CN108444938B - Terahertz imaging solid rocket engine interface debonding defect detection method and system - Google Patents
Terahertz imaging solid rocket engine interface debonding defect detection method and system Download PDFInfo
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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- G01N21/3581—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation
- G01N21/3586—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation by Terahertz time domain spectroscopy [THz-TDS]
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Abstract
The invention provides a terahertz imaging solid rocket engine interface debonding defect detection method and system, which comprises the following steps: step S1: controlling the transmission frequency at f1～f2Sweeping the surface of a solid rocket engine to be measured by a terahertz wave source of a continuous frequency modulation terahertz wave signal which changes between the continuous frequency modulation terahertz wave signals, wherein f1+f2≥150GHz，f2‑f1Not less than 6 GHz; step S2: and detecting the interface debonding defect of the solid rocket engine based on the terahertz wave signal reflected by the surface of the solid rocket engine to be detected during frequency sweeping. The detection method and the system can detect and judge whether debonding exists between the composite material shell and the fuel column of the solid rocket engine, have compact system structure, can realize all-weather all-region all-time use, do not need redundant matching consumables and protective equipment, have convenient and quick detection, visual detection effect and strong practicability, can effectively reduce the detection cost and improve the production efficiency.
Description
Technical Field
The invention relates to the technical field of quality control detection of solid rocket engines, in particular to a device and a method for detecting gap trap between a solid rocket engine shell and a fuel column.
Background
With the development of science and technology, more and more medium composite materials are used for various types of solid rocket engines, and the performance of the solid rocket engines is effectively improved. In application, due to the reasons of multiple aspects such as materials, manufacturing, pressing processes and the like, an integral debonding gap or a local debonding gap often exists between a solid rocket engine shell and a fuel column, and some gaps are even completely separated, so that the integral performance of the engine is influenced, huge potential safety hazards are caused, especially for large-scale equipment and systems with high reliability requirements and long storage service life, the defect is very critical to the integral reliability evaluation of the system, and no efficient portable equipment and method for the integral debonding evaluation of the large-scale composite material shell solid rocket engine exist so far.
For the problems, the existing general X-ray imaging technology can effectively detect the gap defects, but the detection speed is low, so that the full coverage of the area cannot be realized, and the time cost and the efficiency cost are extremely high; meanwhile, radiation injury exists to a certain degree on users, and the protection cost and potential risk of personnel injury are high; the device is heavy, is not suitable for outdoor portable detection, and cannot meet the use requirements of all weather, all regions and all time periods; therefore, a non-contact nondestructive testing device and method which are convenient to use, work all the day long, and have intuitive effect are urgently needed.
Three-dimensional terahertz imaging technology developed in recent years includes time-of-flight imaging, computer-aided tomography, diffraction tomography, fresnel lens imaging, holographic imaging and other methods. Time-of-flight imaging can give the surface topography of an object or three-dimensional structures at different levels, but it cannot show the distribution of non-laminar structures inside the object. In computer-aided tomography, the diameter of the terahertz wave focal point needs to be smaller than the spatial resolution required by tomography, and the focal depth needs to be larger than the size of an object to be imaged. In diffraction tomography, the spatial frequency of an image in a low-frequency region is low, and the signal-to-noise ratio of terahertz waves used for imaging in a high-frequency region is low, so that the problem of poor quality exists in both the low-frequency region and the high-frequency region. The transverse resolution of the Fresnel lens three-dimensional imaging is limited by the diffraction of an imaging system, and the longitudinal resolution is limited by the spectral resolution of a carrier; in addition, the distance between the two object planes of the object to be measured is larger than the depth of field of the imaging system, so that the respective images do not interfere with each other, and therefore, the imaging quality is also influenced by the depth of field of the imaging system. Three-dimensional holography does not image very complex targets nor extract the spectral information of an object, in any case it does not provide accurate refractive index data for reconstructing the target. In addition, in consideration of practicability, the methods are limited by the existing hardware conditions, and therefore, the information of the debonding gap between the thick shell of the large-sized component and the fuel column cannot be effectively acquired, and the practicability is not achieved.
Disclosure of Invention
The invention aims to detect the debonding defect inside the solid rocket engine outside the solid rocket engine on the premise of not damaging or disassembling the solid rocket engine, and provides a method for detecting the debonding gap defect of the solid rocket engine interface, which has strong practicability, wide applicability range and no radiation damage to human bodies.
The invention provides a method for detecting the defect of a debonding gap of a solid rocket engine interface, which comprises the following steps:
step S1: controlling the transmission frequency at f1~f2Sweeping the surface of a solid rocket engine to be measured by a terahertz wave source of a continuous frequency modulation terahertz wave signal which changes between the continuous frequency modulation terahertz wave signals, wherein f1+f2≥150 GHz，f2-f1≥6 GHz；
Step S2: and detecting the interface debonding defect of the solid rocket engine based on the terahertz wave signal reflected by the surface of the solid rocket engine to be detected during frequency sweeping.
As a preferable scheme, the step S1 further includes:
step S11: acquiring a frequency at f1~f2A terahertz wave source of a continuous frequency-modulated terahertz wave signal varying therebetween, wherein f1+f2≥150 GHz，f2-f1≥6 GHz；
Step S12: collimating and parallelly converging a terahertz wave signal emitted by the terahertz wave source to the surface of the solid rocket engine to be detected;
step S13: and controlling the collimation parallel terahertz wave signals to scan the surface of the solid rocket engine to be tested in the x and y directions in a two-dimensional scanning mode.
As a preferable scheme, the step S2 further includes:
step S21: when frequency sweeping is carried out, the parallel terahertz wave signals are collimated and reflected on the surface of the solid rocket engine to be tested, the reflected terahertz wave signals are detected and mixed into intermediate frequency signals, data processing is carried out on the intermediate frequency signals to obtain one-dimensional imaging arrays corresponding to each scanning position, after the terahertz wave source is controlled in a two-dimensional scanning mode to carry out scanning in the x direction and the y direction on the surface of the solid rocket engine to be tested, a three-dimensional imaging data array formed by a plurality of the one-dimensional imaging arrays is obtained, and an x-y direction imaging graph corresponding to the sample to be tested is output according to the three-dimensional imaging data array.
As a preferable scheme, the step S2 further includes:
step S22: and if the imaging image in the x-y direction has fringe distribution, then debonding defects exist, and if the imaging image in the x-y direction has no fringe distribution, then debonding defects do not exist.
The invention also provides a terahertz imaging solid rocket engine interface debonding defect detection system, which comprises:
terahertz wave transmitter for transmitting at frequency f1~f2A continuous frequency-modulated terahertz wave signal of which f is changed1+ f2≥150 GHz，f2-f1≥6 GHz；
The terahertz wave collimating device is connected with the signal output end of the terahertz wave transmitter and is used for collimating and parallelly converging the terahertz wave signal to the surface of the solid rocket engine to be detected;
the terahertz frequency mixer comprises a first signal input end, a second signal input end and a signal output end; the first signal input end is connected with the terahertz wave transmitter and used for receiving a synchronous reference signal transmitted by the terahertz wave transmitter; the second signal input end is used for receiving terahertz wave signals which are collimated and converged to the surface of the solid rocket engine to be measured in parallel to be reflected; the terahertz frequency mixer receives a synchronous reference signal emitted by the terahertz wave emitter and obtains an intermediate frequency signal by the reflected terahertz wave frequency mixer;
the two-dimensional scanning device controls the collimated and parallel terahertz wave signals to scan the surface of the solid rocket engine to be detected in the x and y directions in a two-dimensional scanning mode;
the data acquisition device is used for receiving the intermediate frequency signal output by the terahertz frequency mixer and converting the intermediate frequency signal into a digital signal;
and the imaging processing device is used for receiving the digital signals, processing the digital signals to obtain a one-dimensional imaging array corresponding to each scanning position of the two-dimensional scanning device, controlling the terahertz wave signals parallel to the collimation in a two-dimensional scanning mode to scan the surface of the solid rocket engine to be detected in the x and y directions to obtain a three-dimensional imaging data array formed by a plurality of one-dimensional imaging arrays, and outputting an x-y direction imaging graph corresponding to the sample to be detected according to the three-dimensional imaging data array.
As a preferred scheme, the data acquisition device comprises a first data acquisition end and a second data acquisition end, the first data acquisition end is connected with a signal output end of the terahertz frequency mixer, and the signal output end of the data acquisition device is connected with a signal input end of the imaging processing device and is used for acquiring an intermediate frequency signal obtained by frequency mixing of the terahertz frequency mixer and transmitting the intermediate frequency signal to the imaging processing device; and the second data acquisition end is connected with the signal synchronization end of the terahertz transmitter.
As a preferable scheme, the method further comprises the following steps:
the terahertz beam splitter is arranged between the terahertz wave collimating device and the terahertz frequency mixer and arranged at an angle of 45 degrees with the transmission direction of the terahertz wave signal reflected by the surface of the solid rocket engine to be tested, and the terahertz wave signal reflected by the surface of the solid rocket engine to be tested is reflected to the direction perpendicular to the original transmission direction through the terahertz beam splitter and is received by the terahertz frequency mixer.
As a preferred solution, the terahertz wave collimating device includes a first parabolic mirror and a second parabolic mirror; the first parabolic mirror and the second parabolic mirror are arranged between the terahertz wave transmitter and the solid rocket engine to be tested in parallel; the terahertz beam splitter is arranged between the first parabolic mirror and the second parabolic mirror; the terahertz wave signal emitted by the terahertz wave emitter is collimated into parallel light by the first parabolic mirror and is converged to the surface of the solid rocket engine to be tested through the second parabolic mirror, and the terahertz wave signal is reflected on the surface of the solid rocket engine to be tested, passes through the second parabolic mirror, is reflected to the direction perpendicular to the original transmission direction through the terahertz beam splitter, and is received by the terahertz frequency mixer.
Preferably, the emission period of the terahertz wave emitter is T, and the terahertz wave signal emitted by the terahertz wave emitter is controlled by the frequency f1Change to f2Time of tsWherein t iss< T; the dwell time of the two-dimensional scanning device at each scanning position is NT, wherein N is an integer greater than or equal to 1; the second mentionedAnd the dimension scanning device defines a plane parallel to the surface of the solid rocket engine to be detected as an x-y plane formed by the directions of x and y.
As a preferable scheme, the scanning precision of the two-dimensional scanning device in the x and y directions is 0.1-20 mm; t is 10-500 microseconds; n is 1-1024; t is ts=0.8T。
The third purpose of the invention is to provide an application of the terahertz imaging solid rocket engine interface debonding defect detection system in debonding defect detection between a housing and a fuel column of a solid rocket engine.
Preferably, the housing of the solid rocket engine is a housing with a multilayer interface structure formed by glass fiber, ceramic, resin, inorganic compound or rubber through a pressing, winding or die casting process.
Preferably, the housing of the solid rocket engine is a housing having a planar layer interface, a cylindrical layer interface, or a random-shaped layer interface structure.
The invention has the beneficial effects that: the invention is based on terahertz interference imaging technology to detect the interface debonding defect of the solid rocket engine, and because terahertz waves have the characteristics of strong penetrability, high use safety, good directionality, high bandwidth, small released energy, no harmful photoionization on human bodies and the like, the detection system of the invention can penetrate through the thicker shell of the solid rocket engine to effectively detect whether the debonding defect exists on the interface between the shell of the solid rocket engine and a fuel column, and the detection method of the invention has high accuracy and good reproducibility, does not cause radiation damage to human bodies, and simultaneously has compact structure, can realize all-weather all-time use in all regions, does not need redundant matching consumables and protective equipment, is convenient and fast to detect, is suitable for various types of solid rocket engines, and has strong practicability, the detection cost can be reduced, and the production efficiency is improved.
Drawings
FIG. 1 is a schematic structural diagram of a system for detecting debonding gap defects at an interface of a solid-rocket engine according to the present invention;
FIG. 2a is an image of a thin shell plate and a flat block of a simulated thick seam test;
FIG. 2b is an image of a thin seam simulated detection of the oblique seam between the thick housing plate and the flat block;
FIG. 3a is a test piece detection imaging diagram of simulation of a thick shell plate and a flat medicine block oblique seam.
Description of reference numerals:
100-a solid rocket engine to be tested; 101-a terahertz wave transmitter; 102-a first parabolic mirror;
103-a second parabolic mirror; 104-a third parabolic mirror; 105-a terahertz beam splitter;
106-terahertz frequency mixer; 107-data acquisition means; 108-two-dimensional scanning means;
109-image processing means.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly described below, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.
The invention provides a terahertz imaging solid rocket engine interface debonding defect detection method, which comprises the following steps:
step S1: controlling the transmission frequency at f1~f2Sweeping the surface of a solid rocket engine to be measured by a terahertz wave source of a continuous frequency modulation terahertz wave signal which changes between the continuous frequency modulation terahertz wave signals, wherein f1+f2≥150 GHz，f2-f1≥6 GHz；
Step S2: and detecting the interface debonding defect of the solid rocket engine based on the terahertz wave signal reflected by the surface of the solid rocket engine to be detected during frequency sweeping.
The invention is based on the detection of debonding gap defect by terahertz interference imaging technology, and researches prove that the specific frequency (namely f) provided by the invention1、f2Respectively satisfy f1+ f2≥150 GHz，f2-f1Frequency in the condition range of more than or equal to 6 GHz), can penetrate through the shell of a thicker solid rocket engine, and is stably reflected by an internal fuel column interface, an imaging graph with higher accuracy is obtained by receiving and processing by the imaging processing device 109, and the defect of the interface debonding gap of the solid rocket engine can be effectively detected.
Further, the step S1 further includes:
step S11: acquiring a frequency at f1~f2A terahertz wave source of a continuous frequency-modulated terahertz wave signal varying therebetween, wherein f1+f2≥150 GHz，f2-f1≥6 GHz；
Step S12: collimating and parallelly converging a terahertz wave signal emitted by the terahertz wave source to the surface of the solid rocket engine to be detected;
step S13: and controlling the collimation parallel terahertz wave signals to scan the surface of the solid rocket engine to be tested in the x and y directions in a two-dimensional scanning mode.
Further, the step S2 further includes: during scanning, the terahertz wave signals which are collimated, parallel and then converged are reflected on the surface of the solid rocket engine to be detected, the reflected terahertz wave signals are detected and mixed into intermediate frequency signals, data processing is carried out on the intermediate frequency signals to obtain a one-dimensional imaging array corresponding to each scanning position, after the terahertz wave source is controlled in a two-dimensional scanning mode to carry out scanning in the x direction and the y direction on the surface of the solid rocket engine to be detected, a three-dimensional imaging data array formed by a plurality of the one-dimensional imaging arrays is obtained, and an x-y direction imaging graph corresponding to the sample to be detected is output according to the three-dimensional imaging data array.
Further, the step S2 further includes:
step S22: and if the imaging image in the x-y direction has fringe distribution, then debonding defects exist, and if the imaging image in the x-y direction has no fringe distribution, then debonding defects do not exist. One is no gap at all, and there is no streaking; the other condition is that the thickness of the debonding gaps existing at all detected positions is completely consistent, and no stripes are distributed. The second case hardly occurs in an actual production activity, and therefore, when the image result generated by the detection has no stripe distribution, it can be considered that there is no debonding of the detected engine.
The detection method of the invention is based on the terahertz interference imaging technology to detect the interface debonding defect of the solid rocket engine, and as the terahertz wave has the characteristics of strong penetrability, high use safety, good directionality, high bandwidth, very small released energy, no harmful photoionization on human bodies and the like, the detection system of the invention can penetrate through the thicker shell of the solid rocket engine to effectively detect whether the debonding defect exists on the interface between the shell of the solid rocket engine and the fuel column, and the detection method of the invention has high accuracy and good repeatability, does not cause radiation damage to human bodies, and simultaneously has compact structure, can realize all-weather all-terrain all-time use, does not need redundant matching consumables and protective equipment, is convenient and fast to detect, and is suitable for various types of solid rocket engines, the practicality is strong, can reduce the detection cost, improves production efficiency.
The invention provides a terahertz imaging solid rocket engine interface debonding defect detection system, which refers to fig. 1 and comprises:
And the terahertz wave collimating device is connected with the signal output end of the terahertz wave transmitter and is used for collimating and parallelly converging the terahertz wave signal to the surface of the solid rocket engine 100 to be detected.
A terahertz mixer 106 including a first signal input terminal, a second signal input terminal, and a signal output terminal; the first signal input end is connected with the terahertz wave transmitter 101 and used for receiving a synchronous reference signal transmitted by the terahertz wave transmitter; the second signal input end is used for receiving terahertz wave signals which are collimated and converged to the surface of the solid rocket engine 100 to be measured in parallel and reflected; the terahertz mixer 106 receives the synchronous reference signal emitted by the terahertz transmitter 101 and the reflected terahertz mixer 106 to obtain an intermediate frequency signal.
Specifically, a part of the terahertz wave signal emitted by the terahertz wave emitter 101 is divergently transmitted to a free space, and is collimated into parallel light by the terahertz wave collimating device, and the terahertz wave mixer 106 receives the terahertz wave signal reflected by the surface of the solid rocket engine 100 to be measured and mixes with the reference signal emitted by the terahertz wave emitter 101 to obtain an intermediate frequency signal. The intermediate frequency signals are subjected to fast Fourier transform processing to obtain a z-direction target one-dimensional image, and the depth position of the defect can be reflected.
And the two-dimensional scanning device 108 controls the collimated and parallel terahertz wave signals to scan the surface of the solid rocket engine 100 to be detected in the x and y directions in a two-dimensional scanning mode.
And the data acquisition device 107 is used for receiving the intermediate frequency signal output by the terahertz mixer and converting the intermediate frequency signal into a digital signal.
The imaging processing device 109 is configured to receive the digital signal, process the digital signal to obtain a one-dimensional imaging array corresponding to each scanning position of the two-dimensional scanning device 108, control the terahertz wave signal parallel to the collimation in a two-dimensional scanning manner to scan the surface of the solid rocket engine 100 to be detected in the x and y directions, obtain a three-dimensional imaging data array formed by a plurality of the one-dimensional imaging arrays, and output an x-y direction imaging diagram corresponding to the sample to be detected according to the three-dimensional imaging data array.
Specifically, the emission period of the terahertz wave emitter is T, and the terahertz wave signal emitted by the terahertz wave emitter is controlled by the frequency f1Change to f2Time of tsWherein t iss< T; the dwell time of the two-dimensional scanning device at each scanning position is NT, wherein N is an integer greater than or equal to 1; the two-dimensional scanning device 108 defines a plane parallel to the surface of the solid rocket engine 100 to be measured as an x-y plane formed in x and y directions. The faster the set period, the faster the measurement speed, and due to the limit limitation of the response time, the x and y direction scanning accuracy of the two-dimensional scanning device is preferably 0.1-20 mm, more preferably 0.5mm, the x-y size of the minimum defect which can be detected with the accuracy of 0.5mm is 0.5mm × 0.5mm, and the defect area which can be effectively identified is more than 2mm × 2 mm. T is preferably 10-500 microseconds; n is preferably 1 to 1024, more preferably 256; t is ts<T, preferably Ts=0.8T。
The imaging processing apparatus 109 includes a data processing unit and an image generating unit, which respectively realize their functions by compiling software codes in a codeable chip and automatically generate a multidimensional map by a computer.
The invention is based on the detection of debonding defect by terahertz interference imaging technology, and the terahertz wave emitter 101 emits specific frequency (i.e. f)1、f2Respectively satisfy f1+ f2≥150 GHz，f2-f1Frequency in the range of more than or equal to 6 GHz), can pass through the shell of a thicker solid rocket engine, is stably reflected by an internal fuel column interface, is received and processed by the imaging processing device 109 to obtain an imaging graph with higher accuracy, and can be used for the solid rocket engineThe method has the advantages of good directionality, high accuracy, high repeatability, high emitted frequency bandwidth, small released energy, low cost and no radiation damage to human bodies. The detection system disclosed by the invention is compact in structure, can be used all weather and all regions at all time, does not need redundant matching consumables and protective equipment, is convenient and quick to detect, is suitable for various types of solid rocket engines, is strong in practicability, can reduce the detection cost and improves the production efficiency.
As a preferred embodiment of the present invention, in this embodiment, the acquisition device 107 includes a first data acquisition end and a second data acquisition end, the first data acquisition end is connected to the signal output end of the terahertz frequency mixer 106, the signal output end of the data acquisition device 107 is connected to the signal input end of the imaging processing device 109, and is configured to acquire an intermediate frequency signal obtained by frequency mixing of the terahertz frequency mixer 106 and convert the intermediate frequency signal into a digital signal, and transmit the digital signal to the imaging processing device 109; the second data acquisition end is connected with the signal synchronization end of the terahertz transmitter 101.
The intermediate frequency signal output by the terahertz mixer 106 passes through the data acquisition device 107, realizes multi-cycle acquisition and outputs an average signal, and further generates a visual image result. The imaging processing device 109 can synchronously control the data acquisition device 107 and the two-dimensional scanning device 108 to synchronously coordinate. Further, the data acquisition device 107 can also be connected with the terahertz wave transmitter 101 for signal synchronous acquisition. The imaging processing device 109 can visually display the three-dimensional data acquired by the system device and display the three-dimensional data in three coordinate dimensions of xy, yz and xz.
The data acquisition device 107 outputs synchronous TTL pulses with a pulse period equal to the period T of the sawtooth power supply, e.g., the voltage variation range of the sawtooth power supply is V within the period Tmin-VmaxUsually, the absolute voltage amplitude is not more than 24 volts, the falling edge or rising edge of TTL pulse corresponds to the data recording starting point, and the voltage v can be corresponded to by phase adjustment1Voltage v1Corresponding signal source output frequency f1Corresponding to time t1The data recording end point is determined by the data recording time length of the data acquisition device 107 or the data length selected during data processing, and the signal frequency range corresponding to the optimal data is f1-f2Corresponding to a time length of ts，f2The corresponding time is t2At a voltage v2。
As a preferred embodiment of the present invention, in this embodiment, the present invention further includes a terahertz beam splitter 105, the terahertz beam splitter 105 is disposed between the terahertz wave collimating device and the terahertz frequency mixer 106, and is disposed at an angle of 45 ° with respect to the transmission direction of the terahertz wave signal after the surface of the solid rocket engine 100 to be measured is launched, and the terahertz wave signal reflected on the surface of the solid rocket engine 100 to be measured is reflected to the direction perpendicular to the original transmission direction by the terahertz beam splitter 105 and is received by the terahertz frequency mixer 106. The terahertz beam splitter 105 can randomly change the route of the reflected terahertz wave high-frequency signal, can be conveniently detected and received by other devices, and is more flexible in arrangement. The terahertz beam splitter 105 and the transmission direction of the terahertz wave signal emitted from the surface of the solid rocket engine 100 to be measured are arranged at an angle of 45 degrees, so that the terahertz wave signal can be reflected to the direction perpendicular to the original path reflection, the terahertz wave can be collimated, and high-quality data which can reflect the information of the debonding condition in the solid rocket engine 100 to be measured more clearly can be obtained.
As a preferred embodiment of the present invention, in this embodiment, the terahertz wave collimating device includes a first parabolic mirror 102 and a second parabolic mirror 103, and the first parabolic mirror 102 and the second parabolic mirror 103 are arranged in parallel between the terahertz wave emitter 101 and the solid rocket engine 100 to be measured; the terahertz beam splitter is arranged between the first parabolic mirror 102 and the second parabolic mirror 103; the first parabolic mirror 102 collimates the terahertz wave signal emitted by the terahertz wave emitter 101 into parallel light, and the parallel light is converged to the surface of the solid rocket engine 100 to be measured through the second parabolic mirror 103, and the terahertz wave signal is reflected on the surface of the solid rocket engine 100 to be measured, passes through the second parabolic mirror 103, is reflected to the direction perpendicular to the original path reflection through the terahertz beam splitter 105, and is received by the terahertz mixer 106. In order to focus the terahertz-wave signal reflected back by the terahertz-wave beam splitter 105, a third parabolic mirror 104 may also be provided between the terahertz-wave beam splitter 105 and the terahertz-wave mixer 106, the third parabolic mirror 104 converging the terahertz-wave signal into the terahertz-wave mixer 106.
Referring to fig. 1, a terahertz wave transmitter 101 transmits a signal at a frequency f1~f2The terahertz wave signals with continuous frequency modulation changed in the process are collimated into parallel light by the first parabolic mirror 102, the parallel light is perpendicular to the surface of the solid rocket engine 100 to be detected, and then is converged to the surface of the solid rocket engine 100 to be detected by the second parabolic mirror 103, the terahertz wave signals penetrate through the surface of the shell to be reflected to the internal fuel column interface and return to the original path by the second parabolic mirror 103, if the conditions of separation and debonding occur between the inside of the shell of the solid rocket engine 100 to be detected and the fuel column interface, the terahertz wave signals returned by the terahertz wave signals are distinguished from the terahertz wave signals returned by a defect-free area, and the debonding condition inside the solid rocket engine is judged through image analysis. The terahertz wave signals reflected back are converted into vertical light through the terahertz beam splitter and converged into the terahertz frequency mixer 106 through the third parabolic mirror 104, synchronous reference signals transmitted by the terahertz wave transmitter 101 drive the terahertz frequency mixer 106 at the same time, the terahertz frequency mixer 106 receives the terahertz wave signals reflected by the surface of the solid rocket engine 100 to be tested and the synchronous reference signals transmitted by the terahertz wave transmitter 101, intermediate frequency signals are obtained after frequency mixing, the two-dimensional scanning device 108 controls the terahertz wave source to traverse all scanning positions of the surface of the solid rocket engine 100 to be tested, the imaging processing device 109 receives the intermediate frequency signals corresponding to each position obtained by scanning of the two-dimensional scanning device 108 and obtains one-dimensional imaging arrays corresponding to each scanning position after processing, when the two-dimensional scanning device 108 controls the terahertz wave transmitting source to traverse all scanning positions of the surface of the solid rocket engine 100 to be tested, obtaining a plurality ofThe one-dimensional imaging array forms a three-dimensional imaging data array, and the imaging processing device 109 outputs an x-y direction imaging diagram corresponding to the surface of the solid rocket engine 100 to be measured according to the three-dimensional imaging data array. And judging whether a gap exists between the solid rocket engine shell and the fuel column or not according to whether the image presented by the x-y direction imaging diagram is in equal-strength stripe distribution or not, wherein if the image is in equal-strength stripe distribution, the gap exists between the solid rocket engine shell and the fuel column, and otherwise, the gap does not exist. Two special cases, one is no gap at all, and no stripe is distributed at the moment; the other condition is that the thickness of the debonding gaps existing at all detected positions is completely consistent, and no stripes are distributed. The second case hardly occurs in an actual production activity, and therefore, when the image result generated by the detection has no stripe distribution, it can be considered that there is no debonding of the detected engine.
The detection system can be applied to detection of the debonding defect of the solid rocket engine interface, is particularly suitable for detecting the debonding defect between the shell of the solid rocket engine and the fuel column, can detect and judge whether debonding exists between the composite material shell of the solid rocket engine and the fuel column, has a compact system structure, can realize all-weather all-terrain all-time use, does not need redundant matching consumables and protective equipment, is convenient and quick to detect, has an intuitive detection effect, is wide in application range and strong in practicability, and can effectively reduce the detection cost. The shell of the solid rocket engine can be a shell with a multilayer interface structure formed by materials such as glass fiber, ceramics, resin, inorganic compounds or rubber through processes such as pressing, winding or die casting, and the shell of the solid rocket engine can be a shell with a plane layer interface, a cylindrical layer interface or an irregular layer interface structure.
Test example 1: simulation detection experiment for inclined seam between thin shell plate and flat medicine block
The invention simulates the defects of the medicine blocks by adding the medicine blocks on the thin plate, and analyzes and demonstrates the imaging effect of the detection system of the invention according to the observed imaging effect.
Forming oblique seams with different angles between the thin shell plate and the flat medicine blocks: oblique sewing: the maximum seam width is 5mm, and the seam length is 100 mm; oblique seam 2: the maximum seam width is 2mm and the seam length is 100 mm. The system measures horizontal stepping by 1mm and vertical stepping by 5mm, and two-dimensional imaging is carried out, wherein an oblique seam (an imaging graph) is shown in a graph 2a and an oblique seam (an imaging graph 2 b).
In the oblique seam: the maximum seam width of the oblique seam is 5mm, the seam length is 100mm, and the known angle of the oblique seam formed by the thin shell plate and the flat medicine block is as follows:
the horizontal measurement angle range of the system is +/-4 degrees, the angle is within the measurement angle range of the system, so that imaging can be performed, and the theoretically available fringe number is as follows: n = d/λ =5mm/0.7mm =7
Oblique seam (II): the maximum seam width of the oblique seam is 2mm, the seam length is 100mm, and the known angle of the oblique seam formed by the thin shell plate and the flat medicine block is as follows:
the horizontal measurement angle range of the system is +/-4 degrees, the angle is within the measurement angle range of the system, so that imaging can be performed, and the theoretically available fringe number is as follows: n = d/λ =2mm/0.7mm =3
As can be seen from fig. 2a, distinct stripes are obtained, the number of stripes in fig. 2a is 7 (white area) and the number of stripes in fig. 2b is 3 (white area), which are completely consistent with the theoretical value, and as the angle decreases, the rate of change of the slit width also decreases, the width change of the stripes becomes slower, the width becomes wider, and is also synchronized with the theory.
Therefore, as can be seen from the simulation detection experiment of the thin shell plate and the inclined seam of the flat medicine block, the detection system can effectively detect the debonding seam, and has higher accuracy and precision and good reproducibility.
Test example 2: simulation detection of thick shell plate and medicine block gap
An oblique seam is formed by a thick plate and a medicine block, a defect simulation experiment of the thick plate is carried out, the horizontal stepping for system measurement is 2mm, the vertical stepping is 5mm, the thick plate is not a plane but a curved surface, the bending angle of the thick plate needs to be controlled within the system measurement angle, the seam between the thick shell plate and the medicine block is formed, and an imaging graph is shown in fig. 3 a.
In the actual simulation, the seam width of the contact part of the thick plate and the medicine block changes faster, and the farther the distance from the contact part is, the smaller the seam width change rate is. The right side of the stripe image obtained in fig. 3a is relatively uniform light and shade stripes, the stripes of the region with slowly changing gaps on the left side are wider than those on the right side, and the displayed image result is consistent with theory, thereby demonstrating that the detection system of the invention can also effectively detect the debonding gap of the thick plate.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (9)
1. A terahertz imaging solid rocket engine interface debonding defect detection method is characterized by comprising the following steps:
step S1: controlling the transmission frequency at f1~f2Sweeping the surface of a solid rocket engine to be measured by a terahertz wave source of a continuous frequency modulation terahertz wave signal which changes between the continuous frequency modulation terahertz wave signals, wherein f1+f2≥150 GHz，f2-f1≥6 GHz；
Step S2: detecting the defect of the debonding gap of the solid rocket engine interface based on the terahertz wave signal reflected by the surface of the solid rocket engine to be detected during frequency sweeping;
wherein the step S1 further includes: step S11: acquiring a frequency at f1~f2A terahertz wave source of a continuous frequency-modulated terahertz wave signal varying therebetween, wherein f1+f2≥150 GHz，f2-f1≥6 GHz；
Step S12: collimating and parallelly converging a terahertz wave signal emitted by the terahertz wave source to the surface of the solid rocket engine to be detected;
step S13: controlling the collimation parallel terahertz wave signals to scan the surface of the solid rocket engine to be tested in the x and y directions in a two-dimensional scanning mode;
wherein the step S2 further includes:
step S21: when frequency sweeping is carried out, the parallel terahertz wave signals are collimated and reflected on the surface of the solid rocket engine to be tested, the reflected terahertz wave signals are detected and mixed into intermediate frequency signals, data processing is carried out on the intermediate frequency signals to obtain a one-dimensional imaging array corresponding to each scanning position, after the terahertz wave source is controlled in a two-dimensional scanning mode to carry out scanning in the x direction and the y direction on the surface of the solid rocket engine to be tested, a three-dimensional imaging data array formed by a plurality of the one-dimensional imaging arrays is obtained, and an x-y direction interference imaging graph corresponding to the surface of the solid rocket engine to be tested is output according to the three-dimensional imaging data array;
step S22: if the interference imaging image in the x-y direction has fringe distribution, the interface between the shell of the solid rocket engine to be tested and the fuel column has debonding gap defect, and if the interference imaging image in the x-y direction has no fringe distribution, the debonding gap defect does not exist.
2. A terahertz imaging solid rocket engine interface debonding defect detection system is characterized by comprising:
terahertz wave transmitter for transmitting at frequency f1~f2A continuous frequency-modulated terahertz wave signal of which f is changed1+f2≥150 GHz，f2-f1≥6 GHz；
The terahertz wave collimating device is connected with the signal output end of the terahertz wave transmitter and is used for collimating and parallelly converging the terahertz wave signal to the surface of the solid rocket engine to be measured;
the terahertz frequency mixer comprises a first signal input end, a second signal input end and a signal output end; the first signal input end is connected with the terahertz wave transmitter and used for receiving a synchronous reference signal transmitted by the terahertz wave transmitter; the second signal input end is used for receiving terahertz wave signals which are collimated and converged to the surface of the solid rocket engine to be measured in parallel to be reflected; the terahertz frequency mixer mixes the received synchronous reference signal transmitted by the terahertz wave transmitter and the reflected terahertz wave signal into an intermediate frequency signal;
the terahertz beam splitter is arranged between the terahertz wave collimating device and the terahertz frequency mixer and arranged at an angle of 45 degrees with the transmission direction of the terahertz wave signal reflected by the surface of the solid rocket engine to be tested, and the terahertz wave signal reflected by the surface of the solid rocket engine to be tested is reflected to the direction perpendicular to the original transmission direction by the terahertz beam splitter and is received by the terahertz frequency mixer;
the two-dimensional scanning device controls the collimated and parallel terahertz wave signals to scan the surface of the solid rocket engine to be detected in the x and y directions in a two-dimensional scanning mode;
the data acquisition device is used for receiving the intermediate frequency signal output by the terahertz frequency mixer and converting the intermediate frequency signal into a digital signal;
the imaging processing device is used for receiving the digital signals, obtaining a one-dimensional imaging array corresponding to each scanning position of the two-dimensional scanning device through processing, controlling the terahertz wave signals parallel to the collimation in a two-dimensional scanning mode to scan the surface of the solid rocket engine to be detected in the x and y directions to obtain a three-dimensional imaging data array formed by a plurality of one-dimensional imaging arrays, and outputting an x-y direction interference imaging graph corresponding to the surface of the solid rocket engine to be detected according to the three-dimensional imaging data array; if the interference imaging image in the x-y direction has fringe distribution, the interface between the shell of the solid rocket engine to be tested and the fuel column has debonding gap defect, and if the interference imaging image in the x-y direction has no fringe distribution, the debonding gap defect does not exist.
3. The terahertz imaging solid rocket engine interface debonding defect detection system according to claim 2, wherein the data acquisition device comprises a first data acquisition end and a second data acquisition end, the first data acquisition end is connected with a signal output end of the terahertz frequency mixer, a signal output end of the data acquisition device is connected with a signal input end of the imaging processing device, and the data acquisition device is used for acquiring an intermediate frequency signal obtained by frequency mixing of the terahertz frequency mixer and transmitting the intermediate frequency signal to the imaging processing device; and the second data acquisition end is connected with the synchronous output end of the terahertz wave transmitter.
4. The terahertz imaging solid rocket engine interface debonding defect detection system of claim 3, wherein the terahertz wave collimating device comprises a first parabolic mirror and a second parabolic mirror; the first parabolic mirror and the second parabolic mirror are arranged between the terahertz wave transmitter and the solid rocket engine to be tested in parallel; the terahertz beam splitter is arranged between the first parabolic mirror and the second parabolic mirror; the terahertz wave signal emitted by the terahertz wave emitter is collimated into parallel light by the first parabolic mirror and is converged to the surface of the solid rocket engine to be tested through the second parabolic mirror, and the terahertz wave signal is reflected on the surface of the solid rocket engine to be tested, passes through the second parabolic mirror, is reflected to the direction perpendicular to the original transmission direction through the terahertz beam splitter, and is received by the terahertz frequency mixer.
5. The terahertz imaging solid rocket engine interface debonding defect detection system of claim 2, wherein the terahertz wave emitter emits the terahertz wave signal at a frequency f with a transmission period T1Change to f2Time of tsWherein t iss< T; the dwell time of the two-dimensional scanning device at each scanning position is NT, wherein N is an integer greater than or equal to 1; and the two-dimensional scanning device defines a plane parallel to the surface of the solid rocket engine to be detected as an x-y plane formed by the directions of x and y.
6. The terahertz imaging solid rocket engine interface debonding defect detection system according to claim 2, wherein the x and y direction scanning precision of the two-dimensional scanning device is 0.1-20 mm; t is 10-500 microseconds; n is 1-1024; ts = 0.8T.
7. Use of the terahertz imaging solid rocket engine interface debonding defect detection system according to any one of claims 2-6 in debonding defect detection between a housing and a fuel column of a solid rocket engine.
8. The use of claim 7, wherein the housing of the solid-rocket engine is a housing having a multi-layer interface structure formed of fiberglass, ceramic, resin, inorganic compound or rubber material by a lamination, winding or molding process.
9. The use of claim 8, wherein the housing of the solid-rocket motor is a structural housing having a planar layer interface, a cylindrical layer interface, or a random-shaped layer interface.
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| CN114151237B (en) * | 2021-11-26 | 2022-11-18 | 武汉大学 | Intelligent detection system for debonding of solid rocket engine III interface and application method |
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