Method, system and program for reducing heat generation caused by standing waves in ultrasonically excited thermography nondestructive testing

Abstract

To suppress a generated standing wave from being reflected in a flaw detection method for inspecting an internal defect of an inspection objective material from temperature change of thermography by generating heat by exciting the internal defect through ultrasonic vibrations.SOLUTION: According to the present invention, a photography position of an infrared camera 21 for an inspection objective material m is fixed, and excitation by a vibrator 12 is carried out at a plurality of excitation positions, wherein a computer 3 differentiates temperature distribution data on a frame following an initial frame among a plurality of pieces of time-series temperature distribution data acquired through the excitation with data on the initial frame, and averages data on differences that lapsed times from a start of photography correspond among the respective groups to reduce reflection of a standing wave, thereby making an internal defect clear.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for reducing heat generation caused by standing waves in ultrasonically excited thermography nondestructive testing, a system therefor, and a program therefor. [Background technology]

[0002] As a method for detecting internal defects such as internal defects in a test material, unevenness of the material, welding state (poor welding), or fusion state (peeling), a method is becoming widespread in which the test material is heated, infrared rays emitted from the test material surface are captured by an infrared camera equipped with multiple temperature sensing elements, and the change in temperature value is observed by infrared thermography. For example, the method of observing the change in temperature value of the test material by the infrared thermography is becoming widespread to detect internal defects in metals, plastics, ceramics, concrete, and other materials, fusion of plastics, and delamination between carbon fiber reinforced plastics.

[0003] More specifically, traditionally, ultrasonic testing has involved applying ultrasonic waves to metals, acrylic, concrete, etc., and detecting internal defects from the reflected waves. Recently, however, instead of examining the reflected waves of ultrasonic waves, a new type of infrared thermography (thermography method) called ultrasonic excitation thermography (vibrothermography) has become known in which powerful ultrasonic vibrations (powerful ultrasonic vibrations) are applied to metals, CFRP plates, etc., causing friction at internal defects, generating heat due to friction in the defective parts, and observing the temperature change.

[0004] As an example, as ultrasonically excited thermography, methods have been proposed in which ultrasonic vibrations are generated and applied to a test material, as shown in Patent Documents 1 to 3. Patent documents 2 and 3 show that ultrasonic waves are transmitted to the test material via an intermediary liquid, while Patent document 1 employs a vibration method in which an oscillator (vibration part) is directly brought into contact with the surface of the test material to apply ultrasonic vibrations to the test material without using the intermediary liquid.

[0005] More specifically, it is known that cracks in sintered metal gears, i.e., cracks in gears, can be detected by vibration, which generates friction at the cracked or defective parts, causing the cracked or defective parts to heat up. The above-mentioned high-power ultrasonic vibration is a technology that is used not only to detect defects, but also to fuse metals and plastics with frictional heat. As described above, when ultrasonic vibrations are applied to a test material, heat is generated inside due to the vibration waves, and the test material is not limited to plate materials, and materials of various shapes can be used. The above-mentioned patent documents show that the photographing position of the infrared camera is changed. However, in all of the above cases, the position of the transducer (excitation position) is constant. Also, the vibration frequency of the transducer that performs the excitation is considered to be constant.

[0006] On the other hand, it is also known that the ultrasonic vibration waves incident on the test material reach a steady state over time. As an example, when observing a thermograph taken after applying powerful ultrasonic vibrations to an acrylic plate (test material), temperature spots (temperature patches) appear on the surface of the plate, as shown in Figures 10(A) and (B). FIG. 10(A) is a thermograph of the acrylic plate without any internal defects, and FIG. 10(B) is a thermograph of the acrylic plate with an internal defect (marked "defective portion" in the figure). It is known that these spots form various patterns depending on the conditions of the applied vibration (Non-Patent Document 1). The cause of the above-mentioned spotting is the standing wave of ultrasonic vibration induced in the component, and it changes depending on the place where the vibration is applied and the shape of the target object. As mentioned above, if there is a defect such as a "crack" in the object to be inspected (test material) such as a plate, the defective part will heat up due to frictional heat caused by vibration (Fig. 10(B)). As can be seen from Fig. 10(A)(B), if the part is identified as defective in advance, it can be identified, but if not, it is difficult to distinguish it from other heat-generating parts other than the defect. As described above, the patterns caused by standing waves may be mistaken for heat generation due to internal defects such as defects, and measures are required during inspection. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6079098 [Patent Document 2] Patent No. 6573183 [Patent Document 3] Patent No. 6573184 [Non-Patent Document 1] Japanese Society for Nondestructive Inspection, 2020 Autumn Lecture Conference "Unwanted heat generation caused by standing waves in ultrasonically excited thermography and its impact on inspection" / Shinpei Kishimoto (Tokushima University), Masashi Ishikawa (Tokushima University), Hideo Nishino (Tokushima University), Ryo Fukui (KJTD Co., Ltd.), Yoshiro Habuka (KJTD Co., Ltd.), Yutaka Nishino (KJTD Co., Ltd.) Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to reduce the temperature variations caused by standing waves, which have been a problem in conventional inspections using ultrasonically excited thermography, and to achieve highly accurate inspections. In other words, the present invention aims to solve the problem of a flaw detection method in which a vibrating part is brought into contact with the surface of a test material and vibrated with ultrasonic vibrations to generate frictional heat and heat the internal defects of the test material, and the temperature change of the test material is captured by thermography to check for internal defects, by preventing the identification of the internal defects from being hindered by the reflection of temperature changes caused by standing waves generated in the test material by the vibration. [Means for solving the problem]

[0009] The present invention relates to a flaw detection method for examining internal defects in the entire test material or a specific area of ​​the test material by applying ultrasonic vibrations to the test material using a vibration unit that is in contact with the test material, heating the internal defects of the test material, and observing temperature changes in thermography of the test material surface, i.e., an image that visualizes the temperature distribution on the test material surface. The method comprises: setting a constant shooting position for acquiring the image and a constant frequency of the ultrasonic vibration for the test material; applying the ultrasonic vibration to the test material; taking two or more frames of images with different elapsed times from the start of the shooting; defining the first image from the start of the shooting as an initial image; and observing temperature changes relative to the initial image for other images taken at least after the initial image. and calculating a distribution of the amount of change in temperature, the imaging is started simultaneously with the start of vibration or a predetermined time before the start of vibration, ultrasonic vibration is applied to the test material at a plurality of vibration positions different from each other, and a plurality of the initial images and a plurality of the other images are obtained by imaging using the ultrasonic vibration at each of the plurality of vibration positions, the plurality of other images are obtained after the vibration is applied, and the plurality of other images correspond to each other in terms of the elapsed time from the start of imaging, and the method for detecting internal defects is provided from a distribution of average changes obtained by averaging the distribution of the amount of change in temperature obtained by calculating the distribution of the amount of change in temperature for each of the vibration positions. The above-mentioned internal defects include cracks, cavities, and other defects inside the test material, as well as unevenness of materials, welding defects in test materials with welded parts, and peeling at fusion parts in test materials with fusion parts. Also, checking for the above-mentioned internal defects means checking at least one of the following: the presence or absence of internal defects, the position of the internal defects, the shape of the internal defects, and the size and range of the internal defects. Furthermore, the term "ultrasound" used here refers to sound waves that are not intended to be heard by the human ear, and refers to sound waves of 10 kHz or higher. Furthermore, "corresponding elapsed times from the start of ultrasonic excitation" as used herein includes not only those having the exact same elapsed time from the start of ultrasonic excitation, but also those having different elapsed times, for example, as long as the ordinal numbers (frame numbers) of the other thermal images subtracted in the initial thermal image match even if the elapsed times from the start of ultrasonic excitation are slightly different. In other words, if the elapsed times from the start of ultrasonic excitation are roughly the same, then "corresponding" includes those having roughly the same elapsed time. Furthermore, the present invention has provided a flaw detection method in which one or more distributions of temperature change amounts are calculated as a distribution of frequency-changed temperature change amounts from the image obtained by changing the frequency of the ultrasonic vibration and exciting the test material at at least some of the multiple different vibration positions, and the averaging is performed by adding each of the distributions of frequency-changed temperature change amounts. Furthermore, the present invention relates to a flaw detection method for examining internal defects in the entire test material or a specific region of the test material by applying ultrasonic vibrations to the test material using a vibration part that is in contact with the test material, and observing the temperature change using thermography of the test material surface, i.e., an image that visualizes the temperature distribution on the test material surface, the method comprising: setting both the photographing position for obtaining the image and the vibrating position for applying the vibration to the test material to be constant; photographing two or more frames of the image with different elapsed times from the start of the photographing; defining the first image from the start of the photographing as an initial image; and determining the amount of temperature change from the initial image for at least the other images photographed after the initial image. The present invention provides a flaw detection method for detecting internal defects from a distribution of average changes obtained by averaging the distribution of the temperature change amounts obtained by calculating the distribution of the temperature change amounts for each of the frequencies, the imaging being started simultaneously with the start of the vibration or a predetermined time before the start of the vibration, applying ultrasonic vibrations of a plurality of different frequencies to the test material, and acquiring a plurality of the initial images and a plurality of the other images by each imaging using the ultrasonic vibrations at each of the plurality of different frequencies, the plurality of the other images being acquired after the vibration, and the plurality of the other images being acquired corresponding to each other in terms of the elapsed time from the start of the imaging. Furthermore, the present invention provides a method for detecting internal defects by capturing an image group of three or more frames in a time series in each of the photographs in which the frequency and the vibration position are constant, calculating the distribution of temperature change for at least a plurality of the other images relative to the captured initial image, and forming a set of temperature change distribution groups from the plurality of sets of image groups obtained in each photographing operation in which the ultrasonic vibration is applied to the test material at a plurality of different vibration positions, calculating a plurality of sets of temperature change distribution groups with different vibration positions, averaging the plurality of temperature change distribution groups with corresponding elapsed times from the start of the photographing, and then averaging at least one of the first observation target and the second observation target as the observation target. First observation object: at least one distribution of average changes selected from the distributions of multiple average changes of the time series obtained by the averaging Second observation object: a phase image obtained by Fourier transforming the distribution of the plurality of average changes in time series Furthermore, the present invention provides a flaw detection method in which, in each of the photographs in which the frequency and the vibration position are constant, a group of three or more frames of images are photographed in a chronological order, a distribution of temperature change for at least a plurality of the other images relative to the photographed initial image is calculated, and the chronological distributions of the plurality of temperature change amounts are made into a set of temperature change distribution groups, ultrasonic vibrations of a plurality of different frequencies are applied to the test material to calculate a plurality of sets of temperature change distribution groups with different frequencies, the distributions of the plurality of temperature change amounts corresponding to the elapsed time from the start of the photographing are averaged between the plurality of sets of temperature change distribution groups, and the internal defects are examined using at least one of the next first observation target and the second observation target as the observation target. First observation object: at least one distribution of average temperature change selected from the distributions of multiple average changes of the time series obtained by the averaging Second observation object: a phase image obtained by Fourier transforming the distribution of the plurality of average changes in time series The present invention also provides a flaw detection system that includes a vibration unit that applies ultrasonic vibrations to the test material using a vibration unit that is in contact with the test material to heat internal defects in the test material, and an image capture unit that can capture two or more frames of thermography of the test material surface, that is, temperature distribution data that can be converted into image data that visualizes the temperature distribution on the test material surface, the image capture unit having a heat detection unit such as a thermal detection camera equipped with a plurality of elements that detect infrared rays, and that makes it possible to examine internal defects in the test material from temperature changes in the temperature distribution data on the test material surface captured by the heat detection unit, The internal defect clarification mechanism includes an internal defect clarification mechanism that suppresses the hindrance of the identification of the internal defect due to the reflection of the temperature change caused by the standing wave generated in the test material by the vibration in the temperature distribution data, and the internal defect clarification mechanism includes a placement tool that enables the imaging unit to take the multiple continuous images at different vibration positions by arranging the vibration unit at multiple vibration positions different from each other on the surface of the test material, and a temperature change distribution data between the two or more frames of temperature distribution data acquired by the heat detection unit and acquired for the multiple vibration positions. the temperature distribution data is calculated by averaging a plurality of temperature change distribution data calculated from the obtained temperature distribution data, to calculate average change distribution data, an output unit, and a control unit, at least the data processing unit, the output unit, and the control unit are constructed by a computer and a flaw detection program installed in the computer, the placement tool can at least place the vibration unit in a state in which the vibration unit is in contact with the test material during the photographing, the placement tool can sequentially change the vibration position of the vibration unit by attaching / detaching or moving the vibration unit with respect to the test material, thereby enabling the placement at a plurality of different vibration positions, or can place the vibration unit at a plurality of different vibration positions simultaneously, the control unit starts photographing by the photographing unit simultaneously with the start of vibration by the vibration unit or a predetermined time before the start of vibration, the photographing unit inputs the temperature distribution data acquired by the photographing to the data processing unit in direct or indirect association with the elapsed time, and the control unit sets the temperature distribution data at the start of the photographing, i.e., the first frame, input to the data processing unit from the heat sensing unit as initial temperature distribution data,and causes the data processing unit to calculate a distribution of temperature changes with respect to the initial temperature distribution data for at least the other temperature distribution data captured after vibration applied later than the initial temperature distribution data as the temperature change distribution data, and further the control unit corresponds the elapsed time from the start of the imaging between the other temperature distribution data acquired by setting the vibration positions to a plurality of positions, and causes the data processing unit to calculate an average of the plurality of temperature change distribution data as the average change distribution data, and the output unit can output at least one of the average change distribution data, data based on the average change distribution data, and data related to the internal defect discrimination result determined by the control unit in the data processing unit, in response to an operation by an operator or automatically, and the output unit includes at least one of a display that can display the output data to an operator, a printing device that can print the output data, and a recording device that records the output data on a recording medium that can be played back by another computer or video device. Furthermore, in the present invention, the vibration unit can change the frequency of the ultrasonic vibration and vibrate at least a portion of the vibration unit arranged at a plurality of different vibration positions with respect to the test material, and the control unit causes the data processing unit to calculate one or more of the distribution data of the temperature change amounts as frequency-change temperature change distribution data from the temperature distribution data acquired by changing and vibrating, and the control unit can provide a flaw detection system in which the data processing unit calculates the distribution data of the average temperature change amount by adding each of the distribution data of the frequency-change temperature change amounts to the average. Furthermore, the present invention provides a flaw detection system that includes a vibration unit that applies ultrasonic vibrations to the test material using a vibration unit that is in contact with the test material to heat internal defects in the test material, and an image capture unit that can capture two or more frames of thermographic data of the test material surface, that is, temperature distribution data that can be converted into image data that visualizes the temperature distribution on the test material surface, the image capture unit having a heat detection unit such as a thermal detection camera equipped with a plurality of elements that detect infrared rays, and that can detect internal defects in the test material from temperature changes in the temperature distribution data of the test material surface captured by the heat detection unit. The present invention includes at least a positioning tool capable of positioning the vibration unit in a state of contact with the test material during the photographing, and an internal defect clarification mechanism that suppresses the impairment of identification of the internal defect due to the reflection of a temperature change caused by a standing wave generated in the test material by the vibration in the temperature distribution data, and the internal defect clarification mechanism can perform the vibration with ultrasonic vibrations of different frequencies for each of the continuous photographing by changing the frequency of the ultrasonic vibration of the vibration unit, and can detect temperature changes between the two or more frames of temperature distribution data acquired by the heat sensing unit. The temperature distribution data acquisition system includes a data processing unit that calculates a distribution data of a temperature change amount and calculates an average change amount distribution data by averaging a plurality of the temperature change amount distribution data calculated from the temperature distribution data acquired for the plurality of images taken at different frequencies, an output unit, and a control unit. At least the data processing unit, the output unit, and the control unit are constructed by a computer and a flaw detection program installed in the computer. The control unit starts the image taking by the image taking unit simultaneously with the start of vibration by the vibration applying unit or a predetermined time before the start of vibration. The image taking unit inputs the temperature distribution data acquired by the image taking in direct or indirect association with the elapsed time to the data processing unit. The control unit causes the data processing unit to calculate the distribution data of the temperature change amount relative to the initial temperature distribution data for the other temperature distribution data taken after vibration at least after the initial temperature distribution data, as the distribution data of the temperature change amount. Further, the control unit isThe frequency is set to a plurality of frequencies so that the plurality of acquired other temperature distribution data correspond to each other in terms of the elapsed time from the start of the imaging, and the average of the plurality of temperature change amount distribution data is calculated as the average change amount distribution data by the data processing unit, and the output unit can output at least one of the average change amount distribution data, data based on the average change amount distribution data, and data related to the internal defect discrimination result determined by the control unit in the data processing unit, either in response to an operation by an operator or automatically, and the output unit is provided with at least one of a display that can display the output data to an operator, a printing device that can print the output data, and a recording device that records the output data on a recording medium that can be played back by another computer or video device. Furthermore, in the present invention, the photographing unit photographs three or more frames of the temperature distribution data in a time series in each of the photographs performed with the frequency and the vibration position constant, and the control unit causes the data processing unit to calculate distribution data of the amount of temperature change for at least each of the other temperature distribution data relative to the photographed initial temperature distribution data, and acquires the time series distribution data of the amount of temperature change as a set of distribution data of the amount of temperature change, and the control unit causes the data processing unit to calculate a plurality of sets of distribution data of the amount of temperature change for different vibration positions from the plurality of sets of temperature distribution data obtained in each photograph performed by applying the ultrasonic vibration to the test material at a plurality of different vibration positions, A flaw detection system has been provided in which, between multiple sets of temperature change distribution data groups, the multiple temperature change distribution data corresponding to the elapsed time from the start of shooting are averaged to calculate the average change distribution data, and the control unit can output at least one of the following first data and second data to the output unit as data based on the average change distribution data, either in response to an operator's operation or automatically. First data: at least one average change amount distribution data corresponding to a predetermined elapsed time from the start of the imaging selected by an operator or set in advance from a plurality of time-series average change amount distribution data obtained by the averaging Second data: Phase distribution data obtained by subjecting the plurality of time-series average change amount distribution data to Fourier transform in the data processing unit. In the present invention, the photographing unit photographs three or more frames of the temperature distribution data in a time series in each of the photographs performed with the frequency and the vibration position kept constant, and the control unit causes the data processing unit to calculate distribution data of the amount of temperature change for at least each of the other temperature distribution data relative to the photographed initial temperature distribution data, and acquire the time-series distribution data of the amount of temperature change as a set of distribution data of the amount of temperature change, and the control unit causes the data processing unit to calculate a plurality of sets of distribution data of the amount of temperature change having different frequencies from the plurality of sets of the temperature distribution data obtained in each photograph performed by applying the ultrasonic vibrations of a plurality of different frequencies to the test material, A flaw detection system has been provided in which, between multiple sets of temperature change distribution data groups, the multiple temperature change distribution data corresponding to the elapsed time from the start of shooting are averaged to calculate the average change distribution data, and the control unit can output at least one of the following first data and second data to the output unit as data based on the average change distribution data, either in response to an operator's operation or automatically. First data: at least one average change amount distribution data corresponding to a predetermined elapsed time from the start of the imaging selected by an operator or set in advance from a plurality of time-series average change amount distribution data obtained by the averaging Second data: Phase distribution data obtained by subjecting the plurality of time-series average change amount distribution data to Fourier transform in the data processing unit. Furthermore, the present invention can provide the flaw detection program to be introduced into each of the flaw detection systems. Effect of the Invention

[0010] In the present invention, a vibrating part is brought into contact with the surface of a test material and vibrated with ultrasonic vibrations, thereby generating frictional heat and heating the internal defects of the test material, and the temperature change of the test material is captured by thermography.In this type of flaw detection to check for internal defects, it is possible to prevent the identification of the internal defects from being hindered by the reflection of temperature changes caused by standing waves generated in the test material by the vibration. That is, the present invention reduces surface temperature changes (mottle images) caused by standing waves, making it easier to distinguish heat-generating areas caused by defects. Furthermore, by implementing the present invention, the image that is the inspection result of the internal defect can be displayed to the operator (observer) in a relatively short time. Since the standing waves are not noticeable, even an operator who has little experience in inspecting internal defects can easily determine the defective portion from the image that is the inspection result, as described above. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2A is an explanatory diagram of a flaw detection system according to an embodiment of the present invention, and FIG. 2B is a schematic perspective view showing an example of a vibration unit of the flaw detection system of FIG. [Diagram 2] FIG. 2A is a schematic plan view of a test material showing an example of a vibration position on the surface of the test material to be vibrated by a vibration unit, and FIG. 2B is an overall explanatory diagram showing an example of the placement tool of FIG. 1A. [Diagram 3] 2(A) is an explanatory diagram (block diagram) showing details of the data processing unit 30 of the flaw detection system of FIG. 1, (B) is a schematic side view of the test material showing an example of a change in the vibration position of FIG. 2(A), and (C) is a schematic plan view of (B). [Figure 4] FIG. 2 is an explanatory diagram showing the operation flow of the flaw detection system of FIG. 1. [Diagram 5] FIG. 2 is an explanatory diagram showing the concept of data processing acquired by the flaw detection system of FIG. 1. [Figure 6] FIG. 4 is an explanatory diagram (block diagram) showing the main parts (data storage parts) of the data processing unit in FIG. [Figure 7] FIG. 11 is an explanatory diagram showing an operation flow of a flaw detection system according to another embodiment. [Figure 8]FIG. 11 is an explanatory diagram (block diagram) showing details of a data processing unit 30 according to still another embodiment. [Figure 9] FIG. 10 is an explanatory diagram showing an example of a data storage portion based on average difference data of the main portion (data storage portion based on average difference data) of FIG. 9; [Figure 10] (A) is an explanatory diagram of an image (difference distribution data, i.e., distribution of temperature change) showing the state of temperature change due to vibration of a test material (acrylic plate) without internal defects (internal defects), and (B) is an explanatory diagram of an image showing the state of temperature change due to vibration of a test material (acrylic plate) with an internal defect (defective part). [Figure 11] 2A to 2I are explanatory diagrams of images (difference distribution data, i.e., distribution data of the amount of temperature change) showing the state of temperature change obtained by vibrating a test material (acrylic plate) at vibration positions k1 to k9 in FIG. 2A, respectively. [Figure 12] 11(A) is an explanatory diagram showing the concept of the process of averaging the image data of FIGS. 11(A) to (I), (B) is an explanatory diagram showing an image of average difference data, i.e., average change amount distribution data, obtained from the image data of (A), and (C) is an explanatory diagram showing a thermography obtained by excitation at vibration position k5 in FIG. 2(A) shown as 50 in (A) and FIG. 12. [Figure 13] (A) is an explanatory diagram of differential distribution data acquired at an ultrasonic frequency of 20 kHz, (B) is an explanatory diagram of differential distribution data acquired at an ultrasonic frequency of 28 kHz, (C) is an explanatory diagram of differential distribution data acquired at an ultrasonic frequency of 39 kHz, and (D) is an explanatory diagram of an image of average change amount distribution data obtained by averaging (A) to (C). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Summary of the Invention) The present invention examines internal defects such as defects in test materials that are inspected using metallic materials, plastics, composite materials including CFRP (carbon fiber reinforced plastic), ceramics, concrete, and other materials, and heats the test material by directly applying ultrasonic vibrations to the test material to vibrate it, and observes the changes in heat conducted within the test material caused by the heating.In this observation, the aim is to avoid the reflection of standing waves in the observed image, which can hinder the detection of internal defects. Although the details of the mechanism for suppressing the reflection of standing waves have not been fully elucidated, the present invention was completed based on the inventor's groundbreaking discovery and provides remarkable effects with reproducibility.

[0013] (System Configuration) A preferred system configuration of the present invention will now be described. This flaw detection system is a system for reducing heat generation caused by standing waves in ultrasonically excited thermography nondestructive testing, and includes an excitation unit 1, an imaging unit 2, a computer 3, and a placement tool 4 (FIGS. 1 and 2(B)). The vibration unit 1 applies ultrasonic vibration to the test material m by bringing the vibration unit 12 into contact with the test material m, thereby heating internal defects in the test material m. The photographing unit 2 can continuously photograph two or more frames of thermography of the surface of the test material, that is, temperature distribution data that can be converted into image data that visualizes the temperature distribution on the surface of the test material m. In this example, the visualized image data is data that can be observed on a monitor (display) as an image color-coded for each temperature range. The conversion of the visualized data into image data that can be observed by an operator on a monitor may be performed by the photographing unit 2 (the thermal detection unit 21 described below), or, as in this example, may be performed by an internal defect clarification mechanism (described below) (a computer 3 having a flaw detection program installed therein). The configuration of each part will be specifically described below.

[0014] (Excitation part 1) The vibration section 1 includes a vibration exciter 11, the vibration section 12 which receives vibration voltage from the vibration exciter 11 and generates ultrasonic vibrations to vibrate the test material m, a pressure machine 13 which supports the vibration section 12 and presses it against the test material m, and a mounting table 14 on which the test material m is placed (Figure 1(B)). The pressurizer 13 is provided on the mounting table 14. The pressurizer 13 presses the vibration part 12 against the test material m on the mounting table 14 as described above, thereby applying pressure to the test material m with the vibration part 12.

[0015] The vibration section 12 is composed of a vibrator and a horn. The vibrator 11 is an oscillator (generator) that vibrates the vibrator. The electric signal amplified by the vibrator 11 is transmitted from the vibrator 11 to the vibrator, which is a converter, and converted into mechanical vibration energy. That is, the vibrator to which the vibration voltage is sent by the vibrator 11 converts electric energy into mechanical vibration energy, and at the same time, a pressure is applied by the pressure machine 13, thereby generating strong frictional heat at the internal defects of the test material m. In the excitation, the ultrasonic vibration frequency of the transducer is 10 KHz or more, preferably 15 kHz or more, more preferably 15 kHz to 200 kHz, and further preferably 20 kHz to 100 kHz.

[0016] In this example, the vibrator to which the 28 kHz electrical signal is applied by the oscillator literally vibrates 280,000 times per second, and the vibration energy is transmitted to the test material through the horn (resonator) as described above.

[0017] A commercially available ultrasonic welder (ultrasonic welding machine) used for ultrasonic welding of thermoplastic resins can be used for the vibration unit 1 (FIG. 1(B)). The vibration unit 12 includes an electrostrictive ultrasonic transducer (electrostrictive transducer) that expands and contracts when a voltage is applied as the transducer. Specifically, a BL transducer (BLT transducer / bolt-tightened Langevin transducer) is used as the transducer, and the horn is attached to the BL transducer. The vibration energy of the vibration generated by the BL transducer is transmitted to the test material m through a resonator called the horn. As for the above-mentioned horn, for example, one may be adopted which is composed of a fixed horn (booster) which is attached to the BL vibrator to increase the amplitude of the BL vibrator, and a tool horn which is attached to the fixed horn and pressed against the test material m to transmit the vibration of the fixed horn to the test material m.

[0018] The electrostrictive vibrator is made of lead zirconate titanate (PZT), which vibrates when an AC voltage is applied. The BL vibrator is a vibrator developed for low frequencies using PZT. When the test material m is resin, the time until heat is generated due to an internal defect varies depending on the material of the resin and the distance to the internal defect, but is usually less than one second. Incidentally, if it is possible to appropriately vibrate the test material, a vibrator other than the BL vibrator, such as a magnetostrictive vibrator, may be used.

[0019] In this example, the ultrasonic welder used in the vibration unit 1 first converts a 50 / 60Hz electrical signal into a 28kHz electrical signal by the oscillator. The input voltage is generally AC 200v to 240v, but it is amplified to nearly 1000v inside the oscillator and transmitted to the transducer 12. However, as long as appropriate vibration is possible, the above numerical values ​​can be changed. The electric signal converted by the oscillator is not limited to the above 28 kHz, and usually differs depending on the ultrasonic fusion machine used. Corresponding to the ultrasonic vibration frequency of the vibrator, the electric signal converted by the oscillator is 10 KHz or more, preferably 15 kHz or more, more preferably 15 kHz to 200 kHz, and further preferably 20 kHz to 100 kHz.

[0020] The vibration unit 12 applies vibration to a plurality of points on the surface of the test material m. That is, the plurality of points on the surface of the test material m are set as vibration positions, and the test material m is vibrated by ultrasonic vibration of the transducer m. In this example, the position of one vibration unit 12 is changed in sequence to vibrate the test material m at multiple vibration positions t. However, multiple vibration units 12 may be used, and the arrangement positions (vibration positions) of the vibration units 12 may be changed in sequence to perform the above vibration.

[0021] An example of the vibration position t is shown in Fig. 2(A). In the example of Fig. 2(A), a rectangular plate-like body in a plan view is used as a test material m. There are no particular limitations on the shape and dimensions of the test material m, as long as the temperature change caused by the internal defect can be detected by thermography. In the actual identification of defective products, even items with complex shapes such as gears (e.g., sintered metal gears) can be used as test materials m to check for internal defects.

[0022] In the example shown in Fig. 2(A) above, multiple vibration positions k are set at equal intervals on a straight line (virtual line) L. In this example, vibration is applied in a state where the vibration unit 12 (the horn at the tip of the vibration unit 12) is pressed vertically against the upper surface (front surface) of a rectangular plate-shaped test material m. Each vibration position k is on a straight line L (virtual line) parallel to one side (side c1c2) of the plate surface of the rectangular test material m having vertices c1 to c4. For convenience of explanation, the direction in which the straight line L extends is defined as the x direction. In addition, in the example of Figure 2 (A), the vibration positions k are nine points k1 to k9 arranged at equal intervals, but the vibration positions k are not limited to nine points, and other numbers and arrangements of the vibration positions k can be adopted depending on the dimensions and shape of the test material m as long as internal defects can be clearly identified.

[0023] The straight line is not limited to the line along the edge (one side) of the test material m, as long as it can relatively reduce the reflection of the standing wave on the thermograph for the internal defect. Note that "relatively" here means not only to highlight the internal defect against the standing wave, but also to not make the standing wave stand out against the internal defect. In addition, the vibration positions k may be set in multiple rows, not limited to the single row, within a range that does not impede imaging by the heat sensing unit 21, and the vibration positions k may be distributed, not limited to a straight line. The vibration positions k may be set in accordance with the shape of the test material m so that the standing waves are relatively inconspicuous.

[0024] Incidentally, the vibration position k is not limited to the above-mentioned one in which the vibration unit 12 is brought into vertical contact with the upper surface (plate surface) of the plate-shaped test material m, i.e., the vibration unit 12 is oriented in the thickness direction of the test material m. For example, as shown in Fig. 3(B)(C), a plurality of vibration positions k may be set on the end surface of the plate-shaped test material m, i.e., the vibration unit 12 may be oriented in a direction parallel to the plate surface, and the vibration unit 12 may be brought into vertical contact with the end surface to perform vibration.

[0025] The distance m4 between adjacent vibration positions k need only be such that it is possible to relatively reduce the reflection of standing waves on the thermograph due to internal defects. The vibration positions k can be set at appropriate positions where the above-mentioned reduction can be confirmed according to the material, dimensions, and shape of the test material m through preliminary testing using a test piece with an artificial defect.

[0026] Ideally, the vibration exciter 11 should be able to change the position of the vibration unit 12 (the horn) relative to the mounting table 14 (test material m) in horizontal directions such as left-right and front-back. That is, it is desirable that the pressure unit 13 has a movable part that moves back-and-forth or left-right (along the straight line L) as the positioning tool 4, and the vibration unit 12 is held on the movable part, so that the position of the vibration unit 12 can be changed for each shooting. Alternatively, the mounting table 14 may be able to change its position relative to the vibration unit 12 and pressure unit 13, in the opposite manner to the above. On the other hand, when using a ready-made ultrasonic welder, the pressure applying unit 13 does not have the movable unit that moves back and forth or left and right, and the position of the mounting table 14 cannot be changed relative to the vibration unit 12. Taking the above points into consideration, the placement tool 4 will be described next.

[0027] (Placement tool 4) The placement tool 4 places the vibration unit 12 at the vibration position on the surface of the test material m, making it possible for the vibration unit 12 to vibrate the test material m at each of a plurality of different vibration positions. In the case where the position of the transducer 13 can be changed by horizontally moving the pressure unit 13 or the mounting table 14 , the pressure unit 13 and the mounting table 14 constitute the placement tool 4 . On the other hand, in the case where the pressure section 13 and the mounting table 14 in the vibration section 1 cannot move the vibration section 12 relative to the test material m as described above, the positioning tool 4 can be formed separately from the vibration section 1 (mounting table 14), and the test material m can be moved relative to the vibration section 12 by moving the positioning tool 4 on which the test material m is mounted, thereby changing the vibration position.

[0028] When the placement tool 4 is separate from the vibration unit 1 (mounting table 14), the placement tool 4 can be a plate-like member, i.e., a table (mounting plate), provided on the mounting table 14 of the vibration unit 1 (in this example, the ultrasonic welder shown in FIG. 1(B)) and interposed between the mounting table 14 and the test material m, and the test material m is placed on the placement tool 4 placed on the mounting table 14 (FIG. 2(B)). The plate-like placement tool 4 is one that has enough strength not to be deformed or broken by the vibration of the test material m by the vibration unit 12. Furthermore, if necessary, the test material m may be fixed to the placement fixture 4 using a fixing jig such as a vice, such as a C-clamp, so that the position (vibration position) of the test material m relative to the vibration unit 12 does not change due to vibration during excitation.

[0029] When one shooting, i.e., one continuous shooting with the vibration position fixed, is completed, the operator grasps the positioning tool 4 and shifts the position of the positioning tool 4 relative to the mounting table 14 as described above, thereby changing the vibration position and taking the next shooting. In the example of Fig. 2(A), when shooting at vibration position k1 is completed, the vibration unit 12 is placed at vibration position k2 to take the next shooting, and when shooting at vibration position k2 is completed, the vibration unit 12 is placed at vibration position k3 to take the next shooting, and so on, in such a way that the vibration unit 12 is displaced sequentially between adjacent vibration positions k for each shooting. When the vibration position k is set on a straight line as shown in FIG. 2(A), the placement tool 4 (table) is shifted in one direction (x direction) relative to the vibration unit 12. In this example, in which the position of the vibration part 12 is changed to multiple vibration positions in sequence to perform vibration, the placement tool 4, together with the computer 3 having a flaw detection program installed therein, constitutes an internal defect clarification mechanism that clarifies internal defects in the test material m.

[0030] (Photography section 2) The photographing unit 2 includes a heat detecting unit 21 such as a heat detecting camera, and a support 22 that supports the heat detecting unit 21 (FIG. 2(B)). When a thermal camera is used as the thermal sensing unit 21, a well-known thermal camera having a plurality of elements that sense infrared rays or far-infrared rays can be used. In this example, an infrared camera that senses infrared rays is used as the thermal sensing camera. However, the thermal sensing unit 21 is not limited to an infrared camera (thermal sensing camera) as long as it can capture the temperature distribution image of the surface of the test material, and a line sensor that can sense infrared rays or a single sensor that can sense infrared rays can be used as the thermal sensing unit 21. The line sensor is a linear arrangement of a plurality of sensors that sense infrared rays, and one frame of temperature distribution data can be obtained by scanning the line sensor. The scanning includes not only linear movement of the line sensor, but also rotation (swinging). When the single sensor is used as the thermal sensing unit 21, the single sensor scans to cover two dimensions (area), that is, back and forth and left and right (or vertical and horizontal), to obtain one frame of temperature distribution data. In this embodiment, an example in which an infrared camera is used as the heat detecting section 21 will be described (hereinafter, the heat detecting section 21 will be referred to as the infrared camera 21 as necessary).

[0031] Specifically, the infrared camera 21 includes an infrared imaging element, i.e., an imaging element using an infrared sensor. The infrared imaging element of the infrared camera 21 is a surface type (area sensor). In the infrared camera 21, a plurality of elements (infrared imaging elements) that sense infrared rays are arranged two-dimensionally, and each of the plurality of elements detects temperature to obtain temperature distribution data that can be displayed as a thermograph (thermal image) in different colors depending on the temperature. In the present invention, the temperature distribution data acquired by imaging with the infrared camera 21 indicates the temperature distribution on the surface of the test material m, and the temperature at each position on the surface of the test material m can be displayed as one (one frame) planar image. The infrared camera 21 acquires the temperature distribution data, which can be displayed by color-coding the temperature for each pixel (described later).

[0032] In addition, the infrared camera 21 acquires a plurality of pieces of time-series data of the planar images (temperature distribution data) at a constant time interval (frame rate), i.e., at a constant number of frames per unit time, in one shooting. In the present invention, without changing the position of the infrared camera 21 with respect to the test material m, the positioning tool 4 is used to perform a plurality of shootings for each vibration applied by the transducer 12 at a plurality of positions (vibration positions), and a plurality of sets of time-series data of the temperature distribution are acquired for each vibration position.

[0033] The infrared camera 21 used herein is one that converts captured temperature distribution data directly into the visualized image data, i.e., thermography. However, the conversion of temperature distribution data into thermography may be performed exclusively on the computer 3 side. In this example, the thermal detection camera (infrared camera 21) is of uncooled thermography type, has a frame rate of 60Hz, a pixel count of 320 x 240 = 76,800 pixels, a NETD (thermal resolution / sensitivity) of 0.05°C, a wavelength of 7.5 to 13um, a temperature measurement range selectable from -20 to 120°C, 0 to 350°C, and 200 to 1200°C, and a measurement accuracy of + / -2°C or 2%, whichever is greater. However, the frame rate, number of pixels, NETD, and wavelength may each take a value larger or smaller than the above within a practical range.

[0034] By changing the position of the infrared camera 21 of the photographing unit 2 in accordance with the change in the position of the placement tool 4, i.e., the test material m (change in the vibration position), the relative position with respect to the test material m is made constant in each photographing. The support tool 22 may be any tool that supports the infrared camera 21 so that the position of the infrared camera 21 can be changed. The infrared camera 21 is placed at a position where the image capturing is not hindered by the transducer 12 using the support 22. The position of the infrared camera 21, i.e., the image capturing position, is preferably a position where the center of the surface of the test material m in a plan view is overlooked from above the test material m.

[0035] In the example of FIG. 2(A), the optical axis of the infrared camera 21 is aligned with the center of the test material m, for example, the intersection o of a pair of diagonals (diagonals c1c3 and c2c4) of the test material m which is rectangular in plan view. When the optical axis passes through the intersection point o, it is not limited to placing the infrared camera 21 directly above the intersection point o, but it is preferable that the optical axis passes through the center of the observation area of ​​the test material m while being perpendicular or nearly perpendicular to the surface of the test material m. Furthermore, when the test material m has a shape other than a rectangle, the center of gravity is set as the center o, and the photographing position is set in the same manner as when the test material m is rectangular.

[0036] A well-known camera support such as a tripod may be used as the support 22 (FIG. 2(B)). Each time the excitation position is changed, the tripod is moved on the floor g in the same direction and by the same distance as the displacement of the transducer 12 relative to the test material m, and the relative position of the infrared camera 21 relative to the test material m is kept constant as described above for each excitation at different excitation positions. Regarding the movement (alignment) of the infrared camera 21 in response to the change in the vibration position of the test material m, the infrared camera 21 can be moved by measuring the amount and direction of movement associated with the above change using an encoder or a laser distance meter. Further, the infrared camera 21 may be moved as described above by using a robot arm or a manipulator to make the infrared camera 21 follow the change in the vibration position of the test material m.

[0037] (Computer 3) The computer 3 is equipped with a control device, a calculation device, and a memory device (internal memory device and / or external memory device), and by introducing (installing) a flaw detection program, it constitutes a major part of the flaw detection system of the present invention as a flaw detection device in cooperation with the flaw detection program.

[0038] The above computer 3 may be a flaw detection device manufactured specifically for flaw detection and with the flaw detection program installed from the beginning, but it may also be implemented by adopting a commercially available computer with a general-purpose operating system installed and installing the flaw detection program as an application. The flaw detection program may also be installed on the cloud (on a server connected to a wide area network such as the Internet) and the flaw detection program on the cloud may be accessed. When the above cloud is used, a part of the computer 3 is assumed to be extended on the cloud.

[0039] The infrared camera 21 of the photographing unit 2 is an input device (image data input device) connected to the computer 3. The infrared camera 21 inputs captured temperature distribution data that can be displayed as a thermograph to the computer 3. Although not shown in the figure, operating devices such as a keyboard and a mouse are connected to the computer 3 as the other input devices (command input devices) mentioned above.

[0040] In addition, a monitor (display 31) and a printer (printing device, not shown) are connected as output devices to the computer 3. In addition, a disk drive or a USB memory that records data on a portable medium that stores data may also be connected to the computer 3 as an output device via a well-known interface.

[0041] A data processing unit 30, a control unit 31, an input unit 32, and an output unit 33 are constructed by a computer 3 having the above-mentioned flaw detection program installed therein (FIG. 3(A)). In this example, the data processing section 31, the control section 32 and the output section 33 are the main parts of the internal failure clarification mechanism described above (internal failure clarification processing section), and together with the placement tool 4, constitute the internal failure clarification mechanism.

[0042] The output unit 32 is primarily a connection port of a connector capable of outputting data to the output device. The data processing unit 31 includes a temperature distribution data storage unit 34, an arithmetic processing unit 35, a differential distribution data storage unit 36, and an average differential data storage unit 37 (FIG. 3(A)). The temperature distribution data storage unit 34, the differential distribution data storage unit 36, and the average differential data storage unit 37 are each mainly constructed by the memory device and the flaw detection program, the control unit 32 is mainly constructed by the control device and the flaw detection program, and the calculation processing unit 35 is mainly constructed by the calculation device and the flaw detection program. The flow of the flaw detection method of the present invention shown in FIG. 4 will be described below, along with details of the data processing unit 30.

[0043] (Flow of the flaw detection method according to the present invention) First, the transducer 12 is fixed to the vibration position k (k1 in the example of FIG. 2A) on the surface of the test material m where vibration is to be first performed, and the surface of the test material m is photographed by the infrared camera 21 (thermal sensing unit 21) (Step 1). The multiple thermographs of the time series taken as described above (temperature distribution data that can be converted and displayed) are automatically saved in computer 3 (Step 2). In each of the photographing for each vibration at each vibration position, multiple frames of temperature distribution data are photographed. In each of the photographing for each vibration, for example, 100 frames of temperature distribution data are continuously photographed. The temperature distribution data for each frame is still image data.

[0044] After one vibration is completed, the computer 3 subtracts (subtracts) the initial temperature distribution data (temperature value data for each pixel in the first frame) from each pixel (temperature value data) of the temperature distribution data stored in the computer 3 above to create temperature rise image data (distribution data of the amount of temperature change), i.e., differential distribution data (Step 3). The above Steps 1 to 3 are repeated every time the vibration position (n locations) is changed. In the example of Fig. 2(A), the above Steps 1 to 3 are repeated nine times (n=9) (three times in the example of Fig. 6). The temperature distribution data from the second frame onwards is thermal image data of the heat accumulation portion due to the standing waves taken after excitation.

[0045] In Step 2, the temperature distribution data storage unit 34, under the control of the control unit 32, stores the temperature distribution data input from the infrared camera 21 (thermal detection unit 21) in association with identification data that identifies the elapsed time from the start of shooting (Figures 5 and 6). In this example, the identification data is ordinal data that can identify the time series of the photographed data input in one continuous photographing with the vibration position fixed. Specifically, the identification data may be frame number data (ordinal data) that can identify the frame in which the temperature distribution data was photographed, such as temperature distribution data in the first frame p1, temperature distribution data in the second frame p2, etc., in the photographing (input) order. Also, instead of indirectly associating the elapsed time from vibration with the temperature distribution data as in the frame ordinal data, the elapsed time information (time code) from vibration may be directly associated with each frame (temperature distribution data) as the above identification data, and the temperature distribution data may be stored in the temperature distribution data storage unit 34.

[0046] In Step 2, the temperature distribution data storage unit 34 stores a plurality of sets of the above-mentioned time-series temperature distribution data captured and input by the infrared camera 21 (thermal detection unit 21) for each vibration position k (FIG. 2(A)). That is, the temperature distribution data storage unit 34 stores a plurality of time-series temperature distribution data in each set in association with an identifier (identification data) that identifies the vibration position k. In the example of FIG. 2(A), nine sets of time-series temperature distribution data obtained by applying vibration at vibration positions k1 to k9 are stored. In order to avoid complication, FIG. 6 shows three vibration positions (identifiers s, t, u), but in actual flaw detection, the vibration positions can be set to three positions according to the material m to be tested. Of course, in the implementation of the present invention, the vibration positions are not limited to the above three or nine positions, and the vibration positions can be set to two positions, any of four to eight positions, or any of ten positions or more according to the actual material m to be tested. For the clarification of defects, a more significant effect can be obtained by setting three or more vibration positions.

[0047] Assuming that the vibration position k is the above three positions, and touching upon the data flow in the data processing unit 30, in Step 2, the temperature distribution data storage unit 34 stores a plurality of (n frames) of time-series temperature distribution data s1 to sn acquired from one of the vibration positions as data of a first data set s, and stores the data in association with identifiers (set identification data s and frame identification data pk shown in FIG. 6; k is an arbitrary natural number) so that the set and frame can be identified.

[0048] Then, by repeating Steps 1 to 3 described above, the temperature distribution data storage unit 34 stores a plurality (n frames) of time-series temperature distribution data t1 to tn acquired from another one of the vibration positions as data of a second data set t, and associates the set and the frame with their respective identifiers (the set identification data t and the frame identification data pk;k shown in FIG. 6 are any natural numbers) so as to be able to identify the set and the frame, and further, the temperature distribution data storage unit 34 stores a plurality (n frames) of time-series temperature distribution data u1 to un acquired from yet another (remaining) one of the vibration positions as data of a third data set u, and associates the set and the frame with their respective identifiers (the set identification data u and the frame identification data pk;k shown in FIG. 6 are any natural numbers) so as to be able to identify the set and the frame.

[0049] More specifically, when the photographing at the first vibration position is completed (Step 1) and the plurality of temperature distribution data s1 to sn in the set s are stored in the temperature distribution data storage unit 34 (Step 2), the calculation processing unit 35, under the control of the control unit 31, refers to the temperature distribution data storage unit 34 and sets the still image data s1 of the first frame p1 in the set s as the initial temperature distribution data, and calculates the difference (sk-s1=Sk) from the initial temperature distribution data for each of the subsequent still image data, i.e., each still image data s2 to sn from the second frame p2 onwards, that is, the distribution data of the temperature change amount (Step 3). Note that k in sk is a natural number including 1, and in this example, the data s1 of the first frame p1 is also the subject of the difference along with each still image data s2 to sn from the second frame p2 onwards, and the distribution data (s1-s1)=S1 with the difference temperature change amount 0 is set as the difference from the data of the first frame p1 itself and is used as the reference data of the temperature change amount (distribution). The arithmetic processing unit 35 stores each of the calculation results S1 to Sn as differential distribution data, i.e., distribution data of temperature change amounts, in the differential distribution data storage unit 36. Under the control of the control unit 32, when storing the differential distribution data (distribution data of temperature change amounts) in the differential distribution data storage unit 36, the arithmetic processing unit 35 associates the differential distribution data (distribution data of temperature change amounts) of the set s with an identifier (identification data / ss shown in FIG. 6) that identifies the differential distribution data (distribution data of temperature change amounts) and also associates it with ordinal data P1 to Pn-1 that indicate a time series.

[0050] When the photographing at the next vibration position is completed (Step 1) and the plurality of temperature distribution data t1 to tn in the set t are stored in the temperature distribution data storage unit 34, the calculation processing unit 35, under the control of the control unit 31, refers to the temperature distribution data storage unit 34 and sets the still image data s1 of the first frame p1 in the set t as the initial temperature distribution data, and calculates the difference (tk-t1=Tk) from the initial temperature distribution data for each of the subsequent still image data, i.e., each still image data t2 to tn from the second frame p2 onwards, that is, the distribution data of the temperature change amount (Step 3). As above, k of tk is a natural number including 1, and in this example, the data t1 of the first frame p1 is also the object of the difference along with each still image data t2 to tn from the second frame p2 onwards, and the distribution data (t1-t1)=T1 with the difference temperature change amount 0 is set as the difference with the data of the first frame p1 itself and is used as the reference data of the temperature change amount (distribution). The arithmetic processing unit 35 stores each of the calculation results T1 to Tn as differential distribution data, i.e., distribution data of temperature change amounts, in the differential distribution data storage unit 36. Under the control of the control unit 32, when storing the differential distribution data (distribution data of temperature change amounts) in the differential distribution data storage unit 36, the arithmetic processing unit 35 associates the differential distribution data (distribution data of temperature change amounts) of set t with an identifier (identification data / tt shown in FIG. 6) that identifies the differential distribution data (distribution data of temperature change amounts) and also associates it with ordinal data P1 to Pn-1 that indicate a time series.

[0051] Furthermore, when the photographing at the next vibration position is completed (Step 1) and the plurality of temperature distribution data u1 to tn in the set u are stored in the temperature distribution data storage unit 34, the calculation processing unit 35, under the control of the control unit 31, refers to the temperature distribution data storage unit 34 and sets the still image data u1 of the first frame p1 in the set u as the initial temperature distribution data, and calculates the difference (uk-u1=Uk) from the initial temperature distribution data for each of the subsequent still image data, i.e., each still image data u2 to un from the second frame p2 onwards, that is, the distribution data of the temperature change amount (Step 3). As above, k in uk is a natural number including 1, and in this example, the data u1 of the first frame p1 is also the subject of the difference along with each still image data u2 to un from the second frame p2 onwards, and the distribution data (u1-u1)=U1 with the difference temperature change amount 0 is set as the difference with the data of the first frame p1 itself and is used as the reference data of the temperature change amount (distribution). The arithmetic processing unit 35 stores each of the calculation results U1 to Un as differential distribution data, i.e., distribution data of temperature change amounts, in the differential distribution data storage unit 36. Under the control of the control unit 32, when storing the differential distribution data (distribution data of temperature change amounts) in the differential distribution data storage unit 36, the arithmetic processing unit 35 associates the differential distribution data (distribution data of temperature change amounts) of set u with an identifier (identification data / uu shown in FIG. 6) that identifies the differential distribution data (distribution data of temperature change amounts) and also associates it with ordinal number data P1 to Pn-1 that indicate a time series.

[0052] Regarding the start of imaging by the imaging unit 2 (infrared camera 12) at each of the vibration excitation positions, the elapsed time from vibration excitation is unified (synchronized) between imaging at each vibration excitation position. In this example, the start of imaging at each vibration position (taking the first frame) is simultaneous with the vibration, i.e., the elapsed time from the start of vibration is 0 for each vibration position. However, if the timing of the start of imaging at each vibration position is aligned (synchronized), it is also possible to start imaging before vibration is applied by the imaging unit 2, i.e., take the first frame before vibration is applied (this can be considered as the same negative time elapsed from the start of vibration for imaging at each vibration position). In the claims, the "predetermined time" in "a predetermined time before the start of vibration" does not refer to a specific time difference between the start of shooting and the start of vibration, but rather means that the time difference between the start of shooting and the start of vibration is the same between shooting at each vibration position, in other words, the timing of the start of shooting is aligned. Furthermore, due to the generation of standing waves caused by vibration, the test material m begins to rise in temperature (from the room temperature state before vibration), but there is a slight time lag between the vibration and the generation of standing waves. For this reason, for each of the imaging performed before the start of vibration and simultaneously with the start of vibration, the room temperature state before the temperature rise is used as the data of the first frame (base data of the amount of temperature change, i.e., the reference data). On the other hand, the temperature distribution data from the second frame onwards is thermal image data of the heat accumulation portion due to the standing wave. Although not shown in the figure, in this embodiment, the data processing unit 30 includes a positional deviation detection unit and a correction processing unit. The positional deviation detection unit detects a positional deviation between the difference distribution data (distribution data of temperature change amount) of the corresponding frames by referring to the first difference data set ss, the second difference data set tt, and the third data set uu in the difference distribution data storage unit 36 ​​(Step 4). Specifically, the positional deviation detection unit detects a positional deviation of the test material between the difference distribution data (distribution data of temperature change amount) of the corresponding frames between the above-mentioned sets, using a characteristic point such as an edge or vertex of the test material m as a reference (reference position). That is, the above-mentioned position of the test material in the difference distribution data (distribution data of temperature change amount) of each frame of the first difference data set ss is used as a reference, and the deviation of the above-mentioned position of the test material in the temperature distribution data (distribution data of temperature change amount) of the corresponding frames of the second difference data set tt and the third difference data set uu relative to the reference is detected.

[0053] When the position shift detection unit detects a shift of the reference position of the test material in the difference distribution data (distribution data of temperature change amount) of the corresponding frames of the second difference data set tt and the third difference data set uu relative to the reference position of the test material in the difference distribution data (distribution data of temperature change amount) of each frame of the first difference data set ss, the correction processing unit performs (image) processing such as movement, rotation, enlargement, reduction, etc., i.e., correction, on the difference distribution data (distribution data of temperature change amount) to eliminate the shift (Step 5). Each difference distribution data (distribution data of temperature change amount) in the difference distribution data storage unit 36 ​​is overwritten (updated) with the difference distribution data (distribution data of temperature change amount) for which the correction has been completed. However, instead of updating the difference distribution data (distribution data of temperature change amount) before correction, the correction processing unit may store the difference distribution data (distribution data of temperature change amount) after correction in a separate difference distribution data storage unit 36 ​​or a dedicated data storage unit (not shown).

[0054] In addition, the calculation processing unit 35 may function as both the position deviation detection unit and the correction processing unit, or the data processing unit 30 may be provided with the position deviation detection unit and the correction processing unit separately from the calculation processing unit 35.

[0055] If no position shift is detected by the position shift detection unit in Step 4, or if correction is completed in Step 5, the control unit 31 causes the calculation processing unit 35 to refer to the difference distribution data storage unit 36 ​​to calculate the average data of the difference distribution data (distribution data of temperature change amount) of corresponding frames without position shift or for which the position shift has been corrected between the above-mentioned pairs, and stores the average difference data (average change amount distribution data) in the average difference data storage unit 37 (Step 6).

[0056] More specifically, in Step 6, under the control of the control unit 31, the calculation processing unit 35 refers to the difference distribution data storage unit 36, and adds and averages the difference distribution data (distribution data of temperature change amount) corresponding to the elapsed time from the start of shooting from each of the above sets ss, tt, uu. That is, the sum obtained by adding the difference distribution data (distribution data of temperature change amount) corresponding to the elapsed time from the start of shooting from each of the above sets ss, tt, uu is divided by the number of sets (the number of vibration positions k). In this example, the sum is divided by the number of sets, 3. The calculation processing unit 35 stores each of the calculated average results W1 to Wn in the average difference data storage unit 37 as average difference data (average change amount distribution data). The control unit 31 accepts operations by an operator from operating devices such as a keyboard and a mouse via the input unit 32, and outputs average difference data (average change amount distribution data) specified by the operator by referring to the average difference data storage unit 37 to an output device 38 such as a display or a printer via the output unit 33 (Figures 6 and 3).

[0057] The operator can check for internal defects by looking at the image (visualized average difference data, i.e., average change distribution data) output by the output device 38 and observing the average difference data (average change distribution data) with the largest temperature change, i.e., the easiest to observe. The operator can determine the presence or absence of an internal defect or identify the size and shape of the internal defect through the above observation.

[0058] In the above, the operator may observe the average difference data (average change amount distribution data) for all the acquired frames, i.e., the total average difference data (W1 to Wn), but may also observe only the data Wk of the frame that is estimated to have the largest temperature change due to an internal defect, which is known in advance using a test piece, to efficiently check for internal defects. For example, the operator may observe only the average difference data (Sn+Tn+Un) / 3 (identifier Wn) for the frame pn with the longest elapsed time from vibration application.

[0059] The operator may select average difference data (average change distribution data) suitable for checking for internal defects from the average difference data (average change distribution data) in the average difference data storage unit 37, and discriminate between internal defects. Furthermore, in the above, if only the average difference data (average change distribution data Wn) for the frame pn is observed from the beginning, only the average difference data (average change distribution data Wn) for the frame pn may be calculated by the calculation processing device 35 and stored in the average difference data storage unit 37, and this method is efficient in distinguishing defective products.

[0060] However, if inspection (detection of internal defects) is performed only on a test material m of a specific type (shape, size, material) using a vibrator 11 with a specific output, then a threshold data storage unit and a judgment unit (comparison processing unit) (not shown), as well as a judgment result data storage unit 37c shown by a dashed line in Figure 6, can be provided in the data processing unit 30, and data (threshold difference data) that serves as the threshold (temperature difference) for the discrimination from data previously obtained by testing using a test piece can be stored in the threshold data, and the control unit 31 can have the judgment unit refer to the average difference data storage unit 37 and the threshold data storage unit to compare the average difference data with the threshold difference data, store the judgment result data in the judgment result data storage unit 37c, and output it to the output device 38, thereby making it possible to automatically distinguish internal defects without the assistance of an operator.

[0061] In addition, if a large number of pairs of average difference data (average change distribution data) and judgment result data are accumulated and a trained database can be constructed using machine learning such as AI, particularly deep learning, the judgment unit may discriminate internal defects using a deep neural network algorithm. Also, the average difference data (average change distribution data) output by the computer 3 may be input to a trained computer separate from the computer 3, and only the discrimination may be performed by the trained computer.

[0062] (Example of change) As described above, the excitation position may be changed by moving (shifting) the positioning tool 14 on which the test material m is placed without moving the transducer 12, but conversely, the excitation position may be changed by moving the transducer 12 without moving the positioning tool 14. Specifically, instead of the transducer 12 shown in Fig. 1(B), an ultrasonic welder equipped with a handheld type (hand-held) transducer 12 with a grip is adopted, and the position where the transducer 12 is applied to the test material m is changed by the operator holding the transducer 12 for each image (not shown).

[0063] When using the handy type transducer 12, an operator presses the transducer 12 against the test material m at the excitation position, and instead of the embodiment in which a table (board) is used as the positioning tool 4 as shown in FIG. 2(B), the grip is the positioning tool 4, which is a component of the internal defect clarification mechanism. When moving the transducer 12 against the test material m, a tire-type excitation device having the transducer 12 inside a tire can be used (not shown) similar to the probe of a tire probe used in ultrasonic flaw detection. In this tire-type excitation device, the movement to the next excitation position after imaging can be smoothly performed by rolling the tire on the surface of the test material m.

[0064] In the above-described embodiments, the position of the transducer 12 relative to the test material m is changed for each image capture, and excitation is performed at a plurality of excitation positions. Alternatively, transducers 12 corresponding to the number of excitation positions may be prepared, and the transducers 12 may be placed at each of the excitation positions from the beginning, so that temperature distribution data at a plurality of excitation positions can be obtained in one image capture. By placing a plurality of transducers 12 at each of the excitation positions in advance and performing excitation sequentially, it is possible to reduce the inspection time by eliminating the need to move the transducers 12. Also, when the above vibration is applied simultaneously by a plurality of transducers 12, the vibration application position may be changed for each image capture, and vibration may be applied at more vibration application positions.

[0065] (Example of changes to vibration frequency) On the other hand, instead of performing the above-mentioned excitation at multiple excitation positions, excitation may be performed at a specific excitation position, imaging may be performed, and then the vibration frequency of the ultrasonic vibration of the transducer 11 may be changed without changing the excitation position to obtain multiple sets of time-series temperature distribution data for multiple types of vibration frequencies, and average difference data (average change amount distribution data) may be calculated from the difference distribution data (distribution data of temperature change amount) corresponding to the imaging start time between each set obtained by excitation at different frequencies.

[0066] In the case where the vibration frequency is changed for each vibration without changing the vibration position, for example, a plurality of sets of time-series temperature distribution data obtained from each of the vibrations performed at three different frequencies may be processed as a first data set s, a second data set t, and a third data set u shown in FIG. 6, and the data may be processed in the same manner as in the above-mentioned case. That is, although the method of acquiring the above-mentioned three sets of data is different, data processing may be performed in the same flow as the flow (FIG. 4) of the plurality of sets (three sets in this example) of time-series temperature distribution data obtained by changing the vibration position as described above (FIG. 7). Each of Steps 10 to 60 shown in FIG. 7 corresponds to each of Steps 1 to 6 shown in FIG. 4, and differs from the above-mentioned embodiment only in that Steps 10 to 30 are repeated n times, where n is the number of types of frequencies. Therefore, the configuration of the data processing unit 30 when each vibration is performed by ultrasonic vibrations with different frequencies from each other is also as shown in FIG. 6. When changing the ultrasonic vibration frequency, that is, when changing the distribution of standing waves at a plurality of vibration frequencies to make the standing waves less noticeable, the plurality of vibration frequencies to be selected may be selected from the range of 10 KHz to 500 kHz.

[0067] The frequency can be changed by preparing a plurality of excitation units 1 having different vibration frequencies and alternating the vibrators 12 that are brought into contact with the excitation units 1 at specific excitation positions. When preparing a plurality of excitation units 1, instead of alternatingly bringing each vibrator 12 into contact with a specific excitation position, a plurality of excitation positions may be set and the vibrators 12 of the excitation units 1 having different vibration frequencies may be arranged at each excitation position to perform excitation, in which case the average difference data (average change amount distribution data) is calculated by mixing the excitation at the plurality of excitation positions and the plurality of vibration frequencies. Furthermore, if the vibration exciter 11 is capable of changing the vibration frequency of the transducer 12, it is also possible for one vibration exciter 1 to perform vibration at a plurality of vibration frequencies.

[0068] In any case where the vibration frequency of the ultrasonic vibration is constant and each vibration is performed at multiple vibration positions, the vibration position is constant and the vibration frequency of the ultrasonic vibration is different for each vibration, or both the vibration position and the vibration frequency are multiple, the average difference data (average change distribution data) obtained by the above data processing may be observed to check for internal defects, but it can also be implemented by preparing a test specimen m without internal defects and a test specimen m with artificial defects, performing vibration, and grasping in advance the elapsed time from the start of shooting at which the temperature change is the largest (usually the temperature is saturated) when an internal defect exists, and checking only the average difference data (average change distribution data) corresponding to that elapsed time. When checking only the average difference data (average change distribution data) corresponding to that elapsed time, it is also possible to calculate only the average difference data (temperature change distribution data) corresponding to that elapsed time from the beginning, and obtain temperature distribution data only for frames necessary to calculate the average difference data (average change distribution data) corresponding to that elapsed time. When examining only the average difference data (average change amount distribution data) corresponding to the elapsed time, it can be said that it is sufficient to acquire only the frames of the initial temperature distribution data and the temperature distribution data for the elapsed time.

[0069] The above-mentioned temperature distribution data can be obtained by a) moving (changing) the vibration position (position where vibration is applied) or sequentially applying vibration at multiple points using multiple vibrators, and b) changing the vibration frequency (at multiple vibration frequencies), as well as c) applying vibration in combination with the above a) and b).

[0070] Furthermore, the data storage unit 37a based on average difference data can be implemented as a Fourier transform data storage unit 37a, and under the control of the control unit 31, the calculation processing unit 35 can be made to refer to the average difference data storage unit 37, perform a Fourier transform on a plurality of average difference data W1 to Wn-1 corresponding to each frame of the time series, and store the converted phase image data in the Fourier transform data storage unit 37a.

[0071] The above discrete Fourier transform will now be briefly explained. The calculation processing unit 35 performs a Fourier transform on the average difference data (data showing the relationship between time and temperature change) of multiple frames of the time series stored in the average difference data storage unit 37 to calculate data showing the relationship between phase and frequency. Since the calculated data is discrete, a discrete Fourier transform is performed, but it is also possible to perform a Fourier transform by fitting to an analytical function and performing a continuous Fourier transform. The discrete Fourier transform is performed based on the following equations 1 and 2.

[0072]

number

[0073]

number

[0074] In the above, Fn represents the conversion result (frequency component, complex intensity) at a frequency that is n times the value obtained by dividing the sampling frequency by twice the sampling number N. The difference number n explained so far corresponds to this sampling number N. The n in the above "n times" is used to distinguish it from the n in the difference number n used so far. The number of samplings N was 100 frames (N=100) of image data. However, the number of samplings may be more or less than 100 frames as long as the effect of clarifying the internal defects can be obtained.

[0075] Ren represents the real part of the conversion result, Imn represents the imaginary part of the conversion result, T is the temperature of the kth sampling, An represents the magnitude of the conversion result, and Φn represents the phase of the conversion result. In the discrete Fourier transform, the frequency range after the transformation is determined by the sampling frequency and the number of acquired data. The minimum value fmin and maximum value fmax of the transformed frequency are expressed as the following equations 3 and 4 using the sampling frequency fs and the number of acquired data N.

[0076]

number

[0077]

number

[0078] The operator uses the above-mentioned keyboard or other device to select an inspection frequency from the data showing the relationship between phase and frequency obtained by the Fourier transform, and the phase at the selected inspection frequency is displayed on the above-mentioned display, thereby visualizing the phase at each position of the test material m. The data can be visualized in a manner that represents the inspection position of the test material m on an image plane and represents the phase by saturation, color shading, etc.

[0079] When a Fourier transform is performed, as another embodiment, the relative value of the phase may be displayed. That is, by comparing the phases of the respective parts of the test material m, if the phase of a certain part of the test material m differs from the phase of the other parts of the test material m, it is possible to know that a defect exists in that certain part. The comparison of the phases of the respective parts of the test material m may be performed by an operator checking the phase displayed on the image, or the data processing unit 30 may be provided with the threshold data storage unit, the judgment unit (comparison processing unit), and the judgment result data storage unit 37c described above, and the data processing unit 30 may automatically compare the phases depending on whether the difference between the phase of the certain part of the test material m and the phase of the other parts exceeds a predetermined threshold value. EXAMPLES

[0080] (Example of multiple excitation positions) The test material m in Fig. 2(A) is an acrylic plate, the longitudinal size (m1+m2) of the test material m is 150 mm, the width size m3 is 150 mm, the thickness is 3 mm, the distance m2 from the near short side c1c2 to the center of the vibration position k is 10 mm (the distance m1 from the far short side c3c4 to the center of the vibration position k is 140 mm), and the interval m4 between the vibration positions k is 10 mm, so that the flaw detection method of the present invention can be carried out. In this embodiment, as test pieces, a test material m in Fig. 2(A) having the above dimensions was prepared, in which a plastic ball was collided with the test material m in Fig. 2(A) to generate a crack inside the test material m, thereby providing an artificial defect mk, and a test material m having the above dimensions but not providing the artificial defect mk. The maximum diameter of the artificial defect was set to 20 mm. In this embodiment, the area was set near the center o of the test material m and within the area oc3c4 in Fig. 2(A). In actual flaw detection, it is expected that the reflection of standing waves will be reduced and the defect (internal defect) will be easily observed regardless of the position inside the test material m.

[0081] As described above, when the point of excitation of the test material m is changed (when the excitation position is changed from k1 to k9 in sequence), the temperature (thermography) pattern (mottled image) on the surface of the test material m changes. That is, the locations of the antinodes and nodes of the standing waves caused by vibration in the test material m change. The nine pieces of time-series accumulated difference distribution data (10 to 90 in FIG. 11) from the temperature distribution data obtained from each of the above-mentioned multiple excitation positions k are added together (FIG. 12(A)), and the averaged average difference data is shown in FIG. 12(B). When comparing the image (average difference data image) shown in FIG. 12(B) obtained by superimposing and averaging the nine (accumulated) difference image data and the difference distribution data showing the temperature change situation obtained by excitation at the excitation position k5 in FIG. 2(A), it can be confirmed that the difference in shading of the mottled pattern caused by the standing waves is smaller in the image in FIG. 2(B) than in the image in FIG. 2(C), and the heat generation part caused by the defect is relatively more noticeable.

[0082] Specifically, the S / N ratio (standard deviation of the temperature of the healthy part relative to the temperature rise of the defective part) of the image shown in FIG. 12(B) was 24.6, and the S / N of the image shown in FIG. 12(C) was 15.6. From the images shown in Figures 12(B) and (C), it was confirmed that by applying vibrations (excitation) from multiple different vibration positions, various standing waves are generated, and by averaging the differential distribution data obtained at each excitation, internal defects can be displayed with a good S / N ratio. As described above, by obtaining data from sequentially changing the excitation point (excitation position k), it is possible to reduce the mottled pattern by averaging the temperatures (for each pixel) of the image of the mottled pattern caused by the standing wave, and since heat generation due to vibration in a defect such as a vertical crack is caused by frictional heat generation on the crack surface, it can be understood that even if the excitation position is changed, the position of heat generation due to the defect does not change, and a significant temperature difference can be confirmed even in the image after averaging. It was confirmed that by implementing the present invention, the mottled pattern caused by the standing wave is reduced and averaged, making it easier to visually confirm the defective part.

[0083] (Example of multiple vibration frequencies) Figure 13(A) shows a thermograph of temperature distribution data obtained by exciting the ultrasonic vibration of the transducer 12 at a vibration frequency of 20 kHz, while Figures 13(B) and 13(C) show thermographs of temperature distribution data obtained by exciting the ultrasonic vibration of the transducer 12 at frequencies of 28 kHz and 39 kHz, respectively, at the same exciting position as in Figure 13(A) (excitation position k5 in Figure 2, i.e., near the center of the short side c1c2 of the test material m). The example shown in Figure 13 is a thermal image of an acrylic test piece of 100 mm x 150 mm x 3 mm. The S / N ratio in the thermograph of Figure 13(A) was 3.35, the S / N ratio in the thermograph of Figure 13(B) was 2.87, and the S / N ratio in the thermograph of Figure 13(C) was 3.55. Figure 13(D) shows an image obtained by averaging the thermographs of Figures 13(A) to 13(C). The S / N ratio of the image of Figure 13(D) was 4.66. It can be seen that the standing wave heat generation distribution, i.e., the heat generation distribution caused by standing waves, remains in the averaged image shown in Figure 13(D), but there is a reduction in the standing wave heat generation distribution and a certain improvement in the S / N ratio associated with this reduction.

[0084] Therefore, for each of the multiple sets of time-series temperature distribution data obtained by excitation at each of the above frequencies, the difference (difference distribution data) between the temperature distribution data of the second frame and thereafter and the initial temperature distribution data (first frame) is taken, and the difference distribution data of corresponding frames in each of the above sets is added and averaged to obtain data (average difference data), which is obtained by taking the average from the temperature change (temperature gradient) data.This is thought to make standing waves less noticeable and therefore to make defects even more apparent. In addition, even when vibration is applied at multiple frequencies, the timing of starting imaging with each frequency of vibration is the same as when multiple vibration positions are used, and the elapsed time from vibration application is unified (synchronized) between imaging at each frequency. In this example, the start of imaging at each vibration position (taking the first frame) is performed simultaneously with the vibration in any frequency, that is, the elapsed time from the start of vibration is 0. However, if the timing of the start of imaging at each frequency is aligned (synchronized), it is possible to start imaging before the vibration is applied by the imaging unit 2, that is, to take the first frame before the vibration is applied.

[0085] (Summary) The first invention is an inspection (flaw detection) system that includes a transducer 12 that applies ultrasonic vibrations to a test material m and a vibrator 11 that excites and drives the transducer 12, an infrared camera 21 (heat detection unit 21) that measures and records the temperature of the surface of the test material m, and records the temperature of the surface of the test material m. The transducer 12 is fixed to the test material m by a mounting tool 4 and applies ultrasonic vibrations. The temperature measurement value (output image data) of the infrared camera 21 is recorded in a computer 3 together with the initial temperature (first frame) at the same time as or before the vibration application, and at least the temperature at the time when the ultrasonic vibration in the test material m after the vibration application becomes stable. The data is recorded (saved) and the data is recorded in the computer 3 equipped with a control unit 31, and then, without changing the (relative) positions of the infrared camera 21 and the test material m, the excitation point of the transducer 12 is changed to a different location on the test material m from the above, and the temperature measurement value of the infrared camera 21 is recorded (saved) in the computer 3 in the same manner as described above. The recording in the computer 3 is repeated multiple times (N times) depending on the excitation position, and the obtained N images are differentiated by the initial temperature (first frame), and then averaged for each element of each infrared detector (temperature sensing sensor) of the infrared camera 21 (for each pixel of the image) to display a new averaged image.

[0086] The second invention is an inspection system that includes a transducer 12 that applies ultrasonic vibration to a test material m, one or more transducers 12 with a different vibration frequency from the transducer 12, a vibration exciter 11 that excites each transducer 12, an infrared detection camera 3 that measures and records the temperature of the surface of the test material m, and records the temperature of the surface of the test material m. The transducer 12 is fixed to the test material m and ultrasonic vibration is applied. The temperature measurement value of the infrared camera 21 (output image data) is recorded at the time when the standing wave of the ultrasonic vibration becomes stable in the test material m at least after the vibration, together with the initial temperature (first frame) at the same time as or before the vibration. After recording the data, without changing the (relative) positions of the infrared camera 21 and the test material m, vibration is applied to the same location on the test material m using a vibrator 12 with a different vibration frequency from that of the vibrator 12, and the temperature measurement value of the infrared camera 21 is recorded (stored) in the computer 3 in the same manner as described above. The above recording is repeated multiple times (N times) depending on the vibration frequency, and the obtained N images are differentiated by the initial temperature (first frame), and then averaged for each element of the infrared detector (temperature sensing sensor) of each infrared camera 21 (for each pixel of the image) to display a new averaged image. [Explanation of symbols]

[0087] 1. Vibration section 2. Filming Department 3. Computer 4 Placement tool 11. Vibrator 12 Transducer 13 Pressurizer 14 Placement table 21 Heat sensing section 22 Supports 30 Data Processing Section 31 Control Unit 32 Input section 33 Output section 34 Temperature distribution data storage section 35 Processing unit 36 Differential distribution data storage section 37 Average differential data storage section 37a Data storage section based on average difference data 37c Judgment result data storage unit 38 Output Devices

Claims

1. A flaw detection method for detecting internal defects in the entire test material or in a specific area of ​​the test material by applying ultrasonic vibrations to the test material using a vibrating part that is in contact with the test material, heating the internal defects in the test material, and observing temperature changes in a thermography of the test material surface, i.e., an image that visualizes the temperature distribution on the test material surface, is described. The photographing position for acquiring the image and the frequency of the ultrasonic vibration are fixed for the test material, the ultrasonic vibration is applied, and two or more frames of the image are photographed at different times after the start of the photographing, the first image from the start of the photographing is set as an initial image, and a distribution of temperature change amounts relative to the initial image is calculated for other images photographed at least after the initial image, The imaging starts simultaneously with the start of the vibration or a predetermined time before the start of the vibration, Ultrasonic vibrations are applied to the test material at a plurality of mutually different vibration positions, and a plurality of the initial images and a plurality of the other images are obtained by photographing the material using ultrasonic vibrations at each of the plurality of vibration positions, the plurality of the other images are obtained after the vibrations are applied, and the plurality of the other images correspond to each other in terms of the elapsed time from the start of the photographing, A flaw detection method for detecting internal defects from a distribution of average temperature changes obtained by averaging a plurality of temperature change distributions obtained by calculating the distribution of the temperature change for each vibration position.

2. A flaw detection method as described in claim 1, wherein one or more distributions of temperature change amounts are calculated as a distribution of frequency-changed temperature change amounts from the image obtained by changing the frequency of the ultrasonic vibration and applying it at at least some of the different vibration positions on the test material, and the averaging is performed by adding each of the distributions of frequency-changed temperature change amounts.

3. A flaw detection method for detecting internal defects in the entire test material or in a specific area of ​​the test material by applying ultrasonic vibrations to the test material using a vibrating part that is in contact with the test material, heating the internal defects in the test material, and observing the temperature change using thermography of the test material surface, i.e., an image that visualizes the temperature distribution on the test material surface, is described. The photographing position for obtaining the image and the vibration position for applying the vibration are both fixed for the test material, and two or more frames of the image are photographed at different times after the start of the photographing, the first image from the start of the photographing is set as an initial image, and a distribution of temperature change amounts relative to the initial image is calculated for other images photographed at least after the initial image, The imaging starts simultaneously with the start of the vibration or a predetermined time before the start of the vibration, A flaw detection method in which ultrasonic vibrations of multiple different frequencies are applied to the test material, and multiple initial images and multiple other images are obtained by photographing each of the ultrasonic vibrations at each of the multiple different frequencies, the multiple other images are obtained after the vibration is applied, and the multiple other images obtained correspond in elapsed time from the start of the photographing, and the internal defects are examined from the distribution of average changes obtained by averaging the distribution of the temperature change amounts obtained by calculating the distribution of the temperature change amount for each frequency.

4. In each of the photographing operations in which the frequency and the vibration position are constant, a group of three or more frames of images are photographed in a time series, a distribution of the amount of temperature change of at least a plurality of the other images relative to the photographed initial image is calculated, and the plurality of distributions of the amount of temperature change in the time series are made into a set of distribution groups of the amount of temperature change; A distribution group of the temperature change amount of the plurality of sets of different vibration positions is calculated from the plurality of sets of the image group obtained by each photographing while applying the ultrasonic vibration to the test material at a plurality of different vibration positions; The flaw detection method according to claim 1 or 2, wherein, between multiple sets of temperature change distribution groups, the distributions of the multiple temperature change amounts corresponding to the elapsed time from the start of the shooting are averaged, and the internal defect is examined by observing at least one of the first observation object and the second observation object. First observation object: at least one distribution of average changes selected from the distributions of multiple average changes of the time series obtained by the averaging Second observation target: a phase image obtained by Fourier transforming the distribution of the plurality of average changes in time series

5. In each of the photographing operations in which the frequency and the vibration position are constant, a group of three or more frames of images are photographed in a time series, a distribution of the amount of temperature change of at least a plurality of the other images relative to the photographed initial image is calculated, and the plurality of distributions of the amount of temperature change in the time series are made into a set of distribution groups of the amount of temperature change; Applying ultrasonic vibrations of a plurality of different frequencies to the test material, and calculating a distribution group of the temperature change amounts of the plurality of sets of different frequencies; The flaw detection method according to claim 3, further comprising: averaging the distributions of the plurality of temperature change amounts corresponding to the elapsed time from the start of the photographing among the plurality of sets of distribution groups of the temperature change amounts; and examining the internal defects by observing at least one of the first observation object and the second observation object. First observation object: at least one distribution of average temperature change amounts selected from the distributions of multiple average changes amounts of the time series obtained by the averaging Second observation target: a phase image obtained by Fourier transforming the distribution of the plurality of average changes in time series

6. A flaw detection system comprising: a vibration unit that applies ultrasonic vibrations to the test material using a vibration unit that is in contact with the test material, thereby heating internal defects in the test material; and an image capture unit that can capture two or more frames of thermographic data of the test material surface, i.e., temperature distribution data that can be converted into image data that visualizes the temperature distribution on the test material surface, the image capture unit having a thermal detection unit such as a thermal detection camera equipped with a plurality of elements that detect infrared rays, the flaw detection system making it possible to examine internal defects in the test material from temperature changes in the temperature distribution data of the test material surface captured by the thermal detection unit, The temperature distribution data includes an internal defect clarification mechanism that suppresses the impairment of identification of the internal defect due to the reflection of a temperature change caused by a standing wave generated in the test material by the vibration, The internal defect clarification mechanism is composed of an arrangement tool that enables the imaging unit to take multiple consecutive images at different vibration positions by arranging the vibration unit at multiple different vibration positions on the surface of the test material, a data processing unit that calculates distribution data of temperature change between the two or more frames of temperature distribution data acquired by the heat sensing unit and calculates average change distribution data by averaging the multiple distribution data of temperature change calculated from the temperature distribution data acquired for the multiple vibration positions, an output unit, and a control unit, and at least the data processing unit, the output unit, and the control unit are constructed by a computer and a flaw detection program installed in the computer, The positioning tool can at least place the vibration unit in contact with the test material during the photographing, and the positioning tool can sequentially change the vibration position of the vibration unit by attaching / detaching or moving the vibration unit relative to the test material, thereby enabling the positioning at a plurality of different vibration positions, or can simultaneously position the vibration unit at a plurality of different vibration positions, The control unit starts photographing by the photographing unit simultaneously with the start of vibration by the vibration applying unit or a predetermined time before the start of vibration, The photographing unit inputs temperature distribution data acquired by the photographing in direct or indirect association with the elapsed time to the data processing unit, the control unit causes the data processing unit to calculate, as initial temperature distribution data, a distribution of temperature changes with respect to the initial temperature distribution data for other temperature distribution data captured after vibration application at least after the initial temperature distribution data, using the temperature distribution data of the first frame at the start of the imaging, which is input from the heat sensing unit to the data processing unit, as distribution data of temperature changes; Furthermore, the control unit corresponds the elapsed time from the start of the imaging between the plurality of other temperature distribution data acquired by setting the vibration positions to a plurality of positions, and causes the data processing unit to calculate an average of the plurality of temperature change amount distribution data as the average change amount distribution data, The output unit can output, in response to an operation by an operator or automatically, at least one of the average change amount distribution data, data based on the average change amount distribution data, and data related to a discrimination result of an internal defect that the control unit has caused the data processing unit to determine; The output unit of this flaw detection system is equipped with at least one of a display capable of displaying the output data to an operator, a printing device capable of printing the data, and a recording device that records the data on a recording medium that can be played back on other computers or video equipment.

7. The vibration unit can change the frequency of the ultrasonic vibration and excite at least a part of the vibration unit arranged at a plurality of different vibration positions with respect to the test material, and the control unit causes the data processing unit to calculate one or more pieces of distribution data of the temperature change amount as frequency change temperature change amount distribution data from the temperature distribution data acquired by changing and exciting the material, The flaw detection system according to claim 6 , wherein the control unit causes the data processing unit to calculate the average temperature change distribution data by adding each of the frequency change temperature change distribution data to the average.

8. A flaw detection system comprising: a vibration unit that applies ultrasonic vibrations to the test material using a vibration unit that is in contact with the test material, thereby heating internal defects in the test material; and an image capture unit that can capture two or more frames of thermographic data of the test material surface, i.e., temperature distribution data that can be converted into image data that visualizes the temperature distribution on the test material surface, the image capture unit having a thermal detection unit such as a thermal detection camera equipped with a plurality of elements that detect infrared rays, the flaw detection system making it possible to examine internal defects in the test material from temperature changes in the temperature distribution data of the test material surface captured by the thermal detection unit, The apparatus includes at least a positioning tool that can position the vibration unit in contact with the test material during the photographing, and an internal defect clarification mechanism that suppresses the impairment of identification of the internal defect due to the reflection of a temperature change caused by a standing wave generated in the test material by the vibration in the temperature distribution data, The internal defect clarification mechanism can perform the excitation with ultrasonic vibrations of different frequencies for each of the continuous photographing by changing the frequency of the ultrasonic vibration of the vibration unit, and is composed of a data processing unit that calculates distribution data of the temperature change amount between the two or more frames of temperature distribution data acquired by the heat sensing unit and calculates average change amount distribution data by averaging a plurality of the temperature change amount distribution data calculated from the temperature distribution data acquired for the plurality of photographing at the different frequencies, an output unit, and a control unit, and at least the data processing unit, the output unit, and the control unit are constructed by a computer and a flaw detection program installed in the computer, The control unit starts photographing by the photographing unit simultaneously with the start of vibration by the vibration applying unit or a predetermined time before the start of vibration, The photographing unit inputs temperature distribution data acquired by the photographing in direct or indirect association with the elapsed time to the data processing unit, the control unit causes the data processing unit to calculate, as initial temperature distribution data, a distribution of temperature changes with respect to the initial temperature distribution data for other temperature distribution data captured after vibration application at least after the initial temperature distribution data, using the temperature distribution data of the first frame at the start of the imaging, which is input from the heat sensing unit to the data processing unit, as distribution data of temperature changes; Furthermore, the control unit corresponds the elapsed time from the start of the imaging between the multiple other temperature distribution data acquired by setting the frequency to multiple, and causes the data processing unit to calculate an average of the multiple temperature change amount distribution data as the average change amount distribution data, The output unit can output, in response to an operation by an operator or automatically, at least one of the average change amount distribution data, data based on the average change amount distribution data, and data related to a discrimination result of an internal defect that the control unit has caused the data processing unit to determine; The output unit of this flaw detection system is equipped with at least one of a display capable of displaying the output data to an operator, a printing device capable of printing the data, and a recording device that records the data on a recording medium that can be played back on other computers or video equipment.

9. the photographing unit photographs a group of three or more frames of the temperature distribution data in a time series in each of the photographs performed with the frequency and the vibration position kept constant, and the control unit causes the data processing unit to calculate distribution data of a temperature change amount for at least each of the other temperature distribution data with respect to the photographed initial temperature distribution data, and to acquire the plurality of distribution data of the temperature change amount in a time series as a set of distribution data of a temperature change amount, The control unit causes the data processing unit to calculate a plurality of sets of distribution data of the temperature change amount at different vibration positions from a plurality of sets of temperature distribution data obtained by each photographing performed by applying the ultrasonic vibration to the test material at a plurality of vibration positions different from each other with respect to the test material, Among the plurality of sets of the temperature change amount distribution data group, the plurality of temperature change amount distribution data corresponding to the elapsed time from the start of the imaging are averaged to calculate the average change amount distribution data; The flaw detection system of claim 6 or 7, further comprising a control unit which is capable of outputting at least one of the following first data and second data to the output unit as data based on the average change amount distribution data, either in response to an operator's operation or automatically. First data: at least one average change amount distribution data corresponding to a predetermined elapsed time from the start of the imaging selected by an operator's operation or set in advance from a plurality of time-series average change amount distribution data obtained by the averaging Second data: Phase distribution data obtained by subjecting the plurality of time-series average change amount distribution data to Fourier transform in the data processing unit.

10. the photographing unit photographs a group of three or more frames of the temperature distribution data in a time series in each of the photographs performed with the frequency and the vibration position kept constant, and the control unit causes the data processing unit to calculate distribution data of a temperature change amount for at least each of the other temperature distribution data with respect to the photographed initial temperature distribution data, and to acquire the plurality of distribution data of the temperature change amount in a time series as a set of distribution data of a temperature change amount, The control unit causes the data processing unit to calculate a plurality of sets of distribution data of the temperature change amount having different frequencies from a plurality of sets of the temperature distribution data obtained by each photographing performed by applying the ultrasonic vibrations having a plurality of different frequencies to the test material, Among the plurality of sets of the temperature change amount distribution data group, the plurality of temperature change amount distribution data corresponding to the elapsed time from the start of the imaging are averaged to calculate the average change amount distribution data; The flaw detection system of claim 8, further comprising a control unit which, in response to an operator's operation or automatically, can output at least one of the following first data and second data to the output unit as data based on the average change amount distribution data. First data: at least one average change amount distribution data corresponding to a predetermined elapsed time from the start of the imaging selected by an operator's operation or set in advance from a plurality of time-series average change amount distribution data obtained by the averaging Second data: Phase distribution data obtained by subjecting the plurality of time-series average change amount distribution data to Fourier transform in the data processing unit.

11. The flaw detection program installed in the flaw detection system according to claim 6 .

12. The flaw detection program installed in the flaw detection system according to claim 8 .

Images