CA3089622C - Carrier-type pulsed eddy current testing method and device - Google Patents
Carrier-type pulsed eddy current testing method and device Download PDFInfo
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Abstract
The disclosure belongs to the technical field of non-destructive testing, and specifically discloses a carrier-type pulsed eddy current testing method and a carrier-type pulsed eddy current testing device. First, a metal plate is mounted under a pulsed eddy current sensor, and a square wave excitation is applied to the pulsed eddy current sensor to receive an attenuation curve, i.e., a carrier signal, of an induced voltage in the pulsed eddy current sensor over time as the square wave excitation decreases. Then, a metal component to be tested is placed under the pulsed eddy current sensor mounted with the metal plate, and the square wave excitation is applied to the pulsed eddy current sensor to receive an attenuation curve i.e., a modulating signal, of the induced voltage in the pulsed eddy current sensor over time as the square wave excitation decreases. The carrier signal and the modulating signal are demodulated to obtain the pulsed eddy current testing signal of the metal component to be tested. The disclosure solves the problem that the pulsed eddy current testing signal of metal components such as thin plates and small-diameter pipes is rapidly attenuated and cannot be effectively collected, and expands the application scope of pulsed eddy current testing.
Description
CARRIER-TYPE PULSED EDDY CURRENT TESTING METHOD AND DEVICE
BACKGROUND
[Technical Field]
[0001] The disclosure relates to the technical field of non-destructive testing, and more particularly, to a carrier-type pulsed eddy current testing method and a carrier-type pulsed eddy current detection device.
[Description of Related Art]
BACKGROUND
[Technical Field]
[0001] The disclosure relates to the technical field of non-destructive testing, and more particularly, to a carrier-type pulsed eddy current testing method and a carrier-type pulsed eddy current detection device.
[Description of Related Art]
[0002] In industries such as oil and gas, chemical engineering, electricity, and heating, during the long-term service, metal components such as natural gas pipelines and pressure vessels are prone to large-area corrosion due to the influence of extreme temperature, high pressure, and complex external environment, as well as erosion and corrosion of the medium.
As a result, cracking can arise and cause leakage or even explosion, which leads to huge economic losses, and causes great pollution and harms to the environment. The pulsed eddy current testing technique has the advantages of on-line testing, the ability of penetrate the cladding, etc., and has broad application in the detection of wall thinning of metal components. However, due to the limitation of acquisition accuracy, some extreme-sized metal components, such as thin plates and small-diameter pipes, are beyond the detection range of existing pulse eddy current testing instruments, which has become a major bottleneck restricting the development of this technique.
As a result, cracking can arise and cause leakage or even explosion, which leads to huge economic losses, and causes great pollution and harms to the environment. The pulsed eddy current testing technique has the advantages of on-line testing, the ability of penetrate the cladding, etc., and has broad application in the detection of wall thinning of metal components. However, due to the limitation of acquisition accuracy, some extreme-sized metal components, such as thin plates and small-diameter pipes, are beyond the detection range of existing pulse eddy current testing instruments, which has become a major bottleneck restricting the development of this technique.
[0003] Patent CN104849349A discloses a weld seam detection method for thin-wall small-diameter pipes. The method uses the combined technique of phased array ultrasonic testing, which can be used to detect weld seams on small-diameter pipes with wall thicknesses greater than or equal to 3.5 mm and less than or equal to 7 mm. The method produces no radiation and no pollution, besides, it is simple to operate, intuitive and easy to understand, because the detection results are displayed in the form of a three-dimensional image. Therefore, the method is suitable to detect weld seams on the thin-wall small-diameter pipes. However, similar to conventional ultrasonic testing, in this method, coupling agent is necessary during testing, so the installation of the sensor is much more difficult, resulting in the low testing efficiency. In addition, this method is not applicable to the detection of the component with coatings.
[0004] Chinese Standard GB/T 28705-2012 stipulates a pulsed eddy current testing method for detecting wall thinning caused by large-area corrosion without removing the cover layer, which is applicable to ferromagnetic components made of carbon steel and low alloy steel with diameters of no less than 50 mm, thicknesses of 3 mm to 65 mm and covered by insulations with thicknesses of 0 to 200 mm in a temperature of -150 C to 500 C. However, with regard to thin plates with thicknesses less than 3 mm or small-diameter pipes with diameters smaller than 50 mm, pulsed eddy current testing signals attenuate quickly, leading to poor acquisition accuracy. Therefore, this method is invalid for these components.
SUMMARY
SUMMARY
[0005] In view of the limitations of the above existing technology, the disclosure provides a carrier-type pulsed eddy current testing method and a carrier-type pulsed eddy current testing device. Specifically, a metal plate with high permeability or high conductivity is mounted under the pulsed eddy current sensor, named carrier plate in this patent. The pulsed eddy current signals are obtained by the sensor with the carrier plate. And then two signals are respectively measured with the metal component to be tested and without it. This method can solve the problem that the pulse eddy current testing signal of metal components such as thin plates and small-diameter pipes attenuates rapidly, so that signals of such components can be collected.
[0006] In order to achieve the above objective, an aspect of the disclosure provides a carrier-type pulsed eddy current testing method, including steps below.
[00071 Si: A metal plate is mounted under a pulsed eddy current sensor, and square wave excitation is applied to the pulsed eddy current sensor to receive an attenuation curve, i.e., a carrier signal, of an induced voltage in the pulsed eddy current sensor over time as the square wave excitation decreases.
[0008] S2: A metal component to be tested is placed under the pulsed eddy current sensor mounted with the metal plate, and square wave excitation is applied again to the pulsed eddy current sensor to receive an attenuation curve, i.e., a modulating signal, of an induced voltage in the pulsed eddy current sensor over time as the square wave excitation decreases.
[0009] S3: The carrier signal and the modulating signal are demodulated to obtain the pulsed eddy current testing signal of the metal part to be tested, and based on the original pulsed eddy current testing signal, a wall thickness or defect detection of the metal part to be tested can be realized.
[0010] Preferably, the metal component to be tested is a thin plate with a thickness of 2 mm to 40 mm or a pipe with a diameter greater than 25 mm.
[0011] Preferably, the square wave excitation in S1 and S2 is 0.1 A to 5 A.
[0012] Another aspect of the disclosure provides a carrier-type pulsed eddy current testing device for implementing the method, including a pulsed eddy current sensor, an external control unit, and a metal plate. The pulsed eddy current sensor is configured to induce the induced voltage when subjected to square wave excitation. The external control unit is connected to the pulsed eddy current sensor and is configured to provide the square wave excitation to the pulsed eddy current sensor and receive the induced voltage signal from the pulsed eddy current sensor.
The metal plate is mounted under the pulsed eddy current sensor.
[0013] Preferably, the pulsed eddy current sensor includes a sensor cover, an aviation connector, a driver coil, a pickup coil, and a sensor base. The sensor cover is mounted on the sensor base.
The aviation connector is fixed on the sensor cover and is connected to the external control unit.
The driver coil and the pickup coil are both fixed on the sensor base and are connected to the aviation connector.
[0014] Preferably, the external control unit includes a computer, a main control unit, a D/A
conversion unit, an A/D conversion unit, a power amplifier unit, and a weak signal conditioning unit. The computer is connected to the main control unit. The main control unit is connected to the D/A conversion unit and the A/D conversion unit. The D/A conversion unit is connected to the power amplifier unit. The A/D conversion unit is connected to the weak signal conditioning unit. The power amplifier unit and the weak signal conditioning unit are both connected to the pulsed eddy current sensor.
[0015] At the time of test, a square wave signal generated by the computer is transmitted to the D/A conversion unit via the main control unit. The D/A conversion unit converts the square wave signal into an analog signal and transmits it to the power amplifier unit. The power amplifier unit converts the analog signal into square wave excitation and provides it to the pulsed eddy current sensor. The pulsed eddy current sensor generates an induced voltage due to action of the square wave excitation. The weak signal conditioning unit obtains the induced voltage signal, amplifies and filters it, and transmits it to the A/D conversion unit.
The A/D conversion unit converts the amplified and filtered induced voltage signal into a digital signal and transmits it to the computer via the main control unit. The computer processes the digital signal to obtain relevant information.
[0016] Preferably, the metal plate is made of a highly magnetically conductive or highly electrically conductive material.
[0017] Preferably, a thickness of the metal plate is 1 mm to 20 mm.
[0018] Generally, compared with the existing technology, the above technical solutions conceived in the disclosure mainly have the following technical advantages.
[0019] 1. In the disclosure, a metal plate is adopted to obtain a carrier signal, and a pulsed eddy current testing signal of a metal component to be tested is obtained through a demodulation method, which solves the problem that it is difficult to effectively collect the signal of metal components such as thin plates and small-diameter pipes due to excessively rapid attenuation, and expands the application scope of pulsed eddy current testing.
[0020] 2. The disclosure reduces the requirements for signal acquisition precision and speed, and thus can simplify the pulsed eddy current testing device.
[0021] 3. The disclosure adopts a highly magnetically conductive or highly electrically conductive material to make the metal plate, and the eddy current is attenuated slowly in the metal plate, which reduces the attenuation rate of the obtained signal and is beneficial for signal collection.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic view showing a magnetic field distribution at the time of pulsed eddy current testing according to an embodiment of the disclosure.
[0023] FIG. 2 is an overall structural view showing a carrier-type pulsed eddy current testing device according to an embodiment of the disclosure.
[0024] FIG. 3 is a schematic structural view showing a pulsed eddy current sensor according to an embodiment of the disclosure.
[0025] FIG. 4 is a waveform diagram showing a carrier signal and a modulating signal when a small-diameter pipe is tested according to an embodiment of the disclosure.
[0026] FIG. 5 is diagram showing a waveform of an pulsed eddy current testing signal of a small-diameter pipe measured in an embodiment of the disclosure and a comparison waveform.
[0027] In all the drawings, the same reference numerals are used to denote the same elements or structures: 1- screw, 2- sensor cover, 3- sensor base, 4- pickup coil, 5-aviation connector, 6-driver coil, 7- metal plate, 8- metal component to be tested, 9- pulsed eddy current sensor, 10-power amplifier unit, 11- weak signal conditioning unit, 12- D/A conversion unit , 13- AID
conversion unit, 14- main control unit, 15-computer.
DESCRIPTION OF THE EMBODIMENTS
[0028] To provide a further understanding of the objectives, technical solutions, and advantages of the disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and the embodiments. It should be understood that the specific embodiments described herein are only used to interpret the disclosure and are not intended to limit the disclosure. In addition, the technical features involved in the various embodiments of the disclosure described below can be combined with each other as long as there is no conflict with each other.
[0029] A carrier-type pulsed eddy current testing method provided in an embodiment of the disclosure includes the following steps.
[0030] Si: A metal plate 7 is mounted under a pulsed eddy current sensor 9, and square wave excitation is applied to a driver coil 6 in the pulsed eddy current sensor 9.
The excitation current generates a changing magnetic field in space, as shown in FIG. 1. Thus, an eddy current is induced in the metal plate 7, and the eddy current also generates a corresponding magnetic field.
The above two magnetic fields form a superimposed magnetic field, and a pickup coil 4 receives an attenuation curve, i.e., a carrier signal, of the induced voltage generated by the superimposed magnetic field over time as the square wave excitation decreases.
[0031] S2: A metal component 8 to be tested is placed under the pulsed eddy current sensor 9 mounted with the metal plate 7, and square wave excitation is applied to the driver coil 6. The excitation current generates a changing magnetic field in space. eddy currents are induced in both the metal plate 7 and the metal component 8 to be tested, and the eddy currents also generate corresponding magnetic fields. The magnetic fields of the driver coil 6, the metal plate 7, and =
the metal component 8 to be tested together form a superimposed magnetic field. The pickup coil 4 receives an attenuation curve, i.e., a modulating signal, of the induced voltage generated by the superimposed magnetic field over time as the square wave excitation decreases.
[0032] S3: A finite difference operation is performed between the obtained modulating signal and the obtained carrier signal (i.e. using the obtained modulating signal to minus the obtained carrier signal) for demodulation to obtain an original pulsed eddy current testing signal of the metal component 8 to be tested, and based on the original pulsed eddy current testing signal, a wall thickness or defect detection of the metal component 8 to be tested can be realized.
Specifically, wall thickness measurement can be realized by extracting the signal feature of the late signal attenuation rate, and a component defect can be detected by performing differentiation with the signal of a defect-free region.
[0033] Specifically, the square wave excitation is 0.1 A to 5 A, and the applicable metal component 8 to be tested is a thin plate with a thickness of 2 mm to 40 mm or a pipe with a diameter greater than 25 mm.
[0034] The above method is implemented by a carrier-type pulsed eddy current testing device, which includes a pulsed eddy current sensor 9, a metal plate 7, and an external control unit.
[0035] As shown in FIG. 3, the pulsed eddy current sensor 9 includes a sensor cover 2, an aviation connector 5, a driver coil 6, a pickup coil 4, and a sensor base 3.
The sensor cover 2 is fixed on the sensor base 3 by screws I. The aviation connector 5 is mounted in a mounting hole of the sensor cover 2 and is connected to the external control unit. The driver coil 6 and the pickup coil 4 are both located inside the sensor base 3, are positioned by a mandrel, and are connected to the aviation connector 5. The lower part of the sensor base 3 is provided with a slot, and the metal plate 7 is mounted under the sensor base 3 through the slot.
[0036] As shown in FIG. 2, the external control unit includes a computer 15, a main control unit 14, a D/A conversion unit 12, an AID conversion unit 13, a power amplifier unit 10, and a weak signal conditioning unit 11. The computer 15 is connected to the main control unit 14. The
[00071 Si: A metal plate is mounted under a pulsed eddy current sensor, and square wave excitation is applied to the pulsed eddy current sensor to receive an attenuation curve, i.e., a carrier signal, of an induced voltage in the pulsed eddy current sensor over time as the square wave excitation decreases.
[0008] S2: A metal component to be tested is placed under the pulsed eddy current sensor mounted with the metal plate, and square wave excitation is applied again to the pulsed eddy current sensor to receive an attenuation curve, i.e., a modulating signal, of an induced voltage in the pulsed eddy current sensor over time as the square wave excitation decreases.
[0009] S3: The carrier signal and the modulating signal are demodulated to obtain the pulsed eddy current testing signal of the metal part to be tested, and based on the original pulsed eddy current testing signal, a wall thickness or defect detection of the metal part to be tested can be realized.
[0010] Preferably, the metal component to be tested is a thin plate with a thickness of 2 mm to 40 mm or a pipe with a diameter greater than 25 mm.
[0011] Preferably, the square wave excitation in S1 and S2 is 0.1 A to 5 A.
[0012] Another aspect of the disclosure provides a carrier-type pulsed eddy current testing device for implementing the method, including a pulsed eddy current sensor, an external control unit, and a metal plate. The pulsed eddy current sensor is configured to induce the induced voltage when subjected to square wave excitation. The external control unit is connected to the pulsed eddy current sensor and is configured to provide the square wave excitation to the pulsed eddy current sensor and receive the induced voltage signal from the pulsed eddy current sensor.
The metal plate is mounted under the pulsed eddy current sensor.
[0013] Preferably, the pulsed eddy current sensor includes a sensor cover, an aviation connector, a driver coil, a pickup coil, and a sensor base. The sensor cover is mounted on the sensor base.
The aviation connector is fixed on the sensor cover and is connected to the external control unit.
The driver coil and the pickup coil are both fixed on the sensor base and are connected to the aviation connector.
[0014] Preferably, the external control unit includes a computer, a main control unit, a D/A
conversion unit, an A/D conversion unit, a power amplifier unit, and a weak signal conditioning unit. The computer is connected to the main control unit. The main control unit is connected to the D/A conversion unit and the A/D conversion unit. The D/A conversion unit is connected to the power amplifier unit. The A/D conversion unit is connected to the weak signal conditioning unit. The power amplifier unit and the weak signal conditioning unit are both connected to the pulsed eddy current sensor.
[0015] At the time of test, a square wave signal generated by the computer is transmitted to the D/A conversion unit via the main control unit. The D/A conversion unit converts the square wave signal into an analog signal and transmits it to the power amplifier unit. The power amplifier unit converts the analog signal into square wave excitation and provides it to the pulsed eddy current sensor. The pulsed eddy current sensor generates an induced voltage due to action of the square wave excitation. The weak signal conditioning unit obtains the induced voltage signal, amplifies and filters it, and transmits it to the A/D conversion unit.
The A/D conversion unit converts the amplified and filtered induced voltage signal into a digital signal and transmits it to the computer via the main control unit. The computer processes the digital signal to obtain relevant information.
[0016] Preferably, the metal plate is made of a highly magnetically conductive or highly electrically conductive material.
[0017] Preferably, a thickness of the metal plate is 1 mm to 20 mm.
[0018] Generally, compared with the existing technology, the above technical solutions conceived in the disclosure mainly have the following technical advantages.
[0019] 1. In the disclosure, a metal plate is adopted to obtain a carrier signal, and a pulsed eddy current testing signal of a metal component to be tested is obtained through a demodulation method, which solves the problem that it is difficult to effectively collect the signal of metal components such as thin plates and small-diameter pipes due to excessively rapid attenuation, and expands the application scope of pulsed eddy current testing.
[0020] 2. The disclosure reduces the requirements for signal acquisition precision and speed, and thus can simplify the pulsed eddy current testing device.
[0021] 3. The disclosure adopts a highly magnetically conductive or highly electrically conductive material to make the metal plate, and the eddy current is attenuated slowly in the metal plate, which reduces the attenuation rate of the obtained signal and is beneficial for signal collection.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic view showing a magnetic field distribution at the time of pulsed eddy current testing according to an embodiment of the disclosure.
[0023] FIG. 2 is an overall structural view showing a carrier-type pulsed eddy current testing device according to an embodiment of the disclosure.
[0024] FIG. 3 is a schematic structural view showing a pulsed eddy current sensor according to an embodiment of the disclosure.
[0025] FIG. 4 is a waveform diagram showing a carrier signal and a modulating signal when a small-diameter pipe is tested according to an embodiment of the disclosure.
[0026] FIG. 5 is diagram showing a waveform of an pulsed eddy current testing signal of a small-diameter pipe measured in an embodiment of the disclosure and a comparison waveform.
[0027] In all the drawings, the same reference numerals are used to denote the same elements or structures: 1- screw, 2- sensor cover, 3- sensor base, 4- pickup coil, 5-aviation connector, 6-driver coil, 7- metal plate, 8- metal component to be tested, 9- pulsed eddy current sensor, 10-power amplifier unit, 11- weak signal conditioning unit, 12- D/A conversion unit , 13- AID
conversion unit, 14- main control unit, 15-computer.
DESCRIPTION OF THE EMBODIMENTS
[0028] To provide a further understanding of the objectives, technical solutions, and advantages of the disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and the embodiments. It should be understood that the specific embodiments described herein are only used to interpret the disclosure and are not intended to limit the disclosure. In addition, the technical features involved in the various embodiments of the disclosure described below can be combined with each other as long as there is no conflict with each other.
[0029] A carrier-type pulsed eddy current testing method provided in an embodiment of the disclosure includes the following steps.
[0030] Si: A metal plate 7 is mounted under a pulsed eddy current sensor 9, and square wave excitation is applied to a driver coil 6 in the pulsed eddy current sensor 9.
The excitation current generates a changing magnetic field in space, as shown in FIG. 1. Thus, an eddy current is induced in the metal plate 7, and the eddy current also generates a corresponding magnetic field.
The above two magnetic fields form a superimposed magnetic field, and a pickup coil 4 receives an attenuation curve, i.e., a carrier signal, of the induced voltage generated by the superimposed magnetic field over time as the square wave excitation decreases.
[0031] S2: A metal component 8 to be tested is placed under the pulsed eddy current sensor 9 mounted with the metal plate 7, and square wave excitation is applied to the driver coil 6. The excitation current generates a changing magnetic field in space. eddy currents are induced in both the metal plate 7 and the metal component 8 to be tested, and the eddy currents also generate corresponding magnetic fields. The magnetic fields of the driver coil 6, the metal plate 7, and =
the metal component 8 to be tested together form a superimposed magnetic field. The pickup coil 4 receives an attenuation curve, i.e., a modulating signal, of the induced voltage generated by the superimposed magnetic field over time as the square wave excitation decreases.
[0032] S3: A finite difference operation is performed between the obtained modulating signal and the obtained carrier signal (i.e. using the obtained modulating signal to minus the obtained carrier signal) for demodulation to obtain an original pulsed eddy current testing signal of the metal component 8 to be tested, and based on the original pulsed eddy current testing signal, a wall thickness or defect detection of the metal component 8 to be tested can be realized.
Specifically, wall thickness measurement can be realized by extracting the signal feature of the late signal attenuation rate, and a component defect can be detected by performing differentiation with the signal of a defect-free region.
[0033] Specifically, the square wave excitation is 0.1 A to 5 A, and the applicable metal component 8 to be tested is a thin plate with a thickness of 2 mm to 40 mm or a pipe with a diameter greater than 25 mm.
[0034] The above method is implemented by a carrier-type pulsed eddy current testing device, which includes a pulsed eddy current sensor 9, a metal plate 7, and an external control unit.
[0035] As shown in FIG. 3, the pulsed eddy current sensor 9 includes a sensor cover 2, an aviation connector 5, a driver coil 6, a pickup coil 4, and a sensor base 3.
The sensor cover 2 is fixed on the sensor base 3 by screws I. The aviation connector 5 is mounted in a mounting hole of the sensor cover 2 and is connected to the external control unit. The driver coil 6 and the pickup coil 4 are both located inside the sensor base 3, are positioned by a mandrel, and are connected to the aviation connector 5. The lower part of the sensor base 3 is provided with a slot, and the metal plate 7 is mounted under the sensor base 3 through the slot.
[0036] As shown in FIG. 2, the external control unit includes a computer 15, a main control unit 14, a D/A conversion unit 12, an AID conversion unit 13, a power amplifier unit 10, and a weak signal conditioning unit 11. The computer 15 is connected to the main control unit 14. The
-7-=
main control unit 14 is connected to the D/A conversion unit 12 and the A/D
conversion unit 13.
The D/A conversion unit 12 is connected to the power amplifier unit 10. The A/D conversion unit 13 is connected to the weak signal conditioning unit 11. The power amplifier unit 10 and the weak signal conditioning unit 11 are both connected to the pulsed eddy current sensor 9.
[0037] At the time of test, a square wave signal generated by the computer 15 is transmitted to the D/A conversion unit 12 via the main control unit 14 through the USB
protocol. The D/A
conversion unit 12 converts the square wave signal into an analog signal and transmits it to the power amplifier unit 10. The power amplifier unit 10 converts the analog signal into square wave excitation and provides it to the pulsed eddy current sensor 9. Due to the action of the square wave excitation, the pulsed eddy current sensor 9 generates an induced voltage. The weak signal conditioning unit 11 obtains the induced voltage signal, amplifies and filters it, and transmits it to the A/D conversion unit 13. The A/D conversion unit 13 converts the amplified and filtered induced voltage signal into a digital signal and transmits it to the computer 15 via the main control unit 14. The computer 15 processes the digital signal to obtain relevant information.
[0038] Further, the metal plate 7 is made of a highly magnetically conductive or highly electrically conductive material, such as #45 steel or aluminum, and the thickness of the metal plate 7 is 1 mm to 20 mm.
[0039] A specific example will be described below.
[0040] Example 1 [0041] A pulsed eddy current testing signal of a small-diameter pipe made of 304 stainless steel, with an outer diameter of 50 mm and a wall thickness of 10 mm, was obtained through the above device, and the adopted metal plate was an aluminum plate with a thickness of 6 mm.
[0042] The aluminum plate was mounted under the pulsed eddy current sensor, and square wave excitation was applied to obtain a carrier signal. Then, the small-diameter pipe was placed under the pulsed eddy current sensor mounted with the aluminum plate, and square wave excitation was
main control unit 14 is connected to the D/A conversion unit 12 and the A/D
conversion unit 13.
The D/A conversion unit 12 is connected to the power amplifier unit 10. The A/D conversion unit 13 is connected to the weak signal conditioning unit 11. The power amplifier unit 10 and the weak signal conditioning unit 11 are both connected to the pulsed eddy current sensor 9.
[0037] At the time of test, a square wave signal generated by the computer 15 is transmitted to the D/A conversion unit 12 via the main control unit 14 through the USB
protocol. The D/A
conversion unit 12 converts the square wave signal into an analog signal and transmits it to the power amplifier unit 10. The power amplifier unit 10 converts the analog signal into square wave excitation and provides it to the pulsed eddy current sensor 9. Due to the action of the square wave excitation, the pulsed eddy current sensor 9 generates an induced voltage. The weak signal conditioning unit 11 obtains the induced voltage signal, amplifies and filters it, and transmits it to the A/D conversion unit 13. The A/D conversion unit 13 converts the amplified and filtered induced voltage signal into a digital signal and transmits it to the computer 15 via the main control unit 14. The computer 15 processes the digital signal to obtain relevant information.
[0038] Further, the metal plate 7 is made of a highly magnetically conductive or highly electrically conductive material, such as #45 steel or aluminum, and the thickness of the metal plate 7 is 1 mm to 20 mm.
[0039] A specific example will be described below.
[0040] Example 1 [0041] A pulsed eddy current testing signal of a small-diameter pipe made of 304 stainless steel, with an outer diameter of 50 mm and a wall thickness of 10 mm, was obtained through the above device, and the adopted metal plate was an aluminum plate with a thickness of 6 mm.
[0042] The aluminum plate was mounted under the pulsed eddy current sensor, and square wave excitation was applied to obtain a carrier signal. Then, the small-diameter pipe was placed under the pulsed eddy current sensor mounted with the aluminum plate, and square wave excitation was
-8-applied to obtain a modulating signal. The obtained carrier signal and the obtained modulating signal are as shown in FIG. 4, where the vertical axis represents the induced voltage (V), and the horizontal axis represents the time (s).
[0043] Differentiation was performed on the carrier signal and the modulating signal to obtain a modulated/demodulated signal, i.e., the pulsed eddy current testing signal of the small-diameter pipe, as shown in FIG. 5, where the vertical axis represents the induced voltage (V), and the horizontal axis represents the time (s). Meanwhile, FIG. 5 also shows an original signal of the small-diameter pipe obtained by the pulsed eddy current sensor without the metal plate. It is shown that due to the limitation of the acquisition speed of the device, the early signal could not be accurately obtained, and its attenuation pattern deviated greatly from the theory. In contrast, the signal obtained by the method of the disclosure basically conforms to the theoretical attenuation law and can be used for subsequent defect or wall thickness analysis.
[0044] Those skilled in the art can easily understand that the above is only a preferred embodiment of the disclosure and is not intended to limit the disclosure. Any modification, equivalent replacement, and improvement made within the spirit and principle of the disclosure should be included in the protection scope of the disclosure.
[0043] Differentiation was performed on the carrier signal and the modulating signal to obtain a modulated/demodulated signal, i.e., the pulsed eddy current testing signal of the small-diameter pipe, as shown in FIG. 5, where the vertical axis represents the induced voltage (V), and the horizontal axis represents the time (s). Meanwhile, FIG. 5 also shows an original signal of the small-diameter pipe obtained by the pulsed eddy current sensor without the metal plate. It is shown that due to the limitation of the acquisition speed of the device, the early signal could not be accurately obtained, and its attenuation pattern deviated greatly from the theory. In contrast, the signal obtained by the method of the disclosure basically conforms to the theoretical attenuation law and can be used for subsequent defect or wall thickness analysis.
[0044] Those skilled in the art can easily understand that the above is only a preferred embodiment of the disclosure and is not intended to limit the disclosure. Any modification, equivalent replacement, and improvement made within the spirit and principle of the disclosure should be included in the protection scope of the disclosure.
-9-
Claims (8)
1. A carrier-type pulsed eddy current testing method, comprising steps below:
S1: mounting a metal plate (7) under a pulsed eddy current sensor (9) and applying a square wave excitation to a driver coil (6) in the pulsed eddy current sensor (9) to receive a first attenuation curve, i.e., a carrier signal, of a first induced voltage signal in the pulsed eddy current sensor (9) over time as the square wave excitation decreases, wherein the first induced voltage signal is generated by a superimposed magnetic field formed by a first magnetic field and a second magnetic field, wherein the first magnetic field is generated by a excitation current flowing through the driver coil (6), and the second magnetic field is generated by an eddy current induced in the metal plate (7);
S2: placing a metal component (8) to be tested under the pulsed eddy current sensor (9) mounted with the metal plate (7) and applying the square wave excitation to the pulsed eddy current sensor (9) to receive a second attenuation curve, i.e., a modulating signal, of a second induced voltage signal in the pulsed eddy current sensor (9) over time as the square wave excitation decreases, wherein the second induced voltage signal is generated by a superimposed magnetic field formed by the first magnetic field in step S 1, the second magnetic field in step Sl, and a third magnetic field, wherein the third magnetic field is generated by an eddy current induced in the metal component (8) to be tested; and S3: performing a finite difference operation between the modulating signal and the carrier signal to obtain an original pulsed eddy current testing signal of the metal component (8) to be tested, wherein based on the original pulsed eddy current testing signal, a wall thickness or defect detection of the metal component (8) to be tested is realized by:
measuring the wall thickness of the metal component (8) by extracting a signal feature of a late signal attenuation rate, and detecting a defect of the metal component (8) by performing differentiation with a signal of a defect-free region.
S1: mounting a metal plate (7) under a pulsed eddy current sensor (9) and applying a square wave excitation to a driver coil (6) in the pulsed eddy current sensor (9) to receive a first attenuation curve, i.e., a carrier signal, of a first induced voltage signal in the pulsed eddy current sensor (9) over time as the square wave excitation decreases, wherein the first induced voltage signal is generated by a superimposed magnetic field formed by a first magnetic field and a second magnetic field, wherein the first magnetic field is generated by a excitation current flowing through the driver coil (6), and the second magnetic field is generated by an eddy current induced in the metal plate (7);
S2: placing a metal component (8) to be tested under the pulsed eddy current sensor (9) mounted with the metal plate (7) and applying the square wave excitation to the pulsed eddy current sensor (9) to receive a second attenuation curve, i.e., a modulating signal, of a second induced voltage signal in the pulsed eddy current sensor (9) over time as the square wave excitation decreases, wherein the second induced voltage signal is generated by a superimposed magnetic field formed by the first magnetic field in step S 1, the second magnetic field in step Sl, and a third magnetic field, wherein the third magnetic field is generated by an eddy current induced in the metal component (8) to be tested; and S3: performing a finite difference operation between the modulating signal and the carrier signal to obtain an original pulsed eddy current testing signal of the metal component (8) to be tested, wherein based on the original pulsed eddy current testing signal, a wall thickness or defect detection of the metal component (8) to be tested is realized by:
measuring the wall thickness of the metal component (8) by extracting a signal feature of a late signal attenuation rate, and detecting a defect of the metal component (8) by performing differentiation with a signal of a defect-free region.
2. The carrier-type pulsed eddy current testing method according to claim 1, wherein the metal component (8) to be tested is a thin plate with a thickness of 2 mm to 40 mm or a pipe with a diameter greater than 25 mm.
3. The carrier-type pulsed eddy current testing method according to claim 1, wherein the square wave excitation in S1 and S2 is 0.1 A to 5 A.
4. A carrier-type pulsed eddy current testing device for implementing the method according to any one of claims 1 to 3, comprising an external control unit, wherein the pulsed eddy current sensor (9) is configured to induce the induced voltage signal when subjected to the square wave excitation, the external control unit is connected to the pulsed eddy current sensor (9) and is configured to provide the square wave excitation to the pulsed eddy current sensor (9) and receive the induced voltage signal from the pulsed eddy current sensor (9), and the metal plate (7) is mounted under the pulsed eddy current sensor (9).
5. The carrier-type pulsed eddy current testing device according to claim 4, wherein the pulsed eddy current sensor (9) comprises a sensor cover (2), an aviation connector (5), a driver coil (6), a pickup coil (4), and a sensor base (3), wherein the sensor cover (2) is mounted on the sensor base (3), the aviation connector (5) is fixed on the sensor cover (2) and is connected to the external control unit, and the driver coil (6) and the pickup coil (4) are both fixed on the sensor base (3) and are connected to the aviation connector (5).
6. The carrier-type pulsed eddy current testing device according to claim 4, wherein the external control unit comprises a computer (15), a main control unit (14), a D/A conversion unit (12), an A/D conversion unit (13), a power amplifier unit (10), and a weak signal conditioning unit (11), wherein the computer (15) is connected to the main control unit (14), the main control unit (14) is connected to the D/A conversion unit (12) and the A/D
conversion unit (13), the D/A conversion unit (12) is connected to the power amplifier unit (10), the A/D conversion unit (13) is connected to the weak signal conditioning unit (11), and the power amplifier unit (10) and the weak signal conditioning unit (11) are both connected to the pulsed eddy current sensor (9), wherein at the time of test, a square wave signal generated by the computer (15) is transmitted to the D/A conversion unit (12) via the main control unit (14), the D/A conversion unit (12) converts the square wave signal into an analog signal and transmits it to the power amplifier unit (10), the power amplifier unit (10) converts the analog signal into the square wave excitation and provides it to the pulsed eddy current sensor (9), the pulsed eddy current sensor (9) receives the induced voltage signal due to action of the square wave excitation, the weak signal conditioning unit (11) obtains the induced voltage signal, amplifies and filters it, and transmits it to the A/D conversion unit (13), the A/D conversion unit (13) converts the amplified and filtered the induced voltage signal into a digital signal and transmits it to the computer (15) via the main control unit (14), and the computer (15) processes the digital signal to obtain relevant information.
conversion unit (13), the D/A conversion unit (12) is connected to the power amplifier unit (10), the A/D conversion unit (13) is connected to the weak signal conditioning unit (11), and the power amplifier unit (10) and the weak signal conditioning unit (11) are both connected to the pulsed eddy current sensor (9), wherein at the time of test, a square wave signal generated by the computer (15) is transmitted to the D/A conversion unit (12) via the main control unit (14), the D/A conversion unit (12) converts the square wave signal into an analog signal and transmits it to the power amplifier unit (10), the power amplifier unit (10) converts the analog signal into the square wave excitation and provides it to the pulsed eddy current sensor (9), the pulsed eddy current sensor (9) receives the induced voltage signal due to action of the square wave excitation, the weak signal conditioning unit (11) obtains the induced voltage signal, amplifies and filters it, and transmits it to the A/D conversion unit (13), the A/D conversion unit (13) converts the amplified and filtered the induced voltage signal into a digital signal and transmits it to the computer (15) via the main control unit (14), and the computer (15) processes the digital signal to obtain relevant information.
7. The carrier-type pulsed eddy current testing device according to claim 4, wherein the metal plate (7) is made of a highly magnetically conductive or highly electrically conductive material.
8. The carrier-type pulsed eddy current testing device according to claim 4, wherein a thickness of the metal plate (7) is 1 mm to 20 mm.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910646239.9 | 2019-07-17 | ||
| CN201910646239.9A CN110361444B (en) | 2019-07-17 | 2019-07-17 | Carrier type pulse eddy current detection method and device |
| PCT/CN2019/111666 WO2021007970A1 (en) | 2019-07-17 | 2019-10-17 | Carrier-type pulsed eddy current testing method and device |
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| Publication Number | Publication Date |
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| CA3089622A1 CA3089622A1 (en) | 2021-01-17 |
| CA3089622C true CA3089622C (en) | 2023-08-29 |
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