Acoustic emission sensing measurement method for blade shedding impact on composite materials

Abstract

The present invention relates to an acoustic emission sensing measurement method for a blade flying off and impacting a composite material, comprising the following steps: S1, when the explosive pre-buried in the root of the blade explodes, the composite material shaped part is impacted and the fiber breaks to emit an audio signal; S2, a three-way optical fiber F-P acoustic emission sensing probe uses a space division multiplexing method to send the detected audio signal to a photoelectric processing module through a coupler and a splitter in a large-range high-frequency acoustic signal demodulator, and then sends it to a data acquisition module after processing; S3, by measuring the acoustic frequency and intensity information at different times at the same position during the blade flying off and impacting the composite material, the time history of the audio signal is obtained; S4, by measuring the intensity information of the audio signal at different positions at the same time, the spatial history of the audio signal is obtained. The present invention can obtain the mechanical properties of the composite material to resist impact, with high spatial resolution, high response rate and high sensitivity, and can improve the accuracy of measurement.

Description

Technical Field

[0001] The invention relates to the field of optical fiber FP sensing technology, and more specifically to an acoustic emission sensing measurement method for a blade flying off and impacting a composite material process. Background Art

[0002] The high-speed penetration and penetration of carbon fiber composite laminates is a very complex and difficult process. Its research involves multiple disciplines such as materials science and mechanics. At the same time, there are many factors affecting the failure model and destruction process of composite laminates under high-speed impact. The blade flying off causes damage to the outer layer of the composite material. The flying fragments may penetrate the external important structural parts, and thus cause a series of problems, causing significant economic losses and serious social impact. The transmission medium of fiber optic sensing technology is optical fiber, and the carrier is an optical signal. It overcomes many disadvantages of traditional electrical sensors and brings many new advantages. Compared with traditional monitoring systems, the acoustic emission sensor based on optical fiber FP has strong anti-electromagnetic interference ability and can be used in places with strong electromagnetic field interference; the material of the sensor is mainly quartz, which has strong corrosion resistance and can be used in places with rain and corrosive gas; it provides support for the new application of FP acoustic emission sensors in optical fiber sensors and the development of damage monitoring of composite materials.

[0003] At present, there are several methods for measuring the acoustic signal of impact composite materials: 1. The acoustic signal detection method introduced in the Chinese patent (patent number CN201711267234.2) "A composite acoustic detection sensor and detection method", whose sensor structure includes an excitation piezoelectric chip, a vibration rod, a capacitive microphone, a contact, etc., to achieve the measurement of the composite fiber tearing acoustic signal. However, the electrical sensor used in the invention is susceptible to electromagnetic signal interference, has poor waterproof and corrosion resistance, and cannot achieve long-term stable detection. 2. Fu Tao (Fu Tao, Research on new optical fiber sensors and their acoustic emission source determination in fiber composite materials, Harbin Institute of Technology) proposed a new optical fiber acoustic emission sensor based on a fused cone type optical fiber coupler. The sensor consists of two single-mode optical fibers that are parallel and twisted together after removing the coating at a specified position, and then heated in a hydrogen flame. At the same time, the optical fiber is stretched to make the heated and molten optical fiber in the middle thinner, forming a structure with two tapered parts and a thin waist, and finally encapsulated with a small capillary glass tube. However, by comparing the amplitude-frequency response characteristics of the sensor with those of the stress wave, the sensor is only suitable for low-frequency acoustic emission source monitoring.

[0004] At present, the detection method of acoustic signals of impact damage to composite materials is mainly implemented by electrical sensors. Since electrical sensors are susceptible to electromagnetic interference, have poor waterproof and corrosion resistance, and have difficulty working in harsh environments, signal processing is limited and signal acquisition is inaccurate. Other methods using optical fiber sensors can only detect low-frequency acoustic signals, and cannot detect ultrasonic signals emitted by composite fiber tearing, which makes signal detection have certain limitations. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an acoustic emission sensing measurement method for the process of blade flying off and impacting a composite material. The present invention has the characteristics of anti-electromagnetic interference, wide and adjustable response bandwidth, and can detect the time distribution of the generation, development and attenuation of the acoustic signal and the spatial distribution of the intensity during the impact damage of the composite material, and can realize high-precision, high-response rate, and high-sensitivity multi-point three-dimensional accurate measurement of the acoustic signal of the impact damage of the composite material.

[0006] The technical solution adopted by the present invention to solve the technical problem is: construct an acoustic emission sensing measurement method for the blade flying off and impacting a composite material, the measurement method adopts the following instruments: including three optical fiber FP acoustic emission sensor probes, a large-range high-frequency acoustic signal demodulator, an optical cable, a host computer and a flying off test bench, the three optical fiber FP acoustic emission sensor probes are respectively arranged in the X, Y and Z directions of the flying off test bench;

[0007] The tunable semiconductor laser light source in the large-range high-frequency acoustic signal demodulator is used as the light source in the measurement process. The light emitted by the tunable semiconductor laser light source passes through an optical isolator and then is divided into three optical signals by a splitter. The three optical fiber FP acoustic emission sensor probes are respectively connected to the three optical fiber FP acoustic emission sensor probes through optical couplers and optical cables. The three optical fiber FP acoustic emission sensor probes are connected to the optical path in a space division multiplexing manner.

[0008] The measuring method comprises the following steps:

[0009] S1. When the explosive pre-buried in the root of the blade explodes, the composite material shaped part is impacted and the fiber breaks, emitting an audio signal;

[0010] S2, the three-way optical fiber FP acoustic emission sensor probe uses space division multiplexing to send the detected audio signal to the optoelectronic processing module through the coupler and splitter in the large-range high-frequency acoustic signal demodulator, and then sends it to the data acquisition module after processing;

[0011] S3, the collected acoustic emission signal is Fourier transformed by the host computer to obtain all the frequency components of the acoustic emission signal and the intensity information of the frequency, and then the monitored signal EMD is decomposed to obtain the IMF component and the residual component, and then each IMF component is Hilbert transformed to obtain the time-frequency diagram of the signal, and the frequency distribution and intensity of the signal in the entire monitoring time can be intuitively seen through the time-frequency diagram;

[0012] S4. By measuring the intensity information of the audio signal at different positions at the same time, the spatial history of the audio signal is obtained.

[0013] According to the above scheme, in order to ensure that the three optical fiber FP acoustic emission sensor probes can perform stable and high-performance measurements under a large frequency span, before the measurement begins, the static operating point of the system is adjusted by an automatic Q-switching method to maintain the Q point in the linear working area continuously under a large range of audio signal changes.

[0014] According to the above scheme, in step S2, in order to realize a wide range audio signal, the received audio signal is processed by using a wide range high frequency signal processing method.

[0015] According to the above scheme, in step S3, the signal from the blade flying off impact to the whole composite material special-shaped part destruction process adopts the signal processing method of Fourier transform and Hilbert-Huang transform.

[0016] The acoustic emission sensing measurement method for blade shedding impacting composite materials according to the present invention has the following beneficial effects:

[0017] 1. The present invention adopts an optical fiber sensor and an optical fiber FP acoustic emission probe type sensor, which has a wider response frequency and higher sensitivity; adopts the X, Y, and Z axis probe layout method, which can realize multi-point stereoscopic and distributed online measurement;

[0018] 2. The present invention adopts automatic Q-switching technology to ensure that the sensor can perform stable and high-performance measurements under a large frequency span; by using signal processing methods such as Fourier transform and Hilbert-Huang transform, the time-frequency characteristics of the acoustic emission signal in the X, Y, and Z axis directions of the impact damage of the composite material can be obtained, thereby realizing the numerical damage analysis of the component. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0020] Figure 1 It is a schematic diagram of an acoustic emission sensor measuring device for blade shedding impact composite materials of the present invention; DETAILED DESCRIPTION

[0021] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0022] like Figure 1 As shown, the acoustic emission sensing measurement method of the blade flying off and impacting the composite material process of the present invention adopts the following instruments: including three optical fiber FP acoustic emission sensor probes 1, a large-range high-frequency acoustic signal demodulator 2, an optical cable 3, a host computer 4 and a flying off test bench 5, and the three optical fiber FP acoustic emission sensor probes 1 are respectively arranged in the X, Y and Z directions of the flying off test bench 5.

[0023] The tunable semiconductor laser light source in the large-range high-frequency acoustic signal demodulator 2 is used as the light source in the measurement process. The light emitted by the tunable semiconductor laser light source passes through an optical isolator and then is divided into three optical signals by a splitter. The three optical fiber FP acoustic emission sensor probes 1 are respectively connected to the optical path by optical couplers via optical cables 3. The three optical fiber FP acoustic emission sensor probes 1 are connected to the optical path by space division multiplexing.

[0024] The measurement method includes the following steps:

[0025] In order to ensure that the three optical fiber FP acoustic emission sensor probes 1 can perform stable and high-performance measurements over a large frequency span, before the measurement begins, the system static operating point is adjusted by an automatic Q-switching method to maintain the Q point in the linear operating area when the audio signal changes over a large range.

[0026] S1. When the explosive pre-buried in the root of the blade explodes, the composite material shaped part is impacted and the fibers break, emitting an audio signal.

[0027] S2, the three-way optical fiber FP acoustic emission sensor probe 1 uses space division multiplexing to send the detected audio signal to the optoelectronic processing module through the coupler and splitter in the large-range high-frequency acoustic signal demodulator 2, and then sends it to the data acquisition module after processing; in order to realize the large-range audio signal, the audio signal received by the measurement is processed by a large-range high-frequency signal processing method.

[0028] S3. By performing Fourier transform on the collected acoustic emission signal through the host computer, all frequency components of the signal and the intensity information of the frequency can be obtained. Then, the EMD of the monitored signal is decomposed to obtain the IMF component and the residual component. Then, the Hilbert transform of each IMF component can be used to obtain the time-frequency diagram of the signal. The frequency distribution and intensity of the signal during the entire monitoring time can be intuitively seen through the time-frequency diagram.

[0029] S4. By measuring the intensity information of the audio signal at different positions at the same time, the spatial history of the audio signal is obtained.

[0030] In a preferred embodiment of the present invention, it includes three optical fiber FP acoustic emission sensor probes 1 arranged in the X, Y, and Z directions near a fly-off test bench 5, a large-range high-frequency acoustic signal demodulator 2, an optical cable 3, a host computer 4, and a fly-off test system. The measuring method is as follows: a tunable semiconductor laser light source in a large-scale high-frequency acoustic signal demodulator 2 is used as a light source in the measuring process; the light emitted by the tunable semiconductor laser light source passes through an optical isolator, and then is divided into three optical signals through a splitter, and is connected to an optical fiber FP acoustic emission sensor probe 1 through an optical coupler via an optical cable 3; the three-way optical fiber FP acoustic emission sensor probe 1 is connected to the optical path in a space division multiplexing manner; when the explosive pre-buried in the root of the blade explodes, the composite material shaped part is impacted and the fiber breaks to emit an audio signal; the three-way optical fiber FP acoustic emission sensor probe 1 uses a space division multiplexing method to send the detected audio signal to a photoelectric processing module through a coupler and a splitter in the large-scale high-frequency acoustic signal demodulator 2, and then is sent to a data acquisition module after processing; finally, the collected signal is analyzed and processed by a host computer 4 to measure the acoustic frequency and intensity information at the same position and at different times during the blade flying off and impacting the composite material, and the time history of the audio signal is obtained; by measuring the intensity information of the audio signal at different positions at the same time, the spatial history of the audio signal is obtained.

[0031] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. An acoustic emission sensing measurement method for a blade flying off and impacting a composite material, characterized in that: The measuring method adopts instruments including: three optical fiber FP acoustic emission sensor probes, a large-range high-frequency acoustic signal demodulator, an optical cable, a host computer and a fly-off test bench, wherein the three optical fiber FP acoustic emission sensor probes are respectively arranged in the X, Y and Z directions of the fly-off test bench; The tunable semiconductor laser light source in the large-range high-frequency acoustic signal demodulator is used as the light source in the measurement process. The light emitted by the tunable semiconductor laser light source passes through an optical isolator and then is divided into three optical signals by a splitter. The three optical fiber FP acoustic emission sensor probes are respectively connected to the three optical fiber FP acoustic emission sensor probes through optical couplers and optical cables. The three optical fiber FP acoustic emission sensor probes are connected to the optical path in a space division multiplexing manner. The measuring method comprises the following steps: S1. When the explosive pre-buried in the root of the blade explodes, the composite material shaped part is impacted and the fiber breaks, emitting an audio signal; S2, the three-way optical fiber FP acoustic emission sensor probe uses space division multiplexing to send the detected audio signal to the optoelectronic processing module through the coupler and splitter in the large-range high-frequency acoustic signal demodulator, and then sends it to the data acquisition module after processing; S3, the collected acoustic emission signal is Fourier transformed by the host computer to obtain all the frequency components of the acoustic emission signal and the intensity information of the frequency, and then the monitored signal EMD is decomposed to obtain the IMF component and the residual component, and then each IMF component is Hilbert transformed to obtain the time-frequency diagram of the signal, and the frequency distribution and intensity of the signal in the entire monitoring time can be intuitively seen through the time-frequency diagram; S4. By measuring the intensity information of the audio signal at different positions at the same time, the spatial history of the audio signal is obtained.

2. The acoustic emission sensing measurement method for the blade flying off and impacting composite materials according to claim 1 is characterized in that: In order to ensure that the three optical fiber FP acoustic emission sensor probes can perform stable and high-performance measurements over a large frequency span, the system static operating point is adjusted by an automatic Q-switching method before the measurement begins, maintaining the Q point in the linear operating area when the audio signal changes over a large range.

3. The acoustic emission sensing measurement method for the blade flying off and impacting composite materials according to claim 1 is characterized in that: In step S2, in order to realize a wide range audio signal, the received audio signal is processed by using a wide range high frequency signal processing method.

4. The acoustic emission sensing measurement method for the blade flying off and impacting composite materials according to claim 1 is characterized in that: In step S3, the signal processing method of Fourier transform and Hilbert-Huang transform is used for the signal from the blade flying off impact to the whole composite material special-shaped part destruction process.

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