Experimental apparatus and methods for measuring the mechanical properties of materials across a wide strain rate range

Abstract

An experimental apparatus and method for measuring the mechanical properties of materials across a wide strain rate range are disclosed. Low strain rate loading is achieved via motor propulsion, while medium and high strain rate loading is performed via a loading gun, achieving a range of 10... ‑3 s ‑1 ~10 3 s ‑1 This invention, through mechanical property testing experiments within the strain rate range, overcomes the bottleneck in medium strain rate loading and fills the gap between domestic and international servo hydraulic testing machines and Hopkinson bar loading tests. Based on electromagnetic riveting technology, the invention improves the Hopkinson bar by increasing inductance and capacitance, thereby widening the stress wave pulse width and achieving medium strain rate loading under electromagnetic loading. Furthermore, this invention can perform material mechanics experiments at low, medium, and high strain rates using a single device, avoiding the influence of size effects from different specimen styles and sizes on the results.

Description

Technical Field

[0001] This invention relates to the field of materials mechanics testing devices, specifically a loading device and loading method for testing the mechanical properties of materials under wide strain rate loading. Background Technology

[0002] In the testing of mechanical properties of materials, strain rate is one of the main factors affecting mechanical properties. Therefore, to fully understand the mechanical properties of materials, it is necessary to conduct test experiments at different strain rates.

[0003] Low strain rate experiment (10 -5 ~10 0 s -1 The quasi-static test, or quasi-static test, can be performed on an electronic universal testing machine as specified in GB / T 16825.1. According to GB / T 228.1-2021 Metallic materials, tensile testing—Part 1: Test methods at room temperature—the cross-section of the specimen in the quasi-static room temperature tensile test can be circular, rectangular, polygonal, or annular. Specific dimensions for different specimen types are also specified. GB / T 7314-2017 Metallic materials, compression test at room temperature, specifies that in the quasi-static room temperature compression test, the specimen can be cylindrical, square prism, rectangular plate, or a plate with lugs. However, when the strain rate exceeds 10 s⁻¹… -1 In quasi-static tests, the force sensor used will cause serious interference to the force signal due to multiple reflections of the wave.

[0004] Medium strain rate experiment (10) 0 ~10 2 s -1 The tests were performed using a high-speed servo hydraulic testing machine. For example, in the article "Mechanical Properties and Constitutive Relationship of 2024-T42 Aluminum Alloy at Low and Medium Strain Rates" published by Zhang Yu et al. in the second issue of Vibration and Shock in 2020 (pp. 249-254), quasi-static, low and medium strain rate tensile tests were conducted using an electronic universal testing machine and a high-speed hydraulic servo material testing machine, obtaining stress-strain curves at different strain rates. In the experiment, from 0.1 to 100 s... -1 The strain rate test used a dog bone-shaped specimen with a gauge length of 50 mm and a duration of 500 s. -1A dog-bone-shaped specimen with a gauge length of 20 mm was used. In patent application number CN201810047039.7, Northwestern Polytechnical University proposed an electromagnetic loading method for medium strain rate tension / compression rod loading experiments, capable of achieving uniaxial tension or compression loading at medium strain rates. However, some problems still exist when using a servo testing machine for medium strain rate experiments. For example, Bai Chunyu et al., in their article "Test Method for Key Parameters of Dynamic Tension of Materials at Medium Strain Rates" published in the journal Explosion and Shock in 2015, Vol. 4, pp. 507-512, mentioned that during medium strain rate experiments using a high-speed servo hydraulic testing machine, when the tensile speed exceeds 1 m / s or the strain rate is greater than 20 s... -1 During testing, the tensile load measured by the load sensor on the testing machine exhibits severe oscillations in the plastic section, which masks the true mechanical behavior of the material during dynamic tensile testing, making it impossible to obtain key material parameters such as yield strength and tensile strength. In patent application number 201810047039.7, Northwestern Polytechnical University proposed a medium strain rate tension-compression bar loading test method. This method can achieve medium strain rate, but the outer diameter and number of turns of the main coil of the stress wave loading gun used in it are 3 to 5 times that of the ordinary Hopkinson bar loading device. The device is more complex and costly, making mass production impossible.

[0005] High strain rate experiment (10 2 ~10 4 s -1 The test is conducted using a Hopkinson bar apparatus. GB / T 30069.1-2013, "Metallic materials, high strain rate tensile testing—Part 1: Elastic bar systems," specifies the use of two types of dog-bone specimens in high strain rate tensile tests and provides recommendations on the reference gauge length and transition length. GB / T 34108-2017, "Metallic materials, high strain rate compression testing at room temperature," specifies the use of cylindrical specimens in high strain rate compression tests. GB / T 32967.1-2016, "Metallic materials, high strain rate torsion testing—Part 1: Room temperature testing," specifies the use of cylindrical flanged thin-walled circular tube specimens or hexagonal flanged thin-walled circular tube specimens in high strain rate torsion tests.

[0006] As can be seen from the above, different types of specimens are required for experiments at different strain rates. While the same type of specimen can be used for both low and high strain rate experiments, the dimensions specified in national standards differ. Experimental results obtained using specimens of different types and sizes often exhibit a certain degree of error, known as the size effect, and therefore are not comparable.

[0007] For example, in their article "Plasticity of Ultrafine-Grained Materials under Complex Stress State" published in the Journal of Materials Science and Engineering, Vol. 5, 2015, Gu Yanglin et al. conducted tensile tests on ultrafine-grained copper and coarse-grained copper using a w+bLFM20KN tensile testing machine with flat plate specimens and notched flat plate specimens. The results showed that when using flat plate specimens, the elongation of the two materials differed by 15%, while when using notched flat plate specimens, the difference between the two materials was only 10%.

[0008] Meanwhile, some problems still arose even when using the same equipment. In November 2007, the Chinese Explosion Mechanics Experimental Technology Professional Group organized a comparative activity of conventional SHPB test results. The professional group pre-selected the same bar stock and distributed it to members of five different units, requiring them to arrange specimen processing and conduct experimental tests according to their respective SHPB specifications. The average strain rate given by each unit was 1500 s⁻¹. -1 The stress-strain curves obtained varied considerably among different organizations, especially in the initial loading portion of the experimental curves. The study found that, in addition to size effects caused by different specimens, data obtained from measurements taken by different machines under the same conditions could also differ.

[0009] This means that it is very important to establish a device that can perform wide strain rate experiments using the same type of specimen.

[0010] In invention publication CN103994922A, a novel loading gun structure is proposed. This structure can generate both tensile and compressive waves and can also shape the waveform using traditional shaping methods. In invention patent 201510051071, a main coil structure and usage method for an electromagnetic experimental device are proposed to improve the amplitude and pulse width variation range generated by the electromagnetic experimental device. These two invention patents are only applicable to high strain rate loading and cannot achieve low or medium strain rate loading. Based on the aforementioned inventions, this invention innovatively proposes a set of experimental devices and methods for achieving a wide strain rate range. Summary of the Invention

[0011] To overcome the shortcomings of the narrow strain rate range in existing technologies, this invention proposes an experimental apparatus and method for measuring the mechanical properties of materials with a wide strain rate range.

[0012] The experimental apparatus for measuring the wide strain rate mechanical properties of materials proposed in this invention includes a capacitor charger, a coded servo electric actuator, an electric cylinder, a coaxial connector, two stress wave loading guns, an incident rod, a transmission rod, and a slide rail. The two stress wave loading guns are a first stress wave loading gun and a second stress wave loading gun, respectively, located at opposite ends of the slide rail. The transmission rod is installed inside the first stress wave loading gun, and the incident rod is installed inside the second stress wave loading gun. A sample is placed between the adjacent end faces of the transmission rod and the incident rod. The coded servo electric actuator, electric cylinder, and reducer are arranged from the outside inwards on the slide rail, located outside the first stress wave loading gun, with a coaxial connector between the electric cylinder and the transmission rod. The first positive output line of the capacitor charger is connected to the positive line of the first stress wave loading gun, and the second positive output line of the capacitor charger is connected to the second stress wave loading gun. The input terminal of the capacitor charger is connected to the output terminal of the power supply. A 90uH inductor is connected in series in the capacitor charger to achieve medium strain rate loading.

[0013] The capacitor charger consists of 10 capacitors with a rated voltage of 5000V and a rated capacitance of 4mF, and 1 inductor with a rated capacitance of 90uH.

[0014] During a low-strain-rate uniaxial compression test, the end face of the transmission rod is coaxially fitted with the end face of the reducer. During a low-strain-rate uniaxial tensile test, the end face of the transmission rod is connected to the end face of the reducer via a coaxial connector.

[0015] When performing uniaxial compression tests at medium or high strain rates, the end face of the incident rod does not need to be connected to the flange. When performing uniaxial tensile tests at medium or high strain rates, the end face of the incident rod is connected to the flange.

[0016] During low strain rate experiments, the two stress wave loading guns serve as supports and stabilizers, without applying any load. The control system is connected to the servo electric actuator via signal control lines, and also to the capacitor charger via signal control lines. The loading speed of the servo electric actuator is set by the control system, and the electric cylinder pushes the transmission rod to load the sample.

[0017] The experimental apparatus proposed in this invention for measuring the mechanical properties of materials across a wide range of strain rates includes uniaxial compression loading experiments at low strain rates, uniaxial compression loading experiments at medium strain rates, and uniaxial compression loading experiments at high strain rates.

[0018] The specific process is as follows:

[0019] Step 1: Arrange the equipment and install the sample.

[0020] When performing a uniaxial compression loading test with a low strain rate, the specimen is mounted between the incident rod and the transmission rod.

[0021] When conducting uniaxial compression loading experiments with medium strain rates and high strain rates, the loading end face of the first stress wave loading gun is coaxially and tightly fitted with the end face of the transmission rod away from the specimen, and the specimen is installed between the incident rod and the transmission rod.

[0022] Step 2: Attach the strain gauges.

[0023] Step 3, set parameters:

[0024] When conducting a uniaxial compression loading experiment with low strain rate, the PLC circuit in the control system is set to the electric cylinder loading speed of 0.2 mm / s.

[0025] When conducting a uniaxial compression loading experiment with medium strain rate, the PLC circuit in the control system is set with a capacitance of 40mF and a voltage of 1000V.

[0026] When conducting a high strain rate uniaxial compression loading experiment, the PLC circuit in the control system is set with a capacitance of 4mF and a voltage of 1000V.

[0027] Step 4: Loading:

[0028] When conducting a low strain rate uniaxial compression loading experiment, press the discharge button on the touch screen in the control system to make the electric cylinder start pushing the transmission rod at the speed set in step 3, complete one loading, and collect the required data through the strain gauge.

[0029] When conducting a uniaxial compression loading experiment with medium strain rate, pressing the discharge button on the touch screen in the control system will cause the second stress wave loading gun to discharge, pushing the incident rod to complete one loading cycle, and collecting the required data through strain gauges.

[0030] When performing uniaxial compression loading experiments at high strain rates, the loading process is the same as that for uniaxial compression at medium strain rates.

[0031] Step 5. Data Processing:

[0032] When performing a uniaxial compression loading experiment with low strain rate, voltage signals are acquired through the strain gauges and transmitted to the data acquisition unit 9 via a Wheatstone bridge for recording and storage.

[0033] The data acquisition unit records and stores the voltage change signal V of the bridge arm of the Wheatstone bridge. V is measured by the strain gauge on the transmission rod. The voltage change signal of the bridge arm recorded by the data acquisition unit 9 is converted into a strain signal on the transmission rod using formula (1). The specific expression of the formula is as follows:

[0034]

[0035] Where ε is the strain signal of the transmission rod during the uniaxial compression loading experiment, U is the supply voltage of the Wheatstone bridge during the uniaxial compression loading experiment, k is the strain gauge sensitivity coefficient during the uniaxial compression loading experiment, and V is the bridge arm voltage change signal of the Wheatstone bridge recorded by the data acquisition device 9 during the uniaxial compression loading experiment.

[0036] The strain signal ε of the transmission rod during the uniaxial compression loading experiment is obtained using formula (1).

[0037] The stress σ in the effective test section of the specimen during uniaxial compression loading test S for:

[0038]

[0039] Where, σ S E represents the effective test section stress of the specimen during a uniaxial compression loading test. T A represents the elastic modulus of the transmission rod during a uniaxial compression loading experiment. T Let A be the cross-sectional area of ​​the transmission rod during the uniaxial compression loading experiment. S This refers to the cross-sectional area of ​​the effective test section of the specimen during a uniaxial compression loading experiment.

[0040] The strain ε of the specimen during the uniaxial compression loading experiment was measured using the digital image correlation method. S .

[0041] The strain ε of the specimen during uniaxial compression loading test S The horizontal axis represents the stress σ in the effective test section of the specimen during a uniaxial compression loading test. S Plot the stress-strain curve of the specimen on the vertical axis, thus completing the uniaxial compression experiment at low strain rate.

[0042] When conducting uniaxial compression loading experiments at medium strain rates, the data processing procedure is the same as that for uniaxial compression at low strain rates.

[0043] When conducting uniaxial compression loading experiments with high strain rates, the data processing procedure is the same as that for uniaxial compression with low strain rates.

[0044] The method for measuring the mechanical properties of materials across a wide strain rate using the experimental apparatus proposed in this invention also includes uniaxial tensile loading experiments at low strain rates, uniaxial tensile loading experiments at medium strain rates, and uniaxial tensile loading experiments at high strain rates.

[0045] The specific process is as follows:

[0046] Step 1: Arrange the equipment and install the sample.

[0047] When performing a uniaxial tensile loading test at a low strain rate, a coaxial coupling is installed between the transmission rod and the reducer, with the reducer end face and the transmission rod end face connected to the two ends of the coaxial coupling, respectively. The specimen is then mounted between the incident rod and the transmission rod.

[0048] When conducting uniaxial tensile loading tests at medium strain rates and high strain rates, the incident rod is passed through the second stress wave loading gun, and the flange is threaded onto the incident rod. The loading end face of the second stress wave loading gun is coaxially and tightly fitted with the flange end face. A specimen is installed between the incident rod and the transmission rod.

[0049] Step 2: Attach the strain gauges.

[0050] Step 3, set parameters:

[0051] When conducting a uniaxial tensile loading test with a low strain rate, the loading speed is set. This loading speed is determined by the PLC circuit in the control system, which sets the electric cylinder loading speed to 0.2 mm / s.

[0052] When conducting a uniaxial tensile loading experiment with medium strain rate, the PLC circuit in the control system is set with a capacitance of 40mF and a voltage of 1000V.

[0053] When conducting a high strain rate uniaxial tensile loading experiment, the PLC circuit in the control system is set with a capacitance of 4mF and a voltage of 1000V.

[0054] Step 4: Loading:

[0055] When performing a low strain rate uniaxial tensile loading experiment, press the discharge button on the touch screen in the control system. The electric cylinder will start to push the transmission rod at the set loading speed to complete one loading cycle, and the required data will be collected through the strain gauge.

[0056] When conducting a uniaxial tensile loading experiment with medium strain rate, pressing the discharge button on the touch screen in the control system will cause the second stress wave loading gun to discharge, pushing the incident rod to complete one loading cycle, and collecting the required data through strain gauges.

[0057] When performing a high strain rate uniaxial tensile loading experiment, the loading process is the same as that for a medium strain rate uniaxial compression experiment.

[0058] Step 5. Data Processing:

[0059] When performing a low strain rate uniaxial tensile loading experiment, the voltage signal is acquired through the strain gauge and transmitted to the data acquisition unit 9 via a Wheatstone bridge for recording and storage.

[0060] The data acquisition unit 9 records and stores the voltage change signal V′ of the bridge arm of the Wheatstone bridge during the uniaxial tensile loading experiment. V′ is measured by the strain gauge on the transmission rod. The voltage change signal of the bridge arm during the uniaxial tensile loading experiment recorded by the data acquisition unit 9 is converted into a strain signal on the transmission rod using formula (1-1). The specific expression of the formula is as follows:

[0061]

[0062] Wherein, ε′ is the strain signal of the transmission rod during the uniaxial tensile loading experiment, U′ is the supply voltage of the Wheatstone bridge during the uniaxial tensile loading experiment, k′ is the strain gauge sensitivity coefficient during the uniaxial tensile loading experiment, and V′ is the bridge arm voltage change signal of the Wheatstone bridge during the uniaxial tensile loading experiment recorded by data acquisition device 9.

[0063] The strain signal ε′ of the transmission rod during the uniaxial tensile loading experiment is obtained using formula (1-1).

[0064] Stress σ in the effective test section of the specimen S ′:

[0065]

[0066] Where, σ S E′ represents the effective test section stress of the specimen during a uniaxial tensile loading test. T Let A′ be the elastic modulus of the transmission rod during a uniaxial tensile loading test. T Let A′ be the cross-sectional area of ​​the transmission rod during the uniaxial tensile loading test. S This refers to the cross-sectional area of ​​the effective test section of the specimen during a uniaxial tensile loading test.

[0067] The strain ε of the specimen was measured using digital image correlation. S ′.

[0068] The strain ε of the specimen during a uniaxial tensile loading test S The horizontal axis represents the stress σ in the effective test section of the specimen during a uniaxial tensile loading test. S Plot the stress-strain curve of the specimen on the vertical axis.

[0069] This completes the low strain rate uniaxial compression test.

[0070] When conducting uniaxial compression loading experiments at medium strain rates, the data processing procedure is the same as that for uniaxial compression at low strain rates.

[0071] When conducting uniaxial compression loading experiments with high strain rates, the data processing procedure is the same as that for uniaxial compression with low strain rates.

[0072] This invention achieves low strain rate loading through motor propulsion and achieves medium and high strain rate loading through the loading gun proposed in publication number CN103994922A.

[0073] This invention can achieve 10 -3 s -1 ~10 3 s -1 Mechanical property testing experiments within the strain rate range can solve the problems mentioned in the background technology.

[0074] The main challenge in this invention is achieving a medium strain rate. To achieve this, researchers from various countries have developed different instruments, but all have struggled to precisely control the strain rate generated by the device. One researcher modified a Hopkinson bar apparatus, enabling four sets of medium strain rate experiments. The Hopkinson bar uses an air gun to launch an impact bar at high speed, which collidees coaxially with the incident bar to generate an incident pulse. The drawback of this method is that, because the installation position of the impact bar in the air gun is not exactly the same each time it is launched, and the correlation between impact velocity and air pressure is difficult to determine, it is impossible to accurately control the amplitude of the incident wave, requiring multiple experiments to obtain the desired strain rate. Secondly, for experiments with a large strain rate range, due to air pressure limitations, it is necessary to change the length of the impact bar to obtain different strain rates.

[0075] This invention improves upon Hopkinson bars using electromagnetic riveting technology to achieve a medium strain rate. There are two options for achieving this: 1. increase the inductance; 2. increase the capacitance. However, due to practical limitations such as manufacturing, installation, transportation space requirements, and maintenance, the capacitance cannot be increased indefinitely. Research shows that if the withstand voltage is capped at 1000V, the maximum capacitance currently available for a single capacitor is 40mF. Therefore, given a maximum capacitance of 40mF, an inductance is still required. However, the inductance value must be precisely determined. If the inductance is too small, a medium strain rate cannot be achieved, and the current in the circuit will oscillate. If the inductance is too large, it will lengthen the stress wave rise edge, causing the sample to fail before stress equilibrium.

[0076] In determining the inductance value, this invention:

[0077] The working principle of the stress wave loading gun used is simplified to an RLC series circuit. Assume the capacitor is already charged before switch S is closed, its voltage is U0, and there is no current in the inductor. After the circuit is switched, in Figure 9 Under the reference current direction shown, according to Kirchhoff's voltage law, we have:

[0078] -uc+uR+uL=0 (3)

[0079] and Substituting into the KVL equation, we get:

[0080]

[0081] This is a second-order linear homogeneous differential equation with constant coefficients, and its characteristic equation is:

[0082] LCp² + RCp + 1 = 0 (5)

[0083] Its root is:

[0084]

[0085]

[0086] In the formula:

[0087] — This is called the circuit's attenuation constant, with units of 1 Ω·cm.

[0088] —This is called the natural angular frequency of the circuit, also known as the resonant angular frequency, and its unit is rad / s. The characteristic roots p1 and p2 are also called the natural frequencies or natural frequencies of the circuit.

[0089] The general solution of the differential equation is:

[0090]

[0091] Among them, the integration constants A1 and A2 can be determined by the initial condition u. c (0 + )and Sure.

[0092] Taking the first derivative of equation (8), we get:

[0093]

[0094] The initial conditions are:

[0095] u c (0 + )=u c (0 - )=U0 (10)

[0096]

[0097] so:

[0098]

[0099] Solving equation (12) simultaneously, we can obtain the constants A1 and A2 as follows:

[0100]

[0101] Equation (13-1) is derived based on given initial conditions. Different initial conditions will yield different results. Substituting equation (13-1) into equations (6) and (7) yields the desired solution. The following will explain the solution based on the δ within the square root of expressions (6) and (7) for p1 and p2. 2 With ω 2 The relative sizes of the two items are discussed in three cases.

[0102] Ⅰ Non-oscillating discharge process δ 2 >ω 2 Right now

[0103] In this case, the two characteristic roots are not equal to p1 and p2, and are negative real roots. The capacitor voltage is

[0104]

[0105] The current is:

[0106]

[0107] II. Oscillating discharge process: δ 2 <ω 2 Right now During the oscillating discharge process, the two characteristic roots p1 and p2 are a pair of conjugate complex roots. This can be rewritten as...

[0108]

[0109] In the formula:

[0110]

[0111] It is called the free oscillation angular frequency of the circuit. δ, ω0, and ω satisfy the relationship of a right triangle. According to Euler's formula, the capacitor voltage can also be obtained, and then according to equation (12-1), the current in this case can be calculated as:

[0112]

[0113] (3)δ 2 =ω 2 Right now (Oscillating discharge process)

[0114] exist Under the condition that the two characteristic roots are To obtain the solution in this case, the solution for the non-oscillating discharge process can still be used. Let u c For example, from equation (14), we can obtain Then let p1→p2=-δ and take the limit. And by L'Hôpital's rule, we can obtain:

[0115] uc =U0e -δt (1+δt) (19)

[0116] Therefore:

[0117]

[0118] From the above discussion, it can be seen that in an RLC series circuit, when the resistance is greater than or equal to... When the resistance is less than a certain value, the response in the circuit is non-oscillatory; when the resistance is less than a certain value, the response becomes oscillatory. Therefore, it is also called... This is the critical resistance. It is also commonly referred to as... This situation is called the under-damped situation; This situation is called an over-damped situation;

[0119] The case where R=0 is called the critically damped case; while the case where R=0 is called the undamped case, the response waveform is a constant amplitude oscillation, and the free oscillation period is... With inherent oscillation period They are equal, that is, T = T0

[0120] Figure 10 The curves showing the discharge current versus time under both overdamped and underdamped conditions are presented. The discharge process in the critically damped case exhibits a similar pattern to that in the overdamped case, and since it is less frequently encountered in practical applications, it is not shown here. Taking U0 = 1000V, L = 50uH, and C = 40mF, the critical resistance of the system can be calculated to be 63.25mΩ. The black curve i1 in the figure corresponds to a resistance of 70mΩ, satisfying the overdamped condition; the red curve i2 corresponds to the underdamped oscillation condition, with a resistance of 10mΩ.

[0121] As can be seen from the figure, under the overdamped condition, a non-oscillatory discharge occurs, with the current i1 gradually increasing from zero, and after reaching a certain value (at t = t), it exhibits a certain discharge pattern. m The value (maximum at time t) then decays until it becomes zero, indicating that the value is within the range of 0 to t. m Within a time frame, the inductor absorbs energy and stores it in the magnetic field, t m Then it is released again. And the capacitor voltage u C As the voltage gradually decays from U0 to zero, the capacitor continuously releases the electric field energy it originally stored. Throughout this process, the resistor constantly consumes energy until the energy originally stored in the circuit is exhausted. Under underdamped conditions, the circuit exhibits damped oscillation characteristics, periodically changing direction throughout the process, and the energy storage elements L and C also periodically exchange energy.

[0122] To achieve the medium strain rate condition, a crucial requirement for the applied stress wave is a sufficiently long pulse width. As the preceding analysis shows, the stress wave is primarily generated by the electromagnetic repulsion between the induction coil and the active coil; therefore, a longer period of discharge current is desirable. Under underdamped conditions, the discharge current oscillation period is:

[0123]

[0124] The resistance in the discharge circuit is usually very small. In actual operation, a single-phase diode is used to cut off the reverse current. Therefore, the pulse width of the discharge current can be approximated by equation (21). It is clear from this that the two circuit parameters that have the greatest impact on the current pulse width are the capacitance and inductance values.

[0125] Therefore, the present invention selects a capacitance value of 40mF. When the capacitance value reaches 40mF, in order to achieve a pulse width of 5ms, the required inductance can be calculated to be 90uH according to equations (6), (7) and (15).

[0126] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0127] 1. The experimental apparatus for measuring the mechanical properties of materials under a wide range of strain rates proposed in this invention can realize material mechanics experiments under low strain rate, medium strain rate and high strain rate respectively, and can avoid the influence of size effect of different styles and sizes of specimens on the result error.

[0128] 2. By using electromagnetic loading, the strain rate of the material within a controllable range (10) was controlled. 0 s -1 ~10 2 s -1 This technology, capable of effective measurement under electromagnetic loading, fills a gap in both domestic and international research on servo hydraulic testing machines and Hopkinson bar loading tests. By changing the circuit inductance, the stress wave pulse width can be increased, thereby achieving medium strain rate loading under electromagnetic loading. Figure 7 As shown, under the loading conditions of a 40mF capacitor and a 1000V voltage, the stress wave pulse width reaches 6ms and the strain rate is 55s. -1 This allows for medium strain rate loading. The main breakthrough of this invention is the addition of a 90uH inductor in series in the circuit to increase the stress wave pulse width, thereby achieving medium strain rate loading. Attached Figure Description

[0129] Figure 1 This is a schematic diagram of the compression experiment of the present invention.

[0130] Figure 2 This is a schematic diagram of the tensile test of the present invention.

[0131] Figure 3 This is a three-dimensional structural diagram of the compression experiment of the present invention.

[0132] Figure 4 for Figure 3 Top view.

[0133] Figure 5 This is a three-dimensional structural diagram of the tensile test of the present invention.

[0134] Figure 6 for Figure 5 Top view.

[0135] Figure 7 This is a time-stress curve under medium strain rate loading.

[0136] Figure 8 The time-strain rate curve is shown under medium strain rate loading.

[0137] Figure 9 This is the zero-input response diagram of an RLC circuit.

[0138] Figure 10 The discharge current curves are shown for overdamped and underdamped conditions.

[0139] Figure 11 This is a schematic diagram of a flange.

[0140] In the diagram: 1. Power supply; 2. Capacitor charger; 3. Codeable servo electric driver; 4. Electric cylinder; 5. Servo motor reducer; 6. Coaxial cable; 7. First stress wave loading gun; 8. Control system; 9. Data acquisition unit; 10. Incident rod; 11. Transmission rod; 12. Strain gauge; 13. Flange; 14. Slide rail; 15. Specimen; 16. Second stress wave loading gun; 17. Detailed Implementation

[0141] Example 1

[0142] This embodiment is an experimental apparatus that can realize wide strain rate loading. The wide strain rate is used to carry out uniaxial tensile or uniaxial compression experiments on different materials at low, medium or high strain rates.

[0143] The experimental apparatus for uniaxial tensile or uniaxial compression loading under wide strain rates includes a power supply 1, a capacitor charger 2, a coded servo electric driver 3, an electric cylinder 4, a servo motor reducer 5, a coaxial connector 6, a first stress wave loading gun 7, a second stress wave loading gun 16, a control system 8, a data acquisition unit 9, an incident rod 10, a transmission rod 11, a strain gauge 12, a flange 13, and a slide rail 14.

[0144] The two stress wave loading guns are the first stress wave loading gun 7 and the second stress wave loading gun 16.

[0145] Two stress wave loading guns are located at opposite ends of the slide rail 14. A transmission rod 11 is conventionally mounted inside the first stress wave loading gun 7, and an incident rod 10 is conventionally mounted inside the second stress wave loading gun 16. A sample 15 is positioned between the adjacent end faces of the transmission rod and the incident rod. The coded servo electric drive 3, electric cylinder 4, and reducer 5 are arranged from the outside inwards on the slide rail, located outside the first stress wave loading gun, and a coaxial coupling 6 is provided between the electric cylinder and the transmission rod 11.

[0146] The push rod, transmission rod, and incident rod are coaxial.

[0147] Two strain gauges 12 are symmetrically attached to the circumferential surface at half the length of the incident rod 10; two strain gauges 12 are also symmetrically attached to the circumferential surface at half the length of the transmission rod 11. Each strain gauge is connected to the data acquisition unit 9.

[0148] The capacitor charger consists of ten capacitors with a rated voltage of 5000V and a rated capacitance of 4mF, and one 90uH inductor. The capacitor charger 2 has two positive output lines. The first positive output line is connected to the positive line of the first stress wave loading gun 7, and the second positive output line is connected to the second stress wave loading gun. The input terminal of the capacitor charger 2 is connected to the output terminal of the power supply 1.

[0149] To achieve integrated loading, the same stress wave loading gun is needed for both medium and high strain rate loading. However, the stress wave loading gun device proposed in publication CN103994922A does not meet the inductance requirement. Therefore, to use the same stress wave loading gun, a 90uH inductor needs to be connected in series in the capacitor charger 2 to achieve medium strain rate loading.

[0150] During a low-strain-rate uniaxial compression test, the end face of the incident rod 10 is coaxially fitted with the end face of the reducer. During a low-strain-rate uniaxial tensile test, the end face of the incident rod is connected to the end face of the reducer via a coaxial connector.

[0151] When performing uniaxial compression tests at medium or high strain rates, the end face of the incident rod does not need to be connected to flange 13. When performing uniaxial tensile tests at medium or high strain rates, the end face of the incident rod is connected to flange 13 via threads.

[0152] Both the power supply 1 and the capacitor charger 2 use the power supply part of the electromagnetic riveting device mentioned in the existing invention application number 201510956545.4.

[0153] The programmable servo motor uses a commercially available Jemcom 400 servo electric drive.

[0154] The electric cylinder is a commercially available HE100-3000 stroke electric cylinder.

[0155] The reducer is an XWD6-11-17-23-35-43-59-71-7.5KW cycloidal pinwheel reducer.

[0156] The coaxial coupling is a commercial rigid plum blossom coupling.

[0157] During the low strain rate experiment, the two stress wave loading guns serve as supports and fixation devices, without applying any load. The control system 8 is connected to the servo electric drive 3 via a signal control line, and simultaneously connected to the capacitor charger 2 via the same signal control line. The loading speed of the servo electric drive is set via the control system 8, and the electric cylinder pushes the transmission rod, thereby loading the sample 15.

[0158] Example 2

[0159] This embodiment describes a method for conducting a wide strain rate uniaxial compression loading experiment using the aforementioned wide strain rate loading device.

[0160] The specific process of the wide strain rate uniaxial compression loading experiment includes low strain rate uniaxial compression loading experiment, medium strain rate uniaxial compression loading experiment and high strain rate uniaxial compression loading experiment.

[0161] The specific process is as follows:

[0162] Step 1: Arrange the equipment and install the sample.

[0163] When performing a low-strain-rate uniaxial compression loading test, a specimen 15 is installed between the incident rod 10 and the transmission rod 11. The specimen is made of 2024 aluminum alloy, and its shape is dumbbell-shaped with a smooth cylinder in the middle and threaded connecting sections at both ends. The effective test section of the specimen has a diameter of 3 mm and a length of 3 mm.

[0164] During a uniaxial compression loading test at medium strain rate, the loading end face of the first stress wave loading gun 7 is coaxially and tightly fitted with the end face of the transmission rod 11, and a specimen 15 is installed between the incident rod 10 and the transmission rod 11. The specimen is made of 2024 aluminum alloy, and its shape is dumbbell-shaped with a smooth cylinder in the middle and externally threaded connecting sections at both ends. The effective test section of the specimen has a diameter of 3 mm and a length of 3 mm.

[0165] When conducting uniaxial compression loading experiments at high strain rates, the arrangement and installation process is the same as when conducting uniaxial compression loading experiments at medium strain rates.

[0166] Step 2: Attach the strain gauges.

[0167] Two strain gauges are symmetrically attached to the circumferential surface of the transmission rod 11 at half its length. Two more strain gauges are symmetrically attached to the circumferential surface of the incident rod 10 at half its length. The measurement direction of the strain gauges is parallel to the axis of the incident rod, and their resistance is 1000 ohms. The sensitivity is 1.98. The leads of each strain gauge are connected to a Wheatstone bridge via a double-core shielded cable; the output signal line of the Wheatstone bridge is connected to the input section of a data acquisition unit to record the voltage signal. The Wheatstone bridge is powered by 30V.

[0168] Step 3: Set the loading speed:

[0169] When conducting a uniaxial compression loading experiment with low strain rate, the loading speed of the electric cylinder 4 is set in the PLC circuit of the control system 8. In this embodiment, the speed is set to 0.2 mm / s.

[0170] When conducting a uniaxial compression loading experiment with medium strain rate, the PLC circuit in control system 8 is set with a capacitance of 40mF and a voltage of 1000V.

[0171] When conducting a high strain rate uniaxial compression loading experiment, the PLC circuit in control system 8 is set with a capacitance of 4mF and a voltage of 1000V.

[0172] Step 4: Loading:

[0173] When performing a low strain rate uniaxial compression loading experiment, press the discharge button on the touch screen in the control system 8 to make the electric cylinder 4 start pushing the transmission rod 11 at the speed set in step 3 to complete one loading and collect the required data through the strain gauge.

[0174] When conducting a uniaxial compression loading experiment with medium strain rate, pressing the discharge button on the touch screen in the control system 8 will cause the second stress wave loading gun 16 to discharge, pushing the incident rod 10 to complete one loading cycle, and collecting the required data through the strain gauge.

[0175] When performing a uniaxial compression loading experiment with a high strain rate, the loading process is the same as that for a uniaxial compression loading experiment with a medium strain rate.

[0176] Step 5. Data Processing:

[0177] When performing a uniaxial compression loading experiment with low strain rate, voltage signals are acquired through the strain gauges and transmitted to the data acquisition unit 9 via a Wheatstone bridge for recording and storage.

[0178] The data acquisition unit 9 records and stores the voltage change signal V of the bridge arm of the Wheatstone bridge. V is measured by the strain gauge on the transmission rod. The voltage change signal of the bridge arm recorded by the data acquisition unit 9 is converted into a strain signal on the transmission rod using formula (1). The specific expression of the formula is as follows:

[0179]

[0180] Where ε is the strain signal of the transmission rod during the uniaxial compression loading experiment, U is the supply voltage of the Wheatstone bridge during the uniaxial compression loading experiment, k is the strain gauge sensitivity coefficient during the uniaxial compression loading experiment, and V is the bridge arm voltage change signal of the Wheatstone bridge recorded by the data acquisition device 9 during the uniaxial compression loading experiment. In this embodiment, the supply voltage of the Wheatstone bridge is 30V, and the strain gauge sensitivity coefficient k is 1.92.

[0181] The strain signal ε of the transmission rod is obtained through formula (1).

[0182] The stress σ in the effective test section of the specimen during uniaxial compression loading test S for:

[0183]

[0184] Where, σ S E represents the effective test section stress of the specimen during a uniaxial compression loading test. T A represents the elastic modulus of the transmission rod during a uniaxial compression loading experiment. T Let A be the cross-sectional area of ​​the transmission rod during the uniaxial compression loading experiment. S This refers to the cross-sectional area of ​​the effective test section of the specimen during a uniaxial compression loading experiment.

[0185] The strain ε of the specimen during the uniaxial compression loading experiment was measured using conventional digital image correlation techniques. S .

[0186] The strain ε of the specimen during uniaxial compression loading test S The horizontal axis represents the stress σ in the effective test section of the specimen during a uniaxial compression loading test. S Plot the graph on the vertical axis to obtain the stress-strain curve of the specimen during the uniaxial compression loading experiment. This completes the uniaxial compression loading experiment at low strain rate.

[0187] When conducting uniaxial compression loading experiments at medium strain rates, the data processing procedure is the same as that for uniaxial compression at low strain rates.

[0188] When conducting uniaxial compression loading experiments with high strain rates, the data processing procedure is the same as that for uniaxial compression with low strain rates.

[0189] Example 3

[0190] This embodiment describes a method for conducting a wide strain rate uniaxial tensile loading experiment using the aforementioned wide strain rate loading device.

[0191] The specific process of the wide strain rate uniaxial tensile loading experiment includes low strain rate uniaxial tensile loading experiment, medium strain rate uniaxial tensile loading experiment and high strain rate uniaxial tensile loading experiment.

[0192] The specific process is as follows:

[0193] Step 1: Arrange the equipment and install the sample.

[0194] During a low-strain-rate uniaxial tensile loading test, a coaxial connector 6 is installed between the transmission rod 11 and the reducer 5. The two ends of the coaxial connector 6 are connected to the end faces of the reducer 5 and the transmission rod, respectively. A specimen 15 is installed between the incident rod 10 and the transmission rod 11. The specimen is made of 2024 aluminum alloy, has a dumbbell shape, a smooth cylinder in the middle, and threaded connecting sections at both ends. The effective test section of the specimen has a diameter of 3 mm and a length of 3 mm.

[0195] During a uniaxial tensile loading test at medium strain rate, the incident rod 10 is passed through the second stress wave loading gun 16, and the flange 13 is threaded onto the incident rod 10. The loading end face of the second stress wave loading gun 16 is coaxially and tightly fitted with the end face of the flange 13. A specimen 15 is installed between the incident rod 10 and the transmission rod 11. The specimen is made of 2024 aluminum alloy, and its shape is dumbbell-shaped, with a smooth cylinder in the middle and threaded connecting sections at both ends. The effective test section of the specimen has a diameter of 3 mm and a length of 3 mm.

[0196] When conducting a high strain rate uniaxial tensile loading test, the arrangement and installation process is the same as when conducting a medium strain rate uniaxial tensile loading test.

[0197] Step 2: Attach the strain gauges.

[0198] Two strain gauges are symmetrically attached to the circumferential surface of the transmission rod 11 at half its length. Two more strain gauges are symmetrically attached to the circumferential surface of the incident rod 10 at half its length. The measurement direction of the strain gauges is parallel to the axis of the incident rod, and their resistance is 1000 ohms. The sensitivity is 1.98. The leads of each strain gauge are connected to a Wheatstone bridge via a double-core shielded cable; the output signal line of the Wheatstone bridge is connected to the input section of a data acquisition unit to record the voltage signal. The Wheatstone bridge is powered by 30V.

[0199] Step 3, set parameters:

[0200] When conducting a uniaxial tensile loading test with a low strain rate, the loading speed is set. This loading speed is determined by the PLC circuit in the control system 8, which sets the loading speed of the electric cylinder 4. In this embodiment, the speed is set to 0.2 mm / s.

[0201] When conducting a uniaxial tensile loading experiment with medium strain rate, the PLC circuit in control system 8 is set with a capacitance of 40mF and a voltage of 1000V.

[0202] When conducting a high strain rate uniaxial tensile loading experiment, the PLC circuit in control system 8 is set with a capacitance of 4mF and a voltage of 1000V.

[0203] Step 4: Loading:

[0204] When performing a low strain rate uniaxial tensile loading experiment, press the discharge button on the touch screen in the control system 8, and the electric cylinder will start to push the transmission rod at the set loading speed to complete one loading cycle, and collect the required data through the strain gauge.

[0205] When conducting a uniaxial tensile loading experiment with medium strain rate, pressing the discharge button on the touch screen in the control system 8 will cause the second stress wave loading gun 16 to discharge, pushing the incident rod 10 to complete one loading cycle, and collecting the required data through the strain gauge.

[0206] When performing a uniaxial tensile loading experiment with a high strain rate, the loading process is the same as that for a uniaxial tensile loading experiment with a medium strain rate.

[0207] Step 5. Data Processing:

[0208] When performing a low strain rate uniaxial tensile loading experiment, the voltage signal is acquired through the strain gauge and transmitted to the data acquisition unit 9 via a Wheatstone bridge for recording and storage.

[0209] The data acquisition unit 9 records and stores the voltage change signal V of the Wheatstone bridge arm. V is measured by the strain gauge on the transmission rod. The voltage change signal of the bridge arm recorded by the data acquisition unit 9 is converted into a strain signal on the transmission rod using formula (1-1). The specific expression of the formula is as follows:

[0210]

[0211] Wherein, ε′ is the strain signal of the transmission rod during the uniaxial tensile loading experiment, U′ is the supply voltage of the Wheatstone bridge during the uniaxial tensile loading experiment, k′ is the strain gauge sensitivity coefficient during the uniaxial tensile loading experiment, and V′ is the bridge arm voltage change signal of the Wheatstone bridge recorded by the data acquisition device 9 during the uniaxial tensile loading experiment. In this embodiment, the supply voltage of the Wheatstone bridge is 30V, and the strain gauge sensitivity coefficient k′ is 1.92.

[0212] The strain signal ε′ of the transmission rod is obtained by formula (11).

[0213] Stress σ in the effective test section of the specimen S'for:

[0214]

[0215] Where, σ S E′ represents the effective test section stress of the specimen during a uniaxial tensile loading test. T Let A′ be the elastic modulus of the transmission rod during a uniaxial tensile loading test. T Let A′ be the cross-sectional area of ​​the transmission rod during the uniaxial tensile loading test. S This refers to the cross-sectional area of ​​the effective test section of the specimen during a uniaxial tensile loading test.

[0216] The strain ε of the specimen was measured using a conventional digital image correlation (DIR) method. S .

[0217] The strain ε of the specimen during a uniaxial tensile loading test S ′ is the horizontal axis, and σ is the stress σ of the effective test section of the specimen during a uniaxial tensile loading test. S Plot the stress-strain curve of the specimen with ′ as the vertical axis. This completes the low strain rate uniaxial compression loading experiment.

[0218] When conducting uniaxial compression loading experiments at medium strain rates, the data processing procedure is the same as that for uniaxial compression at low strain rates.

[0219] When conducting uniaxial compression loading experiments with high strain rates, the data processing procedure is the same as that for uniaxial compression with low strain rates.

Claims

1. A method for measuring the broad strain rate mechanical properties of a material, characterized in that, This includes uniaxial compression loading experiments with low strain rates, uniaxial compression loading experiments with medium strain rates, and uniaxial compression loading experiments with high strain rates. The specific process is as follows: Step 1: Arrange the equipment and install the samples; When a low strain rate uniaxial compression test is performed, the end face of the transmission rod (11) is coaxially attached to the end face of the reducer; when a low strain rate uniaxial tensile test is performed, the end face of the transmission rod and the end face of the reducer are connected by a coaxial connector. When performing a uniaxial compression test at medium or high strain rates, the end face of the incident rod does not need to be connected to the flange (13); when performing a uniaxial tensile test at medium or high strain rates, the end face of the incident rod is connected to the flange; when performing a uniaxial compression test at low strain rates, the sample (15) is installed between the incident rod (10) and the transmission rod (11). When performing uniaxial compression loading experiments with medium strain rate and high strain rate, the loading end face of the first stress wave loading gun (7) is coaxially and tightly fitted with the end face of the transmission rod away from the sample, and the sample (15) is installed between the incident rod and the transmission rod. Step 2, attach the strain gauges; Step 3, set the parameters; Step 4, load: When performing a low strain rate uniaxial compression loading experiment, press the discharge button on the touch screen in the control system (8) to make the electric cylinder start pushing the transmission rod (11) at the speed set in step 3 to complete one loading and collect the required data through the strain gauge; the PLC circuit in the control system (8) sets the loading speed of the electric cylinder (4) to 0.2 mm / s; When conducting a uniaxial compression loading experiment with medium strain rate, press the discharge button on the touch screen in the control system, the second stress wave loading gun (16) discharges, pushes the incident rod (10), completes one loading, and collects the required data through the strain gauge; the PLC circuit in the control system is set with a capacitance value of 40mf and a voltage value of 1000V. When performing a high strain rate uniaxial compression loading experiment, the loading process is the same as that for medium strain rate uniaxial compression; the PLC circuit in the control system is set with a capacitance of 4mF and a voltage of 1000V. Step 5. Data Processing: When performing a uniaxial compression loading experiment with low strain rate, the voltage signal is collected through the strain gauge and transmitted to the data acquisition unit (9) and recorded and stored through a Wheatstone bridge. The data acquisition device records and stores the voltage change signal V of the bridge arm of the Wheatstone bridge; where V is measured by the strain gauge on the transmission rod; the voltage change signal of the bridge arm recorded by the data acquisition device is converted into the strain signal on the transmission rod by formula (1), the specific expression of which is: (1) Where ε is the strain signal of the transmission rod during the uniaxial compression loading experiment, U is the power supply voltage of the Wheatstone bridge during the uniaxial compression loading experiment, k is the strain gauge sensitivity coefficient during the uniaxial compression loading experiment, and V is the bridge arm voltage change signal of the Wheatstone bridge recorded by the data acquisition device during the uniaxial compression loading experiment. The strain signal ε of the transmission rod during the uniaxial compression loading experiment is obtained using formula (1). The stress σ in the effective test section of the specimen during uniaxial compression loading test S for: Where, σ S E represents the effective test section stress of the specimen during a uniaxial compression loading test. T A represents the elastic modulus of the transmission rod during a uniaxial compression loading experiment. T Let A be the cross-sectional area of ​​the transmission rod during the uniaxial compression loading experiment. S This refers to the effective test section cross-sectional area of ​​the specimen during a uniaxial compression loading test. The strain ε of the specimen during the uniaxial compression loading experiment was measured using the digital image correlation method. S ; The strain ε of the specimen during uniaxial compression loading test S The horizontal axis represents the stress σ in the effective test section of the specimen during a uniaxial compression loading test. S Plot the stress-strain curve of the specimen on the vertical axis, thus completing the uniaxial compression experiment at low strain rate. When conducting uniaxial compression loading experiments at medium strain rates, the data processing procedure is the same as that for uniaxial compression at low strain rates. When conducting uniaxial compression loading experiments with high strain rates, the data processing procedure is the same as that for uniaxial compression with low strain rates.

2. A method for measuring the broad strain rate mechanical properties of a material, characterized in that, This includes uniaxial tensile loading experiments with low strain rates, uniaxial tensile loading experiments with medium strain rates, and uniaxial tensile loading experiments with high strain rates. The specific process is as follows: Step 1: Arrange equipment and install samples: When performing a uniaxial tensile loading test with low strain rate, a coaxial device (6) is installed between the transmission rod (11) and the servo motor reducer (5), with the end faces of the reducer and the transmission rod connected to the two ends of the coaxial device respectively; the sample (15) is installed between the incident rod and the transmission rod. When performing uniaxial tensile loading tests at medium strain rates and high strain rates, the incident rod (10) is passed through the second stress wave loading gun (16), and the flange (13) is assembled with the incident rod by thread; the loading end face of the second stress wave loading gun is coaxially and tightly fitted with the flange end face; the sample is installed between the incident rod and the transmission rod (11). Step 2, attach the strain gauges: Step 3, set parameters: Step 4, load: When performing a low strain rate uniaxial tensile loading test, press the discharge button on the touch screen in the control system (8), and the electric cylinder will start to push the transmission rod at the set loading speed to complete one loading and collect the required data through the strain gauge; set the loading speed; the loading speed is set to 0.2 mm / s in the PLC circuit of the control system (8); When performing a uniaxial tensile loading experiment at a medium strain rate, pressing the discharge button on the touchscreen in the control system discharges the second stress wave loading gun (16), pushes the incident rod (10), completes one loading, and collects the required data through the strain gauge; the PLC circuit in the control system is set with a capacitance of 40mF and a voltage of 1000V; when performing a uniaxial tensile loading experiment at a high strain rate, the loading process is the same as when performing a uniaxial compression experiment at a medium strain rate; the PLC circuit in the control system is set with a capacitance of 4mF and a voltage of 1000V; Step 5. Data Processing: When performing a low strain rate uniaxial tensile loading experiment, the voltage signal is collected through the strain gauge and transmitted to the data acquisition unit (9) and recorded and stored through the Wheatstone bridge. The data acquisition device records and stores the voltage change signal V′ of the bridge arm of the Wheatstone bridge during the uniaxial tensile loading experiment; where V′ is measured by the strain gauge on the transmission rod; the voltage change signal of the bridge arm during the uniaxial tensile loading experiment recorded by the data acquisition device is converted into the strain signal on the transmission rod by formula (1-1), the specific expression of which is: Where ε′ is the strain signal of the transmission rod during the uniaxial tensile loading experiment, U′ is the supply voltage of the Wheatstone bridge during the uniaxial tensile loading experiment, k′ is the strain gauge sensitivity coefficient during the uniaxial tensile loading experiment, and V′ is the bridge arm voltage change signal of the Wheatstone bridge recorded by the data acquisition device during the uniaxial tensile loading experiment. The strain signal ε′ of the transmission rod during the uniaxial tensile loading experiment is obtained using formula (1-1). Stress σ′ in the effective test section of the specimen S : Where, σ′ S E′ represents the effective test section stress of the specimen during a uniaxial tensile loading test. T Let A′ be the elastic modulus of the transmission rod during a uniaxial tensile loading test. T Let A′ be the cross-sectional area of ​​the transmission rod during the uniaxial tensile loading test. S This refers to the effective test section cross-sectional area of ​​the specimen during a uniaxial tensile loading test. The strain ε′ of the specimen was measured using digital image correlation. S ; The strain ε of the specimen during a uniaxial tensile loading test S The horizontal axis represents the stress σ in the effective test section of the specimen during a uniaxial tensile loading test. S Plot the stress-strain curve of the specimen on the vertical axis; This completes the low strain rate uniaxial tensile loading experiment. When conducting uniaxial tensile loading experiments at medium strain rates, the data processing procedure is the same as that for uniaxial tensile loading at low strain rates. When performing uniaxial tensile loading experiments with high strain rates, the data processing procedure is the same as that for uniaxial tensile loading with low strain rates.

3. The method for measuring the wide strain rate mechanical properties of materials according to claim 1 or 2, characterized in that, The experimental setup used includes a capacitor charger (2), a codeable servo electric driver (3), an electric cylinder (4), a coaxial cable (6), two stress wave loading guns, an incident rod (10), a transmission rod (11), and a slide rail (14); the two stress wave loading guns are a first stress wave loading gun (7) and a second stress wave loading gun (16); the two stress wave loading guns are located at both ends of the slide rail (14); the transmission rod is installed inside the first stress wave loading gun, and the incident rod (10) is installed inside the second stress wave loading gun (16); the transmission rod is adjacent to the incident rod. There is a sample (15) between the end faces; the coded servo electric drive, electric cylinder, and reducer are arranged on the slide rail from the outside to the inside, and are located outside the first stress wave loading gun, and there is a coaxial device (6) between the electric cylinder and the transmission rod (11); the first positive output line of the capacitor charger (2) is connected to the positive line of the first stress wave loading gun, and at the same time, the second positive output line of the capacitor charger is connected to the second stress wave loading gun; the input end of the capacitor charger is connected to the output end of the power supply (1); a 90uH inductor is connected in series in the capacitor charger to realize medium strain rate loading.

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