WO2016039564A1 - Apparatus and method for detecting defects in triplex bonding in lng carrier - Google Patents

Abstract

Disclosed is an apparatus for detecting defects in triplex bonding in an LNG carrier, the apparatus comprising: a heating unit for applying heat to the surface of an object to be inspected to generate a thermal wave propagating in the thickness-wise direction thereof; a thermographic camera for photographing the object to be inspected, which has been heated by the heating unit, to generate a thermal image; and a control unit for receiving and processing the thermal image to calculate information regarding defects which have formed in the object to be inspected. Such an apparatus and a method for detecting defects in triplex bonding in an LNG carrier can provide the benefit of automatically detecting the type, size and location of the defects occurring in the triplex bonding in an LNG carrier and of providing the detection results to a user.

Description

Defect Detection Device and Method of Triplex Bonded Part of LNG Carrier

The present invention relates to an apparatus and method for detecting defects in triplex bonds of LNG carriers, and more particularly, to triplex bonds of LNG carriers, which can automatically detect the presence, type, area, and size of defects occurring in triplex bonds of LNG carriers. A defect detection apparatus and method.

The LNG tank storage tank stores LNG at low temperature of -162 ℃, so it is designed as a primary barrier, insulation and secondary barrier structure to minimize heat transfer.

The primary barrier, which is in direct contact with the liquefied natural gas, is a membrane wall made of stainless steel to withstand cryogenic shrinkage and impact from sloshing.

Between the primary and outer walls is filled with insulation made of polyurethane, plywood, etc. to block heat transfer.

The heat insulating material is composed of a primary heat insulating material provided on the outside of the primary barrier and a secondary heat insulating material provided on the outside of the primary heat insulating material.

At this time, the secondary barrier is provided to complement the function of the primary barrier on the secondary insulation between the primary insulation, a triplex (triplex) is usually used.

The triplex is basically a glass fiber sheet bonded to both sides of an aluminum sheet, and its rigidity differs depending on the thickness of the aluminum sheet and the resin used.

The triplex used as the secondary barrier is made by bonding two triplexes of different rigidity, for example, rigid triplex and flexible triplex, using an adhesive.

In the meantime, defects such as bubbles, uncured, and debonding may occur during the construction of the triplex adhesive part, and the contractor should inspect and repair the defects of the triplex adhesive part.

However, conventionally, the inspection hole detects the whole quantity of a triplex adhesive part manually by the inspection hole in order to detect the defect of a triplex adhesive part.

Therefore, there is a problem that the inspection period is long and accurate inspection is difficult.

The present invention has been made to solve at least some of the problems of the prior art as described above, in one aspect, the LNG carrier that can automatically accurately detect defects such as bubbles, uncured and de-bonding of the triplex adhesive portion of the LNG carrier It is an object of the present invention to provide a triplex adhesive defect detection apparatus and method.

As one aspect for achieving at least some of the above objects, the present invention provides a heating unit for generating heat waves propagating in the thickness direction of the inspection object by applying heat to the surface of the inspection object; A thermal imaging camera for photographing an object heated by the heating unit to generate a thermal image; And a controller configured to receive and process the thermal image to calculate information on defects occurring in the inspection object.

In another aspect, the present invention is a heating step of generating heat waves propagating in the thickness direction of the inspection object by applying heat to the surface of the inspection object through a halogen lamp; Generating a thermal image by measuring radiant heat generated from the surface of the inspection object heated in the heating step; And image processing and signal processing the thermal image to image defects occurring in the inspection object.

According to one embodiment of the present invention having such a configuration, it is possible to obtain the effect that can automatically detect the type, size and generation area of the defects generated in the triplex adhesive portion of the LNG carrier to provide the user with the detection result.

1 is a schematic view showing the configuration of a defect detection apparatus according to an embodiment of the present invention.

2 is a flow chart of a defect detection method according to an embodiment of the present invention.

3 is a flowchart of image processing an amplitude image among characteristic images.

4 is a flowchart of image processing a phase image among characteristic images.

5 is a photograph showing a thermal image, a background image, and a corrected thermal image captured by a thermal imaging camera.

6 is a photograph showing an image processing process of an amplitude image.

7 is a photograph showing an image processing process of a phase image.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Also, the singular forms in this specification include plural forms unless the context clearly indicates otherwise.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

First, a defect detection apparatus according to an embodiment of the present invention will be described with reference to FIG. 1.

As illustrated in FIG. 1, the defect detecting apparatus 100 according to the exemplary embodiment may include a heating unit 110, a thermal imaging camera 120, and a controller 130.

For reference, the defect detection apparatus 100 according to an embodiment of the present invention may be configured as an independent device that can measure the inspection target area while moving the main body along the rail installed in the triplex adhesive portion of the LNG carrier, LNG It may be mounted on a robot that manufactures a triplex of lines and may be configured to detect defects at the same time as the triplex is manufactured.

The heating unit 110 may generate heat waves propagated in the thickness direction of the inspection object 1 by applying heat to the surface of the inspection object 1, that is, the triplex adhesive portion of the LNG carrier.

Here, since the heat wave generated by the heating unit 110 is propagated in a different form in the healthy part and the defective part of the inspection object 1, the amplitude and phase of the radiation wave generated on the surface of the inspection object 1 are different. do.

In an embodiment, the heating unit 110 may include a halogen lamp 111, a waveform generator 112, a signal amplifier 113, and a dimmer 114.

The halogen lamp 111 is a heat source for irradiating light to one surface of the inspection object 1 and may generate a heat wave having a single frequency propagated in the thickness direction of the inspection object 1.

In general, since the triplex adhesive portion of the LNG carrier has low heat permeability due to the thermal properties of the material, the halogen lamp 111 is a high output halogen lamp 111 capable of emitting high thermal energy that can properly transmit heat waves even in the triplex adhesive portion. It is preferred to be configured.

The waveform generator 112 may generate a waveform of a voltage signal applied to the halogen lamp 111.

In one embodiment, the waveform generator 112 may generate a voltage signal in the form of a square wave.

In the case of using the square wave voltage signal, the maximum value of the output of the halogen lamp 111 is longer than in the case of using the sine wave type voltage signal, and thus heats the test object 1 with high power. It has the advantage of being suitable for heating low performance triplex bonds.

On the other hand, in one embodiment, the waveform generator 112 may be controlled by the control unit 130 to be described later.

The signal amplifier 113 amplifies the output voltage output according to the voltage signal generated by the waveform generator 112 to the operating voltage of the halogen lamp 111. The signal amplifier 113 is not particularly limited, and various types of known signal amplifiers 113 may be employed.

The dimmer 114 may adjust the amount of light of the halogem lamp according to the voltage signal amplified by the signal amplifier 113. The dimmer 114 is not particularly limited, and various types of known dimmers 114 may be employed.

Meanwhile, the thermal imaging camera 120 may generate a thermal image by photographing the inspection object 1 heated by the heating unit 110.

As shown in FIG. 1, the thermal imaging camera 120 may be arranged to photograph one surface of the inspection object 1 in the same direction as the halogen lamp 111 with respect to the inspection object 1.

In one embodiment, the thermal imaging camera 120 may be synchronized with the heating unit 110 to photograph the inspection object 1 at regular intervals according to the period of the voltage signal generated by the waveform generator 112.

When the thermal imaging camera 120 and the heating unit 110 are synchronized as described above, the heating unit 110 applies heat modulated by a step function to the inspection object 1 according to a square wave-shaped voltage signal, and the thermal image The camera 120 photographs the inspection object 1 according to the signal generated by the step function, and extracts the phase change between the phase of the heat source wavelength and the phase of the measurement wavelength, thereby using the phase locking surface of the inspection object 1. It has the advantage of being able to detect minute changes in.

The controller 130 may receive the thermal image generated by the thermal imaging camera 120 and process the received thermal image to calculate information of a defect occurring in the inspection object 1.

In an exemplary embodiment, the controller 130 may calculate the type, size, and generation area of the defect occurring in the inspection object 1.

In general, defects such as bubbles, uncured and debonding may occur in the triplex adhesive portion of the LNG carrier. Therefore, the control unit 130 may calculate so that the user can know what defects among bubbles, uncured, and debonding occurred in the inspection object (1).

In addition, since the heating unit 110 heats the inspection object 1 in the form of a square wave as described above, the control unit 130 has a generation time of the voltage signal generated by the waveform generator 112 at 0, 1/2. Thermal image at the period and one cycle It can be configured to calculate the amplitude (A) and phase (Φ) of the heat wave generated in the inspection object (1) through a total of three thermal images.

Here, the amplitude A of the heat wave can be obtained by the following Equation 1 by using the temperature R at a specific period T of the heat wave as a variable.

[Equation 1]

In addition, the phase Φ of the heat wave can be obtained by the following Equation 2 using the temperature R at a specific period T of the heat wave as a variable.

[Equation 2]

Here, the controller 130 may calculate the phase Φ and the amplitude A of the thermal wave in the thermal image, and calculate defect information based on the calculated phase Φ and the amplitude A of the thermal wave.

For reference, when detecting a defect of the triplex adhesive portion of the LNG carrier only through the phase Φ of the hot wave, there is a problem that the defect is not detected at a specific period T. This is because there is a defect sensitive to the amplitude A among the defects, and a defect sensitive to the phase?.

Therefore, the defect detecting apparatus 100 according to an embodiment of the present invention can accurately detect various kinds of defects by analyzing not only the phase Φ of the heat wave generated in the inspection object 1 but also the amplitude A. Has an advantage.

Here, the amplitude of the heat wave generated in the inspection object 1 is a measure of the degree to which the inspection object 1 is heated.

On the other hand, the controller 130 may image the information of the defect occurred in the inspection object 1 through the image processing and the signal processing algorithm to output the image so that the user can know.

Hereinafter, an operation of calculating defect information through image processing and signal processing on the thermal image of the controller 130 will be described.

First, the controller 130 may generate a corrected thermal image by extracting a background image from the thermal image generated by the thermal camera 120.

The controller 130 may generate the characteristic image from the amplitude and phase of the heat wave based on the corrected thermal image.

Here, the characteristic image may include a phase image and an amplitude image.

In addition, the controller 130 may convert the generated characteristic image into a black and white image having a value between 0 and 1. FIG.

Finally, the controller 130 may generate a binary image by expanding the histogram of the obtained black and white image.

Meanwhile, in one embodiment, the controller 130 may extract the amplitude image of the thermal wave from the thermal image, and calculate the position and size of the bubble defects generated in the inspection object 1 based on the extracted amplitude image.

That is, the controller 130 may detect bubble defects through the amplitude image.

In addition, the controller 130 may calculate the size of the actual bubble defect by substituting the size of the bubble defect shown in the black and white image finally obtained by image processing the amplitude image as described above into a preset correlation function.

Here, the correlation function is a function of using x as the size of the detected bubble defect and y as the estimated size of the actual bubble defect, and are generally represented as a nonlinear function.

Here, the estimated size of the actual bubble defect is data on the defect size obtained through the X-ray inspection or the actual measurement of the inspection object (1) where the defect occurred.

Therefore, the correlation function is used to determine various sizes of bubble defects detected by the defect detection apparatus 100 according to an embodiment of the present invention, and actual bubble defects detected by the X-ray inspection or actual measurement of the specimen. Can be obtained by comparing various sizes.

Based on this data, the controller 130 may calculate the size of the actual bubble defect by substituting the size of the bubble defect on the binary image obtained through the image processing into the x value of the correlation function.

Meanwhile, in one embodiment, the controller 130 may extract the phase image of the heat wave from the thermal image, and calculate the position and size of the uncured defect generated in the inspection object 1 based on the extracted phase image.

That is, the controller 130 may detect an uncured defect through the phase image.

The defect detection apparatus 100 according to an embodiment of the present invention as described above has the advantage of automatically calculating the type, size and generation area of defects by moving the triplex adhesive part of the LNG carrier, and providing the image to the user. have.

Next, a defect detection method according to an embodiment of the present invention will be described with reference to FIGS. 2 to 4.

2 is a flowchart of a defect detection method according to an embodiment of the present invention, FIG. 3 is a flowchart of image processing an amplitude image among characteristic images, and FIG. 4 is a flowchart of image processing a phase image among characteristic images.

As shown in FIG. 2, first, heat is applied to the surface of the inspection object 1 through the halogen lamp 111 to generate heat waves propagating in the thickness direction of the inspection object 1 (step S200).

In one embodiment, the halogen lamp 111 may be operated by applying a voltage through the following process.

First, a voltage signal applied to the halogen lamp 111 through the waveform generator 112 may be generated in the form of a square wave.

Thereafter, the voltage signal generated through the signal amplifier 113 may be amplified to the operating voltage of the halogen lamp 111.

Finally, the amount of light of the halogen lamp 111 may be adjusted according to the voltage signal amplified by the dimmer 114.

Meanwhile, radiant heat generated on the surface of the heated inspection object 1 may be measured by the thermal imaging camera 120 to generate a thermal image (a of FIG. 5) (step S210).

At this time, the radiant heat measurement operation of the inspection object 1 is synchronized with the period of the voltage signal, so that the thermal image may be generated according to the period of the voltage signal.

The defect detection method according to the exemplary embodiment of the present invention may generate a thermal image when the generation time of the voltage signal is 0, 1/2, and 1 cycle.

Therefore, the characteristic image to be described later is generated as an amplitude image and a phase image when the generation time of the voltage signal is 0, 1/2 cycle and 1 cycle.

In addition, when a thermal image is generated, a characteristic image may be generated by calculating amplitude and phase based on the thermal image (step S220).

Here, an amplitude image (a of FIG. 6) and a phase image (a of FIG. 7) may be obtained as the characteristic image.

Thereafter, the amplitude image (a of FIG. 6) and the phase image (a of FIG. 7) of the characteristic image are compensated for by the nonuniform heating effect, thereby improving the amplitude image (b of FIG. 6) and the improved phase image (b of FIG. 7). Can be generated (step S230).

In one embodiment, the improved thermal image (c of FIG. 5) may be obtained by extracting a background image (b of FIG. 5) by spatially low frequency filtering the thermal image (a of FIG. 5). Here, the spatial domain low frequency filtering technique is a technique for integrating a mask while moving the entire image area, and obtains a background image (b) of FIG. 5 at a speed about 40 times faster than a conventional polynomial combining technique. There is an advantage.

Here, the non-uniform heating effect is to compensate for the non-uniform heating of the test metabolism by the halogen lamp 111, the non-uniform heating effect can be compensated for by using an image filter.

On the other hand, if the characteristic image is a phase image (a in FIG. 7), in the improved phase image (b in FIG. 7), all the positive phase values are converted to 0 to adjust an image in which the defect portion is emphasized (FIG. 7). C) may be generated.

In the case of the uncured defect, the negative phase has a negative phase. Therefore, when all of the positive phase values, which are healthy regions, are converted to zero, the defective portion is emphasized.

In addition, the improved characteristic image generated through the above process may be converted into a black and white image (c in FIG. 6 and d in FIG. 7) by normalizing the value of each pixel to 0 to 1 (step S240). .

Thereafter, the histogram of the black and white image is analyzed to generate a binary image (d of FIG. 6 and f of FIG. 7) (step S250).

On the other hand, the defect detection method according to an embodiment of the present invention may image the amplitude image and the phase image of the characteristic image by different techniques.

First, the case of an amplitude image is demonstrated with reference to FIG.

After the black and white image (c of FIG. 6) of the amplitude image is generated, the contrast amplification image (d of FIG. 6) may be generated by increasing the contrast of the black and white image (c of FIG. 6) (step S241).

The contrast amplified image (d of FIG. 6) may more clearly represent signal changes caused by bubble defects.

Subsequently, the contrast amplified image (d of FIG. 6) is treated as a defective part larger than the first threshold value by using a preset first threshold value, and the healthy part smaller than the first threshold value is treated as 0 for binary value. An image may be generated (step S250).

The binary image may be morphologically processed to generate an image from which noise has been removed (FIG. 6E) (step S260).

Here, various known image processing techniques may be used as the morphological operation processing technique.

Subsequently, the size of the defective portion of the noise-free binary image (e) of FIG. 6 is measured (f of FIG. 6), and the size of the actual bubble defect is calculated by substituting the measured value of the defective portion into the correlation function. It may be (step S270).

Next, with reference to FIG. 4, the case of a phase image is demonstrated.

After the black and white image of the phase image (d of FIG. 7) is generated, the generated black and white image (d of FIG. 7) is subjected to morphological calculation to smooth the outline of the uncured defect part, thereby reducing the noise. E) of FIG. 7 may be generated (step S242).

Here, the morphological operation may be used as the expansion operation and the erosion operation, but is not limited thereto.

In addition, the morphological operation image (e of FIG. 7) is treated as a defective part larger than the second threshold value by using a preset second threshold value, and the healthy part smaller than the second threshold value is treated as 0 and binary. An image (f of FIG. 7) may be generated (step S250).

The user can identify the uncured defect area through the binary image of the phase image (f of FIG. 7).

While the invention has been shown and described with respect to particular embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as set forth in the claims below. I want to make it clear.

Claims (24)

A heating unit generating heat waves propagating in the thickness direction of the inspection object by applying heat to the surface of the inspection object; A thermal imaging camera for photographing an object heated by the heating unit to generate a thermal image; And A controller which receives the thermal image and processes the thermal image to calculate information of a defect occurring in an inspection object; Triplex bond defect detection device of the LNG carrier comprising a. The method of claim 1, The heating unit, Halogen lamp for irradiating light to the inspection object; A waveform generator for generating a waveform of a voltage applied to the halogen lamp; A signal amplifier for amplifying the voltage signal generated by the waveform generator; And A dimmer controlling an amount of light of the halogen lamp according to the voltage signal amplified by the signal amplifier; Triplex bond defect detection device of the LNG carrier comprising a. The method of claim 1, The thermal imaging camera is a defect detection device for a triplex adhesive portion of the LNG carrier is synchronized with the heating unit to photograph the inspection object in accordance with the period of the voltage signal generated by the waveform generator. The method of claim 2, The thermal imaging camera and the halogen lamp are triplex bond defect detection device of the LNG carrier is disposed on one side of the inspection object. The method of claim 2, The waveform generator is a triplex bond defect detection device of the LNG carrier for generating a voltage signal of the square wave (square wave). The method of claim 5, And the controller calculates an amplitude and a phase of the heat wave in the thermal image when the voltage signal generation time is 0, 1/2 cycle and 1 cycle. The method of claim 1, The control unit is a defect detection device of the triplex bond portion of the LNG carrier for calculating the type, size and generation area of the defect occurred in the inspection object. The method of claim 1, The control unit calculates the phase and amplitude of the heat wave in the thermal image, the triplex bond defect detection apparatus of the LNG carrier for calculating the defect information based on the phase and amplitude of the heat wave. The method of claim 8, The control unit is a defect detection apparatus for LNG triplex adhesive portion for imaging the thermal image through the image processing and signal processing algorithm information of the defect occurred in the inspection object. The method of claim 9, The control unit, Generate a characteristic image from the amplitude and phase of the heat wave, Extracting a background image from the feature image to generate a corrected feature image, Converting the corrected characteristic image into a black and white image having a value between 0 and 1, Triplex bond defect detection device of the LNG carrier to generate a binary image through the histogram of the monochrome image. The method of claim 8, And the control unit extracts an amplitude image of the heat wave from the thermal image and calculates a position and a size of bubble defects generated in the inspection object based on the amplitude image. The method of claim 11, And the control unit calculates the size of the actual bubble defect by substituting the size of the bubble defect shown in the image obtained by image processing the amplitude image into a preset correlation function. The method of claim 8, And the control unit extracts a phase image of the heat wave from the thermal image and calculates a position and size of an uncured defect generated in an inspection object based on the phase image. A heating step of applying heat to the surface of the inspection object through the halogen lamp to generate heat waves propagating in the thickness direction of the inspection object; Generating a thermal image by measuring radiant heat generated from the surface of the inspection object heated in the heating step; And Image-processing and signal-processing the thermal image to image defects occurring in an inspection object; Triplex bond defect detection method of the LNG carrier comprising a. The method of claim 14, The heating step, Generating a voltage signal applied to the halogen lamp in the form of a square wave; Amplifying the voltage signal; And Adjusting an amount of light of the halogen lamp according to the voltage signal; Triplex bond defect detection method of the LNG carrier comprising a. The method of claim 15, The generating of the thermal image may include detecting defects of a triplex adhesive part of an LNG carrier in which a radiation heat measurement operation of the inspection object is synchronized with a period of the voltage signal. The method of claim 14, Imaging the defects, Generating a characteristic image by calculating amplitude and phase based on the thermal image; Extracting a background image from the feature image and generating a corrected feature image; Converting the corrected feature image into a black and white image; And Analyzing the histogram of the black and white image to generate a binary image; Triplex bond defect detection method of the LNG carrier comprising a. The method of claim 17, The corrected thermal image generating step is a defect detection method of a triplex bond portion of the LNG carrier to extract a background image by performing a low-frequency filtering of the captured image of the thermal image. The method of claim 17, The characteristic image generating step is a defect detection method for a triplex bond portion of LNG carriers to generate an amplitude image and a phase image when the voltage signal generation time is 0, 1/2 cycle and 1 cycle. The method of claim 19, The characteristic image generating step comprises the steps of compensating for the non-uniform heating effect of the amplitude image and the phase image to generate an improved amplitude image and improved phase image LNG carrier defect detection method. The method of claim 20, If the characteristic image is a phase image, And converting a positive phase value to zero in the phase image. The method of claim 17, The binary image generating step, If the characteristic image is an amplitude image, Generating a contrast amplified image by increasing the contrast of the amplitude image; Generating the binary image by processing the contrast amplified image as a defect portion larger than the first threshold value and a sound portion smaller than the first threshold value with 0 using a preset first threshold value; And Removing noise through a morphological operation of the binary image; Triplex bond defect detection method of the LNG carrier comprising a. The method of claim 22, The binary image generating step, And calculating the size of the actual defect by substituting the size of the defect portion of the binary image into a preset correlation function. The method of claim 17, The binary image generating step, If the characteristic image is a phase image, Generating a morphologically calculated image by reducing the noise by softening the outline of the defect portion through the morphological calculation of the phase image; And Generating a binary image by processing the morphological calculation image as a defect part larger than the second threshold value as 1 and a healthy part smaller than the second threshold value as 0 using a second preset threshold value; Triplex bond defect detection method of the LNG carrier comprising a.

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