Metal long guide wire type temperature and stress detection dual function sensor

Abstract

The application discloses a metal long wire type temperature and stress detection dual-function sensor, which utilizes a local multi-bending back winding type metal long wire as a propagation carrier of ultrasonic guided waves and as an eddy current excitation and receiving element. When the ultrasonic guided waves propagating in the metal wire meet the local bending reflector, mode conversion and reflection will be generated, and the propagation time difference of the reflection signals of the same mode ultrasonic guided waves generated by the adjacent two bending reflectors is related to the average temperature of the metal wire between the two bending reflectors. The temperature measurement of multiple position points is realized by arranging multiple bending reflectors in the back winding type metal long wire. The dual-function sensor provided by the application can be applied to the temperature distribution measurement and stress detection of the surface of a metal structure under high-temperature variable load service conditions.

Description

Technical Field

[0001] This invention relates to a dual-function sensor for temperature and stress detection using a long metal guide wire, belonging to the field of non-destructive testing, and is suitable for temperature and stress detection of high-temperature variable load metal structures. Background Technology

[0002] Metal structures such as power plant boilers and nuclear power pipelines operate under high-temperature and variable-load conditions for extended periods. To monitor their safe operation, it is necessary to test the temperature and stress of these metal components. Currently used thermocouple temperature measurement technology suffers from drawbacks, such as the inability of a single sensor to achieve multi-point temperature measurement, high replacement rates, and high costs when used under high-temperature conditions.

[0003] The paper (Periyannan Suresh, Rajagopal Prabhu, Balasubramaniam Krishnan. Ultrasonic bent waveguides approach for distributed temperature measurement[J]. Ultrasonics, 2017, 74: 211-220.) uses silicon carbide wire to construct a single waveguide with multiple local bends. The multiple reflected waves generated by the bends are used to realize temperature measurement at different locations. That is, the temperature at multiple heights in the furnace can be measured simultaneously using a single waveguide. However, this sensor cannot realize stress measurement. The literature (Fanlin Meng, Xiucheng Liu, Heyun Wang, Cunfu He, Bin Wu. Characterization of Elastic and Plastic Behaviors in Steel Plate Based on Eddy Current Technique Using a Portable Impedance Analyzer [J]. Journal of Sensors, 2017, 2017: 1-12.) used a portable eddy current analyzer to calibrate the relationship between eddy current impedance curves and stress in 45 steel. Several new stress-sensitive parameters were discovered from the impedance curves, and a method was proposed to use impedance information near the resonance point for high-sensitivity stress characterization, providing a new approach for eddy current detection of stress in ferromagnetic materials. However, this study was conducted at room temperature and did not consider the influence of high temperature and temperature changes on the stress test results. If temperature compensation is required for the measurement results, synchronous temperature testing using other temperature sensors is also necessary.

[0004] To achieve simultaneous multi-point temperature measurement of guided waves and eddy current stress testing, and to compensate for the eddy current stress measurement results using the temperature values ​​measured by the sensor itself, this invention discloses a dual-function sensor for temperature and stress detection using a long metal guide wire. Ultrasonic guided waves and alternating current are simultaneously applied within the long metal guide wire. Based on the principles that temperature changes the ultrasonic guided wave velocity and stress changes the eddy current density, the simultaneous detection of temperature and stress in the conductive body below the long metal guide wire is achieved. This invention is expected to be applied to the monitoring of operational parameters of metal structures operating under high-temperature and variable-load conditions, such as power plant boilers and nuclear power pipelines. Summary of the Invention

[0005] The purpose of this invention is to develop a dual-function sensor for temperature and stress detection using a long metal guide wire, capable of both temperature measurement based on the ultrasonic guided wave principle and stress detection using the eddy current method. To achieve the above objective, this invention adopts the following technical solution:

[0006] The structural design of the dual-function temperature and stress detection sensor using a long metal wire needs to consider both guided wave temperature measurement and eddy current stress measurement requirements. This necessitates physical separation of the guided wave reflector and the eddy current sensor. Furthermore, since the guided wave and eddy current detection are respectively conducted using stress waves and high-frequency currents through the thin wire, there is no mutual interference between them. Therefore, the long metal wire is designed with an overall U-shape. One side of the wire contains multiple inverted triangular or inverted U-shaped bends for reflectors, while the other side contains locally helical or runway-line bends. A piezoelectric sensor is installed on the end surface of the wire containing the inverted triangular or inverted U-shaped bends. Both ends of the long metal wire are connected to the eddy current detection circuit. The steps for simultaneously measuring the temperature and stress of the conductor below the long metal wire using this sensor are as follows:

[0007] An ultrasonic guided wave, generated by a piezoelectric sensor, propagates along a long metal wire. When it encounters a local "inverted triangle" or "inverted U" shaped bend reflector, mode conversion and reflection occur. The propagation time difference (Δt) of the reflected signal of the same mode ultrasonic guided wave generated by two adjacent bend reflectors varies linearly with the average temperature (T) of the metal wire between the two bend reflectors. By setting M "inverted triangle" or "inverted U" shaped bend reflectors in the wound metal wire, the average temperature of M-1 sections can be measured.

[0008] An alternating current output from an eddy current detection circuit is applied to a wound-type long metal conductor. When the current reaches the locally spiraled or runway-shaped bent conductor, eddy currents are generated in the conductor below the conductor. The eddy current detection circuit measures the impedance of the long metal conductor. Then, the guided wave temperature measurement data T and the impedance value Z measured by the eddy current detection circuit are substituted into the calibration equation for the impedance of the long metal conductor with respect to temperature and stress, Z = f(T,σ), to calculate the stress value within the conductor.

[0009] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0010] 1. This invention proposes an integrated dual-purpose sensing method based on a wound metal long guide wire with multiple local bends. It utilizes ultrasonic guided waves and alternating current propagating simultaneously in the long guide wire to achieve ultrasonic guided wave temperature measurement and eddy current stress measurement. The detection method is original.

[0011] 2. The technical solution provided by this invention can solve the problem of synchronous monitoring of temperature and stress in metal structural components under high-temperature variable load conditions. Attached Figure Description

[0012] Figure 1 Design of a dual-function sensor for temperature and stress detection using a long metal guide wire (A).

[0013] Figure 2 Design of a dual-function sensor for temperature and stress detection using a long metal guide wire (B).

[0014] Figure 3 Temperature detection of high-temperature variable load metal structures.

[0015] Figure 4 Stress testing of high-temperature variable load metal structures.

[0016] In the diagram: 1-Function generator; 2-Sampling resistor; 3-Piezoelectric sensor; 4-Ultrasonic guided wave excitation acquisition module; 5-Host computer; 6-Digital acquisition card; 7-M "inverted U-shaped" bent reflectors; 8-Runway line bent conductor; 9-M "inverted triangle" bent reflectors; 10-Local spiral conductor. Detailed implementation method:

[0017] Based on the above description of the invention, a dual-function sensor for temperature and stress detection using a long metal guide wire can be provided in the following embodiments. One specific embodiment provided below is merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0018] To provide a means for achieving guided wave temperature measurement and eddy current stress measurement using a single long metal wire, Figure 1 and Figure 2 The diagram shows two structural design schemes for a dual-function metal long-wire sensor. The metal wire has a diameter of approximately 0.5–1 mm and is generally in a double-turn folded shape. A length-extending piezoelectric element is fixedly mounted on the near-end surface of one side for exciting and receiving longitudinal modal ultrasonic guided waves within the wire. The two ends of the double-turn wire are connected to the function generator and digital acquisition card of the eddy current detection module for high-frequency eddy current signal excitation and reception.

[0019] A thin metal guide wire is laid on the surface of a metal component subjected to high-temperature variable loads, while eddy current and guided wave testing instruments are placed in the ambient temperature range. To measure the propagation velocity of guided waves within the thin guide wire, multiple inverted triangular or inverted U-shaped bends are designed on one side of the guide wire, serving as wave reflectors. The guided wave will generate reflected echoes after passing through these reflectors. The propagation time difference (Δt) of the reflected signal of the same mode ultrasonic guided wave at two adjacent bends varies linearly with the average temperature (T) of the metal wire between the two bends. Based on the known distance (L) between the bends, the average propagation velocity of the ultrasonic guided wave in that section can be obtained, and the temperature T of that section can be calibrated. Therefore, on the surface of a high-temperature component with an unknown temperature, the temperature of that section can be determined by measuring the ultrasonic guided wave propagation velocity at a certain location on the thin metal guide wire through a calibration curve. By setting M inverted triangular or inverted U-shaped bends in a long, looped metal guide wire, the average temperature of M-1 sections can be measured. Ultrasonic guided wave propagation signal such as Figure 3 As shown, the temperature at different locations on the surface of the high-temperature component can be obtained by calculating the wave velocity of the guided wave in segment M-1.

[0020] To induce eddy currents in the stress-monitoring area, a spiral or runway-shaped bent conductor is locally installed on the other side of the thin guide wire. When a high-frequency current is passed through the metal guide wire circuit, eddy currents will be generated within the conductive component below the coil. By monitoring the change in impedance of the metal guide wire using an eddy current detection module, the stress in the conductive component can be assessed. Figure 4 As shown, eddy current testing was performed on the surface of the high-temperature component. The guided wave temperature measurement data T and the impedance value Z measured by the eddy current testing circuit were substituted into the calibration equation Z=f(T,σ) of the impedance of the long metal wire with respect to temperature and stress, and the stress value in the conductor was obtained by calculation.

Claims

1. A metal long guide wire type temperature and stress detecting dual functional sensor, characterized by, The long metal guide wire is U-shaped, with multiple inverted triangle or inverted U-shaped bends and reflectors on one side and a spiral or runway-line bend on the other side. A piezoelectric sensor is installed on the end surface of the long metal guide wire containing the inverted triangle or inverted U-shaped bends and reflectors. The two ends of the long metal guide wire are connected to the eddy current detection circuit.

2. The metal long guide wire type temperature and stress detecting dual functional sensor according to claim 1, wherein The steps for simultaneously measuring the temperature and stress of the conductor beneath the long metal wire using this dual-function sensor are as follows: a. An ultrasonic guided wave generated by a piezoelectric sensor propagates along a long metal wire. When it encounters a local "inverted triangle" or "inverted U" shaped bend reflector, mode conversion and reflection will occur. The propagation time difference Δt of the reflected signal of the same mode ultrasonic guided wave generated by two adjacent bend reflectors varies linearly with the average temperature T of the long metal wire between the two bend reflectors. M "inverted triangle" or "inverted U" shaped bend reflectors are set in the U-shaped long metal wire to achieve the measurement of the average temperature of M-1 sections. b. The eddy current detection circuit outputs an alternating current which is fed into a U-shaped metal wire. When the alternating current reaches the locally spiral or runway-shaped bend in the wire, an eddy current is formed in the conductor below the wire. The eddy current detection circuit measures the impedance value of the metal wire. c. Substitute the average temperature T of the ultrasonic guided wave and the impedance value measured by the eddy current detection circuit into the calibration equation of the impedance of the long metal wire with respect to temperature and stress to calculate the stress value in the conductor.

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