Laser-induced energetic material shock wave extraction system and method

Abstract

The laser-induced energetic material shock wave extraction system and method disclosed by the application belong to the field of energetic material detonation performance detection.The application comprises a nanosecond pulse laser, a mirror, a 150mm focusing lens, a two-dimensional displacement table, a three-dimensional automatic adjusting sample table, a detection laser, a cylindrical lens, a mask, a filter, an arrayed photoelectric detector, an analog circuit module and a data acquisition module.The application utilizes laser to induce energetic materials to generate shock waves, and realizes the extraction of the shock waves of the energetic materials through the arrayed detection laser and the detector, so as to obtain the characteristic velocity of the shock waves, perform linear regression analysis on the shock wave velocity and the known detonation velocity, realize the prediction of the detonation velocity of the energetic materials, and improve the prediction accuracy of the detonation velocity.The application can measure the shock wave velocity of the laser-induced energetic materials in the case that only 5-10mg is consumed at a time, and has the advantages of high resolution, high safety, low cost and simple and easy-to-implement testing method.

Description

Technical Field

[0001] This invention relates to a method for extracting shock waves from energetic materials and a system for predicting detonation velocity, belonging to the field of detonation performance testing of energetic materials. Background Technology

[0002] Energetic materials, as the most important power and destructive energy source in weapon systems, release a large amount of energy through their own redox reactions and are widely used in blasting industries, pyrotechnics, weaponry, and rocket propulsion. Detonation performance and safety performance are the two most important properties of energetic materials, directly determining their destructive capability and reliability.

[0003] Detonation performance is typically measured by five parameters: detonation velocity, detonation pressure, detonation heat, detonation volume, and detonation temperature, as well as thermodynamic parameters such as the enthalpy of formation. Detonation velocity is particularly important for energetic materials; therefore, predicting the detonation velocity of energetic materials, especially novel energetic materials, is crucial for optimizing explosive formulations and ensuring safe and rational production. Current methods mostly predict detonation velocity based on national military standards, consuming approximately 100 grams or 1 kilogram of explosive. However, due to issues such as charge density, this method suffers from poor repeatability and high risk. In recent years, a method has emerged that uses schlieren to extract images of laser-induced shock waves, and then extracts the characteristic wave velocity of the shock wave from the schlieren images, thus accurately and efficiently predicting the detonation velocity of energetic materials. This method is safe, reliable, fast, and accurate. However, to improve temporal resolution, schlieren imaging requires high-speed cameras. High-speed cameras are expensive; a high-speed camera with a resolution of 200,000 frames per second costs as much as 800,000 yuan. Furthermore, the core technology is dependent on foreign sources, making domestic production impossible. Summary of the Invention

[0004] To address the challenges of determining the detonation velocity of energetic materials, the high risks involved, the high cost of high-speed cameras for extracting laser-induced shock waves using schlieren imaging, and the lack of domestically developed high-temporal-resolution high-speed cameras, this invention aims to provide a laser-induced energetic material shock wave extraction system and method. This system utilizes a two-dimensional array detector to extract the shock wave generated by laser-loaded energetic materials, and uses the extracted shock wave's characteristic velocity to predict the detonation velocity of the energetic material.

[0005] The objective of this invention is achieved through the following technical solution.

[0006] The laser-induced energetic material shock wave extraction system disclosed in this invention includes a nanosecond pulsed laser, a mirror, a 150mm focusing lens, a two-dimensional displacement stage, a three-dimensional automatically adjustable sample stage, a probe laser, a cylindrical lens, a mask, a filter, an array photodetector, an analog circuit module, and a data acquisition module.

[0007] The nanosecond pulsed laser is used to generate laser-induced shock waves by interacting with energetic materials.

[0008] The three-dimensional displacement stage is used to adjust the height and position of the sample.

[0009] The two-dimensional displacement stage is used to adjust the height of the focusing lens above the sample to ensure that the focal point of the laser is inside the sample.

[0010] There are two detection lasers, which are deployed in two directions to generate detection laser sources.

[0011] There are two cylindrical lenses, which are placed in front of the corresponding detection lasers to constrain the size of the laser spot and shape the laser spot into an ellipse.

[0012] There are two photomasks, each placed behind a corresponding cylindrical lens, used to generate an array of light sources at the photomask.

[0013] There are two filters, which are placed in front of the corresponding array photodetectors to filter out stray light and improve the flatness of the received signal of the detector.

[0014] The array photodetector is an avalanche photodiode, consisting of two sets that are welded together and cured with UV adhesive to form a single column for point-to-point reception of probe light signals.

[0015] The analog circuit module is connected to each avalanche photodiode and is used to provide bias voltage to the avalanche photodiode and convert current signals into voltage signals.

[0016] The data acquisition module is connected after the analog circuit module and is used to acquire and record the output voltage of the analog circuit.

[0017] This invention discloses a method for extracting shock waves from laser-induced energetic materials, implemented based on the laser-induced energetic material shock wave extraction system. The method includes the following steps:

[0018] Step 1: Collect data using a laser-induced energetic material shock wave extraction system.

[0019] The first detection laser is activated. After passing through the first cylindrical lens, the detection source emits an elliptical beam that is bright in the center and dark around the edges. This elliptical beam, after passing through the first cylindrical lens, perpendicularly illuminates the first photomask, creating a series of optical paths. The first photomask has M circular holes with diameters of 240-260 μm and spacings of 1.4-1.6 mm. Due to the bremsstrahlung emission of the high-brightness plasma plume in the early stages of plasma generation, this emission exhibits a broad spectrum characteristic, with an emission range of 400–1100 nm. The wavelength range of this plasma radiation light falls within the response range of the array detector, significantly affecting the detection signal, often resulting in strong noise signals observed on the array detector. To reduce the influence of this plasma radiation light on the experiment, a first filter is placed in front of the first array detector. The height of the first photomask is adjusted so that the distance between the lowest optical path channel and the sample surface is h. y The position of the first array photodetector is adjusted so that the light path emitted from the first mask is incident point-to-point onto the first array photodetector. The second detection laser is turned on. After passing through the second cylindrical lens, the detection light source emits an elliptical beam that is bright in the center and dark around the edges. This elliptical beam is perpendicularly incident on the second mask through the second cylindrical lens, creating a series of optical paths. The second mask has M circular holes with diameters of 240µm-260µm and spacings of 1.4mm-1.6mm. A second filter is placed in front of the second array detector. The height of the second mask is adjusted so that the distance between the leftmost optical path and the sample surface is h. x Adjust the position of the second array photodetector so that the light path channel emitted through the second mask is incident on the second array photodetector point-to-point;

[0020] The nanosecond pulsed laser is focused by a lens to a depth of δ mm below the sample surface to avoid the uncertainty caused by the high-energy pulsed laser breaking down the air.

[0021] Using silicon-based avalanche photodiodes as detectors, enameled copper wires are connected to the anode and cathode pads of the detectors, respectively. The soldered modules are then placed on a PCB board and fixed with UV-cured adhesive. M detectors are fixed sequentially using the above method, ensuring that the surfaces of the M detectors are in the same plane. After fixing, the positions of the detectors can be finely adjusted using the enameled copper wires to ensure that the detection beam accurately hits the photosensitive surface of the detector, obtaining the optimal initial signal response.

[0022] When the probe laser passes through the shock wave region, the shock wave density distribution is not uniform. When the probe light passes through the disturbed area of ​​the shock wave, because the density at the leading edge of the shock wave is relatively higher than that at the trailing edge, the law of refraction, n1sin(θ1)=n2sin(θ2), determines that the exit position of the light after passing through the disturbed area will be deflected downwards relative to the initial propagation direction. The deflected light spot gradually deviates from the center position of the detector's detection surface. Due to the photocurrent generated by the photodetector... The incident light power P depends on the incident light power, which in turn depends on the irradiated area A. Therefore, when the probe beam is deflected by the leading edge of the shock wave, less light is emitted from the photosensitive surface of the detector, resulting in an attenuation peak on top of the original signal.

[0023] Set the oscilloscope to trigger-ready mode and press the single-excitation button on the nanosecond pulse laser. The laser's Q-SYNC signal will trigger the data acquisition module to record and store the signals from each channel. After completing one data acquisition cycle, adjust the X and Y axes of the sample stage so that the excitation laser hits a new sample surface each time, completing Q measurements.

[0024] Preferably, the first mask has M circular holes with a diameter of 250 μm and a spacing of 1.5 mm.

[0025] The second mask has M circular holes with a diameter of 250um and a spacing of 1.5mm.

[0026] Using a silicon-based avalanche photodiode as the detector, 0.4mm diameter enameled copper wires are used to connect to the anode and cathode pads of the detector, respectively. The soldered module is then placed on a PCB board and fixed with UV-curing adhesive.

[0027] Step 2: Use the SVD algorithm to smooth and denoise the signals from each channel acquired by the data acquisition module.

[0028] Step 2. (1) Represent the signal data acquired in Step 1 as A(k), where k represents the signal data detected when the height between the optical path channel and the sample surface is k; decompose the signal A(k) into an m×n matrix, i.e., A(k)→A m×n (k); where 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;

[0029] Step 2.(2) Transfer signal A m×n (k) can be decomposed into the product of three matrices, i.e., A m×n (k)=U m×n ·∑ m×n ·V m×n; where U is an m×m unitary matrix, V is an n×n unitary matrix, ∑ is an m×n matrix, all elements outside the main diagonal of the m×n matrix are 0, and the values ​​on the main diagonal are arranged in descending order, i.e. σ1>σ2>σ3>...;

[0030] Step 2.(3) Set all values ​​in ∑ except the maximum value σ1 to 0 to obtain ∑1; multiply the obtained ∑1 with U and U to obtain the denoised signal A1. m×n (k);

[0031] Step 2.(4) Calculate the percentage of σ1 to all σ, i.e. Determine if the condition f > 0.99 is met; if so, the denoising process ends. If not, use the denoised signal A1. m×n (k) is used as a new initial signal. Steps 2.(1), 2.(2), and 2.(3) are repeated until the preset noise reduction conditions are met.

[0032] Step 3: Extract a portion of the attenuation curve data and fit it using multiple e-exponential methods; extract the location of the attenuation signal trough to obtain the arrival time of the shock wave front.

[0033] Step 3. (1) Extract the attenuation signal range on one optical path channel; find the position X of the minimum value within the entire signal range. min , with X min N data points are extracted before and after the center, i.e., X is extracted. min ±N; then X min The default value is 0. Gaussian linear regression is used for fitting, and the fitting formula is as follows: Where x is the number of data points, and the fitting parameters are a1 and b1; after the first fitting, the regression coefficient R is calculated. 2 And determine R 2 Check if the value >0.99 is true; if it is, the fitting ends here; if not, perform a second fitting, i.e. Then the previous judgment conditions are repeated until the i-th time, R 2 The value >0.99 is met, therefore the final fitted result is: attenuated signal.

[0034] Step 3.(2) Obtain the arrival time of the shock wave front using the attenuation signal V obtained in step 3.(1); determine the rising edge position x of the pump laser pulse. max Defined as the moment when the shock wave is generated; for the fitting results Perform differentiation and search Position x minTherefore, the arrival time of the shock wave front is t = (X min +x min -x max -N)*0.001us;

[0035] Step 3.(3) Denote the arrangement direction of the first array detector perpendicular to the sample stage surface as the Y-axis direction; denote the arrangement direction of the second array detector parallel to the sample stage surface as the X-axis direction. Repeat steps 3.(1) and 3.(2) to obtain the arrival time of the shock wave front of each channel in the X-axis and Y-axis directions;

[0036] Step 3.(4) Fit the relationship between the arrival time of the shock wave obtained in Step 3.(3) and the distance obtained in Step 3.(1) using the formula; In the early stage of plasma evolution, the pressure of the shock wave front is much greater than the pressure of the ambient gas, that is, the ambient gas pressure is negligible. The early stage of laser-induced shock wave propagation is described by the Sedov-Taylor principle. The relationship between the distance R from the shock wave front to the explosion center and the propagation time t is expressed as: R = At q A and q are constant coefficients. In the later stages of plasma evolution, the high-temperature, high-pressure plasma nucleus gradually collapses, at which point the ambient gas pressure becomes significant. During its outward propagation, the shock wave encounters resistance from the ambient gas, causing it to rapidly attenuate to the speed of sound. The later stages of laser-induced shock wave propagation are described using the drag model principle. The relationship between the distance R from the shock wave front to the explosion center and the propagation time t is expressed as: R = R0(1 - e^(-q / t)) -βt ), where R0 is the cutoff distance and β is the drag coefficient. The measured range spans the period before and after the shock wave propagation, and the improved model is: R = At q +vt; where v=R0·β is the product of the cutoff distance R0 and the drag coefficient β; this model also takes into account the period before and after the shock wave propagation, making the fitting prediction more accurate;

[0037] For the arrival time of the shock wave in each channel in the X direction obtained in step 3.(3), use R = At q +vt is fitted; the position-time fitting curve of the X-axis is obtained; for the arrival time of the shock wave of each channel in the Y direction obtained in step 3.(3), R = At ​​is used to fit the curve. q +vt is used for fitting; the position-time fitting curve of the Y-axis is obtained.

[0038] Step 4: Utilize the position-time relationship in two directions to capture the position coordinates in two directions at the same moment, obtain the position data of two points on the shock wave waveform, and then, based on the ellipse equation, fit the shock wave waveform at the corresponding time through the position to extract the propagation path and waveform of the shock wave.

[0039] Using the time of the M-1 signals furthest from the X-axis as a reference, find the corresponding position y on the position-time fitting curve of the Y-axis obtained in step three. i The coordinates along the Y-axis are as follows: (0, h) x ), (0, y2), (0, y3),…, (0, y M The coordinates along the X-axis are as follows: (0, h) x (1.5, h) x (3.0, h) x ), ..., (M·1.5-1.5, 3.5); thus, the positions of the shock waves in the X-axis and Y-axis directions at the same moment were obtained;

[0040] Since the shock wave waveform of laser-loaded energetic materials is elliptical, the equation of the ellipse is: By fitting the shock wave waveform at the specified location and time, the extraction of the shock wave waveform is achieved.

[0041] Step 5: Differentiate the time-position relationship to obtain the time-velocity relationship, and then obtain the corresponding shock wave characteristic velocity; remove outliers from the shock wave characteristic velocities extracted from multiple measurements according to the Laida (3σ) criterion; and use the PLS method to establish a linear regression relationship between the characteristic velocities of different energetic materials and the macroscopic detonation velocity to predict the macroscopic detonation velocity.

[0042] The vt curve can be obtained by differentiating the position-time fitting curve with respect to the Y-axis; that is, the relationship between the shock wave velocity and time in the laser loading direction can be obtained; let t = 0.8us in the vt curve, the shock wave velocity at this time is the characteristic velocity of the shock wave; Q different characteristic velocities are obtained for each sample;

[0043] During repeated acquisition, fluctuations in laser energy and differences in the substrate at the detection points directly affect the interaction between the laser and the material, causing fluctuations in the attenuation signal position and even acquiring abnormal data with deviations from the average value exceeding two or three times the standard deviation. Since the spectral intensity from multiple acquisitions approximates a normal distribution, outlier characteristic velocities are eliminated according to the Laida (3σ) criterion. For a set of spectral data with an average value of μ and a standard deviation of σ, measurements deviating from the average value by more than two standard deviations are collectively referred to as outliers, and data within the interval [μ-2σ, μ+2σ] are selected as valid data.

[0044] A linear regression relationship between the characteristic velocities of different energetic materials and the macroscopic detonation velocity is established by using the PLS method. The macroscopic detonation velocity is then predicted based on the linear regression relationship, thus realizing the extraction of laser-induced energetic material shock waves.

[0045] Beneficial effects:

[0046] 1. This invention discloses a laser-induced shock wave extraction system and method for energetic materials. A nanosecond pulsed laser interacts with an energetic material to generate a shock wave. A continuous probe beam is then shaped by a cylindrical lens and a mask to produce an array of point light sources. These point light sources are filtered and then irradiated point-to-point onto an array of APDs (Active Photodiodes). The voltage changes of the APDs are converted by an analog module and collected and recorded by a data acquisition module to obtain the attenuation signal of the shock wave. After obtaining the attenuation signal data, the SVD algorithm is first used to smooth and denoise the signal data. Then, a portion of the attenuation curve data is extracted and fitted using multiple exponential regressions. The valley position of the attenuation signal is then extracted to obtain the arrival time of the shock wave front at the corresponding position, and a modified power-law model is used to fit its time-position relationship. Two coordinate points on the shock wave front at the same moment are extracted using a specific algorithm, and the shock wave is extracted using an elliptic equation. The time-position relationship is differentiated to obtain the time-velocity relationship, thereby obtaining the corresponding shock wave characteristic velocity. A linear regression relationship between the characteristic velocities of different energetic materials and the macroscopic detonation velocity is established using the PLS method to predict the macroscopic detonation velocity.

[0047] 2. This invention discloses a laser-induced shock wave extraction system and method for energetic materials. By advancing the sample stage by 0.5 mm in a single step, it achieves sampling of 4 points within 10 μs, equivalent to completing the task of a 400,000-frame high-speed camera. A 200,000-frame high-speed camera costs as much as 800,000 yuan, while this invention costs approximately 80,000 yuan. Compared to the high-speed camera required for schlieren imaging, this invention saves 90% of the cost.

[0048] 3. This invention discloses a laser-induced shock wave extraction system and method for energetic materials. It extracts the shock wave from energetic materials using an array of probe lasers and detectors, obtaining the characteristic velocity of the shock wave. Subsequently, linear regression analysis is performed on the shock wave velocity and a known detonation velocity to predict the detonation velocity of the energetic material. By setting the initial distance between the probe beam and the sample stage surface to 2 mm, the minimum detection time is 1.8 μs, while the shortest shooting time of a 200,000-frame high-speed camera is 5 μs. Compared to the high-speed camera required for schlieren imaging, its performance is improved by approximately 60%.

[0049] 4. The present invention discloses a laser-induced shock wave extraction system and method for energetic materials. It utilizes laser-induced energetic materials to generate shock waves and can measure the shock wave velocity of laser-induced energetic materials with a single consumption of only 5-10 mg. By modeling the shock wave velocity and the known detonation velocity, it provides a simple, safe and reliable new method for predicting the detonation velocity of energetic materials. Attached Figure Description

[0050] Figure 1This is a schematic diagram of a laser-induced shock wave extraction system for energetic materials;

[0051] Figure 2 It is the collected shock wave attenuation peak curve;

[0052] Figure 3 This is a diagram illustrating the extraction of X and Y axis coordinates at the same moment;

[0053] Figure 4 It is the extracted shock wave waveform diagram;

[0054] Figure 5 These are the characteristic velocities of shock waves extracted from four types of energetic materials.

[0055] Among them, 1—nanosecond pulse laser, 2—reflector, 3—second probe laser, 4—second cylindrical lens, 5—two-dimensional displacement stage, 6—150mm focusing lens, 7—first data acquisition module, 8—second mask, 9—first probe laser, 10—first cylindrical lens, 11—first mask, 12—first filter, 13—first simulation module, 14—second data acquisition module, 15—second simulation module, 16—second array photodetector, 17—second filter, 18—three-dimensional automatic adjustment sample stage, and 19—first array photodetector. Detailed Implementation

[0056] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.

[0057] like Figure 1 As shown, the laser-induced energetic material shock wave extraction system disclosed in this embodiment includes a nanosecond pulsed laser 1, a reflector 2, a 150mm focusing lens 6, a two-dimensional displacement stage 5, a three-dimensional automatically adjustable sample stage 18, a first probe laser 9, a first cylindrical lens 10, a first mask 11, a first filter 12, a first array photodetector 19, a first simulation module 13, a first data acquisition module 7, a second probe laser 3, a second cylindrical lens 4, a second mask 8, a second filter 17, a second array photodetector 16, and a second simulation module 15. The second data acquisition module 14 is connected as follows: the first detection laser 9 is placed in front of the first cylindrical lens 10, the first mask 11 is placed on the three-dimensional automatic adjustment sample stage 18, and the first array photodetector 19 is connected to the first analog module 13, and then to the first data acquisition module 7; the second detection laser 3 is placed in front of the second cylindrical lens 4, the second mask 8 is placed on the three-dimensional automatic adjustment sample stage 18, and the first array photodetector 16 is connected to the second analog module 14, and then to the second data acquisition module 14. The focusing lens 6 is located directly above the sample stage 18, and the sample is placed on the sample stage 18.

[0058] The laser emitted by nanosecond pulsed laser 1 is focused onto the sample on sample stage 18 after passing through mirror 2 and focusing lens 6, generating a laser-induced shock wave. The laser emitted by the first probe laser 9 passes through the first cylindrical lens 10 and the first mask 11, becoming an array of point light sources at different heights from the sample surface. This array then passes through the first filter 12, and the optical signal is received by the first array photodetector 19. The current signal is transmitted to the first analog module 13, converted into a voltage signal, and received by the first data acquisition module 7. Another set of probe light, emitted by the second probe laser 3, passes through the second cylindrical lens 4 and the second mask 13, becoming an array of point light sources at the same height from the sample. This array of point light sources passes parallel to a portion of the sample above, detecting the laser-induced shock wave. After passing through the second filter 17, the optical signal is received by the second array photodetector 16. The current signal is transmitted to the second analog module 15, converted into a voltage signal, and received by the second data acquisition module 14.

[0059] The nanosecond pulsed laser has a laser wavelength of 1064nm, a pulse width of 9ns, and a single-pulse laser energy that is adjustable from 10-120mJ at 1064nm.

[0060] The reflective lens is used to change the path of the pulsed laser, so that the laser acts perpendicularly on the sample.

[0061] The focusing lens, f = 150 mm, is used to focus the laser emitted by the pulsed laser onto the sample, thereby inducing a shock wave to be generated on the sample.

[0062] The detection laser is a 638nm continuous laser, used as a laser source to generate the detection light.

[0063] The cylindrical lens, f = 8 cm, is used to shrink the spot of the detection laser.

[0064] The mask has a series of 250µm diameter circular holes spaced 1.5mm apart, used to generate point light sources. The diameter needs to be selected according to the actual detector to achieve the best signal-to-noise ratio.

[0065] The filter is a 635nm narrow bandpass filter, used to filter stray light and improve signal quality, while shielding most of the plasma light.

[0066] The array photodetector is a silicon-based avalanche photodiode. The detector is fabricated into a row by combining welding and ultraviolet adhesive curing, and is used to form point-to-point detection with the array point light source.

[0067] The simulation module shown is an integrated circuit board, which mainly provides reverse bias voltage for the avalanche photodiode and converts the current signal of the avalanche photodiode into a voltage signal.

[0068] The data acquisition module consists of three 350MHz bandwidth four-channel oscilloscopes used to record and store the voltage values ​​returned by the analog module.

[0069] The three-dimensional displacement stage is used to place the sample and achieve three-dimensional displacement of the sample.

[0070] The two-dimensional displacement stage is used to adjust the vertical height of the focusing lens to focus the laser focal point 3mm below the sample surface.

[0071] The laser-induced shock wave extraction method for energetic materials disclosed in this embodiment is implemented in the following specific steps:

[0072] Step 1: Collect data using a laser-induced energetic material shock wave extraction system.

[0073] A nanosecond pulsed laser with a wavelength of 1064 nm and a pulse width of 9 ns was used. The excitation energy was adjusted to 110 mJ and focused onto the sample surface 3 mm below the surface through a lens with a focal length of f = 150 mm.

[0074] A first detection laser with an output power of 1W and a wavelength of 638nm is activated. After passing through a first cylindrical lens with a focal length of 8cm, this detection light emits a vertically elliptical beam that is bright in the center and dark around the edges. This elliptical beam then perpendicularly illuminates a first photomask, creating a series of optical paths. A first filter, a bandpass filter with a center wavelength of 635±20nm, is placed in front of the first array detector. Its high-transmission range precisely covers the 638nm detection light used in the experiment. It is placed parallel to the first array detector, 3cm in front. The height of the first photomask is adjusted so that the distance between the lowest optical path and the sample surface is 3.5mm. The position of the first array photodetector is adjusted so that the light emitted from the first photomask is incident point-to-point onto the first array photodetector.

[0075] A second detector laser with an output power of 1W and a wavelength of 638nm is activated. After passing through a second cylindrical lens with a focal length of 8cm, this detector emits a horizontal elliptical beam that is bright in the center and dark around the edges. This elliptical beam then vertically illuminates the second photomask, creating a series of optical paths. A second filter, a bandpass filter with a center wavelength of 635±20nm, is placed in front of the second array detector. Its high-transmission range precisely covers the 638nm detector beam used in the experiment. It is placed parallel to the second array detector, 3cm in front. The height of the second photomask is adjusted so that the distance between the leftmost optical path and the sample surface is 2mm. The position of the second array photodetector is adjusted so that the optical path emitted through the second photomask is incident point-to-point onto the second array photodetector.

[0076] A silicon-based avalanche photodiode with a photosensitive surface area of ​​200 μm, a cutoff frequency of 2 GHz, a detection wavelength of 400-1100 nm, and a typical gain of 100 was used as the detector. Enamelled copper wires with a diameter of 0.4 mm were connected to the anode and cathode pads of the detector, and the soldered module was then placed on a PCB board and fixed with UV-curing adhesive. Six detectors were fixed sequentially using the above method, ensuring that the surfaces of the six detectors were in the same plane. The array detectors were placed horizontally and vertically at a distance of 8 cm from the three-dimensional automatically adjustable sample stage. After fixing, the positions of the detectors could be finely adjusted using the enamelled copper wires to ensure that the detection beam accurately hit the photosensitive surface of the detector, thereby obtaining the optimal initial signal response.

[0077] Turn on both probe lasers and place the sample on the sample stage. Set the oscilloscope to trigger-ready mode and press the single-trigger button on the nanosecond pulse laser. The laser's Q-SYNC signal will trigger the oscilloscope to record and store the signals from each channel. A total of 12 attenuation signal data points are obtained in one measurement.

[0078] After completing one data acquisition, the X and Y axes of the sample stage were adjusted so that the excitation laser hit a new sample surface each time, avoiding the generation of new chemical substances due to repeated ablation of the sample surface. This process was repeated for a total of 30 measurements, yielding 30 sets of data.

[0079] Step 2: Use the SVD algorithm to smooth and denoise the signals of each channel acquired by the data acquisition module, extract the data of the attenuation curve, and fit it using multiple e-exponential methods.

[0080] The SVD algorithm is used to smooth and denoise the signals from each channel acquired by the data acquisition module.

[0081] (1) The acquired signal data is represented by A(k), where k represents the signal data detected when the height between the optical path channel and the sample surface is k; the signal A(k) is decomposed into an m×n matrix, i.e., A(k)→A m×n (k); where 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;

[0082] (2) Signal A m×n (k) can be decomposed into the product of three matrices, i.e., A m×n (k)=U m×n ·∑ m×n ·V m×n ; where U is an m×m unitary matrix, V is an n×n unitary matrix, ∑ is an m×n matrix, all elements outside the main diagonal of the m×n matrix are 0, and the values ​​on the main diagonal are arranged in descending order, i.e. σ1>σ2>σ3>...;

[0083] (3) Set all values ​​in ∑ except the maximum value σ1 to 0 to obtain ∑1; multiply the obtained ∑1 by U and U to obtain the denoised signal A1. m×n (k);

[0084] (4) Calculate the percentage of σ1 to all σ, i.e. Determine if the condition f > 0.99 is met; if so, the denoising process ends. If not, use the denoised signal A1. m×n (k) is used as the new initial signal. Repeat steps (1), (2), and (3) until the condition is met.

[0085] Extract a portion of the decay curve data and fit it using multiple e-exponential methods.

[0086] The attenuation signal range is captured within an optical path; the location X of the minimum value is found within the entire signal range. min , with X min N data points are extracted before and after the center, i.e., X is extracted. min ±1500; then X min The default value is 0. Gaussian linear regression is used for fitting, and the fitting formula is as follows: Where x is the number of data points, and the fitting parameters are a1 and b1; after the first fitting, the regression coefficient R is calculated. 2 And determine R 2 Check if the value >0.99 is true; if it is, the fitting ends here; if not, perform a second fitting, i.e. Then the previous judgment conditions are repeated until the i-th time, R 2 The value >0.99 is met, therefore the final fitted result is: attenuated signal.

[0087] Step 3: Extract the location of the valley of the attenuation signal to obtain the arrival time of the shock wave front.

[0088] After obtaining the fitted attenuation signal, the arrival time of the shock wave front is determined. The rising edge position x of the pump laser pulse is then used. max Defined as the moment when the shock wave is generated; for the fitting results Perform differentiation and search Position x min Therefore, the arrival time of the shock wave front is t = (X min +x min -x max-N)*0.001us; Repeat the above steps to process all the data from other optical paths, and finally obtain 30 sets (12 data points per set) of time and distance data.

[0089] Step 4: Shock wave waveform extraction.

[0090] For each set of data, the direction perpendicular to the sample stage surface of the array detectors is denoted as the Y-axis; the direction perpendicular to the sample stage surface is denoted as the X-axis. After obtaining the time and distance data, the relationship between the two is fitted using a formula. Since the measured range (in both time and distance scales) spans the periods before and after the shock wave propagation, the model is improved: R = At q +vt. Where v = R0·β is the product of the cutoff distance R0 and the drag coefficient β, and A and q are constant coefficients, which are the quantities to be fitted.

[0091] The relationship between the positions and time of each point on the X and Y axes is modeled as: R = At q +vt is used for fitting. Using the times of the last 5 signals on the X-axis as a reference, the corresponding position y is found on the position-time fitting curve on the Y-axis. i Therefore, the newly acquired Y-axis coordinates are as follows: (0, 3.5), (0, y2), (0, y3), (0, y4), (0, y5), (0, y6). In the six sets of data for the X-axis, since the first point in the X-axis was calibrated during the experimental setup and is directly above the laser focal point, the X-axis coordinates are as follows: (0, 3.5), (1.5, 3.5), (3.0, 3.5), (4.5, 3.5), (6, 3.5), (7.5, 3.5). Thus, the positions of the shock waves in the X and Y directions at the same moment have been obtained.

[0092] Since the shock wave waveform of laser-loaded energetic materials is elliptical, the equation of the ellipse is: By obtaining the position coordinates of the shock wave in the X and Y directions at the same moment, the shock wave waveform at the corresponding time can be fitted. This completes the extraction of the shock wave waveform.

[0093] Step 5: Build a model for prediction.

[0094] After obtaining the Rt-fit curve along the Y-axis, its derivative yields the vt curve. After obtaining the vt curve, let t = 0.8 μs, and consider the shock wave velocity at this point as the characteristic velocity of the shock wave. Thirty different characteristic velocities were obtained for each sample.

[0095] The characteristic velocity for eliminating anomalies is based on the Laida (3σ) criterion. Assuming the mean of a set of spectral data is μ and the standard deviation is σ, data within the interval [μ-2σ, μ+2σ] are selected as valid data.

[0096] By establishing a linear regression relationship between the characteristic velocities and macroscopic detonation velocities of different energetic materials using the PLS method, macroscopic detonation velocities can be predicted. The prediction results for four energetic materials are shown in Table 1.

[0097] Table 1

[0098]

[0099] This achievement enables the extraction of laser-induced shock waves from energetic materials and the prediction of detonation velocities. Compared to the national military standard method, which consumes approximately 100 grams or kilograms of explosive charge per measurement, this method requires only milligrams of charge. Detonation parameters for four energetic materials were predicted. Compared to the schlieren method, which consumes the same amount of charge, the velocity prediction error of this method is approximately 15 m / s to 85 m / s. In contrast, the schlieren method using a high-speed camera has an error of approximately 80 m / s to 120 m / s, meaning this method reduces the error by 30% to 60%.

[0100] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A laser-induced shock wave extraction system for energetic materials, characterized in that: It includes a nanosecond pulsed laser, a mirror, a 150mm focusing lens, a two-dimensional displacement stage, a three-dimensional automatically adjustable sample stage, a probe laser, a cylindrical lens, a mask, a filter, an array photodetector, an analog circuit module, and a data acquisition module. The nanosecond pulsed laser is used to interact with energetic materials to generate laser-induced shock waves. The three-dimensional automatic adjustable sample stage is used to adjust the height and position of the sample; The two-dimensional displacement stage is used to adjust the height of the focusing lens above the sample to ensure that the focal point of the laser is inside the sample. There are two detector lasers, namely the first detector laser and the second detector laser, which are respectively deployed in the X-axis and Y-axis directions to generate detector lasers; The cylindrical lens consists of two lenses, a first cylindrical lens and a second cylindrical lens, which are placed behind the corresponding detection lasers to constrain the size of the laser spot and shape the laser spot into an ellipse. There are two photomasks, a first photomask and a second photomask, which are placed behind the corresponding cylindrical lenses to generate an array of light sources at the photomasks. The filter consists of two pieces, namely the first filter and the second filter, which are placed in front of the corresponding array photodetector to filter out stray light and improve the smoothness of the received signal of the detector. The array photodetector is a silicon-based avalanche photodiode. There are two sets: a first array photodetector and a second array photodetector. They are welded together and cured with UV adhesive to form a column for point-to-point reception of detection light signals. There are two analog circuit modules, namely the first analog module and the second analog module, which are respectively connected to each silicon avalanche photodiode and are used to provide bias voltage to the silicon avalanche photodiode and convert current signals into voltage signals. There are two data acquisition modules: the first data acquisition module and the second data acquisition module. There are three 350MHz bandwidth four-channel oscilloscopes, which are connected to the analog circuit module to acquire and record the output voltage of the analog circuit.

2. A method for extracting shock waves from laser-induced energetic materials, based on the laser-induced energetic material shock wave extraction system as described in claim 1, characterized in that: Step 1: Collect data through the system; turn on the first probe laser, and adjust the height of the first mask so that the distance between the lowest optical path channel and the sample surface is [value missing]. Adjust the position of the first array photodetector so that the light path exiting the first mask is incident point-to-point onto the first array photodetector; turn on the second detection laser, and adjust the height of the second mask so that the distance between the leftmost light path channel and the sample surface is [missing information]. Adjust the position of the second array photodetector so that the light path channel emitted through the second mask is incident on the second array photodetector point-to-point; The excitation laser generated by the nanosecond pulsed laser is focused below the sample surface through a lens. Set the oscilloscope to trigger-ready mode, press the single-excitation button on the nanosecond pulse laser, and the Q-SYNC signal from the nanosecond pulse laser will trigger the data acquisition module to record and store the signals from each channel. After completing one data acquisition cycle, adjust the X and Y axes of the sample stage so that the excitation laser hits a new sample surface each time, completing the process. Second measurement; Step 2: Use the SVD algorithm to smooth and denoise the signals from each channel acquired by the data acquisition module, extract the attenuation curve data, and apply it multiple times. The index is fitted; Step 3: Extract the location of the attenuation signal valley to obtain the arrival time of the shock wave front; denote the arrangement direction of the first array detector perpendicular to the sample stage surface as the Y-axis direction; denote the arrangement direction of the second array detector parallel to the sample stage surface as the X-axis direction; use... The time-position relationship of the shock wave leading edge in the Y-axis and X-axis directions is fitted to extract the position of the attenuation signal valley and obtain the arrival time of the shock wave leading edge, where R is the distance from the shock wave leading edge to the explosion center and t is the propagation time. As of the distance and drag coefficient The product of and , where is a constant coefficient, is the quantity to be fitted; Step 4: Utilize the position-time relationship in two directions to capture the position coordinates in the Y-axis and X-axis directions at the same moment, obtain the position data of two points on the shock wave waveform, and then, based on the ellipse equation, fit the shock wave waveform at the corresponding time through the position to extract the propagation path and waveform of the shock wave.

3. The laser-induced shock wave extraction method for energetic materials as described in claim 2, characterized in that: It also includes step five, which involves differentiating the time-position relationship to obtain the time-velocity relationship, thereby determining the corresponding shock wave characteristic velocity; According to Raida (3) The criteria are used to remove outliers from the characteristic velocities of shock waves extracted from multiple measurements; and the macroscopic detonation velocity is predicted by establishing a linear regression relationship between the characteristic velocities of different energetic materials and the macroscopic detonation velocity using the PLS method.

4. The laser-induced shock wave extraction method for energetic materials as described in claim 2 or 3, characterized in that: The implementation method for step one is as follows: The first detection laser is activated. After passing through the first cylindrical lens, the laser emits an elliptical beam that is bright in the center and dark around the edges. This beam perpendicularly illuminates the first photomask, creating a series of optical paths. The first photomask has... A series of circular holes, each with a diameter of 240-260 μm and a spacing of 1.4 mm-1.6 mm, are used. During the initial stage of plasma generation, a high-brightness plasma plume emits bremsstrahlung light, known as plasma radiation. This radiation has a broad spectrum, ranging from 400 to 1100 nm. Since the wavelength of this plasma radiation falls within the response range of the array detector, it significantly affects the detection signal, often resulting in strong noise signals observed on the array detector. To reduce the impact of this plasma radiation on the experiment, a first filter is placed in front of the first array detector. The height of the first mask is adjusted so that the distance between the lowest optical path channel and the sample surface is... Adjust the position of the first array photodetector so that the light path exiting the first mask is incident point-to-point onto the first array photodetector; turn on the second detection laser, which, after passing through the second cylindrical lens, emits an elliptical beam that is bright in the center and dark around the edges, perpendicularly illuminating the second mask and creating a series of light paths. The second mask has... A series of circular holes with a diameter of 240µm-260µm and a spacing of 1.4mm-1.6mm are placed; a second filter is placed in front of the second array detector; the height of the second mask is adjusted so that the distance between the leftmost optical path channel and the sample surface is [missing information]. Adjust the position of the second array photodetector so that the light path channel emitted through the second mask is incident on the second array photodetector point-to-point; A nanosecond pulsed laser is focused below the sample surface using a focusing lens. To avoid the uncertainties caused by high-energy pulsed lasers breaking down the air; Using a silicon-based avalanche photodiode as an array photodetector, enameled copper wires are connected to the anode and cathode pads of the array photodetector, respectively. The soldered module is then placed on a PCB board and fixed with UV-curing adhesive. This process is repeated sequentially. An array of photodetectors ensures The surfaces of the detectors are in the same plane; after fixing, the position of the detectors is finely adjusted using enameled copper wire so that the detection beam hits the photosensitive surface of the array photodetector precisely to obtain the best initial signal response. When the probe laser passes through the shock wave region, the shock wave density distribution is not uniform; when the probe light passes through the disturbed region of the shock wave, the density at the leading edge of the shock wave is relatively higher than that at the trailing edge, thus violating the law of refraction. This determines that when light passes through the shock wave disturbance area, its exit position will be deflected downwards relative to its initial propagation direction; the deflected light spot gradually deviates from the center of the detector's detection surface, due to the photocurrent generated by the photodetector. Depends on incident light power The incident light power It also depends on the irradiated area Therefore, when the probe beam is deflected by the leading edge of the shock wave, less light is on the photosensitive surface of the array photodetector, resulting in an attenuation peak on top of the original signal. Set the oscilloscope to trigger-ready mode and press the single-excitation button on the nanosecond pulse laser. The Q-SYNC signal from the nanosecond pulse laser will trigger the data acquisition module to record and store the signals from each channel. After completing one data acquisition cycle, adjust the X and Y axes of the sample stage so that the excitation laser hits a new sample surface each time, completing the process. Second measurement.

5. The laser-induced shock wave extraction method for energetic materials as described in claim 4, characterized in that: The second step is implemented as follows: Step 2. (1) Use the signal data collected in Step 1 to... express, The height between the optical path channel and the sample surface is... The signal data detected at that time; the signal Decomposed into The matrix, i.e. → ;in , These are the number of rows and the number of columns, respectively. and The product equals the total number of data points; Step 2. (2) Transfer the signal It can be decomposed into the product of three matrices, i.e. ;in for unitary matrix, for The unitary matrix, ∑ is The matrix, The matrix has all elements except those on the main diagonal as 0, and the values ​​on the main diagonal are arranged in descending order. ; Step 2. (3) Divide the maximum value in ∑ Set all values ​​except ∑1 to 0, resulting in ∑1; then combine the resulting ∑1 with... and Multiply to obtain the noise-reduced signal. ; Step 2. (4) Calculate account for all The percentage, that is Determine if the conditions are met: If the condition is met, the denoising process ends; otherwise, the denoised signal is used. As a new initial signal, repeat steps 2.(1), 2.(2), and 2.(3) until the preset noise reduction conditions are met.

6. The laser-induced shock wave extraction method for energetic materials as described in claim 5, characterized in that: The method for implementing step three is as follows: Step 3. (1) Extract the attenuation signal range on one optical path channel; find the position of the minimum value within the entire signal range. ,by Cut off the center and the front and back respectively Data points, i.e., interception Then The default value is 0. Gaussian linear regression is used for fitting, and the fitting formula is as follows: ,in For attenuation signal, The number of data points is given, and the fitting parameters are given. and After the first fitting is completed, the regression coefficients are calculated. and judge Is the condition true? If it is true, the fitting ends here; if it is not true, a second fitting is performed, i.e. Then the previous judgment conditions are repeated until the process reaches the first condition. Second-rate, Therefore, the final fitting result is: attenuated signal. ; Step 3. (2) Attenuation signal obtained through step 3. (1) Obtain the arrival time of the shock wave front; determine the rising edge position of the pump laser pulse. Defined as the moment when the shock wave is generated; for the fitting results Perform differentiation and search Location This allows us to obtain the arrival time of the shock wave front. ; Step 3. (3) The arrangement direction of the first array of photodetectors perpendicular to the sample stage surface is recorded as the Y-axis direction; the arrangement direction of the second array of photodetectors parallel to the sample stage surface is recorded as the X-axis direction; repeat steps 3. (1) and 3. (2) to obtain the arrival time of the shock wave front of each channel in the X-axis and Y-axis directions; Step 3. (4) Fit the relationship between the arrival time of the shock wave obtained in Step 3. (3) and the distance obtained in Step 3. (1) using the formula; In the early stage of plasma evolution, the pressure of the shock wave front is much greater than the pressure of the ambient gas, that is, the ambient gas pressure is negligible; The early stage of laser-induced shock wave propagation is described by the Sedov-Taylor principle; The relationship between the distance R from the shock wave front to the explosion center and the propagation time t is expressed as: , and The constant coefficient is used; in the later stages of plasma evolution, the high-temperature and high-pressure plasma nucleus gradually collapses, at which point the ambient gas pressure cannot be ignored; during the outward propagation of the shock wave, it is subjected to resistance from the ambient gas, causing the shock wave to rapidly attenuate to the speed of sound; the later stages of laser-induced shock wave propagation are described using the drag model principle; the relationship between the distance R from the shock wave front to the explosion center and the propagation time t is expressed as: ,in For the cut-off distance and The drag coefficient is used; the measurement range spans the period before and after shock wave propagation, and the improved model is as follows: ;in As of the distance and drag coefficient The product of the two phases; the model also takes into account the periods before and after the shock wave propagation, resulting in higher accuracy of the fitting prediction. For the arrival time of the shock wave in each channel along the X-axis obtained in step 3.(3), through... Perform fitting; obtain the position-time fitting curve of the X-axis; for the arrival time of the shock wave in each channel in the Y-axis direction obtained in step 3.(3), use... Perform fitting; obtain the position-time fitting curve of the Y-axis.

7. The laser-induced shock wave extraction method for energetic materials as described in claim 6, characterized in that: Step four is implemented as follows: The one furthest from the X-axis Using the time of each signal as a reference, find the corresponding position on the Y-axis position-time fitting curve obtained in step three. The coordinates along the Y-axis are as follows: (0, ... ), (0, ), (0, ), ..., (0, The coordinates along the X-axis are as follows: (0, ... ), (1.5, (3.0) ), ..., ( (3.5); Thus, the positions of the shock waves along the X and Y axes at the same moment were obtained; Since the shock wave waveform of laser-loaded energetic materials is elliptical, the equation of the ellipse is: The shock wave waveform at the corresponding time is fitted to the location; thus, the shock wave waveform is extracted.

8. The laser-induced shock wave extraction method for energetic materials as described in claim 7, characterized in that: Step five is implemented as follows: The derivative of the position-time fitting curve with respect to the Y-axis can be obtained. The curve; that is, the relationship between the shock wave velocity in the laser loading direction and time; let At this point, the shock wave velocity is the characteristic velocity of the shock wave; each sample obtains A different characteristic velocity; Because fluctuations in laser energy and differences in the substrate at the detection points directly affect the interaction between the laser and the material during repeated acquisition, the position of the attenuated signal may fluctuate, even resulting in abnormal data with deviations from the average value exceeding two or three times the standard deviation. Since the spectral intensity from multiple acquisitions approximates a normal distribution, according to Laida (3... The criteria for eliminating anomalies include the characteristic speed. For a set of spectral data, the mean is μ and the standard deviation is... Measurements that deviate from the mean by more than two standard deviations are collectively referred to as outliers, and the interval [μ-2] is selected. μ+2 The data within the brackets is valid. A linear regression relationship between the characteristic velocities of different energetic materials and the macroscopic detonation velocity is established by using the PLS method. The macroscopic detonation velocity is then predicted based on the linear regression relationship, thus realizing the extraction of shock waves from energetic materials induced by excitation laser.

9. The laser-induced shock wave extraction method for energetic materials as described in claim 4, characterized in that: The first mask template has A circular hole with a diameter of 250um and a spacing of 1.5mm; The second mask has A circular hole with a diameter of 250um and a spacing of 1.5mm; Using silicon-based avalanche photodiodes as array photodetectors, 0.4 mm diameter enameled copper wires are used to connect to the anode and cathode pads of the array photodetector respectively. The soldered modules are then placed on a PCB board and fixed with UV-curing adhesive.

Images