Tensile test device and method capable of obtaining specified deformation state of sample

Abstract

The invention discloses a tensile test device and method capable of obtaining a specified deformation state of a sample. The tensile test device comprises a clamping mechanism, a high-speed tensile testing machine and a capacitor, the clamping mechanism is mounted on a test bed of the high-speed tensile testing machine, a main coil positive terminal of the clamping mechanism is connected with a negative electrode of the thyristor, and a main coil negative terminal of the clamping mechanism is connected with a negative electrode of the capacitor; the anode of the thyristor is connected with the anode of the capacitor. According to the invention, the high-speed tensile testing machine can be unloaded when the sample is loaded to any target deformation state before fracture, so that a crystal phase structure of the target deformation state before fracture of the sample is obtained, and an experimental basis is provided for verification of a material mechanics microscopic theory. According to the invention, the unloading time of the tensile experiment can be accurately controlled, and the precision can reach + / -2 [mu] s.

Description

Technical Field

[0001] The invention relates to a material dynamic mechanical property testing technology, in particular to a tensile testing device and a device method capable of obtaining a specified deformation state of a sample. Background Art

[0002] Engineering materials and structures are often subjected to complex stress states. For example, during takeoff and landing of large passenger aircraft, the landing gear will be impacted by the ground. The mechanical behavior of materials under medium strain rates may be different from that under quasi-static conditions. If the mechanical properties of materials under medium strain rates can be known, it will be helpful to perform numerical simulation calculations of materials under medium strain rates and design effective impact-resistant structures. Therefore, it is of great significance to study the mechanical behavior of materials under medium strain rate loading conditions.

[0003] Generally speaking, the strain rate range is 10 0 s -1 Up to 10 2 s -1 The range is medium strain rate state, and the ranges outside the left and right ends are quasi-static and high strain rate states. It should be noted that different types of test equipment need to be matched to carry out mechanical property tests in different strain rate ranges.

[0004] At present, for medium strain rate loading experiments on materials, the conventional testing method is to use a high-speed tensile testing machine, which has the characteristics of constant rate actuation (the maximum loading rate of the actuator can reach 20m / s), open-loop / closed-loop coordinated high-precision control, and high loading repeatability. It is a commonly used test equipment for obtaining the medium and low strain rate dynamic mechanical properties of materials. It is generally composed of a testing machine stand, a hydraulic power source, a control system, and a water cooler. The testing machine stand is composed of an actuator, a dynamic clamp, a static clamp, a force sensor, etc. The process of using a high-speed tensile testing machine to conduct a dynamic tensile test on a material is briefly described as follows: (1) Before the test, one end of the specimen is mounted on a static clamp and the dynamic clamp mounted on the end of the actuator is pre-tightened so that the specimen and the dynamic clamp are kept in close contact and the test piece does not interfere with or get stuck when the actuator moves up and down; (2) The test control and acquisition system parameters are set, such as the control mode, the target loading rate of the actuator, the data acquisition frequency, the data acquisition trigger mode and parameters, etc.; (3) The actuator moves to the lowest position, then accelerates upward to the target rate, and the dynamic clamp instantly holds the test piece, achieving a constant rate of stretching of the test piece, and triggering the test data acquisition system at the same time.

[0005] However, the high-speed tensile testing machines currently available on the market will continue to load the specimen until it breaks under tension after clamping it, and cannot quickly release the specimen when it is in a specific tensile deformation state. If a specimen in a specific tensile deformation state can be obtained, an electron microscope can be used to perform microscopic observation and characteristic analysis of the tested specimen, which is helpful for theoretical research on material micromechanics. Therefore, it is necessary to design a device and corresponding experimental method that can quickly release the specimen in a specific deformation state in a high-speed tensile test. Summary of the invention

[0006] In order to overcome the disadvantage of the high-speed tensile testing machine in the prior art that the loading strain cannot be controlled when loading a sample, the present invention proposes a tensile testing device and method capable of obtaining a specified deformation state of a sample.

[0007] The tensile test device capable of obtaining a specified deformation state of a specimen provided by the present invention comprises a clamping mechanism, a high-speed tensile test machine and a capacitor, wherein the clamping mechanism is installed on a test bench of the high-speed tensile test machine. The positive terminal of the main coil of the clamping mechanism is connected to the negative terminal of the thyristor; the negative terminal of the main coil of the clamping mechanism is connected to the negative terminal of the capacitor; the positive terminal of the thyristor is connected to the positive terminal of the capacitor.

[0008] The clamping mechanism includes a transfer platform, a base, a main clamping plate, a secondary clamping plate, a spring assembly, a main coil, a secondary coil, a clamping plate limit assembly and a clamping block; wherein: the base is located on the upper surface of the transfer platform; the secondary clamping plate and the main clamping plate are both located between the upper support plate and the lower support plate of the base, and the secondary clamping plate and the main clamping plate are parallel to each other, and the secondary clamping plate and the main clamping plate form a sample clamping section and a coil clamping section; the coil includes a main coil and a secondary coil; the main coil and the secondary coil are located between the main clamping plate and the secondary clamping plate, and the main coil is close to the main coil clamping plate, and the secondary coil is close to the secondary coil clamping plate; the disc spring assembly is mounted on the spring core shaft, and the main clamping plate, the main coil, the secondary coil and the secondary clamping plate are positioned by the spring assembly. The two clamping blocks are located in the sample clamping section and fixed between the secondary clamping plate and the main clamping plate; the axis of each clamping block limiting rod is perpendicular to the inner surface of the secondary clamping plate or the inner surface of the main clamping plate.

[0009] The ends of the sample clamping section of the secondary clamping plate and the sample clamping section of the main clamping plate are respectively provided with connecting shafts; the secondary clamping plate and the main clamping plate are respectively fixedly connected to the base through the connecting shafts. A clamping plate limiting assembly is provided at the end of the coil clamping section; the clamping plate limiting assembly is arranged between the secondary clamping plate and the main clamping plate and fixed on the base.

[0010] The clamp block limiting rod of one of the two clamp blocks is inserted into the second clamp block limiting hole, so that the clamp block limiting rod of the other clamp block is inserted into the first clamp block limiting hole; the clamp block limiting rod of the clamp block is tightly matched with the clamp block limiting hole.

[0011] The spring assembly comprises two disc spring groups and a spring core shaft. When assembled with the coil and the clamping plate, the two disc spring groups are respectively fixed on the outer surface of the main clamping plate and the outer surface of the secondary clamping plate.

[0012] The main clamping plate and the secondary clamping plate are respectively provided with main coil connection holes distributed in a triangular shape; and the three main coil connection holes are located around the second through hole of the spring core shaft.

[0013] The main clamping plate is in the shape of a rectangular plate, and is divided into a sample clamping section and a coil clamping section according to its function; a first clamping block limiting groove is provided on the inner surface of the sample clamping section; a first clamping block connecting hole for connecting the clamping block is provided on the bottom surface of the first clamping block limiting groove; a groove for installing the main coil is provided on the inner surface of the coil clamping section. The surface of one long side of the main clamping plate is a stepped surface, so that the surface of the sample clamping section is lower than the surface of the coil clamping section, forming an installation avoidance surface for the base. A first spring pin clamping block is provided on the end surface of the coil clamping section. The first spring pin clamping block is in the shape of a square plate, and its lower end is fixed on the end surface of the coil clamping section, and the upper end of the first spring pin clamping block protrudes out of the groove of the coil clamping section.

[0014] The secondary clamping plate is also in the shape of a rectangular plate, and is divided into a sample clamping section and a coil clamping section according to its function; there is also a rectangular second clamping block limiting groove on the inner surface of the sample clamping section; the bottom surface of the second clamping block limiting groove has two second clamping block connection holes for connecting the clamping block; the second clamping block limiting hole is located between the two second clamping block connection holes; the inner surface of the coil clamping section has a groove for installing the main coil. There is a second spring pin clamping block on the end surface of the coil clamping section, and the second spring pin clamping block is in the shape of a square plate, the lower end of which is fixed on the end surface of the coil clamping section, and the upper end of the second spring pin clamping block protrudes out of the groove of the coil clamping section.

[0015] The base is composed of a lower support plate, an upper support plate and two side vertical plates. The long sides of the upper support plate and the lower support plate on the same side are provided with a avoidance groove for the coil clamping section in the main clamping plate. The lower support plate is provided with a transfer table connection hole; the upper support plate is provided with a main clamping plate connection hole; the upper support plate and the lower support plate are provided with a coaxial secondary clamping plate connection hole. A spring pin through hole and a spring pin housing connection hole are provided on one side vertical plate.

[0016] The specific process of performing a tensile test using the electromagnetic unlocking release device proposed by the present invention is:

[0017] Step 1: Install the electromagnetic unlocking release device:

[0018] The transfer table in the electromagnetic unlocking release device is horizontally placed on the working platform of the high-speed tensile testing machine, and the high-speed camera is fixed on the working platform of the high-speed tensile testing machine through a bracket, and the high-speed camera is at the same height as the middle of the sample.

[0019] Connect the negative terminal of the capacitor to the negative terminal of the main coil in the main coil; connect the positive terminal of the capacitor to the positive terminal of the thyristor; connect the negative terminal of the thyristor to the positive terminal of the main coil in the main coil; complete the circuit connection from the capacitor to the main coil.

[0020] When installing the electromagnetic unlocking release device, adjust the position of the transfer table so that the axis of the specimen through-hole of the transfer table coincides with the axis of the dynamic clamping fixture of the high-speed tensile testing machine, the four sides of the bottom plate of the transfer table are respectively parallel to the four sides of the working platform of the high-speed tensile testing machine, and the transfer table is fixed on the working platform of the high-speed tensile testing machine.

[0021] Step 2, clamp the sample:

[0022] When clamping the sample, rotate the main clamping plate and the secondary clamping plate around the connecting axis so that the primary coil and the secondary coil are in a close contact state; keep the secondary clamping plate stationary and rotate the main clamping plate 5° counterclockwise; insert the sample into the gap between the two clamping blocks; rotate the main clamping plate clockwise to return to its original position to complete the clamping of the sample.

[0023] Step 3, obtain the time T0 required for the sample to break:

[0024] When the strain rate is set to n / s, the sample is stretched and loaded using a high-speed tensile machine until it breaks. During the loading process, the deformation state of the sample at different times is recorded by the high-speed camera, and the time T0 required from the start of loading to the fracture of the sample and the fracture strain ε of the sample are recorded. n / s is the amount of strain added to the sample per unit time.

[0025] Step 4, determine the time required for thyristor startup:

[0026] The time △T required from the start of the high-speed stretching machine to the conduction of the thyristor is set; the strain expected to be reached in this test is set to ε', and △T=T0(ε' / ε).

[0027] Step 5, capacitor charging:

[0028] The capacitor is charged to a voltage value of 3000V by a power supply.

[0029] Step 6, tensile test:

[0030] Start the high-speed tensile testing machine; the strain rate of the tensile testing machine is the same as the strain rate described in step 3, which is also n / s. Simultaneously start the trigger controller of the high-speed camera and the thyristor; and start timing immediately through the trigger controller.

[0031] When the timing reaches △T, the trigger controller sends a trigger signal to the thyristor, turning on the thyristor, so that the cable between the positive terminal of the capacitor and the positive terminal of the main coil is turned on, and the capacitor releases a semi-sinusoidal pulse current to the main coil; the peak value of the pulse current is 8000A. The peak value of the main coil is 10 6 A / m-level magnetic field. The electromagnetic repulsion pushes the main clamping plate and the secondary clamping plate away from each other, and the sample loses the clamping force; the tensile test of the sample is completed.

[0032] The microscopic features of the stretched sample under a predetermined strain state are observed through an electron microscope, and the features of the metal crystal phase at that moment are recorded.

[0033] During the stretching process of the sample, when the distance between the first spring pin clamping block and the second spring pin clamping block is greater than the thickness of the pin body in the clamping plate limiting assembly, the pin body is pushed into the gap between the first spring pin clamping block and the second spring pin clamping block under the action of the spring to prevent the main clamping plate and the secondary clamping plate from clamping the sample again under the action of the spring assembly.

[0034] The high-speed tensile testing machine off-target device provided by the present invention solves the problem in the prior art that the loading strain of the high-speed tensile testing machine cannot be controlled when loading a sample.

[0035] The clamping mechanism of the present invention comprises a base, a transfer table, a main clamping plate, a secondary clamping plate, two clamping blocks, a primary coil, a secondary coil and a spring assembly. The main clamping plate and the secondary clamping plate are located inside the base, and the two clamping blocks are fixedly connected to the main clamping plate and the secondary clamping plate respectively; one end of the sample passes through the clamping part of the clamping mechanism and contacts with the two clamping blocks to be clamped; the main clamping plate and the secondary clamping plate respectively move inwards towards each other, so that the clamping part initially clamps the sample, and then the disc spring group in the spring assembly is evenly distributed on the outside of the main clamping plate and the secondary clamping plate, and the spring core shaft of the spring assembly passes through the disc spring group and the two coaxial spring core shafts on the main clamping plate and the secondary clamping plate. The disc spring group is compressed by a nut, so that the main clamping plate and the secondary clamping plate further move inwards towards each other, so that the clamping part can clamp the sample tightly. The high-speed tensile testing machine is started to perform tensile loading on the sample. When the sample is loaded to the target strain state, the capacitor discharges the main coil, and an electromagnetic repulsion force is generated between the main coil and the secondary coil, causing the main clamping plate and the secondary clamping plate to move outward respectively, so that the clamping block loses the clamping force on the sample, and the pin of the clamping plate limit assembly quickly extends when a sufficiently large gap is generated between the main clamping plate and the secondary clamping plate, preventing the main clamping plate and the secondary clamping plate from clamping the sample again under the elastic force of the disc spring group, thereby achieving the off-target requirement for the specimen.

[0036] The top of the transfer platform is provided with a circular sample passing hole, and the sample passing hole is used to allow the sample to freely pass through the top plate of the transfer platform, so as to obtain a larger longitudinal operating space when installing the sample.

[0037] The high-speed tensile testing machine off-target device further comprises: a capacitor and a thyristor, wherein the capacitor discharges the main coil, and the thyristor is responsible for controlling the conduction state of the circuit where the capacitor is located.

[0038] Compared with the prior art, the present invention enables the high-speed tensile testing machine to unload when the sample is loaded to any target deformation state before fracture, so as to obtain the crystal phase structure of the target deformation state of the sample before fracture, providing an experimental basis for the verification of the microscopic theory of material mechanics. The present invention can accurately control the unloading time of the tensile test, and its accuracy can reach ±2μs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is an isometric view of the overall structure of the present invention.

[0040] Figure 2 It is a front view of the overall structure of the present invention.

[0041] Figure 3 yes Figure 2 Right view of .

[0042] Figure 4 yes Figure 2 Rear view of.

[0043] Figure 5 yes Figure 2 Top view of the .

[0044] Figure 6 is an isometric view of the clamping mechanism.

[0045] Figure 7 It is a front view of the clamping mechanism.

[0046] Figure 8 yes Figure 7 Right view of .

[0047] Fig. 9 yes Figure 7 Rear view of.

[0048] Fig.10 yes Figure 7 Top view of the .

[0049] Fig.11 yes Figure 7 View of the AA section.

[0050] Fig.12 yes Fig.10 View of the BB section.

[0051] Fig.13 It is an exploded schematic diagram of the transfer table, base, main clamping plate, secondary clamping plate, clamping block and connecting shaft.

[0052] Fig.14 It is an assembly diagram of the transfer table, the base, the main clamping plate, the secondary clamping plate, the clamping block and the connecting shaft.

[0053] Fig.15 It is an isometric view of a transfer station.

[0054] Fig.16 It is an isometric view of the pedestal.

[0055] Fig.17 is an isometric view of the main clamping plate.

[0056] Fig.18 This is an isometric view of the clamping plate.

[0057] Fig.19 This is the front view of the clamping plate.

[0058] Fig. 20 yes Fig.19 Right view of .

[0059] Fig.21 yes Fig.19 Top view of the .

[0060] Fig. 22 yes Fig.19 Rear view of.

[0061] Fig.23 It is a front view of the assembly structure of the base, the main clamping plate, the secondary clamping plate, the clamping block and the connecting shaft.

[0062] Fig.24 yes Fig.23 Rear view of.

[0063] Fig.25 yes Fig.23 Top view of the .

[0064] Fig.26 yes Fig.23 Right view of .

[0065] Fig. 27 yes Fig.25 View of the CC section.

[0066] Fig.28 yes Fig.25 View of the middle DD section.

[0067] Fig.29 yes Fig.25 View of the EE section.

[0068] Fig.30 yes Fig.25 View of the FF section.

[0069] Fig.31 yes Fig.25 View of the GG section.

[0070] Fig.32 yes Fig.25 View of section HH.

[0071] Fig.33 is an exploded schematic diagram of the spring assembly.

[0072] Fig.34 It is an assembly diagram of a base, a main clamping plate, a secondary clamping plate, a clamping block, a connecting shaft and a spring assembly.

[0073] Fig.35 It is an exploded schematic diagram of the main clamping plate and the main coil.

[0074] Fig.36 It is the assembly diagram of the main clamping plate and the main coil.

[0075] Fig.37 This is an exploded schematic diagram of the secondary clamping plate and the secondary coil.

[0076] Fig.38 This is a schematic diagram of the assembly of the secondary clamping plate and the secondary coil.

[0077] Fig.39 It is an exploded schematic diagram of the base, pin body, spring and clamping plate limit assembly housing.

[0078] Fig.40 It is an assembly diagram of the base, pin body, spring and clamping plate limit assembly housing.

[0079] Fig.41 is an isometric view of the clamping block.

[0080] In the figure: 1. Clamping mechanism; 2. Sample; 3. Power supply; 4. Capacitor; 5. High-speed tensile testing machine; 6. High-speed camera; 7. Transfer station; 71. Avoidance port of main coil terminal; 72. Base connection hole; 73. Transfer station mounting hole; 74. Sample through hole; 8. Base; 81. Transfer station connection hole; 82. Avoidance slot; 83. Main clamping plate connection hole; 84. Secondary clamping plate connection hole; 85. Spring pin housing connection hole; 86. Spring pin through hole; 9. Main clamping plate; 91. First base connection hole; 92. First clamping block limit slot; 93. First clamping block limit hole; 94. First clamping block connection hole; 95. Spring mandrel first through hole; 96. Main coil connection hole; 97. First spring pin clamping block; 10. Secondary clamping plate; 101. Second base connection hole; 102. Second clamping block limit slot; 103. The second clamping block limiting hole; 104. The second clamping block connecting hole; 105. The second through hole of the spring mandrel; 106. The secondary coil connecting hole; 107. The second spring pin clamping block; 11. The spring assembly; 111. The disc spring assembly; 112. The spring mandrel; 113. The spacer; 114. The nut; 12. The main coil; 121. The third through hole of the spring mandrel; 122. The threaded hole of the main coil; 123. The positive terminal of the main coil; 124. The negative terminal of the main coil; 13. The secondary coil; 131. The fourth through hole of the spring mandrel; 132. The threaded hole of the secondary coil; 14. The clamping plate limiting assembly; 141. The spring pin housing; 142. The pin body; 143. The spring; 1411. The housing connecting hole; 15. The clamping block; 151. The clamping block limiting rod; 152. The clamping block threaded hole; 16. The connecting shaft; 17. The thyristor. DETAILED DESCRIPTION

[0081] This embodiment is an electromagnetic unlocking release device for a high-speed tensile testing machine, comprising a clamping mechanism 1, a high-speed tensile testing machine 5 and a capacitor 4, wherein the clamping mechanism is installed on a test bench of the high-speed tensile testing machine. The positive terminal 123 of the main coil of the clamping mechanism is connected to the negative electrode of the thyristor 17; the negative terminal 124 of the main coil of the clamping mechanism is connected to the negative electrode of the capacitor; the positive electrode of the thyristor is connected to the positive electrode of the capacitor. The capacitor is connected to an external power supply 3.

[0082] The high-speed tensile testing machine 5 , the capacitor 4 and the thyristor 17 are all prior art.

[0083] The clamping mechanism 1 includes a transfer platform 7, a base 8, a main clamping plate 9, a secondary clamping plate 10, a spring assembly 11, a main coil 12, a secondary coil 13, a clamping plate limit assembly 14 and a clamping block 15; wherein: the base 8 is located on the upper surface of the transfer platform 7; the secondary clamping plate 10 and the main clamping plate are both located between the upper support plate and the lower support plate of the base 8, and the secondary clamping plate and the main clamping plate are parallel to each other, and the secondary clamping plate and the main clamping plate form a sample clamping section and a coil clamping section; the coil includes a main coil 12 and a secondary coil 13. The main coil 12 and the secondary coil 13 are located between the main clamping plate 9 and the secondary clamping plate 10, and the main coil is close to the main coil clamping plate, and the secondary coil 13 is close to the secondary coil clamping plate; the main clamping plate, the main coil, the secondary coil and the secondary clamping plate are positioned by the spring assembly 11.

[0084] Two clamping blocks 15 are located in the sample clamping section and fixed between the secondary clamping plate 10 and the main clamping plate 9; the clamping block limiting rod of one clamping block is inserted into the second clamping block limiting hole 103, and the clamping block limiting rod of the other clamping block is inserted into the first clamping block limiting hole 93; the clamping block limiting rod of the clamping block is tightly fitted with the clamping block limiting hole. The axis of each clamping block limiting rod is perpendicular to the inner surface of the secondary clamping plate or the inner surface of the main clamping plate. The corresponding surface between the secondary clamping plate and the main clamping plate is the clamping surface of the sample 2.

[0085] The ends of the sample clamping sections of the secondary clamping plate and the sample clamping sections of the primary clamping plate are provided with connecting shafts 16 respectively; the secondary clamping plate and the primary clamping plate are respectively connected to the base 8 through the connecting shafts. A clamping plate limiting assembly 14 is provided at the end of the coil clamping section; the clamping plate limiting assembly is arranged between the secondary clamping plate and the primary clamping plate and fixed on the base 8.

[0086] The spring assembly 11 includes two disc spring groups 111 and a spring core shaft 112, wherein the two disc spring groups are sleeved on the spring core shaft. When assembled with the coil and the clamping plate, the two disc spring groups are respectively located at the outer surface of the main clamping plate and the outer surface of the secondary clamping plate, and are fastened by a spacer 113 and a nut 114. The disc spring group adopts the existing technology.

[0087] The main clamping plate and the secondary clamping plate are respectively provided with main coil connection holes 96 distributed in a triangular shape; and the three main coil connection holes are located around the second through hole 105 of the spring core shaft.

[0088] The main clamping plate 9 is in the shape of a rectangular plate, and is divided into a sample clamping section and a coil clamping section according to its function; a rectangular first clamping block limiting groove 92 is provided on the inner surface of the sample clamping section; a first clamping block connecting hole 94 for connecting the clamping block is provided on the bottom surface of the first clamping block limiting groove; a groove for installing the main coil is provided on the inner surface of the coil clamping section. The surface of one long side of the main clamping plate is a stepped surface, so that the surface of the sample clamping section is lower than the surface of the coil clamping section, forming an installation avoidance surface for the base 8. A first spring pin clamping block 97 is provided on the end surface of the coil clamping section. The first spring pin clamping block is in the shape of a square plate, and its lower end is fixed on the end surface of the coil clamping section, and the upper end of the first spring pin clamping block protrudes out of the groove of the coil clamping section.

[0089] The secondary clamping plate 10 is also in the shape of a rectangular plate, and is divided into a sample clamping section and a coil clamping section according to its function; there is also a rectangular second clamping block limiting groove 102 on the inner surface of the sample clamping section; the bottom surface of the second clamping block limiting groove has two second clamping block connection holes 104 for connecting the clamping block; the second clamping block limiting hole 103 is located between the two second clamping block connection holes; the inner surface of the coil clamping section has a groove for installing the main coil. There is a second spring pin clamping block 107 on the end surface of the coil clamping section, which is in the shape of a square plate, and its lower end is fixed on the end surface of the coil clamping section, and the upper end of the second spring pin clamping block protrudes from the groove of the coil clamping section.

[0090] The base 8 is frame-shaped and consists of a lower support plate, an upper support plate and two side vertical plates. The long sides of the upper support plate and the lower support plate on the same side are provided with a relief groove 82 for the coil clamping section in the main clamping plate 9. The lower support plate is provided with a transfer table connection hole 81; the upper support plate is provided with a main clamping plate connection hole 83; the upper support plate and the lower support plate are provided with a coaxial secondary clamping plate connection hole 84. A spring pin through hole 86 and a spring pin housing connection hole 85 are provided on one side vertical plate.

[0091] The primary coil and the secondary coil both adopt the existing technology, which is disclosed in the invention patent CN105571961.

[0092] This embodiment also proposes a method for performing a tensile test using the electromagnetic unlocking release device. The specific process is:

[0093] Step 1: Install the electromagnetic unlocking release device:

[0094] The transfer table 7 in the electromagnetic unlocking release device is placed horizontally on the working platform of the high-speed tensile testing machine 5, and the position of the transfer table 7 is adjusted so that the axis of the sample passing hole 74 of the transfer table 7 coincides with the axis of the dynamic clamping fixture of the high-speed tensile testing machine 5, and the four sides of the bottom plate of the transfer table 7 are respectively parallel to the four sides of the working platform of the high-speed tensile testing machine 5, and the transfer table is fixed on the working platform of the high-speed tensile testing machine 5.

[0095] The high-speed camera 6 is fixed on the working platform of the high-speed stretching machine 5 through a bracket, and the high-speed camera 6 and the middle of the sample are at the same height.

[0096] Connect the negative terminal of capacitor 4 to the negative terminal 124 of the main coil in the main coil; connect the positive terminal of capacitor 4 to the positive terminal of thyristor 17; connect the negative terminal of thyristor 17 to the positive terminal 123 of the main coil in the main coil; complete the circuit connection between capacitor 4 and main coil 12.

[0097] Step 2, clamp the sample:

[0098] Rotate the main clamping plate 9 and the secondary clamping plate 10 around the connecting shaft 16 to make the primary coil 12 and the secondary coil 13 in a close contact state; keep the secondary clamping plate 10 stationary, and rotate the main clamping plate 9 counterclockwise by 5°; insert the sample 2 into the gap between the two clamping blocks 15; rotate the main clamping plate 9 clockwise to return to its original position to complete the clamping of the sample.

[0099] Step 3, obtain the time T0 required for the sample to break:

[0100] When the strain rate is set to n / s, the sample is stretched and loaded using a high-speed tensile machine until it breaks. During the loading process, the deformation state of the sample at different times is recorded by the high-speed camera, and the time T0 required from the start of loading to the fracture of the sample and the fracture strain ε of the sample are recorded. n / s is the amount of strain added to the sample per unit time.

[0101] Step 4, determine the time required for thyristor startup:

[0102] The time ΔT required from the start of the high-speed stretching machine to the conduction of the thyristor 17 is set; the strain expected to be reached in this test is set to ε', and ΔT = T0 (ε' / ε).

[0103] Step 5, capacitor charging:

[0104] The capacitor 4 is charged to a voltage value of 3000V by the power supply 3.

[0105] Step 6, tensile test:

[0106] The high-speed tensile testing machine is started; the strain rate of the tensile testing machine is the same as the strain rate described in step 3, which is also n / s. At the same time, the trigger controller of the high-speed camera 6 and the thyristor 17 is started; the timing is immediately started by the trigger controller.

[0107] When the timing reaches △T, the trigger controller sends a trigger signal to the thyristor, turning on the thyristor 17, so that the cable between the positive terminal of the capacitor and the positive terminal of the main coil is turned on, and the capacitor 4 releases a semi-sine pulse current to the main coil 12; the peak value of the pulse current is 8000A. The main coil 12 generates a magnetic field with a peak strength of 10 6 The electromagnetic repulsive force pushes the main clamping plate 9 and the secondary clamping plate 10 away from each other, and the sample 2 loses the clamping force; thus completing the tensile test of the sample.

[0108] During the stretching process of the sample, when the distance between the first spring pin clamping block 97 and the second spring pin clamping block 107 is greater than the thickness of the pin body 142 in the clamping plate limit assembly, the pin body is pushed into the gap between the first spring pin clamping block 97 and the second spring pin clamping block 107 under the action of the spring 143 to prevent the main clamping plate 9 and the secondary clamping plate 10 from clamping the sample 2 again under the action of the spring assembly 11.

[0109] The microscopic features of the stretched sample under a predetermined strain state are observed using an electron microscope, and the features of the metal crystal phase at that moment are recorded.

Claims

1. A tensile testing device capable of obtaining a specified deformation state of a specimen, characterized in that: The invention comprises a clamping mechanism (1), a high-speed tensile testing machine (5) and a capacitor (4), wherein the clamping mechanism is installed on a test bench of the high-speed tensile testing machine; the positive terminal of the main coil of the clamping mechanism is connected to the negative terminal of the thyristor (17); the negative terminal of the main coil of the clamping mechanism is connected to the negative terminal of the capacitor; the positive terminal of the thyristor is connected to the positive terminal of the capacitor; The clamping mechanism (1) comprises a transfer platform (7), a base (8), a main clamping plate (9), a secondary clamping plate (10), two spring assemblies (11), a main coil (12), a secondary coil (13), a clamping plate limit assembly (14) and a clamping block (15); wherein: the base is located on the upper surface of the transfer platform; the secondary clamping plate and the main clamping plate are both located between the upper support plate and the lower support plate of the base, and the secondary clamping plate and the main clamping plate are parallel to each other, and the secondary clamping plate and the main clamping plate form a sample clamping section and a coil clamping section; the coil comprises a main coil and a secondary coil (1 3); the main coil (12) and the secondary coil are located between the main clamping plate and the secondary clamping plate (10), and the main coil is close to the main clamping plate, and the secondary coil is close to the secondary clamping plate; the disc spring assembly is mounted on the spring core shaft, and the main clamping plate, the main coil, the secondary coil and the secondary clamping plate are positioned by the spring assembly (11); two clamping blocks (15) are located in the sample clamping section and are fixed between the secondary clamping plate (10) and the main clamping plate (9); the axis of each clamping block limit rod is perpendicular to the inner surface of the secondary clamping plate or the inner surface of the main clamping plate; A connecting shaft (16) is provided at the end of the sample clamping section of the secondary clamping plate and the end of the sample clamping section of the main clamping plate respectively; the secondary clamping plate and the main clamping plate are respectively fixedly connected to the base (8) through the connecting shafts; a clamping plate limiting assembly (14) is provided at the end of the coil clamping section; the clamping plate limiting assembly is arranged between the secondary clamping plate and the main clamping plate and fixed on the base (8).

2. The tensile testing device capable of obtaining a specified deformation state of a specimen as claimed in claim 1, characterized in that: The clamp block limiting rod of one of the two clamp blocks (15) is inserted into the second clamp block limiting hole (103), so that the clamp block limiting rod of the other clamp block is inserted into the first clamp block limiting hole (93); the clamp block limiting rod of the clamp block is tightly fitted with the clamp block limiting hole.

3. The tensile testing device capable of obtaining a specified deformation state of a specimen as claimed in claim 1, characterized in that: The spring assembly (11) comprises two disc spring groups (111) and a spring core shaft (112); when assembled with the coil and the clamping plate, the two disc spring groups are respectively fixed on the outer surface of the main clamping plate and the outer surface of the secondary clamping plate.

4. The tensile testing device capable of obtaining a specified deformation state of a specimen as claimed in claim 1, characterized in that: The main clamping plate and the secondary clamping plate are respectively provided with main coil connection holes (96) distributed in a triangular shape, and the three main coil connection holes are located around the second through hole (105) of the spring core shaft; The main clamping plate (9) is in the shape of a rectangular plate and is divided into a sample clamping section and a coil clamping section according to its function; a rectangular first clamping block limiting groove (92) is provided on the inner surface of the sample clamping section; a first clamping block connecting hole (94) for connecting the clamping block is provided on the bottom surface of the first clamping block limiting groove; a groove for mounting the main coil is provided on the inner surface of the coil clamping section; a surface of one long side of the main clamping plate is a stepped surface, so that the surface of the sample clamping section is lower than the surface of the coil clamping section, forming an installation avoidance surface of the base (8); a first spring pin clamping block (97) is provided on the end surface of the coil clamping section, the first spring pin clamping block is in the shape of a square plate, the lower end of which is fixed on the end surface of the coil clamping section, and the upper end of the first spring pin clamping block protrudes out of the groove of the coil clamping section; The secondary clamping plate (10) is also in the shape of a rectangular plate, and is divided into a sample clamping section and a coil clamping section according to its function; the inner surface of the sample clamping section is also provided with a rectangular second clamping block limiting groove (102); the bottom surface of the second clamping block limiting groove is provided with two second clamping block connecting holes (104) for connecting the clamping block; the second clamping block limiting hole (103) is located between the two second clamping block connecting holes; the inner surface of the coil clamping section is provided with a groove for installing the main coil; the end surface of the coil clamping section is provided with a second spring pin clamping block (107), the second spring pin clamping block is in the shape of a square plate, the lower end of which is fixed on the end surface of the coil clamping section, and the upper end of the second spring pin clamping block protrudes out of the groove of the coil clamping section.

5. The tensile testing device capable of obtaining a specified deformation state of a specimen as claimed in claim 1, characterized in that: The base (8) is composed of a lower support plate, an upper support plate and two side vertical plates; the long sides on the same side of the upper support plate and the lower support plate are both provided with an avoidance groove (82) for the coil clamping section in the main clamping plate (9); the lower support plate is provided with transfer platform connection holes (81); the upper support plate is provided with a main clamping plate connection hole (83); the upper support plate and the lower support plate are provided with coaxial secondary clamping plate connection holes (84); and one side vertical plate is provided with a spring pin through hole (86) and a spring pin housing connection hole (85).

6. A method for performing a tensile test using the electromagnetic unlocking release device according to claim 1, characterized in that: The specific process is: Step 1: Install the electromagnetic unlocking release device: The transfer table (7) in the electromagnetic unlocking release device is horizontally placed on the working platform of the high-speed tensile testing machine (5), and the high-speed camera is fixed on the working platform of the high-speed tensile testing machine through a bracket, and the high-speed camera (6) is at the same height as the middle of the sample; Connecting the negative terminal of the capacitor (4) to the negative terminal (124) of the main coil in the main coil; connecting the positive terminal of the capacitor to the positive terminal of the thyristor (17); connecting the negative terminal of the thyristor (17) to the positive terminal (123) of the main coil in the main coil; completing the circuit connection between the capacitor and the main coil (12); Step 2, clamp the sample: Step 3, obtain the time T0 required for the sample to break: When the set strain rate is n / s, the sample is stretched and loaded by a high-speed tensile machine until it breaks; during the loading process, the deformation state of the sample at different times is recorded by the high-speed camera, and the time T0 required from the start of loading to the fracture of the sample and the fracture strain ε of the sample are recorded; n / s is the strain amount increased by the sample per unit time; Step 4, determine the time required for thyristor startup: The time ΔT required between the start of the high-speed stretching machine and the conduction of the thyristor (17) is set; the strain amount expected to be reached in this test is ε', and ΔT = T0 (ε' / ε); Step 5, capacitor charging: The capacitor is charged to a voltage of 3000 V by a power supply 3; Step 6, tensile test: Start a high-speed tensile testing machine; the strain rate of the tensile testing machine is the same as the strain rate described in step 3, which is also n / s; simultaneously start the trigger controller of the high-speed camera (6) and the thyristor (17); and start timing immediately through the trigger controller; When the timed duration reaches ΔT, the trigger controller sends a trigger signal to the thyristor, causing the thyristor (17) to be turned on, so that the cable between the positive electrode of the capacitor and the positive terminal of the main coil is turned on, and the capacitor (4) releases a semi-sinusoidal pulse current to the main coil (12); the peak value of the pulse current is 8000A; the main coil (12) generates a peak value of 10 6 A / m-level magnetic field is used; the main clamping plate (9) and the secondary clamping plate (10) are pushed away from each other by the electromagnetic repulsion force, and the sample 2 loses the clamping force; and the tensile test of the sample is completed; The microscopic features of the stretched sample under a predetermined strain state are observed through an electron microscope, and the features of the metal crystal phase at that moment are recorded.

7. The method for performing a tensile test using an electromagnetic unlocking release device as claimed in claim 6, characterized in that: When installing the electromagnetic unlocking release device, the position of the transfer platform (7) is adjusted so that the axis of the sample passing hole (74) of the transfer platform coincides with the axis of the dynamic clamping fixture of the high-speed tensile testing machine (5), the four sides of the bottom plate of the transfer platform are respectively parallel to the four sides of the working platform of the high-speed tensile testing machine, and the transfer platform is fixed on the working platform of the high-speed tensile testing machine.

8. The method for performing a tensile test using an electromagnetic unlocking release device as claimed in claim 6, characterized in that: When clamping the sample, the main clamping plate (9) and the secondary clamping plate (10) are rotated around the connecting shaft (16) so that the main coil (12) and the secondary coil (13) are in a close contact state; the secondary clamping plate (10) is kept stationary and the main clamping plate (9) is rotated 5° counterclockwise; the sample 2 is inserted into the gap between the two clamping blocks (15); the main clamping plate is rotated clockwise to return to its original position to complete the clamping of the sample.

9. The method for performing a tensile test using an electromagnetic unlocking release device as claimed in claim 6, characterized in that: During the stretching process of the sample, when the distance between the first spring pin clamping block (97) and the second spring pin clamping block 107 is greater than the thickness of the pin body (142) in the clamping plate limit assembly, the pin body is pushed into the gap between the first spring pin clamping block (97) and the second spring pin clamping block (107) under the action of the spring (143), so as to prevent the main clamping plate (9) and the secondary clamping plate (10) from clamping the sample (2) again under the action of the spring assembly (11).

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