can be damped.

The wedge 24 has an incident angle θi such that the ultrasonic vibration satisfies the above expression (2) and enters the subject.
However, for example, a polystyrene resin, a polyimide resin, an acrylic resin, a fluorine resin (so-called Teflon) or the like can be used.

FIG. 2 is a plan view showing the ultrasonic transducer array 22 in which N ultrasonic transducers 22i having a width WA are arranged without gaps.

FIG. 3 shows the beam width W of the surface acoustic wave transmitted and received from the surface acoustic wave probe 20 constructed as described above.
It is the result measured using the vertical drill hole. As the ultrasonic transducer array 22 constituting the surface acoustic wave probe 20, lead titanate-based porcelain is used, and 20 (N =) ultrasonic transducers 22i having a width WA of 1.5 mm are arranged without gaps. The wedge 24 is made of polyimide resin.

As shown in FIG. 4, for example, four ultrasonic flaw detection circuits 31 to 34 are connected to the surface acoustic wave probe 20, and 20 ultrasonic transducers are connected to five adjacent elements. Divided into four groups I, II, III, IV
Five elements in the group are connected to one common ultrasonic testing circuit. The four ultrasonic flaw detection circuits 31 to 34 are synchronized, transmit electric pulses for transmitting surface waves to four groups I to IV at the same time, and have four groups I to
The signals received by the IV are simultaneously received and amplified to an appropriate level.

As shown in FIG. 3, this surface wave probe 2
It was confirmed that the surface wave beam transmitted and received from 0 had almost no variation in intensity, and that flaw detection was possible with uniform sensitivity over a wide beam width range of about 30 mm.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings.

The present embodiment can be implemented in a flaw detector which supplies a liquid such as water as a propagation medium of an ultrasonic wave between a surface acoustic wave probe and a rolling roll as a test object. In particular, FIG. As shown, the rolling roll 110 will be described with an example suitable for flaw detection by scanning and moving the surface acoustic wave probe 20 on the surface thereof.

This embodiment includes a roll rotating device, a surface acoustic wave probe 20, a probe holder 50, and a water supply device 80.

The roll rotating device moves the rolling roll 110, which is to be inspected for surface defects, in the circumferential direction C
Rotate to. A well-known appropriate device may be used as the roll rotating device, and is not illustrated in order to avoid complication of the drawing.

The surface acoustic wave probe 20 is composed of the lead titanate-based porcelain as vibrators and N = 20 ultrasonic vibrators 22i having a width WA of 1.5 mm arranged without gaps. The surface wave probe 20 can detect a surface defect by transmitting a surface wave to the surface of the rolling roll 110 by forming a water gap between the probe surface and the rolling roll 110 as an object. It is.

The probe holder 50 includes a rolling roll 1
The holding mechanism 60 is provided below the guide 76 that is slidable with respect to the fixed structure 70 positioned above the holding mechanism 60. The holding mechanism 60 includes a pair of front and rear
A total of four rollers 62 are provided, and when performing flaw detection,
These rollers 62 contact the surface of the rolling roll 110 and rotate, thereby stabilizing flaw detection scanning. The probe holder 50 is mounted between the four rollers 62.

The fixed structure 70 is provided with a motor 72 for supplying power for moving the holding mechanism 60 up and down along a guide 76, and a mounting base 74 thereof. As a method of transmitting the power of the motor 72, a conventionally known appropriate means may be used, and illustration is omitted to avoid complication of the drawing.

A scraper 90 for removing the couplant is provided in front of the holding mechanism 60 (to the right in the figure) so that the couplant remaining on the surface of the roll 110 does not flow into the surface wave propagation path. Is provided.

The probe holder 50 includes a holding mechanism 6
By interposing an elastic body such as a spring between the rolling roll 110 and the rolling roll 110, the rolling roll 110 is urged and supported in the surface direction. More specifically, the probe holder 50 is attached to the tip of a rod-shaped body 66 that fits loosely up and down with respect to the holding mechanism 60, and a spring (not shown) is provided at an appropriate position around the rod-shaped body 66. Therefore, the probe holder 50 is constantly urged downward.

The probe holder 50 is provided with the surface wave probe 20.
In order to form a predetermined gap between the rolling roll 110 and the rolling roll 110,
A pair of copying rollers 52 protruding to the 0 side are provided. Specifically, as shown in FIG. 6, a shaft 54 is provided in the probe holder 50 along the horizontal direction, and the copying roller 52 is disposed on the shaft 54.

As described above, the copying roller 52 pivotally supported by the probe holder 50 is urged by the spring,
It is always in contact with the surface of the rolling roll 110. With this configuration, the probe holder 50 holds the surface acoustic wave probe 20 such that the gap between the surface acoustic wave probe 20 and the rolling roll 110 maintains a constant value.

As shown in detail in FIG. 7, a water supply device 80 is provided inside the probe holder 50. The water supply device 80 stores the water guided from the conduit 82 into the accommodation portion 84.
And is discharged from a discharge port 86 provided at the bottom of the storage portion 84 to form a water layer without bubbles between the surface wave probe 20 and the rolling roll 110. Since the water supply device may be configured using conventionally known appropriate means, detailed description will be omitted.

Four ultrasonic testing circuits 31 to 34 are connected to the surface acoustic wave probe 20, and as described with reference to FIG.
Elements are divided into four groups I to IV, and five elements in the group are connected to one common ultrasonic inspection circuit. The four ultrasonic inspection circuits are synchronized, transmit electric pulses for irradiating surface waves to four groups I to IV at the same time, and simultaneously receive signals captured by the four groups I to IV. , To a level at which a defect can be determined.

[0036]

EXAMPLE Using the above embodiment, a roll having minute defects was selected as a test material, and its rotation speed R = 25r.
pm, feed speed V = 1 in the axial direction of the surface wave probe 20
2 mm / sec (helical scanning pitch P = 28.8 at this time)
mm), flaw detection was performed 50 times, and the reproducibility of the defect echo height was examined. As a comparative example, a surface acoustic wave probe (2Z10) composed of a conventional single-plate ultrasonic transducer and a wedge.
× 30S) was also attached to the flaw detector, and the reproducibility of the defect echo height when the same test piece was flaw-detected was also shown. In addition,
In consideration of the beam width of the surface wave, when the conventional probe is used, the rotation speed R = 50 rpm, the feed speed V in the axial direction of the surface wave probe V = 7.5 mm / sec (the pitch P of the helical scan at this time) = 18 mm) for flaw detection. The result is shown in FIG.

As is apparent from FIG. 8, when the flaw detection is performed by the present embodiment (solid line A), the defect echo height hardly changes, whereas in the conventional device (broken line B), A change in the defect echo height of about 6 dB at the maximum is observed, and it can be seen that the entire surface of the roll can be flaw-detected with uniform sensitivity according to the present invention.

Further, in the above comparison, the ultrasonic transducer was used under the condition that the entire width of the ultrasonic transducer was the same between the apparatus of the present embodiment and the conventional apparatus. Excluding the time required for attaching / detaching the test material, it is about 167 seconds in the apparatus of the present embodiment and 266 seconds in the conventional apparatus.

Although the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist thereof.

For example, the ultrasonic transducer 22i, the wedge 24, and the damping material 26 which are members constituting the surface acoustic wave probe
Are not limited to those shown in the above embodiment, and any material having the same function can be used.

Further, in the above embodiment, the case where water is used as the contact medium has been described, but other liquids such as oil may be used.

The object to which the present invention is applied is not limited to a rolling roll, and is not particularly limited as long as it is a cylindrical body such as a roller made of metal or the like.

[0043]

According to the present invention, when detecting defects such as cracks or the like existing on the surface or just below the surface of a metal cylindrical body such as a rolling roll or a roller by a surface wave, the entire surface of the cylindrical body can be detected at a uniform speed. In addition, flaw detection can be performed efficiently in a short time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration example of a surface acoustic wave probe used in the present invention.

FIG. 2 is a plan view seen from the direction of arrow II in FIG. 1;

FIG. 3 is a diagram showing a beam profile and a beam width of the surface acoustic wave probe according to the present invention.

FIG. 4 is a circuit diagram showing an example of grouping of ultrasonic transducer arrays according to the present invention and connection with an ultrasonic testing circuit;

FIG. 5 is a front view showing the overall configuration of the embodiment of the present invention.

FIG. 6 is a side view showing a probe holder part of the embodiment.

FIG. 7 is a cross-sectional view showing a water supply unit.

FIG. 8 is a diagram showing a comparison of the reproducibility of the defect echo height between the embodiment of the present invention and the conventional apparatus.

FIG. 9 is a plan view showing a scanning state of the surface acoustic wave probe on the surface of the cylindrical body.

FIG. 10 is a diagram showing a beam profile and a beam width in a conventional surface acoustic wave probe.

[Explanation of symbols]

 Reference Signs List 20 surface acoustic wave probe 22 ultrasonic transducer array 22i ultrasonic transducer 24 wedge 31-34 ultrasonic testing circuit 50 probe holder 52 copying roller 60 holding mechanism 62 roller 80 water supply device 100 … Cylindrical body 110… Rolling roll

Claims (4)

[Claims] 1. A surface wave probe for transmitting and receiving a surface wave via a couplant is brought into contact with the surface of a rotating cylindrical body, and the surface wave probe contacts the cylindrical body in a direction opposite to the rotation direction. A method for ultrasonic inspection of a cylindrical body for detecting a defect by receiving a reflected wave from a defect existing immediately below the surface of the cylindrical body or the surface, and transmitting a plurality of supersonic waves as the surface wave probe. An ultrasonic flaw detection method for a cylindrical body, comprising using a linear array type probe constituted by arranging ultrasonic transducers. 2. The method of claim 1, wherein the plurality of ultrasonic transducers are divided into groups.
An ultrasonic flaw detection method for a cylindrical body, wherein ultrasonic waves are transmitted and received simultaneously for each corresponding transducer in each group. 3. A surface wave probe for transmitting and receiving a surface wave via a couplant is brought into contact with the surface of the rotating cylindrical body, and the surface wave probe is applied to the cylindrical body in a direction opposite to the rotation direction. While propagating, by receiving a reflected wave from a defect existing immediately below the surface of the cylindrical body or the surface, the ultrasonic flaw detector of the cylindrical body to detect the defect, the surface wave probe, wedge, An ultrasonic flaw detector for a cylindrical body, which is a linear array type probe comprising a transducer array configured by arranging a plurality of ultrasonic transducers. 4. The ultrasonic flaw detector for a cylindrical body according to claim 3, wherein the wedge has a normal to a bottom surface brought into contact with the surface of the cylindrical body via a couplant and a normal to the bottom surface. With an inclined surface intersecting at an incident angle θi defined by the following equation θi = sin ⁻¹ (Cw / Cr) (Cw: velocity of an ultrasonic wave in a wedge, Cr: velocity of a surface wave in a cylindrical body). An ultrasonic flaw detector for a cylindrical body, wherein an ultrasonic transmitting / receiving surface of the ultrasonic vibrator is attached to the inclined surface.