KR101312321B1 - Nondestructive crack detecting apparatus for a nuclear fuel plate - Google Patents

Abstract

According to an aspect of the present invention, there is provided a test apparatus for extracting internal defect information of a plate fuel specimen, comprising: a heating unit for heating an object, a beam irradiation unit for irradiating a plurality of beams, and an information collecting unit, wherein the information collecting unit is irradiated to the specimen. Provided is a non-contact non-destructive inspection apparatus that extracts interference between a plurality of beams and obtains defect information of the specimen.
In addition, the present invention is a test device for extracting the internal defect information of the plate-shaped fuel specimen, the heating unit for heating the object, the beam irradiation unit formed to irradiate the beam to the object and the horizontal direction of the specimen with respect to the front and back of the measurement specimen The present invention provides a non-contact non-destructive inspection apparatus including an information collecting unit capable of extracting gradient defect information inside a measurement specimen by obtaining a gradient displacement image and a gradient phase image.

Description

Plate fuel non-destructive testing device {NONDESTRUCTIVE CRACK DETECTING APPARATUS FOR A NUCLEAR FUEL PLATE}

The present invention relates to a non-contact, non-destructive inspection device for detecting defects in the plate fuel specimen.

Defects in the plate fuel can be detected by X-ray or ultrasound. In the case of X-ray inspection, large defects can be effectively detected, but in the case of small delamination defects or close defects, which are major defects of the plate-shaped fuel, it is difficult to detect them.

The defect detection method using the high frequency ultrasonic wave has the advantage of being able to detect the peeling and the defect of the joint effectively. However, in the case of ultrasonic examination, scanning inspection is required, so it takes a lot of time to examine all the area of the specimen and because the thickness of the plate-shaped fuel is very thin, about 2 mm, it is necessary to use high frequency ultrasonic wave of several tens of MHz. There is a disadvantage that must be performed.

In the conventional defect detection method using laser ultrasound, the presence, type, size, and location of the defect are determined by measuring the delay time, the signal strength, and the signal shape of the ultrasonic signal without converting the signal ( 10-2001-0026773), the ultrasound is converted to a digital signal and then imaged to measure the defect (Republic of Korea Patent Publication 10-2005-0046083). Such conventional technologies have a problem that the method of use is complicated for the general public in the industrial field and it is difficult to provide image information at high speed.

The present invention is to provide a non-contact non-destructive defect image measuring apparatus for showing a defect image in a nuclear fuel specimen using a plurality of beams.

In addition, the present invention is to provide a non-contact non-destructive defect image measuring apparatus for measuring the defect image in the nuclear fuel specimen by extracting the slope defect information using the beam.

In order to solve the above problems, a non-contact non-destructive defect image measuring apparatus according to an embodiment of the present invention, a heating unit for heating the object to expand or contract the crack existing in the object at regular intervals, and the A reference path proceeding in a direction away from one surface vertically, a first path reflected after being incident at a predetermined angle on the surface, and a second path beam reflected after being incident on the surface at an angle different from the first path; And a beam irradiator for overlapping the beams to form an interference image, and an information collector for extracting defect information of the object from the interference image. The beam irradiator generates a first directional interference image of the surface of the object by overlapping the beam of the first path and the beam of the second path, and overlaps the beam of the first path and the beam of the reference path to overlap the beam on the object surface. An interference image in a second direction intersecting with one direction is generated.

As an example related to the present invention, the beam irradiator includes a beam generator for irradiating a beam and a beam splitter formed in a path of the beam so that the beam travels in at least two different paths.

As an example related to the present invention, the beam irradiator includes a phase shifting device which is formed in at least one path to change the phase of the beam passing through the path.

As an example related to the present invention, the heating unit may be disposed in a continuous oscillation laser apparatus for heating the object and a traveling path of a laser generated by the continuous oscillation laser apparatus, and may transmit the laser at a sine wave intensity over time. It includes a filter that is controlled to be.

 As an example related to the present disclosure, the heating unit may include a heat source device capable of heating the object to a strength in the form of one sinusoidal wave or an intensity overlapping at least two sinusoids.

As an example related to the present invention, the information collecting unit acquires and stores in real time a horizontal interference image and a vertical interference image generated on one surface of the object, and stores a horizontal phase map image for each time from the horizontal interference image. And a signal processing module for obtaining a time-dependent vertical phase map image from the vertical interference image.

In order to solve the above problems, the non-contact non-destructive defect measurement apparatus according to an embodiment of the present invention, the heating unit for heating the object to expand or contract the crack existing in the object at a predetermined period, and the object A beam irradiator for generating an interference image by irradiating a laser beam, dividing a beam reflected from the object surface, and then superposing the laser beam; and an information collecting unit for measuring any one-way displacement of the object surface by heating from the interference image. do. The beam irradiator divides the beam reflected by the object into a first path and a second path, and a first mirror and a plane perpendicular to the second path and the second path to rereflect the beam of the first path. And a second mirror tilted at an angle and reflecting the beam passing through the second path to overlap the beam of the first path to generate a tilted interference image.

As an example related to the present invention, the heating unit may be disposed in a continuous oscillation laser apparatus for heating the object and a traveling path of a laser generated by the continuous oscillation laser apparatus, and may transmit the laser at a sine wave intensity over time. It includes a filter that is controlled to be.

As an example related to the present invention, the beam irradiator includes a phase shifting device which is formed in at least one path to change the phase of the beam passing through the path.

As an example related to the present disclosure, the heating unit may include a heat source device capable of heating the object to a strength in the form of one sinusoidal wave or an intensity overlapping at least two sinusoids.

As an example related to the present invention, the information collecting unit includes a storage module for acquiring and storing a gradient interference image generated from one surface of the object in real time and a signal processing module for obtaining a gradient phase map image for each hour from the interference image. do.

In order to solve the above problems, the method for measuring a non-contact nondestructive defect image measuring apparatus according to an embodiment of the present invention, the heating unit heating the object to a certain period of intensity, the beam irradiation unit and the front and Generating an interference image for each surface by irradiating a laser on the back surface, and obtaining information from the interference image of the front surface by time information collecting unit for the phased phase image of the front surface from the interference image on the back surface; Obtaining a time-phased phase map image on the back side, and generating the displacement image and the phase image on the front side by extracting an amplitude value and a phase value at a specific frequency from the phase map image on the front side; The collector extracts an amplitude value and a phase value at a specific frequency from the phase map image on the back side. Generating a displacement image and a phase image of the data acquisition unit, acquiring the relative displacement image information of the front and back sides of the object using the difference between the displacement image of the front surface and the displacement image of the back surface; Obtaining relative phase image information of the front and back sides of the object by using a difference between the phase image of the front side and the phase image of the back side.

As an example related to the present invention, the heating unit heats the object in the form of a sine wave, and the specific frequency includes a frequency corresponding to a heating period in which the heating unit heats the object and an integer multiple of the frequency.

As an example related to the present invention, the heating unit heats the object with an intensity in the form of overlapping two or more sinusoidal waves, and the specific frequency corresponds to a frequency corresponding to a period of each sinusoidal wave, a sum or a difference of the frequencies. Includes an overlapping frequency and an integer multiple of the frequency.

The non-contact non-destructive inspection apparatus according to at least one embodiment of the present invention configured as described above may obtain a phase image and a displacement image in a vertical or horizontal direction by extracting an interference signal between a plurality of beams. Through this, it is possible to effectively provide defect information existing in the plate fuel.

In addition, the present invention can obtain a tilt phase image and a displacement image in the vertical or horizontal direction with respect to the plate-like fuel surface. Since the slope information has a strong characteristic against noise, it can be effectively used in industrial sites.

1 is a diagram illustrating an internal configuration of a non-destructive inspection device based on a laser interferometer for thermal deformation measurement for detecting internal defect image information of a plate-shaped fuel specimen according to an embodiment of the present invention.
2 is a diagram illustrating an internal configuration of a heating apparatus based on a heating apparatus according to an embodiment of the present invention.
3 is a view showing the internal configuration of a laser-based heating unit according to an embodiment of the present invention.
4 is a view showing the transmittance of each rotation angle of the rotary variable strength filter according to an embodiment of the present invention.
FIG. 5 is a view illustrating heating intensity for each 10 second period of a heating unit according to an embodiment of the present invention. FIG.
FIG. 6 is a view illustrating heating intensity for each 100 second period of a heating unit according to an embodiment of the present invention. FIG.
FIG. 7 is a view illustrating heating intensity of a 10 second cycle and a 100 second cycle of a heating unit according to an embodiment of the present invention.
FIG. 8A is a diagram illustrating an image of acquiring and storing N laser interference images continuously in a timely manner in a laser interference unit according to an embodiment of the present invention.
FIG. 8B is a diagram illustrating four laser beam phases (for example, 0 degrees, 90 degrees, 180 degrees, 270 degrees, etc.) at each time point when an image is acquired by using a phase shifting device in an interference part according to an embodiment of the present invention. FIG. 11 is a diagram illustrating an image of acquiring and storing N * 4 laser interference images in succession.
9 is a diagram illustrating a position of a frequency domain for extracting defect information in a defect image information collecting unit according to an embodiment of the present invention.
10 is a diagram illustrating a position of a periodic multiple frequency region for extracting defect information from a defect image information collecting unit according to an embodiment of the present invention.
11 is a signal processing flowchart of a non-contact non-destructive inspection device for detecting defect image information from a laser interference image according to an embodiment of the present invention.
12 is a signal processing flowchart of a non-contact non-destructive inspection device for detecting defect image information from a phase shift laser interference image according to an embodiment of the present invention.
FIG. 13 is a diagram illustrating a configuration of an apparatus for inspecting an internal defect of an object using a high frequency ultrasonic signal of a general piezoelectric trend method.
14 is a diagram illustrating an internal configuration of a non-destructive inspection device based on a tilt laser interferometer for measuring thermal deformation for detecting tilt image information of an internal defect of a plate-shaped fuel specimen according to an embodiment of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, the plate-shaped fuel non-contact nondestructive inspection apparatus which concerns on this invention is demonstrated in detail with reference to drawings. In the present specification, the same or similar reference numerals are given to different embodiments in the same or similar configurations. As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

The suffix "module" and " part "for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role.

1 is a diagram illustrating an internal configuration of a non-destructive inspection device based on a laser interferometer for thermal deformation measurement for detecting internal defect image information of a plate-shaped fuel specimen according to an embodiment of the present invention.

Referring to FIG. 1, a non-contact non-destructive inspection apparatus according to an embodiment of the present invention may include a beam irradiator, a heating unit, an information collecting unit, and the like.

The heating part may be heated without contacting the measurement object 14.

The beam irradiator may be an electronic speckle laser interference part 3 (4) that obtains a laser interference image having displacement information that is changed in a horizontal direction and a vertical direction of the surface direction of the object 14 by heat.

The information collecting unit may be configured to extract defect information from the laser interference image obtained from the beam irradiator.

The laser interference image of the front surface of the measurement object may be measured by the electronic speckle laser interference part 4 located at the front side, and the laser interference image of the back surface may be measured by the electronic speckle laser interference part 3 located at the back side. .

The upper heating part 1 generates heat by the control device 11 controlled by the defect image information collecting part 5 controlling the heat source device 12, and the generated heat is measured by the heat spreader 13. The front of the object 14 is evenly irradiated. In addition, the lower heating unit 2 generates heat by the control device 15 controlled by the defect image information collecting unit 5 controls the heat source device 16 and the generated heat is measured by the heat spreader 17. The front of the object 14 is evenly irradiated. In this case, heat may be applied to the surface of the measurement object in the form of a sine wave having a predetermined period.

Due to the heat irradiated to the measurement object, micro-deformation is generated at each position in the measurement object, and the deformation appears in the form of displacement on the surface of the measurement object. This displacement is measured by the laser interference part 4 of the front face of the specimen and the laser interference part 3 of the back face.

The laser interference part 3 located behind the measurement object generates an interference image by using the output beam of the laser 21. The output laser beam of the laser 21 is divided into a passing beam and a reflected beam by the beam splitter 22. The passing beam is further divided into a passing beam and a reflected beam by another beam splitter 23. The beam passing through the beam splitter 23 is reflected by the mirror 24, and then adjusted by the filter 48, and then through the beam splitter 25, through the imaging lens 27, and the imaging sensor 28. Is incident on. The beam reflected by the beam splitter 23 passes through the mirrors 47 and 30, and then irradiates the back side of the measurement object 14 by the beam diffusing optical system 31, and then the image is passed through the beam splitter 25 to the imaging lens. A laser interference image incident on the image pickup sensor 28 via 27 and displaced in the vertical direction of the surface of the measurement object 14 is obtained by the image pickup sensor 28. In this case, the laser beam reflected by the beam splitter 23 may be phase shifted by the phase shifter. According to an embodiment of the present invention, the phase shifting device may be a PZT 29. The beam may be phase shifted by the PZT 29 so that the imaging sensor may acquire a laser interference image shifted in phase.

The beam splitter 25 can be removed from the optical path of the beam which has been rotated by the rotating device 26 and passed through the beam splitter 23, in which case the laser beam passes through the mirror 32 and the beam diffusing optical system 33. The laser interference image containing the displacement information which is uniformly irradiated on the back of the measurement object and is horizontally deformed on the surface through the imaging lens 27 is obtained by the imaging sensor 28. At this time, the angles of the beams of the two paths irradiated from above and below the measurement object are between 45 and 180 degrees.

The laser interference image is obtained in the same manner on the front surface of the measurement object.

The laser interference part 4 located in front of the measurement object generates an interference image of the front surface by using the output beam of the laser 21. The laser beam reflected by the beam splitter 22 is split into a passing beam and a reflected beam by another beam splitter 36 past the mirror 35. The reflected beam is intensity-adjusted by the filter 49 and then enters the imaging sensor 40 through the beam splitter 37 and through the imaging lens 39.

The beam passing through the beam splitter 36 passes through the mirrors 41 and 42 and passes through the beam diffusing optical system 44 evenly on the front surface of the measurement object, and the image of the front side of the irradiated measurement object is connected to the beam splitter 37. An image is formed on the imaging sensor 40 via the imaging lens 39. At this time, the image pickup sensor 40 forms a vertical laser interference image on the front surface of the measurement object 14.

The beam splitter 37 located in front of the object may be removed from the optical path of the beam which has been rotated by the rotating device 38 and passed through the beam splitter 36, in which case the laser beam is mirror 45 and beam diffusing. A laser interference image containing displacement information that is uniformly irradiated on the front surface of the measurement object through the optical system 46 and is deformed in the horizontal direction on the surface is obtained by the imaging sensor 40 through the imaging lens 39.

The defect image information collecting unit 5 can obtain distortion information from the laser interference image obtained by including a control and signal processing computer therein.

2 is a diagram illustrating an internal configuration of a heating apparatus based on a heating apparatus according to an embodiment of the present invention.

The heat source device of the heating unit may be a heat exchanger. The heat intensity of the heat exchanger 12-1 is controlled by the controller 1.

3 is a view showing the internal configuration of a laser-based heating unit according to an embodiment of the present invention.

Referring to FIG. 3, the rotary continuous variable intensity filter 12-3 continuously controls the intensity of the laser beam output from the continuous oscillation laser 12-2. By the filter the intensity of the laser beam is varied in the form of sinusoidal amplitude. The permeability of the rotary continuous variable strength filter 12-3 is shown in FIG. 4.

The intensity of heat that heats the surface of the measurement object may be in the form of a sine wave. The heating unit may heat the object to an intensity of one sinusoidal wave form or an intensity of a form in which at least two sinusoids are superposed. For example, it may be heated in one cycle as shown in FIG. 5, and may be heated in a cycle as shown in FIG. 7 by overlapping the period in FIG. 5 and the period in FIG. 6.

For example, when FIG. 5 is a 10-second heating cycle and FIG. 6 is a 100-second heating cycle, the heating intensity pattern irradiated with the same may be the same as FIG. 7.

The process of obtaining the time-phased phase map image by the information collector is as follows.

The information collector acquires a horizontal laser interference image (image size: mxn pixels) and a vertical interference image (image size: mxn pixels) generated in front of and behind a measurement object in real time, and stores the result in a computer memory. Obtain the horizontal fringe image and the wrapping phase map by time from the horizontal laser interference image, and then unwrapp the expanded phase map image, and use the same method to wrap the vertical fringe image and the time-dependent vertical fringe image with the vertical laser interference image. The phase map is obtained and then unwrapped to obtain a phase map image. The method of obtaining the lapping phase map and the unwrapping phase map will be described in more detail using Equation (4) and Equation (9) below.

The horizontal phase map contains defect information that changes in the horizontal direction on the object surface, and the vertical phase map contains defect information that changes in the vertical direction on the object surface.

The phase map information for the defect can be obtained by subtracting the reference phase map from the unfolded current phase map.

In addition, the process of collecting the vertical and horizontal displacement image of the information collector is as follows.

From the horizontal phase map image (image size: mxn pixels) obtained in real time, the value is extracted at time (1,1) position by time to generate a one-dimensional signal in the time domain, and the frequency is converted by frequency conversion. After extracting the amplitude coefficient value at a specific frequency position, record it at the position (1,1) of the horizontal displacement image and repeat the process from (1,2) pixel position of the horizontal phase map image (m, n) A horizontal displacement image (size: mxn pixel) is generated by repeating up to the position. From the vertical phase map image (image size: mxn pixels) obtained in real time, the value is extracted at time (1,1) position by time to generate a one-dimensional signal in the time domain, and frequency transformed to generate a frequency spectrum. After extracting the amplitude coefficient value at a specific frequency position, we record it at (1,1) position of the vertical displacement image and repeat this process from (1,2) pixel position of the vertical phase map image (m, n) A vertical displacement image (size: mxn pixel) may be generated by repeating up to the position.

The specific frequency position extracted by the information collecting unit may be the same frequency as the single periodic frequency when the heating unit heats the single frequency period. The specific frequency position may also be a frequency position that is a multiple of the single periodic frequency.

If the heating unit heats the object with the intensity of overlapping at least two sine waves, the specific frequency position extracted by the defect image information collecting unit is equal to the plurality of periodic frequencies, the sum or difference of the periodic frequencies that the heating unit heats up. It may be a corresponding frequency.

The principle of extracting the relative vertical defect information and the relative horizontal defect information of the front side from the displacement image of the front and back sides of the object is as follows.

The information collector obtains a horizontal displacement image of the back and front of the measurement specimen, and obtains a difference image of the horizontal displacement image of the front surface of the measurement specimen from the horizontal displacement image of the back of the measurement specimen. Extract the information. In the same way, the vertical phase image is obtained for the back and front surfaces of the test specimen, and the vertical deflection image for the front surface of the test specimen is obtained from the vertical displacement image obtained for the back surface of the measurement specimen. Can be extracted.

The principle of collecting the vertical or horizontal phase image of the information collector is as follows.

The information collector generates a 1-dimensional signal in the time domain by extracting a value at a time (1,1) position from time to time in a horizontal phase map image (image size: mxn pixels) obtained for each time obtained in real time, and converting the frequency into a frequency domain. After obtaining the frequency spectrum, extract the phase value at the specific frequency position and record it in the (1,1) position of the horizontal phase image. A horizontal phase image (size: mxn pixels) is generated by repeating up to position (m, n), and a time-phased vertical phase map image (image size: mxn pixels) is obtained at the time (1,1) position at time. The value is extracted to generate a one-dimensional signal in the time domain, and the frequency is transformed to obtain a frequency spectrum. Value, and this process may be repeated from (1,2) pixel position to (m, n) position of the vertical phase map image to generate a vertical phase image (size: mxn pixel).

The principle of extracting the relative vertical defect information and the relative horizontal defect information from the phase image of the front and back of the object is as follows.

The information collector obtains a horizontal phase image of the back and front surfaces of the test specimen, and obtains a difference image of the horizontal phase image obtained from the horizontal phase image of the front surface of the measurement specimen, Extract defect information. In the same way, a vertical phase image is obtained for the back and front surfaces of the test specimen, and a vertical phase image obtained for the front surface of the test specimen is obtained from the vertical phase image obtained for the back surface of the measurement specimen. Information can be extracted.

The detailed process of extracting the defect image by the information collector is as follows.

The defect image information collecting unit 5 of FIG. 1 can obtain deformation information from the laser interference image obtained by including a control and signal processing computer therein. The defect image information collecting unit 5 acquires a laser interference image of the back side of the measurement object by using the laser interference unit 3, and obtains a laser interference image of the front side of the measurement object by using the laser interference unit 4. . The defect image information collecting unit 5 first stores the reference laser interference image before heating the measurement object, and then starts to acquire the laser interference images of the front and rear surfaces of the measurement object while starting the heating. The laser interference image is continuously measured in real time, and the defect image information collecting unit 5 sequentially stores the measured laser interference image in a memory in an internal control and signal processing computer. For example, the result of storing N laser interference images in real time in the time domain and storing them in a memory is shown in FIG. 8A. In this case, the measurement object is heated at a sine type heat intensity which is repeated at regular intervals. The obtained laser interference image may be stored in real time without phase shift or may be acquired using a phase shifter. The phase shifter may be PZTs 29 and 42 of FIG. 1. For example, in FIG. 8A, the image of No. 1 is a speckle laser interference image, which is a laser interference image that does not phase shift, and the number 1 of FIG. Four laser interfering images, respectively, obtained after moving to °, 90 °, 180 °, and 270 °) are acquired and stored in memory.

In addition, the laser interference image may obtain a laser interference image containing displacement information in a direction perpendicular to the surface of the measurement object by leaving the beam splitters 25 and 37 on the optical path as it is, and using the rotating devices 26 and 38. The beam splitters 25 and 37 may be removed from the optical path to obtain and store a laser interference image including displacement information that is deformed in the horizontal direction of the measurement object.

The laser interference image f (x, y) in the time domain may be expressed as Equation (1).

(1)

(One)

Where d is the direct current component of the image, b is the brightness intensity for each (x, y) position, and Φ is the phase component to be measured.

If this is converted into the frequency domain, it is expressed as Equation (2) below.

(2)

(2)

Where D is a direct current component in the frequency domain, F is a frequency domain representation of the signal, and ^* represents a complex conjugated component. If only one of the F (w _x , w _y ) signals or F ^* (w _x , w _y ) is selected and the inverse frequency conversion is performed, the following equation (3) is obtained.

은 식(4)로부터 획득할 수 있다.Then from Eq. (3) we get

Can be obtained from equation (4).

는 위상펼침(참조: "2D phase unwrapping", D.C.Ghiglia and M.D. Pritt,, A Willey-Interscience Publication, 1998)을 실행하여 위상맵 영상을 획득한다. Wrapping phase map image

Performs phase unfolding (see "2D phase unwrapping", DCGhiglia and MD Pritt, A Willey-Interscience Publication, 1998) to obtain a phase map image.

If the laser interference image is acquired by the phase shift method, four phase shifted (0 °, 90 °, 180 °, 270 °) interference images are obtained at any one time, so that the equations (5), (6), It can be expressed as (7), (8).

Where d is the direct current component of the image, I _ac is the brightness intensity for each (x, y) position, and φ is the phase component to be measured. The lapping phase map image obtained from these is obtained as shown in equation (9).

In the same way, the wrapping phasemap image Φ (x, y) is subjected to phase unfolding (see “2D phase unwrapping” DC Ghiglia and MD Pritt, A Willey-Interscience Publication, 1998) to obtain a displacement phasemap image. .

The defect phase image can be obtained by subtracting the current displacement phase map image from the reference displacement phase map image.

라고 하면

에서의 진폭을 구하면 되고, 복수의 주기인

와

이라고 가정을 하면 도 9에 보이는 바와 같이

에서의 계수값을 구하여

에서의 변위영상을 구할 수 있으며,에서의 계수값을 구하여

에서의 변위영상을 구할 수 있으며,

에서의 계수값을 구하여

에서의 변위영상을 구할 수 있으며,

에서의 계수값을 구하여

에서의 변위영상을 구할 수 있다. 또한 판형핵연료 내부에 Closed 결함 혹은 미세결함이 있으면 재료는 변형과정에서 가열부에서 가열하는 주기의 배수에 해당하는 주파수 성분이 발생하는 비선형 성분이 발생하므로 이를 이용하여 비선형 변위 영상을 얻을 수 있다. 예를들어, 도 10에 보이는 바와 같이 측정 대상체 표면에 가하는 가열부의 정현 주기가

Hz라고 가정을 하면,

혹은

에서의 상대적인 계수 변화를 구하여 비선형 변위 영상을 얻을 수 있다. In the phase map image obtained in the time domain, a signal of each pixel position for each time can be obtained. For example, assuming that the figure showing the phase map image obtained for each time is shown in FIG. 8, P (pixel, 1, 1) position P ( The time domain signal at x1, y1) will be a value represented along the point. After frequency conversion of this value, the amplitude value at f [Hz], which is the thermal intensity period applied by the heating unit, is extracted and collected ((pixel, m, n) at pixel (1, 1)). A displacement image of an mxn size, which is a measurement object displacement image, may be obtained. For example, the period of heating

When you say

Is to find the amplitude of

Wow

Assume that as shown in Figure 9

Find the coefficient at

You can get the displacement image at, Find the coefficient at

You can get the displacement image at,

Find the coefficient at

You can get the displacement image at,

Find the coefficient at

The displacement image at can be obtained. In addition, if there is a closed defect or microdefect inside the plate fuel, the material generates a nonlinear component that generates a frequency component corresponding to a multiple of the period of heating in the heating part during the deformation process, thereby obtaining a nonlinear displacement image. For example, as shown in FIG. 10, the sinusoidal period of the heating unit applied to the surface of the measurement object

Assuming Hz,

or

The nonlinear displacement image can be obtained by calculating the relative coefficient change at.

Displacement image generates displacement image by calculating amplitude value at specific frequency (frequency of heating cycle, multiple frequency, sum frequency of two frequencies or subtracted difference frequency) from (1,1) to (m, n), respectively. do.

주파수에서의 신호가

일 때 진폭값은

이고 위상값은

이다. 여기서 A와 B는

주파수에서 cos 성분과 sin 성분의 계수이다. The phase image is generated by obtaining a phase value instead of an amplitude coefficient value at the specific frequency position. For example in the frequency domain

The signal at the frequency

When is the amplitude value

And the phase value is

to be. Where A and B are

Cos component and sin component coefficient at frequency.

As described above, flowcharts for obtaining the displacement image and the phase image from the laser interference image and the phase shifted interference image are shown in FIGS. 11 and 12.

FIG. 13 is a general apparatus for detecting defects inside a measurement object 55 which is a plate-shaped fuel specimen using a general high frequency piezoelectric transducer 54 which is controlled by a computer 51 and signal processed. The measurement object 55 is installed in the scanning device 56 to scan the X and Y axes. Since the plate-shaped nuclear fuel measuring object is about 2 mm thick, a high frequency signal of about 20 MHz or more should be used to detect internal defects of the object using a pulse-echo time-of-flight longitudinal signal. The high frequency signal has high inspection efficiency only when the inspection is performed in the water 53 which is the water tank 52. This detection method can effectively extract defect information inside the measurement object. However, since all parts of the measurement object need to be examined, a long time is required to perform a complete test.

FIG. 14 is a diagram illustrating an internal configuration of a non-destructive inspection apparatus based on a tilt laser interferometer for measuring thermal deformation for detecting tilt defect image information inside a plate-shaped fuel specimen according to an embodiment of the present invention.

Referring to FIG. 14, a non-contact non-destructive inspection apparatus for detecting tilt defect image information inside a plate-shaped fuel sample according to an embodiment of the present invention may include a beam irradiator, a heating unit, an information collecting unit, and the like.

The heating units 101 and 102 may be heated without contacting the measurement object 114.

The beam irradiator may include gradient laser interferences 103 and 104 for obtaining laser interference images having gradient displacement information in one direction which is changed in a horizontal direction of the surface direction of the object 114 by heat.

The information collecting unit may be formed to extract defect information from the laser interference image obtained by the laser interference unit.

Here, the tilt laser interference image of the front surface of the measurement object 114 is measured by the tilt laser interference part 104 located at the front part, and the tilt laser interference image of the back side is measured by the tilt laser interference part 103 located at the back side. .

The heating unit 101 of the upper portion generates heat by the control device 111 controlled by the tilt-defect image information collecting unit 105 controls the heat source device 112 and the generated heat is generated by the heat spreader 113. The front of the measurement object 114 is evenly irradiated. In addition, the lower heating unit 102 generates heat by the control device 115 controlled by the defect image information collecting unit 105 controls the heat source device 116 and the generated heat is measured by the heat spreader 117. (114) The front surface is evenly irradiated, where the intensity of heat irradiated to the surface of the measurement object is repeatedly irradiated with the intensity of the sinusoidal wave form with a certain period.

Due to the heat irradiated to the measurement object, micro-deformation is generated at each position in the measurement object, and the deformation appears in the form of displacement on the surface of the measurement object. The tilt displacement in one direction of the displacement is measured by the tilt laser interference portion 104 on the upper part of the specimen and the tilt laser interference portion 103 on the lower portion of the specimen.

The tilt laser interference unit 103 located at the back of the measurement object generates an interference image by using an output beam of the laser 121. The output laser beam of the laser 121 is divided into a pass beam and a reflected beam by the beam splitter 122.

The passing beam is reflected by the mirror 123 and then adjusted by the filter 138 and then irradiated to the back of the measurement object through the beam diffusing optical system 124. The image on the back side is reflected by the mirror 127 which can be controlled by the phase shifting device through the beam splitter 125 and then reflected by the beam splitter 125 again to pass through the imaging lens 140 through the imaging sensor 140 The reference beam is incident to 141. The phase shifter may be a PZT 126. The image of the back of the measurement object 114 is reflected by the beam splitter 125 and reflected by the mirror 128 inclined at an angle, and then passes through the beam splitter 125 to the imaging sensor 141 through the imaging lens 140. A tilted interference image that is incident and interferes with the reference beam is acquired by the imaging sensor 128. The angle is arbitrarily adjustable.

The tilt laser interference image is obtained in the same manner on the front surface of the measurement object.

The tilt laser interference unit 104 positioned in front of the measurement object generates a tilt interference image of the front of the measurement object using the output beam of the laser 121. The laser beam reflected by the beam splitter 122 is adjusted by the filter 139 through the mirror 129 and then irradiated to the front surface of the measurement object 114 by the beam diffusion optical system 130. The irradiated front image is reflected by the mirror 133, which can be controlled to move to the PZT 132 via the beam splitter 131, and then reflected by the beam splitter 133, through the imaging lens 135. A reference beam is incident at 136. The front image of the measurement object 114 is reflected by the beam splitter 131 and reflected by the mirror 134 which is inclined at an angle, and then passes through the beam splitter 131 to the imaging sensor 136 through the imaging lens 135. An interference image that is incident and interferes with the reference beam is acquired by the imaging sensor 136 and includes the tilt image information.

The tilt defect image information collecting unit 105 includes a control and signal processing computer therein to obtain an hourly tilt phase map image from a tilt laser interference image obtained by time, and to obtain a horizontal tilt displacement image and a horizontal direction from the obtained hourly tilt phase map image. The gradient information of the gradient present in the test specimen can be obtained by obtaining the direction gradient phase image.

The method of heating the measurement object, the method of obtaining the laser interference image, and the method of extracting the tilt defect information are performed in the same manner as the method of extracting the displacement information in the horizontal direction of the surface of the measurement object by the defect image information collecting unit 5 of FIG. 1. .

Such a defect detection method of the present invention has the advantage that it can be used in the field by providing a defect image visually and can be a high-speed inspection compared to the conventional ultrasonic detection method.

As described above, the present invention has been described by specific embodiments such as specific components and the like. For those skilled in the art, various modifications and variations are possible from these descriptions. Therefore, the spirit of the present invention should not be construed as being limited to the described embodiments, and all of the equivalents or equivalents of the claims, as well as the following claims, are included in the scope of the present invention.

Claims (14)

A heating unit which heats the object to expand or contract a crack existing in the object at regular intervals;
A beam irradiator formed to irradiate beams in different directions on one surface and a rear surface of the object;
Collecting surface interference images of the one surface from beams of different directions irradiated to the surface, collecting surface interference images of the back surface from beams of different directions irradiated to the rear surface, surface interference images of the surface and back surfaces And a non-destructive information collection unit for extracting the thickness direction interference image of the object from the surface interference image of the object to extract the combined information of the object. The method of claim 1,
The beam irradiation unit,
A beam generator for irradiating a beam; And
And a beam splitter formed in the path of the beam so that the beam travels in at least two different paths. 3. The method of claim 2,
The beam irradiation unit,
And a phase shifting device formed on at least one path to change the phase of the beam passing through the path. The method of claim 1,
The heating unit includes:
A continuous oscillation laser device for heating the object; And
And a filter disposed on the path of the laser generated by the continuous oscillation laser device, the filter being controlled to transmit the laser with sine wave intensity over time. The method of claim 1,
The heating unit includes:
And a heat source device capable of heating the object to a strength of one sinusoidal wave shape or an intensity overlapping at least two sinusoidal waves. The method of claim 1,
The information collecting unit,
Obtain and store a horizontal interference image and a vertical interference image generated on one surface of the object in real time, obtain a time-phase horizontal phase map image from the horizontal interference image, and time-dependent vertical phase map from the vertical interference image. Non-contact destructive testing device comprising a signal processing module for obtaining an image. delete delete delete delete delete A heating unit heating the object to a certain period of intensity;
Generating a coherent image of each plane by irradiating a laser beam to the front and the back of the object;
An information collecting unit obtaining a time-phased phase map image of the front surface from the interference image of the front surface;
An information collecting unit obtaining a time-phased phase map image of the back side from the interference image of the back side;
Generating, by the information collecting unit, a displacement image and a phase image of the front surface by extracting an amplitude value and a phase value at a specific frequency from the phase map image of the front surface;
Generating a displacement image and a phase image of the back side by extracting an amplitude value and a phase value at a specific frequency from the phase map image of the back side;
Acquiring the relative displacement image information of the front and back sides of the object by using the difference between the displacement image of the front side and the displacement image of the back side; And
And a step of acquiring the relative phase image information of the front and back sides of the object by using the difference between the phase image on the front side and the phase image on the back side. The method of claim 12,
The heating unit heats the object to a sinusoidal intensity,
The specific frequency is,
And the heating unit includes a frequency corresponding to a heating cycle for heating the object and an integer multiple of the frequency. The method of claim 12,
The heating unit heats the object to a strength in the form of overlapping two or more sinusoids,
The specific frequency is,
And a frequency corresponding to the period of each sinusoidal wave, a frequency corresponding to the sum or difference of the frequencies, and an integer multiple of the frequency.

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