A microelement three-dimensional dynamic deformation measuring device and method for a dynamic true triaxial system

Abstract

The application provides a micro-element three-dimensional dynamic deformation measurement device and method for a dynamic true triaxial system. A loading device is used to dynamically load a sample, and two laser measurement systems are arranged in the axial direction without loading. In the method, step 1: loading and measurement process and measurement data description; step 2: based on the measurement scheme of the double-face eight-point symmetrical arrangement, a calculation method for the dynamic off-plane deformation value of the X-axis is provided. The application provides a new paradigm for precise measurement under dynamic loading conditions. With the performance of laser Doppler microsecond-level dynamic response and nanometer-level precision, combined with the symmetrical measurement point layout, the interference of absolute displacement is eliminated through mathematical principles, the technical path of dynamic deformation measurement under complex dynamic disturbance is reconstructed from the principle level, and the micro-element three-dimensional dynamic deformation measurement under dynamic true triaxial loading is realized.

Description

Technical Field

[0001] This invention relates to the field of high-end equipment manufacturing, and in particular to the measurement of three-dimensional dynamic deformation of specimens for dynamic true triaxial systems. Background Technology

[0002] Rocks at medium to high strain rates (10 1 s -1 ~10 3 s -1 Dynamic mechanical response studies under certain conditions generally employ split Hopkinson bars, such as... Figure 1 As shown, Figure 1This is a 3D diagram of a dynamic true triaxial electromagnetic Hopkinson bar system in existing technology. However, traditional split Hopkinson bar systems have limitations, only enabling one-dimensional impact loading and allowing analysis of the dynamic mechanical properties of materials under one-dimensional dynamic stress. The invention US20210318216A1 designs and manufactures a dynamic true triaxial electromagnetic Hopkinson bar system. Its innovation lies in the ability to simultaneously apply synchronous stress waves to six incident bars in three axes and six directions, ensuring that the arrival error of the six stress waves is within 5μs, and that the six stress waves exhibit high consistency with an error within 1%. It can achieve one-dimensional, two-dimensional, and even three-dimensional dynamic synchronous loading. In dynamic experiments, the test object is usually considered as a micro-element. It is necessary to fully understand that regardless of whether it is one-dimensional loading or two-dimensional and three-dimensional dynamic loading, the micro-element will undergo three-dimensional dynamic deformation, exhibiting significant volume change characteristics. However, few studies and methods have been conducted on the three-dimensional dynamic deformation characteristics of micro-elements. The three-dimensional dynamic deformation characteristics of materials are of great significance for studying the volume deformation characteristics and failure behavior of materials under different dynamic loading dimensions. To determine the three-dimensional deformation characteristics of a micro-element, it is necessary to calculate the deformation along each axis separately. While the dynamic deformation along the loading axis can be calculated using established stress wave theory, in one-dimensional and two-dimensional dynamic loading, the micro-element exhibits free dynamic out-of-plane deformation along the non-loading axes due to the dynamic Poisson effect. In one-dimensional dynamic loading, there are two non-loading free deformation axes, while in two-dimensional dynamic loading, there is only one. Determining the dynamic out-of-plane deformation along the non-loading free axis is a problem that needs to be solved. In static loading, multiple cameras are typically used to perform full-field three-dimensional DIC (Digital Image Correlation) observations of the free surface of the sample micro-element. This is a non-contact optical measurement technique that measures mechanical properties such as displacement and strain by analyzing pixel changes in an object's surface image before and after deformation. This allows for the acquisition of the sample's three-dimensional deformation characteristics. However, it should be noted that the static loading process is relatively slow, placing low demands on the performance parameters of the cameras, primarily the frame rate. Therefore, the cameras are relatively small, and the entire system is easy to install and set up. In contrast, dynamic loading tests involve instantaneous impact loading of large loads. The deformation of the sample micro-element is transient. To perform three-dimensional DIC observations, high-speed or even ultra-high-speed cameras are required to observe the instantaneous deformation during the loading process. Such cameras are large and expensive. Furthermore, dynamic loading devices are complex, with limited observation space, which restricts the construction of observation systems based on high-speed / ultra-high-speed cameras.

[0003] High strain rate (10) in rock 1 s -1 ~10 3 s -1In dynamic mechanical response research, traditional split Hopkinson bars can only achieve one-dimensional impact loading and corresponding stress state analysis, which is insufficient to meet the needs of multi-dimensional loading. The newly invented dynamic true triaxial electromagnetic Hopkinson bar system can simultaneously apply consistent (time difference ≤ 5μs, waveform error ≤ 1%) triaxial six-axis stress waves through six incident bars, supporting one-dimensional to three-dimensional dynamic synchronous loading, providing a fundamental condition for multi-dimensional loading experiments. Regardless of one-dimensional, two-dimensional, or three-dimensional loading, the micro-element will undergo three-dimensional dynamic deformation with volume change characteristics. While the axial deformation under loading can be calculated using mature stress wave theory, the two unloaded free axes under one-dimensional loading and the one unloaded free axis under two-dimensional loading will experience free-plane deformation due to the dynamic Poisson effect. The measurement of these key deformation characteristics remains a technological gap. While the three-dimensional deformation of micro-elements can be obtained through full-field three-dimensional DIC observation using multiple cameras during static loading, dynamic loading experiments involve large-load transient impacts (rapid deformation speed), require high-speed / ultra-high-speed cameras (large size and high cost), and have compact loading devices (narrow reserved observation space), making it difficult to implement traditional optical observation methods.

[0004] Therefore, there is an urgent need to develop a three-dimensional dynamic deformation monitoring device and method for specimen micro-elements that is adapted to the loading environment of dynamic true triaxial testing, and combines high sampling rate, high accuracy, and low cost. The key focus should be on overcoming the challenge of efficiently capturing dynamic out-of-plane deformation along unloaded free axes, thereby improving experimental efficiency and the diversity of observation results. This is crucial for revealing the effects of material deformation at medium to high strain rates (10⁻⁶ rpm). 1 s -1 ~10 3 s -1 The volumetric deformation mechanism and failure behavior under multidimensional loading are of key scientific significance and are also the core requirement for promoting the comprehensive development of dynamic true triaxial testing technology. Summary of the Invention

[0005] To address this challenge and successfully measure dynamic out-of-plane deformation and calculate dynamic volumetric deformation under free and unrestricted conditions in complex dynamic loading environments, this invention designs a three-dimensional dynamic deformation measurement device and method for micro-element bodies in dynamic true triaxial systems.

[0006] To address the problems in existing technologies, this invention provides a three-dimensional dynamic deformation measurement device for a micro-element in a dynamic true triaxial system. The device includes a loading device and a sample. The loading device is a dynamic true triaxial electromagnetic Hopkinson bar system. The sample is dynamically loaded using the loading device. Two laser measurement systems are set along the unloaded axis. Taking the X-axis as an example: an X+ laser measurement system and an X- laser measurement system are set on the X-axis. Measurement points are arranged on the sample. The X+ and X- intermediate measurement points are symmetrically arranged at the center point of the sample. Based on the principle of three-point plane positioning, measurement points are arranged in the X+ and X- directions respectively. The sample X+ has three measurement points: upper X+, lower right X+, and lower left X+. The sample X- has three measurement points: upper X-, lower left X-, and lower right X-. The X+ laser measurement system measures the deformation of the sample in the X+ direction, while the X- laser measurement system measures the deformation in the X- direction. The X+ laser measurement system includes lasers for measuring the upper X+ measurement point, the middle X+ measurement point, and the lower left X+ measurement point. The X-laser measurement system includes lasers for measuring the X+ lower right measurement point of the sample; X-laser measurement systems for measuring the X-upper measurement point of the sample, the X-middle measurement point of the sample, the X-lower left measurement point of the sample, and the X-lower right measurement point of the sample; and X+ upper, lower right, and lower left measurement points around the X+ middle measurement point of the sample. Three measuring points are arranged in an equilateral triangle around the middle measuring point of sample X+, with the centroid of the equilateral triangle coinciding with the middle measuring point of sample X+. Similarly, three measuring points—the upper measuring point of sample X-, the lower left measuring point of sample X-, and the lower right measuring point of sample X-—are arranged in an equilateral triangle around the middle measuring point of sample X-, with the centroid of the equilateral triangle coinciding with the middle measuring point of sample X-. These three measuring points around the middle measuring point of sample X+ correspond one-to-one with the three measuring points around the middle measuring point of sample X-, and the line connecting any two corresponding measuring points is parallel to the X-axis.

[0007] As a further improvement of the present invention, the dynamic loading is a dual-axis four-way synchronous loading or a single-axis two-way synchronous loading.

[0008] As a further improvement of the present invention, the sample to be tested is a 50 mm cube.

[0009] As a further improvement of the present invention, the measurement point on the sample X+ is located directly above the middle measurement point on the sample X+; the measurement point on the sample X- is located directly above the middle measurement point on the sample X-.

[0010] A method for measuring the three-dimensional dynamic deformation of a micro-element in a dynamic true triaxial system. Step 1: Loading and measurement process, measurement data description; Under biaxial four-way synchronous loading or single-axis biaxial synchronous loading, if one or two axes of the sample are not loaded, taking the X-axis direction as an example, the method for measuring the dynamic out-of-plane deformation of the sample in the X-axis direction is as follows: Relying on the loading device, X+ laser measurement system and X- laser measurement system are respectively placed in the X+ and X- axes. The rules for the arrangement of measurement points are as follows: The central core measurement point is symmetrically arranged at the center point of the sample surface to be measured, which are the X+ middle measurement point and the X- middle measurement point of the sample. Three measurement points are set on the outside of the X+ middle measurement point and the X- middle measurement point of the sample, respectively. The three measurement points are distributed around the central core measurement point in the form of an equilateral triangle. It is required that the centroid of the equilateral triangle coincides with the central core measurement point. The three measurement points around the X+ middle measurement point and the three measurement points around the X- middle measurement point are set one-to-one. The line connecting the two one-to-one corresponding measurement points is parallel to the X-axis.

[0011] The out-of-plane displacement and out-of-plane velocity of the sample at the X+ central measurement point and its surrounding three measurement points were determined using laser Doppler technology and denoted as follows: , , , , , , , ;

[0012] The out-of-plane displacement and out-of-plane velocity of the sample at the X-center measurement point and its surrounding three measurement points were determined using laser Doppler technology, and denoted as follows: , , , , , ;

[0013] Step 2: Based on the measurement scheme of double-sided eight-point symmetrical arrangement, propose the dynamic out-of-plane deformation value of the X-axis. The calculation method;

[0014] Step 2.1: Calculate the dynamic out-of-plane deformation value based on the displacement measurement results. Calculation: Two measuring points on the same axis constitute a set of symmetrical measuring points, for a total of four sets of symmetrical points. The dynamic out-of-plane deformation value of the first set of symmetrical points is calculated. Dynamic out-of-plane deformation value of the second symmetrical point group Dynamic out-of-plane deformation value of the third symmetrical point group Dynamic out-of-plane deformation value of the fourth symmetrical point group After obtaining the deformation at each symmetrical point group, the average deformation at each symmetrical point group is taken as the deformation of the specimen along the X-axis.

[0015]

[0016] The deformation of the specimen along the X-axis is obtained. Further calculations were performed on the strain of the specimen under unconfined X-axis conditions, where... The original length of the specimen on the X-axis before loading:

[0017]

[0018] Step 2.2: Calculate the dynamic out-of-plane deformation value based on the velocity measurement results. Calculate: the dynamic out-of-plane velocity value of the first symmetrical point group. The dynamic out-of-plane velocity value of the second symmetrical point group The dynamic out-of-plane velocity value of the third symmetrical point group The dynamic out-of-plane velocity value of the fourth symmetrical point group The out-of-plane velocity values ​​at each symmetrical point group are integrated to obtain the out-of-plane deformation value at each symmetrical point group. The average value is then used as the deformation result of the specimen along the X-axis.

[0019] .

[0020] As a further improvement of the present invention, the distance between the three measuring points on the edge and the edge of the sample is greater than 10 mm.

[0021] As a further improvement of the present invention, the distance between the three measuring points on the edge and the edge of the sample is 12mm to 18mm.

[0022] As a further improvement of the present invention, the time accuracy of the velocity signal measured by laser Doppler is at least greater than 1 μs.

[0023] As a further improvement of the present invention, the time accuracy of the velocity signal measured by laser Doppler is 1 μs to 0.1 μs.

[0024] As a further improvement of the present invention, step 2.3 is also included: calculating the volumetric strain of the specimen based on the measured dynamic out-of-plane strain; the specimen is in a two-dimensional stress state under the loading mode of two axes, and compressive deformation occurs on the Y and Z loading axes. The corresponding strain is calculated based on stress wave theory. The deformation and strain occurring on the Y and Z axes are respectively denoted as... , and , The original lengths of the sample along the X, Y, and Z axes are denoted as follows: , and The volumetric strain that occurs is denoted as , = .

[0025] The beneficial effects of this invention are:

[0026] This invention provides a new paradigm for precise measurement under dynamic loading conditions. With the performance of laser Doppler microsecond-level dynamic response and nanometer-level precision, combined with a symmetrical measurement point layout, the interference of absolute displacement is eliminated through mathematical principles. It reconstructs the technical path for dynamic deformation measurement under complex dynamic disturbances from the principle level, and realizes the three-dimensional dynamic deformation measurement of micro-element under dynamic true triaxial loading.

[0027] It achieves improved performance indicators, with significantly enhanced measurement accuracy and dynamic response capabilities compared to traditional strain gauges and high-speed cameras. At the same time, it redefines the economic efficiency and engineering applicability of high-precision measurement equipment with lower costs and a smaller footprint.

[0028] By avoiding the limitations of electromagnetic / high-temperature interference of strain gauges through non-contact measurement, it provides a feasible and accurate means for high-precision dynamic out-of-plane displacement measurement under special working conditions such as high temperature. The symmetrical layout overcomes the spatial installation problem of high-speed DIC and provides a complete solution of "measurement accuracy - environmental adaptability - engineering feasibility" for the typical complex working condition of dynamic true triaxial system.

[0029] This method innovatively applies laser Doppler measurement to the field of dynamic out-of-plane deformation measurement, proposing a symmetrical measurement method based on a laser Doppler vibrometer and related calculation methods for symmetrical measurement. The laser Doppler vibrometer used in this method has advantages such as high precision, strong dynamic monitoring capability, and small equipment size, enabling high-precision transient displacement measurement within a limited space. Furthermore, based on the proposed symmetrical measurement method, multiple symmetrical measurement points are arranged in two directions along the deformation axis. This symmetrical measurement method avoids measurement errors caused by sample deflection during testing and comprehensively considers the dynamic deformation information of the micro-element sample along a certain deformation axis. By measuring the dynamic out-of-plane displacement information of the micro-element sample under different stress states, the three-dimensional dynamic deformation behavior and dynamic volume change process of the material can be described.

[0030] This invention innovatively combines a laser Doppler vibrometer with a symmetrical measurement method, achieving the measurement results of out-of-plane displacement using a traditional high-speed camera at a lower cost. It breaks through the technical bottleneck of dynamic out-of-plane deformation measurement in confined spaces and has advantages such as high precision, strong dynamic response, and small size. It eliminates sample deflection error and comprehensively captures the dynamic deformation information of micro-elements, realizing efficient and accurate measurement of three-dimensional deformation and volume change under complex loading environments. It can also significantly improve the scientificity and reliability of dynamic true triaxial tests. Attached Figure Description

[0031] Figure 1 This is a 3D diagram of a dynamic true triaxial electromagnetic Hopkinson rod system in the existing technology;

[0032] Figure 2 This is a 3D diagram of a dynamic true triaxial electromagnetic Hopkinson rod system with an additional 3D dynamic deformation measurement device;

[0033] Figure 3 This is a schematic diagram of a laser measurement system (taking the X+ laser measurement system as an example).

[0034] Figure 4 This is a schematic diagram of the three-dimensional dynamic deformation measurement device in the system (taking the X-axis as an example).

[0035] Figure 5 This is a schematic diagram of the overall layout of the symmetrical measuring points;

[0036] Figure 6 This is a schematic diagram of the layout of measuring points on a single measuring surface;

[0037] Figure 7 This is a schematic diagram of the measuring point layout scheme;

[0038] Figure 8 It is a dynamic measurement optical path test diagram;

[0039] Figure 9a The graph shows the measured dynamic out-of-plane displacement results (the measured dynamic out-of-plane displacement of the sample surface obtained using a laser Doppler vibration meter, demonstrating the feasibility of this method).

[0040] Figure 9b The diagram shows the measured dynamic out-of-plane strain results (the dynamic out-of-plane strain results calculated from the dynamic out-of-plane displacement of the sample surface measured by a laser Doppler vibration meter, illustrating the feasibility of this method).

[0041] The component names corresponding to the numbers in the diagram are as follows: 001-Loading device, 002-Loading device Y+waveguide rod, 003-Loading device Y-waveguide rod, 004-Loading device Z+waveguide rod, 005-Loading device Z-waveguide rod, 201-X+laser measurement system, 202-X-laser measurement system, 203-X+laser measurement system support component, 204-X+laser measurement system upper point measurement laser, 205-X+laser measurement system middle point measurement laser, 206-X+laser measurement system lower left point measurement... Laser measurement: 207-X+ laser measurement system lower right point measurement laser, 300-sample, 401-sample X- upper measurement point, 402-sample X- middle measurement point, 403-sample X- lower left measurement point, 404-sample X- lower right measurement point, 405-sample X+ upper measurement point, 406-sample X+ middle measurement point, 407-sample X+ lower right measurement point, 408-sample X+ lower left measurement point, 501-X+ laser measurement system optical path, 502-X- laser measurement system optical path. Detailed Implementation

[0042] The invention will now be further described with reference to the accompanying drawings.

[0043] Specific Implementation Method 1: A three-dimensional dynamic deformation measurement device for micro-element in a dynamic true triaxial system, such as... Figure 2 As shown, the device includes a loading device 001 and a sample 300. The loading device 001 is a dynamic true triaxial electromagnetic Hopkinson bar system. The loading device 001 is used to dynamically load the sample 300. The dynamic loading is either biaxial four-way synchronous loading or uniaxial bidirectional synchronous loading. The sample 300 being tested is preferably a 50mm cube.

[0044] Two laser measurement systems are set up along the unloaded axis. Taking the X-axis as an example: X+ laser measurement system 201 and X- laser measurement system 202 are set up on the X-axis. Measurement points are arranged on the sample 300. The X+ intermediate measurement point 406 and the X- intermediate measurement point 402 are symmetrically arranged at the center point of the sample 300. Based on the principle of three-point plane, the X+ measurement point 405 is arranged in the X+ and X- directions respectively (the X+ measurement point 405 is located at the X+ intermediate measurement point 406). The X+ laser measurement system 201 is used to measure the deformation information of the sample 300 in the X+ direction, and the X- laser measurement system 202 is used to measure the deformation information of the sample 300 in the X- direction. The X+ laser measurement system 202 is used to measure the deformation information of the sample 300 in the X- direction. The X+ laser measurement system 202 is used to measure the deformation information of the sample 300 in the X- direction.

[0045] like Figure 3 , Figure 4 and Figure 6 As shown, the X+ laser measurement system 201 is equipped with an X+ laser measuring laser 204 for measuring the upper X+ measurement point 405 of the sample X+, an X+ laser measuring laser 205 for measuring the middle X+ measurement point 406 of the sample X+, an X+ laser measuring laser 206 for measuring the lower left X+ measurement point 408 of the sample X+, and an X+ laser measuring laser 207 for measuring the lower right X+ measurement point 407 of the sample X+.

[0046] like Figure 5 As shown, the X-laser measurement system 202 includes an upper X-laser measurement laser for measuring the upper X-measurement point 401 of the sample, a middle X-laser measurement laser for measuring the middle X-measurement point 402 of the sample, a lower left X-laser measurement laser for measuring the lower left X-measurement point 403 of the sample, and a lower right X-laser measurement laser for measuring the lower right X-measurement point 404 of the sample; three measurement points surrounding the middle X-measurement point 406 of the sample are distributed in an equilateral triangle shape on the sample: upper X-measurement point 405 of the sample, lower right X-measurement point 407 of the sample, and lower left X-measurement point 408 of the sample. Around the X+ middle measurement point 406, the centroid of the equilateral triangle coincides with the X+ middle measurement point 406. Around the X- middle measurement point 402, the three measurement points X-upper measurement point 401, X-lower left measurement point 403, and X-lower right measurement point 404 are distributed in the form of an equilateral triangle around the X- middle measurement point 402, and the centroid of the equilateral triangle coincides with the X- middle measurement point 402. The three measurement points around the X+ middle measurement point 406 and the three measurement points around the X- middle measurement point 402 are set in a one-to-one correspondence, and the line connecting two corresponding measurement points is parallel to the X-axis.

[0047] Specific Implementation Method 2: The following example uses the dynamic out-of-plane deformation measurement of the specimen in the X-axis direction under biaxial four-way synchronous loading as an example to illustrate the measuring device and method. This method is still applicable to the dynamic out-of-plane deformation measurement of the specimen in the unloaded axis direction under uniaxial two-way synchronous loading. If the Z-axis is loaded, the X-axis and Y-axis can be measured using this method respectively.

[0048] Step 1: Loading and measurement process, measurement data description.

[0049] Taking the dynamic out-of-plane deformation measurement of the specimen in the X-axis direction under biaxial four-way synchronous loading as an example, this measurement device and method are described. The loading device 001 is used to dynamically load the specimen 300. During dynamic loading, the four stress waves in the biaxial four-way direction reach the specimen through the loading device Y+ waveguide rod 002, loading device Y- waveguide rod 003, loading device Z+ waveguide rod 004, and loading device Z- waveguide rod 005, respectively, achieving biaxial four-way synchronous loading of the specimen. Under this loading mode, the specimen is in a two-dimensional stress state, with stress waves along the Y and Z loading axes. When compression deformation occurs due to impact, dynamic out-of-plane deformation will occur along the X-axis (here, out-of-plane deformation refers to displacement and deformation along the X-axis that are perpendicular to the YZ plane, which cannot be measured by conventional strain gauges or other contact measurement methods, and high-speed / ultra-high-speed DIC technology is difficult to apply to this measurement scenario due to its large equipment size). For measuring this dynamic out-of-plane deformation, this invention proposes the following measurement method: relying on the loading device 001, X+ laser measurement system 201 and X- laser measurement system 202 are respectively installed along the X+ and X- axes. The test sample 300 is usually small, a 50mm cube. Thanks to laser Doppler measurement technology, its optical probe has a small size, allowing multiple probes to be arranged within a small measured area to obtain an averaged result that better represents the deformation level. The measurement point arrangement rules are as follows: the X+ intermediate measurement point 406 and the X- intermediate measurement point 402 are symmetrically arranged at the center point of the sample 300. Then, based on the principle of three-point plane determination, the X+ laser measurement system 202 is arranged in the X+ and X- directions respectively. The X+ laser measurement system 201 measures the deformation of the sample 300 in the X+ direction, and the X- laser measurement system 202 measures the deformation of the sample 300 in the X- direction. The X+ laser measurement system 202 measures the deformation of the sample 300 in the X- direction. The optical paths formed are as follows: X+ laser measurement system optical path 501, X- laser measurement system optical path 502, etc. Figure 8 As shown. A measuring instrument based on the laser Doppler principle can measure the displacement and velocity of the measured point separately. Based on this method, for measurement point 405 on the X+ plane of the sample, the X+ laser measuring system using point measurement laser 204 can determine the out-of-plane displacement and out-of-plane velocity of that point perpendicular to the YZ plane, denoted as... , For the sample X+ intermediate measurement point 406, the X+ laser measurement system intermediate point measurement laser 205 can determine the out-of-plane displacement and out-of-plane velocity of this point perpendicular to the YZ plane, which are denoted as follows: , For the sample X+ lower right measurement point 407, the X+ laser measurement system's lower right point measurement laser 207 can determine the out-of-plane displacement and out-of-plane velocity perpendicular to the YZ plane at that point, denoted as ; , For the sample X+ lower left measurement point 408, the X+ laser measurement system's lower left point measurement laser 206 can determine the out-of-plane displacement and out-of-plane velocity perpendicular to the YZ plane at that point, denoted as ; , Similarly, for the sample X-measurement point 401, sample X-middle measurement point 402, sample X-lower left measurement point 403, and sample X-lower right measurement point 404, their out-of-plane displacement and out-of-plane velocity perpendicular to the YZ plane can be determined by laser Doppler technology, and denoted as follows: , , , , , , , .

[0050] Explanation of the four-point measurement scheme: The four-point scheme is an optimal solution based on geometric measurement principles and reliability engineering concepts. Its value lies in constructing a spatial reference plane through non-collinear point placement. While satisfying the "three-point plane determination" geometric constraint, a fourth central core measurement point is introduced. This central core measurement point not only ensures the measurement of important data at the center point of the specimen but also creates measurement redundancy. This layout significantly improves system robustness by increasing degrees of freedom, ensuring that even when single-point data is abnormal, the out-of-plane deformation characteristics can still be stably reconstructed using the remaining three points. The distribution of measurement points must follow the principle of spatial uniformity. The central measurement point is used to capture the deformation response of the main body, while the edge measurement points together construct a reference frame describing the planar attitude change. Their collaborative work enables the measurement of rigid displacement and dynamic out-of-plane displacement of the specimen, and then the calculation of dynamic deformation is achieved through bi-directional symmetrical measurement. This scheme, based on geometric constraint mechanisms and system stability design, provides a feasible solution for dynamic out-of-plane deformation measurement. For the arrangement of the four measuring points, the central measuring point should be located at the center of the surface of the sample being measured, and the other three measuring points should be distributed around the central measuring point in an equilateral triangle. The centroid of the equilateral triangle should coincide with the central core measuring point, and the distance between the three measuring points and the edge of the sample should be greater than 10 mm.

[0051] Step 2: Explanation of the calculation method and measuring point layout scheme. During impact loading, the specimen 300 undergoes deformation and slight displacement in the X direction, denoted as follows: , , among which deformation This is due to the dynamic deformation characteristics of the sample 300 itself, and the small displacement. This refers to the motion characteristics of the specimen 300 during loading due to vibration or pre-existing deflection. Ideally, the specimen 300 only deforms. And the deformation This is the quantity of greatest concern in the experiment, but in actual experiments, the loading process inevitably causes a small displacement of the specimen 300. If in measuring deformation At that time, a small displacement Including this will cause deformation. The results showed a significant error compared to the actual values. Only by setting up a reasonable measurement point scheme could reliable data be obtained, and only a calculation method based on reliable measurement data could reasonably depict the relevant deformation characteristics. (Measurement of 300 mm deformation of the sample) Different measuring point schemes, such as Figure 7 The discussion is as follows: for the single-sided measuring point method, measuring point 1 only considers deformation. And not considered At the same time, displacement was introduced. Regarding interference with measurement results: When using a two-sided asymmetrical measuring point arrangement, the displacement can be eliminated by superimposing the measurements from measuring points 1 and 2. Regarding the interference with the measurement results, further consideration is needed when the sample 300 exhibits partial deflection. While the asymmetrical arrangement of measuring points on both sides can eliminate displacement... This introduces interference with the measurement results, but further introduces the issue of deflection angle. The resulting sample rotation error (when the two sides are asymmetrical, due to the 30° deflection of the sample, the measured values ​​at both sides may be reduced simultaneously, ultimately leading to a decrease in the deformation value) (Too small), which will also affect the measurement deformation. This introduces interference, but when two symmetrical measuring points are set up, the displacement problem is solved. To mitigate interference with the measurement results, the potential interference from sample deflection at 300° was eliminated, ensuring high accuracy of the measurement results and maximizing the deformation value. Credible.

[0052] Based on a measurement scheme with a double-sided eight-point symmetrical arrangement, a method for measuring the dynamic out-of-plane deformation value along the X-axis is proposed. The precise calculation method:

[0053] Step 2.1 Calculate the dynamic out-of-plane deformation value based on the displacement measurement results. calculate.

[0054] In the above discussion and design of the measuring point layout scheme, the double-sided symmetrical measuring point layout can solve the interference of the overall displacement and deflection of the sample 300 on the measurement results. This test and calculation method further proposes a double-sided eight-point symmetrical measurement method, in which two measuring points on the same axis constitute a group of symmetrical measuring points. The upper measuring point 401 of sample X- and the upper measuring point 405 of sample X+ constitute the first symmetrical point group, the middle measuring point 402 of sample X- and the middle measuring point 406 of sample X+ constitute the second symmetrical point group, the lower left measuring point 403 of sample X- and the lower left measuring point 408 of sample X+ constitute the third symmetrical point group, and the lower right measuring point 404 of sample X- and the lower right measuring point 407 of sample X+ constitute the fourth symmetrical point group, for a total of four groups of symmetrical points. The dynamic out-of-plane deformation value of the first symmetrical point group is... Dynamic out-of-plane deformation value of the second symmetrical point group Dynamic out-of-plane deformation value of the third symmetrical point group Dynamic out-of-plane deformation value of the fourth symmetrical point group After obtaining the deformation at each symmetrical point group, in order to better represent the deformation result of the specimen 300 on the X-axis, the average deformation at each symmetrical point group is taken as the deformation result of the specimen 300 on the X-axis:

[0055]

[0056] The deformation of sample 300 along the X-axis was obtained. Furthermore, the strain of specimen 300 under unconfined X-axis conditions can be calculated, where... The original length of specimen 300 on the X-axis before loading:

[0057]

[0058] Step 2.2 Calculate the dynamic out-of-plane deformation value based on the velocity measurement results. calculate.

[0059] In most laser Doppler measuring instruments, the measurement method involves measuring the velocity at the measurement point. This method also provides the dynamic out-of-plane deformation value based on the velocity measurement method. The calculation method includes the dynamic out-of-plane velocity values ​​of the first symmetrical point group. The dynamic out-of-plane velocity value of the second symmetrical point group The dynamic out-of-plane velocity value of the third symmetrical point group The dynamic out-of-plane velocity value of the fourth symmetrical point group The out-of-plane velocity values ​​at each symmetrical point group are integrated to obtain the out-of-plane deformation value at each symmetrical point group. The average value is then used as the deformation result of sample 300 along the X-axis.

[0060]

[0061] It should be noted that the velocity result obtained by velocity demodulation is the velocity result, and the displacement result needs to be obtained by integration. Therefore, high time accuracy is required for the measurement. Considering that a dynamic loading process is usually several hundred μs, the time accuracy of the velocity signal measured by laser Doppler must be at least greater than 1 μs.

[0062] Furthermore, a method for calculating the dynamic deformation of the three-dimensional volume can be provided.

[0063] Step 2.3 Calculate the volumetric strain of the specimen based on the measured dynamic out-of-plane strain.

[0064] Under this loading mode, the specimen is in a two-dimensional stress state, undergoing compressive deformation along the Y and Z loading axes. The corresponding strain can be calculated based on stress wave theory (the relevant calculation methods are well-established). The deformation and strain occurring along the Y and Z axes are denoted as follows: , and , .

[0065] The original lengths of sample 300 along the X, Y, and Z axes are denoted as follows: , and The volumetric strain that occurs is denoted as .

[0066] = .

[0067] Figure 9a The graph shows the measured dynamic out-of-plane displacement results. The measured dynamic out-of-plane displacement of the sample surface, obtained using a laser Doppler vibration meter, demonstrates the feasibility of this method.

[0068] Figure 9b The graph shows the measured dynamic out-of-surface strain results. The dynamic out-of-surface strain results are calculated from the dynamic out-of-surface displacement of the sample surface measured by a laser Doppler vibration meter, demonstrating the feasibility of this method.

[0069] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A three-dimensional dynamic deformation measurement device for a micro-element in a dynamic true triaxial system, characterized in that: The system includes a loading device (001) and a sample (300). The loading device (001) is a dynamic true triaxial electromagnetic Hopkinson bar system. The loading device (001) is used to dynamically load the sample (300). Two laser measurement systems are set in the unloaded axis. Taking the X-axis as an example: an X+ laser measurement system (201) and an X- laser measurement system (202) are set on the X-axis. Measurement points are arranged on the sample (300). The X+ middle measurement point (406) and the X- middle measurement point (402) are symmetrically arranged at the center point of the sample (300). Based on the principle of three-point plane, the X+ measurement point (405) and the X+ lower right measurement point (402) are arranged in the X+ and X- directions, respectively. Measurement points (407) and X+ lower left measurement point (408), X- upper measurement point (401), X- lower left measurement point (403), and X- lower right measurement point (404) of the sample, wherein the X+ laser measurement system (201) is used to measure the deformation information of the sample (300) in the X+ direction, and the X- laser measurement system (202) is used to measure the deformation information of the sample (300) in the X- direction; the X+ laser measurement system (201) is equipped with an X+ laser upper point measurement laser (204) for measuring the X+ upper measurement point (405) of the sample, an X+ laser middle point measurement laser (205) for measuring the X+ middle measurement point (406) of the sample, and a measurement... The X+ laser measurement system has a lower left measuring laser (206) for measuring the lower left measuring point (408) of the sample X+ and a lower right measuring laser (207) for measuring the lower right measuring point (407) of the sample X+; the X-laser measurement system (202) is equipped with an upper measuring laser for measuring the upper measuring point (401) of the sample X-, a middle measuring laser for measuring the middle measuring point (402) of the sample X-, a lower left measuring laser for measuring the lower left measuring point (403) of the sample X-, and a lower right measuring laser for measuring the lower right measuring point (404) of the sample X-; the X+ middle measuring point The three measuring points around the middle measuring point (406) of the sample X+ are the upper measuring point (405), the lower right measuring point (407), and the lower left measuring point (408) of the sample X+, which are distributed in the form of an equilateral triangle around the middle measuring point (406) of the sample X+. The centroid of the equilateral triangle coincides with the middle measuring point (406) of the sample X+. The three measuring points around the middle measuring point (402) of the sample X- are the upper measuring point (401), the lower left measuring point (403), and the lower right measuring point (404) of the sample X- are distributed in the form of an equilateral triangle around the middle measuring point (402) of the sample X-. The centroid of the equilateral triangle coincides with the middle measuring point (402) of the sample X-.The three measuring points around the intermediate measuring point (406) of sample X+ are set one-to-one with the three measuring points around the intermediate measuring point (402) of sample X-, and the line connecting two of the one-to-one corresponding measuring points is parallel to the X-axis.

2. The three-dimensional dynamic deformation measurement device for a micro-element in a dynamic true triaxial system according to claim 1, characterized in that: The dynamic loading is either dual-axis four-way synchronous loading or single-axis bidirectional synchronous loading.

3. The three-dimensional dynamic deformation measurement device for a micro-element in a dynamic true triaxial system according to claim 1, characterized in that: The test specimen (300) is a 50 mm cube.

4. The three-dimensional dynamic deformation measurement device for a micro-element in a dynamic true triaxial system according to claim 1, characterized in that: The measurement point (405) on the X+ sample is located directly above the middle measurement point (406) on the X+ sample; the measurement point (401) on the X- sample is located directly above the middle measurement point (402) on the X- sample.

5. A method for measuring the three-dimensional dynamic deformation of a micro-element in a dynamic true triaxial system using the measuring device of claim 1, characterized in that: Step 1: Loading and Measurement Process and Measurement Data Description; Under biaxial four-way synchronous loading or uniaxial bidirectional synchronous loading, if one or two axes of the sample are not loaded, taking the X-axis direction as an example, the method for measuring the dynamic out-of-plane deformation of the sample in the X-axis direction is as follows: Relying on the loading device (001), the X+ laser measurement system (201) and the X- laser measurement system (202) are respectively installed in the X+ and X- axes. The measurement point arrangement rules are as follows: The central core measurement points are symmetrically arranged at the center point of the measured surface of the sample (300), which are the X+ core points of the sample. Three measuring points are provided on the outer sides of the intermediate measuring point (406) and the sample X-intermediate measuring point (402), the sample X+intermediate measuring point (406) and the sample X-intermediate measuring point (402), respectively. The three measuring points are distributed around the central core measuring point in the form of an equilateral triangle. It is required that the centroid of the measuring equilateral triangle coincides with the central core measuring point. The three measuring points around the sample X+intermediate measuring point (406) and the three measuring points around the sample X-intermediate measuring point (402) are set one-to-one. The line connecting the two one-to-one corresponding measuring points is parallel to the X-axis. The out-of-plane displacement and out-of-plane velocity perpendicular to the YZ plane of the sample X+ at the central measurement point (406) and three surrounding measurement points were determined using laser Doppler technology and denoted as follows: , , , , , , , ; The out-of-plane displacement and out-of-plane velocity perpendicular to the YZ plane of the sample X-center measurement point (402) and its three surrounding measurement points were determined by laser Doppler technology and denoted as follows: , , , , , ; Step 2: Based on the measurement scheme of double-sided eight-point symmetrical arrangement, propose the dynamic out-of-plane deformation value of the X-axis. The calculation method; Step 2.1: Calculate the dynamic out-of-plane deformation value based on the displacement measurement results. Calculation: Two measuring points on the same axis constitute a set of symmetrical measuring points, for a total of four sets of symmetrical points. The dynamic out-of-plane deformation value of the first set of symmetrical points is calculated. Dynamic out-of-plane deformation value of the second symmetrical point group Dynamic out-of-plane deformation value of the third symmetrical point group Dynamic out-of-plane deformation value of the fourth symmetrical point group After obtaining the deformation at each symmetrical point group, the average deformation at each symmetrical point group is taken as the deformation result of the specimen (300) on the X-axis: The deformation of the specimen (300) along the X-axis was obtained. Further calculations were performed on the strain of specimen (300) under unconfined X-axis conditions, where... The original length of the specimen (300) on the X-axis before loading: Step 2.2: Calculate the dynamic out-of-plane deformation value based on the velocity measurement results. Calculate: the dynamic out-of-plane velocity value of the first symmetrical point group. The dynamic out-of-plane velocity value of the second symmetrical point group The dynamic out-of-plane velocity value of the third symmetrical point group The dynamic out-of-plane velocity value of the fourth symmetrical point group The out-of-plane velocity values ​​at each symmetrical point group are integrated to obtain the out-of-plane deformation values ​​at each symmetrical point group. The average value is then used as the deformation result of the specimen (300) on the X-axis. 。 6. The method for measuring the three-dimensional dynamic deformation of a micro-element in a dynamic true triaxial system according to claim 5, characterized in that: The distance between the three measuring points on the edge and the edge of the sample is greater than 10 mm.

7. The method for measuring the three-dimensional dynamic deformation of a micro-element in a dynamic true triaxial system according to claim 6, characterized in that: The distance from the three measuring points on the edge to the edge of the sample is 12mm to 18mm.

8. The method for measuring the three-dimensional dynamic deformation of a micro-element in a dynamic true triaxial system according to claim 5, characterized in that: The time accuracy of the velocity signal measured by laser Doppler is at least greater than 1 μs.

9. The method for measuring the three-dimensional dynamic deformation of a micro-element in a dynamic true triaxial system according to claim 8, characterized in that: The time accuracy of the velocity signal measured by laser Doppler is from 1 μs to 0.1 μs.

10. The method for measuring the three-dimensional dynamic deformation of a micro-element in a dynamic true triaxial system according to claim 5, characterized in that: The process also includes step 2.3: calculating the volumetric strain of the specimen based on the measured dynamic out-of-plane strain; the specimen is in a two-dimensional stress state under a two-axis loading mode, undergoing compressive deformation along the Y and Z loading axes, and the corresponding strain is calculated based on stress wave theory. The deformation and strain occurring along the Y and Z axes are denoted as follows: , and , The original lengths of the sample (300) along the X, Y, and Z axes are denoted as follows: , and The volumetric strain that occurs is denoted as , = .

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