A thickness measurement probe and method combining eddy current and ultrasonic waves

Abstract

The present invention belongs to the field of non-destructive testing, and discloses a thickness measurement probe and a thickness measurement method combining eddy current and ultrasonic, which includes a housing; a protective layer is provided at one end of the housing, a delay block and a wafer for generating ultrasonic waves are sequentially provided on the side of the protective layer close to the housing, silver plating layers are provided on both the upper and lower surfaces of the wafer, and wafer electrode leads are provided on the silver plating layers; a through hole is opened on the protective layer, a housing is provided in the through hole, a magnetic core is provided inside the housing, an eddy current coil for eddy current detection is sleeved on the magnetic core, and coil leads are provided on the eddy current coil; the wafer electrode leads and the coil leads both penetrate out of the housing and are connected to interfaces provided on the outer wall of the housing. By integrating the eddy current and ultrasonic probes on the same probe, the thickness of the matrix of the turbine blade to be tested, the thickness of the TBCs ceramic layer, and the thickness of the TBCs metal layer can be obtained with only one detection, overcoming the position error caused by two measurements and significantly improving the measurement efficiency.

Description

Technical Field

[0001] The invention belongs to the field of nondestructive testing, and relates to a thickness measurement probe and a thickness measurement method combining eddy current and ultrasonic wave. Background Technique

[0002] The turbine blade of a gas turbine is a key component that converts the energy of high-temperature gas into the work done by the gas turbine. As a rotating component, the turbine blade needs to bear the combined action of loads such as high temperature, centrifugal stress, gas flow impact force, and vibration stress during operation. In order to reduce the working temperature of the turbine blade substrate, a thermal barrier coating (TBCs) is generally covered on the surface of the turbine blade substrate, which can effectively reduce the working temperature of the turbine blade substrate and slow down thermal corrosion, etc. During the manufacturing and service stages of the turbine blade, it is necessary to monitor the thickness and uniformity of the turbine blade substrate and its TBCs to judge whether the manufacturing quality is qualified and whether the service state is healthy, etc. Among them, the thickness of the turbine blade substrate is generally between 10 and 30 mm, the thickness of the TBCs ceramic layer is between 150 and 300 μm, and the thickness of the TBCs metal layer is between 100 and 200 μm.

[0003] Currently, the commonly used thickness measurement method is to measure the thickness of the turbine blade substrate and the metal layer by the ultrasonic echo method, and measure the thickness of the TBCs ceramic layer by the eddy current method. However, the above detection process has the following three deficiencies: 1. The ultrasonic measurement of the turbine blade substrate thickness and the eddy current measurement of the TBCs coating thickness are carried out separately, and the detection efficiency is relatively low; 2. Since the measurements are not carried out simultaneously, it is difficult to make the positions, coupling conditions, and probe pressing forces of the two measurements before and after completely consistent, and the measured thicknesses of the turbine blade substrate and TBCs are often not the values at the same position; 3. The commonly used portable eddy current thickness gauge can only measure the thickness of the TBCs ceramic layer and cannot measure the thickness of the TBCs metal layer. Summary of the Invention

[0004] The purpose of the invention is to overcome the disadvantages of low detection efficiency and inaccurate detection results in the prior art when measuring the thickness of the turbine blade substrate and the TBCs ceramic layer, and to provide a thickness measurement probe and a thickness measurement method combining eddy current and ultrasonic wave.

[0005] To achieve the above purpose, the invention adopts the following technical solutions:

[0006] On the one hand, a thickness measurement probe combining eddy current and ultrasonic wave of the invention includes a housing;

[0007] A protective layer is arranged at one end of the housing. A delay block and a wafer for generating ultrasonic waves are sequentially arranged on the side of the protective layer close to the housing. Silver plating layers are arranged on the upper and lower surfaces of the wafer, and wafer electrode leads are arranged on the silver plating layers;

[0008] A through hole is formed in the protective layer, a housing is arranged in the through hole, a magnetic core is arranged inside the housing, an eddy current coil for eddy current detection is sleeved on the magnetic core, and a coil lead is arranged on the eddy current coil;

[0009] The wafer electrode lead and the coil lead both pass through the outer shell and are connected to the interfaces arranged on the outer wall of the outer shell.

[0010] A further improvement of the thickness measurement probe with combined eddy current and ultrasonic waves of the present invention lies in:

[0011] A backing made of epoxy resin and tungsten powder is arranged on the inner wall of the outer shell.

[0012] The eddy current coil includes an excitation coil and a detection coil, and the excitation coil and the detection coil are sleeved on the magnetic core at intervals.

[0013] The material of the protective layer is plexiglass.

[0014] The thickness of the protective layer is one-fourth of the wavelength of the center frequency of the ultrasonic waves generated by the wafer.

[0015] The interface is a BNC interface or a LEMO interface.

[0016] The material of the wafer is a piezoelectric composite material, and the center frequency is 5 - 10 MHz.

[0017] The material of the magnetic core is soft ferrite, the materials of the housing and the outer shell are aluminum or stainless steel respectively, and the wafer electrode lead and the coil lead are both made of copper wire.

[0018] The diameter of the magnetic core is 1 - 2 mm, the delay block is annular, and the height is 5 - 10 mm.

[0019] In the second aspect of the present invention, a thickness measurement method for a thickness measurement probe with combined eddy current and ultrasonic waves, which is applied to a turbine blade with a TBCs coating, includes the following steps:

[0020] S1: Apply an ultrasonic coupling agent on the turbine blade to be tested and then contact it with the thickness measurement probe;

[0021] S2: Connect the interface of the thickness measurement probe to the test system, and excite the eddy current coil through the test system to perform eddy current detection to obtain the thickness of the TBCs ceramic layer of the turbine blade to be tested;

[0022] S3: Excite the wafer to generate ultrasonic waves through the test system to obtain the propagation times of the ultrasonic echoes of the interface between the TBCs ceramic layer and the TBCs metal layer, the interface between the TBCs metal layer and the substrate, and the bottom surface of the substrate of the turbine blade to be tested;

[0023] S4: Based on the ultrasonic echo sound velocity of the TBCs metal layer and the ultrasonic echo sound velocity of the turbine blade substrate, and combining the propagation time of the ultrasonic echoes at the interface between the TBCs ceramic layer and the TBCs metal layer, the interface between the TBCs metal layer and the substrate, and the bottom surface of the substrate, the thickness of the TBCs metal layer and the thickness of the substrate are obtained.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The thickness measurement probe combining eddy current and ultrasound of the present invention integrates the eddy current and ultrasound probes on the same probe. Only one detection is required to obtain the thickness of the turbine blade substrate to be tested, the thickness of the TBCs ceramic layer, and the thickness of the TBCs metal layer. At the same time, since the thickness values are obtained in one measurement, it is strictly ensured that the measurement values are obtained at the same position, overcoming the position error caused by two measurements. In addition, it also overcomes the measurement error caused by the different coupling states at the same position due to two measurements, realizing the efficient and accurate measurement of the thickness of the turbine blade substrate, the thickness of the TBCs ceramic layer, and the thickness of the TBCs metal layer.

[0026] Further, a backing made of epoxy resin plus tungsten powder is provided on the inner wall of the housing, filling the entire inner wall of the housing, effectively absorbing the reverse ultrasonic waves emitted by the wafer, effectively suppressing the after-vibration of the wafer, reducing the number of single pulse cycles, and improving the longitudinal resolution of ultrasonic detection.

[0027] Further, the magnetic core is made of soft ferrite, making the resistivity, medium and high frequency losses, and cost lower.

[0028] Further, the protective layer is made of plexiglass, and the thickness is about one-fourth of the wavelength of the center frequency of the ultrasonic wave, thereby obtaining a higher ultrasonic transmission rate.

[0029] Further, the wafer is made of piezoelectric composite material, and the center frequency is 5 - 10 MHz, thereby achieving the balance between ultrasonic attenuation and longitudinal resolution and improving the detection accuracy.

[0030] Further, the diameter of the magnetic core is 1 - 2 mm, the delay block is designed in a ring shape, and the height is 5 - 10 mm. The diameter of the magnetic core ensures that the thickness range of eddy current measurement is as small as possible, thus ensuring the measurement accuracy. The height design of the delay block effectively avoids the interference of the near field area on ultrasonic thickness measurement.

[0031] The thickness measurement method combining eddy current and ultrasound of the present invention measures each thickness at the same position, which can ensure that the thicknesses of the TBCs ceramic layer, the TBCs metal layer, and the substrate of the turbine blade to be tested do not change due to position changes, eliminating measurement errors caused by position changes, coupling conditions, and probe pressing force, etc., and greatly improving the test accuracy. Description of the Drawings

[0032] Figure 1 Schematic diagram of the thickness measurement probe structure combining eddy current and ultrasound according to an embodiment of the present invention;

[0033] Figure 2 Top view of the thickness measurement probe structure combining eddy current and ultrasound according to an embodiment of the present invention;

[0034] Figure 3 Schematic diagram of the working principle of the thickness measurement probe combining eddy current and ultrasound according to an embodiment of the present invention.

[0035] Wherein: 1 - Eddy current probe; 2 - Ultrasound probe; 3 - Housing; 4 - Magnetic core; 5 - Eddy current coil; 501 - Excitation coil; 502 - Detection coil; 6 - Coil lead; 7 - Protective layer; 8 - Outer shell; 9 - Interface; 10 - Wafer electrode lead; 11 - Backing; 12 - Wafer; 13 - Delay block. Specific implementation manners

[0036] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above accompanying drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0038] The present invention will be further described in detail below with reference to the accompanying drawings:

[0039] See Figure 1 and 2, in an embodiment of the present invention, a thickness measurement probe combining eddy current and ultrasonic is provided to simultaneously and accurately measure the thickness of the substrate, the TBCs ceramic layer, and the TBCs metal layer of the turbine blade to be tested, and significantly improve the efficiency of thickness measurement, thereby efficiently and accurately detecting the thickness of the substrate, the TBCs ceramic layer, and the TBCs metal layer of the turbine blade to be tested.

[0040] Specifically, the thickness measurement probe combining eddy current and ultrasonic includes a housing 8; a protective layer 7 is provided at one end of the housing 8. A delay block 13 and a wafer 12 for generating ultrasonic waves are sequentially provided on the side of the protective layer 7 close to the housing 8. Silver plating layers are provided on both the upper and lower surfaces of the wafer 12, and wafer electrode leads 10 are provided on the silver plating layers; a through hole is opened on the protective layer 7, and a housing 3 is provided in the through hole. A magnetic core 4 is provided inside the housing 3, an eddy current coil 5 for eddy current detection is sleeved on the magnetic core 4, and a coil lead 6 is provided on the eddy current coil 5; the wafer electrode lead 10 and the coil lead 6 both pass through the housing 8 and are connected to an interface 9 provided on the outer wall of the housing 8.

[0041] Among them, the housing 3, the magnetic core 4, the eddy current coil 5, and the coil lead 6 form an eddy current probe 1, and the protective layer 7, the housing 8, the wafer electrode lead 10, the wafer 12, and the delay block 13 form an ultrasonic probe 2. A through hole is opened at the exact center of the ultrasonic probe 2 to accommodate the eddy current probe 1.

[0042] The thickness measurement probe combining eddy current and ultrasonic of the present invention integrates the eddy current and ultrasonic probes on the same probe, and the thickness of the substrate of the turbine blade to be tested, the thickness of the TBCs ceramic layer, and the thickness of the TBCs metal layer can be obtained with only one detection. At the same time, since the thickness values are obtained in one measurement, it is strictly ensured that the measurement values are obtained at the same position, overcoming the position error caused by two measurements. In addition, the measurement error caused by the different coupling states of two measurements at the same position is also overcome, realizing the efficient and accurate measurement of the thickness of the substrate of the turbine blade, the thickness of the TBCs ceramic layer, and the thickness of the TBCs metal layer.

[0043] Preferably, in another embodiment, the shape of the housing 3 is cylindrical, and the material is selected from aluminum or stainless steel to achieve better electromagnetic shielding and reduce the influence of the ultrasonic emission circuit on the eddy current signal.

[0044] Preferably, in another embodiment, the material of the magnetic core 4 is selected as soft ferrite. Preferably, the soft ferrite can be Mn-Zn ferrite, which makes the resistivity, medium and high frequency loss, and cost lower.

[0045] Preferably, in another embodiment, the eddy current coil 5 includes an excitation coil 501 and a detection coil 502. Among them, the diameter of the coil copper wire can be 0.05 - 0.1 mm, which can achieve the balance between the performance of the wound coil and the size of the probe.

[0046] Preferably, in another embodiment, the interface 9 can be selected from interfaces with good versatility such as BNC interface or LEMO interface. Among them, the BNC interface refers to a coaxial cable interface, which is used for connecting 75-ohm coaxial cables, providing two channels for receiving RX and transmitting TX. It is used for connecting unbalanced signals, thereby improving the versatility of the thickness measurement probe and facilitating use.

[0047] Preferably, in another embodiment, the material of the protective layer 7 is selected as plexiglass, and the thickness is about one-fourth of the wavelength of the ultrasonic wave with the center frequency of the ultrasonic probe 2, thereby obtaining a relatively high ultrasonic transmission rate.

[0048] Preferably, in another embodiment, the outer shell 8 is cylindrical, made of aluminum or stainless steel, with good electrical conductivity, and can be used as the negative electrode of the wafer 12.

[0049] Preferably, in another embodiment, the material of the wafer electrode lead 10 is copper wire with good conductivity.

[0050] Preferably, in another embodiment, a backing 11 made of epoxy resin and tungsten powder is provided on the inner wall of the outer shell 8, filling the entire inner wall of the outer shell 8, effectively absorbing the reverse ultrasonic waves emitted by the wafer 12, effectively suppressing the after-vibration of the wafer 12, reducing the number of single pulse cycles, and improving the longitudinal resolution of the ultrasonic probe 2.

[0051] Preferably, in another embodiment, the wafer 12 is annular, and there is a silver-plated layer on each of the upper and lower surfaces, serving as the positive and negative electrodes of the wafer 12.

[0052] Preferably, in another embodiment, the material of the wafer 12 is a piezoelectric composite material, and the center frequency is 5 - 10 MHz, thereby achieving a balance between ultrasonic attenuation and longitudinal resolution and improving the detection accuracy.

[0053] Preferably, in another embodiment, the diameter of the magnetic core 4 is 1 - 2 mm, the delay block 13 is designed in a ring shape, sleeved outside the housing 3, and the height is 5 - 10 mm. The diameter of the magnetic core 4 ensures that the thickness range of eddy current measurement is as small as possible, thereby ensuring the measurement accuracy. The height design of the delay block 13 effectively avoids the interference of the near field on ultrasonic thickness measurement.

[0054] See Figure 3 , in another embodiment of the present invention, a thickness measurement method combining eddy current and ultrasound is provided. Based on the above-mentioned thickness measurement probe combining eddy current and ultrasound, it is applied to a turbine blade with a TBCs coating. The thickness measurement method combining eddy current and ultrasound includes the following steps:

[0055] S1: Apply ultrasonic coupling agent on the turbine blade to be tested and then contact it with the thickness measurement probe. S2: Connect the interface of the thickness measurement probe to the test system, and use the test system to excite the eddy current coil 5 to perform eddy current detection, so as to obtain the thickness of the TBCs ceramic layer of the turbine blade to be tested. S3: Use the test system to excite the wafer 12 to generate ultrasonic waves, and obtain the propagation time of the ultrasonic echoes at the interface between the TBCs ceramic layer and the TBCs metal layer, the interface between the TBCs metal layer and the substrate, and the bottom surface of the substrate of the turbine blade to be tested. S4: According to the ultrasonic echo sound velocity of the TBCs metal layer and the ultrasonic echo sound velocity of the substrate, combined with the propagation time of the ultrasonic echoes at the interface between the TBCs ceramic layer and the TBCs metal layer, the interface between the TBCs metal layer and the substrate, and the bottom surface of the substrate, obtain the thickness of the TBCs metal layer and the thickness of the substrate.

[0056] Specifically, apply ultrasonic coupling agent on the turbine blade to be tested with TBCs coating, place the test probe on it, connect the interface to the existing test system, and sequentially excite the ultrasonic probe 2 and the eddy current probe 1 through the test system, the wafer electrode lead 10 and the coil lead 6. The wafer 12 vibrates under the drive of the positive and negative pulse voltages, thereby generating ultrasonic waves and passing through the delay block 13 and the protective layer 7, and being transmitted into the TBCs ceramic layer, the TBCs metal layer and the substrate of the turbine blade to be tested through the coupling agent. Ultrasonic echoes B1, B2 and B3 are respectively generated at the interface between the TBCs ceramic layer and the TBCs metal layer, the interface between the TBCs metal layer and the substrate, and the bottom surface of the substrate of the turbine blade to be tested, and the echo propagation times t1, t2 and t3 at this time are read out. The propagation times of the sound waves in the TBCs ceramic layer, the TBCs metal layer and the substrate are t1, t2 - t1 and t3 - t2 respectively. At this time, the thickness calculated by multiplying the nominal sound velocity by the time is the nominal thickness, rather than the actual thickness.

[0057] This is because the sound velocities will vary due to different spraying processes of the TBCs ceramic layer, and the sound velocity of the TBCs ceramic layer is quite different from that of the TBCs metal layer and the substrate. Therefore, in the present invention, the actual thickness of the TBCs ceramic layer is measured by the eddy current method, the actual propagation time of the ultrasonic waves in the TBCs ceramic layer is measured by the ultrasonic method, and the actual sound velocity of the TBCs ceramic layer is calculated. Since the material compositions and processing techniques of the TBCs metal layer and the substrate are relatively stable and there are mature sound velocity data for reference, they can be used as the actual sound velocities for ultrasonic thickness measurement of the TBCs metal layer and the substrate.

[0058] First, use the eddy current probe 1 and utilize the lift-off effect to measure the actual thickness H of the TBCs ceramic layer 1a , and calculate the actual sound velocity v of the ceramic layer 1a = H 1a / t1. Then, according to the formula H = v·t, substitute the actual sound velocities v of the TBCs metal layer and the substrate of the turbine blade to be tested2a and v 3a Substitute into the calculation to obtain the actual thicknesses H of the TBCs metal layer and the substrate of the turbine blade to be tested 2a and H 3a .

[0059] Since the measurements are taken at the same location, it can be ensured that the thicknesses of the TBCs ceramic layer, the TBCs metal layer, and the substrate of the turbine blade to be tested do not change due to position variations, eliminating measurement errors caused by position changes, coupling conditions, and probe pressing force, etc., and greatly improving the test accuracy.

[0060] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modifications made on the basis of the technical solution according to the technical idea proposed by the present invention fall within the protection scope of the claims of the present invention.

Claims

1. A thickness measurement method for a thickness measurement probe based on the combination of eddy current and ultrasound, characterized in that, The thickness measuring probe combining eddy current and ultrasonic includes a housing (8); a protective layer (7) is arranged at one end of the housing (8), a delay block (13) and a wafer (12) for generating ultrasonic waves are sequentially arranged on the side of the protective layer (7) close to the housing (8), silver plating layers are arranged on the upper and lower surfaces of the wafer (12), and wafer electrode leads (10) are arranged on the silver plating layers; a through hole is formed in the protective layer (7), a housing (3) is arranged in the through hole, a magnetic core (4) is arranged inside the housing (3), an eddy current coil (5) for eddy current detection is sleeved on the magnetic core (4), and a coil lead (6) is arranged on the eddy current coil (5); the diameter of the magnetic core (4) is 1-2 mm; the wafer electrode leads (10) and the coil leads (6) both pass through the housing (8) and are connected to an interface (9) arranged on the outer wall of the housing (8); The thickness measuring method is applied to a turbine blade with a TBCs coating and includes the following steps: S1: Apply ultrasonic coupling agent to the turbine blade to be tested and then contact it with the thickness measuring probe; S2: Connect the interface of the thickness measuring probe to the test system, and excite the eddy current coil (5) through the test system to perform eddy current detection to obtain the thickness of the TBCs ceramic layer of the turbine blade to be tested; S3: Excite the wafer (12) through the test system to generate ultrasonic waves, and obtain the propagation time of the ultrasonic echoes of the interface between the TBCs ceramic layer and the TBCs metal layer, the interface between the TBCs metal layer and the substrate, and the bottom surface of the substrate of the turbine blade to be tested; S4: According to the ultrasonic echo sound velocity of the TBCs metal layer and the ultrasonic echo sound velocity of the turbine blade substrate, combined with the propagation time of the ultrasonic echoes of the interface between the TBCs ceramic layer and the TBCs metal layer, the interface between the TBCs metal layer and the substrate, and the bottom surface of the substrate, obtain the thickness of the TBCs metal layer and the thickness of the substrate.

2. The thickness measurement method of the thickness measurement probe based on the combination of eddy current and ultrasound according to claim 1, characterized in that, A backing (11) made of epoxy resin plus tungsten powder is arranged on the inner wall of the housing (8).

3. The thickness measurement method of the thickness measurement probe based on the composite of eddy current and ultrasound according to claim 1, characterized in that, The eddy current coil (5) includes an excitation coil (501) and a detection coil (502), and the excitation coil (501) and the detection coil (502) are sleeved on the magnetic core (4) at intervals.

4. The thickness measurement method of the thickness measurement probe based on the composite of eddy current and ultrasound according to claim 1, characterized in that, The material of the protective layer (7) is plexiglass.

5. The thickness measurement method of the thickness measurement probe based on the combination of eddy current and ultrasound according to claim 1, wherein, The thickness of the protective layer (7) is one-fourth of the wavelength of the center frequency of the ultrasonic waves generated by the wafer (12).

6. The thickness measurement method of the thickness measurement probe based on the composite of eddy current and ultrasound according to claim 1, characterized in that, The interface (9) is a BNC interface or a LEMO interface.

7. The thickness measurement method of the thickness measurement probe based on the composite of eddy current and ultrasound according to claim 1, characterized in that, The material of the wafer (12) is a piezoelectric composite material, and the center frequency is 5-10 MHz.

8. The thickness measurement method of the thickness measurement probe based on the combination of eddy current and ultrasound according to claim 1, characterized in that, The material of the magnetic core (4) is soft ferrite, the materials of the housing (3) and the housing (8) are aluminum or stainless steel respectively, and the wafer electrode leads (10) and the coil leads (6) are both made of copper wires.

9. The thickness measurement method of the thickness measurement probe based on the composite of eddy current and ultrasound according to claim 1, characterized in that, The delay block (13) is annular, and the height is 5-10 mm.

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