Measurement device and method for free surface velocity history under impact loading of corroded metals

Abstract

The present invention discloses a measuring device and method for the free surface velocity history under impact loading of corroded metals, comprising a terahertz velocity measurement mainframe, a terahertz focusing mirror and an oscilloscope; the terahertz velocity measurement mainframe is arranged directly in front of the free surface of the corroded metal material, and is used for emitting continuous terahertz waves to the free surface of the corroded metal material and recovering the terahertz waves reflected by the free surface of the corroded metal material, and generating interference signals; the terahertz focusing mirror is arranged between the terahertz velocity measurement mainframe and the free surface of the corroded metal material, and is used for focusing the continuous terahertz waves onto the free surface of the corroded metal material, and collecting and transmitting the terahertz waves reflected by the free surface of the corroded metal material to the terahertz velocity measurement mainframe; the oscilloscope is used for collecting and recording the interference signals generated by the terahertz velocity measurement mainframe. The present invention utilizes the high penetrability of terahertz waves to microspray particles to penetrate through the dense microspray particles and irradiate the surface of the free surface of the metal material, so as to realize the measurement of the free surface velocity history of the metal material.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion metal impact loading dynamics. Specifically, it relates to a measuring device and method for the free surface velocity history under corrosion metal impact loading. Background Art

[0002] When a metal material with surface corrosion is under shock wave loading, some material particles will be ejected from the free surface, and their velocity is greater than the overall movement velocity of the metal material free surface. This belongs to a typical micro-material ejection process and is an important research content in the study of detonation and shock wave physics. The characteristics of the micro-material ejection process mainly include characteristics such as the metal free surface velocity history, micro-material velocity / particle size / density, etc. Each parameter has important value for the study of the impact dynamics response characteristics of materials. Among them, the velocity history of the metal free surface reflects the overall response characteristics of the metal under impact loading, which is of great significance for understanding the mechanical response and failure behavior of corrosion metal materials under extreme conditions such as high-speed collision or impact. At the same time, it has important engineering application value and is an important experimental parameter in impact dynamics research.

[0003] Currently, in the aspect of velocity measurement during the corrosion metal impact loading process, the mainly adopted technology is Photonic Doppler Velocimetry (abbreviated as PDV), and generally infrared laser (1.55μm) (a small number use visible laser) is used as the light source. However, during the micro-ejection process, when the amount of micro-ejected material is relatively high, most of the laser will be reflected or blocked by the micro-material particles, making the laser unable to irradiate the metal material free surface, and it is difficult to measure the free surface velocity history of the corrosion metal material under impact loading. Although the light / electrical probe technology for obtaining the impact time of the material free surface can indirectly measure the free surface velocity, due to the possibility that the micro-ejected material particles may cause the probe to conduct in advance, it is also difficult to obtain the free surface velocity history during the micro-ejection process. Therefore, there is currently a lack of an effective measurement method for the free surface velocity history of corrosion metal materials under impact loading.

[0004] In view of this, the present application is specifically proposed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that most of the laser light in the existing photon Doppler velocimetry technology will be reflected or blocked by micro-matter particles, making it impossible for the laser to irradiate the free surface of the metal material, and it is difficult to measure the velocity history of the free surface of the corroded metal material under shock loading. The purpose is to provide a device and method for measuring the velocity history of the free surface of a corroded metal under shock loading. By using the high penetrability of terahertz waves to microspray particles, it is possible to penetrate the dense microspray particles and irradiate the free surface of the metal material, and use the terahertz wave Doppler interferometry technology to measure the velocity history of the free surface of the metal material, filling the data gap of the free surface velocity in the current research on the shock loading process of corroded metal materials.

[0006] The present invention is realized through the following technical solutions:

[0007] A device for measuring the velocity history of the free surface of a corroded metal under shock loading, comprising a terahertz velocimeter host, a terahertz focusing mirror, and an oscilloscope; the terahertz velocimeter host is arranged directly in front of the free surface of the corroded metal material, and is used for emitting continuous terahertz waves to the free surface of the corroded metal material and recovering the terahertz waves reflected by the free surface of the corroded metal material, and generating an interference signal; the terahertz focusing mirror is arranged between the terahertz velocimeter host and the free surface of the corroded metal material, and is used for focusing the continuous terahertz waves emitted by the terahertz velocimeter host onto the free surface of the corroded metal material, and collecting and transmitting the terahertz waves reflected by the free surface of the corroded metal material to the terahertz velocimeter host; the oscilloscope is used for collecting and recording the interference signal generated by the terahertz velocimeter host.

[0008] The present invention utilizes the high penetrability of terahertz waves to microspray particles to penetrate the dense microspray particles and irradiate the free surface of the metal material, and uses the terahertz wave Doppler interferometry technology to measure the velocity history of the free surface of the metal material, filling the data gap of the free surface velocity in the current research on the shock loading process of corroded metal materials.

[0009] Since the size of the microsprayed metal particles generated by shock loading is in the micron range, and the wavelength of terahertz waves is in the submillimeter range, terahertz waves can effectively pass through the metal microspray particles through the diffraction effect, irradiate the free surface of the metal and be reflected by it. This method can be used to measure the velocity history of the free surface of the metal material in the case of a large number of micro-particles in front of the corroded metal material after shock loading.

[0010] Furthermore, it further includes a radio frequency cable for transmitting the interference signal output by the terahertz velocimeter host to the oscilloscope.

[0011] Furthermore, the terahertz wave is an electromagnetic wave with a frequency in the range of 0.1 THz to 10 THz.

[0012] Further, the terahertz focusing mirror is a transmissive terahertz focusing mirror made of a material with weak absorption of terahertz waves or a reflective terahertz focusing mirror made of a metal material.

[0013] Further, the material with weak absorption of terahertz waves is polyethylene, polytetrafluoroethylene or high-resistance silicon.

[0014] Further, a sand wall or a steel plate is placed in the direction of the terahertz velocity measurement host or the terahertz focusing mirror facing the free surface of the corroded metal material.

[0015] The present invention also provides a method for measuring the velocity history of the free surface under impact loading of corroded metal, including the following steps:

[0016] 1) At the beginning of the impact loading test, the terahertz velocity measurement host emits continuous terahertz waves, which are focused by the terahertz focusing mirror, penetrate the microparticles in front of the free surface of the corroded metal material and are vertically transmitted to the free surface of the corroded metal material and are vertically reflected by it;

[0017] 2) The terahertz waves reflected by the free surface of the corroded metal material are collected by the terahertz focusing mirror and then transmitted into the terahertz velocity measurement host. The terahertz velocity measurement host converts the terahertz waves into terahertz interference signals and transmits them to the oscilloscope;

[0018] 3) Analyze and process the terahertz interference signals stored in the oscilloscope to obtain the terahertz Doppler frequency shift f d , and then calculate the velocity u of the free surface of the corroded metal.

[0019] Further, the calculation formula for the velocity u of the free surface of the corroded metal is as follows:

[0020] u = λf d / 2

[0021] λ is the terahertz wave wavelength, and f d is the terahertz Doppler frequency shift.

[0022] Further, the Doppler frequency shift f d = f1 – f0, where f1 is the vibration frequency of the electromagnetic wave after being reflected by an object moving at a speed u, and f0 is the initial emission vibration frequency of the electromagnetic wave.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] The measuring device and method for the free surface velocity history of corroded metals under impact loading provided by the embodiments of the present invention use terahertz waves with a wavelength in the sub-millimeter range, which have high penetrability for micro-scale microjet particles. Therefore, terahertz waves can effectively penetrate the micro-particles generated on the free surface of the corroded metal material under impact loading through diffraction effects and irradiate the metal free surface, and use the terahertz wave Doppler interferometry velocity measurement technology to realize the non-destructive measurement of the free surface velocity history of the metal material in the case of a large number of micro-particles in front of the corroded metal material under impact loading. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is a spectrogram of the free surface velocity of a corroded metal material obtained by the existing PDV technology during the impact loading process;

[0027] Figure 2 It is a schematic structural diagram of the measuring device provided by the embodiments of the present invention;

[0028] Figure 3 It is a comparison diagram of the free surface velocity history of the impact-loaded corroded metal material measured by the embodiments of the present invention and the velocity band obtained by PDV.

[0029] Markings in the drawings and corresponding component names:

[0030] 1 - Free surface of the corroded metal material, 2 - Metal micro-particles, 3 - Terahertz velocity measurement host, 4 - Terahertz wave, 5 - Terahertz focusing lens, 6 - RF cable, 7 - Oscilloscope. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in combination with the embodiments and the drawings. The illustrative embodiments and descriptions thereof of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0032] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that the present invention does not have to be implemented with these specific details. In other embodiments, well-known structures are not specifically described in order to avoid obscuring the present invention.

[0033] Throughout the specification, references to "an embodiment", "embodiments", "an example" or "examples" mean that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Thus, the phrases "an embodiment", "embodiments", "an example" or "examples" appearing throughout the specification do not necessarily all refer to the same embodiment or example. Additionally, the particular features, structures, or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. Further, those of ordinary skill in the art will understand that the diagrams provided herein are for illustrative purposes only and are not necessarily drawn to scale. The term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0034] In the description of the present invention, the orientation or positional relationship indicated by terms such as "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "high", "low", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the protection scope of the present invention.

[0035] Currently, in the aspect of measuring the velocity during the impact loading process of corrosive metals, the Photonic Doppler Velocimetry (PDV) technology is mainly adopted, and generally an infrared laser (1.55 μm) (a small number use visible lasers) is used as the light source. Its working process is as follows: The infrared or visible laser emitted by the PDV probe irradiates the target surface and is reflected by it. Since the target target is moving at a speed u, according to the Doppler effect, the frequency of the reflected signal will increase, and its Doppler frequency shift is Δf Doppler = 2u / λ, where λ is the working wavelength of the laser adopted by PDV. After the infrared laser reflected by the target target enters the PDV probe, it is transmitted by an optical fiber to the PDV host, interferes with the reference laser and is recorded by an oscilloscope. By analyzing the Doppler frequency shift, the moving speed of the target target can be obtained. During the impact loading process of corrosive metal materials, since the scale of micro-matter particles is in the μm level, the infrared or visible laser emitted by PDV will be reflected by the micro-matter particles, and thus the velocity history characteristics of the micro-matter particles are obtained.

[0036] When measuring the velocity parameters during the impact loading of corroded metals based on the PDV technology, there is a major drawback that tiny particulate matter blocks visible or infrared lasers, resulting in the inability to fully measure the free surface velocity. Specifically, when the concentration of tiny particulate matter is high, most of the laser light will be reflected or blocked by the tiny particulate matter, preventing the laser from irradiating the free surface of the metal material and making it impossible to obtain the velocity history of the free surface of the metal material. As Figure 1 shown, the Doppler spectrogram of the shock wave loading of the corroded metal material obtained using the PDV technology is given. It can be seen that during the entire process, the PDV only measures the velocity dispersion band of the tiny particulate matter, and there is no Doppler signal corresponding to the free surface.

[0037] Example 1

[0038] As Figure 2 shown, the embodiment of the present invention provides a measuring device for the velocity history of the free surface under the impact loading of corroded metals, including a terahertz velocity measurement host 3, a terahertz focusing mirror 5, a radio frequency cable 6, and an oscilloscope 7;

[0039] The terahertz velocity measurement host 3 is arranged directly in front of the free surface 1 of the corroded metal material, and is used to emit continuous terahertz waves 4, penetrate the metal microparticles 2 to reach the free surface 1 of the corroded metal material, and recover the terahertz waves 4 reflected by the free surface 1 of the corroded metal material, and generate an interference signal;

[0040] The terahertz focusing mirror 5 is arranged between the terahertz velocity measurement host 3 and the free surface 1 of the corroded metal material, and is used to focus the continuous terahertz waves 4 emitted by the terahertz velocity measurement host 3 onto the free surface 1 of the corroded metal material, and collect and transmit the terahertz waves reflected by the free surface 1 of the corroded metal material to the terahertz velocity measurement host 3;

[0041] The radio frequency cable 6 is used to transmit the interference signal output by the terahertz velocity measurement host to the oscilloscope 7;

[0042] The oscilloscope 7 is used to collect and record the interference signal generated by the terahertz velocity measurement host 3.

[0043] The present invention utilizes the high penetrability of terahertz waves to microspray particles to penetrate through the dense microspray particles and irradiate the surface of the free surface of the metal material, and uses the terahertz wave Doppler interference velocity measurement technology to measure the velocity history of the free surface of the metal material, filling the data gap of the free surface velocity in the current research on the impact loading process of corroded metal materials.

[0044] Since the size of the micro-jet metal particles generated by impact loading is in the micron range, while the wavelength of terahertz waves is in the sub-millimeter range, terahertz waves can effectively pass through the metal micro-jet particles through the diffraction effect, irradiate the free surface of the metal and be reflected by it. This method can use terahertz waves to measure the velocity history of the free surface of a metal material in the case of a large number of micro-particles in front of the corroded metal material after impact loading.

[0045] Preferably, the terahertz wave is an electromagnetic wave with a frequency in the range of 0.1 THz to 10 THz.

[0046] Preferably, the terahertz focusing mirror 5 is a transmissive terahertz focusing mirror made of a material with weak absorption of terahertz waves (such as polyethylene, polytetrafluoroethylene or high-resistivity silicon) or a reflective terahertz focusing mirror made of a metal material.

[0047] Preferably, in order to avoid damage to the test system caused by explosion fragments and shock waves, a metal mirror can be used to turn the transmission direction of the terahertz wave, and a sand wall or steel plate, etc. is placed in the direction of the terahertz velocity measurement host or the terahertz focusing mirror facing the free surface 1 of the corroded metal material to achieve explosion shock protection for the terahertz velocity measurement host and the terahertz focusing mirror.

[0048] Example 2

[0049] The embodiment of the present invention also provides a method for measuring the velocity history of the free surface under impact loading of a corroded metal, including the following steps:

[0050] (1) Before the impact loading test of the corroded metal, install the terahertz velocity measurement host 3 in front of the free surface 1 of the corroded metal material, and adjust the emission direction of the terahertz wave 4 so that it can vertically irradiate the area to be measured on the free surface 1 of the corroded metal material;

[0051] (2) Place the terahertz focusing mirror 5 in the transmission path of the terahertz wave 4, and adjust the front and back positions of the terahertz focusing mirror in the transmission path of the terahertz wave so that the focused spot of the terahertz wave coincides with the surface of the free surface 1 of the corroded metal material;

[0052] (3) Connect the interference signal output port of the terahertz velocity measurement host 3 to the input port of the oscilloscope 7 with a radio frequency cable 6;

[0053] (4) After the impact loading test starts, the terahertz wave 4 emitted by the terahertz velocity measurement host 3 is focused by the terahertz focusing mirror 5, penetrates the micro-particles in front of the free surface of the corroded metal and is transmitted to the surface of the free surface 1 of the corroded metal material and is vertically reflected by it;

[0054] (5) The terahertz wave reflected by the free surface of the corroded metal material is collected by the terahertz focusing mirror 5 and then transmitted into the terahertz velocity measurement host 3. The terahertz velocity measurement host 3 converts the terahertz wave into a terahertz interference signal and outputs it;

[0055] (6) The terahertz interference signal is transmitted to the oscilloscope 7 through the RF cable 6, and the oscilloscope collects and stores the terahertz interference signal;

[0056] (7) After the impact loading test, the terahertz interference signal stored in the oscilloscope is analyzed and processed, and the terahertz Doppler frequency shift f d is obtained through analysis, and then the velocity u of the free surface of the corroded metal material is calculated.

[0057] Specifically, according to the Doppler principle of electromagnetic waves, when the free surface of the corroded metal material is stationary, the Doppler frequency shift of the terahertz wave reflected by it is 0. Therefore, the frequency of the terahertz Doppler interference signal generated by the terahertz velocity measurement host is also 0; when the free surface of the metal moves at a certain velocity u, the Doppler frequency shift of the terahertz wave reflected by it is not zero, and the oscillation frequency f d of the terahertz Doppler interference signal generated by the terahertz velocity measurement host is also not zero, and it is proportional to the velocity u of the free surface of the metal and inversely proportional to the wavelength λ of the terahertz wave.

[0058] f d = 2u / λ

[0059] Therefore, by performing Doppler frequency analysis on the recorded terahertz Doppler interference signal to obtain the terahertz wave Doppler oscillation frequency value f d , the velocity u = λf d / 2 of the free surface of the corroded metal material can be obtained.

[0060] Specifically, according to the Doppler principle, when an electromagnetic wave is reflected by an object moving at a velocity u, its vibration frequency f0 will become f1. This change in vibration frequency is called the corresponding Doppler frequency shift f d ,

[0061]

[0062] After interfering this electromagnetic wave with the original electromagnetic wave (oscillation frequency f0), the oscillation frequency of the obtained interference signal is also f d . Therefore, by measuring the oscillation frequency of the interference signal, the velocity of the target target can be calculated.

[0063] Since within the velocity range of interest (u < 10 km / s), the velocity value u is much smaller than the speed of light c, the denominator of the last term in the above formula can be approximated (1 - u / c ≈ 1). Thus, (using f0λ = c)

[0064]

[0065] The Doppler frequency shift f is obtained through the above formula dThe relative error is less than 0.004% (when u < 10 km / s), so it can be used as a very good approximation.

[0066] As Figure 3 Shown is a comparison diagram of the free surface velocity history of the impact-loaded corrosion metal material measured in this embodiment and the velocity band obtained by PDV. It can be seen from the figure that the signal spectrogram obtained by the PDV technology shows a diffuse band, corresponding to the velocities of multiple microjet particles under the impact loading of the corrosion metal, and the free surface velocity history is not obtained. However, the method adopted in the present invention realizes penetrating the microjet particles and obtaining the velocity history of the free surface of the metal material.

[0067] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A measuring device for the free surface velocity history under impact loading of corroded metal, characterized in that, It includes a terahertz velocity measurement mainframe (3), a terahertz focusing mirror (5) and an oscilloscope (7); The terahertz velocity measurement mainframe (3) is arranged directly in front of the free surface (1) of the corroded metal material, and is used to emit continuous terahertz waves (4) to the free surface (1) of the corroded metal material and recover the terahertz waves (4) reflected by the free surface (1) of the corroded metal material, and generate a Doppler interference signal; The terahertz focusing mirror (5) is arranged between the terahertz velocity measurement mainframe (3) and the free surface (1) of the corroded metal material, and is used to focus the continuous terahertz waves (4) emitted by the terahertz velocity measurement mainframe (3) onto the free surface (1) of the corroded metal material, and collect and transmit the terahertz waves reflected by the free surface (1) of the corroded metal material to the terahertz velocity measurement mainframe (3); The oscilloscope (7) is used to collect and record the Doppler interference signal generated by the terahertz velocity measurement mainframe (3); It also includes a radio frequency cable (6), which is used to transmit the interference signal output by the terahertz velocity measurement mainframe to the oscilloscope (7).

2. The measuring device for the free surface velocity history under impact loading of corroded metal according to claim 1, characterized in that, The terahertz wave (4) is an electromagnetic wave with a frequency in the range of 0.1 THz to 10 THz.

3. The measuring device for the free surface velocity history under impact loading of corroded metal according to claim 1, characterized in that, The terahertz focusing mirror (5) is a transmissive terahertz focusing mirror made of a material with weak absorption of terahertz waves or a reflective terahertz focusing mirror made of a metal material.

4. The measuring device for the free surface velocity history under impact loading of corroded metal according to claim 3, characterized in that, The material with weak absorption of terahertz waves is polyethylene, polytetrafluoroethylene or high-resistance silicon.

5. The measuring device for the free surface velocity history under impact loading of corroded metal according to claim 1, characterized in that, A sand wall or a steel plate is placed in the direction of the terahertz velocity measurement mainframe or the terahertz focusing mirror facing the free surface (1) of the corroded metal material.

6. A measuring method for the free surface velocity history under impact loading of corroded metal based on the measuring device according to any one of claims 1 to 5, characterized in that, It includes the following steps: 1) At the beginning of the impact loading test, the terahertz velocity measurement mainframe emits continuous terahertz waves, and the terahertz waves are focused by the terahertz focusing mirror, penetrate the fine particles in front of the free surface of the corroded metal material and are vertically transmitted to the free surface of the corroded metal material and are vertically reflected by it; 2) The terahertz waves reflected by the free surface of the corroded metal material are collected by the terahertz focusing mirror and then transmitted into the terahertz velocity measurement mainframe. The terahertz velocity measurement mainframe converts the terahertz waves into terahertz interference signals and transmits them to the oscilloscope; 3) Analyze and process the terahertz interference signals stored in the oscilloscope to obtain the terahertz Doppler frequency shift f d , and then calculate the velocity u of the free surface of the corroded metal.

7. The measuring method for the free surface velocity history under impact loading of corroded metal according to claim 6, characterized in that, The calculation formula for the velocity u of the free surface of the corroded metal is as follows: u = λ f d / 2 λ is the wavelength of the terahertz wave, f d is the terahertz Doppler frequency shift.

8. The measuring method for the free surface velocity history under impact loading of corroded metal according to claim 6, characterized in that, The Doppler frequency shift f d = f 1 – f 0, f where 1 is the vibration frequency of the electromagnetic wave after being reflected by an object moving at a speed u, f and 0 is the initial emission vibration frequency of the electromagnetic wave.

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