JP2012063325A - Laser ultrasonic inspection device and laser ultrasonic inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser ultrasonic inspection technique for performing nondestructive inspection of an inspection object whose surface shape is complicated at a high speed with high precision.SOLUTION: A laser ultrasonic inspection device 10 includes a transmission laser head 21 which irradiates the inspection object K with first laser light R1 to excite an ultrasonic wave; a reception laser head 22 which performs irradiation with second laser light R2 to detect an ultrasonic wave propagated in the inspection object K; a signal processing part which images a defect included in the inspection object K based upon the ultrasonic wave detected by the reception laser head 22; and an angle adjustment part 13 which adjusts angles of incidence of the first laser light R1 and second laser light R2 on the surface of the inspection object K.

Description

  The present invention relates to a laser ultrasonic inspection technique for irradiating a laser beam onto an inspection target to excite ultrasonic waves on the inspection target, detecting an echo of the ultrasonic wave, and examining an existing defect or the like.

  As a technique for nondestructively examining defects or the like to be inspected, an ultrasonic flaw detection technique for performing an inspection by bringing a piezoelectric probe into contact with the inspection object is conventionally known. However, this ultrasonic flaw detection technique has a problem that it is difficult to bring the piezoelectric probe into contact with the surface of the inspection object when the inspection object is a high temperature or a complicated structure. .

  As a technique for solving such a problem, in recent years, a laser ultrasonic flaw detection technique in which the action of a piezoelectric probe is replaced with a laser beam has attracted attention. According to this laser ultrasonic flaw detection technology, compared to the ultrasonic flaw detection method using a piezoelectric probe, non-destructive inspection of an inspection target can be performed remotely and non-contact, and no contact medium is required. There is an advantage that it is difficult to be influenced by the shape and surrounding environment (see, for example, Patent Documents 1 and 2).

JP-A-11-271281 JP 2005-195594 A

  By the way, when the laser ultrasonic inspection technology is applied to an inspection object with a complicated surface shape, the inspection time is prolonged due to the low receiving sensitivity of the laser beam, or the beam diameter of the irradiated laser is affected by the surface shape. There is a problem in that the accuracy of defect flaws decreases due to changes in the beam path and the optical path length of the beam.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a laser ultrasonic inspection technique for performing nondestructive inspection of an inspection object having a complicated surface shape at high speed and high accuracy.

  The laser ultrasonic inspection apparatus of the present invention detects a transmission laser head that irradiates an inspection target with a first laser to excite the ultrasonic wave, and an echo of the ultrasonic wave that irradiates a second laser and propagates through the inspection target. Receiving laser head, a signal processing unit for imaging a defect included in the inspection object based on the detected echo, and incident angles of the first laser and the second laser with respect to the surface of the inspection object And an angle adjustment unit for adjustment.

  According to the present invention, there is provided a laser ultrasonic inspection technique for performing nondestructive inspection of an inspection target having a complicated surface shape at high speed and with high accuracy.

(A) The side view of the laser ultrasonic inspection apparatus which shows 1st Embodiment of this invention, (B) The top view. 1 is a block diagram of a laser ultrasonic inspection apparatus according to a first embodiment. The graph which shows the signal level of the ultrasonic wave detected by the laser ultrasonic inspection apparatus which concerns on embodiment. The block diagram of the laser ultrasonic inspection apparatus which concerns on 2nd Embodiment. (A) The side view of the laser ultrasonic inspection apparatus which shows 3rd Embodiment of this invention, (B) The operation | movement explanatory drawing. (A) Side view of a laser ultrasonic inspection apparatus equipped with a crosstalk prevention wall in the first embodiment, (B) Side view of a laser ultrasonic inspection apparatus equipped with a crosstalk prevention wall in the third embodiment. The side view of the laser ultrasonic inspection apparatus which concerns on 4th Embodiment of this invention.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, the laser ultrasonic inspection apparatus 10 of the first embodiment irradiates a transmission laser head 21 that irradiates an inspection target K with a first laser R1 and excites ultrasonic waves, and a second laser R2. A receiving laser head 22 for detecting an ultrasonic echo propagating through the inspection target K, a signal processing unit 30 (FIG. 2) for imaging a defect included in the inspection target K based on the detected echo, and an inspection And an angle adjusting unit 13 that adjusts the incident angles of the first laser R1 and the second laser R2 with respect to the surface of the target K.

  Then, the laser ultrasonic inspection apparatus 10 operates in association with each function unit shown in FIG. 2 according to input information from the operation terminal 31 and a program executed by the microprocessor (control unit 32). The defect included in the image is detected, and the defect information is imaged.

In the description of each embodiment, the inspection target K is assumed to be an aircraft body or the like made of a carbon fiber composite material. In the defect inspection by the laser ultrasonic inspection apparatus 10 for such a carbon fiber composite material, a peeling defect generated in a material formed in a layer form with resin and carbon fiber is a main inspection object.
In addition, the inspection object K can also be applied to defect inspection such as welding defects and stress corrosion cracking in various components made of SUS such as piping in large plants such as nuclear power plants. In addition, various materials such as other metals and ceramics can be used.

  The probe 20 fixes and holds the transmission laser head 21 and the reception laser head 22. In FIG. 1, the reception laser head 22 is linearly arranged on one side of the transmission laser head 21, but the reception laser head 22 may be arranged on both sides thereof. Further, the receiving laser head 22 may be arranged in a planar shape or a circumferential shape with the transmitting laser head 21 as the center.

The support member 11 coupled to the space moving unit 12 is connected to the probe 20 via the angle adjusting unit 13 and brings the probe 20 close to an arbitrary position on the surface of the inspection target K. Then, the probe 20 is scanned along the surface of the inspection object K in a state where the distance from the surface of the inspection object K is kept constant.
Here, the space moving unit 12 may take various specific modes, but a moving means (not shown) that displaces the range on the surface of the inspection target K one-dimensionally or two-dimensionally, and this moving means. And a lifting / lowering means for displacing the support member 11 toward the surface of the inspection object K. Alternatively, an articulated robot (not shown) whose tip forms the support member 11 can be applied.

As shown in FIG. 1 (B), the angle adjustment unit 13 includes a first adjustment body 13a that performs a predetermined angle on the probe 20 around the first rotation shaft 15a, and the first rotation shaft 15a. The second adjustment body 13b is configured to provide a predetermined angle to the first adjustment body 13a with the second rotation shaft 15b orthogonal to the center.
The angle adjusting unit 13 is provided with a driving body (not shown) for making an angle around the first rotation shaft 15a and the second rotation shaft 15b.

Thus, the angle adjusting unit 13 can set the inclined surface of the probe 20 in an arbitrary direction and an arbitrary inclination by biaxial adjustment of the first rotating shaft 15a and the second rotating shaft 15b.
Thereby, the angle of the probe 20 can be adjusted, and the laser light emitted from the transmission laser head 21 and the reception laser head 22 can be incident on the surface of the inspection target K in the normal direction.

As shown in FIG. 2, the transmission laser head 21 is connected to a transmission laser source 23 via an optical fiber or the like.
The transmission laser source 23 outputs, for example, a CO ₂ laser having a wavelength of 10.6 μm as the first laser R1. As irradiation conditions of the first laser R1, for example, the pulse width is set to 50 ns to 200 ns, the energy is set to 100 mJ to 200 mJ, and the repetition frequency is set to 50 Hz to 150 Hz.
According to the first laser R1 irradiated under such conditions, the penetration depth is about 20 μm with respect to the inspection target K of the carbon fiber composite material.

  When the inspection target K is irradiated with the first laser R1, a very small area on the surface is instantaneously heated to turn several surface layers into plasma, and ultrasonic waves are applied to the inspection target K as a reaction force when the generated plasma expands. Is excited. The ultrasonic waves are divided into those that propagate inside the subject and those that propagate on the surface of the subject.

As shown in FIG. 2, the reception laser head 22 is connected to a reception laser source 24 via an optical fiber or the like.
The receiving laser source 24 outputs, for example, a YAG laser having a wavelength of 1064 nm as the second laser R2.
The laser method applied to the transmission laser source 23 or the reception laser source 24 is not particularly limited, and various laser methods can be applied.

The ultrasonic wave excited by the first laser R1 is reflected on the back surface or the defective portion of the inspection target K, and the surface of the inspection target K where the reflected wave (echo) arrives vibrates with a displacement of nanometer order.
When the second laser R2 is irradiated on the surface of the inspection target K that is minutely oscillated by this echo, reflected light having a wavelength changed due to optical frequency transition (Doppler shift) is reflected.

As shown in FIG. 2, the signal processing unit 30 receives the reflected light of the second laser R2 and measures the Doppler shift, and converts the analog signal acquired from the reception interferometer 25 into a digital signal. The signal recording unit 26 for collecting data and an imager 27 for performing image processing by aperture synthesis processing based on the integrated data.
Then, a signal is output from the signal processing unit 30 to the monitor 33, and the defect position included in the inspection target K is image-recognized.

By the way, the operation control of the space moving unit 12 and the angle adjusting unit 13 is performed based on the surface shape information of the inspection target K registered in the information storage unit 34 in advance.
On the other hand, in order to realize further high accuracy of defect detection, the information of the signal processing unit 30 is fed back to the control unit 32, whereby the space moving unit 12 and the angle adjusting unit 13 can be adjusted.

Specifically, the space moving unit 12 and the angle adjusting unit 13 can be adjusted based on the intensity signal of the reflected light of the second laser R2 measured by the reception interferometer 25.
Alternatively, the space moving unit 12 and the angle adjusting unit 13 can be adjusted based on the detection timing and intensity of the surface wave signal included in the reflected light of the second laser R2 measured by the reception interferometer 25.

FIG. 3 shows the signal level S1 of the received surface wave data and the signal level S2 of other measurement data overwritten. Thus, the space moving unit 12 and the angle adjusting unit 13 can be adjusted by comparing the two signal levels S1 and S2.
Further, based on the position information of the space moving unit 12 or the angle information of the angle adjusting unit 13, the intensity of the detected echo can be corrected, and a high quality image can be obtained.

Next, the operation of the laser ultrasonic inspection apparatus 10 will be described.
First, based on the surface shape information of the inspection target K registered in the information storage unit 34, the space moving unit 12 and the angle adjustment unit 13 are operated, and the probe 20 is moved to a predetermined position and angle with respect to the surface of the inspection target K. Make them close by.

Then, when the irradiation spot size of the first laser R1 and the second laser R2 is 2 mm × 10 mm, for example, the space moving unit 12 is spaced from the surface of the investigation target K as 50% overlap of the beam scan. The probe 20 is moved stepwise at intervals of 1 mm in the short side direction of the irradiation spot in a state where is kept constant.
As the probe 20 moves stepwise along the surface of the survey target K in this way, the angle adjustment unit 13 operates based on the surface shape information, and the first laser R1 and the second laser R2 are moved to the surface of the survey target K. Incident in the normal direction.

  The first laser R1 transmitted from the transmission laser source 23 via the optical fiber is irradiated from the transmission laser head 21 toward the investigation target K. Then, the ultrasonic wave propagating through the surface and inside of the investigation target K is excited with the irradiation spot of the first laser R1 as a starting point.

  On the other hand, the second laser R2 transmitted from the reception laser source 24 through the optical fiber is irradiated from the reception laser head 22 toward the investigation target K. Then, the reflected light of the second laser R 2 that reflects the surface of the investigation object K is transmitted to the reception interferometer 25 through the optical fiber in the reverse direction.

At this time, when the echo of the ultrasonic wave excited by the first laser R1 reaches the irradiation spot of the second laser R2, the reflected light of the second laser R2 undergoes a wavelength change due to Doppler shift.
The reception interferometer 25 detects the signal of the wavelength change due to the Doppler shift, the signal recorder 26 converts the detected analog signal into a digital signal and stores it, and the imager 27 stores the stored data as an image. The data is converted into data, and the monitor 33 displays an internal image of the inspection object K including the defect.

The signal processing unit 30 also measures the intensity of the reflected light of the second laser output from the reception interferometer 25. The angle adjustment unit 13 is readjusted by feeding back the measured intensity information of the reflected light. To do.
In addition, the signal processing unit 30 corrects the intensity of the echo detected based on the angle information of the angle adjusting unit 13, and performs image quality improvement processing in the imager 27.

  With the laser ultrasonic inspection apparatus 10 described above, the non-destructive inspection of the inspection target K having a complicated surface shape can be performed at high speed and with high accuracy.

(Second Embodiment)
As shown in FIG. 4, the laser ultrasonic inspection apparatus of the second embodiment is provided with a surface measurement head 28 and a surface measurement unit 29 instead of the information storage unit 34 (FIG. 2) in the first embodiment. ing. 4 that are the same as or correspond to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

The surface measuring unit 29 measures the surface shape of the inspection target K by the surface measuring head 28 installed on the probe 20 and generates operation signals of the space moving unit 12 and the angle adjusting unit 13 based on the measurement result. It is. Thereby, the defect inspection of the inspection object K can be performed without creating the surface shape information of the inspection object K in advance.
Examples of the surface measuring head 28 include those that irradiate the surface of the inspection target K with laser light R3 for measuring the surface shape, as shown in FIG. 4, but are not limited thereto. Instead, for example, an ultrasonic type or contact type distance sensor can be used.

(Third embodiment)
As shown in FIG. 5, the angle adjustment unit 13 in the laser ultrasonic inspection apparatus of the third embodiment individually adjusts the angles of the transmission laser head 21 and the reception laser head 22.
5 that are the same as or correspond to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

The laser ultrasonic inspection apparatus of the third embodiment is the same as the first embodiment in that the probe 20 is brought close to the surface of the inspection object K by the space moving unit 12 (FIG. 1).
The transmitting laser head 21 and the receiving laser head 22 are connected to the individual position adjusting units 16 so that the positions can be adjusted separately.
Furthermore, the transmission laser head 21 and the reception laser head 22 are connected to individual angle adjustment units 13 so that the inclination can be adjusted separately.

  When the cylindrical member shown in FIG. 5 is targeted as the inspection target K, the angle adjustment unit 13 is adjusted by one rotation axis 15 to adjust the inclination of the transmission laser head 21 and the reception laser head 22. Can do. On the other hand, in the case of the inspection target K having a complicated surface shape, it is necessary to adjust the inclination of the transmission laser head 21 and the reception laser head 22 by adjusting the angle adjustment unit 13c biaxially.

FIG. 6A is a side view of the laser ultrasonic inspection apparatus on which the crosstalk preventing wall 17 is mounted in the first embodiment. FIG. 6B is a side view of a laser ultrasonic inspection apparatus equipped with a crosstalk prevention wall 17 in the third embodiment.
Thus, by providing the crosstalk prevention wall 17, it is possible to prevent the reflected light of the first laser R1 or the second laser R2 from interfering with the adjacent transmission laser head 21 or reception laser head 22.
Thereby, the nondestructive inspection of the inspection target K having a complicated surface shape can be performed with high accuracy.

(Fourth embodiment)
As shown in FIG. 7, in the laser ultrasonic inspection apparatus of the fourth embodiment, a plurality of probes 20 each having a transmission laser head 21, a reception laser head 22, and an angle adjustment unit 13 are arranged on the inspection target.
Thereby, the nondestructive inspection of the inspection target K having a complicated surface shape can be performed at high speed.

The present invention is not limited to the above-described embodiments, and can be appropriately modified and implemented within the scope of the common technical idea.
For example, the case where the second laser R2 is irradiated with a plurality of beams is shown, but the case where it is a single beam is also included. The angle adjustment unit 13 forms an inclined surface having an arbitrary direction and an arbitrary inclination by biaxial adjustment. However, depending on the shape of the inspection target, the inclination adjustment by uniaxial adjustment may be sufficient.

  In addition, the angle adjustment unit 13 forms an inclined surface with an arbitrary direction and an arbitrary inclination by the first rotation shaft 15a and the second rotation shaft 15b, but is not limited to this method, for example, Various actuators may be combined and connected to the probe to change the inclined surface.

  DESCRIPTION OF SYMBOLS 10 ... Laser ultrasonic inspection apparatus, 11 ... Support member, 12 ... Spatial movement part, 13 ... Angle adjustment part, 13a ... 1st adjustment body, 13b ... 2nd adjustment body, 15 ... Turning axis, 15a ... 1st time Moving shaft, 15b ... second rotating shaft, 16 ... position adjusting unit, 17 ... crosstalk prevention wall, 20 ... probe, 21 ... transmitting laser head, 22 ... receiving laser head, 23 ... transmitting laser source, 24 ... receiving laser Source 25, reception interferometer 26, signal recorder 27, imager 28, surface measurement head 29, surface measurement unit 30, signal processing unit 31, operation terminal 32, control unit 33, Monitor, 34... Information storage unit, K... Inspection object, R1... First laser, R2... Second laser, R3.

Claims (12)

A transmission laser head that irradiates an inspection target with a first laser to excite ultrasonic waves;
A receiving laser head that detects an echo of the ultrasonic wave that propagates through the inspection object by irradiating a second laser;
A signal processing unit for imaging a defect included in the inspection object based on the detected echo;
An laser ultrasonic inspection apparatus comprising: an angle adjustment unit that adjusts incident angles of the first laser and the second laser with respect to a surface of the inspection target. The laser ultrasonic inspection apparatus according to claim 1,
A laser ultrasonic inspection apparatus comprising a plurality of the receiving laser heads. In the laser ultrasonic inspection apparatus according to claim 1 or 2,
The laser ultrasonic inspection apparatus, wherein the angle adjustment unit includes a mechanism for adjusting an angle of a probe that holds the transmission laser head and the reception laser head. In the laser ultrasonic inspection apparatus according to any one of claims 1 to 3,
The angle adjustment unit is configured to be capable of individually adjusting the angles of the transmission laser head and the reception laser head, respectively. In the laser ultrasonic inspection apparatus according to any one of claims 1 to 4,
A laser ultrasonic inspection apparatus comprising: a surface measurement unit that measures a surface shape of the inspection target, wherein the angle adjustment unit is driven based on a measurement result of the surface measurement unit. In the laser ultrasonic inspection apparatus according to any one of claims 1 to 5,
The laser ultrasonic inspection apparatus, wherein the angle adjusting unit is driven based on the intensity of reflected light of the second laser. In the laser ultrasonic inspection apparatus according to any one of claims 1 to 6,
The laser ultrasonic inspection apparatus, wherein the angle adjustment unit is driven based on at least one of detection timing and intensity of a surface wave signal included in reflected light of the second laser. In the laser ultrasonic inspection apparatus according to any one of claims 1 to 7,
A laser ultrasonic inspection apparatus that performs intensity correction of the echo based on angle information of the angle adjustment unit. The laser ultrasonic inspection apparatus according to any one of claims 1 to 8,
A laser ultrasonic inspection apparatus comprising a head position adjustment mechanism capable of individually adjusting the distances between the transmission laser head and the reception laser head and the inspection object. In the laser ultrasonic inspection apparatus according to any one of claims 1 to 9,
A laser ultrasonic inspection apparatus comprising a crosstalk prevention wall for preventing interference between adjacent transmission laser heads and reception laser heads. In the laser ultrasonic inspection apparatus according to any one of claims 1 to 10,
A laser ultrasonic inspection apparatus, wherein a plurality of probes each including the transmission laser head, the reception laser head, and an angle adjustment unit are arranged on the inspection target. Irradiating an inspection target with a first laser to excite ultrasonic waves;
Irradiating a second laser to detect an echo of the ultrasonic wave propagating through the inspection object;
Performing signal processing for imaging a defect included in the inspection object based on the detected echo;
Adjusting the incident angles of the first laser and the second laser with respect to the surface to be inspected.

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