Corrosion thinning online monitoring method and system for aerospace hot-end metal component simulation test platform

Abstract

The application discloses an aerospace hot-end metal component simulation test platform corrosion thinning online monitoring method and system, wherein the method comprises the following steps: using laser vertical incidence of the measured hot-end metal component to excite ultrasonic waves; receiving the ultrasonic echo signal through the electromagnetic ultrasonic probe arranged on the surface of the measured hot-end metal component; extracting a plurality of resonance frequencies and corresponding resonance orders based on the ultrasonic echo signal; selecting adjacent resonance frequencies and non-adjacent resonance frequencies to calculate a plurality of groups of first-order resonance frequencies with different accuracies, performing weighted average on the plurality of groups of first-order resonance frequencies, and obtaining a first-order resonance frequency weighted average value and a weighted uncertainty; and further calculating the thickness of the measured hot-end metal component based on the relationship between the resonance frequency and the thickness. The application realizes online monitoring of the corrosion thinning of the high-temperature alloy material, and can overcome the flutter condition. A method for measuring uncertainty with different accuracies is proposed, and all effective data are used as much as possible to reduce the measurement error.

Description

Technical Field

[0001] This invention relates to the field of metal thickness detection technology, and in particular to an online monitoring method and system for corrosion thinning of aerospace hot-end metal components using a simulation test platform. Background Technology

[0002] High-temperature alloys, due to their excellent physical and chemical properties under high-temperature conditions, are widely used in aerospace, energy, and petrochemical fields. In the aerospace field, high-temperature alloys are among the most crucial materials in aero-engines. In modern advanced aero-engines, high-temperature alloys account for 40% to 60% of the total material usage. Turbine blades and exhaust nozzles, as important components of aero-engines, frequently operate in harsh environments such as high temperature, high pressure, and strong corrosion, making them prone to corrosion and thinning defects. To ensure the reliability of aircraft operating at high altitudes, a series of reliability tests are often conducted before delivery, simulating outdoor high-temperature erosion service environments. During testing, engines and their components must withstand complex dynamic loads such as vibration, impact, noise, and pressure pulsation generated by the system itself. How to conduct real-time online monitoring of turbine blades and engine exhaust nozzles during hot-fire testing is a challenging problem that needs to be solved.

[0003] Traditional piezoelectric ultrasonic testing requires a coupling agent (such as machine oil, water glass, or glycerin) between the probe and the workpiece. High temperatures can cause this coupling agent to evaporate, and traditional ultrasonic probes are prone to damage when in contact with high-temperature alloy materials, posing safety hazards. Currently available high-temperature probes can only perform brief tests at 550°C, making continuous high-temperature testing difficult. Air-coupled ultrasonic probes use air as the coupling agent, allowing for non-contact testing, but their lower transduction efficiency makes them unsuitable for high-temperature testing.

[0004] Laser ultrasonic resonance testing is a non-contact thickness measurement method. Compared with traditional ultrasonic testing methods, pulsed lasers are non-contact, require no coupling agent, are suitable for high-temperature testing, and greatly improve operational safety, exhibiting good high-temperature performance. Laser ultrasonic testing allows for rapid scanning because the beam has zero inertia and eliminates the viscous resistance of coupling agents. Laser-excited ultrasound is largely unaffected by material properties, and the pulse signal has a very wide bandwidth, reaching tens of megahertz. Compared to the widely studied EMR (electromagnetic acoustic resonance), it eliminates the need to adjust the resonant frequency range and removes the frequency sweep operation to obtain a complete resonant spectrum, reducing operational difficulty and making it suitable for workpieces with significant thickness variations. Ultrasonic thickness measurement techniques include time-domain and frequency-domain techniques. Time-domain thickness measurement typically uses the transit time and wave velocity of ultrasound waves in the thickness direction within the pipe to calculate the pipe thickness. While simple in principle and easy to operate, time-domain thickness measurement is widely used in thick-walled pipe testing. However, for thin-walled pipes, where the thickness is small, echoes tend to overlap, resulting in lower accuracy and making it difficult to apply to thin-walled pipe testing. Frequency domain thickness measurement technology allows for sufficiently long excitation acoustic waves, ideally in the form of continuous wave excitation, but also in the form of broadband pulse excitation. Resonance thickness measurement is a type of frequency domain thickness measurement. Ultrasonic resonance thickness measurement is theoretically simple and mature, widely used, and theoretically boasts very high measurement accuracy. It is highly sensitive to small thickness changes and has significant advantages for monitoring thinned components. However, traditional laser interferometers require high standards for the working environment and surface smoothness of the component when receiving signals. Furthermore, the component and interferometer often need to remain relatively stationary during operation, which is difficult to achieve in many in-service testing applications.

[0005] The current challenges in detecting turbine blades and engine exhaust nozzles in high-temperature erosion simulation experiments are: ① High-temperature erosion simulation experiments are often conducted in high-temperature environments. Conventional sensors cannot directly monitor high-temperature alloy materials, and many high-temperature sensors with temperatures above 550℃ are still in the experimental research stage, are expensive, and unsuitable for large-scale testing. ② In high-temperature erosion simulation experiments, engine hot-running tests can cause the workpieces to experience flutter. Overcoming this flutter state for continuous high-temperature monitoring is also a problem we must consider. ③ How to achieve reliable and accurate high signal-to-noise ratio monitoring while ensuring energy conversion efficiency.

[0006] The following patents currently exist regarding high-temperature laser ultrasonic testing:

[0007] Invention patent application number: CN201910982656.0 discloses a laser ultrasonic measurement method for the thickness of high-temperature metallic materials. Based on laser ultrasonic technology, the method achieves thickness measurement of multiple samples within a temperature range from room temperature to 480°C by high-precision detection of the propagation time of longitudinal wave pulse signals within the sample.

[0008] Utility model patent application number: CN202121614687.X discloses a laser ultrasonic non-contact non-destructive testing device, which solves the problems of traditional testing being unable to detect irregularly shaped workpieces and unable to detect in high-temperature environments, and eliminates the use of coupling agent in the traditional piezoelectric ultrasonic testing process; this method realizes true non-contact non-destructive testing and expands the scope of the field of non-destructive testing.

[0009] Utility model patent application number: CN202121898224.0 discloses an ultrasonic transducer that combines laser and electromagnetic technology, which does not require a coupling agent and effectively makes up for the shortcomings of traditional piezoelectric ultrasonic transducer technology; it solves the problems of detection in long-distance dangerous environments and high-temperature conditions under harsh environments such as high temperature, high pressure, strong corrosion and radiation.

[0010] Utility model patent application number: CN201320402743.2 discloses a non-contact laser-electromagnetic ultrasonic probe device. The EMAT sensor is characterized by comprising an upper cooling shell and a lower cooling shell made of metal, and using circulating water to maintain normal operating temperature.

[0011] Invention patent application number CN202111136536.2 discloses an online detection probe, system and method for ultra-high temperature metallic materials. The probe shell and the detection coil, excitation coil, laser incident channel, first water inlet channel, two second water inlet channels and the cavity between the corundum sheet form a circulating cooling channel, which can play the role of circulating water cooling. At the same time, the use of a coil-only receiving probe can realize continuous detection at high temperature.

[0012] Invention patent application number: CN202111136565.9 discloses an online detection probe, system and method for ultra-high temperature ferromagnetic metal castings and forgings. It is a permanent magnet-free ring coil EMAT sensor based on the principle of enhancing longitudinal wave energy through surface constraint mechanism and the method of transient water cooling of the test piece and ring coil enhancing the contribution ratio of magnetostriction. The probe is equipped with a water film cooling channel and a light guide arm. The water film can play the role of surface constraint, which greatly enhances the amplitude of longitudinal wave vibration along the thickness direction of the test piece. The light guide arm is used for the passage of laser source.

[0013] The aforementioned patents propose methods such as electromagnetic ultrasonic testing and laser electromagnetic ultrasonic testing for the inspection of metallic materials under high-temperature environments, and also design high-temperature sensors. Some of these methods can achieve continuous high-temperature testing under conventional conditions, but they cannot perform high-precision high-temperature testing on turbine blades and engine exhaust nozzles that are simultaneously under flutter conditions. Therefore, the laser electromagnetic ultrasonic resonance method proposed in this patent can perform continuous high-temperature testing of these two special components under flutter conditions with single-sided erosion thinning, and features high measurement accuracy. Summary of the Invention

[0014] To overcome the technical barriers encountered in the testing and inspection of turbine blades and engine exhaust nozzles under flutter conditions, this invention provides an online monitoring method and system for corrosion thinning of aerospace hot-end metal components using a simulated testing platform. The method employs laser electromagnetic ultrasonic resonance for online monitoring of corrosion thinning in high-temperature alloy materials. It features a small blind zone, wide spectrum, high resolution, high energy, is not limited by temperature, and has high accuracy in detecting minute thickness changes in high-temperature alloy materials. It can overcome flutter conditions and achieve thickness measurement of workpieces up to 10 mm, meeting the application requirements for online monitoring of corrosion thinning during the testing of turbine blades and engine exhaust nozzles.

[0015] Firstly, a method for online monitoring of corrosion thinning on a simulated test platform for aerospace hot-end metal components is provided, comprising the following steps:

[0016] S1: Use a laser to be incident perpendicularly on the hot metal part being tested to excite ultrasonic waves;

[0017] S2: Receive ultrasonic echo signals through an electromagnetic ultrasonic probe placed on the surface of the metal component being tested at the hot end;

[0018] S3: Extract multiple resonant frequencies and their corresponding resonant orders based on ultrasonic echo signals;

[0019] S4: Select adjacent and non-adjacent resonant frequencies to calculate multiple sets of first-order resonant frequencies with unequal precision. Perform a weighted average on these multiple sets of first-order resonant frequencies to obtain the weighted average value of the first-order resonant frequencies. and weighted uncertainty

[0020] S5: The thickness δ of the hot-end metal component being measured is calculated using the following formula:

[0021]

[0022]

[0023] In the formula, c is the ultrasonic wave velocity in the material of the hot-end metal component being measured, and f is the measured value of the first-order resonant frequency.

[0024] Furthermore, step S4 specifically includes:

[0025] The first set of first-order resonant frequencies is obtained by selecting multiple pairs of adjacent resonant frequencies;

[0026] The second set of first-order resonant frequencies is obtained by selecting multiple pairs of non-adjacent resonant frequencies;

[0027] The third set of first-order resonant frequencies was obtained by selecting multiple resonant frequencies and calculating them using the method of successive differences.

[0028] The three sets of first-order resonant frequencies are weighted and averaged to obtain the weighted average value of the first-order resonant frequencies. The calculation formula is as follows:

[0029]

[0030] In the formula, m and p i X i Let n and p represent the number of first-order resonant frequencies, their weights, and the i-th first-order resonant frequency in the first group of first-order resonant frequencies, respectively; j Y j Let l and p represent the number of first-order resonant frequencies, their weights, and the j-th first-order resonant frequency in the second group of first-order resonant frequencies, respectively; k Z k These represent the number of first-order resonant frequencies, their weights, and the kth first-order resonant frequency in the third group of first-order resonant frequencies, respectively.

[0031] Weighted uncertainty The following formula is used to calculate:

[0032]

[0033]

[0034]

[0035]

[0036] In the formula, v i v j v k These represent the residual errors of the first-order resonant frequencies in the first group, the second group, and the third group, respectively.

[0037] Furthermore, the weighting ratio of the three sets of first-order resonant frequencies is:

[0038] p i :p j :p k =a:b:c

[0039] Where a, b, and c represent the number of resonant frequencies used when calculating the first-order resonant frequencies in the first group, the second group, and the third group, respectively.

[0040] Furthermore, the resonant frequency extracted in step S3 is located in the range of 1MHz to 10MHz.

[0041] Furthermore, the resonant frequencies extracted in step S3 are all longitudinal wave resonant frequencies.

[0042] In a second aspect, an online monitoring system for corrosion thinning of a simulated test platform for aerospace hot-end metal components is provided, which is used to realize the online monitoring method for corrosion thinning of a simulated test platform for aerospace hot-end metal components as described in any of the first aspects. The system includes a laser excitation module and a host computer, a data acquisition card, a detection circuit and an electromagnetic ultrasonic probe connected in sequence.

[0043] The host computer is configured to execute steps S3 to S5.

[0044] Furthermore, the electromagnetic ultrasonic probe includes a housing, a detection coil, a corundum sheet, and a signal interface;

[0045] The corundum sheet is disposed at the bottom of the housing, and the detection coil is disposed at the top of the corundum sheet; the signal interface is disposed on the housing and is electrically connected to the detection coil.

[0046] Furthermore, the detection circuit includes a switching module, a low-voltage module, an impedance matching module, an echo detection module, and a sampling current module; the switching module, the low-voltage module, and the input terminal of the detection coil are electrically connected in sequence, the output terminal of the detection coil is electrically connected to the impedance matching module and the echo detection module respectively, and the sampling current module is electrically connected to the impedance matching module.

[0047] Furthermore, the laser excitation module includes a pulsed laser, a laser fiber, and a focusing lens connected in sequence.

[0048] Furthermore, when the focusing lens is a convex lens, the detection coil is a spiral coil; when the focusing lens is a prism, the detection coil is a butterfly coil.

[0049] This invention proposes a method and system for online monitoring of corrosion thinning in a simulated test platform for hot-end metal components in aerospace applications. It utilizes a laser-ultrasonic resonance thickness measurement method to achieve online monitoring of corrosion thinning in high-temperature alloy materials under high-temperature conditions. This method overcomes flutter conditions and meets the requirements for online monitoring of corrosion thinning during turbine blade and engine exhaust nozzle testing. This invention also proposes a method to address the uncertainty of unequal precision measurement using the laser-ultrasonic resonance method, minimizing measurement errors by utilizing all available data. Furthermore, the proposed online corrosion thinning monitoring system utilizes laser fiber technology, enabling the laser output direction to be changed with low energy attenuation, compensating for the large size of pulsed lasers and achieving real-time online monitoring of complex areas. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 This is a schematic diagram of the laser ultrasonic resonance thickness measurement principle provided in an embodiment of the present invention;

[0052] Figure 2 This is a flowchart of the online monitoring method for corrosion thinning of aerospace hot-end metal component simulation test platform provided in this embodiment of the invention;

[0053] Figure 3 This is the echo frequency domain diagram of thickness measurement using the laser ultrasonic resonance method provided in this embodiment of the invention;

[0054] Figure 4 This is a schematic diagram of the corrosion thinning online monitoring system of the aerospace hot-end metal component simulation test platform provided in this embodiment of the invention;

[0055] Figure 5 This is a schematic diagram of the detection circuit provided in an embodiment of the present invention;

[0056] Figure 6 This is a schematic diagram of the electromagnetic ultrasonic probe structure provided in an embodiment of the present invention. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0058] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," "center," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intervening element. The terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or order. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.

[0059] The present invention proposes an online monitoring method and system for corrosion thinning of aerospace hot-end metal components simulation test platform. It utilizes laser electromagnetic ultrasonic technology and integrates laser ultrasonic resonance method to realize continuous monitoring of high-temperature corrosion thinning of engine turbine blades and tail nozzles under high-temperature flutter conditions.

[0060] This invention is based on the laser-electromagnetic ultrasonic resonance thickness measurement method. To clearly understand the technical solution of this invention, the basic principle of the laser-electromagnetic ultrasonic resonance thickness measurement method is explained as follows:

[0061] The process of laser-generated ultrasound is the interaction between a pulsed laser and the surface medium of the material being tested, and it can be divided into two mechanisms: thermoelastic and ablation. This invention preferably employs the ablation mechanism for laser-excited ultrasound. Compared to the thermoelastic mechanism, laser ultrasound under the ablation mechanism has the characteristics of large amplitude, and the longitudinal wave sound field is directed towards the interior of the tested component and parallel to the normal direction of the tested component. Although the average single ablation depth of the ablation mechanism is 0.7 μm, this ablation amount is extremely small and can be ignored. Figure 1 The diagram shown illustrates the principle of laser ultrasonic resonant thickness measurement. When the laser power is greater than 10... 7 W / cm 2When a thin layer on the surface of a material is irradiated by a laser, it will melt or even generate plasma in a very short time (some atoms gain enough energy to break free from the attraction between atoms, detach from the material surface, and form plasma on the surface of the material). The normal force of the plasma on the tested component will cause stress waves to propagate inside the material, that is, to generate ultrasonic waves in the material. Longitudinal waves, transverse waves and Rayleigh waves will exist simultaneously inside the material.

[0062] Ultrasonic resonance thickness measurement involves transmitting ultrasonic waves to the component under test, performing a Fourier transform on the repeatedly superimposed resonant signals generated within the component, determining the frequency, and then calculating the thickness of the component from the relationship between the frequency and the thickness of the component. This method offers advantages such as no need for coupling agent, high measurement accuracy, and strong capability for measuring thin workpieces. When a beam of ultrasonic waves with multiple frequencies is continuously and perpendicularly incident on the component under test and propagates within it, the ultrasonic waves will undergo multiple reflections at the upper and lower interfaces within the component. When the thickness of the component under test is an integer multiple of half the wavelength, most of the incident and reflected waves will superimpose to form a standing wave, increasing the ultrasonic amplitude and significantly increasing the transmittance. The electromagnetic ultrasonic probe is more likely to receive the echo signal, resulting in a noticeable change at a specific frequency on the oscilloscope. The thickness of the component under test can then be calculated based on this frequency, expressed as:

[0063]

[0064]

[0065] In the formula, δ is the thickness of the component being tested; λ is the ultrasonic wavelength; c is the ultrasonic wave velocity in the material of the component being tested, which is only related to the elastic modulus E, Poisson's ratio σ, and material density p of the material of the component being tested; n is a multiple of half the wavelength; and f is the resonant frequency of the ultrasonic wave.

[0066] When n equals 1, the measured f1 is the fundamental frequency, meaning the resonance occurs at half the wavelength; this frequency is also called the first-order resonant frequency. Correspondingly, when n equals 2, 3, 4…, the resonance occurs at n times half the wavelength, at which point f2, f3, …, f… n Let be the second-order resonant frequency, the third-order resonant frequency, ..., the nth-order resonant frequency.

[0067] The difference between any two adjacent harmonic resonant frequencies is equal to the first-order resonant frequency, as shown below.

[0068] f n -f n-1 =f1 (3)

[0069] By analogy, if any two adjacent resonant frequencies are known, the thickness δ of the component being measured can be calculated, as shown below.

[0070]

[0071] Furthermore, when the Kth and Ith resonant frequencies are known (I>K≥1), that is, when the number of their adjacent frequencies is known, the thickness δ of the measured component can be calculated, as follows:

[0072]

[0073] The alloy component thickness calculated using the above method has a certain systematic uncertainty. To reduce this systematic uncertainty, this invention provides an improved method for online monitoring of corrosion thinning on a simulation test platform for aerospace hot-end metal components, such as... Figure 2 As shown, it includes the following steps:

[0074] S1: A laser is incident perpendicularly on the hot metal part under test to excite ultrasonic waves. In this embodiment, the laser-excited ultrasonic waves adopt an ablation mechanism.

[0075] S2: Receive ultrasonic echo signals through an electromagnetic ultrasonic probe placed on the surface of the metal component being tested at the hot end.

[0076] S3: Extract multiple resonant frequencies and their corresponding resonant orders based on ultrasonic echo signals.

[0077] Since interference signals of varying degrees are unavoidable at the front end, and these interference signals often occur below 1MHz, while resonant signals above 10MHz are difficult to distinguish from noise signals due to severe sound wave attenuation, it is preferable to eliminate frequency points below 1MHz and above 10MHz to improve detection accuracy. In this embodiment, multiple resonant points with significant amplitudes between 2MHz and 10MHz are preferred for data processing to obtain a more accurate thickness value.

[0078] In thinner alloy components, the ultrasonic signal travels a shorter path to the bottom, resulting in less signal attenuation. Therefore, as the thickness of the alloy component decreases, the amplitude of the resonant wave increases, leading to a more pronounced resonant signal. However, the reduced thickness also decreases the number of frequency points within the 2MHz to 10MHz range, affecting the accuracy of the final calculation results. For more reliable results from the laser-electromagnetic ultrasonic resonance method, a certain thickness range for the component is required (generally within 10mm).

[0079] Since the laser-excited ultrasonic wave in this embodiment uses an ablation mechanism, the excited longitudinal wave is more pronounced. Therefore, the resonant frequencies extracted in this embodiment are all longitudinal wave resonant frequencies. Figure 3As shown, this is the frequency domain diagram of the thickness measurement echo using the laser ultrasonic resonance method. Due to the presence of a vertical bias magnetic field, the resonant points of the transverse wave will exist simultaneously in the frequency domain diagram. The resonant points of the longitudinal wave and the transverse wave can be distinguished by the propagation relationship between the sound velocities of the transverse and longitudinal waves. The resonant points of the longitudinal wave are marked in the figure.

[0080] S4: Select adjacent and non-adjacent resonant frequencies to calculate multiple sets of first-order resonant frequencies with unequal precision. Perform a weighted average on these multiple sets of first-order resonant frequencies to obtain the weighted average value of the first-order resonant frequencies. and weighted uncertainty

[0081] Specifically, step S4 includes:

[0082] S41: Select multiple pairs of adjacent resonant frequencies to calculate the first group of first-order resonant frequencies.

[0083] S42: Select multiple pairs of non-adjacent resonant frequencies to calculate the second set of first-order resonant frequencies.

[0084] S43: Select multiple resonant frequencies and use the successive difference method to calculate the third set of first-order resonant frequencies.

[0085] S44: Perform a weighted average of the three sets of first-order resonant frequencies to obtain the weighted average of the first-order resonant frequencies. The calculation formula is as follows:

[0086]

[0087] In the formula, m and p i X i Let n and p represent the number of first-order resonant frequencies, their weights, and the i-th first-order resonant frequency in the first group of first-order resonant frequencies, respectively; j Y j Let l and p represent the number of first-order resonant frequencies, their weights, and the j-th first-order resonant frequency in the second group of first-order resonant frequencies, respectively; k Z k These represent the number of first-order resonant frequencies, their weights, and the kth first-order resonant frequency in the third group of first-order resonant frequencies, respectively.

[0088] The weight ratio of the three sets of first-order resonant frequencies is: p i :p j :p k = a:b:c. a, b, and c represent the number of resonant frequencies used when calculating the first-order resonant frequencies in the first group, the second group, and the third group, respectively.

[0089] Weighted uncertainty The standard deviation of the weighted average value f of the first resonant frequencies is expressed as follows:

[0090]

[0091]

[0092]

[0093]

[0094] In the formula, v i v j v k These represent the residual errors of the first-order resonant frequencies in the first group, the second group, and the third group, respectively.

[0095] For example, given six consecutive resonant points A, B, C, D, E, F, with resonant frequencies f0 and f1 respectively... A f B f C f D f E f F The first-order resonant frequency f can be determined from the difference between adjacent resonant frequencies. AB f BC f CD f DE f EF Let these numbers be X1, X2, X3, X4, and X5, where m is 5. The first-order resonant frequency f can be calculated from the difference between the resonant frequencies of adjacent numbers greater than 1. AC f AD f AE f AF f BD f BE f BF f CE f CF f DF Let them be Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8, Y9, Y 10 That is, n is set to 5; the first-order resonant frequency Z1 is calculated using the successive difference method based on the frequency differences between point A and points B, C, D, E, and F, where l is set to 1. Weighting is then applied according to the utilization of the number of resonant points, X... i and Y j Both utilize data from two resonant points, therefore the weight p i p j Both are 2, Z k Data from six resonant points were used, therefore the weight p k It is 6, that is: p i:p j :p k = 2:2:6. Of course, in other embodiments, the values ​​of m, n, l, and the three weights can be adjusted according to the actual situation.

[0096] S5: The thickness δ of the hot-end metal component being measured is calculated using the following formula:

[0097]

[0098]

[0099] In the formula, c is the ultrasonic wave velocity in the material of the hot-end metal component being measured, and f is the measured value of the first-order resonant frequency.

[0100] It should be noted that in the above embodiments, only the longitudinal wave resonant frequency in the echo is used for calculation. In other embodiments, the transverse wave resonant frequency and the corresponding resonant order can also be extracted at the same time. Then, the thickness δ′ of the tested hot end metal component based on the transverse wave is calculated using the same method as above. Then, the average value is taken with the thickness δ of the tested hot end metal component calculated based on the longitudinal wave as the final thickness of the tested hot end metal component.

[0101] The corrosion thinning online monitoring method for aerospace hot-end metal component simulation test platform provided in the above embodiments utilizes laser ultrasonic resonance thickness measurement to achieve online monitoring of corrosion thinning of high-temperature alloy materials in high-temperature environments. This method overcomes flutter conditions and meets the requirements for online corrosion thinning monitoring during turbine blade and engine exhaust nozzle testing. A method for addressing the unequal precision measurement uncertainty of laser ultrasonic resonance thickness measurement is proposed to minimize measurement errors by utilizing all available data.

[0102] This invention also provides an online monitoring system for corrosion thinning of a simulated test platform for aerospace hot-end metal components, used to implement the online monitoring method for corrosion thinning of a simulated test platform for aerospace hot-end metal components as described above. Figure 4 As shown, the system includes a laser excitation module and a host computer 5, a data acquisition card 4, a detection circuit 3, and an electromagnetic ultrasonic probe 2 connected in sequence; the host computer 5 is configured to execute steps S3 to S5.

[0103] Specifically, such as Figure 5 As shown, the detection circuit 3 includes a switching module, a low-voltage module, an impedance matching module, an echo detection module, and a sampling current module; the input terminals of the switching module, the low-voltage module, and the detection coil (EMAT coil) are electrically connected in sequence, the output terminal of the detection coil is electrically connected to the impedance matching module and the echo detection module respectively, and the sampling current module is electrically connected to the impedance matching module.

[0104] In this embodiment, the switching module consists of an FPGA development board, a driver chip, and a thyristor. The FPGA development board generates a square wave signal with a pulse width of 500μs every two seconds to control the conduction of the thyristor. The thyristor is an ITO-247, composed of two anti-parallel silicon controlled rectifiers (SCRs). It is a bidirectional SCR, capable of bidirectional conduction, and typically operates in the first or third quadrant. Its gate operating current is 30-60mA, the maximum gate trigger voltage is 1.5V, the maximum gate trigger current is 60mA, and the non-repetitive surge peak current is 1000A at 50Hz and 1047A at 60Hz. The low-voltage module's low-voltage capacitor bank provides a discharge current ic for a few milliseconds. This current ic is a smooth, near-DC current, providing a static bias magnetic field for ultrasonic wave reception, thus replacing the traditional permanent magnet. The low-voltage capacitor bank C1 has a capacitance of 1000μF, and the maximum charging voltage of the low-voltage power supply is 300V. The electromagnetic ultrasonic probe is a coil-only EMAT, with its detection coil providing the bias magnetic field and receiving ultrasonic waves. The impedance matching module consists of a series of high-frequency inductors with different inductance values ​​(0.7-25.6μH) and a series of high-voltage capacitors with different capacitance values ​​(0.33-10nF) connected in parallel. By adjusting the capacitor and inductor parameters, energy efficiency is improved, and the amplitude and signal-to-noise ratio of the echo signal are enhanced. Simultaneously, to consider the wideband reception characteristics of the circuit, external impedance matching can be used, which also serves as a frequency selector. Taking into account the effects of the number of coil turns, coil wire diameter, and coil outer diameter, the signal considering the coil parameters can be solved using COMSOL software in simulation. Then, PROTEUS is used to further process the acquired signal and adjust the wideband impedance matching parameters. In the sampling current module, a constantan wire sampling resistor is placed at the end of the circuit to acquire the low-voltage DC current passing through the detection coil. The echo detection module can pick up the echo signal, filter and amplify it, and then transmit it to the host computer after analog-to-digital conversion via the acquisition card.

[0105] like Figure 6As shown, in this embodiment, the coil-type EMAT includes a housing 22, a detection coil 21, an alumina sheet 23, and a signal interface 25. The alumina sheet 23 is disposed at the bottom of the housing 22, and the detection coil 21 is disposed at the top of the alumina sheet 23. The signal interface 25 is disposed on the housing 22 and is electrically connected to the detection coil 21 via a high-temperature resistant wire 24. The space between the housing 22 and the alumina sheet 23 is filled with high-temperature resistant ceramic adhesive 26. When the probe is working, a pulsed laser is excited by a pulsed laser. After the laser reaches the surface of the high-temperature alloy material, ultrasonic waves are generated in the high-temperature alloy material by an ablation mechanism. After a low-voltage DC-like current is applied to the coil, a bias magnetic field perpendicular to the coil direction can be provided, and the coil receives the ultrasonic echo signal. In addition, high-melting-point metallic silver is selected as the coil wire, and high-temperature resistant ceramic adhesive with a temperature of 1280℃ is used as the insulation material for the outside of the coil, which can improve the high-temperature resistance and protect both the detection coil and the high-temperature resistant wire. Continuous cooling with circulating water is not required, which meets the requirements for continuous detection in high-temperature environments. The corundum sheet, made of alumina, is positioned at the bottom of the detection coil. It possesses excellent insulation properties, does not participate in electromagnetic effects, and is also wear-resistant, water-resistant, corrosion-resistant, and high-temperature resistant. It has sufficient hardness to protect the detection coil. In some embodiments, the laser can be a through-type laser, i.e., as shown... Figure 6 As shown, a laser channel is provided in the middle of the coil-type EMAT; of course, in other embodiments, a side-through type can also be selected as needed, or the two can be separated independently.

[0106] Because lasers have the characteristic of propagating in a straight line in a uniform medium, complex environments such as narrow spaces are inevitably encountered in actual pipeline inspection. Pulsed lasers are usually quite large, and relying solely on moving the pulsed laser to achieve circumferential pipeline inspection would present many problems. To improve inspection efficiency, this embodiment combines laser fiber to achieve angular deflection during laser excitation, thereby enabling scanning functionality.

[0107] Specifically, the laser excitation module includes a pulsed laser 11, a laser fiber 12, and a focusing lens (not shown) connected in sequence. The laser 13 generated by the pulsed laser 11 is transmitted through the laser fiber 12 and then illuminates the surface of the hot-end metal component of the aerospace part under test after passing through the focusing lens. When the focusing lens is a convex lens, the light spot can be made into a disk shape, and the size of the light spot can also be changed. In this case, the detection coil is preferably a spiral coil, and the acquired signal is better. When the focusing lens is a prism, the light spot can be made into a sheet shape, and the size of the sheet-shaped light spot can also be adjusted. In this case, the detection coil is preferably a butterfly coil, and the acquired signal is better.

[0108] Because both laser excitation and EMAT reception use non-contact probes, non-contact testing of the workpiece can be achieved. Furthermore, the EMAT receiving probe is unaffected by surface roughness and vibration because it does not require coupling agent bonding. The optimized EMAT probe has low lift-off sensitivity, achieving resonant detection with a lift-off distance of at least 5mm, enabling online monitoring of corrosion thinning of high-temperature alloy materials under high-temperature flutter conditions. Conversely, traditional laser ultrasonic testing requires interferometer probes with high brightness requirements for the workpiece material, necessitating a highly reflective testing surface and strict perpendicularity between the probe and the workpiece testing surface. This places high demands on the testing environment. Under flutter conditions, the interferometer receives not only ultrasonic signals but also signals from workpiece vibration, significantly interfering with the required thickness measurement signal, making it difficult to apply in vibration-prone environments. Furthermore, the laser ultrasonic resonance method has a wide excitation bandwidth and can detect multiple resonant frequencies without the need for frequency sweeping signals, which can improve detection accuracy. The pulse reflection A-wave signal has limited energy and its detection resolution is affected by frequency. The resonance method can achieve the superposition of multiple reflection energies, which can greatly enhance the amplitude of the detection signal. The thickness can be detected based on the frequency domain signal after Fourier transform, which can reduce the influence of noise signals on the thickness measurement signal.

[0109] The above-described embodiment presents an online monitoring system for corrosion thinning of aerospace hot-end metal components, a simulation test platform capable of online monitoring of corrosion thinning in high-temperature alloy materials under high-temperature flutter conditions, meeting the requirements for broadband signal reception. Utilizing laser fiber technology, the system can change the laser output direction with low energy attenuation, overcoming the large size limitation of pulsed lasers and enabling real-time online monitoring of complex areas. By using convex lenses and cylindrical mirrors to modify the shape and size of the laser spot, the spot size is adjusted accordingly for thinner workpieces and vice versa. Smaller spots penetrate shallower due to significant laser beam scattering, while larger spots penetrate deeper. For workpieces of different shapes and thicknesses, different shaped light sources are combined with different shaped EMAT (Electromagnetic Acoustic Amplifier) ​​sensors to provide a bias magnetic field and receive ultrasonic echo signals.

[0110] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0111] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An on-line monitoring method of corrosion thinning of an aerospace hot end metal component simulation test platform, characterized in that, The method comprises the following steps: S1: using laser to vertically irradiate the measured hot-end metal component to excite ultrasonic waves; S2: receiving ultrasonic echo signals through an electromagnetic acoustic probe arranged on the surface of the measured hot-end metal component; S3: extracting a plurality of resonance frequencies and corresponding resonance orders based on the ultrasonic echo signals; S4: selecting adjacent resonant frequencies and non-adjacent resonant frequencies to calculate a plurality of groups of first-order resonant frequencies with different accuracies, performing weighted average processing on the plurality of groups of first-order resonant frequencies with different accuracies to obtain a weighted average value of the first-order resonant frequencies and a weighted uncertainty ; Step S4 specifically comprises: selecting a plurality of pairs of adjacent resonance frequencies to calculate a first group of first-order resonance frequencies; selecting a plurality of pairs of non-adjacent resonance frequencies to calculate a second group of first-order resonance frequencies; selecting a plurality of resonance frequencies to calculate a third group of first-order resonance frequencies by using a difference method; The first-order resonance frequency weighted average value is obtained by weighted average processing on the first-order resonance frequencies of the three groups The calculation formula is as follows: ； In the formula, m Represent the number of first-order resonant frequencies, their weights, and their order in the first group of first-order resonant frequencies, respectively. i One first-order resonant frequency; n , These represent the number of first-order resonant frequencies, their weights, and the first order resonant frequency in the second group, respectively. j One first-order resonant frequency; l , , Represent the number of first-order resonant frequencies, their weights, and their order in the third group of first-order resonant frequencies, respectively. k One first-order resonant frequency; Weighted uncertainty This is calculated by the formula: ； ； ； ； wherein , , respectively represent the residual error of the first order resonance frequency in the first set of first order resonance frequencies, the second set of first order resonance frequencies, the third set of first order resonance frequencies. S5: Calculate the thickness of the measured hot metal part according to the following formula : ； ； wherein c is the measured ultrasonic wave speed in the material of the hot section metal component, f is the first order resonance frequency measurement.

2. The method of claim 1, wherein the method is characterized by: The weight ratio of the three groups of first-order resonance frequencies is: ； wherein respectively represent the number of resonance frequencies used when calculating the first, second, and third set of first order resonance frequencies.

3. The method of claim 1, wherein the method is used for monitoring the corrosion thinning of an aerospace hot section metal component mockup test platform, wherein the method comprises: The resonance frequencies extracted in step S3 are located in the interval of 1 MHz to 10 MHz.

4. The method of claim 1, wherein, The resonance frequencies extracted in step S3 are all longitudinal wave resonance frequencies.

5. An on-line monitoring system for corrosion thinning of an aerospace hot section metal component simulation test platform, characterized in that, The system for implementing the corrosion thinning online monitoring method of the aerospace hot-end metal component simulation test platform as claimed in any one of claims 1 to 4 comprises a laser excitation module and, in sequence, a host computer, an acquisition card, a detection circuit, and an electromagnetic acoustic probe. The host computer is configured to perform steps S3-S5 in claim 1.

6. The system for on-line monitoring of corrosion thinning of aerospace hot section metal component mockup test platforms of claim 5, wherein, The electromagnetic acoustic probe comprises a shell, a detection coil, a corundum piece, and a signal interface. The corundum piece is arranged at the bottom of the shell, and the detection coil is arranged at the top of the corundum piece; the signal interface is arranged on the shell and is electrically connected with the detection coil.

7. The system for on-line monitoring of corrosion thinning of aerospace hot section metal component mockup test platforms of claim 6 wherein, The detection circuit comprises a switching module, a low-voltage module, an impedance matching module, an echo detection module, and a sampling current module; the switching module, the low-voltage module, and the input end of the detection coil are electrically connected in sequence; the output end of the detection coil is electrically connected with the impedance matching module and the echo detection module respectively; and the sampling current module is electrically connected with the impedance matching module.

8. The system for on-line monitoring of corrosion thinning of aerospace hot section metal component mockup test platforms of claim 6, wherein, The laser excitation module comprises, in sequence, a pulsed laser, a laser optical fiber, and a focusing lens.

9. The system for on-line monitoring of corrosion thinning of aerospace hot section metal component mockup test platforms of claim 8 wherein, When the focusing lens is a convex lens, the detection coil is a spiral coil; and when the focusing lens is a prism, the detection coil is a butterfly coil.

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