Method and device for testing parachute ablated and struck by high-energy laser

Abstract

The invention relates to the technical field of laser striking, in particular to a high-energy laser ablation parachute striking test method and device. The test method comprises the steps of preparing the test device; carrying out a high-energy laser ablation parachute striking test; analyzing a test process and a test result; performing finite element simulation on the test process; and comparing the morphology and mechanical characteristics of the damaged parachute obtained by simulation and test in different speed fields, and adjusting finite element simulation parameters to enable a simulation result to be matched with a test result. The device is high in applicability, can be used for testing the laser ablation resistance of the parachute in various shapes and sizes, and provides a design basis for the laser ablation resistance of the parachute; the finite element simulation method for studying the aerodynamic characteristics of the damaged parachute is established, and the influence of damage degrees of different parts and different structures on the overall flight performance of the parachute is revealed.

Description

Technical Field

[0001] The invention relates to the field of laser strike technology, and in particular to a high-energy laser ablation strike parachute test method and device. Background Art

[0002] Traditional methods of attacking airdropped parachutes mainly include: traditional firepower attack, electronic warfare interference and laser countermeasures. Among them, the main materials of the parachute canopy and parachute rope are nylon, polyester fiber or polyaramid fiber, which are easy to catch fire when exposed to high temperatures. The laser ablation countermeasure is mainly developed based on the characteristics of the material's inability to withstand high temperatures.

[0003] In recent years, with the demand for countering "low, slow and small" drones, high-energy laser counter-drone technology has received attention and has been initially applied. However, the technical characteristics of drone countermeasures and parachute countermeasures are different: first, under the operation of the pilot, the flight trajectory of the drone is difficult to predict, but the parachute generally has no power and its trajectory is easy to predict; second, the shell material of the drone is generally plastic or carbon fiber reinforced resin-based composite materials, which are more resistant to ablation than parachute materials; finally, the drone control system is relatively complex. After losing balance, some multi-rotor drones can adjust the speed of different rotors through control algorithms to maintain balance. Based on the successful application of high-energy laser counter-drones, it is necessary to develop laser counter-parachute technology.

[0004] Therefore, it is necessary to design a high-energy laser ablation parachute test method and device. Summary of the invention

[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a high-energy laser ablation strike parachute test method and device.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: A high-energy laser ablation strike parachute test method, comprising: Step 1, preparing a test device: the test device includes a wind tunnel, a high-energy laser assembly, a high-speed camera and a plurality of parachutes, the wind tunnel is used to blow open the parachutes to simulate the state of the parachutes in flight, the high-energy laser assembly is used to emit high-energy lasers to the parachutes to ablate the parachutes, and the high-speed camera is used to film the test process; Step 2, conducting a high-energy laser ablation test on a parachute: hanging the end of the parachute rope of the parachute at the middle position of the wind tunnel exit, opening the wind tunnel and setting the wind speed range so that the parachute opens normally, turning on the high-speed camera to shoot the posture of the parachute, turning on the high-energy laser assembly to irradiate and ablate the parachute until the parachute cannot continue to fly; replacing the parachute and conducting the test again so that the high-energy laser assembly irradiates and ablates different parts of the parachute, completing the ablation strike test on several parts of the parachute; Step 3, analyzing the test process and test results: analyzing the high-speed video of the parachute being ablated to obtain key time parameters; observing the microscopic morphology of the ablated part of the parachute under an optical microscope, and comparing the ablation degree of different parts of the parachute, as well as the center and boundary morphology of the ablation area of ​​the same part; Step 4, performing finite element simulation on the test process: in the finite element simulation, calculating the mechanical properties of the parachute under different damage degrees of the parachute canopy and parachute ropes; selecting nodes at the ends of the parachute, and deriving the pressure change curve corresponding to the nodes over time; Step 5, comparing the morphology and mechanical characteristics of the damaged parachute obtained by simulation and experiment under different velocity fields, and adjusting the finite element simulation parameters to make the simulation results consistent with the experimental results.

[0007] Furthermore, in step 2, the different parts of the parachute include different positions of the parachute ropes and different positions of the parachute surface.

[0008] Furthermore, in step 3, the key time parameters include and ; The parachute opening time; It is the time from when the laser starts to ablate the local part of the parachute to when the local part of the parachute begins to deform and become unstable but the parachute surface still maintains its normal shape.

[0009] Furthermore, in step 3, the microscopic morphology of the ablated part of the parachute is observed under an optical microscope to compare the ablation degree of different parts of the parachute, as well as the center and boundary morphology of the ablation area of ​​the same part; specifically including: The fluid mechanics equations of the one-dimensional plane Lagrange fluid mechanics code SSS are: ; ; ; ; ; ; ; In the formula, For time; is the Euler coordinate; is the particle velocity; is the specific volume; is the specific internal energy; is the total specific energy; is temperature; is the total pressure; For pressure; for stickiness; is the mass per unit area; is the resultant stress, , All are stress deviator; is the thermal conductivity coefficient; is the laser energy absorbed by the unit mass medium per unit time, ,in, is the linear absorption coefficient of the medium to the laser, is the light intensity per unit grid in the laser absorption area, is the unit grid length; When the SSS code is used for the calculation of the laser-driven flyer process, the laser effect additional term is first added to the right side of equation (3), and the state equation that can describe the state of the laser ablation plasma is introduced; In the first stage, the parachute material absorbs the laser using the solid absorption model. According to the Lambert-Beer-Bouguer law, the light intensity in the solid medium is It decays exponentially with the propagation distance x, that is: ; In the second stage, when the gas temperature is below a certain value, the absorption coefficient of the partially ionized material and is proportional to, expressed as ;constant It increases with increasing temperature, varying between -3 / 2 and 1 / 2. 2; through organic coupling with solid absorption, in the vapor state: ; In the formula, , , are the linear absorption coefficient, density and temperature of the solid metal in the initial state; and is the local density and temperature; During the laser ablation of the parachute material to form a vapor plasma, the laser intensity is At this level, reverse bremsstrahlung absorption is the main absorption mechanism in the parachute material vapor, that is, in the third stage, the linear absorption coefficient of the plasma is: ; In the formula, is the quantum mechanics correction factor, which is approximately 1; is the average ionization charge number of the ion; is the incident laser wavelength; is the ion number density; is the electron temperature.

[0010] Furthermore, in step 4, it specifically includes: Use CATIA to draw the 3D model of the test device and air flow field, and use hypermesh software to divide the mesh, which is used to simulate the flight performance of parachutes with different parts of damage, and export the k file that can be used for ls-prepost software operation; In the ls-prepost software, add the rope unit of the parachute rope to simulate the force process of the parachute surface under the constraint of the parachute rope; Submit the problem to the ls-dyna solver to calculate the mechanical properties of the parachute under different degrees of damage to the parachute canopy and parachute ropes; select the nodes at the ends of the parachute and derive the pressure-time curve corresponding to the nodes.

[0011] The present invention also provides a high-energy laser ablation strike parachute test device, including a wind tunnel, a high-energy laser assembly, a high-speed camera and a plurality of parachutes; The end of the parachute rope is hung at the middle position of the wind tunnel exit; The wind tunnel is used to blow open the parachute to simulate the state of the parachute in flight; The high-energy laser assembly is arranged on the side of the parachute, and is used to emit high-energy laser to the parachute to ablate the parachute; The high-speed camera is arranged on the side of the parachute and is used to shoot the test process.

[0012] Furthermore, the high-energy laser assembly includes a high-energy laser, a rotating platform, and a heat sink; The high-energy laser is arranged on the rotating platform and is used for emitting high-energy laser; The rotating platform is used to drive the high-energy laser to rotate so as to adjust the emission direction of the high-energy laser; The heat sink is in contact with the high energy laser and is used for dissipating heat from the high energy laser.

[0013] From the above description of the present invention, it can be seen that, compared with the prior art, the high-energy laser ablation strike parachute test method and device of the present invention have the following beneficial effects: 1. The invention has strong applicability and can be used to test the anti-laser ablation performance of parachutes of various shapes and sizes, providing a design basis for the anti-laser ablation performance of parachutes; 2. The present invention is easy to test and has low test cost. By generating wind fields with different flow rates through a low-speed wind tunnel, the flight performance of a parachute at different landing speeds can be simulated; 3. The present invention facilitates data collection. The high-speed camera is set up on the ground, which solves the difficulty of collecting the deformation of the moving parachute in the traditional outdoor test. It is easy to focus the lens and collect the parachute deformation video; 4. The present invention establishes a finite element simulation method for studying the aerodynamic characteristics of a damaged parachute, revealing the influence of different parts and different degrees of structural damage on the overall flight performance of the parachute. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A flow chart of the steps of a high-energy laser ablation strike parachute test method according to an embodiment of the present invention; Figure 2 It is a structural schematic diagram of a high-energy laser ablation strike parachute test device in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a high energy laser assembly in an embodiment of the present invention; Figure 4 is a curve of pressure variation over time corresponding to a node in an embodiment of the present invention; Explanation of the numbers in the figure: 1 wind tunnel, 2 high-energy laser assembly, 3 high-speed camera, 4 parachute, 201 high-energy laser, 202 rotating pan-tilt head, 203 radiator, 401 parachute rope, 402 parachute surface. DETAILED DESCRIPTION

[0015] The technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0016] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0017] Reference Figure 1 As shown, a preferred embodiment of the present invention, a high energy laser ablation strike parachute test method, comprises: Step 1, preparing a test device: the test device includes a wind tunnel 1, a high-energy laser assembly 2, a high-speed camera 3 and a plurality of parachutes 4, the wind tunnel 1 is used to blow open the parachutes 4 to simulate the state of the parachutes 4 in flight, the high-energy laser assembly 2 is used to emit high-energy lasers to the parachutes 4 to ablate the parachutes 4, and the high-speed camera 3 is used to shoot the test process; Step 2, conducting a high-energy laser ablation test on a parachute: hang the end of the parachute rope 401 of the parachute 4 at the middle position of the exit of the wind tunnel 1, open the wind tunnel 1 and set the wind speed range so that the parachute 4 opens normally, turn on the high-speed camera 3 to shoot the posture of the parachute 4, turn on the high-energy laser assembly 2 to irradiate and ablate the parachute 4 until the parachute 4 cannot continue to fly; replace the parachute 4 and conduct the test again so that the high-energy laser assembly 2 irradiates and ablates different parts of the parachute 4, and complete the ablation test on several parts of the parachute 4; Step 3, analyzing the test process and test results: analyzing the high-speed video of the parachute 4 being ablated to obtain key time parameters; observing the microscopic morphology of the ablated part of the parachute 4 under an optical microscope, and comparing the ablation degree of different parts of the parachute 4, as well as the center and boundary morphology of the ablation area of ​​the same part; Step 4, finite element simulation is performed on the test process: in the finite element simulation, the mechanical properties of the parachute 4 are calculated under different damage degrees of the parachute canopy and the parachute rope 401 of the parachute 4; nodes at the ends of the parachute 4 are selected, and the pressure variation curve corresponding to the node is derived; wherein the pressure variation curve is referred to Figure 4 As shown in the figure, when the parachute is subjected to laser ablation, ablation damage or even holes will be formed in the local area. Subsequently, when the pre-damaged parachute falls, the local area with pre-damage is prone to stress concentration under the action of air, that is, the node with increased pressure. Figure 4In the 0-20ms, the parachute is in a slow deformation stage, and the pressure at the node does not increase significantly. From 20ms, the pressure at the node increases significantly. At 800ms, the pressure at the node reaches a peak. Therefore, by testing the pressure at the pre-damaged node of the parachute, the service performance of the parachute after laser ablation can be determined.

[0018] Step 5, comparing the morphology and mechanical characteristics of the damaged parachute 4 obtained by simulation and experiment under different velocity fields, and adjusting the finite element simulation parameters to make the simulation results consistent with the experimental results.

[0019] As a preferred embodiment of the present invention, it may also have the following additional technical features: In this embodiment, in step 2, the different parts of the parachute 4 include different positions of the parachute rope 401 and different positions of the parachute canopy 402.

[0020] In this embodiment, in step 3, the key time parameters include and ; The parachute opening time; It is the time from when the laser starts to ablate the part of the parachute 4 to when the part of the parachute 4 starts to become deformed and unstable but the parachute surface 402 still maintains a normal shape.

[0021] In this embodiment, in step 3, the microscopic morphology of the ablated part of the parachute 4 is observed under an optical microscope to compare the ablation degree of different parts of the parachute 4 and the center and boundary morphology of the ablation area of ​​the same part; specifically, the following steps are performed: The fluid mechanics equations of the one-dimensional plane Lagrange fluid mechanics code SSS are: ; ; ; ; ; ; ; In the formula, For time; is the Euler coordinate; is the particle velocity; is the specific volume; is the specific internal energy; is the total specific energy; is temperature; is the total pressure; For pressure; for stickiness; is the mass per unit area; is the resultant stress, , All are stress deviator; is the thermal conductivity coefficient; is the laser energy absorbed by the unit mass medium per unit time, ,in, is the linear absorption coefficient of the medium to the laser, is the light intensity per unit grid in the laser absorption area, is the unit grid length; When the SSS code is used for the calculation of the laser-driven flyer process, the laser effect additional term is first added to the right side of equation (3), and the state equation that can describe the state of the laser ablation plasma is introduced; In the first stage, the absorption of laser by parachute 4 material adopts the solid absorption model. According to the Lambert-Beer-Bouguer law, the light intensity in the solid medium is It decays exponentially with the propagation distance x, that is: ; In the second stage, when the gas temperature is below a certain value, the absorption coefficient of the partially ionized material and is proportional to, expressed as ;constant It increases with increasing temperature, varying between -3 / 2 and 1 / 2. 2; through organic coupling with solid absorption, in the vapor state: ; In the formula, , , are the linear absorption coefficient, density and temperature of the solid metal in the initial state; and is the local density and temperature; During the process of laser ablation of parachute 4 material to form vapor plasma, the laser intensity is At this level, reverse bremsstrahlung absorption is the main absorption mechanism in the vapor of parachute 4 material, that is, in the third stage, the linear absorption coefficient of the plasma is: ; In the formula, is the quantum mechanics correction factor, which is approximately 1; is the average ionization charge number of the ion; is the incident laser wavelength; is the ion number density; is the electron temperature.

[0022] In this embodiment, step 4 specifically includes: Use CATIA to draw the three-dimensional model of the test device and air flow field, and use hypermesh software to divide the mesh, which is used to simulate the flight performance of parachute 4 with different parts of damage, and export the k file that can be used for ls-prepost software operation; In the ls-prepost software, the rope unit of the parachute rope 401 is added to simulate the force process of the parachute surface 402 under the restriction of the parachute rope 401; Submit the solution to the ls-dyna solver to calculate the mechanical properties of the parachute 4 under different degrees of damage to the parachute cover 402 and the parachute rope 401; select the nodes at the ends of the parachute 4 and derive the pressure-time curve corresponding to the nodes.

[0023] Reference Figures 2 to 3 As shown, the present invention also provides a high-energy laser ablation strike parachute test device, comprising a wind tunnel 1, a high-energy laser assembly 2, a high-speed camera 3 and a plurality of parachutes 4; The end of the parachute rope 401 of the parachute 4 is hung at the middle position of the exit of the wind tunnel 1; The wind tunnel 1 is used to blow open the parachute 4 to simulate the state of the parachute 4 in flight; The high-energy laser assembly 2 is arranged on the side of the parachute 4, and is used to emit high-energy laser to the parachute 4 to ablate the parachute 4; The high-speed camera 3 is arranged on the side of the parachute 4 to shoot the test process.

[0024] In this embodiment, the high energy laser assembly 2 includes a high energy laser 201, a rotating platform 202, and a heat sink 203; The high energy laser 201 is arranged on the rotating platform 202 and is used to emit high energy laser; The rotating platform 202 is used to drive the high-energy laser 201 to rotate so as to adjust the emission direction of the high-energy laser; The heat sink 203 is in contact with the high energy laser 201 and is used to dissipate heat for the high energy laser 201 .

[0025] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and improved concepts of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. A high energy laser ablation parachute test method, characterized in that: include: Step 1, preparing a test device: the test device includes a wind tunnel, a high-energy laser assembly, a high-speed camera and a plurality of parachutes, the wind tunnel is used to blow open the parachutes to simulate the state of the parachutes in flight, the high-energy laser assembly is used to emit high-energy lasers to the parachutes to ablate the parachutes, and the high-speed camera is used to film the test process; Step 2, conducting a high-energy laser ablation test on a parachute: hanging the end of the parachute rope of the parachute at the middle position of the wind tunnel exit, opening the wind tunnel and setting the wind speed range so that the parachute opens normally, turning on the high-speed camera to shoot the posture of the parachute, turning on the high-energy laser assembly to irradiate and ablate the parachute until the parachute cannot continue to fly; replacing the parachute and conducting the test again so that the high-energy laser assembly irradiates and ablates different parts of the parachute, completing the ablation strike test on several parts of the parachute; Step 3, analyzing the test process and test results: analyzing the high-speed video of the parachute being ablated to obtain key time parameters; observing the microscopic morphology of the ablated part of the parachute under an optical microscope, and comparing the ablation degree of different parts of the parachute, as well as the center and boundary morphology of the ablation area of ​​the same part; Step 4, performing finite element simulation on the test process: in the finite element simulation, calculating the mechanical properties of the parachute under different damage degrees of the parachute canopy and parachute ropes; selecting nodes at the ends of the parachute, and deriving the pressure change curve corresponding to the nodes over time; Step 5, comparing the morphology and mechanical characteristics of the damaged parachute obtained by simulation and experiment under different velocity fields, and adjusting the finite element simulation parameters to make the simulation results consistent with the experimental results.

2. A high energy laser ablation strike parachute test method according to claim 1, characterized in that: In step 2, the different parts of the parachute include different positions of the parachute ropes and different positions of the parachute surface.

3. A high energy laser ablation strike parachute test method according to claim 1, characterized in that: In step 3, the key time parameters include and ; The parachute opening time; It is the time from when the laser starts to ablate the local part of the parachute to when the local part of the parachute begins to deform and become unstable but the parachute surface still maintains its normal shape.

4. A high energy laser ablation strike parachute test method according to claim 1, characterized in that: In step 3, the microscopic morphology of the ablated part of the parachute is observed under an optical microscope to compare the ablation degree of different parts of the parachute, as well as the center and boundary morphology of the ablation area at the same part; specifically including: The fluid mechanics equations of the one-dimensional plane Lagrange fluid mechanics code SSS are: ； ； ； ； ； ； ； In the formula, For time; is the Euler coordinate; is the particle velocity; is the specific volume; is the specific internal energy; is the total specific energy; is temperature; is the total pressure; For pressure; for stickiness; is the mass per unit area; is the resultant stress, , All are stress deviator; is the thermal conductivity coefficient; is the laser energy absorbed by the unit mass medium per unit time, ,in, is the linear absorption coefficient of the medium to the laser, is the light intensity per unit grid in the laser absorption area, is the unit grid length; When the SSS code is used for the calculation of the laser-driven flyer process, the laser effect additional term is first added to the right side of equation (3), and the state equation that can describe the state of the laser ablation plasma is introduced; In the first stage, the parachute material absorbs the laser using the solid absorption model. According to the Lambert-Beer-Bouguer law, the light intensity in the solid medium is It decays exponentially with the propagation distance x, that is: ； In the second stage, when the gas temperature is below a certain value, the absorption coefficient of the partially ionized material and is proportional to, expressed as ;constant It increases with increasing temperature, ranging from -3 / 2 to 1 / 2. 2; through organic coupling with solid absorption, in the vapor state: ； In the formula, , , are the linear absorption coefficient, density and temperature of the solid metal in the initial state; and is the local density and temperature; During the laser ablation of the parachute material to form a vapor plasma, the laser intensity is At this level, reverse bremsstrahlung absorption is the main absorption mechanism in the parachute material vapor, that is, in the third stage, the linear absorption coefficient of the plasma is: ； In the formula, is the quantum mechanics correction factor, which is approximately 1; is the average ionization charge number of the ion; is the incident laser wavelength; is the ion number density; is the electron temperature.

5. The high energy laser ablation strike parachute test method according to claim 1, characterized in that: In the step 4, it specifically includes: Use CATIA to draw the 3D model of the test device and air flow field, and use hypermesh software to divide the mesh, which is used to simulate the flight performance of parachutes with different parts of damage, and export the k file that can be used for ls-prepost software operation; In the ls-prepost software, add the rope unit of the parachute rope to simulate the force process of the parachute surface under the constraint of the parachute rope; Submit the problem to the ls-dyna solver to calculate the mechanical properties of the parachute under different degrees of damage to the parachute canopy and parachute ropes; select the nodes at the ends of the parachute and derive the pressure-time curve corresponding to the nodes.

6. A high energy laser ablation parachute test device, characterized in that: Includes a wind tunnel, a high-energy laser package, a high-speed camera, and several parachutes; The end of the parachute rope is hung at the middle position of the wind tunnel exit; The wind tunnel is used to blow open the parachute to simulate the state of the parachute in flight; The high-energy laser assembly is arranged on the side of the parachute, and is used to emit high-energy laser to the parachute to ablate the parachute; The high-speed camera is arranged on the side of the parachute and is used to shoot the test process.

7. The high energy laser ablation strike parachute test device according to claim 6, characterized in that: The high-energy laser assembly includes a high-energy laser, a rotating platform, and a radiator; The high-energy laser is arranged on the rotating platform and is used for emitting high-energy laser; The rotating platform is used to drive the high-energy laser to rotate so as to adjust the emission direction of the high-energy laser; The heat sink is in contact with the high energy laser and is used for dissipating heat from the high energy laser.

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