A simulation method and platform fixture of hub central piece crack acoustic emission signal

Abstract

The application relates to a simulation method and platform dummy of a hub central piece crack acoustic emission signal, and the simulation method comprises the following steps: (1) preparing a standard fatigue test piece; (2) acquiring acoustic emission signals of a whole process of fatigue fracture of the standard fatigue test piece; (3) performing filtering and noise reduction pretreatment on the acquired acoustic emission signals; (4) generating simulation acoustic emission signals; (5) installing a hub central piece platform dummy on a model rotor test bed; (6) operating the model rotor test bed to complete rotor system hub central piece crack damage monitoring test verification; the waveform and spectrum characteristics of the crack acoustic emission signals are determined through fatigue fracture test of the hub central piece test piece made of the same material; the crack acoustic emission signals are simulated by using an acoustic emission signal waveform generator and a driver; finally, the simulation of the hub central piece crack acoustic emission signals is completed on the model rotor test bed, and the rotor system hub central piece crack damage monitoring test verification is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of helicopter health and usage monitoring, in particular to a hub central piece crack acoustic emission signal simulation method and platform dummy piece. BACKGROUND

[0002] Considering that the rotor system is very dangerous when the hub central piece produces real fatigue crack damage under high-speed operation, and the huge centrifugal force makes it risky to install a fixed sensor on it. Therefore, the acoustic emission detection technology is applied to the helicopter rotor system to realize the detection and identification of hub central piece fatigue crack damage. The following key technical problems need to be solved: crack acoustic emission signal separation technology under strong background noise interference of the rotor system, crack acoustic emission signal conduction mechanism analysis technology under complex configuration, hub central piece crack acoustic emission signal physical simulation technology, acoustic emission sensor optimization layout and installation technology in the narrow space of the rotor system. The hub central piece, as the core component of the helicopter rotor system, is usually made of titanium alloy material with the advantages of high strength, good fracture toughness, good low temperature performance and strong corrosion resistance. However, due to the complex loading condition of the hub central piece, it bears high and low cycle alternating loads from the rotor, transmission and aircraft, and its failure mode under complex loading condition is mainly fatigue crack damage. Moreover, it is a single-channel complex structure without redundancy, and once it fails, it will cause disastrous consequences. Therefore, it is necessary to carry out fatigue crack damage monitoring of the hub central piece of the helicopter rotor system.

[0003] At present, for the fatigue crack damage monitoring of the helicopter hub central piece, the early domestic and foreign mainly use the structure vibration response analysis method based on strain gauge. With the development of sensor technology, acoustic emission, piezoelectric guided wave, optical fiber sensing and other technologies are also gradually applied to the fatigue crack damage detection of metal materials. The structure vibration response analysis method can monitor the more serious failure state of the hub central piece, but due to the influence of strong background noise interference in the complex operating environment of the helicopter, the early fault symptom discovery ability is insufficient. Compared with the conventional strain monitoring method, the acoustic emission detection technology realizes real-time monitoring of damage by continuously monitoring the transient elastic waves suddenly released due to deformation or damage inside or on the surface of the material. The acoustic emission signal characteristics generated by different materials, different objects and different damages are not the same. Therefore, as a dynamic non-destructive testing technology, acoustic emission detection technology is more suitable for crack initiation and propagation monitoring of the helicopter hub central piece.

[0004] It is very dangerous to make the hub central part produce real fatigue crack damage in the case of high-speed operation of the rotor system, and the huge centrifugal force also makes it risky to install fixed sensors on it. Therefore, the application of acoustic emission detection technology to the helicopter rotor system to realize the detection and identification of the fatigue crack damage of the hub central part still needs to solve the following key technical problems: crack acoustic emission signal separation technology under the strong background noise interference of the rotor system, crack acoustic emission signal conduction mechanism analysis technology under complex configuration, crack acoustic emission signal physical simulation technology of the hub central part, and acoustic emission sensor optimization layout and installation fixing technology in the narrow space of the rotor system. SUMMARY

[0005] The purpose of the present application is to provide a simulation method and platform for crack acoustic emission signals of the hub central part, to determine the waveform and frequency spectrum characteristics of the crack acoustic emission signals through fatigue fracture test of the hub central part test piece made of the same material, to simulate the crack acoustic emission signals by using acoustic emission signal waveform generator and driver, to reasonably design the installation platform and fixing method according to the size of the acoustic emission sensor, amplifier, transducer and wire harness arrangement, and finally to complete the simulation of the crack acoustic emission signals of the hub central part on the model rotor test bench, so as to realize the crack damage monitoring test verification of the rotor system hub central part.

[0006] The technical scheme of the present application is as follows:

[0007] A simulation method for crack acoustic emission signals of the hub central part, comprising the following steps:

[0008] (1) making a standard fatigue test piece;

[0009] (2) obtaining acoustic emission signals of the whole process of fatigue fracture of the standard fatigue test piece;

[0010] (3) filtering and denoising the obtained acoustic emission signals for pretreatment;

[0011] (4) generating simulation acoustic emission signals;

[0012] (5) installing the hub central part platform dummy on the model rotor test bench;

[0013] (6) running the model rotor test bench to complete the crack damage monitoring test verification of the rotor system hub central part.

[0014] Further, in step (1), a rectangular cross-section standard fatigue test piece with double pre-made notches is designed by using the same material as the hub central part.

[0015] Further, step (2) is specifically: paste the acoustic emission sensor on the upper and lower sides of the pre-prepared notch of the standard fatigue test piece, fix the standard fatigue test piece with the acoustic emission sensor on the fatigue test system clamp, perform the sine load cyclic stress loading, and obtain the acoustic emission signal in the whole process of fatigue fracture of the test piece.

[0016] Further, the maximum load of the cyclic stress loading is 20KN, the minimum load is 2KN, the stress ratio R is 0.1, and the loading frequency is 5Hz.

[0017] Further, the acoustic emission signal in the whole process of fatigue fracture of the test piece includes the acoustic emission signals in the crack initiation state stage, the crack initiation state stage, and the crack expansion and fracture state stage.

[0018] Further, step (3) is specifically: using db18 wavelet basis to decompose the acoustic emission signal for several layers, using the hard threshold method for noise reduction processing, finally reconstructing the acoustic emission signal, and extracting the typical characteristic parameters of each stage of the reconstructed acoustic emission signal, including: amplitude, frequency, repetition rate, threshold, pulse width, ring count, rise time, and duration.

[0019] Further, the pre-processed acoustic emission signals and typical characteristic parameters of each stage are input into the acoustic emission signal waveform generator and driver for generating simulated acoustic emission signals.

[0020] Further, step (6) is specifically: after the model rotor test bench runs to the rated speed, the generated crack acoustic emission simulation signal is intermittently sent to the transducer of the platform dummy part by the acoustic emission signal waveform generator and driver, the two acoustic emission sensors of the platform dummy part perform real-time data acquisition, the collected acoustic emission signals are conditioned by the two preamplifiers of the platform dummy part, and then transmitted to the acoustic emission acquisition system through the current collector ring for analysis, and the crack damage monitoring test verification of the rotor system hub central part is completed.

[0021] A platform dummy part applied to a simulation method of a hub central part crack acoustic emission signal, comprising a mounting platform, wherein an arc-shaped notch for avoiding a damper is arranged at the edge of the mounting platform, the arc-shaped notch equally divides the mounting platform into four mounting surfaces which are symmetrical in pairs, two symmetrical mounting surfaces are respectively provided with acoustic emission sensors, and the other two symmetrical mounting surfaces are respectively provided with preamplifiers, the preamplifiers are respectively connected with the acoustic emission sensors in one-to-one correspondence, a transducer is mounted in the center of the mounting platform, the transducer is connected with the acoustic emission signal waveform generator and driver, bolt holes are arranged at the edges of the mounting surfaces, and the platform dummy part is connected with the hub central part through the bolt holes.

[0022] The beneficial effects of the present application: the present application provides a simulation method and platform dummy of hub central crack acoustic emission signal, which uses acoustic emission signal waveform generation and driver and transducer to output crack acoustic emission simulation signal, without the need for destructive measures such as pre-made defects for hub central structure, ensuring the safety of test personnel and test equipment; the acoustic emission signal of the fatigue fracture test of the rectangular test piece made of the same material is used for signal simulation and tested on the model rotor test bench, ensuring the authenticity and reliability of the rotor system hub central crack damage monitoring test verification; the platform dummy designed and processed has exquisite configuration, and the installation and fixation implementation process is simple and convenient; the method and platform dummy of the present application have been applied to the simulation of the model rotor test bench hub central crack acoustic emission signal, and good results have been achieved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the cyclic stress loading test fatigue test system.

[0024] Figure 2 It is a schematic diagram of the structure of the standard fatigue test piece.

[0025] Figure 3 It is a schematic diagram of the model rotor system hub central crack damage monitoring test.

[0026] Figure 4 It is an elevation view of the platform dummy.

[0027] Figure 5 It is an isometric view of the platform dummy.

[0028] 1, fatigue test system, 2, upper clamp, 3, standard fatigue test piece, 4, lower clamp, 5, acoustic emission sensor, 6, acoustic emission acquisition system, 7, model rotor system test bench, 8, rotor system, 9, platform dummy, 10, wire, 11, preamplifier, 12, transducer. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] A simulation method of hub central crack acoustic emission signal steps as follows:

[0031] (1) The weak area of the rotor hub central part under load concentration is a rectangular area, therefore, according to GB / T 228.1-2010 “Metallic Materials Tensile Testing-Part 1: Method of Tensile Test at Room Temperature” and GB / T 6398-2017 “Metallic Materials Fatigue Testing-Fatigue Crack Propagation Methods”, a rectangular cross-section standard fatigue test piece 3 with double-sided pre-notched is designed with the same material as the hub central part, the test piece is 240mmx40mmx3mm in size, the surface roughness is 1μm, a tapered notch defect with a width of 3mm and a depth of 1.5mm is preformed in the middle of the test piece, as shown in FIG. 2, the standard fatigue test piece 3 can effectively simulate the most weak rectangular area of the hub central part under load, and the defect design form shortens the tensile fracture process and ensures that multiple standard fatigue test pieces are tensile fractured at the same position. Figure 2

[0032] (2) Two acoustic emission sensors 5 are pasted on the upper and lower sides of the pre-notched of the standard fatigue test piece 3 to facilitate the collection of acoustic emission signals propagating in different directions at the tensile fracture position, the fatigue test piece 3 with the acoustic emission sensors 5 pasted thereon is fixed on the upper clamp 2 and the lower clamp 4 of the fatigue test system 1, a sinusoidal load cycle stress is loaded to accelerate the tensile fracture process, the maximum load is 20KN, the minimum load is 2KN, the stress ratio R is 0.1, the loading frequency is 5Hz, and the acoustic emission signals in the whole fatigue fracture process of the test piece are acquired by the acoustic emission acquisition system 6, including the crack-free state stage, the crack initiation state stage, and the crack propagation and fracture state stage, as shown in FIG. 3. Figure 1

[0033] (3) The acquired acoustic emission signals are pre-processed by filtering and noise reduction, the db18 wavelet basis is selected for 5-layer decomposition of the acoustic emission signals, the hard threshold method is used for noise reduction processing, and finally the acoustic emission signals are reconstructed to achieve the maximum suppression of noise while minimizing the impact on the signals, and the typical characteristic parameters of each stage of the reconstructed acoustic emission signals are extracted, including amplitude, frequency, repetition rate, threshold, pulse width, ring count, rise time, and duration.

[0034] (4) The pre-processed acoustic emission signals and typical characteristic parameters of each stage are input into the acoustic emission signal waveform generator and driver for generating simulated acoustic emission signals, the device includes a microprocessor module, a DDS module based on FPGA, a high-speed D / A module, an amplitude adjustment module, a filtering and amplification module, a power driving module, a WiFi interface module, a touch display module, and a power module, and has the advantages of high signal simulation accuracy and multiple adjustable waveforms; the acoustic emission signal waveform generator and driver adopts the acoustic emission signal waveform generator disclosed in Chinese patent CN211579943U.

[0035] ​​(5) First, the platform dummy 9 is fixed on the hub central member of the model rotor system 8 by threaded connection; then two acoustic emission sensors 5 for receiving crack acoustic emission signals, two preamplifiers 11 for amplifying and conditioning the crack acoustic emission signals received by the acoustic emission sensors 5, and one transducer 12 for emitting crack acoustic emission simulation signals are respectively placed in the reserved space of the platform dummy 9; then the cover plate is installed by threaded connection, which can effectively prevent the cover plate from being thrown out; finally, the wires 10 of each device are led out from the reserved holes and routed along the edge of the platform dummy, and after being bundled and fixed with a strap, they are connected to the acoustic emission acquisition system 6 and the acoustic emission signal waveform generator and driver, which improves the test accuracy and reduces the test interference, realizes high-reliability acoustic emission signal excitation, acquisition and long-distance transmission, as shown in Figure 3 .

[0036] (6) After the model rotor test bed 7 runs to the rated speed, the acoustic emission signal waveform generator and driver intermittently sends the generated crack acoustic emission simulation signals to the transducer 12 for output, and the two acoustic emission sensors perform real-time data acquisition. The collected acoustic emission signals are conditioned by the two preamplifiers 11 and then transmitted to the acoustic emission acquisition system for analysis through the bus bar, completing the rotor system hub central member crack damage monitoring test verification, which can truly and effectively simulate the operating environment noise of the helicopter rotor system.

[0037] Another embodiment of the present application is to provide a platform dummy 9 applied to a crack acoustic emission simulation method of a hub central member, which comprises a mounting platform, the edge of the mounting platform is provided with an arc-shaped notch for avoiding the damper, and the arc-shaped notch equally divides the mounting platform into four mounting surfaces which are symmetrically arranged in pairs. Two symmetrically arranged mounting surfaces are respectively provided with an acoustic emission sensor 5, and the other two symmetrically arranged mounting surfaces are respectively provided with a preamplifier 11. The preamplifier 11 is connected to the acoustic emission sensor 5 in one-to-one correspondence. A transducer 12 is mounted in the center of the mounting platform, and the transducer 12 is connected to the acoustic emission signal waveform generator and driver. The edge of the mounting surface is provided with a bolt hole, and the platform dummy is connected to the hub central member by the bolt passing through the bolt hole, as shown in Figure 4 .

[0038] The above is only a specific embodiment of the present application, which is described in detail, and the part not described in detail is a conventional technology. However, the protection scope of the present application is not limited to this, and any changes or replacements within the technical range disclosed by the present application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present application. The protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of simulating a hub central piece crack acoustic emission signal, characterized by, It comprises the following steps: (1) making a standard fatigue test piece; (2) obtaining acoustic emission signals of the whole process of fatigue fracture of the standard fatigue test piece; (3) filtering and denoising preprocessing of the obtained acoustic emission signals; (4) generating simulated acoustic emission signals; (5) installing the hub central piece platform dummy on the model rotor test bench; (6) the model rotor test bench is running, and the rotor system hub central piece crack damage monitoring test verification is completed, specifically: after the model rotor test bench is running to the rated speed, the generated simulated acoustic emission signals are sent to the transducer of the platform dummy for output by the acoustic emission signal waveform generation and driver intermittently, the two acoustic emission sensors of the platform dummy perform real-time data acquisition, and the collected acoustic emission signals are conditioned by the two preamplifiers of the platform dummy and then transmitted to the acoustic emission acquisition system through the current collector ring for analysis, thereby completing the rotor system hub central piece crack damage monitoring test verification.

2. The method of claim 1, wherein, In step (1), a rectangular cross-section standard fatigue test piece with double-sided pre-prepared notches made of the same material as the hub central piece is used.

3. The method of claim 1, wherein, Step (2) is specifically: the acoustic emission sensor is pasted on the upper and lower sides of the pre-prepared notch of the standard fatigue test piece, the standard fatigue test piece with the pasted acoustic emission sensor is fixed on the fatigue test system clamp, the sinusoidal load cyclic stress is loaded, and the acoustic emission signals in the whole process of fatigue fracture of the test piece are obtained.

4. The method of claim 3, wherein, The maximum load of the cyclic stress loading is 20KN, the minimum load is 2KN, the stress ratio R is 0.1, and the loading frequency is 5Hz.

5. The method of claim 3, wherein, The acoustic emission signals in the whole process of fatigue fracture of the test piece include the acoustic emission signals in the stages of no crack, crack initiation and crack propagation to fracture.

6. The method of claim 3, wherein, Step (3) is specifically: the acoustic emission signals are decomposed by several layers using db18 wavelet basis, denoising processing is performed using the hard threshold method, the acoustic emission signals are finally reconstructed, and the typical characteristic parameters of each stage of the reconstructed acoustic emission signals are extracted, including amplitude, frequency, repetition rate, threshold, pulse width, ring count, rise time and duration.

7. The method of claim 6, wherein, The preprocessed acoustic emission signals and typical characteristic parameters of each stage are input into the acoustic emission signal waveform generation and driver for generating simulated acoustic emission signals.

8. A platform dummy part for applying the simulation method of the hub central part crack acoustic emission signal according to any one of claims 1-7, characterized in that: The installation platform is provided with an arc-shaped notch for avoiding the damper at the edge of the installation platform, the arc-shaped notch equally divides the installation platform into four installation surfaces which are symmetrical in pairs, two symmetrical installation surfaces are respectively provided with acoustic emission sensors, and the other two symmetrical installation surfaces are respectively provided with preamplifiers which are respectively connected with the acoustic emission sensors in one-to-one correspondence, a transducer is installed in the center of the installation platform, the transducer is connected with the acoustic emission signal waveform generation and driver, bolt holes are arranged at the edges of the installation surfaces, and the platform dummy is connected with the hub central piece through the bolt holes.

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