A device and method for measuring Hugoniot relationship parameters of an artificial bird based on a Hopkinson rod

Abstract

The present application provides a device and method for measuring the Hugoniot relationship parameters of an artificial bird based on a Hopkinson bar, which relates to the technical field of bird impact tests. The device avoids the disadvantage of the traditional method of indirectly calculating a certain physical quantity through the Hugoniot pressure relationship by directly measuring the shock wave velocity and the particle velocity after the wave. Secondly, the device can effectively decouple the deformation of the device from the dynamic behavior of the bird body, thereby reducing the influence of the material size and stiffness characteristics of the measuring device on the constitutive model of the bird body. The method conducts tests on artificial birds of different densities through test preparation, testing, measurement data processing, measurement data correction and validity analysis, and empirical index analysis, fits the Hugoniot curves of artificial birds of different densities, and then obtains the constitutive model and parameters of the bird body. This method of forward derivation of the state equation and its parameters based on the theory of physical state will not cause the constitutive model and parameters of the bird body to change with changes in working conditions, thereby improving the universality of the test data.

Description

Technical Field

[0001] The present application relates to the technical field of bird strike tests, and in particular to a device and method for measuring Hugoniot relationship parameters of an artificial bird based on a Hopkinson rod. Background Art

[0002] Verifying the load-bearing capacity of aircraft structures is a fundamental requirement of aircraft design. Impact loads are one of the most common types of loads an aircraft may encounter. During flight, front structures such as the windshield, nose, and wings are inevitably impacted by external objects such as birds, hail, and rocks. Due to their high destructiveness and frequency, bird strikes have been classified as a Category "A" aviation disaster by the Federation Aeronautique Internationale (Fédération Aéronautique Internationale). Impact testing is the ultimate and most effective verification method for aircraft structural impact resistance design studies.

[0003] Research on bird strike resistance in aircraft involves highly complex nonlinear mechanics, as the physical process of a bird strike is often accompanied by severe deformation or even localized damage to the aircraft structure. This makes accurate description difficult to achieve using theoretical analysis alone. Furthermore, the high cost and long lead times of bird strike testing significantly restrict its practical application. Therefore, the bird strike resistance design of modern aircraft structures is highly dependent on numerical simulation technology.

[0004] Current finite element simulation studies of bird strikes typically employ a coupled approach, where the deformations of the bird and the structure interact. For example, the bird is numerically discretized using smoothed particle hydrodynamics (SPH), while the target structure is numerically discretized using the Lagrange method. Therefore, the material constitutive models and parameters of both the bird and the aircraft structure are crucial foundations for finite element simulation studies. Determining the bird's constitutive model and parameters typically employs an inversion method. Specifically, based on the application conditions of the bird numerical model, equivalent and simplified structural response measurement tests must be designed to obtain systematic basic test data, which serves as a benchmark for determining the constitutive model and inverting the constitutive parameters.

[0005] However, these methods fall under the purview of inverse dynamics research, and the resulting bird constitutive model and parameters vary with operating conditions, failing to meet the need for universal applicability. Therefore, the study of bird constitutive models and parameters can be based on the theory of physical state, where the equation of state and its parameters are derived from the forward derivation. This allows the constitutive model and parameters to be regressed to the inherent properties of the material, allowing for a more physically meaningful description of its dynamic mechanical behavior.

[0006] In order to derive the bird body constitutive model and parameters suitable for finite element simulation of aircraft structure anti-bird strike, it is necessary to first fit the Hugoniot relationship of the artificial bird (i.e., the shock wave velocity V sand the particle velocity after the wave V p The linear relationship between the medium sound velocity and C 0 and the linear Hugoniot relation constant k The existing test methods for the Hugoniot relationship of artificial birds are mainly based on the impact test of birds hitting rigid targets or flat plates to obtain the artificial bird V s and V p Hugoniot relationship.

[0007] However, in the bird strike rigid target method, V p is obtained directly from the impact test, and V s is calculated indirectly through the Hugoniot pressure relationship; similarly, in the flying plate impact test method, V s is obtained directly from the impact test, and V p It is calculated indirectly through the Hugoniot pressure relationship. Therefore, these methods cannot directly measure the artificial bird's decoupled from the structural deformation. V p and V s , which affects the accuracy and universality of the data. Summary of the Invention

[0008] The purpose of this application is to solve the problem that the existing artificial bird Hugoniot relationship test method cannot directly measure the artificial bird decoupled from the structural deformation. V p and V s To overcome the shortcomings of the present invention, a device and method for measuring the Hugoniot relationship parameters of an artificial bird based on a Hopkinson rod are provided.

[0009] To achieve the above objectives, the technical solutions adopted in this application are as follows:

[0010] In one aspect of the present application, a device for measuring Hugoniot relationship parameters of an artificial bird based on a Hopkinson bar is provided, comprising a bracket and a Hopkinson bar movably arranged on the bracket. The Hopkinson bar comprises an impact bar, an incident bar, and a transmission bar arranged in sequence along an axial direction. A gap is defined between the incident bar and the transmission bar for clamping the artificial bird. The impact bar is driven to impact the incident bar to generate a shock wave. The shock wave propagates through the incident bar to the artificial bird. Part of the shock wave is reflected by the artificial bird to the incident bar to form a reflected wave, and part of the shock wave is transmitted through the artificial bird to the transmission bar to form a transmitted wave.

[0011] A first strain gauge group and a second strain gauge group are arranged axially and spaced apart on the periphery of the incident rod, and a third strain gauge group is arranged on the periphery of the transmission rod. The first strain gauge group, the second strain gauge group, and the third strain gauge group generate voltage signals for measuring the strains of the shock wave, the reflected wave, and the transmitted wave, respectively. The post-wave particle velocity of the artificial bird is calculated based on the strains of the shock wave, the reflected wave, and the transmitted wave.

[0012] A first piezoelectric film sensor and a second piezoelectric film sensor are respectively arranged on the clamping surfaces of the incident rod and the transmission rod. The first piezoelectric film sensor and the second piezoelectric film sensor generate voltage signals respectively for measuring the normal forces of the two end surfaces of the artificial bird along the axial direction. The shock wave velocity of the artificial bird is calculated based on the time difference between the voltage signals generated by the first piezoelectric film sensor and the second piezoelectric film sensor.

[0013] Furthermore, the device also includes an energy absorbing device fixedly arranged on the bracket, and the Hopkinson rod also includes an absorption rod, which is axially arranged on the side of the transmission rod away from the incident rod, and the end of the absorption rod away from the transmission rod is inserted into the energy absorbing device to absorb the shock wave that is not reflected and transmitted.

[0014] Furthermore, the impact rod, the incident rod, the transmission rod and the absorption rod are coaxially arranged.

[0015] Furthermore, the diameters of the impact rod, incident rod, transmission rod and absorption rod are the same, which are 1.0 to 1.2 times the diameter of the circumscribed circle of the artificial bird with the largest mass in the test outline.

[0016] Furthermore, the device also includes a normal camera and an oblique camera arranged on the same side of the artificial bird. The optical axis of the normal camera is perpendicular to the axis of the Hopkinson rod, and the angle between the optical axis of the oblique camera and the axis of the Hopkinson rod is an acute angle, so as to capture the deformation process of the artificial bird from different fields of view.

[0017] Furthermore, the distance between the first strain gauge group and the incident rod near the end of the impact rod is 1 / 4 to 1 / 3 of the length of the incident rod, the distance between the second strain gauge group and the incident rod near the end of the transmission rod is 1 / 4 to 1 / 3 of the length of the incident rod, and the distance between the third strain gauge group and the transmission rod near the end of the incident rod is 1 / 4 to 1 / 3 of the length of the transmission rod.

[0018] Furthermore, the first strain gauge group includes at least two strain gauges arranged axially symmetrically on both sides of the incident rod, the second strain gauge group includes at least two strain gauges arranged axially symmetrically on both sides of the incident rod, and the third strain gauge group includes at least two strain gauges arranged axially symmetrically on both sides of the transmission rod.

[0019] Another aspect of the present application provides a method for measuring Hugoniot relationship parameters of an artificial bird based on a Hopkinson bar, the method being implemented by any of the above-mentioned devices, the method comprising:

[0020] Test preparation: Determine the diameters of the impact rod, incident rod, and transmission rod based on the diameter of the artificial bird; determine the lengths of the impact rod, incident rod, and transmission rod based on the strain and stress requirements of the artificial bird;

[0021] The experiment involved driving the impact rod to impact the incident rod to generate a shock wave. The shock wave propagated through the incident rod to the artificial bird. Part of the shock wave was reflected by the artificial bird to the incident rod, forming a reflected wave. Part of the shock wave was transmitted through the artificial bird to the transmission rod, forming a transmitted wave. The first, second, and third strain gauge groups were used to measure the strains of the shock wave, reflected wave, and transmitted wave, respectively. The first and second piezoelectric film sensors were used to measure the normal forces on the two end faces of the artificial bird along the axial direction, respectively.

[0022] Measurement data processing: The post-wave particle velocity of the artificial bird is calculated based on the strain of the shock wave, reflected wave, and transmitted wave. The calculation formula is:

[0023] (6)

[0024] in, V p is the particle velocity after the wave of the artificial bird, C 0 is the one-dimensional elastic wave velocity of the impact rod, , E is the elastic modulus of the impact rod, ρ 0 is the density of the impact rod, ε i is the strain of the shock wave, ε r is the strain of the reflected wave, ε t is the strain of the transmitted wave;

[0025] The shock wave velocity of the artificial bird is calculated based on the time difference of the voltage signal generated when measuring the normal force on the two end surfaces of the artificial bird along the axial direction. The calculation formula is:

[0026] (7)

[0027] in, V s is the shock wave velocity of the artificial bird, L G is the length of the artificial bird, t input is the time when the first piezoelectric film sensor starts to generate a voltage signal, t outputis the time when the second piezoelectric film sensor starts to generate a voltage signal;

[0028] Measurement data correction and validity analysis: The strains measured by the first, second, and third strain gauge groups are corrected using Fourier transform. The corrected normal forces on the artificial bird's two axial end faces are calculated based on the corrected strains. These corrected normal forces on the artificial bird's two axial end faces are then compared with the normal forces measured by the first and second piezoelectric film sensors to determine the validity of the measurement data.

[0029] Empirical indicator analysis: Repeat the test preparation to measurement data correction and validity analysis for artificial birds of different densities, fit the Hugoniot curves of artificial birds of different densities regarding the post-wave particle velocity and shock wave velocity, compare the slopes and intercepts of the Hugoniot curves of artificial birds of different densities, and determine the influence of the density of the artificial bird on its mechanical behavior.

[0030] Furthermore, during the test preparation, the lengths of the impact rod, incident rod, and transmission rod are determined based on the strain and stress requirements of the artificial bird, including:

[0031] Determine the lengths of the incident and transmitted rods:

[0032] Assume that the incident rod and the transmitted rod have the same preset lengths, both L’ , preset lengths of incident and transmitted rods L’ The strain of the artificial bird measured should be free from the waveform superposition of shock waves and reflected waves;

[0033] If the time required from the shock wave reaching the second strain gauge group to the reflected wave propagating along the incident rod back to the second strain gauge group is greater than the width of the shock wave, the preset lengths of the incident rod and the transmission rod are increased. L’ Determined as the length of the incident rod and the transmitted rod L ;

[0034] Determine the length of the striker rod:

[0035] Preset length of striker rod L B ’ The strain of the artificial bird measured should not be superimposed by the shock wave and the reflected wave. At the same time, the preset length of the impact rod should be L B ’ It should be possible to achieve stress balance during the loading process of the artificial bird;

[0036] The calculation formula for the width of the shock wave is:

[0037] (1)

[0038] in, ΔT is the width of the shock wave, C 0 is the one-dimensional elastic wave velocity of the impact rod, , E is the elastic modulus of the impact rod and the incident rod, ρ 0 is the density of the impact rod and the incident rod;

[0039] The calculation formula for the number of times the shock wave propagates back and forth in the artificial bird is:

[0040] (2)

[0041] in, n is the number of round trips in the artificial bird, C G is the one-dimensional elastic wave velocity of the artificial bird, L G is the length of the artificial bird;

[0042] If the time required from the shock wave reaching the second strain gauge group to the reflected wave propagating back to the second strain gauge group along the incident rod is greater than the width of the shock wave, and the number of times the shock wave propagates back and forth in the artificial bird is greater than 3, so that stress balance is achieved during the loading process of the artificial bird, then the preset length of the impact rod is increased. L B ’ Determined as the length of the striker rod L B .

[0043] Furthermore, in the measurement data correction and validity analysis, correcting the strains measured by the first strain gauge group, the second strain gauge group, and the third strain gauge group by Fourier transform includes converting the strains measured by the first strain gauge group and the second strain gauge group from the time domain to the frequency domain by Fourier transform. Then, the one-dimensional wave equation of the Hopkinson bar becomes:

[0044] (8)

[0045] The general solution to this one-dimensional wave equation is:

[0046] (9)

[0047] in, is the angular frequency, x is any length of the Hopkinson bar along the axial direction, is the strain in frequency domain analysis, function and is the strain in the Hopkinson bar x The Fourier form of axial propagation, the complex exponential function and The modulus and phase reflect the shock wave attenuation and propagation, γ is the propagation coefficient, and attenuation coefficient and phase velocity The calculation formula is:

[0048] (10)

[0049] in, i is the imaginary number in the complex function, the attenuation coefficient is a positive even function, wave number is an odd function;

[0050] Therefore, the Fourier transform of the axial particle velocity and normal force at any length of the Hopkinson rod is:

[0051] (11)

[0052] (12)

[0053] in, is the axial particle velocity at any length of the Hopkinson rod in frequency domain analysis, is the normal force of the Hopkinson bar at any length in the frequency domain analysis, A is the cross-sectional area of the incident and transmitted rods;

[0054] The attenuation coefficient is calculated from the strain of the shock wave measured by the first strain gauge group and wave number , the attenuation coefficient is calculated from the strain of the reflected wave measured by the second strain gauge group and wave number ;Pick and The average value of the attenuation coefficient ,Pick and The average value of the wave velocity ,Will and By substituting the Fourier transform of the axial particle velocity and normal force at any length of the Hopkinson rod, we can obtain the frequency domain form of the corrected velocity and normal force of the two end surfaces of the artificial bird along the axial direction. Then, through the inverse Fourier transform, we can obtain the time domain form to complete the correction of the strains measured by the first strain gauge group, the second strain gauge group, and the third strain gauge group.

[0055] Furthermore, in the measurement data correction and validity analysis, the corrected normal force of the artificial bird along the axial end faces is calculated based on the corrected strain, and the corrected normal force of the artificial bird along the axial end faces is compared with the normal force measured by the first piezoelectric film sensor and the second piezoelectric film sensor to determine the validity of the measurement data. The method includes: calculating the corrected normal force peak value of the artificial bird along the axial end faces based on the corrected strains of the first strain gauge group, the second strain gauge group and the third strain gauge group. and , and The time of occurrence is and ;

[0056] The peak values of the normal forces on both ends of the artificial bird along the axial direction are measured by the first piezoelectric film sensor and the second piezoelectric film sensor. and , and The time of occurrence is and ;

[0057] The validity judgment formula of the measurement data of the first piezoelectric film sensor is:

[0058] (17)

[0059] If satisfied and The difference is less than 5%, and and If the difference is less than 5%, it is determined that the measurement data of the first piezoelectric film sensor is valid;

[0060] The validity judgment formula of the measurement data of the second piezoelectric film sensor is:

[0061] (18)

[0062] If satisfied and The difference is less than 5%, and and If the difference is less than 5%, it is determined that the measurement data of the second piezoelectric film sensor is valid.

[0063] The beneficial effects of this application include:

[0064] The present application provides a device for measuring the Hugoniot relationship parameters of an artificial bird based on a Hopkinson bar, comprising a bracket and a Hopkinson bar movably arranged on the bracket. The Hopkinson bar comprises an impact bar, an incident bar, and a transmission bar arranged in sequence along the axial direction, with a gap between the incident bar and the transmission bar for clamping the artificial bird. The impact bar is driven to impact the incident bar to generate a shock wave, which propagates through the incident bar to the artificial bird. Part of the shock wave is reflected by the artificial bird to the incident bar to form a reflected wave, and part of the shock wave is transmitted through the artificial bird to the transmission bar to form a transmitted wave. A first strain gauge group and a second strain gauge group are arranged axially at intervals on the periphery of the incident bar, and a third strain gauge group is arranged on the periphery of the transmission bar. The first strain gauge group, the second strain gauge group, and the third strain gauge group are respectively used to generate voltage signals to measure the strain of the shock wave, the reflected wave, and the transmitted wave. The post-wave particle velocity of the artificial bird is calculated based on the strain of the shock wave, the reflected wave, and the transmitted wave. A first piezoelectric film sensor and a second piezoelectric film sensor are respectively provided on the clamping surfaces of the incident rod and the transmission rod. The first piezoelectric film sensor and the second piezoelectric film sensor are respectively used to generate voltage signals to measure the normal forces on the two end faces of the artificial bird along the axial direction. The shock wave velocity of the artificial bird is calculated based on the time difference between the voltage signals generated by the first piezoelectric film sensor and the second piezoelectric film sensor. By directly measuring the shock wave velocity and the particle velocity after the wave, the device provided by this application avoids the disadvantage of the traditional method of indirectly calculating a certain physical quantity through the Hugoniot pressure relationship. Through precise real-time measurement, the dynamic response of the artificial bird when subjected to impact can be more accurately described, improving the accuracy and reliability of the data. Secondly, the device can achieve effective decoupling of device deformation and the dynamic behavior of the bird, thereby reducing the influence of the measurement device material size, stiffness characteristics, etc. on the bird's constitutive model. This advantage not only improves the universality of the test data, but also provides a more scientific and reliable foundation for subsequent simulation research and aircraft structural design, and has broad application prospects.

[0065] This application also provides a method for measuring the Hugoniot relationship parameters of artificial birds based on a Hopkinson bar, implemented using any of the aforementioned devices. This method involves conducting experiments on artificial birds of varying densities through test preparation, testing, measurement data processing, measurement data correction, validity analysis, and empirical indicator analysis. The method then fits the Hugoniot curves for these artificial birds, thereby obtaining the bird's constitutive model and parameters. This method, based on the theory of physical state and forward derivation of the equation of state and its parameters, prevents the bird's constitutive model and parameters from changing with operating conditions, thereby improving the universality of the test data. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0067] Figure 1 A side view of a device for measuring Hugoniot relationship parameters of an artificial bird based on a Hopkinson rod provided in this application;

[0068] Figure 2 for Figure 1 Front view of

[0069] Figure 3 It is the side view of the equivalent elastic modulus calibration test;

[0070] Figure 4 A flowchart of a method for measuring Hugoniot relationship parameters of an artificial bird based on a Hopkinson rod provided in this application;

[0071] Figure 5 Comparison chart of test normal force and simulation normal force calibrated for equivalent elastic modulus;

[0072] Figure 6 This is a comparison of the normal forces on the left and right end surfaces of the artificial bird before and after waveform correction;

[0073] Figure 7 Schematic diagram of the original voltage signals of the first piezoelectric film sensor and the second piezoelectric film sensor after calibration;

[0074] Figure 8 The density is 1.050g / cm 3 Scatter diagram of the post-wave particle velocity and shock wave velocity of the artificial bird;

[0075] Figure 9 The density is 0.990g / cm 3 Scatter diagram of the post-wave particle velocity and shock wave velocity of the artificial bird;

[0076] Figure 10 The density is 0.950g / cm 3 Scatter diagram of post-wave particle velocity and shock wave velocity of the artificial bird;

[0077] Figure 11 A comparison chart of the Hugoniot relationship curves fitted based on artificial birds of different densities.

[0078] Icons: 1. Air cannon barrel; 2. Impact rod; 3. Waveform shaper; 4. Incident rod; 5. Artificial bird; 6. Transmission rod; 7. Absorption rod; 8. Bracket; 9. Energy absorption device; 10. First strain gauge group; 11. Second strain gauge group; 12. Third strain gauge group; 13. First Wheatstone bridge box; 14. Second Wheatstone bridge box; 15. Third Wheatstone bridge box; 16. First piezoelectric film sensor; 17. Second piezoelectric film sensor; 18. Data logger; 19. DC regulated power supply; 20. Normal camera; 21. Oblique camera; 22. Calibration projectile; 23. Test at a strain rate of 2.70 / s Normal force; 24. Simulated normal force at a strain rate of 2.70 / s; 25. Test normal force at a strain rate of 5.09 / s; 26. Simulated normal force at a strain rate of 5.09 / s; 27. Normal force on the left end face of the artificial bird in one test without waveform correction; 28. Normal force on the right end face of the artificial bird in one test without waveform correction; 29. Normal force on the left end face of the artificial bird in one test with waveform correction; 30. Normal force on the right end face of the artificial bird in one test with waveform correction; 31. Original voltage signal of the first piezoelectric film sensor in one test; 32. Original voltage signal of the second piezoelectric film sensor in one test; 33. Density is 1.050g / cm 3 The Hugoniot relationship curve of the artificial bird is fitted; 34. The density is 0.990g / cm 3 Hugoniot curve fitted by artificial bird; 35. Density is 0.950g / cm 3 The Hugoniot relationship curve fitted by the artificial bird. DETAILED DESCRIPTION

[0079] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of this application, not all of them. Generally, the components of this application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0080] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application as claimed, but merely represents selected embodiments of the present application. It should be noted that, unless there is a conflict, the various features of the embodiments of the present application may be combined with each other, and the combined embodiments are still within the scope of protection of the present application.

[0081] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0082] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of this application is typically placed when in use. These terms are intended solely to facilitate the description of this application and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," "third," etc., are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0083] Furthermore, terms such as "horizontal" and "vertical" do not necessarily mean that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0084] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0085] In one aspect of the present application, a device for measuring Hugoniot relationship parameters of an artificial bird based on a Hopkinson rod is provided. Figure 1 and Figure 2As shown, it includes a bracket 8 fixed to the ground and a Hopkinson rod movably arranged on the bracket 8. Eight groups of support rods are arranged at intervals on the upper surface of the bracket 8, each group of support rods containing two support rods, one located on each side of the bracket 8. A roller shaft is mounted on each group of support rods, and two rollers are mounted on each roller shaft. The spacing between the two rollers on each roller shaft satisfies the support of the Hopkinson rod and does not interfere with the roller shaft. The Hopkinson rod includes an impact rod 2, an incident rod 4, and a transmission rod 6, which are arranged axially and sequentially on the rollers from left to right, with an artificial bird 5 clamped between the right end face of the incident rod 4 and the left end face of the transmission rod 6. The impact rod 2 is placed in the air cannon barrel 1, and the end of the incident rod 4 adjacent to the air cannon barrel 1 (i.e., the left end of the incident rod 4) is the projectile-facing end. Driven by an air cannon, the impact rod 2 strikes the projectile-facing end of the incident rod 4 in parallel, generating a shock wave. This shock wave is approximately a compressed square wave. The shock wave propagates through the incident rod 4 to the artificial bird 5. Part of the shock wave is reflected by the artificial bird 5 back to the incident rod 4, forming a reflected wave, and part of the shock wave is transmitted through the artificial bird 5 to the transmission rod 6, forming a transmitted wave. A waveform shaper 3 is affixed to the center of the projectile-facing end face of the incident rod 4. By adjusting the number of layers of this waveform shaper 3, the rise time of the loading wave can be precisely controlled, thereby optimizing the loading waveform. The waveform shaper 3 can be made of a material with negligible strength, such as vacuum sealant.

[0086] A first strain gauge group 10 and a second strain gauge group 11 arranged in an axially spaced relationship are adhered to the outer circumferential surface of the incident rod 4, and a third strain gauge group 12 is adhered to the outer circumferential surface of the transmission rod 6. The first strain gauge group 10, the second strain gauge group 11, and the third strain gauge group 12 generate voltage signals for measuring the strains of the shock wave, the reflected wave, and the transmitted wave, respectively. The post-wave particle velocity of the artificial bird 5 is calculated based on the strains of the shock wave, the reflected wave, and the transmitted wave.

[0087] A first piezoelectric film sensor 16 and a second piezoelectric film sensor 17 are respectively positioned in close proximity to the center of the clamping surface between the incident rod 4 and the transmissive rod 6. Specifically, the first piezoelectric film sensor 16 is positioned at the center of the right end face of the incident rod 4, and the second piezoelectric film sensor 17 is positioned at the center of the left end face of the transmissive rod 6. The voltage signals generated by the first and second piezoelectric film sensors 16, 17 are used to measure the normal forces acting on the axial end faces of the artificial bird 5. The shock wave velocity of the artificial bird 5 is calculated based on the time difference between the voltage signals generated by the first and second piezoelectric film sensors 16, 17.

[0088] It should be understood that when the compression properties of the impact rod 2, the incident rod 4 and the transmission rod 6 satisfy linear elasticity, the strain measured by the strain gauge group is linearly converted to the particle velocity and normal force on the left and right end surfaces of the artificial bird 5.

[0089] It should be noted that the voltage signals generated by the first strain gauge group 10, the second strain gauge group 11, and the third strain gauge group 12 can be processed according to the Wheatstone bridge conversion formula to obtain strain. The specific implementation method is as follows: according to the conventional method in the prior art, the first strain gauge group 10 is connected to the first Wheatstone bridge box 13; the second strain gauge group 11 is connected to the second Wheatstone bridge box 14; and the third strain gauge group 12 is connected to the third Wheatstone bridge box 15. The three Wheatstone bridges in the first Wheatstone bridge box 13, the second Wheatstone bridge box 14, and the third Wheatstone bridge box 15 all adopt the arm-to-arm measurement method in the prior art. When measuring with the piezoelectric film sensor, according to the conventional method in the prior art, the output ports of the first Wheatstone bridge box 13, the second Wheatstone bridge box 14, and the third Wheatstone bridge box 15 are connected to the input port of the data acquisition device 18. The first, second, and third Wheatstone bridge boxes 13, 14, and 15 are each connected to a DC regulated power supply 19, which supplies power to the three Wheatstone bridge boxes. The output ports of the first and second piezoelectric film sensors 16, 17 are connected to the input ports of a data acquisition device 18, as is conventional in the art. The data acquisition device 18 and the DC regulated power supply 19 are also grounded, as is conventional in the art.

[0090] In general, by directly measuring the shock wave velocity and the post-wave particle velocity, the device provided by this application avoids the drawback of the traditional method of indirectly calculating a certain physical quantity through the Hugoniot pressure relationship. Through precise real-time measurement, the dynamic response of the artificial bird 5 when it is impacted can be described more accurately, improving the accuracy and reliability of the data. Secondly, this device can achieve effective decoupling of the deformation of the device and the dynamic behavior of the bird, thereby reducing the influence of the material size and stiffness characteristics of the measuring device on the constitutive model of the bird. This advantage not only improves the universality of the test data, but also provides a more scientific and reliable basis for subsequent simulation research and aircraft structure design, and has broad application prospects.

[0091] Furthermore, the device also includes an energy absorbing device 9 fixedly arranged on the bracket 8, and the Hopkinson rod also includes an absorption rod 7 slidably arranged on the roller, the absorption rod 7 is axially arranged on the side of the transmission rod 6 away from the incident rod 4, and the energy absorbing device 9 is arranged on the side of the absorption rod 7 away from the transmission rod 6. The end of the absorption rod 7 adjacent to the energy absorbing device 9 (that is, the right end of the absorption rod 7) is the energy absorbing end, and the energy absorbing end is inserted into the energy absorbing device 9. The interior of the energy absorbing device 9 is filled with plasticine to effectively absorb the shock wave that is not reflected and transmitted (that is, the residual energy after the impact) and to limit the movement of the incident rod 4 and the transmission rod 6.

[0092] Furthermore, the impact rod 2, the incident rod 4, the transmission rod 6 and the absorption rod 7 are coaxially arranged and are all coaxial with the air cannon barrel 1. This coaxial arrangement design can effectively ensure the parallel collision between the impact rod 2 and the incident rod 4, thereby ensuring the accurate propagation direction of the shock wave, avoiding the angular deviation and irregular propagation that may occur during the impact process, and ensuring the high accuracy and reliability of the test measurement.

[0093] Furthermore, the impact rod 2, incident rod 4, transmission rod 6, and absorption rod 7 are all made of nylon PA66. The diameters of the impact rod 2, incident rod 4, transmission rod 6, and absorption rod 7 are the same, and are all 1.0 to 1.2 times the diameter of the circumscribed circle of the artificial bird 5 with the largest mass in the test outline. The lengths of the impact rod 2, incident rod 4, transmission rod 6, and absorption rod 7 are determined according to conventional methods in the prior art. Among them, the incident rod 4 and transmission rod 6 must be able to prevent the measured strain of the artificial bird 5 from superimposing the waveform of the shock wave and the reflected wave; the impact rod 2 should be able to prevent the measured strain of the artificial bird 5 from superimposing the waveform of the shock wave and the reflected wave, and at the same time, it is necessary to achieve stress balance during the loading process of the artificial bird 5; the absorption rod 7 depends on the length of the actual test bench and needs to ensure that the impact energy transmitted by the transmission rod 6 can be transferred to the energy absorption device 9 as much as possible to prevent the transmission rod 6 from generating large axial displacement during impact, so that the artificial bird 5 cannot undergo a uniform deformation process.

[0094] Furthermore, the device also includes a normal camera 20 and an oblique camera 21, positioned on the same side of the artificial bird 5. Specifically, the normal camera 20 is conventionally positioned in the gap between the incident rod 4 and the transmissive rod 6, and is located on the side of the artificial bird 5 perpendicular to the Hopkinson rod axis. Furthermore, the lens of the normal camera 20 is positioned horizontally, with its optical axis perpendicular to the axis of the Hopkinson rod, to capture the deformation process of the artificial bird 5 in a horizontal field of view. Similarly, the oblique camera 21 is conventionally positioned in the gap between the incident rod 4 and the transmissive rod 6, and is positioned on the same side of the artificial bird 5 as the normal camera 20. Furthermore, the lens of the oblique camera 21 is tilted, with its optical axis forming an acute angle with the axis of the Hopkinson rod, to capture the deformation process of the artificial bird 5 in an oblique field of view. Preferably, both the normal camera 20 and the oblique camera 21 are high-speed cameras.

[0095] Furthermore, the first strain gauge group 10 is located at 1 / 4 to 1 / 3 of the length of the incident rod 4 near the end of the impact rod 2, that is, the distance between the first strain gauge group 10 and the left end of the incident rod 4 is 1 / 4 to 1 / 3 of the length of the incident rod 4; the second strain gauge group 11 is located at 1 / 4 to 1 / 3 of the length of the incident rod 4 near the end of the transmission rod 6, that is, the distance between the second strain gauge group 11 and the right end of the incident rod 4 is 1 / 4 to 1 / 3 of the length of the incident rod 4; the third strain gauge group 12 is located at 1 / 4 to 1 / 3 of the length of the transmission rod 6 near the end of the incident rod 4, that is, the distance between the third strain gauge group 12 and the left end of the transmission rod 6 is 1 / 4 to 1 / 3 of the length of the transmission rod 6, thereby ensuring that the distance between the first strain gauge group 10 and the second strain gauge group 11 is greater than 1 / 3 of the length of the incident rod 4, so as to correct the stress wave dispersion and attenuation caused by the viscoelastic Hopkinson bar.

[0096] Furthermore, the first strain gauge group 10 includes two strain gauges axially symmetrically arranged on either side of the incident rod 4, the second strain gauge group 11 includes two strain gauges axially symmetrically arranged on either side of the incident rod 4, and the third strain gauge group 12 includes two strain gauges axially symmetrically arranged on either side of the transmission rod 6. The two strain gauges that make up the same strain gauge group are affixed to the outer circumference of the corresponding rod at the 3 o'clock and 9 o'clock directions, or the two strain gauges that make up the same strain gauge group are affixed to the outer circumference of the corresponding rod at the 6 o'clock and 12 o'clock directions, and the strain gauge sensitive grid of each strain gauge is arranged along the axis of the corresponding rod.

[0097] Another aspect of the present application provides a method for measuring Hugoniot relationship parameters of an artificial bird based on a Hopkinson rod, the method being implemented by any of the above-mentioned devices, such as Figure 4 As shown, the method includes:

[0098] S1, test preparation: determine the diameters of the impact rod 2, incident rod 4, transmission rod 6, and absorption rod 7 according to the diameter of the artificial bird 5; determine the lengths of the impact rod 2, incident rod 4, and transmission rod 6 according to the strain and stress requirements of the artificial bird 5; determine the length of the absorption rod 7 according to the actual length of the test bench.

[0099] S11, determine the diameters of the impact rod 2, the incident rod 4, the transmission rod 6, and the absorption rod 7 according to the diameter of the artificial bird 5:

[0100] The diameters of the four rods are determined based on the largest artificial bird (5) in the current experiment as specified in the test outline. The diameters of the four rods are equal, and are 1.0 to 1.2 times the diameter of the circumcircle of the largest artificial bird (5).

[0101] In this embodiment, the maximum bird mass specified in the test outline is 247.4g, the artificial bird 5 has a cylindrical shape with a length-to-diameter ratio of 3:10, and the maximum density of the artificial bird 5 is 1.050g / cm3. The 247.4g artificial bird 5 has a length of 30mm and a diameter of 100mm; the diameter of the four rods is 1 times the diameter of the 247.4g artificial bird 5, and the diameter of the four rods is determined to be 100mm.

[0102] S12, determining the lengths of the impact rod 2, the incident rod 4, and the transmission rod 6 according to the strain and stress requirements of the artificial bird 5:

[0103] S121, determine the lengths of the incident rod 4 and the transmission rod 6:

[0104] Assume that the incident rod 4 and the transmission rod 6 have the same preset lengths. L’ , the preset lengths of the incident rod 4 and the transmission rod 6 L’ The strain of the artificial bird 5 measured should be such that the waveform superposition of the shock wave and the reflected wave does not occur;

[0105] If the time required for the shock wave generated by the impact rod 2 hitting the incident rod 4 to reach the second strain gauge group 11, propagate along the incident rod 4 to the artificial bird 5, be reflected by the artificial bird 5 as a reflected wave, and propagate back along the incident rod 4 to the second strain gauge group 11 is greater than the width of the shock wave, then the preset lengths of the incident rod 4 and the transmission rod 6 are increased. L’ Determined as the length of the incident rod 4 and the transmission rod 6 L ;

[0106] S122, determine the length of the impact rod 2:

[0107] Preset length of striker rod 2 L B ’ The strain of the artificial bird 5 measured should not be superimposed by the shock wave and the reflected wave. At the same time, the preset length of the impact rod 2 L B’ It should be possible to achieve stress balance during the loading process of the artificial bird 5.

[0108] Impact rod 2 with speed V When the incident rod 4 is hit parallel to the incident rod 4, a shock wave is generated at the incident rod 4. The shock wave is an approximate compression square wave strain signal. The calculation formula for the width of the shock wave is:

[0109] (1)

[0110] in, ΔT is the width of the shock wave, C 0 is the one-dimensional elastic wave velocity of the impact rod 2, , E is the elastic modulus of the impact rod 2 and the incident rod 4, ρ 0 is the density of the impact rod 2, the incident rod 4, the transmission rod 6 and the absorption rod 7.

[0111] The calculation formula for the number of times the shock wave propagates back and forth in the artificial bird 5 is:

[0112] (2)

[0113] in, n is the number of round trips in artificial bird 5, C G is the one-dimensional elastic wave speed of artificial bird 5, which is about 1500m / s, L G is the length of the artificial bird 5.

[0114] If the time required for the shock wave generated by the impact of the impact rod 2 on the incident rod 4 to reach the second strain gauge group 11, propagate along the incident rod 4 to the artificial bird 5, be reflected by the artificial bird 5 as a reflected wave, and propagate back to the second strain gauge group 11 along the incident rod 4 is greater than the width of the shock wave, and the number of times the shock wave propagates back and forth in the artificial bird 5 is greater than 3, so that stress balance is achieved during the loading process of the artificial bird 5, then the preset length of the impact rod 2 is changed to L B ’ Determined as the length of the striker rod 2 L B .

[0115] S13, determine the length of the absorbing rod 7:

[0116] Length of the absorption rod 7 L A The length of the actual test bench is determined by the absorption rod 7, which is used as a carrier to transfer the impact energy to the energy absorption device 9. L AIt is necessary to ensure that the impact energy transmitted by the transmission rod 6 can be transmitted to the energy absorbing device 9 as much as possible to prevent the transmission rod 6 from generating a large axial displacement during the collision, so that the artificial bird 5 cannot undergo a uniform deformation process.

[0117] In this embodiment, the preset L’ =3000mm, L B ’ =400mm. The impact rod 2, incident rod 4, transmission rod 6 and absorption rod 7 are all made of nylon PA66, whose one-dimensional elastic wave speed is 1800m / s. L B ’ =400mm, calculated by formula (1) ΔT =0.44ms. When the shock wave reaches the second strain gauge group 11, propagates along the axial direction of the incident rod 4 to the right end face of the incident rod 4, is reflected by the artificial bird 5 as a reflected wave (wherein the reflected wave is a tensile wave) and propagates back to the second strain gauge group 11, the total propagation distance of the wave is 2000mm, and the propagation time is 1.11ms, which is greater than the width of the shock wave. The shock wave will not overlap with the reflected tensile wave, which makes the test data analysis difficult. And it is calculated by formula (2) n =11, which is greater than 3, indicating that the stress in the artificial bird 5 can be balanced. Therefore, the lengths of the incident rod 4 and the transmission rod 6 are set. L The length of the impact rod 2 is 3000mm L B 400mm is reasonable.

[0118] After determining the diameter and parameters, the impact rod 2 is arranged in the air cannon barrel 1, and the incident rod 4, transmission rod 6 and absorption rod 7 are arranged on the bracket 8 in sequence, so that the impact rod 2, incident rod 4, transmission rod 6 and absorption rod 7 are all coaxial with the air cannon barrel 1, and the projectile-facing end face of the incident rod 4 is located at one end close to the air cannon barrel 1, and the energy-absorbing end of the absorption rod 7 is close to the energy-absorbing device 9.

[0119] S2, measurement device calibration: calibrate the first piezoelectric film sensor 16 and the second piezoelectric film sensor 17; determine the relationship between the pixel coordinates in the field of view of the normal camera 20 and the oblique camera 21 and the world coordinates; calibrate the equivalent elastic modulus of the impact rod 2, the incident rod 4, the transmission rod 6 and the absorption rod 7 based on the impact test of the calibration bullet 22 E’ .

[0120] S21, calibrating the first piezoelectric film sensor 16 and the second piezoelectric film sensor 17:

[0121] When the artificial bird 5 is not clamped between the incident rod 4 and the transmission rod 6, and the right end face of the incident rod 4 is tightly fitted with the left end face of the transmission rod 6, the impact rod 2 impacts the incident rod 4 in parallel. By converting the voltage signals collected by the first strain gauge group 10, the second strain gauge group 11 and the third strain gauge group 12 into stress signals, the relationship between the stress signals and the voltage signals of the first piezoelectric film sensor 16 and the second piezoelectric film sensor 17 is obtained respectively, and the calibration curve is determined by fitting the relationship. Figure 7 As shown, the original voltage signal of the piezoelectric film sensor assembly after calibration is displayed. The peak value of the voltage signal of the first piezoelectric film sensor 16 is greater than the peak value of the voltage signal of the second piezoelectric film sensor 17, indicating that the forces on the left and right end surfaces of the artificial bird 5 are not equal.

[0122] S22, determining the relationship between the pixel coordinates in the field of view of the normal camera 20 and the oblique camera 21 and the world coordinates:

[0123] A calibration ruler is placed at the location where the incident rod 4 and the transmission rod 6 clamp the artificial bird 5, and the calibration ruler is simultaneously located in the horizontal field of view captured by the normal camera 20 and the oblique field of view captured by the oblique camera 21. The pixel coordinate differences at both ends of the calibration ruler along the axis of the artificial bird 5 are measured in the horizontal field of view and the oblique field of view, respectively, to obtain the relationship between the pixel coordinates in the axis direction of the artificial bird 5 in the horizontal field of view captured by the normal camera 20 and the world coordinates, as well as the relationship between the pixel coordinates in the axis direction of the artificial bird 5 in the oblique field of view captured by the oblique camera 21 and the world coordinates.

[0124] S23, based on the impact test of the calibration bullet 22, calibrate the equivalent elastic modulus of the impact rod 2, the incident rod 4, the transmission rod 6 and the absorption rod 7 E’ :

[0125] Since the impact rod 2, incident rod 4, transmission rod 6 and absorption rod 7 are all made of nylon PA66, the equivalent elastic modulus calibrated by the incident rod 4 is E’ As Figure 3 As shown, the impact rod 2, transmission rod 6 and absorption rod 7 in S1 are removed from the bracket 8, and a cylindrical nylon PA66 calibration bullet 22 is used to impact the projectile end surface of the incident rod 4 at different speeds.

[0126] A finite element simulation model of the impact of a calibration bullet 22 made of nylon PA66 on the incident rod 4 is established, and the elastic modulus of nylon PA66 used in the incident rod 4 and the calibration bullet 22 is set to be E Linear elastic material; and through iteration, the peak deviation between the simulated normal force and the test normal force is minimized, and the elastic modulus after iterative optimization is determined as the equivalent elastic modulus of the impact rod 2, the incident rod 4, the transmission rod 6 and the absorption rod 7 E’ , as the basis for measurement data processing.

[0127] In this embodiment, the calibration bullet 22 has a length of 400 mm and a diameter of 100 mm. The calibration bullet 22 impacts the projectile end face of the incident rod 4 at strain rates of 2.70 / s and 3.09 / s, respectively, and the normal force amplitude generated is 0 to 85 kN. Based on the elastic modulus of nylon PA66 after iterative optimization, the simulated normal force on the projectile end face of the incident rod 4 at strain rates of 2.70 / s and 3.09 / s is obtained. Figure 5 As shown in the figure, when the strain rate is 2.70 / s, the peak error between the simulated normal force 24 and the test normal force 23 is less than 10%, which meets the test outline requirements; when the strain rate is 3.09 / s, the peak error between the simulated normal force 26 and the test normal force 25 is less than 10%, which meets the test outline requirements; the elastic modulus of the nylon PA66 material used in the incident rod 4 in the finite element simulation is used as the equivalent elastic modulus of the impact rod 2, the incident rod 4, the transmission rod 6 and the absorption rod 7 E’ .

[0128] S3, test: drive the impact rod 2 to impact the incident rod 4 to generate a shock wave, the shock wave propagates through the incident rod 4 to the artificial bird 5, part of the shock wave is reflected by the artificial bird 5 to the incident rod 4 to form a reflected wave, and part of the shock wave is transmitted through the artificial bird 5 to the transmission rod 6 to form a transmitted wave; the first strain gauge group 10, the second strain gauge group 11 and the third strain gauge group 12 are used to measure the strains of the shock wave, the reflected wave and the transmitted wave respectively; the first piezoelectric film sensor 16 and the second piezoelectric film sensor 17 are used to measure the normal force of the two end faces of the artificial bird 5 along the axial direction respectively.

[0129] Based on the experimental preparation of S1, an impact test was carried out. The impact rod 2 was launched through the air cannon. The high-pressure air pushed the impact rod 2 to accelerate axially along the air cannon barrel 1. The impact rod 2 hit the projectile end, generating an approximate compression square wave strain signal (i.e., shock wave) on the incident rod 4. This elastic compression wave was transmitted to the interface between the incident rod 4 and the artificial bird 5. Part of the wave was transmitted to the artificial bird 5, and then continued to be transmitted from the artificial bird 5 to the transmission rod 6 to obtain the transmitted wave. Part of the wave was reflected back to the incident rod 4 in the form of a tensile wave, i.e., the reflected wave.

[0130] When the shock wave passes through the first and second strain gauge groups 10 and 11, the two pairs of strain gauges are compressed, and the first and second Wheatstone bridge boxes 13 and 14 generate voltage signals, which are recorded by the data collector 18. A portion of the shock wave is reflected back to the incident rod 4 as a tensile wave. As it propagates back to the second and first strain gauge groups 11 and 10, the two pairs of strain gauges are stretched, and the second and first Wheatstone bridge boxes 14 and 13 generate voltage signals, which are recorded by the data collector 18. Another portion of the shock wave continues from the artificial bird 5 to the transmission rod 6. As it passes through the third strain gauge group 12, one pair of strain gauges is compressed, and the third Wheatstone bridge box 15 generates a voltage signal, which is recorded by the data collector 18. The voltage signals measured by the first, second, and third strain gauge groups 10, 11, and 12 are processed according to the Wheatstone bridge conversion formula to obtain strain.

[0131] When the shock wave reaches the interface between incident rod 4 and artificial bird 5, first piezoelectric film sensor 16 generates a voltage signal, which is recorded by data collector 18. A portion of the shock wave reaches artificial bird 5, and then continues from artificial bird 5 to the interface between artificial bird 5 and transmission rod 6. Second piezoelectric film sensor 17 generates a voltage signal, which is also recorded by data collector 18.

[0132] S4, measurement data processing: calculate the post-wave particle velocity of the artificial bird 5 based on the strain of the shock wave, reflected wave and transmitted wave; calculate the shock wave velocity of the artificial bird 5 based on the time difference of the voltage signal generated when measuring the normal force on the two end surfaces of the artificial bird 5 along the axial direction.

[0133] S41, calculate the post-wave particle velocity of the artificial bird 5 based on the strain of the shock wave, the reflected wave, and the transmitted wave:

[0134] The calculation formula for the speed of the artificial bird 5 along the axial end faces (i.e., the left and right end faces) is:

[0135] (3)

[0136] (4)

[0137] in, V input and V output are the speeds of the two end faces of the artificial bird 5 along the axial direction, C 0 is the one-dimensional elastic wave velocity of the impact rod 2, , E is the elastic modulus of the striking rod 2, where E It can also be replaced by the equivalent elastic modulusE’ , ρ 0 is the density of impact rod 2, ε i is the strain of the shock wave, ε r is the strain of the reflected wave, ε t is the strain of the transmitted wave.

[0138] Since the velocity of the left end face of the artificial bird 5 is greater than the velocity of the right end face of the artificial bird 5, the length of the artificial bird 5 will shorten over time during the loading process. The calculation formula for the strain rate of the artificial bird 5 is:

[0139] (5)

[0140] in, is the strain rate of artificial bird 5.

[0141] Therefore, the calculation formula for the particle velocity after the wave of artificial bird 5 is:

[0142] (6)

[0143] in, V p is the post-wave particle velocity of artificial bird 5.

[0144] S42, calculating the shock wave velocity of the artificial bird 5 according to the time difference of the voltage signals generated when measuring the normal forces on the two end surfaces of the artificial bird 5 along the axial direction:

[0145] When the shock wave reaches the left and right ends of the artificial bird 5, the first piezoelectric film sensor 16 and the second piezoelectric film sensor 17 start to generate voltage signals in sequence. The time when the two piezoelectric film sensors start to generate voltage signals is recorded. The shock wave velocity of the artificial bird 5 is calculated as follows:

[0146] (7)

[0147] in, V s is the shock wave velocity of artificial bird 5, t input is the time when the first piezoelectric film sensor 16 starts to generate a voltage signal, t output is the time when the second piezoelectric film sensor 17 starts to generate a voltage signal.

[0148] S5, measurement data correction and validity analysis: Correct the strains measured by the first strain gauge group 10, the second strain gauge group 11, and the third strain gauge group 12 through Fourier transform; calculate the corrected normal forces of the two end surfaces of the artificial bird 5 along the axial direction based on the corrected strains, and compare the corrected normal forces of the two end surfaces of the artificial bird 5 along the axial direction with the normal forces measured by the first piezoelectric film sensor 16 and the second piezoelectric film sensor 17 to determine the validity of the measurement data;

[0149] S51, correcting the strains measured by the first strain gauge group 10, the second strain gauge group 11, and the third strain gauge group 12 by Fourier transform:

[0150] Since the impact rod 2, incident rod 4, transmission rod 6, and absorption rod 7 are all made of nylon PA66, a polymer with viscoelastic properties, wave propagation in the viscoelastic rods is diffuse. Furthermore, wave attenuation occurs due to material damping, necessitating waveform correction.

[0151] The specific method for waveform correction is consistent with that of S23. The strains measured by the first strain gauge group 10 and the second strain gauge group 11 are obtained by the test method of S23. The strains measured by the first strain gauge group 10 and the second strain gauge group 11 are converted from the time domain to the frequency domain through Fourier transform. The one-dimensional wave equation of the Hopkinson bar becomes:

[0152] (8)

[0153] The general solution of formula (8) is:

[0154] (9)

[0155] in, is the angular frequency, x is any length of the Hopkinson bar along the axial direction, is the strain in frequency domain analysis, function and is the strain in the Hopkinson bar x The Fourier form of axial propagation, the complex exponential function and The modulus and phase reflect the shock wave attenuation and propagation, γ is the propagation coefficient, and attenuation coefficient and phase velocity The calculation formula is:

[0156] (10)

[0157] in, i is the imaginary number in the complex function, the attenuation coefficient is a positive even function, wave number is an odd function.

[0158] Therefore, the Fourier transform of the axial particle velocity and normal force at any length of the Hopkinson rod is:

[0159] (11)

[0160] (12)

[0161] in, is the axial particle velocity at any length of the Hopkinson rod in frequency domain analysis, is the normal force of the Hopkinson bar at any length in the frequency domain analysis, A is the cross-sectional area of the incident rod 4 and the transmission rod 6.

[0162] Since the right end of the incident rod 4 is a free end face, the normal force is equal to zero. The calculation formula of the normal force on the right end face is:

[0163] (13)

[0164] It is assumed that the incident rod 4 is at the projectile end x =0, then the right end face of the incident rod 4 x =L.

[0165] Therefore, the transfer function The calculation formula is:

[0166] (14)

[0167] in, is the transfer function.

[0168] From formula (14), we can see that the attenuation coefficient can be calculated from the amplitude of the transfer function, and the wave number can be calculated from the phase of the transfer function.

[0169] The attenuation coefficient is calculated from the strain of the shock wave measured by the first strain gauge group 10. and wave number The attenuation coefficient is calculated from the strain of the reflected wave measured by the second strain gauge group 11. and wave number ;Pick and The average value of the attenuation coefficient ,Pick and The average value of the wave velocity ,Will and By substituting the Fourier transform of the axial particle velocity and normal force at any length of the Hopkinson bar, the frequency domain form of the corrected velocity and normal force of the two end surfaces of the artificial bird 5 along the axial direction is obtained. Then, through the inverse Fourier transform, the time domain form is obtained to complete the correction of the strains measured by the first strain gauge group 10, the second strain gauge group 11 and the third strain gauge group 12.

[0170] The normal forces on both end faces of the artificial bird 5 along the axial direction are obtained from the strains measured by the first strain gauge group 10, the second strain gauge group 11, and the third strain gauge group 12. The calculation formula for the normal force on the left end face of the artificial bird 5 is:

[0171] (15)

[0172] The calculation formula of the normal force on the right end face of the artificial bird 5 is:

[0173] (16)

[0174] in, F input and F output are the normal forces on the left and right end faces of the artificial bird 5, respectively. Here, the elastic modulus E It can also be replaced by the equivalent elastic modulus E’ .

[0175] like Figure 6 As shown, the normal forces on the left and right end surfaces of the artificial bird 5 differ greatly before waveform correction is performed. After waveform correction is performed, the difference between the two decreases, indicating that waveform correction is an important step that cannot be ignored.

[0176] S52, calculating the corrected normal forces on both axial end surfaces of the artificial bird 5 based on the corrected strain, and comparing the corrected normal forces on both axial end surfaces of the artificial bird 5 with the normal forces on both axial end surfaces of the artificial bird 5 measured by the first piezoelectric film sensor 16 and the second piezoelectric film sensor 17 to determine the validity of the measurement data:

[0177] The corrected strains of the first strain gauge group 10, the second strain gauge group 11 and the third strain gauge group 12 are obtained by S51, and the corrected peak values of the normal forces on both end surfaces of the artificial bird 5 along the axial direction are calculated. and , and The time of occurrence is and ;

[0178] The first piezoelectric film sensor 16 and the second piezoelectric film sensor 17 respectively measure the peak values of the normal forces on the two end surfaces of the artificial bird 5 along the axial direction. and , and The time of occurrence is and ;

[0179] The validity judgment formula of the measurement data of the first piezoelectric film sensor 16 is:

[0180] (17)

[0181] If formula (17) is satisfied, the measurement data of the first piezoelectric film sensor 16 is determined to be valid;

[0182] The validity judgment formula of the measurement data of the second piezoelectric film sensor 17 is:

[0183] (18)

[0184] If formula (18) is satisfied, it is determined that the measurement data of the second piezoelectric film sensor 17 is valid.

[0185] S6, empirical indicator analysis: Repeat the test preparation for artificial birds 5 with different densities to measure data correction and validity analysis, fit the Hugoniot curves of artificial birds 5 with different densities regarding the post-wave particle velocity and shock wave velocity, compare the slopes and intercepts of the Hugoniot curves of artificial birds 5 with different densities, and determine the influence of the density of artificial birds 5 on the mechanical behavior of artificial birds 5.

[0186] According to the test outline, the density is 1.050g / cm 3 、0.990g / cm 3 and 0.950g / cm 3 The post-wave particle velocity and shock wave velocity of 12 groups of artificial birds 5 at strain rates of 666.7 / s~2000.0 / s. Figures 8 to 10 As the particle velocity behind the wave increases, the shock wave velocity basically increases linearly. Figure 11 Based on the density of 1.050g / cm 3 、0.990g / cm 3 and 0.950g / cm 3 The Hugoniot curve fitted by artificial bird 5 is as follows: Figure 11 As shown, as the density of the artificial bird 5 decreases, the intercept of the Hugoniot curve of the artificial bird 5 decreases, and the slope remains basically constant, indicating that the mechanical behaviors of artificial birds 5 with different densities are different.

[0187] This completes the measurement of the particle velocity and shock wave velocity after the artificial bird 5 wave using the Hopkinson bar-based Hugoniot relation parameter measurement device. This method, through experimental preparation, testing, measurement data processing, measurement data correction and validity analysis, and empirical indicator analysis, conducts tests on artificial birds 5 of varying densities, fitting Hugoniot curves for these densities and subsequently obtaining the bird's constitutive model and parameters. This method, based on the theory of physical state and forward derivation of the equation of state and its parameters, prevents the bird's constitutive model and parameters from changing with operating conditions, thereby improving the universality of the experimental data.

[0188] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A device for measuring Hugoniot relationship parameters of an artificial bird based on a Hopkinson rod, characterized in that: The invention comprises a bracket (8) and a Hopkinson rod movably arranged on the bracket (8), wherein the Hopkinson rod comprises an impact rod (2), an incident rod (4) and a transmission rod (6) arranged in sequence along the axial direction, and a gap for clamping an artificial bird (5) is provided between the incident rod (4) and the transmission rod (6), wherein the impact rod (2) is driven to impact the incident rod (4) to generate a shock wave, wherein the shock wave propagates to the artificial bird (5) via the incident rod (4), a part of the shock wave is reflected by the artificial bird (5) to the incident rod (4) to form a reflected wave, and a part of the shock wave is transmitted by the artificial bird (5) to the transmission rod (6) to form a transmitted wave; A first strain gauge group (10) and a second strain gauge group (11) arranged at intervals along the axial direction are provided on the periphery of the incident rod (4), and a third strain gauge group (12) is provided on the periphery of the transmission rod (6), wherein the first strain gauge group (10), the second strain gauge group (11) and the third strain gauge group (12) generate voltage signals for measuring the strains of the shock wave, the reflected wave and the transmitted wave respectively, and the post-wave particle velocity of the artificial bird (5) is calculated based on the strains of the shock wave, the reflected wave and the transmitted wave; A first piezoelectric film sensor (16) and a second piezoelectric film sensor (17) are respectively provided on the clamping surfaces of the incident rod (4) and the transmission rod (6); the first piezoelectric film sensor (16) and the second piezoelectric film sensor (17) generate voltage signals for respectively measuring the normal forces of the two end faces of the artificial bird (5) along the axial direction; and the shock wave velocity of the artificial bird (5) is calculated based on the time difference between the voltage signals generated by the first piezoelectric film sensor (16) and the second piezoelectric film sensor (17).

2. The device according to claim 1, characterized in that The device further comprises an energy absorbing device (9) fixedly arranged on the bracket (8), and the Hopkinson rod further comprises an absorption rod (7), wherein the absorption rod (7) is axially arranged on a side of the transmission rod (6) away from the incident rod (4), and an end of the absorption rod (7) away from the transmission rod (6) is inserted into the energy absorbing device (9) to absorb the shock wave that is not reflected and transmitted.

3. The device according to claim 1 or 2, characterized in that The impact rod (2), the incident rod (4) and the transmission rod (6) are coaxially arranged.

4. The device according to claim 1 or 2, characterized in that The device further comprises a normal camera (20) and an oblique camera (21) arranged on the same side of the artificial bird (5), wherein the optical axis of the normal camera (20) is perpendicular to the axis of the Hopkinson rod, and the angle between the optical axis of the oblique camera (21) and the axis of the Hopkinson rod is an acute angle, so as to capture the deformation process of the artificial bird (5) from different fields of view.

5. The device according to claim 1 or 2, characterized in that The distance between the first strain gauge group (10) and the end of the incident rod (4) close to the impact rod (2) is 1 / 4 to 1 / 3 of the length of the incident rod (4), the distance between the second strain gauge group (11) and the end of the incident rod (4) close to the transmission rod (6) is 1 / 4 to 1 / 3 of the length of the incident rod (4), and the distance between the third strain gauge group (12) and the end of the transmission rod (6) close to the incident rod (4) is 1 / 4 to 1 / 3 of the length of the transmission rod (6).

6. The device according to claim 1 or 2, characterized in that The first strain gauge group (10) includes at least two strain gauges symmetrically arranged along the axial direction on both sides of the incident rod (4), the second strain gauge group (11) includes at least two strain gauges symmetrically arranged along the axial direction on both sides of the incident rod (4), and the third strain gauge group (12) includes at least two strain gauges symmetrically arranged along the axial direction on both sides of the transmission rod (6).

7. A method for measuring Hugoniot relationship parameters of an artificial bird based on a Hopkinson rod, characterized in that: The method is implemented by the device according to any one of claims 1 to 6, and the method includes: Test preparation: Determine the diameters of the impact rod (2), the incident rod (4), and the transmission rod (6) according to the diameter of the artificial bird (5); determine the lengths of the impact rod (2), the incident rod (4), and the transmission rod (6) according to the strain and stress requirements of the artificial bird (5); Test: driving the impact rod (2) to impact the incident rod (4) to generate a shock wave, part of the shock wave is reflected by the artificial bird (5) to form a reflected wave, and part of the shock wave is transmitted through the artificial bird (5) to form a transmitted wave; measuring the strains of the shock wave, the reflected wave, and the transmitted wave respectively; measuring the normal forces of the two end faces of the artificial bird (5) along the axial direction respectively; Measurement data processing: The post-wave particle velocity of the artificial bird (5) is calculated based on the strain of the shock wave, the reflected wave and the transmitted wave. The calculation formula is: in, V p is the post-wave particle velocity of the artificial bird (5), C 0 is the one-dimensional elastic wave velocity of the impact rod (2), , E is the elastic modulus of the impact rod (2), ρ 0 is the density of the impact rod (2), ε i is the strain of the shock wave, ε r is the strain of the reflected wave, ε t is the strain of the transmitted wave; The shock wave velocity of the artificial bird (5) is calculated based on the time difference of the voltage signal generated when measuring the normal force on the two end faces of the artificial bird (5) along the axial direction. The calculation formula is: in, V s is the shock wave velocity of the artificial bird (5), L G is the length of the artificial bird (5), t input is the time when the first piezoelectric film sensor (16) starts to generate a voltage signal, t output The time when the second piezoelectric film sensor (17) starts to generate a voltage signal; Measurement data correction and validity analysis: correcting the strains measured by the first strain gauge group (10), the second strain gauge group (11), and the third strain gauge group (12) by Fourier transform; calculating the corrected normal forces of the artificial bird (5) along the axial end faces based on the corrected strains, and comparing the corrected normal forces of the artificial bird (5) along the axial end faces with the normal forces measured by the first piezoelectric film sensor (16) and the second piezoelectric film sensor (17) to determine the validity of the measurement data; Empirical index analysis: Repeat the test preparation to the measurement data correction and validity analysis for the artificial birds (5) of different densities, fit the Hugoniot curves of the artificial birds (5) of different densities with respect to the post-wave particle velocity and the shock wave velocity, compare the slopes and intercepts of the Hugoniot curves of the artificial birds (5) of different densities, and judge the influence of the density of the artificial bird (5) on the mechanical behavior of the artificial bird (5).

8. The method according to claim 7, characterized in that In the test preparation, determining the lengths of the impact rod (2), the incident rod (4), and the transmission rod (6) according to the strain and stress requirements of the artificial bird (5) includes: Determine the lengths of the incident rod (4) and the transmission rod (6): Assume that the incident rod (4) and the transmission rod (6) have the same preset lengths, both L’ , the preset lengths of the incident rod (4) and the transmission rod (6) L’ It should be possible to prevent the strain of the artificial bird (5) obtained by measurement from the waveform superposition of the shock wave and the reflected wave; If the time required from the shock wave reaching the second strain gauge group (11) to the reflected wave propagating along the incident rod (4) back to the second strain gauge group (11) is greater than the width of the shock wave, the preset lengths of the incident rod (4) and the transmission rod (6) are increased. L’ Determined as the length of the incident rod (4) and the transmission rod (6) L ; Determine the length of the striker rod (2): The preset length of the impact rod (2) L B ’ The strain of the artificial bird (5) obtained by measurement should not have the waveform superposition of the shock wave and the reflected wave, and at the same time, the preset length of the impact rod (2) L B ’ It should be possible to achieve stress balance during the loading process of the artificial bird (5); The calculation formula of the width of the shock wave is: in, ΔT is the width of the shock wave, C 0 is the one-dimensional elastic wave velocity of the impact rod (2), , E is the elastic modulus of the impact rod (2) and the incident rod (4), ρ 0 is the density of the impact rod (2) and the incident rod (4); The calculation formula for the number of times the shock wave propagates back and forth in the artificial bird (5) is: in, n is the number of round trips of the artificial bird (5), C G is the one-dimensional elastic wave velocity of the artificial bird (5), L G is the length of the artificial bird (5); If the time required from the shock wave reaching the second strain gauge group (11) to the reflected wave propagating along the incident rod (4) back to the second strain gauge group (11) is greater than the width of the shock wave, and the number of times the shock wave propagates back and forth in the artificial bird (5) is greater than 3, so that stress balance is achieved during the loading process of the artificial bird (5), then the preset length of the impact rod (2) is increased. L B ’ Determined as the length of the striking rod (2) L B .

9. The method according to claim 7 or 8, characterized in that In the measurement data correction and validity analysis, the correction of the strains measured by the first strain gauge group (10), the second strain gauge group (11) and the third strain gauge group (12) by Fourier transform includes: converting the strains measured by the first strain gauge group (10) and the second strain gauge group (11) from the time domain to the frequency domain by Fourier transform, and then the one-dimensional wave equation of the Hopkinson bar becomes: The general solution to this one-dimensional wave equation is: in, is the angular frequency, x is any length of the Hopkinson bar along the axial direction, is the strain in frequency domain analysis, function and is the strain in the Hopkinson bar x The Fourier form of axial propagation, the complex exponential function and The modulus and phase reflect the shock wave attenuation and propagation, γ is the propagation coefficient, and attenuation coefficient and phase velocity Related, , i is the imaginary number in the complex function, the attenuation coefficient is a positive even function, wave number is an odd function; Therefore, the Fourier transform of the axial particle velocity and normal force at any length of the Hopkinson bar is: in, is the axial particle velocity of the Hopkinson rod at any length in the frequency domain analysis, is the normal force of the Hopkinson bar at any length in the frequency domain analysis, A is the cross-sectional area of the incident rod (4) and the transmission rod (6); The attenuation coefficient is calculated by measuring the strain of the shock wave by the first strain gauge group (10). and wave number The attenuation coefficient is calculated from the strain of the reflected wave measured by the second strain gauge group (11) and wave number ;Pick and The average value of the attenuation coefficient ,Pick and The average value of the wave velocity ,Will and The Fourier transform of the axial particle velocity and normal force at any length of the Hopkinson rod is brought in to obtain the frequency domain form of the corrected velocity and normal force of the two end faces of the artificial bird (5) along the axial direction. Then, the time domain form is obtained through the inverse Fourier transform to complete the correction of the strains measured by the first strain gauge group (10), the second strain gauge group (11) and the third strain gauge group (12).

10. The method according to claim 9, characterized in that In the measurement data correction and validity analysis, the correction of the normal force of the artificial bird (5) along the axial end faces is calculated based on the corrected strain, and the correction of the normal force of the artificial bird (5) along the axial end faces is compared with the normal force measured by the first piezoelectric film sensor (16) and the second piezoelectric film sensor (17) to determine the validity of the measurement data, including: calculating the corrected peak values of the normal force of the artificial bird (5) along the axial end faces based on the corrected strains of the first strain gauge group (10), the second strain gauge group (11) and the third strain gauge group (12); and , and The time of occurrence is and ; The normal force peak values of the two end surfaces of the artificial bird (5) along the axial direction are respectively measured according to the first piezoelectric film sensor (16) and the second piezoelectric film sensor (17). and , and The time of occurrence is and ; The validity judgment formula of the measurement data of the first piezoelectric film sensor (16) is: If satisfied and The difference is less than 5%, and and If the difference is less than 5%, it is determined that the measurement data of the first piezoelectric film sensor (16) is valid; The validity judgment formula of the measurement data of the second piezoelectric film sensor (17) is: If satisfied and The difference is less than 5%, and and If the difference is less than 5%, it is determined that the measurement data of the second piezoelectric film sensor (17) is valid.

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