Infrared flaw detection device and method based on convective thermal metamaterial temperature field scattering resonance

Abstract

The present invention discloses an infrared flaw detection device and method based on the scattering resonance of the temperature field of a convection thermal metamaterial, and belongs to the field of infrared flaw detection technology. The present invention utilizes a time-harmonic heat source to excite a uniformly rotating convection ring structure, and places a sample ring on the upper surface of the convection ring. When the sample is defect-free, a resonance peak in the temperature field on the upper surface of the sample can be observed with the help of an infrared camera by scanning the excitation heat source; when the sample has a defect, it is excited at this frequency, and it is observed that the amplitude response of the temperature field is linearly related to the defect size. Since the device is based on the scattering resonance effect of the convection thermal metamaterial and the time-harmonic heat source, the response sensitivity of the temperature amplitude to defects can be effectively improved, and therefore it can be used to achieve high-sensitivity infrared non-destructive flaw detection.

Description

Technical Field

[0001] The present invention relates to the field of infrared flaw detection technology, and in particular to an infrared flaw detection device and method based on convective thermal metamaterial temperature field scattering resonance. Background Art

[0002] Compared with other detection technologies, infrared flaw detection has the advantages of non-contact measurement, high precision, safety, speed and convenience, and is widely used in defect detection of different materials such as metals and non-metals. For example, by using a periodic heat source to heat one side of the circuit board and using a high-precision infrared thermal imager to record the surface temperature field response of the other side of the circuit board, when the heating frequency of the heat source is high, the surface cracks of the circuit board can be quickly found, and when the heating frequency is low, the internal defects can be accurately located.

[0003] However, due to the rapid attenuation of the temperature field amplitude during spatial transmission, actual infrared flaw detection or non-destructive testing often requires relatively high temperature amplitude input or short observation distance to ensure its high sensitivity, which seriously limits the application scenarios and performance of this technology. The present invention proposes a new infrared flaw detection device based on the temperature field scattering resonance effect of convective thermal metamaterials, which can make infrared flaw detection imaging clearer to improve the sensitivity of defect detection. Summary of the invention

[0004] The purpose of the present invention is to solve the problem in the prior art that it is difficult to obtain the defect size non-destructively and accurately by infrared flaw detection, and to provide an infrared flaw detection device and method based on convective thermal metamaterial temperature field scattering resonance to achieve a high sensitivity response of the temperature field amplitude to the defect.

[0005] The technical solutions specifically adopted in the present invention are as follows:

[0006] In a first aspect, the present invention provides an infrared flaw detection device based on convective thermal metamaterial temperature field scattering resonance, which includes a driving mechanism, a convection ring, a time-harmonic excitation heat source and an infrared imaging device;

[0007] The convection ring is a homogeneous annular cross-section cylinder made of convection thermal metamaterial, and its two end faces are respectively a first end face and a second end face, wherein the first end face is used to carry the sample to be inspected in a tightly fitting manner;

[0008] The rotating driving end of the driving mechanism is connected to the convection ring, and is used to drive the convection ring to rotate at a uniform speed around the axis; and when the convection ring is driven to rotate by the driving mechanism, the sample to be inspected remains fixed and rotates asynchronously;

[0009] The time-harmonic excitation heat source is arranged on the side where the second end surface of the convection ring is located, and is used to input a time-harmonic temperature field to the second end surface of the convection ring;

[0010] The adjustable range of the angular velocity of the driving mechanism driving the convection ring to rotate and the adjustable range of the time-harmonic temperature field excitation angular frequency input by the time-harmonic excitation heat source into the convection ring overlap, and the state in which the angular velocity and the excitation angular frequency remain the same is used as the flaw detection state of the infrared flaw detection device;

[0011] The infrared imaging device is arranged on the side where the first end surface of the convection ring is located, and its imaging direction is along the axial direction of the convection ring toward the sample to be inspected, and is used to collect thermal images of the surface of the sample to be inspected.

[0012] As a preferred embodiment of the first aspect, the convection thermal metamaterial used in the convection ring is silver or copper.

[0013] As a preference of the above first aspect, the driving mechanism is a mechanical driving mechanism or an electromagnetic driving mechanism.

[0014] As a preferred embodiment of the first aspect, the time-harmonic excitation heat source is an electrically controlled semiconductor refrigeration plate attached to the first end face of the convection ring, or a laser heating device using the first end face of the convection ring as a heating surface.

[0015] As a preferred embodiment of the first aspect, the excitation temperature output by the time-harmonic excitation heat source satisfies a sinusoidal oscillation form or a cosine oscillation form.

[0016] As a preferred embodiment of the first aspect, the angular velocity of the convection ring driven by the driving mechanism to rotate is adjustable, and the angular frequency of the time-harmonic temperature field excitation input by the time-harmonic excitation heat source into the convection ring is fixed.

[0017] As a preferred embodiment of the first aspect, the angular velocity of the convection ring driven by the driving mechanism to rotate is fixed, and the angular frequency of the time-harmonic temperature field excitation input by the time-harmonic excitation heat source into the convection ring is adjustable.

[0018] As a preferred embodiment of the above-mentioned first aspect, a thermal interface material for reducing the thermal resistance between the convection ring and the sample to be inspected is coated on the first end surface of the convection ring.

[0019] In a second aspect, the present invention provides an infrared flaw detection method using the infrared flaw detection device according to any one of the schemes of the first aspect, comprising:

[0020] S1. The driving mechanism and the time-harmonic excitation heat source in the infrared flaw detection device are adjusted so that the angular velocity of the convection ring driven by the driving mechanism is the same as the angular frequency of the time-harmonic temperature field excitation input into the convection ring by the time-harmonic excitation heat source, thereby maximizing the amplitude of the temperature field outputted from the first end face of the convection ring through the resonance effect, and the infrared flaw detection device is in a flaw detection state;

[0021] S2, keeping the infrared flaw detection device in a flaw detection state, placing a non-destructive homogeneous sample of the same model as the sample to be detected on the first end face of the convection ring, and keeping the projection of the non-destructive homogeneous sample on the first end face completely located within the first end face; after the temperature field output from the surface of the non-destructive homogeneous sample is stable, the infrared imaging device collects a first thermal image of the surface of the non-destructive homogeneous sample;

[0022] S3, keeping the infrared flaw detection device in a flaw detection state, placing the sample to be detected on the first end face of the convection ring, and keeping the projection of the sample to be detected on the first end face completely within the first end face; after waiting for the temperature field output on the surface of the flaw detection sample to stabilize, the infrared imaging device collects a second thermal image of the surface of the sample to be detected;

[0023] S4. Identify all defect areas from the second thermal image based on the temperature field amplitude change, and obtain the temperature field amplitude change of each defect area from the first thermal image and the second thermal image, and then convert the temperature field amplitude change of each defect area into an equivalent thermal diffusivity change according to a pre-calibrated linear relationship, and then substitute the equivalent thermal diffusivity change of each defect area into the Maxwell-Garnett formula to calculate the volume ratio of each defect area in the sample to be inspected, so as to quantitatively determine the defect size of each defect area in the sample to be inspected.

[0024] As a preferred embodiment of the above-mentioned second aspect, for each defect area in the sample to be inspected, it is necessary to obtain the temperature field amplitude change corresponding to each thermal image pixel in the area, and then calculate the volume ratio of each thermal image pixel in the sample to be inspected, and determine the defect depth at this thermal image pixel according to the physical area of ​​the sample corresponding to each thermal image pixel, thereby realizing three-dimensional defect shape detection of each defect area.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] The present invention provides an infrared flaw detection device and method based on the scattering resonance of the temperature field of a convective thermal metamaterial. The working principle of the infrared flaw detection device is the scattering resonance effect of the temperature field of a convective thermal metamaterial. It uses a time-harmonic heat source to excite a mechanically driven uniform-speed convection ring structure, and places a sample ring on the upper surface of the convection ring. When the sample ring is free of defects, the infrared camera can be used to observe the existence of a resonance peak in the temperature field on the upper surface of the sample ring by scanning the excitation heat source. Compared with the case without a convective thermal metamaterial, the amplitude can be amplified by more than 3 times; when the sample ring has a defect, it is excited at this frequency, and it can be observed that the amplitude response of the scattering temperature field on the upper surface of the sample defect is linearly related to the size of the defect. Therefore, based on the infrared detection of the sample surface temperature field, high-sensitivity detection of the defect position and defect size can be achieved based on the change in the temperature field amplitude. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the infrared flaw detection device provided by the present invention when carrying a non-destructive sample.

[0028] Figure 2 This is a schematic diagram of the infrared flaw detection device provided by the present invention when carrying a destructive sample.

[0029] Figure 3 This is a schematic diagram of the flaw detection mechanism principle of the infrared flaw detection device provided by the present invention.

[0030] Figure 4 The present invention provides a numerical simulation result of the resonance effect of the convection ring in the infrared flaw detection device.

[0031] Figure 5 The present invention provides a numerical simulation result of the temperature amplitude response to the defect degree after the convection ring and the sample are combined in the infrared flaw detection device provided by the present invention.

[0032] Figure 6 The figure is a schematic diagram of the steps of an infrared flaw detection method based on the infrared flaw detection device provided by the present invention.

[0033] The reference numerals in the figure are: convection ring 1, time-harmonic excitation heat source 2, driving mechanism 3, infrared imaging device 4, sample to be inspected 5, scratch defect 6. It should be noted that the elements in the figure are schematic and do not represent actual scale drawing. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0035] In the description of the present invention, it is to be understood that when an element is considered to be "connected" to another element, it may be directly connected to the other element or indirectly connected, that is, there are intermediate elements. On the contrary, when an element is said to be "directly" connected to another element, there are no intermediate elements.

[0036] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for the purpose of distinction and description, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

[0037] In a preferred embodiment of the present invention, an infrared flaw detection device based on convective thermal metamaterial temperature field scattering resonance is provided, and its structural schematic diagram is shown as follows: Figure 1 As shown. The infrared flaw detection device includes a convection ring 1, a time-harmonic excitation heat source 2, a driving mechanism 3 and an infrared imaging device 4. The present invention is based on the temperature field scattering resonance effect of the convection thermal metamaterial excited by the time-harmonic heat source. The temperature field amplitude corresponding to the resonance frequency responds to the structural or material defects more obviously. Therefore, based on this effect, non-destructive infrared flaw detection can be achieved on the sample 5 to be inspected.

[0038] In the infrared flaw detection device, the convection ring 1 is a homogeneous annular cross-section cylinder made of a convection thermal metamaterial, and its two end faces are respectively a first end face and a second end face, wherein the first end face is used to carry the sample 5 to be inspected in a tightly fitting manner.

[0039] It should be noted that the placement posture of the above-mentioned convection ring 1 can generally be placed in a manner that the axial direction is vertical to the horizontal plane, so that the first end face and the second end face are respectively the top face and the bottom face. In this way, the sample 5 to be inspected only needs to be placed in a close fit on the top face of the convection ring 1 to keep the two from being separated. Of course, in theory, in other postures, as long as the sample 5 to be inspected can be placed in a close fit on the first end face of the convection ring 1 through other fixing mechanisms, the same effect can be achieved.

[0040] It should be noted that the convection thermal metamaterial used in the above-mentioned convection ring 1 is a material with high thermal conductivity, such as silver, copper, and other alloys or non-metallic materials may also be used. In an embodiment of the present invention, the convection ring 1 is preferably processed with copper to reduce the amplitude attenuation during the temperature field transmission process. The material inside the convection ring 1 should be homogeneous and defect-free to ensure that the internal thermal convection is completely uniform. The thermal convection in the convection thermal metamaterial can be introduced by driving the convection ring 1 to rotate at a uniform speed around the axial direction, and the convection intensity is the rotational angular velocity Ω0 of the convection ring 1. The cross-section of the convection ring 1 is a ring, and the ratio of the inner diameter of the ring to the outer diameter of the ring is preferably above 0.8.

[0041] In the infrared flaw detection device, the rotation driving end of the driving mechanism 3 is connected to the convection ring 1, and is used to drive the convection ring 1 to rotate at a uniform speed around the axis. When the convection ring 1 is driven to rotate by the driving mechanism 3, the sample 5 to be inspected remains fixed and does not rotate synchronously with the convection ring 1.

[0042] It should be noted that the above-mentioned driving mechanism 3 can directly or indirectly drive the convection ring 1. In the embodiment of the present invention, the mechanical driving mechanism 3 is implemented by a motor, and the driving shaft of the motor can be coaxially fixed with the convection ring 1 through a non-heat-conducting connector. However, in other embodiments, the above-mentioned driving mechanism 3 can also be in the form of an electromagnetic driving mechanism 3. The electromagnetic driving mechanism 3 can be installed on the convection ring 1 by installing corresponding matching components, and then drive the convection ring 1 in a non-contact manner based on electromagnetic induction, thereby avoiding heat transfer between the convection ring 1 and the driving mechanism 3.

[0043] It should be noted that, since the sample 5 to be inspected needs to be kept fixed when the convection ring 1 is driven to rotate by the driving mechanism 3, it can be considered to be achieved by setting an external clamping mechanism or a limiting mechanism. In addition, the mechanism for fixing the sample 5 to be inspected should be made of a non-heat-conductive material to avoid heat transfer.

[0044] In the infrared flaw detection device, the time-harmonic excitation heat source 2 is arranged on the side where the second end face of the convection ring 1 is located, and is used to input a time-harmonic temperature field to the second end face of the convection ring 1 .

[0045] It should be noted that the excitation temperature output by the time-harmonic excitation heat source 2 satisfies the sine oscillation form or the cosine oscillation form in the time domain. When the excitation temperature T(t) output by the time-harmonic excitation heat source 2 satisfies the sine oscillation form in the time domain, its expression is T(t)=A0*sin(ω0t+φ0)+T0, where t is time, A0 is amplitude, ω0 is the excitation angular frequency, φ0 is phase, and T0 is the preset center reference temperature. Similarly, when the excitation temperature T(t) output by the time-harmonic excitation heat source 2 satisfies the cosine oscillation form in the time domain, its expression is T(t)=A0*cos(ω0t+φ0)+T0.

[0046] The above-mentioned time-harmonic excitation heat source 2 can be in various forms. In an embodiment of the present invention, the time-harmonic excitation heat source 2 adopts an electrically controlled semiconductor refrigeration sheet, which can be directly attached to the first end face of the convection ring 1 to directly exchange heat with the convection ring 1. However, in other embodiments, the time-harmonic excitation heat source 2 can also adopt a laser heating device, which can use the first end face of the convection ring 1 as a heating surface, heat the first end face by irradiating the laser onto the first end face of the convection ring 1, and then change its temperature. Of course, in addition to these two forms, other forms of time-harmonic excitation heat sources 2 are theoretically feasible as long as they can achieve temperature field output in the form of sinusoidal oscillation or cosine oscillation.

[0047] In the infrared flaw detection device, the adjustable range of the angular velocity Ω0 of the driving mechanism 3 driving the convection ring 1 to rotate and the adjustable range of the time-harmonic temperature field excitation angular frequency ω0 input to the convection ring 1 by the time-harmonic excitation heat source 2 overlap. In other words, at least one of the driving mechanism 3 and the time-harmonic excitation heat source 2 is adjustable, and of course both are also adjustable. The angular velocity Ω0 of the driving mechanism 3 can be adjusted by changing the power of the driving mechanism 3, and the excitation angular frequency ω0 of the time-harmonic excitation heat source 2 can be adjusted by the internal control unit of the time-harmonic excitation heat source 2, and the specific details shall be subject to the actual devices used by both.

[0048] The structure of the sample 5 to be inspected can be annular or any planar shape whose size is smaller than the difference between the inner and outer radii of the convection ring. However, no matter what structure is adopted, the size of the sample 5 to be inspected should not exceed the first end face of the convection ring 1 that carries the sample, that is, the projection of the sample 5 to be inspected when placed on the first end face should be completely inside the first end face. When the sample is placed on the convection ring 1, the two need to maintain a fit state to reduce the heat transfer resistance as much as possible. In practical applications, the first end face of the convection ring 1 can be coated with a thermal interface material for reducing the thermal resistance between the convection ring 1 and the sample 5 to be inspected, such as thermal grease with high thermal conductivity. After coating with thermal grease, the possibility of heat generated by friction between the convection ring 1 and the sample 5 to be inspected affecting the accuracy of the inspection can also be reduced.

[0049] In the infrared flaw detection device, the infrared imaging device 4 is arranged on the side where the first end surface of the convection ring 1 is located, and its imaging direction is along the axial direction of the convection ring 1 toward the sample to be detected 5, and is used to collect a heat map (heatmap) of the surface of the sample to be detected 5. The specific form of the infrared imaging device 4 is not limited, and it can generally be implemented by a high-sensitivity infrared camera or infrared thermal imager.

[0050] In the above-mentioned infrared flaw detection device, the purpose of overlapping the adjustable range of the angular velocity Ω0 of the driving mechanism 3 and the adjustable range of the time-harmonic temperature field excitation angular frequency ω0 of the time-harmonic excitation heat source 2 is to ensure that the above-mentioned angular velocity Ω0 and the above-mentioned excitation angular frequency ω0 can be controlled to remain the same. The infrared flaw detection device uses the state in which the above-mentioned angular velocity and the excitation angular frequency remain the same as the flaw detection state of the infrared flaw detection device. The flaw detection principle of the above-mentioned infrared flaw detection device is introduced below.

[0051] In the above infrared flaw detection device, the time-harmonic temperature field input by the time-harmonic excitation heat source 2 to the second end face of the convection ring 1 has a certain excitation angular frequency ω0, and the output temperature oscillates in the time domain in a sine or cosine form. The convection thermal metamaterial in the convection ring 1 has an extremely high thermal conductivity, and the convection speed inside it is uniform. Therefore, when the time-harmonic temperature field is input to the convection ring 1, the convection ring 1 will further uniformly transfer heat to the sample 5 to be inspected. Figure 1As shown, if the sample 5 to be inspected does not contain defects, the thermal convection inside it is also uniform. When the excitation angular frequency ω0 is constantly changing, it can be observed that the temperature field scattering response to a certain excitation angular frequency input is the most obvious on the surface of the sample structure, and the scattering spectrum amplitude is the largest. The excitation angular frequency is the resonant frequency of the combined structure of the convection ring 1 and the sample 5 to be inspected. Through theoretical and numerical simulation analysis, it is found that the resonant frequency is very close to the angular velocity Ω0 (i.e., the convection rate of the thermal metamaterial) at which the driving mechanism 3 drives the convection ring 1 to rotate. This shows that when the heat source temperature field and the convective thermal metamaterial resonate at the same frequency, the amplitude can be greatly improved compared to the case without convection. However, as Figure 2 As shown, when there is a scratch defect 6 (or other forms of curves such as perforations) in the sample 5 to be inspected, the thermal diffusion rate in the sample will inevitably decrease, resulting in the attenuation of the amplitude of the observed temperature field. The attenuation rate is linearly related to the diffusion rate (degree of defect). Therefore, the inspection mechanism of the infrared inspection device of the present invention is as follows: Figure 3 As shown, firstly, a non-defective sample structure is combined on a convection ring 1 made of a convection thermal metamaterial, and then a temperature field is inputted in a time-harmonic manner. By changing the above angular velocity Ω0 or the excitation angular frequency ω0, a resonant frequency that can form a thermal scattering resonance effect (i.e., a set of Ω0 and ω0 that can obtain the maximum amplitude of the temperature field outputted from the surface of the non-defective sample) is found. At this time, the above angular velocity Ω0 and the above excitation angular frequency ω0 remain the same, and then a defective sample structure is combined on a convection ring 1 made of a convection thermal metamaterial, and the temperature field is continuously inputted in a time-harmonic manner. Under the excitation of the above resonant frequency, the amplitude response change of the temperature field on the surface of the defective sample structure is obtained, so that the equivalent thermal diffusivity change caused by the defect is determined according to the linear relationship between the amplitude change of the temperature field and the equivalent thermal diffusivity change caused by the defect. The relationship between the equivalent thermal diffusivity change caused by the defect and the defect duty cycle can be calculated by the Maxwell-Garnett formula. Finally, the defect size can be determined according to the defect duty cycle. At the same time, the defect position can be identified from the temperature field (i.e., the thermal image) on the surface of the defective sample structure, so that the present invention can realize the position location of the defect and the quantitative estimation of the size.

[0052] In order to more clearly demonstrate the existence of the thermal scattering resonance effect, in the embodiment of the present invention, based on the above Figure 1 The infrared flaw detection device shown in the figure uses Matlab to simulate a single convection ring 1 made of convection thermal metamaterial. The convection ring 1, which rotates clockwise at a uniform speed, is excited by a time-harmonic temperature field in the form of cosine oscillation, and the temperature field output of the end face of the sample on the other side is observed. The parameters of the Matlab simulation are as follows: the input excitation temperature field center reference temperature T0 = 383.15 K, the amplitude A0 = 100 K, the convection ring 1 is a copper ring, the thermal conductivity is 400 W / (m·K), and the mass density is 8960 kg / m3 , constant pressure specific heat capacity is 385 J / (kg·K), the cross section of the copper ring is annular, with an inner radius of 5.0 cm and an outer radius of 5.5 cm. In order to verify the temperature field scattering resonance effect between the convective thermal metamaterial and the time-harmonic excitation heat source, the input cosine-form time-harmonic heat source excitation is simulated on the lower surface of the convection ring 1, and the temperature field output on the upper surface of the convection ring 1 is observed with the help of a high-precision infrared camera. In this embodiment, the heat source is swept to observe whether a resonance peak will appear in the output temperature field when the excitation angular frequency ω0 is close to the rotation speed of the convective thermal metamaterial. Of course, in other embodiments, the excitation angular frequency ω0 can be fixed, and the resonance effect of the convective thermal metamaterial and the input temperature field signal can be observed by changing the rotation angular velocity Ω0 of the convective thermal metamaterial. Figure 4 The figure shows the numerical simulation results of the temperature field scattering resonance effect of the sample bearing surface of the convection ring 1. It can be seen that when the excitation angular frequency ω0 gradually increases from 0 and the frequency is swept, a resonance peak will appear in the temperature field scattering, and the resonance frequency is approximately equal to the angular velocity of rotation of the convection thermal metamaterial. In this embodiment, a variety of rotation angular velocities Ω0 of the convection ring 1 are set to verify the universality. When the rotation angular velocity Ω0 of the convection ring 1 is 0.05 rad / s (gray), 0.10 rad / s (red), 0.15 rad / s (blue), and 0.20 rad / s (green), the temperature field amplitude is represented by the normalized scattering coefficient, and the resonance peaks all appear at the same time when the excitation angular frequency ω0 and the rotation angular velocity Ω0 are the same, which is the temperature field scattering resonance effect between the convection thermal metamaterial and the time-harmonic excitation heat source. It can also be found that the temperature field amplitude at the resonance peak position can be increased by more than 5 times compared with the case without convection, which will greatly improve the infrared flaw detection capability of the device.

[0053] In addition, this embodiment further follows Figure 2As shown, a combination of a convection ring 1 made of a convection thermal metamaterial and a sample 5 to be inspected is numerically simulated, and a combination of a convection ring 1 made of a convection thermal metamaterial and a non-destructive homogeneous sample of the same model as the sample 5 to be inspected is numerically simulated, so as to obtain the numerical simulation results of the defect degree response. In the simulation of this embodiment, a ring structure with the same size as the convection ring 1 is used as the sample 5 to be inspected, and a high thermal conductivity silicone grease is applied between the sample and the convection ring 1 to reduce the energy loss during the temperature field transfer process. In the same way as the numerical simulation of a single convection ring 1, a cosine-shaped time-harmonic heat source excitation is simulated on the lower surface of the convection ring 1, and the temperature field output of the upper surface of the sample 5 to be inspected is observed with the help of a high-precision infrared camera. Since defects such as scratches and perforations will inevitably change the sample structure and thermal diffusivity, the reduction in thermal diffusivity will directly increase the energy loss in the temperature field scattering process, resulting in a reduction in the output temperature field amplitude. In the simulation, the thermal conductivity of the sample 5 to be inspected is 200 W / (m·K), the structural size is the same as that of the convective thermal metamaterial ring, the resonant frequency is π / 4 rad / s, and the normalized amplitude is the amplitude ratio of the defective scattering temperature field to the defect-free scattering temperature field under the resonant frequency excitation. Figure 5 The figure shows the change of the normalized amplitude of the surface temperature field output of the sample 5 to be inspected with the decrease of the equivalent thermal diffusivity caused by the defect. It can be seen that there is a linear relationship between the two ,in is the amplitude variation of the temperature field output on the upper surface of the sample 5 to be inspected, is the change in equivalent thermal diffusivity caused by the defect. Therefore, the linear relationship The coefficients in can be calibrated in advance and then used in actual detection.

[0054] In an embodiment of the present invention, the linear relationship The coefficient calibration method is as follows: First, place the homogeneous non-destructive sample on the convection ring 1 and observe the temperature field amplitude under the flaw detection state; then, place a series of homogeneous samples of the same model as the homogeneous non-destructive sample but with known size defects on the convection ring 1 and observe the temperature field amplitude under the flaw detection state. The defect sizes on different samples are different, and the obtained temperature field amplitudes are also different. Based on the temperature field amplitudes of the homogeneous non-destructive sample and the homogeneous sample with known size defects, the change in the temperature field amplitude of the homogeneous samples with different defect sizes relative to the homogeneous non-destructive sample can be calculated. At the same time, the equivalent thermal diffusivity of homogeneous non-destructive samples and homogeneous samples with different defect sizes can be measured, and then the change in the equivalent thermal diffusivity of homogeneous samples with different defect sizes relative to the homogeneous non-destructive samples can be calculated. Finally, based on the two types of variable data obtained, we can fit and The linear relationship equation between them is determined by the coefficient of the linear relationship equation.

[0055] It should be noted that the equivalent thermal diffusivity of homogeneous non-destructive samples and homogeneous samples with different defect sizes can be determined experimentally or obtained by substituting the known defect volume duty cycle into the Maxwell-Garnet equation.

[0056] When scratches, perforations and other defects cause changes in the structure of the sample to be tested, the duty cycle f represents the proportion of the defect volume in the overall volume of the sample structure, and the diffusion rate change is It can be calculated according to the Maxwell-Garnett formula:

[0057]

[0058] in, is the thermal diffusivity of the defect-free sample, is the thermal diffusivity of the defective material, such as a scratch or a puncture, which may be air.

[0059] The present invention will further demonstrate the above Figure 1 The infrared flaw detection method of the infrared flaw detection device shown in the figure has the following process: Figure 6 As shown, the specific steps include S1~S4.

[0060] S1. Adjust the driving mechanism 3 and the time-harmonic excitation heat source 2 in the infrared flaw detection device so that the angular velocity Ω0 driven by the driving mechanism 3 to drive the convection ring 1 to rotate is the same as the time-harmonic temperature field excitation angular frequency ω0 input to the convection ring 1 by the time-harmonic excitation heat source 2, thereby maximizing the temperature field amplitude output from the first end face of the convection ring 1 through the resonance effect, and the infrared flaw detection device is in the flaw detection state.

[0061] It should be noted that when adjusting the driving mechanism 3 and the time-harmonic excitation heat source 2 in the infrared flaw detection device, which one to adjust can be selected according to the adjustable conditions of the two. Finally, the angular velocity Ω0 and the excitation angular frequency ω0 can be kept the same. In practical applications, the resonance peak that will appear in the output temperature field when the excitation angular frequency is close to the angular velocity of the convective thermal metamaterial can be observed by sweeping the heat source. Of course, the resonance effect of the convective thermal metamaterial and the input temperature field signal can also be observed by fixing the excitation angular frequency and changing the angular velocity of the convective thermal metamaterial.

[0062] S2. Keep the infrared flaw detection device in the flaw detection state, place a non-destructive homogeneous sample of the same model as the sample to be detected 5 on the first end face of the convection ring 1, and keep the projection of the non-destructive homogeneous sample on the first end face completely located within the first end face; after the temperature field output from the surface of the non-destructive homogeneous sample stabilizes, collect the first thermal image of the surface of the non-destructive homogeneous sample by the infrared imaging device 4.

[0063] It should be noted that after the non-destructive homogeneous sample is placed on the first end face of the convection ring 1, it takes a certain amount of time for the two to achieve thermal convection stability inside each other, so it is necessary to wait for a period of time until the temperature field output on the surface of the non-destructive homogeneous sample is stable before collecting the first thermal image on the end face of the non-destructive homogeneous sample that is not in contact with the convection ring 1. The specific waiting time can be determined according to actual conditions and is not limited to this.

[0064] In this step, due to the existence of the resonance effect, the temperature field output amplitude will be greatly improved compared to the case without convection, so the thermal field image in the field of view of the infrared imaging device 4 will be more sensitive to structural and material changes. A resonant frequency time-harmonic heat source is used to excite the convective thermal metamaterial that rotates uniformly at the resonance rate, and a non-destructive homogeneous sample is placed above the convective thermal metamaterial. The temperature field output at the sample at this time is observed by using the infrared imaging device 4 to obtain information such as the temperature field amplitude.

[0065] S3. Keep the infrared flaw detection device in the flaw detection state, place the sample 5 to be detected on the first end face of the convection ring 1, and keep the projection of the sample 5 to be detected on the first end face completely within the first end face; after waiting for the temperature field output on the surface of the flaw detection sample 5 to stabilize, the infrared imaging device 4 collects a second thermal image of the surface of the sample 5 to be detected.

[0066] It should be noted that, like the non-destructive homogeneous sample, after the flaw detection sample 5 is placed on the first end face of the convection ring 1, it takes a certain amount of time for the thermal convection inside each to stabilize, so it is necessary to wait for a period of time until the temperature field output on the surface of the flaw detection sample 5 stabilizes before collecting the first thermal image on the end face of the non-destructive homogeneous sample that is not in contact with the convection ring 1. The specific waiting time can be determined according to actual conditions and is not limited to this.

[0067] In this step, after replacing the lossless homogeneous sample with the defective sample, the convective thermal metamaterial rotating at a uniform speed at the resonance rate is excited by a resonant frequency time-harmonic heat source, and the temperature field output at the defective sample at this time is observed by using an infrared imaging device 4, that is, a thermal image is recorded, and the defect position is locked according to the thermal image and information such as the temperature field amplitude is recorded. Due to the presence of defects, such as scratches or perforations, the equivalent thermal conductivity and thermal diffusivity of the sample will be reduced, thereby causing the temperature field output amplitude to be reduced compared to the defect-free case, and the amplitude reduction is linearly related to the reduction rate of the equivalent thermal conductivity or thermal diffusivity. Since the resonance effect amplifies the temperature field amplitude, the temperature field amplitude change caused by the defect is more easily observed by the infrared imaging device 4. Subsequently, the diffusivity change can be inferred based on the temperature field amplitude change, and the defect size can be further obtained with the help of the equivalent medium theory.

[0068] S4. Identify all defective areas from the second thermal image based on the change in temperature field amplitude, and obtain the temperature field amplitude change of each defective area from the first thermal image and the second thermal image, and then convert the temperature field amplitude change of each defective area into an equivalent thermal diffusivity change according to a pre-calibrated linear relationship, and then substitute the equivalent thermal diffusivity change of each defective area into the Maxwell-Garnett formula to calculate the volume ratio of each defective area in the sample 5 to be inspected (i.e., the duty cycle f), so as to quantitatively determine the defect size of each defective area in the sample 5 to be inspected.

[0069] It should be noted that it is easy to identify the defective area from the second thermal image based on the change in the temperature field amplitude, because the temperature field at the position without defects in the second thermal image is uniform, while the defective position will have obvious non-uniformity. Therefore, the defective area can be identified by the naked eye or automatically identified by the recognition algorithm. There may be one or more defective areas in a second thermal image.

[0070] When the defect size of the defect area is quantitatively detected in the above step S4, a defect area can be regarded as a whole, and the overall volume ratio of the defect in the sample to be inspected 5 is determined, and then the overall size of the defect (i.e., the defect volume) is determined. Of course, a single defect area itself may also have non-uniformity, such as Figure 2 The scratch defect 6 present in the sample 5 may not have a uniform depth, and may have different depths at different positions. For this situation, in another embodiment of the present invention, for each defective area in the sample 5 to be inspected, each thermal image pixel in the defective area may be regarded as a sub-defect. Then, the temperature field amplitude change corresponding to each thermal image pixel in the area is obtained, and the volume ratio of the sub-defect corresponding to each thermal image pixel in the sample 5 to be inspected is calculated according to the process in S4, and then the actual volume of the sub-defect corresponding to each thermal image pixel is calculated according to the known volume of the sample 5 to be inspected, and then the physical area of ​​the sample corresponding to each thermal image pixel (which can be determined by the internal and external parameters of the camera) is divided by the physical area to determine the defect depth at this thermal image pixel. In this way, the corresponding defect depth can be determined for each thermal image pixel position in each defective area, and the three-dimensional defect shape can be refined and inverted in combination with the planar position of the defective area.

[0071] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An infrared flaw detection device based on convective thermal metamaterial temperature field scattering resonance, characterized in that: It includes a driving mechanism, a convection ring, a time-harmonic excitation heat source and an infrared imaging device; The convection ring is a homogeneous annular cross-section cylinder made of convection thermal metamaterial, and its two end faces are respectively a first end face and a second end face, wherein the first end face is used to carry the sample to be inspected in a tightly fitting manner; The rotating driving end of the driving mechanism is connected to the convection ring, and is used to drive the convection ring to rotate at a uniform speed around the axis; and when the convection ring is driven to rotate by the driving mechanism, the sample to be inspected remains fixed and rotates asynchronously; The time-harmonic excitation heat source is arranged on the side where the second end surface of the convection ring is located, and is used to input a time-harmonic temperature field to the second end surface of the convection ring; The adjustable range of the angular velocity of the driving mechanism driving the convection ring to rotate and the adjustable range of the time-harmonic temperature field excitation angular frequency input by the time-harmonic excitation heat source into the convection ring overlap, and the state in which the angular velocity and the excitation angular frequency remain the same is used as the flaw detection state of the infrared flaw detection device; The infrared imaging device is arranged on the side where the first end surface of the convection ring is located, and its imaging direction is along the axial direction of the convection ring toward the sample to be inspected, and is used to collect thermal images of the surface of the sample to be inspected.

2. The infrared flaw detection device based on convective thermal metamaterial temperature field scattering resonance as claimed in claim 1 is characterized in that: The convection thermal metamaterial used in the convection ring is silver or copper.

3. The infrared flaw detection device based on convective thermal metamaterial temperature field scattering resonance as claimed in claim 1, characterized in that: The driving mechanism is a mechanical driving mechanism or an electromagnetic driving mechanism.

4. The infrared flaw detection device based on convective thermal metamaterial temperature field scattering resonance as claimed in claim 1, characterized in that: The time-harmonic excitation heat source adopts an electrically controlled semiconductor refrigeration sheet attached to the first end surface of the convection ring, or adopts a laser heating device using the first end surface of the convection ring as a heating surface.

5. The infrared flaw detection device based on convective thermal metamaterial temperature field scattering resonance as claimed in claim 1, characterized in that: The excitation temperature output by the time-harmonic excitation heat source satisfies a sinusoidal oscillation form or a cosine oscillation form.

6. The infrared flaw detection device based on convective thermal metamaterial temperature field scattering resonance as claimed in claim 1, characterized in that: The angular velocity at which the driving mechanism drives the convection ring to rotate is adjustable, and the angular frequency of the time-harmonic temperature field excitation input by the time-harmonic excitation heat source into the convection ring is fixed.

7. The infrared flaw detection device based on convective thermal metamaterial temperature field scattering resonance as claimed in claim 1, characterized in that: The angular velocity at which the driving mechanism drives the convection ring to rotate is fixed, and the angular frequency of the time-harmonic temperature field excitation input by the time-harmonic excitation heat source into the convection ring is adjustable.

8. The infrared flaw detection device based on convective thermal metamaterial temperature field scattering resonance as claimed in claim 1, characterized in that: The first end surface of the convection ring is coated with a thermal interface material for reducing the thermal resistance between the convection ring and the sample to be inspected.

9. An infrared flaw detection method using the infrared flaw detection device according to any one of claims 1 to 8, characterized in that: include: S1. The driving mechanism and the time-harmonic excitation heat source in the infrared flaw detection device are adjusted so that the angular velocity of the convection ring driven by the driving mechanism is the same as the angular frequency of the time-harmonic temperature field excitation input into the convection ring by the time-harmonic excitation heat source, thereby maximizing the amplitude of the temperature field outputted from the first end face of the convection ring through the resonance effect, and the infrared flaw detection device is in a flaw detection state; S2, keeping the infrared flaw detection device in a flaw detection state, placing a non-destructive homogeneous sample of the same model as the sample to be detected on the first end face of the convection ring, and keeping the projection of the non-destructive homogeneous sample on the first end face completely located within the first end face; after the temperature field output from the surface of the non-destructive homogeneous sample is stable, the infrared imaging device collects a first thermal image of the surface of the non-destructive homogeneous sample; S3, keeping the infrared flaw detection device in a flaw detection state, placing the sample to be detected on the first end face of the convection ring, and keeping the projection of the sample to be detected on the first end face completely within the first end face; after waiting for the temperature field output on the surface of the flaw detection sample to stabilize, the infrared imaging device collects a second thermal image of the surface of the sample to be detected; S4. Identify all defect areas from the second thermal image based on the temperature field amplitude change, and obtain the temperature field amplitude change of each defect area from the first thermal image and the second thermal image, and then convert the temperature field amplitude change of each defect area into an equivalent thermal diffusivity change according to a pre-calibrated linear relationship, and then substitute the equivalent thermal diffusivity change of each defect area into the Maxwell-Garnett formula to calculate the volume ratio of each defect area in the sample to be inspected, so as to quantitatively determine the defect size of each defect area in the sample to be inspected.

10. The infrared flaw detection method according to claim 9, characterized in that: For each defect area in the sample to be inspected, it is necessary to obtain the temperature field amplitude change corresponding to each thermal image pixel in the area, and then calculate the volume ratio of each thermal image pixel in the sample to be inspected, and determine the defect depth at this thermal image pixel based on the physical area of ​​the sample corresponding to each thermal image pixel, thereby realizing three-dimensional defect shape detection of each defect area.

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