A method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency

Abstract

The present invention discloses a method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency, which belongs to the field of non-destructive detection, including: measuring the longitudinal wave and transverse wave ultrasonic resonance frequencies under a certain temperature field, obtaining the longitudinal wave and transverse wave ultrasonic propagation velocities, and then obtaining the temperatures measured by the longitudinal wave and transverse wave respectively according to the pre-calibrated wave velocity and temperature relationship, and finally obtaining the comprehensive resonant temperature measurement result according to the resonant frequency points of the longitudinal wave and transverse wave. The present invention can effectively measure the internal temperature of the structure when the ultrasonic propagation time data is not easy to collect or the collected data is distorted, and has high measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the field of non-destructive detection, and more specifically, to a method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency. Background Art

[0002] Ultrasonic method is one of the important methods in the field of non-destructive detection, with the advantages of non-contact measurement and good real-time performance. In the actual engineering of aerospace or petrochemical engineering, when various mechanical equipment are in operation, the temperature inside the structure can greatly affect the operating efficiency and safety of the equipment. Therefore, the measurement of the internal temperature of high-temperature mechanical equipment is very important for the health monitoring and thermal safety assessment of mechanical equipment.

[0003] The traditional solution only collects the ultrasonic propagation time through the pulse echo method, and determines the internal temperature of the structure based solely on the relationship between the ultrasonic propagation time and temperature. When the ultrasonic propagation time data is difficult to collect or the collected data is distorted, the temperature measurement accuracy will decrease or even become impossible to measure, and the scope of application will be limited. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency. The method can effectively measure the internal temperature of the structure with high measurement accuracy when the ultrasonic propagation time data is difficult to collect or the collected data is distorted.

[0005] The object of the present invention is achieved through the following solutions:

[0006] A method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency, comprising: measuring the longitudinal wave and transverse wave ultrasonic resonance frequencies under a certain temperature field, obtaining the longitudinal wave and transverse wave ultrasonic propagation velocities, and then obtaining the temperatures measured by the longitudinal wave and transverse wave respectively according to a pre-calibrated wave velocity and temperature relationship, and finally calculating the comprehensive resonant temperature measurement result according to the resonant frequency points of the longitudinal wave and the transverse wave.

[0007] Furthermore, the resonant frequency includes: a resonant frequency obtained through comprehensive processing of transverse waves and longitudinal waves.

[0008] Furthermore, the method measures the longitudinal and transverse ultrasonic resonance frequencies under a certain temperature field, obtains the longitudinal and transverse ultrasonic propagation velocities, obtains the temperatures measured by the longitudinal and transverse waves respectively according to the pre-calibrated wave velocity and temperature relationship, and finally calculates the comprehensive resonant temperature measurement result according to the resonant frequency points of the longitudinal and transverse waves, specifically including the following sub-steps:

[0009] S1, when the ultrasonic frequency propagating in the detected object is equal to the natural frequency, resonance is formed. The relationship between this frequency and the thickness of the object is:

[0010] (1.1);

[0011] in, L is the structure thickness, n represents the order of the resonant frequency, is the wavelength, represents the resonant frequency, is the propagation speed of ultrasound in solid media, including ultrasonic longitudinal waves and transverse waves. With temperature T The relationship is calibrated in advance according to the following formula:

[0012] (1.2);

[0013] Among them, the coefficient a, b, c Determined by experiment, varies according to the material;

[0014] S2, substitute equation (1.2) into (1.1) to obtain:

[0015] (1.3);

[0016] According to formula (1.3), when the resonant frequency f When the order is determined and the thickness of the structure is L When the structure is at a certain temperature, one or a series of resonant frequencies are measured. f The data of ultrasonic wave propagation speed under a certain temperature state is obtained. v ( T );

[0017] S3, when exciting and receiving ultrasonic longitudinal waves or ultrasonic transverse waves, the propagation speeds are expressed as and , the temperature values ​​under longitudinal wave and shear wave detection conditions are obtained by formula (1.2) and , according to the following formula and The final internal temperature of the structure is:

[0018] (1.4);

[0019] in, , , p Indicates the weight of the extracted resonant frequency points of the longitudinal wave echo to the total number of points, q Indicates the weight of the extracted resonant frequency points of the shear wave echo to the total number of points, x Indicates the number of resonant frequency points of the extracted longitudinal wave echo, y Indicates the number of resonant frequency points of the extracted longitudinal wave echo.

[0020] Furthermore, the method further includes the steps of: obtaining the influence of temperature on ultrasonic wave propagation time through the resonant frequency to measure the temperature field inside the structure, specifically including: obtaining the resonant frequency through measurement f Then, the propagation speed is obtained by formula (1.3): v , and then obtain the ultrasonic propagation time t.

[0021] Furthermore, the resonant frequency is obtained by measuring f Then, the propagation speed is obtained by formula (1.3): v , and then obtain the ultrasonic wave propagation time t, which specifically includes the sub-steps:

[0022] If the temperature field inside the structure is uniform, t can be calculated using the following formula:

[0023] (1.5).

[0024] Furthermore, the resonant frequency is obtained by measuring f Then, the propagation speed is obtained by formula (1.3): v , and then obtain the ultrasonic wave propagation time t, which specifically includes the sub-steps:

[0025] If the temperature field inside the structure is non-uniform, t can be calculated using the following formula:

[0026] (1.6);

[0027] in, t represents the propagation time of ultrasound in the structure, z Represents the direction of heat transfer.

[0028] Furthermore, the temperature field includes a uniform or non-uniform temperature field inside a pure metal, alloy, non-metallic material, or composite material structure.

[0029] Furthermore, the measurement is real-time measurement.

[0030] The beneficial effects of the present invention include:

[0031] (1) Aiming at the need to measure the internal temperature of a high-temperature structure when mechanical equipment is in operation, the present invention proposes an ultrasonic measurement method based on ultrasound that can monitor the internal temperature of a structure. This method can realize real-time measurement of the internal temperature of a high-temperature structure when the machine equipment is in normal operation or stopped operation.

[0032] (2) The present invention is different from the traditional method of only collecting ultrasonic propagation time through the pulse echo method and determining the internal temperature of the structure based solely on the relationship between ultrasonic propagation time and temperature. The method of the present invention can effectively measure the internal temperature of the structure by selecting the resonant frequency of the collected ultrasonic wave when the ultrasonic propagation time data is difficult to collect or the collected data is distorted. Therefore, it has a higher measurement accuracy. As the temperature of the structure increases, the frequency of the interference signal decreases, and the accuracy of the temperature measurement is also improved. In addition, the resonant frequency temperature measurement method proposed in the present invention is not limited to the excited ultrasonic waveform. It can not only realize the resonant temperature measurement of transverse waves or longitudinal waves, but also can realize the comprehensive resonant temperature measurement through the resonant frequency of transverse waves and longitudinal waves, thereby further improving the temperature measurement accuracy; as long as a stable resonant frequency point can be obtained, the internal temperature of the structure can be successfully obtained.

[0033] (3) The method of the present invention is applicable to the measurement of uniform or non-uniform temperature fields inside pure metal, alloy, non-metallic material and composite material structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0035] Figure 1 This is a schematic diagram of ultrasonic detection;

[0036] Figure 2 The figure is a flowchart of the steps of the method according to the embodiment of the present invention. DETAILED DESCRIPTION

[0037] All features disclosed in all embodiments in this specification, or steps in all methods or processes implicitly disclosed, except for mutually exclusive features and / or steps, can be combined and / or expanded or replaced in any manner.

[0038] The specific implementation process of the present invention is as follows:

[0039] The present invention is a method for measuring the internal temperature of a high-temperature solid based on ultrasonic harmonic frequency, and the specific technical scheme is as follows:

[0040] like Figure 1 As shown, when the frequency of the ultrasonic wave propagating in the detected object is equal to the natural frequency, resonance is formed. The relationship between the frequency and the thickness of the object is:

[0041] (1.1);

[0042] is the wavelength, L is the structure thickness, is the propagation speed of ultrasound in solid media, including ultrasonic longitudinal waves and transverse waves. With temperature T Generally speaking, the relationship between speed and temperature is usually linear or nonlinear, and the coefficient a, b, c Usually determined experimentally, the propagation speed varies depending on the material. With temperature T The relationship generally needs to be calibrated in advance:

[0043] (1.2);

[0044] Substituting equation (1.2) into (1.1) we can obtain:

[0045] (1.3);

[0046] It can be seen that the resonant frequency order ( They are the first-order resonant frequency, the second-order resonant frequency, the third-order resonant frequency, ..., n The resonant frequency of the first order) is determined and the thickness of the structure L When the structure is at a certain temperature, one or a series of resonant frequencies are measured. f The data of the propagation speed of ultrasound at a certain temperature can be obtained. v ( T ), assuming that when exciting and receiving ultrasonic longitudinal waves or ultrasonic transverse waves, the propagation speeds are expressed as and , the temperature values ​​under longitudinal wave and shear wave detection conditions can be obtained respectively through formula (1.2): and , then the final structural temperature can be determined as or , you can also combine and The final internal temperature of the structure is expressed as follows:

[0047] (1.4);

[0048] in, , , p Indicates the weight of the extracted resonant frequency points of the longitudinal wave echo to the total number of points, q Indicates the weight of the extracted resonant frequency points of the shear wave echo to the total number of points, x Indicates the number of resonant frequency points of the extracted longitudinal wave echo, yIndicates the number of resonant frequency points of the extracted longitudinal wave echo. The method flow chart is as follows Figure 2 shown.

[0049] If you want to obtain the change of ultrasonic propagation time under the influence of temperature, or want to obtain the internal temperature of the structure through ultrasonic time, but the ultrasonic propagation time data is not easy to collect or the collected data is distorted, you can get the resonant frequency by measuring f After that, the propagation speed can be obtained through formula (1.3) v , and then obtain the ultrasonic propagation time:

[0050] (1.5);

[0051] If the temperature field inside the structure is non-uniform, equation (1.5) becomes:

[0052] (1.6);

[0053] in, t represents the propagation time of ultrasound in the structure, z Represents the direction of heat transfer.

[0054] In summary, the present invention is particularly aimed at effectively measuring the internal temperature of the structure by selecting the resonant frequency of the collected ultrasonic wave, or obtaining the influence of temperature on the ultrasonic wave propagation time through the resonant frequency, when the ultrasonic wave propagation time data is difficult to collect or the collected data is distorted. It is not limited to the excited ultrasonic wave shape, and can not only realize the resonant temperature measurement of transverse waves or longitudinal waves, but also can realize the comprehensive resonant temperature measurement of transverse waves and longitudinal waves, thereby further improving the temperature measurement accuracy. It is suitable for the measurement of uniform or non-uniform temperature fields inside structures such as metals, alloys, refractory alloys, and metal-based composite materials.

[0055] On the basis of the above technical scheme, laser ultrasonic detection experiments were conducted to collect the ultrasonic longitudinal and transverse wave resonance frequencies of 10mm thick structural steel materials under four different uniform temperature fields of 25℃, 50℃, 75℃ and 100℃. The first-order resonance frequency was collected under one temperature condition and three resonance frequency points were collected under longitudinal and transverse wave detection conditions respectively.

[0056] According to the calibration experiment, the relationship between the ultrasonic propagation velocity and temperature inside the structural steel is obtained in advance:

[0057] (1.7);

[0058] (1.8);

[0059] The first-order resonant frequency and the corresponding temperature measurement results under different temperature conditions obtained by experimental measurement are shown in Table 1 (three resonant frequency points were collected under the same temperature condition, namelyp = q =3):

[0060] Table 1

[0061]

[0062] When ultrasonic waves propagate in a solid structure, their propagation speed is related to the elastic modulus. E ,density ρ , Poisson's ratio μ Related, according to the theoretical formula:

[0063] When ultrasonic waves propagate in a solid structure, their propagation speed is related to the elastic modulus. E ,density ρ , Poisson's ratio μ Related, according to the theoretical formula:

[0064] (1.9);

[0065] (1.10);

[0066] The physical properties of structural steel in the material library are approximately read in the simulation software COMSOL multi-physics simulation platform as shown in Table 2:

[0067] Table 2

[0068]

[0069] The internal temperature of the structure obtained by theoretical calculation by combining equations (1.7) and (1.8) is shown in Table 3:

[0070] Table 3

[0071]

[0072] Although there are certain errors in equations (1.7) and (1.8) obtained from the calibration experiment and in the reading of physical parameters, the resonant temperature measurement results, when compared with the theoretical calculation results, still reflect that this method can effectively measure the internal temperature of the structure with high accuracy.

[0073] The units involved in the embodiments of the present invention may be implemented by software or hardware, and the units described may also be arranged in a processor. The names of these units do not, in some cases, limit the units themselves.

[0074] According to one aspect of an embodiment of the present invention, a computer program product or a computer program is provided, the computer program product or the computer program includes a computer instruction, and the computer instruction is stored in a computer-readable storage medium. A processor of a computer device reads the computer instruction from the computer-readable storage medium, and the processor executes the computer instruction, so that the computer device executes the method provided in the above various optional implementations.

[0075] As another aspect, an embodiment of the present invention further provides a computer-readable medium, which may be included in the electronic device described in the above embodiment; or may exist independently without being assembled into the electronic device. The above computer-readable medium carries one or more programs, and when the above one or more programs are executed by an electronic device, the electronic device implements the method described in the above embodiment.

Claims

1. A method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency, characterized in that: Firstly, the longitudinal wave and transverse wave ultrasonic resonance frequencies under a certain temperature field are measured to obtain the longitudinal wave and transverse wave ultrasonic propagation velocities, and then the temperatures measured by the longitudinal wave and transverse wave are respectively obtained according to the pre-calibrated wave velocity and temperature relationship, and finally the comprehensive resonant temperature measurement result is calculated according to the resonant frequency points of the longitudinal wave and the transverse wave; specifically, the sub-steps are as follows: S1, when the ultrasonic frequency propagating in the detected object is equal to the natural frequency, resonance is formed. The relationship between this frequency and the thickness of the object is: (1.1)； in, L is the structure thickness, n represents the order of the resonant frequency, is the wavelength, represents the resonant frequency, is the propagation speed of ultrasound in solid media, including ultrasonic longitudinal waves and transverse waves. With temperature T The relationship is calibrated in advance according to the following formula: (1.2)； Among them, the coefficient a, b, c Determined by experiment, varies according to the material; S2, substitute equation (1.2) into (1.1) to obtain: (1.3)； According to formula (1.3), when the resonant frequency f When the order is determined and the thickness of the structure is L When the structure is at a certain temperature, one or a series of resonant frequencies are measured. f The data of ultrasonic wave propagation speed under a certain temperature state is obtained. v ( T ); S3, when exciting and receiving ultrasonic longitudinal waves or ultrasonic transverse waves, the propagation speeds are expressed as and , the temperature values ​​under longitudinal wave and shear wave detection conditions are obtained by formula (1.2) and , according to the following formula and The final internal temperature of the structure is: (1.4)； in, , , p Indicates the weight of the extracted resonant frequency points of the longitudinal wave echo to the total number of points, q Indicates the weight of the extracted resonant frequency points of the shear wave echo to the total number of points, x Indicates the number of resonant frequency points of the extracted longitudinal wave echo, y Indicates the number of resonant frequency points of the extracted longitudinal wave echo.

2. The method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency according to claim 1, characterized in that: The resonant frequency includes: the resonant frequency obtained by comprehensive processing of transverse waves and longitudinal waves.

3. The method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency according to claim 1, characterized in that: The method also includes the steps of: obtaining the influence of temperature on ultrasonic wave propagation time through the resonant frequency to measure the temperature field inside the structure, specifically including: obtaining the resonant frequency through measurement f Then, the propagation speed is obtained by formula (1.3): v , and then obtain the ultrasonic propagation time t.

4. The method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency according to claim 3, characterized in that: The resonant frequency is obtained by measuring f Then, the propagation speed is obtained by formula (1.3): v , and then obtain the ultrasonic wave propagation time t, which specifically includes the sub-steps: If the temperature field inside the structure is uniform, t can be calculated using the following formula: (1.5)。 5. The method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency according to claim 3, characterized in that: The resonant frequency is obtained by measuring f Then, the propagation speed is obtained by formula (1.3): v , and then obtain the ultrasonic wave propagation time t, which specifically includes the sub-steps: If the temperature field inside the structure is non-uniform, t can be calculated using the following formula: (1.6)； in, t represents the propagation time of ultrasound in the structure, z Represents the direction of heat transfer.

6. The method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency according to claim 1, characterized in that: The temperature field includes uniform or non-uniform temperature fields inside pure metal, alloy, non-metal material and composite material structures.

7. The method for measuring the internal temperature of a high-temperature structure based on ultrasonic harmonic frequency according to claim 1, characterized in that: The measurement is a real-time measurement.

Images