CN116678917A - Rapid prediction method and system for detonation velocity of laser loaded energetic material - Google Patents
Rapid prediction method and system for detonation velocity of laser loaded energetic material Download PDFInfo
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Abstract
The invention discloses a method and a system for rapidly predicting detonation velocity of a laser loaded energetic material, and belongs to the field of detonation performance detection of energetic materials. The method uses the interaction of pulse laser and energetic materials to generate shock waves, and uses an APD detector of a single point to record and store the voltage change of the APD so as to obtain attenuation signals when the shock waves pass through detection beams, and extracts the interval time between the pulse signals and each attenuation peak at different heights from the surface of the energetic materials; and obtaining the corresponding shock wave characteristic velocity through the corrected point explosion model fitting time-position relationship, and establishing a linear regression relationship with the macroscopic explosion velocity to realize the rapid prediction of the explosion velocity of the energetic material. According to the invention, only 5-10mg of sample is needed, and the extraction of the shock wave velocity of the energetic material is realized through a single-point detector, so that the characteristic velocity of the shock wave is obtained; and linearly fitting the shock wave velocity and the known detonation velocity to predict the detonation velocity of the energetic material. The invention can improve the research and development efficiency of the energetic material and reduce the research and development cost.
Description
Technical Field
The invention relates to a method and a system for extracting the shock wave velocity and predicting the detonation velocity of an energetic material, belonging to the field of detection of detonation performance of the energetic material.
Background
The energetic material is used as the most important power and damage energy source in a weapon system, releases a large amount of energy through self oxidation-reduction reaction, and is widely used in the fields of blasting industry, pyrotechnic agents, weapon equipment, rocket propulsion and the like. The detonation performance and the safety performance are two most important performances of the energetic material, and directly determine the damage capability and the reliability of the energetic material.
Detonation performance is typically measured by "five explosion" parameters, such as detonation velocity, detonation pressure, detonation heat, detonation capacity, detonation temperature, and thermodynamic parameters, such as formation enthalpy. The explosion velocity has very important significance for energetic material explosion velocity prediction, and especially the explosion velocity prediction of novel energetic materials has important significance for explosive formulation optimization and safe and reasonable production. The current method is mainly used for measuring the detonation velocity by consuming about hundred grams of explosive quantity and kilogram of explosive quantity on the basis of national army standards, but has the defects of poor reproducibility, high risk and the like due to the problems of explosive density and the like.
In recent years, a method for accurately and efficiently predicting the detonation velocity of an energetic material by extracting an image of laser-induced shock waves by using a schlieren method and then extracting the characteristic wave velocity of the shock waves by using the image of schlieren has appeared. However, in the schlieren method, in order to improve the resolution in time, it is necessary to take a photograph of the schlieren by means of a high-speed camera. And the high-speed camera is high in price, and the high-speed camera with 20 ten thousand frames of resolution is sold at a price as high as 80 ten thousand. Meanwhile, the core technology is limited by foreign countries, and cannot meet domestic autonomous production. This places a great limit on the application of the schlieren method.
Disclosure of Invention
The invention aims to solve the problems that the conventional energetic material explosion velocity is difficult to measure and has high risk, a high-speed camera in an image for extracting laser induced shock waves by using a schlieren method is high in price, and a high-speed camera with high time resolution cannot be independently researched and developed in China.
The aim of the invention is achieved by the following technical scheme.
The invention discloses a laser loading energetic material explosion velocity rapid prediction method, which comprises the following steps:
step one: a shock wave is generated.
And the nanosecond pulse laser is used for adjusting the excitation energy to be more than 110mJ, the excitation energy is focused to a preset position below the surface of the sample through the lens, and the laser is loaded on the energetic material sample to generate shock waves, so that the uncertainty caused by the breakdown of the high-energy pulse laser to air is avoided.
Preferably, a nanosecond pulse laser with a wavelength of 1064nm and a pulse width of 9ns is used, the excitation energy is adjusted to 110mJ, the laser is focused to a position 3mm below the surface of the energetic material sample through a lens with a focal length of f=150 mm, and the laser loads the energetic material sample to generate a shock wave, so that uncertainty caused by air breakdown of the high-energy pulse laser is avoided.
Step two: the shock wave is detected.
The laser is used as a detection light source. Silicon-based avalanche photodiodes are used as detectors. The direct enamelled copper wires are respectively connected to the anode and cathode bonding pads of the detector, then the welded module is placed on the PCB and fixed by ultraviolet curing glue, and the position of the detector is finely adjusted by the enamelled copper wires after the fixing is finished, so that the detection light beam is accurately beaten on the photosensitive surface of the detector, and the best initial signal response is ensured to be obtained.
When the probe laser passes through the shockwave region, the shockwave density distribution is not uniform. When the detected light passes through the disturbance area of the shock wave, the high density of the shock wave front edge refractsLaw n 1 sin(θ 1 )＝n 2 sin(θ 2 ) It is determined that the light beam after passing through the shockwave disturbance region will be deflected downward with respect to the initial propagation direction. The deflected light spot gradually deviates from the center of the detection surface of the detector due to the photocurrent generated by the photoelectric detectorDepending on the incident light power P, while the incident light power p=a·i depends on the irradiation area a. Therefore, when the detection beam is deflected by the impact wave front edge, the area of the light spot on the light sensitive surface of the detector is reduced, and an attenuation peak is generated on the basis of the original signal.
Meanwhile, the bremsstrahlung luminescence of the high-brightness plasma plume exists in the initial stage of plasma generation, the radiation luminescence is characterized by wide spectrum, and the luminescence range is 400-1100nm. And the light is in the corresponding range of the detector, so that the detection signal is obviously influenced, and a stronger noise signal is often observed on the detector. In order to reduce the effect of the plasma radiation. A band-pass filter with a center wavelength of 635+/-20 nm is selected, the high-transmittance range of the band-pass filter just covers 632.8nm detection light used in an experiment, the band-pass filter is placed in front of a detector in a position of 2.5 cm-3 cm in parallel, the influence caused by bremsstrahlung emission and excitation light scattering of plasma plumes is removed, and the signal-to-noise ratio of signals is remarkably improved.
Preferably, the output power of the He-Ne laser as the probe light source is 1mW and the wavelength is 632.8nm.
The silicon-based avalanche photodiode as a detector has a photosurface of 200 μm, a cut-off frequency of 2GHz, a detection wavelength of 400-1100nm, and a gain of 100.
An enameled copper wire with the diameter of 0.4mm is connected to the anode and cathode bonding pads of the detector respectively.
The band-pass filter is arranged in front of the detector in parallel at a position of 2.5 cm-3 cm.
Step three: and (5) current-voltage conversion.
The analog module comprises an APD power module and an APD current-voltage conversion module. Detection methodOne end of a copper wire led out of the tester is connected to the power module, and the other end of the copper wire is connected to the current-voltage conversion module. The output voltage of the main chip of the APD power module is determined by the voltage on the feedback pin FB, and the calculation formula is as follows:resistor R 1 ，R 22 Potentiometer R 4 Substituting the above formula to obtain: /> By means of a pair of potentiometers R 4 And adjusting to obtain the required voltage.
Since APDs are high-speed semiconductor photodetectors with internal gain, only photons can be converted to electrons and an amplified photocurrent signal is generated. Therefore, a current-voltage conversion module is added behind the power supply module and is passed through a filter circuit, and the multiplied photo-generated current signal of the APD is converted into a voltage signal and is filtered. The electric signal is output from the P2 pin (anode) of the APD, enters the reverse input end of the operational amplifier to form a negative feedback amplifying circuit, and outputs the voltage output to a subsequent data acquisition module for acquisition and recording after passing through a capacitor.
Preferably, the APD power module uses TPS5534 (TSSOP package) as the main chip.
The operational amplifier is an operational amplifier OPA657U.
And the negative feedback amplifying circuit outputs the voltage to a subsequent data acquisition module after passing through a 0.1 mu F capacitor.
Step four: and (5) data acquisition.
After the detection beam is 2mm away from the surface of the sample and the measurement is completed, the heights of the laser focusing lens and the sample table are adjusted simultaneously, so that the laser focusing lens and the sample table are synchronously lowered. Each measurement is carried out by presetting a step length, so that the detection distance variation range is 2-10 mm. Meanwhile, when the height is reduced each time, the X axis and the Y axis of the sample stage are required to be adjusted, so that excitation laser is beaten on a new sample surface each time, and the influence caused by brand new chemical substances generated by multiple ablations on the sample surface is avoided.
Preferably, each measurement step is 0.5mm.
Step five: and (5) data processing.
Firstly, denoising and smoothing processing is carried out on the signal by utilizing SVD filtering. SVD noise reduction algorithm implementation: (1) The acquired signal data is represented by A (k), wherein A (k) represents the signal data detected when the height of the detection light and the surface of the sample is k; decomposing the signal A (k) into an m n matrix, i.e. A (k) →A m×n (k) A. The invention relates to a method for producing a fibre-reinforced plastic composite Wherein m and n are the number of rows and columns respectively, and the product of m and n is equal to the total number of data. (2) Will signal A m×n (k) Decomposition into products of three matrices, i.e. A m×n (k)＝U m×n ·∑ m×n ·V m×n . Wherein U is m×m unitary matrix, V is n×n unitary matrix, sigma is m×n matrix, elements other than main diagonal are all 0, and the values are arranged in order from large to small, i.e. sigma 1 >σ 2 >σ 3 >.... (3) Dividing sigma by maximum sigma 1 All values except for all values return to 0 to obtain sigma 1; multiplying the obtained sigma 1 with U and V to obtain a noise-reduced signal A1 m×n (k) A. The invention relates to a method for producing a fibre-reinforced plastic composite (4) Calculation of sigma 1 Percentage of all sigma, i.eJudging whether the condition is satisfied: f (f)>A threshold is preset, and if the threshold is met, the denoising part is finished; if the condition is not satisfied, the noise-reduced signal A1 is used for m×n (k) And (3) repeating the steps (1), (2) and (3) as new initial signals until the preset noise reduction condition is met.
And secondly, intercepting the attenuation signal range. Finding the position of the minimum value in the whole signal range, and obtaining the position of the minimum value of an attenuation signal by X min And (5) respectively intercepting pixel points from front to back of the center.
After the corresponding part of the attenuation signal is intercepted, the curve of the attenuation signal measured each time is fitted. X is to be min Presetting to 0 point, and performing simulation by using Gaussian linearityAnd (3) combining, wherein a fitting formula is as follows:wherein the fitting parameter is a 1 And b 1 . After the first fitting is finished, solving the regression coefficient R 2 And judge R 2 >Whether the preset value is true. If true, fitting to the end; if not, then a second fitting is performed, i.e. +.>The previous determination is then continued until the ith time, R 2 >The preset value is established, so that the final fitting result is as follows:
after the fitted attenuation signal is obtained, the arrival time of the shock wave is judged. The time zero of the signal is defined when the pump laser pulse arrives. The moment when the signal decay is minimal is the time of arrival of the shock wave. Thus fitting the result ofConduct derivative and find +.>The position of (2) is denoted as x min . The position is then restored to obtain the time of arrival of the shock wave in the original signal as t= (X) min +x min -1500) 0.001us. And repeating the steps to realize the complete processing of the signal data with different heights from the surface of the sample, and finally obtaining a plurality of groups of time and distance data.
After the time and distance data are obtained, a formula is used to fit the relationship between the two. In the early stage of plasma evolution, the pressure of the impact front is far greater than the pressure of the ambient gas, namely the ambient gas pressure is ignored. The early stage of laser induced shock wave propagation is described by the Sedov-Taylor principle. The relationship between the distance R of the shock front along to the center of the explosion and the propagation time t is expressed as:where A and q are parameters of the desired fit. In the later stage of plasma evolution, the high-temperature high-pressure plasma nuclei gradually collapse, and the pressure of the ambient gas cannot be ignored. The shock wave is subjected to resistance from the ambient gas during the outward propagation, so that the shock wave is rapidly attenuated to the sound velocity. The later stages of laser induced shock wave propagation are described by Drag model principles. The relationship between the distance R of the shock front along to the center of the explosion and the propagation time t can be expressed as: r=r 0 (1-e -βt ) Wherein R is 0 And β is the parameter of the desired fit. Since the measured range (in time and distance scale) spans the front and back periods of shock wave propagation, the point explosion model was improved: r=at q +vt. Wherein v=r 0 Beta. The improved point explosion model simultaneously gives consideration to the front and rear periods of the shock wave propagation, and improves the fitting precision of the shock wave propagation. After the corresponding R-t fitting curve is obtained, deriving the R-t fitting curve to obtain a v-t curve. And obtaining the relation of the time evolution of the shock wave velocity.
Preferably, X is min Respectively intercepting 1500 pixel points, namely X, from front to back of the center min ±1500。
Step six: and predicting the detonation velocity of the energetic material through the established model.
After the v-t curve is obtained, the characteristic speed of the shock wave is intercepted, and a linear regression relation between the characteristic speeds of different energetic materials and macroscopic explosion speeds is established through a PLS method, so that the detonation speed prediction of the energetic materials is realized.
The invention also discloses a laser loading energetic material explosion velocity rapid prediction system which is used for realizing the laser loading energetic material explosion velocity rapid prediction method. The laser loading energetic material explosion speed rapid prediction device comprises a nanosecond pulse laser, a reflector, a 150mm focusing lens, a one-dimensional displacement table, a three-dimensional automatic adjustment sample table, a He-Ne laser, an optical filter, an avalanche photodiode APD, an analog circuit module and a data acquisition module.
The nanosecond pulse laser is used for inducing the energetic material to generate laser shock waves.
The three-dimensional displacement table is used for adjusting the height and the position of the sample.
The one-dimensional displacement table is used for adjusting the height of the focusing lens above the sample and guaranteeing that the focus of laser is positioned at the position of 3mm inside the sample. While after focusing the inside of the sample, it is used to move synchronously with the three-dimensional displacement stage to change the distance between the probe light and the sample surface.
The He-Ne laser is used for generating a detection laser source.
The avalanche photodiode is used for receiving signals of detection light.
The optical filter is arranged in front of the avalanche photodiode and is used for filtering stray light and improving the flatness of a received signal of the detector.
The analog circuit module is connected to the APD and is used for providing bias voltage for the APD and converting a current signal into a voltage signal.
The data acquisition module is connected behind the analog circuit module and is used for acquiring and recording the output voltage of the analog circuit.
The beneficial effects are that:
1. the invention discloses a method and a system for rapidly predicting the detonation velocity of a laser loaded energetic material, which realize sampling 4 points within 10 mu s by stepping a sample stage by 0.5mm once, which is equivalent to completing the task of a 40 ten thousand-frame high-speed camera. And the selling price of a 20 ten thousand-frame high-speed camera is up to 80 ten thousand yuan, the comprehensive cost of the device is about 8 ten thousand, and compared with the high-speed camera which is required to be used by a schlieren method, the device can save 90 percent of cost.
2. The invention discloses a method and a system for rapidly predicting the detonation velocity of a laser loaded energetic material, wherein the initial distance between a detection beam and the surface of a sample stage is set to be 2mm, so that the lowest detection time point is 1.8us, and the shortest shooting time of a 20-ten-thousand-frame high-speed camera is 5us. The performance is improved by about 60% compared to the high speed camera that the schlieren method needs to use.
3. The invention discloses a rapid prediction method and a rapid prediction system for the detonation velocity of a laser loaded energetic material, which utilize the laser induced energetic material to generate shock waves, can measure the shock wave velocity of the laser induced energetic material under the condition of only consuming 5-10mg at a time, and provide a novel simple, feasible, safe and reliable method for the detonation velocity prediction of the energetic material through modeling of the shock wave velocity and the known detonation velocity.
Drawings
FIG. 1 is a schematic diagram of a laser induced energetic material shock wave detonation velocity extraction system.
Fig. 2 is a graph of the acquired shock wave attenuation peaks.
Figure 3 is a graph of the velocity extraction results of the shock wave features for four energetic materials.
1-nanosecond pulse laser, 2-reflecting mirror, 3-150 mm focusing lens, 4-He-Ne laser, 5-one-dimensional displacement table, 6-three-dimensional automatic adjustment sample table, 7-optical filter, 8-Avalanche Photodiode (APD), 9-analog circuit module and 10-data acquisition module.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings.
As shown in fig. 1, the embodiment discloses a rapid prediction system for the detonation velocity of a laser loaded energetic material, which comprises a nanosecond pulse laser 1, a reflecting mirror 2, a 150mm focusing lens 3, a He-Ne laser 4, a one-dimensional displacement table 5, a three-dimensional automatic adjustment sample table 6, a filter 7, an avalanche photodiode 8, a data simulation module 9 and a data acquisition module 10.
After being reflected by the reflecting mirror 2, a beam of nanosecond pulse laser emitted by the nanosecond pulse laser 1 is parallelly incident to the 150mm focusing lens 3 and then converged on the three-dimensional automatic adjusting sample stage 6. The 150mm focusing lens 3 is fixed on a one-dimensional displacement table 5 with one-dimensional adjustable. The He-Ne laser 4 emits a beam of probe light, which passes through the filter 7 and irradiates the avalanche photodiode 8. The filter 7 is placed in parallel 3cm in front of the avalanche photodiode 8. The avalanche photodiode 8 is connected to an analog block 9 and subsequently to a digital acquisition block 10.
The nanosecond pulse laser has the laser wavelength of 1064nm, the pulse width of 9ns and the single pulse laser energy of 10-120mJ@1064nm which is adjustable.
The reflecting lens is used for changing the path of the pulse laser and enabling the laser to vertically act on the sample.
And the focusing lens is used for focusing the laser emitted by the pulse laser on the sample, so that the sample is induced to generate shock waves.
The detection laser comprises a continuous laser with the wavelength of 632.8nm and a laser light source for generating detection light.
The filter is a 635nm narrow-band pass filter and is used for filtering stray light, improving the quality of signals and shielding most of plasma light.
The avalanche photodiode is a silicon-based APD diode, and the detector is fixed on the support rod in a combined welding and ultraviolet glue curing mode.
The analog block shown provides a reverse bias voltage for an APD and converts the APD current signal to a voltage signal for an integrated circuit board.
The data acquisition equipment is a four-channel oscilloscope with the bandwidth of 350MHz and is used for recording and storing the voltage value transmitted back by the analog module.
The three-dimensional displacement table is used for placing the sample and realizing horizontal displacement of the sample and adjusting the height of the sample.
The one-dimensional displacement table is used for adjusting the height of the focusing lens above the sample and guaranteeing that the focus of laser is positioned at the position of 3mm inside the sample. While after focusing the inside of the sample, it is used to move synchronously with the three-dimensional displacement stage to change the distance between the probe light and the sample surface.
The embodiment discloses a laser loading energetic material explosion velocity rapid prediction method, which comprises the following specific implementation steps:
the first step: the He-Ne laser is started to enable the detection beam to be 2mm away from the surface of the sample, and the detection beam irradiates the surface of the detector after passing through the filter plate.
And a second step of: the excitation energy was adjusted to above 110mJ using a nanosecond pulsed laser with a wavelength of 1064nm and a pulse width of 9ns, focused 3mm below the sample surface by a lens with a focal length f=150 mm. The attenuation signal is collected once.
And a third step of: the heights of the one-dimensional displacement table and the three-dimensional displacement table are synchronously reduced by 0.5mm.
Fourth step: the X-axis and Y-axis of the three-dimensional displacement table are adjusted to ensure that each laser ablation is a new sample.
Fourth step: after signals within the range of 2-10 mm are obtained, noise reduction and smoothing processing are carried out on the signals by utilizing an SVD method.
Fifth step: and (3) intercepting the attenuation signal range from the denoised data, and respectively fitting attenuation signal curves measured each time after intercepting corresponding parts of the attenuation signals. And then judging the arrival time of the shock wave, and extracting the arrival time of the shock wave.
Sixth step: after the time and distance data are obtained, the relationship between the two is fitted. And obtaining the relation between time and speed through derivation, and meanwhile, intercepting the speed at 0.8us as the characteristic speed of the shock wave.
Seventh step: and establishing linear regression relations between different energetic material characteristic speeds and macroscopic explosion speeds through a PLS method, and predicting the macroscopic explosion speeds.
From this, the extraction of laser induced energetic material shock wave and the prediction of detonation velocity are realized. Compared with a method for measuring the detonation velocity by using the national army standard to consume about hundred grams and kilogram of medicine quantity at a time, the method can measure the detonation velocity by using only milligram of medicine quantity. The detonation parameters of the four energetic materials are predicted, and compared with the schlieren method which consumes milligrams of medicine, the predicted speed error of the method is about 15 m/s-85 m/s. While the error predicted by the schlieren method using the high-speed camera is about 80m/s to 120m/s, the method reduces the error by 30% to 60% compared with the method.
Comparison table of detonation parameter prediction results and reports of four energetic materials
In the embodiment, a pulse laser is firstly used for generating a shock wave through interaction with an energetic material, then a single-point APD detector is used for recording and storing voltage changes of the APD to obtain an attenuation signal when the shock wave passes through a detection light beam, and then an algorithm is used for extracting the interval time between the pulse signal and each attenuation peak at different heights from the surface of the energetic material. And then fitting the time-position relation through the corrected point explosion model to obtain the corresponding shock wave characteristic speed and establishing a linear regression relation with the macroscopic explosion speed so as to realize the rapid prediction of the explosion speed of the energetic material. The shock wave extraction method adopted by the implementation only consumes trace energy-containing materials, and the shock wave speed of the energy-containing materials is extracted through a single-point detector, so that the characteristic speed of the shock wave is obtained. And finally, performing linear fitting on the shock wave speed and the known detonation velocity, and then estimating the detonation velocity of the energetic material. In the embodiment, only 5-10mg of samples are needed, so that the research and development period of the energetic material is greatly shortened, the research efficiency of the energetic material is improved, and the research and development cost of the energetic material is reduced.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (7)
1. A method and a system for rapidly predicting the detonation velocity of a laser loaded energetic material are characterized in that: comprises the following steps of the method,
step one: generating a shock wave;
adjusting excitation energy to be more than 110mJ by using a nanosecond pulse laser, focusing to a preset position below the surface of a sample by using a lens, and loading an energetic material sample by laser to generate shock waves so as to avoid uncertainty caused by high-energy pulse laser breakdown air;
step two: detecting a shock wave;
He-Ne laser is used as a detection light source; silicon-based avalanche photodiodes are used as detectors; the method comprises the steps of respectively connecting a direct enamelled copper wire to an anode bonding pad and a cathode bonding pad of a detector, then placing a welded module on a PCB (printed circuit board) and fixing the module by ultraviolet curing glue, and finely adjusting the position of the detector by the enamelled copper wire after the fixing is finished so as to ensure that a detection light beam is accurately beaten on a light sensitive surface of the detector and ensure that the optimal initial signal response is obtained;
when the detection laser passes through the shock wave region, the shock wave density distribution is not uniform; when the detected light passes through the disturbance area of the shock wave, the refraction law n is due to the higher density of the shock wave front edge 1 sin(θ 1 )＝n 2 sin(θ 2 ) After the light passes through the impact wave disturbance area, the emergent position of the light is downwards deflected relative to the initial propagation direction; the deflected light spot gradually deviates from the center of the detection surface of the detector due to the photocurrent generated by the photoelectric detectorDepending on the incident light power P, while the incident light power p=a·i depends on the irradiation area a; therefore, when the detection beam is deflected by the impact wave front edge, the area of the light spot on the light sensitive surface of the detector is reduced, and an attenuation peak is generated on the basis of the original signal;
in order to reduce the effect of the plasma radiation; selecting a band-pass filter with a center wavelength of 635+/-20 nm, and placing the band-pass filter in front of the detector in parallel at a position of 2.5 cm-3 cm;
step three: current-voltage conversion;
the analog module comprises an APD power supply module and an APD current-voltage conversion module; one end of a copper wire led out from the detector is connected to the power module, and the other end of the copper wire is connected to the current-voltage conversion module; the output voltage of the main chip of the APD power module is determined by the voltage on the feedback pin FB, and the calculation formula is as follows:resistor R 1 ，R 22 Potentiometer R 4 Substituting the above formula to obtain:
by means of a pair of potentiometers R 4 Adjusting to obtain the required voltage;
because APD is a high-speed semiconductor photodetector with internal gain, it can only convert photons into electrons and produce an amplified photocurrent signal; therefore, a current-voltage conversion module is added behind the power module and passes through a filter circuit, and the multiplied photo-generated current signal of the APD is converted into a voltage signal and is filtered; the electric signal is output from the P2 pin of the APD, enters the reverse input end of the operational amplifier to form a negative feedback amplifying circuit, and outputs the voltage output to a subsequent data acquisition module for acquisition and recording after passing through a capacitor;
step four: collecting data;
after the detection beam is 2mm away from the surface of the sample and measurement is completed, the heights of the laser focusing lens and the sample table are adjusted simultaneously, so that the laser focusing lens and the sample table are synchronously lowered; each measurement is carried out by presetting a step length, so that the detection distance variation range is 2-10 mm; meanwhile, when the height is reduced each time, the X axis and the Y axis of the sample stage are required to be adjusted, so that excitation laser is beaten on a new sample surface each time, and the influence caused by brand new chemical substances generated by multiple ablations on the sample surface is avoided;
step five: data processing;
denoising and smoothing the signal by utilizing SVD filtering; SVD noise reduction algorithm implementation: (1) The acquired signal data is represented by A (k), wherein A (k) represents the signal data detected when the height of the detection light and the surface of the sample is k; decomposing the signal A (k) into an m n matrix, i.e. A (k) →A m×n (k) The method comprises the steps of carrying out a first treatment on the surface of the Wherein m and n are the number of rows and columns respectively, and the product of m and n is equal to the total number of data; (2) Will signal A m×n (k) Decomposition into products of three matrices, i.e. A m×n (k)＝U m×n ·∑ m×n ·V m×n The method comprises the steps of carrying out a first treatment on the surface of the Wherein U is m×m unitary matrix, V is n×n unitary matrix, sigma is m×n matrix, elements other than main diagonal are all 0, and the values are arranged in order from large to small, i.e. sigma 1 >σ 2 >σ 3 >..; (3) Dividing sigma by maximum sigma 1 All values except for all values return to 0 to obtain sigma 1; multiplying the resulting sigma 1 with U and V,obtaining a noise-reduced signal A1 m×n (k) The method comprises the steps of carrying out a first treatment on the surface of the (4) Calculation of sigma 1 Percentage of all sigma, i.eJudging whether the condition is satisfied: f (f)>A threshold is preset, and if the threshold is met, the denoising part is finished; if the condition is not satisfied, the noise-reduced signal A1 is used for m×n (k) Repeating the steps (1), (2) and (3) until the preset noise reduction condition is met as a new initial signal;
secondly, intercepting the attenuation signal range; finding the position of the minimum value in the whole signal range, and obtaining the position of the minimum value of an attenuation signal by X min Intercepting pixel points respectively from front to back of the center;
after the corresponding part of the attenuation signal is intercepted, fitting the attenuation signal curve measured each time respectively; x is to be min Presetting to be 0 point, fitting by using Gaussian linearity, wherein a fitting formula is as follows:wherein the fitting parameter is a 1 And b 1 The method comprises the steps of carrying out a first treatment on the surface of the After the first fitting is finished, solving the regression coefficient R 2 And judge R 2 >Whether the preset value is true; if true, fitting to the end; if not, then a second fitting is performed, i.e. +.>The previous determination is then continued until the ith time, R 2 >The preset value is established, so that the final fitting result is as follows:
after obtaining the fitted attenuation signal, judging the arrival time of the shock wave; defining a time zero of the signal when the pump laser pulse arrives; the moment when the signal attenuation is minimum is the arrival time of the shock wave; thus fitting the result ofConduct derivative and find +.>The position of (2) is denoted as x min The method comprises the steps of carrying out a first treatment on the surface of the The position is then restored to obtain the time of arrival of the shock wave in the original signal as t= (X) min +x min -1500) 0.001us; repeating the steps to realize the complete processing of the signal data with different heights from the surface of the sample, and finally obtaining a plurality of groups of time and distance data;
after obtaining the data of time and distance, fitting the relation between the time and the distance by using a formula; in the early stage of plasma evolution, the pressure of the impact front is far greater than the pressure of the ambient gas, namely the ambient gas pressure is ignored; the early stage of laser induced shock wave propagation is described by the Sedov-Taylor principle; the relationship between the distance R of the shock front along to the center of the explosion and the propagation time t is expressed as:wherein A and q are parameters of the desired fit; in the later stage of plasma evolution, the high-temperature high-pressure plasma core gradually collapses, and the pressure of the ambient gas cannot be ignored at the moment; the shock wave is subjected to resistance from ambient gas in the process of outwards propagation, so that the shock wave is rapidly attenuated to sound velocity; the later propagation period of the laser induced shock wave is described by using a Drag model principle; the relationship between the distance R of the shock front along to the center of the explosion and the propagation time t can be expressed as: r=r 0 (1-e -βt ) Wherein R is 0 And β is the parameter of the desired fit; since the measured range (in time and distance scale) spans the front and back periods of shock wave propagation, the point explosion model was improved: r=at q +vt; wherein v=r 0 Beta; the improved point explosion model simultaneously gives consideration to the front and rear periods of the shock wave propagation, and improves the fitting precision of the shock wave propagation; after obtaining a corresponding R-t fitting curve, deriving the R-t fitting curve to obtain a v-t curve; namely, obtaining the relation of the time evolution of the shock wave velocity;
step six: the detonation velocity of the energetic material is predicted through the established model;
after the v-t curve is obtained, the characteristic speed of the shock wave is intercepted, and a linear regression relation between the characteristic speeds of different energetic materials and macroscopic explosion speeds is established through a PLS method, so that the detonation speed prediction of the energetic materials is realized.
2. The method for rapidly predicting the detonation velocity of a laser loaded energetic material according to claim 1, wherein the method comprises the following steps: the nanosecond pulse laser with the wavelength of 1064nm and the pulse width of 9ns is used for adjusting the excitation energy to 110mJ, the excitation energy is focused to a position 3mm below the surface of the energetic material sample through a lens with the focal length f=150mm, and the laser loads the energetic material sample to generate shock waves, so that the uncertainty caused by the breakdown of the high-energy pulse laser by air is avoided.
3. The method for rapidly predicting the detonation velocity of a laser loaded energetic material according to claim 1, wherein the method comprises the following steps: as a light source of the probe light, the He-Ne laser was 1mW in output power and 632.8nm in wavelength.
The silicon-based avalanche photodiode used as a detector has a photosurface of 200 mu m, a cut-off frequency of 2GHz, a detection wavelength of 400-1100nm and a gain of 100;
an enamelled copper wire with the diameter of 0.4mm is respectively connected to an anode pad and a cathode pad of the detector;
the band-pass filter is arranged in front of the detector in parallel at a position of 2 cm-3 cm.
4. The method for rapidly predicting the detonation velocity of a laser loaded energetic material according to claim 1, wherein the method comprises the following steps: the main chip used by the APD power module is TPS5534;
the operational amplifier is an operational amplifier OPA657U;
and the negative feedback amplifying circuit outputs the voltage to a subsequent data acquisition module after passing through a 0.1 mu F capacitor.
5. The method for rapidly predicting the detonation velocity of a laser loaded energetic material according to claim 1, wherein the method comprises the following steps: each measurement step was 0.5mm.
6. The method for rapidly predicting the detonation velocity of a laser loaded energetic material according to claim 1 or 2, wherein the method comprises the following steps: by X min Respectively intercepting 1500 pixel points, namely X, from front to back of the center min ±1500。
7. The laser loading energetic material explosion velocity rapid prediction system is used for realizing the laser loading energetic material explosion velocity rapid prediction method according to claim 1, 2, 3, 4, 5 or 6, and is characterized in that: the device comprises a nanosecond pulse laser, a reflector, a 150mm focusing lens, a one-dimensional displacement table, a three-dimensional automatic adjustment sample table, a He-Ne laser, an optical filter, an Avalanche Photodiode (APD), an analog circuit module and a data acquisition module;
the nanosecond pulse laser is used for inducing the energetic material to generate laser shock waves;
the three-dimensional displacement table is used for adjusting the height and the position of the sample;
the one-dimensional displacement table is used for adjusting the height of the focusing lens above the sample and ensuring that the focal point of the laser is positioned at a position of 3mm inside the sample; simultaneously after focusing the inside of the sample, it is used to move synchronously with the three-dimensional displacement table to change the distance between the probe light and the sample surface;
the He-Ne laser is used for generating a detection laser source;
the avalanche photodiode is used for receiving signals of detection light;
the optical filter is arranged in front of the avalanche photodiode and is used for filtering stray light and improving the flatness of a received signal of the detector;
the analog circuit module is connected to the APD and used for providing bias voltage for the APD and converting a current signal into a voltage signal;
the data acquisition module is connected behind the analog circuit module and is used for acquiring and recording the output voltage of the analog circuit.
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