Solid propellant grain elastic modulus detection method, crack detection method and system

Abstract

The invention relates to a solid propellant grain elastic modulus detection method, a crack detection method and a crack detection system. During elastic modulus detection, a calibrated Poisson's ratio is determined through solid propellant fuel, and then the ultrasonic longitudinal wave velocity in a solid propellant grain is determined based on echoes; and calculating the elastic modulus of the solid propellant grain based on the calibrated Poisson's ratio and the ultrasonic longitudinal wave velocity in the solid propellant grain, thereby realizing the detection of the elastic modulus of the grain. When cracks are detected, echo signals are subjected to noise reduction, a wave packet and the arrival time of the wave packet are determined through enveloping, then the distance from ultrasonic waves to the wave packet is calculated based on the ultrasonic longitudinal wave velocity and the wave packet, and then whether cracks exist or not is determined by comparing the distance from the ultrasonic waves to the wave packet with the thickness of a solid propellant grain. According to the invention, the real-time elastic modulus of the solid propellant grain can be detected, and crack detection can be carried out on the whole solid propellant grain including the internal structure of the solid propellant grain without destroying the integrity of the solid propellant grain.

Description

Technical Field

[0001] The invention relates to the technical field of solid propellant grain detection, and in particular to a solid propellant grain elastic modulus detection method, a crack detection method and a system. Background Art

[0002] Solid propellant is an energetic composite material with specific properties. Currently, the commonly used solid propellant is a mixture of polymers, oxidizers, metal fuels, etc. The macroscopic performance of solid propellant grain is viscoelastic, and it is very difficult to detect its elastic modulus and Poisson's ratio.

[0003] In addition, solid propellant grains are obtained by molding solid propellant raw materials using a molding device. The destruction of their structural integrity is one of the core reasons for engine failure. Cracks are a common factor that destroys the structural integrity of solid propellant grains. Cracks may occur during the process of solid propellant grains being loaded into the engine. Therefore, it is very important to detect cracks in solid propellant grains loaded into the engine.

[0004] The traditional method for detecting cracks in solid propellant grains is often to sample the solid propellant grains loaded into the engine and then conduct experimental tests in the laboratory. This process destroys the integrity of the solid propellant grains and is not only time-consuming and labor-intensive, but also difficult to fully evaluate the internal structure of the entire solid propellant grain. Summary of the invention

[0005] Based on this, it is necessary to provide a solid propellant grain elastic modulus detection method, crack detection method and system to address the above technical problems, which can detect and calculate the real-time elastic modulus of the solid propellant grain, and can perform crack detection on the entire solid propellant grain including its internal structure without destroying the integrity of the solid propellant grain.

[0006] In a first aspect, the present invention provides a method for detecting the elastic modulus of a solid propellant grain, comprising the following steps:

[0007] Conduct mechanical tests on solid propellant raw materials to obtain the elastic modulus and ultrasonic longitudinal wave velocity of the solid propellant raw materials;

[0008] The calibrated Poisson's ratio is calculated based on the elastic modulus of the solid propellant raw material and the ultrasonic longitudinal wave velocity according to the elastic modulus calculation formula;

[0009] Sending longitudinal wave signals to the solid propellant grains in the engine outside the engine and receiving echo signals, and then determining the ultrasonic longitudinal wave velocity in the solid propellant grains according to the echo signals;

[0010] The elastic modulus of the solid propellant grain is calculated based on the calibrated Poisson's ratio and the ultrasonic longitudinal wave velocity in the solid propellant grain according to the elastic modulus calculation formula.

[0011] In one embodiment, the solid propellant raw material is subjected to mechanical testing to obtain the elastic modulus of the solid propellant raw material, including:

[0012] Conducting tensile tests on solid propellant raw materials to obtain tensile load-displacement curves of the solid propellant raw materials;

[0013] The elastic modulus of solid propellant raw materials was calculated based on the tensile load-displacement curve.

[0014] In one embodiment, the elastic modulus calculation formula is:

[0015]

[0016] In the formula, E represents the elastic modulus, C L represents the ultrasonic longitudinal wave intensity, ρ represents the density, and σ represents the calibrated Poisson's ratio.

[0017] In one embodiment, sending a longitudinal wave signal to a solid propellant grain in the engine outside the engine and receiving an echo signal, and then determining the ultrasonic longitudinal wave velocity in the solid propellant grain according to the echo signal includes the following steps:

[0018] A longitudinal wave signal is generated by exciting a signal generator outside the engine;

[0019] The voltage of the longitudinal wave signal is amplified by at least 200 times through a power amplifier and then transmitted to a transceiver isolation duplexer;

[0020] The amplified longitudinal wave signal is sent to the ultrasonic transducer arranged on the outer wall of the engine through the transceiver isolator;

[0021] After receiving the echo signal returned by the solid propellant grain, the ultrasonic transducer sends the echo signal to the oscilloscope through the transceiver isolation duplexer;

[0022] The ultrasonic longitudinal wave velocity of the solid propellant grain is determined by an oscilloscope.

[0023] In a second aspect, the present invention further provides a solid propellant grain crack detection method, which is based on the echo signal in the solid propellant grain elastic modulus detection method, and comprises the following steps:

[0024] The echo signal is subjected to noise reduction processing by wavelet transform to obtain a reconstructed signal;

[0025] Filtering drift and background noise of the reconstructed signal by low-pass filtering and / or high-pass filtering;

[0026] Performing Hilbert transform on the filtered reconstructed signal to calculate the envelope of the signal;

[0027] Using a peak detection algorithm to identify wave packets in the envelope and determine the arrival time of the wave packets;

[0028] Based on the ultrasonic longitudinal wave velocity and the arrival time of the wave packet, the distance of the ultrasonic longitudinal wave reaching the wave packet is calculated;

[0029] The distance of the ultrasonic longitudinal wave reaching the wave packet is compared with the thickness of the solid propellant grain to determine whether there are cracks in the solid propellant.

[0030] In one embodiment, performing noise reduction processing on the echo signal by wavelet transform comprises the following steps:

[0031] Decompose the echo signal through wavelet transform to obtain wavelet coefficients of multiple scales;

[0032] Removing noise components of wavelet coefficients based on a preset threshold;

[0033] The inverse wavelet transform is performed on the wavelet coefficients after noise removal to obtain the reconstructed signal.

[0034] In one of the embodiments, the distance of the ultrasonic longitudinal wave arriving at the wave packet is compared with the thickness of the solid propellant grain to determine whether the solid propellant grain has a crack. If the distance of the ultrasonic longitudinal wave arriving at the wave packet is less than the thickness of the solid propellant grain, then the solid propellant grain has a crack; if the distance of the ultrasonic longitudinal wave arriving at the wave packet is greater than or equal to the thickness of the solid propellant grain, then the solid propellant grain has no crack.

[0035] In one embodiment, the peak detection algorithm is a findpeaks algorithm.

[0036] In one embodiment, the low-pass filtering is performed using a low-pass Butterworth filter with a cutoff frequency of 0.1 Hz, and the high-pass filtering is performed using a high-pass Butterworth filter with a cutoff frequency of 10 Hz.

[0037] In a third aspect, the present invention further provides a solid propellant grain elastic modulus detection and crack detection system for executing the above-mentioned solid propellant grain elastic modulus detection method and the above-mentioned solid propellant grain crack detection method.

[0038] The beneficial effects of the present invention are:

[0039] (1) In the present invention, the solid propellant raw material is used to determine the calibrated Poisson's ratio, and then the ultrasonic longitudinal wave velocity in the solid propellant grain is determined using the echo signal. Based on the two, the real-time elastic modulus of the grain can be calculated, thereby realizing the detection of the real-time elastic modulus of the solid propellant grain.

[0040] (2) In the present invention, the echo signal is first subjected to noise reduction processing, and then the envelope is calculated, the wave packet is identified, and the distance of the ultrasonic longitudinal wave reaching the wave packet is calculated according to the wave packet arrival time and the ultrasonic longitudinal wave velocity. This distance is compared with the grain thickness to determine whether the grain has cracks. The whole process can detect cracks in the entire solid propellant grain including its internal structure without destroying the integrity of the solid propellant grain, which is fast and has low labor costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram of longitudinal wave velocity measurement provided in an embodiment of the present invention;

[0042] Figure 2 It is a schematic diagram of the relationship between the solid propellant grain elastic modulus detection and crack detection system provided in an embodiment of the present invention and the engine assembly. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0044] In one embodiment, Figure 1 As shown, the solid propellant grain elastic modulus detection method of this embodiment includes the following steps:

[0045] S101. Perform mechanical testing on solid propellant raw materials to obtain elastic modulus and ultrasonic longitudinal wave velocity of the solid propellant raw materials.

[0046] Specifically, the mechanical test of the solid propellant raw material is completed in the laboratory. The whole process is well known to those skilled in the art and will not be described in detail here.

[0047] It should be noted that the solid propellant raw material is a part of the solid propellant grain or a parallel storage unit of the solid propellant grain, and is most preferably a parallel storage unit.

[0048] S102. Calculate a calibrated Poisson's ratio based on the elastic modulus of the solid propellant raw material and the ultrasonic longitudinal wave velocity according to the elastic modulus calculation formula.

[0049] The elastic modulus calculation formula is:

[0050]

[0051] In the formula, E represents the elastic modulus, C L represents the ultrasonic longitudinal wave intensity, ρ represents the density, and σ represents the calibrated Poisson's ratio.

[0052] The density of solid propellant raw material is ρ, which is a known quantity. Based on E, ρ, and CL The quantitative relationship between the Poisson's ratio σ and the Poisson's ratio σ can be calculated. For solid propellant raw materials and the grain prepared by raw material molding, the Poisson's ratio remains unchanged.

[0053] S103, sending longitudinal wave signals to the solid propellant grains in the engine outside the engine and receiving echo signals, and then determining the ultrasonic longitudinal wave velocity in the solid propellant grains according to the echo signals.

[0054] like Figure 1 As shown in the figure, when determining the ultrasonic longitudinal wave velocity in the solid propellant grain based on the echo signal, the longitudinal wave peak is the detection object, and the ultrasonic longitudinal wave velocity is calculated by identifying the time difference of the first echo peak. The transmission distance of the first echo is 2d, and the time is t1, and the ratio of the two is the longitudinal wave velocity.

[0055] S104. Based on the calibrated Poisson's ratio and the ultrasonic longitudinal wave velocity in the solid propellant grain, the elastic modulus of the solid propellant grain is calculated according to the elastic modulus calculation formula.

[0056] In this embodiment, the Poisson's ratio is used as the medium calibration quantity, so that the real-time elastic modulus detection of the drug column can be achieved, and the calculation process is simple.

[0057] In one embodiment, the solid propellant raw material is subjected to mechanical testing to obtain the elastic modulus of the solid propellant raw material, including:

[0058] S201. Perform a tensile test on the solid propellant raw material to obtain a tensile load-displacement curve of the solid propellant raw material.

[0059] S202. Calculate and obtain the elastic modulus of the solid propellant raw material based on the tensile load-displacement curve.

[0060] In one embodiment, sending a longitudinal wave signal to a solid propellant grain in the engine outside the engine and receiving an echo signal, and then determining the ultrasonic longitudinal wave velocity in the solid propellant grain according to the echo signal includes the following steps:

[0061] S301, generating a longitudinal wave signal by exciting a signal generator outside the engine.

[0062] S302, amplify the voltage of the longitudinal wave signal by at least 200 times through a power amplifier and then transmit it to a transceiver isolation duplexer.

[0063] The signal is amplified 200 times by a power amplifier to ensure that the signal has enough energy to stimulate ultrasonic propagation in the propellant.

[0064] S303, sending the amplified longitudinal wave signal to the ultrasonic transducer arranged on the outer wall of the engine through the transceiver isolator.

[0065] During this process, the ultrasonic waves emitted by the ultrasonic transducer will propagate in the solid propellant grain. Cracks or damage will cause reflection, scattering or attenuation of the ultrasonic signal, thereby producing characteristic changes in the echo signal and forming a wave packet.

[0066] S304, after receiving the echo signal returned by the solid propellant grain, the ultrasonic transducer sends the echo signal to the oscilloscope through the transceiver isolation duplexer.

[0067] Ultrasonic longitudinal waves propagate in solid propellant grains and are affected by the internal structure and physical properties of the solid propellant grains during the transmission process. The characteristics of the echo signal reflect the internal structure and defects of the solid propellant grains.

[0068] S305, determining the ultrasonic longitudinal wave velocity of the solid propellant grain through an oscilloscope. The received echo signal is read through the oscilloscope, and the oscilloscope converts the signal into a visual waveform to provide data support for subsequent analysis.

[0069] The solid propellant grain elastic modulus detection method of the present embodiment can calculate the real-time elastic modulus of the solid propellant grain based on the calibrated Poisson's ratio and the ultrasonic longitudinal wave velocity in the solid propellant grain.

[0070] Based on the same invention, the present invention also provides a solid propellant grain crack detection method, which is based on the echo signal in the solid propellant grain elastic modulus detection method, and includes the following steps:

[0071] S401 , performing noise reduction processing on the echo signal by wavelet transform to obtain a reconstructed signal.

[0072] The noise reduction process of the echo signal by wavelet transform includes the following steps:

[0073] S501 . Decompose the echo signal through wavelet transform to obtain wavelet coefficients of multiple scales.

[0074] S502: Remove noise components of the wavelet coefficients based on a preset threshold.

[0075] S503: Perform inverse wavelet transform on the wavelet coefficients after noise removal to obtain a reconstructed signal.

[0076] S402: Filter the drift and background noise of the reconstructed signal by low-pass filtering and / or high-pass filtering.

[0077] Specifically, the low-pass filtering is performed using a low-pass Butterworth filter with a cut-off frequency of 0.1 Hz, and the high-pass filtering is performed using a high-pass Butterworth filter with a cut-off frequency of 10 Hz.

[0078] S403, performing Hilbert transform on the filtered reconstructed signal to calculate the envelope of the signal.

[0079] S404: Use a peak detection algorithm to identify the wave packets in the envelope and determine the arrival time of the wave packets.

[0080] The peak detection algorithm is the findpeaks algorithm. According to the characteristics of ultrasonic propagation, it will give a relatively strong echo when encountering cracks or damage. This echo signal is the wave packet.

[0081] S405. Based on the ultrasonic longitudinal wave velocity and the arrival time of the wave packet, the distance of the ultrasonic longitudinal wave reaching the wave packet is calculated. The distance of the ultrasonic longitudinal wave reaching the wave packet is the distance of the ultrasonic wave reaching the crack. It should be noted that when the ultrasonic wave reaches the other side of the side wall of the solid propellant grain, the side wall is also regarded as a crack and a wave packet is also generated.

[0082] Specifically, the distance calculation formula in step S405 is distance = longitudinal wave velocity C L × arrival time / 2. The distance is the actual distance that the first direct wave of the ultrasonic longitudinal wave propagates to the crack.

[0083] S406. Compare the distance of the ultrasonic longitudinal wave reaching the wave packet with the thickness of the solid propellant grain to determine whether there is a crack in the solid propellant grain.

[0084] Among them, the distance of the ultrasonic longitudinal wave arriving at the wave packet and the thickness of the solid propellant grain are compared to determine whether the solid propellant grain has cracks. If the distance of the ultrasonic longitudinal wave arriving at the wave packet is less than the thickness of the solid propellant grain, then the solid propellant grain has cracks; if the distance of the ultrasonic longitudinal wave arriving at the wave packet is greater than or equal to the thickness of the solid propellant grain, then the solid propellant grain has no cracks.

[0085] The solid propellant grain crack detection method of the present invention can perform crack detection on the entire solid propellant grain including its internal structure without destroying the integrity of the solid propellant grain.

[0086] The present invention also provides a solid propellant grain elastic modulus detection and crack detection system for executing the solid propellant grain elastic modulus detection method and the solid propellant grain crack detection method.

[0087] like Figure 2 As shown, the solid propellant grain elastic modulus detection and crack detection system of the present invention includes a signal generator, a rate amplifier, a transceiver isolation duplexer, an oscilloscope, a processing module, and an ultrasonic transducer mounted on the outer wall of the engine filling grain portion.

[0088] The power amplifier is connected to the signal generator, the transceiver isolation duplexer is connected to the power amplifier, the oscilloscope and the ultrasonic transducer, and the processing module is connected to the oscilloscope.

[0089] The engine grain filling part includes the engine casing, the heat insulation layer and the solid propellant grain from the outside to the inside. The processing module is used to perform the crack detection process of the solid propellant grain. The echo signal obtained by the above system can be used to calculate the real-time elastic modulus of the solid propellant grain.

[0090] The solid propellant grain elastic modulus detection and crack detection system of the present invention can obtain echo signals to calculate the elastic modulus of the solid propellant grain and detect cracks.

[0091] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for detecting elastic modulus of solid propellant grain, characterized in that: The following steps are involved: Performing mechanical testing on the solid propellant raw material to obtain the elastic modulus and ultrasonic longitudinal wave velocity of the solid propellant raw material; The calibrated Poisson's ratio is calculated based on the elastic modulus of the solid propellant raw material and the ultrasonic longitudinal wave velocity according to the elastic modulus calculation formula; Sending longitudinal wave signals to the solid propellant grains in the engine outside the engine and receiving echo signals, and then determining the ultrasonic longitudinal wave velocity in the solid propellant grains according to the echo signals; The elastic modulus of the solid propellant grain is obtained by calculating according to an elastic modulus calculation formula based on the calibrated Poisson's ratio and the ultrasonic longitudinal wave velocity in the solid propellant grain.

2. The method for detecting elastic modulus of solid propellant grain according to claim 1, characterized in that: The solid propellant raw material is subjected to mechanical testing to obtain the elastic modulus of the solid propellant raw material, including: Performing a tensile test on the solid propellant raw material to obtain a tensile load-displacement curve of the solid propellant raw material; The elastic modulus of the solid propellant raw material is calculated based on the tensile load-displacement curve.

3. The method for detecting elastic modulus of solid propellant grain according to claim 2, characterized in that: The elastic modulus calculation formula is: In the formula, E represents the elastic modulus, C L represents the ultrasonic longitudinal wave intensity, ρ represents the density, and σ represents the calibrated Poisson's ratio.

4. The method for detecting the elastic modulus of a solid propellant grain according to claim 2 or 3, characterized in that: The method of sending a longitudinal wave signal to a solid propellant grain in the engine outside the engine and receiving an echo signal, and then determining the ultrasonic longitudinal wave velocity in the solid propellant grain according to the echo signal comprises the following steps: A longitudinal wave signal is generated by exciting a signal generator outside the engine; Amplifying the voltage of the longitudinal wave signal by at least 200 times through a power amplifier and transmitting the amplified voltage to a transceiver isolation duplexer; The amplified longitudinal wave signal is sent to the ultrasonic transducer arranged on the outer wall of the engine through the transceiver isolator; After receiving the echo signal returned by the solid propellant grain, the ultrasonic transducer sends the echo signal to the oscilloscope through the transceiver isolation duplexer; The ultrasonic longitudinal wave velocity of the solid propellant grain is determined by the oscilloscope.

5. A method for detecting cracks in solid propellant grains, characterized in that: Based on the echo signal in the solid propellant grain elastic modulus detection method according to any one of claims 1 to 4, the method comprises the following steps: The echo signal is subjected to noise reduction processing by wavelet transform to obtain a reconstructed signal; Filtering the drift and background noise of the reconstructed signal by low-pass filtering and / or high-pass filtering; Performing Hilbert transform on the filtered reconstructed signal to calculate the envelope of the signal; Using a peak detection algorithm to identify wave packets in the envelope and determine the arrival time of the wave packets; Based on the ultrasonic longitudinal wave velocity and the arrival time of the wave packet, the distance of the ultrasonic longitudinal wave reaching the wave packet is calculated; The distance of the ultrasonic longitudinal wave reaching the wave packet is compared with the thickness of the solid propellant grain to determine whether there are cracks in the solid propellant.

6. The solid propellant grain crack detection method according to claim 5, characterized in that: The noise reduction process of the echo signal by wavelet transform comprises the following steps: Decompose the echo signal through wavelet transform to obtain wavelet coefficients of multiple scales; Removing noise components of the wavelet coefficients based on a preset threshold; The inverse wavelet transform is performed on the wavelet coefficients after noise removal to obtain the reconstructed signal.

7. The solid propellant grain crack detection method according to claim 5, characterized in that: The comparison of the distance of the ultrasonic longitudinal wave arriving at the wave packet and the thickness of the solid propellant grain to determine whether the solid propellant grain has a crack is as follows: if the distance of the ultrasonic longitudinal wave arriving at the wave packet is less than the thickness of the solid propellant grain, then the solid propellant grain has a crack; if the distance of the ultrasonic longitudinal wave arriving at the wave packet is greater than or equal to the thickness of the solid propellant grain, then the solid propellant grain has no crack.

8. The solid propellant grain crack detection method according to claim 5, characterized in that: The peak detection algorithm is the findpeaks algorithm.

9. The solid propellant grain crack detection method according to claim 5, characterized in that: The low-pass filtering is performed using a low-pass Butterworth filter with a cut-off frequency of 0.1 Hz, and the high-pass filtering is performed using a high-pass Butterworth filter with a cut-off frequency of 10 Hz.

10. A solid propellant grain elastic modulus detection and crack detection system, characterized in that: Used to perform the solid propellant grain elastic modulus detection method as described in any one of claims 1 to 4 and the solid propellant grain crack detection method as described in any one of claims 5 to 9.

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