Infrared pulse phase nondestructive testing device and method based on thermal resistance change of electrorheological fluid

Abstract

The invention provides an infrared pulse phase nondestructive testing device and method based on thermal resistance change of an electro-rheological fluid. The infrared pulse phase nondestructive testing device comprises a heat accumulator (2), the electro-rheological fluid (3), a thermal imager (4), a computer (5), a switch (6) and a pulse generator (7), the heat accumulator (2) is tightly attached to one side of the electrorheological body (3), and the heat accumulator (2) and the electrorheological body (3) are connected with the pulse generator (7) through a cable (8); the pulse generator (7) is connected with the computer (5), and the switch (6) is arranged between the pulse generator (7) and the computer (5); and the thermal imager (4) is connected with the computer (5). The technical scheme is suitable for detecting defects at deep hidden positions.

Description

Technical Field

[0001] The invention relates to the field of infrared detection technology, in particular to an infrared pulse phase nondestructive detection device and method based on the change of current rheological thermal resistance. Background Art

[0002] The infrared pulse phase method is an advanced detection technology that applies strong pulsed light to the surface of the sample to be tested. When the infrared heat wave encounters a defect during propagation in the component, its phase will change. By comparing the phase difference between the transmitted heat wave and the received heat wave, non-destructive detection of component defects can be achieved, which has the advantages of being fast and intuitive. However, the depth of defects that can be detected by this technology is not large, and it is usually used to detect shallow surface defects. The signal-to-noise ratio of deep defects is relatively low, because due to insufficient thermal excitation, the temperature rise of deep defects is weak (usually <0.5°C), which is easily confused with background noise, resulting in missed detection or misjudgment. In addition, the instruments and equipment required for detection are large in size and high in cost, making it difficult to achieve online detection. Summary of the invention

[0003] In view of this, the object of the present invention is to provide an infrared pulse phase nondestructive testing device and method based on the change of electrorheological thermal resistance, which is suitable for detecting defects in deeply buried areas.

[0004] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: an infrared pulse phase nondestructive detection device based on the change of thermal resistance of an electrorheological device, comprising a heat storage body 2, an electrorheological device 3, a thermal imager 4, a computer 5, a switch 6 and a pulse generator 7; one side of the electrorheological device 3 is closely attached to the heat storage body 2, and the heat storage body 2 and the electrorheological device 3 are connected to the pulse generator 7 through a cable 8; the pulse generator 7 is connected to the computer 5, and the switch 6 is arranged between the pulse generator 7 and the computer 5; the thermal imager 4 is connected to the computer 5; the heat storage body 2 comprises a heat storage body microcolumn array 23, and the electrorheological device 3 comprises an electrorheological fluid 32; Through the synergistic effect of the heat storage body 2 and the electrorheological fluid 3, when power is turned on during the detection phase, heat is transferred directionally to the deep defect area of ​​the test piece 1 through the heat storage body microcolumn array 23 and the orderly arranged electrorheological fluid 32; the infrared thermal imager 4 monitors the defects encountered by the infrared heat wave when propagating in the test piece 1, and detects the deep defects of the test piece 1.

[0005] In a preferred embodiment, the thermal storage body 2 is composed of a copper electrode 21 embedded in a substrate, a serpentine resistance wire 22 and a thermal storage body micro-column array 23; the copper electrode 21 embedded in the substrate is connected to the pulse generator 7 through the cable 8.

[0006] In a preferred embodiment, the thermal storage body micro-column array 23 specifically includes a first metal substrate and a semiconductor material coating, and the semiconductor material coating is disposed on the surface of the first metal substrate.

[0007] In a preferred embodiment, the electrorheological device 3 is composed of a flexible packaging layer 31, an electrorheological fluid 32, a pre-embedded electrode 33, a protective layer micro-column array 34, a copper sheet 35 and a flexible thermal conductive sheet 36; the pre-embedded electrode 33 is connected to the pulse generator 7 through the cable 8; The flexible encapsulation layer 31, the electrorheological fluid 32, the protective layer micro-column array 34, the copper sheet 35 and the flexible heat-conducting sheet 36 are arranged in sequence.

[0008] In a preferred embodiment, the protective layer micro-pillar array 34 , the copper sheet 35 and the flexible heat conductive sheet 36 form a protective layer of the electro-variant film 3 .

[0009] In a preferred embodiment, the protective layer micro-column array 34 specifically includes a second metal substrate, a semiconductor polymer layer and a flexible copper foil layer; the outer layer of the second metal substrate is sequentially provided with the semiconductor polymer layer and the flexible copper foil layer.

[0010] In a preferred embodiment, the electrorheological fluid 32 uses high-viscosity silicone oil as the liquid matrix, and adds hydrophobic fumed silica as a thixotropic agent so that the liquid matrix presents a gel state when standing still. Diamond powder, graphene and ceramic particles are used as fillers to form the filling layer of the electrorheological fluid 32.

[0011] In a preferred embodiment, the infrared thermal imager 4 transmits the captured surface dynamic temperature field of the test piece 1 to the computer 5 via a USB cable, and based on the temperature data measured by the infrared thermal imager 4, a time-temperature matrix is ​​established, the differential temperature field is calculated, the heat diffusion rate field is constructed, and the phase information is extracted and the defects are detected by the phase method.

[0012] In a preferred embodiment, the computer 5 sends a synchronization start instruction to the pulse generator 7 and the infrared thermal imager 4 through a hardware interrupt mechanism to ensure synchronization between the thermal excitation signal and the recording of the infrared thermal imager 4 .

[0013] The present invention also provides an infrared pulse phase nondestructive detection method based on the change of electrorheological thermal resistance, and adopts an infrared pulse phase nondestructive detection device based on the change of electrorheological thermal resistance; firstly, the heat storage body 2 and the electrorheological body 3 are closely attached to one side of the surface of the test piece 1, and then the heat storage body 2 and the electrorheological body 3 are charged and discharged according to the frequency, and when the heat storage body 2 and the electrorheological body 3 are synergistically powered on during the detection stage, the heat is directed to the deep defect area of ​​the test piece 1 through the high-conductivity heat storage body micro-column array 23 and the orderly arranged electrorheological fluid 32; after the power is turned off during the non-working period, the micro-column array increases the thermal resistance, and the electrorheological body is converted into an adiabatic state, which effectively prevents heat diffusion and maintains the thermal stability of the system; at the same time, the dynamic temperature distribution of the surface of the test piece 1 is photographed on the other side of the test piece 1 by an infrared thermal imager 4, and the temperature distribution information is collected by a computer 5; when the infrared heat wave encounters a defect during the propagation process in the test piece 1, its phase will change, and by comparing the phase difference between the emitted heat wave and the received heat wave, the phase analysis of the information data is performed on the computer 5 to realize the diagnosis of the defect.

[0014] Compared with the prior art, the present invention has the following beneficial effects: First, the temperature control is precise and the changes are regular, which is convenient for signal collection and analysis; second, the equipment used is small and easy to carry; third, it can be applied to the detection of in-service equipment. For example, when the temperature of the internal medium is very high, an electrostatic variable type device can be attached to the inner wall of the equipment, and the heat source inside the equipment itself can be used (without the use of other heating devices) to realize the detection of the equipment, thus creating a new and widely used detection method for the infrared pulse phase method.

[0015] Main application: Applicable to buried defect detection in oil and gas pipelines, pressure vessels, and scenes. Avoid sudden leakage accidents through periodic thermal stimulation and data analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of an infrared pulse phase nondestructive testing device based on the change of thermal resistance of the electrorheological machine according to a preferred embodiment of the present invention; Figure 2 It is a schematic diagram of the heat storage body structure of the infrared pulse phase nondestructive testing device based on the change of the thermal resistance of the electrorheological machine according to the preferred embodiment of the present invention; Figure 3 It is a schematic diagram of the electrorheological structure of an infrared pulse phase nondestructive testing device based on electrorheological thermal resistance change according to a preferred embodiment of the present invention; Figure 4 It is a schematic diagram of the structure of a heat storage body micro-column array of an infrared pulse phase nondestructive testing device based on the change of the electrorheological thermal resistance according to a preferred embodiment of the present invention; Figure 5This is a schematic diagram of the protective layer micro-column array structure of an infrared pulse phase non-destructive testing device based on electrorheological thermal resistance change in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0018] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0019] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.

[0020] Infrared pulse phase nondestructive testing device based on the change of current rheological thermal resistance, reference Figure 1-5 , including a heat storage body 2, an electrovar 3, a thermal imager 4, a computer 5, a switch 6 and a pulse generator 7; one side of the electrovar 3 is in close contact with the heat storage body 2, and the heat storage body 2 and the electrovar 3 are connected to the pulse generator 7 through a cable 8; the pulse generator 7 is connected to the computer 5, and the switch 6 is arranged between the pulse generator 7 and the computer 5; the thermal imager 4 is connected to the computer 5.

[0021] Specifically, the thermal storage body 2 is composed of a copper electrode 21 embedded in a substrate, a serpentine resistance wire 22 and a thermal storage body micro-column array 23; the copper electrode 21 embedded in the substrate is connected to the pulse generator 7 through the cable 8.

[0022] The thermal storage body micro-column array 23 specifically includes a first metal substrate 231 and a semiconductor material coating 232. The surface of the first metal substrate 231 is provided with the semiconductor material coating 232. Specifically, the first metal substrate 231 is a copper substrate.

[0023] Specifically, the electrorheological device 3 is composed of a flexible packaging layer 31, an electrorheological fluid 32, a pre-embedded electrode 33, a protective layer micro-column array 34, a copper sheet 35 and a flexible thermal conductive sheet 36; the pre-embedded electrode 33 is connected to the pulse generator 7 through the cable 8; The flexible encapsulation layer 31 , the electrorheological fluid 32 , the protective layer micro-pillar array 34 , the copper sheet 35 and the flexible thermal conductive sheet 36 are sequentially arranged. The protective layer micro-pillar array 34 , the copper sheet 35 and the flexible thermal conductive sheet 36 form the protective layer of the electrorheological fluid 3 .

[0024] The protective layer micro-pillar array 34 specifically includes a second metal substrate 341 , a semiconductor polymer layer 342 and a flexible copper foil layer 343 ; the outer layer of the second metal substrate 341 is sequentially provided with the semiconductor polymer layer 342 and the flexible copper foil layer 343 .

[0025] Specifically, the electrorheological fluid 32 uses high-viscosity silicone oil as a liquid matrix, and adds hydrophobic fumed silica as a thixotropic agent to make the liquid matrix present a gel state when standing still. Diamond powder, graphene and ceramic particles are used as fillers to form a filling layer of the electrorheological fluid 32.

[0026] Specifically, the infrared thermal imager 4 transmits the captured surface dynamic temperature field of the test piece 1 to the computer 5 via a USB cable. Based on the temperature data measured by the infrared thermal imager 4, a time-temperature matrix is ​​established, the differential temperature field is calculated, the heat diffusion rate field is constructed, and the phase information is extracted and the defects are detected by the phase method.

[0027] Specifically, the computer 5 sends a synchronization start instruction to the pulse generator 7 and the infrared thermal imager 4 through a hardware interrupt mechanism to ensure synchronization between the thermal excitation signal and the recording of the infrared thermal imager 4 .

[0028] The infrared pulse phase nondestructive testing method based on the change of electrorheological thermal resistance adopts the infrared pulse phase nondestructive testing device based on the change of electrorheological thermal resistance; firstly, the heat storage body 2 and the electrorheological body 3 are closely attached to one side of the surface of the test piece 1, and then the heat storage body 2 and the electrorheological body 3 are charged and discharged according to the frequency, and when the heat storage body 2 and the electrorheological body 3 are energized in the detection stage, the heat is transferred to the deep defect area of ​​the test piece 1 through the high-conductivity heat storage body micro-column array 23 and the orderly arranged electrorheological fluid 32; after the power is turned off during the non-working period, the micro-column array increases the thermal resistance, and the electrorheological body is transformed into an adiabatic state, which effectively prevents heat diffusion and maintains the thermal stability of the system; at the same time, the dynamic temperature distribution of the surface of the test piece 1 is photographed on the other side of the test piece 1 by an infrared thermal imager 4, and the temperature distribution information is collected by a computer 5; when the infrared heat wave encounters a defect during the propagation process in the test piece 1, its phase will change, and by comparing the phase difference between the emitted heat wave and the received heat wave, the phase analysis of the information data is performed on the computer 5 to realize the diagnosis of the defect.

[0029] The heat transfer of the thermal storage body 2 to the test piece 1 is controlled by the coordinated mechanism of "micro-column array + electric field regulation" to achieve directional guidance of transient heat flow. Its working principle is as follows: the thermal storage body micro-column array 23 has a composite structure of a first metal matrix 231 and a semiconductor material coating 232. When voltage is applied, the thermal resistance of the semiconductor material coating 232 is reduced, thereby achieving efficient directional conduction of heat to the electrorheological fluid 3; electric field regulation: the electrorheological fluid 3 produces a phase change response under the action of the electric field. When power is on: the fillers of the electrorheological fluid 32 are arranged in order along the direction of the electric field to form a continuous heat conduction channel, and the thermal conductivity is improved; when power is off: the fillers of the electrorheological fluid 32 are randomly dispersed, and the thermal conductivity drops to the level of insulating materials. Through the synergistic effect of the two, when the power is turned on during the detection phase, the heat is directed to the deep defect area of ​​the test piece 1 through the high-conductivity heat storage body micro-column array 23 and the orderly arranged electrorheological body 3; after the power is turned off during the non-working period, the heat storage body micro-column array 23 increases the thermal resistance, and the electrorheological body 3 is transformed into an adiabatic state, effectively preventing heat diffusion and maintaining the thermal stability of the system. In order to prevent the electrorheological fluid from leaking due to the puncture of the encapsulation layer film of the electrorheological body 3 by iron thorns or protrusions, a protective layer is added outside the encapsulation layer. The protective layer is close to the electrorheological encapsulation layer and the test piece, and is composed of a copper sheet 35, two rows of protective layer micro-column arrays 34 and a flexible thermal conductive sheet 36. It has both thermal conductivity and anti-external force protection functions, and effectively prevents the electrorheological fluid from leaking due to external reasons. During the detection, the pulse generator 7 provides electrical signals to the heat storage body 2 and the electrorheological body 3, respectively controlling the heat release function of the heat storage body 2 and the electric field switch of the electrorheological body 3. Among them, the timing of the switch of the heat storage body 2 and the switch of the electrorheological body 3 can be adjusted independently to match the heat diffusion time. For example, after the switch of the heat storage body 2 is started, the switch of the electrorheological machine 3 is started after a delay of 0.1 to 0.5 seconds. The delay time is dynamically adjusted according to the thermal conductivity of the material of the test piece 1 and the defect depth to ensure that the heat is fully transferred to the deep defect area. By accurately controlling the opening and closing frequency of the circuit, the efficiency of heat transfer to the deep defects is effectively improved. The temperature contrast in the deep defect area can also be significantly improved through the periodic thermal resistance switching of the electrorheological machine, thereby improving the signal-to-noise ratio.

[0030] Before the test, the electric pulse generator 7 sends an electric signal to the heat storage body 2 through the cable 8. The heat storage body 2 introduces the electric signal into the inside through the copper electrode 21 embedded in the base, and the internal serpentine resistance wire 22 converts the electric energy into thermal energy to actively generate heat; the heat storage body micro-column array 23 is made of high thermal conductivity metal (such as copper), and the surface is composited with semiconductor materials (such as doped silicon or silicon carbide) through nano-coating technology to form a metal-semiconductor composite structure. The metal part is responsible for efficient heat conduction, and the semiconductor layer further optimizes the heat conduction path through electric field regulation. Its function is to increase the contact area with the electrostatic variable body 3 to strengthen the heat conduction from the heat storage body 2 to the electrostatic variable body 3.

[0031] During detection, the cable 8 sends an electrical signal to the embedded electrode 33 of the electrorheological fluid 3, so that the filler of the electrorheological fluid inside the encapsulation layer is arranged in the direction of the electric field to form a high thermal conductivity path. For the electrorheological fluid 32, high-viscosity silicone oil is selected as the liquid matrix to enhance its anti-fluidity and self-sustaining force while maintaining the electric field response capability; by adding a small amount of hydrophobic gas-phase silica as a thixotropic agent, the liquid matrix presents a gel state when standing still, and restores fluidity under pressure or electric field, realizing the controllable switching of "solid-liquid"; a certain proportion of diamond powder, graphene and ceramic particles are selected as fillers to form the filling layer of the electrorheological fluid, and PDMS (polydimethylsiloxane) is used as the flexible encapsulation layer 31, and the electrode 33 is embedded in the filling layer.

[0032] The protective layer is composed of a copper sheet 35, two rows of micro-column arrays 34 and a flexible thermal conductive sheet 36. The micro-column array of the protective layer is composed of copper and semiconductor polymers arranged alternately to form a "metal-semiconductor-metal" sandwich structure. The metal micro-columns are used to increase the contact area, and the semiconductor polymer layer adjusts the thermal resistance through electric field response. When the power is turned on, the conductivity of the semiconductor polymer is enhanced, the interface thermal resistance is reduced, and the heat is transferred to the test piece along the metal micro-columns in a direction; when the power is turned off, the semiconductor layer returns to a high-resistance state and blocks the heat conduction path. In conjunction with the phase change characteristics of the electrorheological fluid 3-2, the directional heat transfer capability is enhanced; the flexible thermal conductive sheet is close to the test piece, which not only prevents the packaging layer from being punctured, but also has good flexibility and can fit test pieces 1 of different shapes.

[0033] The supporting structure of the infrared thermal imager 4 can be moved forward and backward, left and right, and rotated 360° horizontally through wheels, and has a self-locking function, which is convenient for optimizing the shooting position. In addition, the infrared thermal imager transmits the captured dynamic temperature field of the test piece surface to the console computer 5 through a USB cable to store, reproduce and analyze the dynamic infrared thermal image, including: based on the actual temperature data measured by the thermal imager, establish a time-temperature matrix, calculate the differential temperature field, construct a heat diffusion rate field, extract phase information and detect defects by phase method.

[0034] The switch 6 of the pulse generator 7 is connected to the computer 5. In order to realize synchronous control, the computer 5 has a built-in multi-threaded applet, whose functions include: synchronous triggering: sending synchronous start instructions to the pulse generator 7 and the infrared thermal imager 4 through the hardware interrupt mechanism to ensure strict synchronization between the thermal excitation signal and the infrared thermal imager recording; communication management: communicating with the pulse generator 7 and the infrared thermal imager 4, and interacting with the PLC controller in real time to transmit delay time parameters and control instructions. The switch control of the current variant 3 is realized by the PLC controller, and the specific process is: when the heat storage body 2 is started, the PLC built-in high-speed timer module starts countdown, and after the countdown ends, the power-on signal of the current variant 3 is triggered.

Claims

1. Infrared pulse phase nondestructive testing device based on the change of thermal resistance of electrorheological device, characterized in that: The device comprises a heat storage body (2), an electrorheological device (3), a thermal imager (4), a computer (5), a switch (6) and a pulse generator (7); the heat storage body (2) is in close contact with one side of the electrorheological device (3); the heat storage body (2) and the electrorheological device (3) are connected to the pulse generator (7) via a cable (8); the pulse generator (7) is connected to the computer (5); the switch (6) is arranged between the pulse generator (7) and the computer (5); the thermal imager (4) is connected to the computer (5); the heat storage body (2) comprises a heat storage body microcolumn array (23); and the electrorheological device (3) comprises an electrorheological fluid (32); Through the synergistic effect of the heat storage body (2) and the electrorheological fluid (3), when power is turned on during the detection phase, heat is transferred directionally to the deep defect area of ​​the test piece (1) through the heat storage body micro-column array (23) and the orderly arranged electrorheological fluid (32); the defects encountered by the infrared heat wave when propagating in the test piece (1) are monitored by the infrared thermal imager (4), so as to detect the deep defects of the test piece (1).

2. The infrared pulse phase nondestructive testing device based on the change of electrorheological thermal resistance according to claim 1 is characterized in that: The heat storage body (2) is composed of a base-embedded copper electrode (21), a serpentine resistance wire (22), and a heat storage body micro-column array (23); the base-embedded copper electrode (21) is connected to the pulse generator (7) via the cable (8).

3. The infrared pulse phase nondestructive testing device based on the change of electrorheological thermal resistance according to claim 2 is characterized in that: The thermal storage body micro-column array (23) specifically comprises a first metal substrate and a semiconductor material coating, and the semiconductor material coating is provided on the surface of the first metal substrate.

4. The infrared pulse phase nondestructive testing device based on the change of electrorheological thermal resistance according to claim 1 is characterized in that: The electrorheological device (3) is composed of a flexible packaging layer (31), an electrorheological fluid (32), a pre-buried electrode (33), a protective layer micro-column array (34), a copper sheet (35), and a flexible thermal conductive sheet (36); the pre-buried electrode (33) is connected to the pulse generator (7) via the cable (8); The flexible packaging layer (31), the electrorheological fluid (32), the protective layer micro-column array (34), the copper sheet (35) and the flexible heat-conducting sheet (36) are arranged in sequence.

5. The infrared pulse phase nondestructive testing device based on the change of electrorheological thermal resistance according to claim 4 is characterized in that: The protective layer micro-column array (34), the copper sheet (35) and the flexible heat-conducting sheet (36) form a protective layer for the electrorheological device (3).

6. The infrared pulse phase nondestructive testing device based on the change of electrorheological thermal resistance according to claim 4 is characterized in that: The protective layer micro-column array (34) specifically comprises a second metal substrate, a semiconductor polymer layer and a flexible copper foil layer; the outer layer of the second metal substrate is provided with the semiconductor polymer layer and the flexible copper foil layer in sequence.

7. The infrared pulse phase nondestructive testing device based on the change of electrorheological thermal resistance according to claim 4 is characterized in that: The electrorheological fluid (32) uses high-viscosity silicone oil as a liquid matrix, and adds hydrophobic fumed silica as a thixotropic agent so that the liquid matrix presents a gel state when standing still. Diamond powder, graphene and ceramic particles are used as fillers to form a filling layer of the electrorheological fluid (32).

8. The infrared pulse phase nondestructive testing device based on the change of electrorheological thermal resistance according to claim 1 is characterized in that: The infrared thermal imager (4) transmits the captured surface dynamic temperature field of the test piece (1) to the computer (5) via a USB cable. Based on the temperature data measured by the infrared thermal imager (4), a time-temperature matrix is ​​established, the differential temperature field is calculated, the heat diffusion rate field is constructed, and the phase information is extracted and the defects are detected by the phase method.

9. The infrared pulse phase nondestructive testing device based on the change of electrorheological thermal resistance according to claim 1 is characterized in that: The computer (5) sends a synchronization start instruction to the pulse generator (7) and the infrared thermal imager (4) through a hardware interrupt mechanism, thereby ensuring synchronization between the thermal excitation signal and the recording of the infrared thermal imager (4).

10. Infrared pulse phase nondestructive testing method based on the change of electrorheological thermal resistance, characterized in that: An infrared pulse phase nondestructive testing device based on the change of electrorheological thermal resistance as described in any one of claims 1 to 9 is used; firstly, a heat storage body (2) and an electrorheological body (3) are placed in close contact with one side of the surface of a test piece (1); then, the heat storage body (2) and the electrorheological body (3) are charged and discharged at a frequency; when the heat storage body (2) and the electrorheological body (3) are powered on during the testing phase, heat is transferred to the deep defect area of ​​the test piece (1) through the high-conductivity heat storage body microcolumn array (23) and the orderly arranged electrorheological fluid (32); in the non After the power is turned off during the working period, the micro-column array increases the thermal resistance, and the electro-variable state is transformed into an adiabatic state, which effectively prevents heat diffusion and maintains the thermal stability of the system; at the same time, the dynamic temperature distribution of the surface of the test piece (1) is photographed by an infrared thermal imager (4) on the other side of the test piece (1), and the temperature distribution information is collected by a computer (5); when the infrared heat wave encounters a defect during the propagation process in the test piece (1), its phase will change, and by comparing the phase difference between the transmitted heat wave and the received heat wave, the phase analysis of the information data is performed on the computer (5) to achieve the diagnosis of the defect.

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