Momentum exchange driven impact indentation testing device and testing method

Abstract

The present invention relates to a momentum exchange driven impact indentation testing device and testing method. The device comprises a driving unit, a measuring unit, a positioning and point changing unit, and an in-situ observation unit. The modular unit adopts a momentum exchange method to drive the indenter to press into the test piece. The measuring unit picks up the force and displacement information during the impact indentation test. The in-situ observation unit records the deformation and heat distribution of the test piece in real time. The motion characteristics and program automatic control of the driving unit avoid secondary impact. The testing device of the present invention provides the necessary experimental means and testing device for testing and analyzing the mechanical properties of materials under high strain rates, and has good application prospects in the fields of aerospace, armor protection, and physical property characterization.

Description

Technical Field

[0001] The present invention relates to the field of precision instruments, and in particular to a momentum exchange driven impact indentation testing device and a testing method. Background Art

[0002] Materials underpin and guide all high-tech advancements. In key areas such as military armor protection, ultra-high-speed machining, and aerospace safety, materials face high-strain-rate impact conditions. Traditional static testing methods can render material mechanical properties ineffective. Therefore, developing a reliable high-strain-rate impact loading tester is crucial.

[0003] At present, high-strain-rate material micromechanical property testing devices are generally in the development stage. Specifically, there are multiple ways to implement high-strain-rate impact loading, but many problems exist. For example, the impact indentation device based on the Hopkinson bar developed by Ghatu Subhash et al. at the University of Michigan in the United States successively attached strain gauges to the Hopkinson incident bar and cantilever beam, and performed tests by directly applying stress wave signals to reversely calculate the indentation force and displacement; and by measuring the deflection deformation of the cantilever beam and piezoelectric force sensors to directly measure the indentation force and displacement. Because the drive of the Hopkinson bar must meet the assumption of a one-dimensional stress wave, the stress wave will produce waveform dispersion at the indenter, resulting in unstable impact loading, extremely noisy measurement signals, and difficulty in obtaining indentation curves. Another example is the electromagnetically driven pendulum-type impact indentation test device developed by Micro Materials Ltd. in the United Kingdom. However, it has the problem of repeated loading, and its impact acceleration space is limited by the measurement range of the displacement sensor, resulting in low indentation velocity and energy. Another example is the Nanomechanics test device in the United States. Inc.'s impact press-in device, which uses a voice coil motor drive with a step current signal, also suffers from repeated press-in and lacks a curve. Another example is the Swiss company Alemnis AG's piezoelectric-driven impact press-in device, which also suffers from low speed and energy. These issues are either due to limitations in the testing principles, making it difficult to obtain test curves and conducting in-depth analysis, or due to issues with repeated press-in, low energy, and slow speed in the testing instrument, which are not consistent with the material's actual loading conditions.

[0004] Therefore, there is an urgent need for an impact indentation testing device that is stable and reliable, has adjustable pressing speed and energy, and can prevent secondary loading, for use in ultra-high-speed processing, aerospace, military protection and other fields. Summary of the Invention

[0005] The purpose of the present invention is to provide a momentum exchange driven impact indentation testing device, which performs impact loading with controllable pressing speed and energy on the test piece, obtains the pressing force and displacement curve of the pressing process, and prevents the indenter from loading the test piece secondary.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A momentum exchange driven impact indentation testing device comprises an in-situ observation unit 2, a positioning and point changing unit 3, a driving unit 4, a measuring unit 5, a data acquisition card 6, a motion control card 7 and a control system 8; the in-situ observation unit 2 is used to observe the pressing position on the test piece 515 and transmit the deformation and thermal distribution data of the test piece 515 to the control system 8; the driving unit 4 comprises a first component and a second component of the same weight, the first component swings and then hits the second component to perform translational motion; the first component comprises a pendulum 411, a hammer head 47 fixedly connected to the lower end of the pendulum, and a hammer head 47 fixedly connected to the front end of the hammer head 47. The ball head 49 and the light shielding plate 46 are installed at the lower end of the hammer head 47, and the center of gravity of the first component is located on the central axis of the ball head 49; the second component includes a flexible hinge 43, a pressure head 42 fixedly connected to the front end of the moving part of the flexible hinge 43, and an impact block 410 fixedly connected to the rear end of the moving part of the flexible hinge 43, and the center of gravity of the second component is located on the central axis of the moving part of the flexible hinge 43; when the ball head 49 swings to the lowest point, the axis and the axis of the impact block 410 are on the same horizontal line; the first component drives the pendulum 411 to swing through the swing control component, and the swing control component includes a pendulum shaft 418, a motor 41 7 and a frame 412 for mounting a pendulum shaft 418, the motor shaft is connected to the pendulum shaft 418 via an electromagnetic clutch 420, and an encoder 413 is mounted on the pendulum shaft 418; the test piece 515 and the flexible hinge 43 are both mounted on the positioning and point-changing unit 3, and are driven by the positioning and point-changing unit 3 to perform X-axis positioning and YZ direction point-changing; the measuring unit 5 includes a laser interferometer, a piezoelectric force sensor 56, a right-angle prism 58, a reflector 510, and a photoelectric switch 511, the test piece 515 and the right-angle prism 58 are mounted on the measuring end of the piezoelectric force sensor 56, and the probe 55 of the laser interferometer emits The light beam enters the right-angle prism 58 and the plane mirror 510 in turn. The incident surface of the right-angle prism 58 and the plane mirror 510 are at a 45-degree angle, and the plane mirror 510 is perpendicular to the axis of the pressure head 42; the axes of the pressure head 42, the test piece 515 and the piezoelectric force sensor 56 are parallel. When the ball head 49 is at the lowest point, the two ends of the light shielding plate 46 are located in the slit of the photoelectric switch 511; the control system 8 receives and controls the electromagnetic clutch 420, the motor 417 and the encoder 413 through the motion control card 7, and collects data from the photoelectric switch 511 and the piezoelectric force sensor 56 through the data acquisition card 6.

[0008] As a better technical solution of the present invention, the in-situ observation unit 2 includes a high-speed camera 28 and a thermal imager 24. The high-speed camera 28 and the thermal imager 24 adjust their spatial positions through the three-dimensional motion platform I 22 and the three-dimensional motion platform II 26 respectively so that their observation axes are in the same horizontal plane as the motion axis of the indenter 42.

[0009] As a more optimal technical solution of the present invention, a mounting plate VI 415 is fixedly connected to the top of the frame 412 , a motor 415 is fixedly connected to the mounting plate VI 415 , and the pendulum shaft 418 is mounted on the mounting plate VI 415 via a support seat.

[0010] As a more optimal technical solution of the present invention, the shaft of the motor 415 is connected to the transmission shaft 422 via a reducer 423 , and the transmission shaft 422 is connected to the pendulum shaft 418 via an electromagnetic clutch 420 .

[0011] As a better technical solution of the present invention, the positioning and changing point unit 3 includes a base 31, a mounting plate IV32, a mounting plate V33, an X-axis macro positioning platform 36, an adapter plate III35, and an X-axis micro positioning platform 38. The mounting plate IV32 is mounted on the base 31, and the mounting plate V33 is mounted on the mounting plate IV32. Through the long keyhole on the mounting plate V33, the mounting plate V33 can be adjusted forward and backward along the X-axis direction. The X-axis macro positioning platform 36 is mounted on the mounting plate V33. There is a reinforcement plate 34 on each side of the X-axis macro positioning platform 36 mounted on the mounting plate V33. The thickness of the reinforcement plate 34 is lower than the installation plane height of the X-axis macro positioning platform 36. The adapter plate III35 is mounted on the X-axis macro positioning platform 36. The X-axis macro positioning platform 36 is installed on the installation plane, the X-axis micro positioning platform 38 is installed on the adapter plate III 35, the adapter plate IV 32, the reinforcement rib 311, and the adapter plate V 312 are fixedly connected, the adapter plate IV 39 is installed on the X-axis micro positioning platform 38, the YZ point changing platform 314 is installed on the adapter plate V 312, and the adapter plate VI 315 is installed on the YZ point changing platform 314. The X-axis macro positioning platform 36 drives the YZ point changing platform 314 and the X-axis micro positioning platform 38 to perform macro movement and positioning along the X-axis, the X-axis micro positioning platform 38 drives the YZ point changing platform 314 to perform micro movement and positioning along the X-axis, and the YZ point changing platform 314 drives the piezoelectric force sensor 56 and the specimen table 59 to change points along the YZ direction.

[0012] As a better technical solution of the present invention, the probe 55 is installed on the three-dimensional motion platform III52 through the probe holder 54. The probe 55 is connected to the laser interferometer controller 51 through an optical fiber. The probe 55 adjusts its spatial position through the three-dimensional motion platform III52 so that its measuring axis is in the same horizontal plane as the center of the right-angle prism 58 and the center of the reflector 510, and the incident light and the reflected light of the reflector 510 coincide and are parallel to the axis of the indenter 42, thereby realizing the measurement of the indentation displacement.

[0013] As a more preferred technical solution of the present invention, the measuring end of the piezoelectric force sensor 56 is fixedly connected to an adapter plate VII57 , and the right-angle prism 58 and the test piece 515 are installed on the same side of the adapter plate VII57 .

[0014] As a more preferred technical solution of the present invention, the photoelectric switch 511 is installed on the photoelectric switch base 513 through the mounting frame 512 and the adapter frame 514 , and the photoelectric switch base 513 is installed on the mounting plate V33 .

[0015] As a more optimal technical solution of the present invention, the testing device further includes a vibration isolation platform 1 , on which the in-situ observation unit 2 , the positioning and point changing unit 3 , the driving unit 4 and the measuring unit 5 are all installed.

[0016] Another object of the present invention is to provide a momentum exchange driven impact indentation testing method, comprising:

[0017] Step 1: The test piece 515 is brought into pre-contact with the indenter 42 via the X-axis macro positioning platform 36, the X-axis micro positioning platform 38, and the YZ point changing platform 314, and then locked through the three platforms;

[0018] Step 2: Keep the electromagnetic clutch 420 normally closed, and the encoder 413 provides real-time feedback of the position and motion state of the pendulum shaft 418 to the motion control card 7 and the control system 8;

[0019] Step 3: After setting the pendulum lifting height, the measurement begins. The control system 8 monitors the operating status of the test device and gives instructions based on the feedback value of the encoder 413. The control command is sent from the control system 8 to the motion control card 7. The motion control card 7 outputs an electrical signal to drive the motor 417 to drive the pendulum to the set height.

[0020] Step 4: The control system 8 detects that the feedback value of the encoder 413 matches the set height, sends a command to control the motion control card 7 to output a signal to disconnect the electromagnetic clutch 420, and the hammer head 47 hits the moving part of the flexible hinge 43, causing it to drive the indenter 42 to complete an impact loading. The force and displacement information during the impact indentation test is picked up by the measurement unit 5;

[0021] Step 5: The moving portion of the flexible hinge 43 moves backward under the deformation of the deformable portion of the flexible hinge 43 and strikes the hammer 47, causing momentum exchange. The moving portion of the flexible hinge 43 stays at the impact point, and the entire body centered on the hammer 47 begins to move backward, driving the pendulum shaft 418 to rotate in the opposite direction.

[0022] Step 6: The encoder 413 detects the reverse displacement value and sends it to the motion control card 7 and the control system 8 in real time. The control system 8 sends a control instruction to the electromagnetic clutch 420 to close it. The pendulum shaft 418 is captured by the electromagnetic clutch 420, the motor 417 is in a self-locking state, and the pendulum shaft 418 stops moving. The dynamic hardness of the test piece 515 can be calculated based on the force and displacement information of the impact indentation process. The formula is:

[0023]

[0024] Among them H Dyn is the dynamic hardness, m eff is the sum of the equivalent mass of the moving part of the flexible hinge 43 and the pressure head 42, V incident V is the velocity of the indenter 42 when it first contacts the test piece 515. re bound is the speed of the indenter 42 at the same position after the indenter 42 completes the indentation, h rest is the residual depth of the impact indentation, f DAF (h) is the area function of the pressure head;

[0025] Step 7: During the impact indentation process, the strain rate at different times and in different deformation areas will change. The strain rate when the indentation depth is h is The average strain rate of the entire process is used as the characteristic strain rate of the experiment. Through multiple experiments with different impact energies, a mapping relationship between the characteristic strain rate and dynamic hardness of the test piece 515 is established to obtain the dynamic mechanical properties of the test piece 515.

[0026] The beneficial effects are:

[0027] The momentum exchange driven impact indentation testing device provided by the present invention can avoid secondary impacts, realizes the driving of the indenter by means of momentum exchange, separates the indenter and the pendulum, ensures the relatively fixed spatial position of the indenter, provides convenience for displacement measurement, and enables the pendulum to obtain a larger energy storage range. In addition, through mechanical structure design and program automatic control, it is possible to prevent the indenter from rebounding and causing secondary loading on the test piece. The testing device of the present invention includes a driving unit, a measuring unit, a positioning and point change unit, and an in-situ observation unit through a modular design. The structural design is reasonable, the overall size is compact, and the units do not interfere with each other, effectively increasing the expansion space of the instrument function, and also facilitating the repair and maintenance of each unit component during subsequent use. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide further understanding of the present invention and constitute a part of this application. The illustrative examples of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0029] Figure 1 This is a test principle diagram of the present invention;

[0030] Figure 2 It is an overall axial side schematic diagram of the present invention;

[0031] Figure 3 It is an overall top view of the present invention;

[0032] Figure 4 Schematic diagram of the in-situ observation unit of the present invention;

[0033] Figure 5 This is a schematic diagram of the axial side of the positioning and changing point unit of the present invention;

[0034] Figure 6 is an axial schematic diagram of a measuring unit of the present invention;

[0035] Figure 7 A top view of the measuring unit of the present invention;

[0036] Figure 8 It is a front view of the drive unit of the present invention and an exploded view of the assembly of the lower half;

[0037] Figure 9 A side view of the drive unit of the present invention and an exploded view of the upper portion thereof;

[0038] Figure 10 1. A top view and an axonometric view of the flexible hinge of the present invention;

[0039] Figure 11 Schematic diagram of eliminating frame deformation for displacement measurement in the measurement unit;

[0040] In the figure: 1. Isolation platform; 2. In-situ observation unit; 3. Positioning and point change unit; 4. Drive unit; 5. Measurement unit; 6. High-speed data acquisition card; 7. Motion control card; 8. Control system; 21. Mounting plate I; 22. Three-dimensional motion platform I; 23. Adapter plate I; 24. Thermal imager; 25. Mounting plate II; 26. Three-dimensional motion platform II; 27. Adapter plate II; 28. High-speed camera; 31. Base; 32. Mounting plate IV; 33. Mounting plate V; 34. Reinforcement plate; 35. Adapter plate III; 36. X-axis macro positioning platform; 37. Screw group I; 38. X-axis micro positioning platform; 39. Adapter plate IV; 310. Screw group II; 311. Reinforcement rib; 312. Adapter plate V; 313. Bolt group; 314. YZ point change platform; 315. Adapter plate VI; 41. Hinge seat; 42. Press head; 43. Flexible hinge; 44. Counterweight block I; 45, displacement measuring block; 46, light shield; 47, hammer head; 48, counterweight block II; 49, carbide ball head; 410, carbide impact block; 411, pendulum; 412, frame; 413, encoder; 414, support base I; 415, mounting plate VI; 416, motor base; 417, motor; 418, pendulum shaft; 419, support base II; 420, electromagnetic clutch; 421, support base III ; 422. Drive shaft; 423. Reducer; 51. Laser interferometer controller; 52. Three-dimensional motion platform III; 53. Mounting plate III; 54. Probe holder; 55. Probe; 56. Piezoelectric force sensor; 57. Adapter plate Ⅶ; 58. Right-angle prism; 59. Test piece table; 510. Reflector; 511. Photoelectric switch; 512. Mounting bracket; 513. Photoelectric switch holder; 514. Adapter bracket; 515. Test piece. DETAILED DESCRIPTION

[0041] The details of the present invention and its specific implementation methods are further described below with reference to the accompanying drawings.

[0042] See also Figures 1 to 11As shown, a momentum exchange driven impact indentation testing device of the present invention comprises an in-situ observation unit 2, a positioning and point changing unit 3, a driving unit 4, a measuring unit 5, a data acquisition card 6, a motion control card 7 and a control system 8; the in-situ observation unit 2 is used to observe the pressing position on the test piece 515 and transmit the deformation and heat distribution data of the test piece to the control system 8; the driving unit 4 comprises a first component and a second component of the same weight, the first component swings and then hits the second component to perform translational motion; the first component comprises a pendulum 411, a hammer head 47 fixedly connected to the lower end of the pendulum, and a hammer head 47 fixed at the front end thereof. The center of gravity of the first component is located on the central axis of the ball head 49; the second component includes a flexible hinge 43, a pressure head 42 fixedly connected to the front end of the moving part of the flexible hinge 43, and an impact block 410 fixedly connected to the rear end of the moving part of the flexible hinge 43. The center of gravity of the second component is located on the central axis of the moving part of the flexible hinge 43; when the ball head 49 swings to the lowest point, the axis and the axis of the impact block 410 are on the same horizontal line; the first component drives the pendulum 411 to swing through the swing control component, and the swing control component includes a pendulum shaft 418, a motor 417 and a frame 412 for mounting a pendulum shaft 418, the motor shaft of the motor 417 is connected to the pendulum shaft 418 via an electromagnetic clutch 420, and an encoder 413 is mounted on the pendulum shaft 418; the test piece 515 and the flexible hinge 43 are both mounted on the positioning and point-changing unit 3, and are driven by the positioning and point-changing unit 3 to perform X-axis positioning and YZ direction point-changing; the measuring unit 5 includes a laser interferometer, a piezoelectric force sensor 56, a right-angle prism 58, a reflector 510 and a photoelectric switch 511, the test piece 515 and the right-angle prism 58 are mounted on the measuring end of the piezoelectric force sensor 56, and the probe 55 of the laser interferometer emits The light beam enters the right-angle prism 58 and the plane mirror 510 in sequence. The incident surface of the right-angle prism 58 and the plane mirror 510 are at a 45-degree angle, and the plane mirror 510 is perpendicular to the axis of the pressure head 42. The axes of the pressure head 42, the tested object 515 and the piezoelectric force sensor 56 are parallel. When the ball head 49 is at the lowest point, the two ends of the light shielding plate 46 are located in the slit of the photoelectric switch 511. The control system 8 receives and controls the electromagnetic clutch 420, the motor 417 and the encoder 413 through the motion control card 7, and collects data from the photoelectric switch 511 and the piezoelectric force sensor 56 through the data acquisition card 6.

[0043] The momentum-exchange-driven impact indentation testing device of the present invention drives the indenter through momentum exchange, separating the indenter and pendulum. This not only ensures the indenter's relatively fixed spatial position, facilitating displacement measurement, but also allows the pendulum to obtain a larger energy storage range. Furthermore, program control prevents secondary loading of the test piece after the indenter rebounds. Through a modular design, the present invention conducts micro-area dynamic performance testing and in-situ dynamic deformation monitoring of materials in parallel, providing technical support for testing the service performance of materials under impact conditions.

[0044] See also Figure 1 As shown, the momentum exchange driven impact indentation testing device of the present invention performs an impact indentation experiment. The testing principle is to enable the indenter 42 to obtain an initial velocity to impact the test piece 515 through the momentum exchange of the pendulum and the moving parts of the flexible hinge 43 in the driving unit 4. During the impact indentation process, the experimental data such as material deformation, heat distribution, load and displacement are picked up by the in-situ observation unit 2, the piezoelectric force sensor 56 and the probe 55.

[0045] See also Figure 2 and Figure 3 As shown, the momentum exchange driven impact indentation testing device of the present invention includes a shock isolation platform 1, an in-situ observation unit 2, a positioning and changing point unit 3, a driving unit 4, and a measuring unit 5. The driving unit 4 is installed on the base 31 in the positioning and changing point unit 3 through a frame 412, and the in-situ observation unit 2, the positioning and changing point unit 3, and the measuring unit 5 are respectively installed on the shock isolation platform 1. The axes of the pressure head 42 of the driving unit 4, the test piece 515 of the measuring unit 5 and the piezoelectric force sensor 56 are parallel; the hinge seat 41 of the driving unit 4 is installed on the mounting plate V33 of the positioning and changing point unit 3; the high-speed camera 28 and the thermal imager 24 of the in-situ observation unit 2 can adjust their spatial positions through the three-dimensional motion platform I22 and the three-dimensional motion platform II26 respectively so that their observation axes pass through the position where the pressure head 42 on the test piece 515 is pressed and are in the same horizontal plane as the motion axis of the pressure head 42, so as to realize in-situ observation of the deformation process of the test piece; when the hammer head 47 of the driving unit 4 moves to the lowest position, the two ends of the light shielding plate 46 are located at the measuring unit 5 In the slit of the photoelectric switch 511, the photoelectric switch 511 triggers the high-speed data acquisition card 6, the thermal imager 24, and the high-speed camera 28 to collect data and record the data to the computer. After receiving the trigger signal, the motion control card 7 runs the next action according to the program; the motor 417, the electromagnetic clutch 420, the encoder 413 of the drive unit 4 are connected to the motion control card 7 by a cable, and the motion control card 7 is connected to the control system 8 by a cable. The control system 8 receives and controls the motor 417, the electromagnetic clutch 420, and the encoder 413 through the motion control card 7, thereby realizing impact loading of the test piece 515 and picking up the force and displacement information during the impact indentation process.

[0046] There are multiple threaded holes on the counterweight block I 44 and the counterweight block II 48, which are used to add counterweight blocks to adjust the center of gravity of the first component and the second component. The rocker arm 411 is a high-rigidity, lightweight hollow rod, which makes it easy for the first component to adjust the center of gravity of the second component by adjusting the weight of the counterweight block II 48, and no significant bending stress wave is excited in the rocker arm 411 when the first component and the second component collide.

[0047] See also Figure 5 As shown, the specific structure of the positioning and changing point unit 3 is as follows:

[0048] The base 31 is mounted on the isolation table 1, the mounting plate IV 32 is mounted on the base 31, the mounting plate V 33 is mounted on the mounting plate IV 32, and the mounting plate V 33 can be adjusted forward and backward along the X-axis direction through the long keyhole on the mounting plate V 33. The X-axis macro positioning platform 36 is mounted on the mounting plate V 33. There is a reinforcement plate on each side of the X-axis macro positioning platform 36 mounted on the mounting plate V 33. The thickness of the reinforcement plate 34 is slightly lower than that of the X-axis macro The positioning platform 36 is mounted at a height of a plane. Adapter plate III 35 is mounted on the mounting plane of the X-axis macro positioning platform 36. The X-axis micro positioning platform 38 is mounted on adapter plate III 35. Adapter plate IV 32, reinforcement ribs 311, and adapter plate V 312 are fixedly connected. Adapter plate IV 39 is mounted on the X-axis micro positioning platform 38. The YZ point-changing platform 314 is mounted on adapter plate V 312. Adapter plate VI 315 is mounted on the YZ point-changing platform 314. The X-axis macro positioning platform 36 drives the YZ point-changing platform 314 and the X-axis micro positioning platform 38 to perform macroscopic movement and positioning along the X-axis. The X-axis micro positioning platform 38 drives the YZ point-changing platform 314 to perform microscopic movement and positioning along the X-axis. The YZ point-changing platform 314 drives the piezoelectric force sensor 56 and the specimen stage 59 to change points along the YZ directions. During the impact loading process, the adapter plate III 35 and the reinforcement plate 34 are reinforced by the screw group I 37, the adapter plate IV 39 and the adapter plate III 35 are reinforced by the screw group II 310, and the adapter plate VI 315 and the adapter plate V 312 are reinforced by the bolt group 313, which can improve the rigidity of the positioning and point changing unit 3; during pre-positioning and point changing, the screw group I 37, the screw group II 310, and the bolt group 313 are loosened. There are long keyholes along the Y direction on both sides of the adapter plate VI315, and there is a long keyhole along the Z direction on the adapter plate V312, ensuring that the adapter plate VI315 and the adapter plate V312 can move relative to each other in the Y and Z directions. There are long keyholes along the X direction on both sides of the adapter plate IV39 and the adapter plate III35, so that there can be relative movement between the adapter plate III35 and the reinforcement plate 34, and between the adapter plate III35 and the adapter plate IV39.

[0049] See also Figures 6 to 7 As shown, the specific structure of the measuring unit 5 is as follows:

[0050] The test piece 515 is coaxially mounted on the adapter plate Ⅶ57 through the test piece table 59, and the adapter plate Ⅶ57 is coaxially mounted on the measuring end of the piezoelectric force sensor 56. The piezoelectric force sensor 56 is fixed on the adapter plate Ⅵ315 of the positioning and point changing unit 3 to measure the impact force on the test piece 515; the right-angle prism 58 is mounted on the adapter plate Ⅶ57 on the same side as the test piece 515, and the laser interferometer probe 55 is mounted on the three-dimensional motion platform III52 through the probe holder 54. There is an optical fiber connection between the laser interferometer probe 55 and the laser interferometer controller 51. The laser interferometer probe 55 adjusts its spatial position through the three-dimensional motion platform III52 so that its measuring axis is in the same horizontal plane as the center of the right-angle prism 58 and the center of the reflector 510, and the entrance of the reflector 510 is The incident light and the reflected light coincide and are parallel to the axis of the indenter 42, realizing the measurement of the indentation displacement; the right-angle prism 58 and the test piece 515 are simultaneously mounted on the adapter plate Ⅶ57. When the test piece 515 is subjected to impact loading, the piezoelectric force sensor 56 and the positioning and point changing unit 3 behind the test piece 515 are also deformed by the impact loading. The right-angle prism 58 and the test piece 515 will therefore produce displacements and the displacement amounts are equal. The displacement change measured by the laser interferometer probe 55 is the X-direction displacement of the indenter 42 minus the X-direction displacement of the right-angle prism 58, that is, the displacement of the indenter 42 pressed into the test piece 515; the photoelectric switch 511 is mounted on the photoelectric switch seat 513 through the mounting frame 512 and the adapter frame 514, and the photoelectric switch seat 513 is mounted on the mounting plate Ⅴ33.

[0051] See also Figures 8 to 10 As shown, the specific structure of the driving unit 4 is as follows:

[0052] The flexible hinge 43 is mounted on the hinge seat 41, with a pressure head 42 mounted on the front end and a carbide impact block 410 mounted on the rear end. The upper and lower end surfaces are symmetrically mounted with a counterweight block I 44, and a displacement measuring block 45 is symmetrically mounted on the counterweight block I 44. The hammer head 47 is fixed to the rocker 411 by fasteners. A carbide ball head 49 is mounted on the front end, and counterweight blocks II 48 are symmetrically mounted on the left and right ends. A light shielding plate 46 is mounted on the lower end. The carbide ball head 49, the counterweight block II 48, and the light shielding plate 4 6. The pendulum 411 is fixedly connected to form a first assembly with the hammer head 47 as the core. The pressure head 42, the carbide impact block 410, the counterweight block I 44, and the displacement measuring block 45 are fixedly connected to form a second assembly with the moving part of the flexible hinge 43 as the core. By adjusting the installation position of the pendulum 411 on the pendulum shaft 418, the axis of the carbide impact block 410 and the carbide ball head 49 coincide with each other. The first assembly is adjusted to adjust the overall center of gravity to the center axis of the hammer head 47 by adjusting the weight of the counterweight block II 48. On, and when the first component is stationary at the lowest position, there is no pressure in contact between the carbide ball head 49 and the carbide impact block 410. The second component adjusts the overall center of gravity to the central axis of the moving part of the flexible hinge 43 by adjusting the weight of the counterweight block I44, and after the mass adjustment of the counterweight block I44 and the counterweight block II48, the masses of the first component and the second component are equal. When the first component moves to the lowest position, the two wholes realize momentum exchange through the collision between the carbide ball head 49 and the carbide impact block 410. After the momentum exchange, the first component will stay at the impact point, and the second component will obtain the overall speed with the hammer head 47 as the center to move forward, thereby driving the pressure head 42 to move. When the pressure head 42 is pressed to the maximum displacement, the elastic force of the deformed part of the flexible hinge 43 causes the second component to move in the opposite direction until the momentum is exchanged again by impacting the hammer head 47. After that, the second component will stay at the impact point, and the first component will obtain the speed of the second component to move backward.The axes of the pendulum shaft 418 and the transmission shaft 422 coincide with each other but do not touch each other. The two are respectively fixedly connected to the input and output ends of the electromagnetic clutch 420, and the transmission and disconnection between the transmission shaft 422 and the pendulum shaft 418 are realized by the opening and closing of the electromagnetic clutch 420; the pendulum shaft 418 is installed on the mounting plate VI 415 through the support seat I 414 and the support seat II 419, the shaft end of the pendulum shaft 418 is fixedly connected to the mover of the encoder 413, the transmission shaft 422 is installed on the frame 412 through the support seat III 421, the shaft end of the transmission shaft 422 is fixedly connected to the output end of the reducer 423, the reducer 423 is fixed on the frame 412, the input end is fixedly connected to the shaft of the motor 417, and the motor 417 is installed on the mounting plate through the motor seat 416 On VI415, the encoder 413 detects the rotation angle of the pendulum shaft 418 in real time and sends the position information to the motion control card 7 in real time. The electromagnetic clutch 420 is in a normally closed state. Under the program control of the control system 8, the motor 417 drives the hammer head to rise to a set height. By controlling the electromagnetic clutch 420 to open, the hammer head 47 performs a circular motion along the axis of the pendulum shaft 418. Changing the set height can change the speed and energy of the whole body centered on the hammer head 47 at the lowest point, thereby changing the movement speed and energy of the whole body centered on the moving part of the flexible hinge 43, and then changing the speed and energy of the pressure head 42 impacting the test piece 515, thereby achieving pressing into the test piece 515 with different pressing rates and impact energies.

[0053] like Figure 11 As shown, when the indenter 42 is pressed into the test piece 515, the displacement of the indenter 42 is Δl T The deformation of the frame is equal to the displacement of the right-angle prism 58, which is Δl S , the displacement of the indenter 42 actually pressed into the specimen 515 is (Δl T -Δl S ), the target displacement change measured by the laser interferometer probe 55 is [(l0+l1)-(l0+l1′+l2′)]. Since the acute angle of the right-angle prism 58 is 45°, there is Δl S =l1′, and l1-l2′=Δl T , so [(l0+l1)-(l0+l1′+l2′)]=(Δl T -Δl S ), that is, the target displacement change measured by the laser interferometer probe 55 is the displacement of the indenter 42 actually pressed into the test piece 515.

[0054] The photoelectric switch 511 is positioned in the X direction via the long keyhole on the adapter frame 514 to adjust the time difference between the collision between the first component and the second component and the entry of the light shielding plate 46 into the slit of the photoelectric switch 511, thereby adjusting the time difference between the trigger signal and the measurement signal.

[0055] The momentum exchange driven impact indentation testing method of the present invention comprises the following steps:

[0056] Step 1: Use the X-axis macro positioning platform 36, X-axis micro positioning platform 38, and YZ point changing platform 314 in the positioning and point changing unit 3 to bring the test piece 515 into pre-contact with the indenter 42, and lock each platform with the screw group I 37, screw group II 310, and bolt group 313;

[0057] Step 2: Start the test instrument, keep the electromagnetic clutch 420 normally closed, and the encoder 413 provides real-time feedback of the position and motion status of the pendulum shaft 418 to the motion control card 7 and the control system 8. The program waits for the operator to set the pendulum lifting height.

[0058] Step 3: After setting the preset height, click Start Test, and the program will automatically run. The program in the control system 8 monitors the operating status of the instrument according to the feedback value of the encoder 413 and gives instructions. The control command is sent from the control system 8 to the motion control card 7. The motion control card 7 outputs an electrical signal to drive the motor 417 to drive the pendulum to the set height.

[0059] Step 4: When the program detects that the feedback value of the encoder 413 matches the set height, it sends a command to control the motion control card 7 to output a signal to disconnect the electromagnetic clutch 420. The hammer head 47 strikes the moving part of the flexible hinge 43, causing it to drive the indenter 42 to complete an impact loading. The force and displacement information during the impact indentation test is picked up by the measurement unit 5.

[0060] Step 5: The moving portion of the flexible hinge 43 moves backward under the action of the deformation of the deformable portion of the flexible hinge 43 and strikes the hammer head 47, causing momentum exchange. The moving portion of the flexible hinge 43 stays at the impact point, and the entire body centered on the hammer head 47 begins to move backward, driving the pendulum shaft 418 to rotate in the opposite direction.

[0061] Step 6. At this time, the encoder 413 detects the reverse displacement value and sends it to the motion control card 7 and the control system 8 in real time. The program sends a control instruction to the electromagnetic clutch 420 to close it, and the pendulum shaft 418 is captured by the electromagnetic clutch 420. At this time, the motor 417 is in a self-locking state, and the pendulum shaft 418 no longer moves. The program waits for the operator to set it again, realizing a single impact loading of the pressure head 42 on the test piece 515 and preventing secondary loading.

[0062] From the above, it can be seen that the momentum exchange-driven impact indentation testing device described in the present invention uses program negative feedback control to raise the pendulum hammerhead to a set height. The pendulum then collides with the flexible hinge moving part under the action of gravity, generating momentum exchange. The flexible hinge moving part drives the indenter into the test piece, and a laser interferometer and piezoelectric force sensor measure the indentation displacement and force. When the pendulum hammerhead collides with the flexible hinge moving part, the light shield mounted on the hammerhead moves into the slit of the photoelectric switch, generating a trigger signal, which triggers the high-speed data acquisition card, high-speed camera, and thermal imager to collect data. Secondary impact loading is prevented through coordinated control of software and hardware. This device provides an experimental basis for conducting research on the mechanical properties of materials at high strain rates, and has significant application value in the study of the mechanical properties of key service materials in ultra-high-speed machining, aerospace, armor protection, and other fields.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements to the present invention are intended to fall within the scope of protection of the present invention.

[0064] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "up", "down", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0065] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0066] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0067] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A momentum exchange driven impact indentation testing device, characterized by: It includes an in-situ observation unit, a positioning and point change unit, a driving unit, a measuring unit, a data acquisition card, a motion control card and a control system; the in-situ observation unit is used to observe the pressing position on the test piece and transmit the deformation and heat distribution data of the test piece to the control system; the driving unit includes a first component and a second component of the same weight, and the first component swings and hits the second component to perform translational motion; the first component includes a pendulum rod, a hammer head fixedly connected to the lower end of the pendulum rod, a ball head fixedly connected to the front end of the hammer head and a light shielding plate installed at the lower end of the hammer head, and the center of gravity of the first component is located on the central axis of the ball head; the second component includes a flexible hinge, a pressure head fixedly connected to the front end of the moving part of the flexible hinge, and an impact block fixedly connected to the rear end of the moving part of the flexible hinge, and the center of gravity of the second component is located on the central axis of the moving part of the flexible hinge; when the ball head swings to the lowest point, the axis center and the axis center of the impact block are on the same horizontal line; the first component drives the pendulum rod to swing through the swing control component, and the swing control component The invention comprises a pendulum shaft, a motor and a frame for mounting the pendulum shaft, wherein the motor shaft and the pendulum shaft are connected via an electromagnetic clutch, and an encoder is mounted on the pendulum shaft; the test piece and the flexible hinge are both mounted on a positioning and point-changing unit, and are driven by the positioning and point-changing unit to perform X-axis positioning and YZ direction point-changing; the measuring unit comprises a laser interferometer, a piezoelectric force sensor, a right-angle prism, a reflector and a photoelectric switch, the test piece and the right-angle prism are mounted at the measuring end of the piezoelectric force sensor, the light beam emitted by the probe of the laser interferometer enters the right-angle prism and the plane reflector in sequence, the incident surface of the right-angle prism and the plane reflector are at an angle of 45 degrees, and the plane reflector is perpendicular to the axis of the pressure head; the axes of the pressure head, the test piece and the piezoelectric force sensor are parallel, and when the ball head is at the lowest point, the two ends of the light shield are located in the slits of the photoelectric switch; the control system receives and controls signals from the electromagnetic clutch, the motor and the encoder via a motion control card, and collects data from the photoelectric switch and the piezoelectric force sensor via a data acquisition card.

2. The momentum exchange driven impact indentation testing device according to claim 1, characterized in that: The in-situ observation unit includes a high-speed camera and a thermal imager, and the spatial positions of the high-speed camera and the thermal imager are adjusted respectively through the three-dimensional motion platform I and the three-dimensional motion platform II so that their observation axes and the indenter motion axis are in the same horizontal plane.

3. The momentum exchange driven impact indentation testing device according to claim 1, characterized in that: The top of the frame is fixedly connected with a mounting plate VI, the mounting plate VI is fixedly connected to the motor, and the pendulum shaft is mounted on the mounting plate VI through a support seat.

4. The momentum exchange driven impact indentation testing device according to claim 1, wherein: The motor shaft is connected to the transmission shaft through a reducer, and the transmission shaft is connected to the pendulum shaft through an electromagnetic clutch.

5. The momentum exchange driven impact indentation testing device according to claim 1, characterized in that: The positioning and point changing unit includes a base, a mounting plate IV, a mounting plate V, an X-axis macro positioning platform, an adapter plate III, and an X-axis micro positioning platform. The mounting plate IV is mounted on the base, the mounting plate V is mounted on the mounting plate IV, and the mounting plate V can be adjusted forward and backward along the X-axis direction through the long keyhole on the mounting plate V. The X-axis macro positioning platform is mounted on the mounting plate V. There is a reinforcement plate on each side of the X-axis macro positioning platform mounted on the mounting plate V. The thickness of the reinforcement plate is lower than the height of the installation plane of the X-axis macro positioning platform. The adapter plate III is mounted on the X-axis macro positioning On the platform installation plane, the X-axis micro positioning platform is installed on the adapter plate III, the adapter plate IV, the reinforcement rib plate, and the adapter plate V are fixedly connected, the adapter plate IV is installed on the X-axis micro positioning platform, the YZ point changing platform is installed on the adapter plate V, and the adapter plate VI is installed on the YZ point changing platform. The X-axis macro positioning platform drives the YZ point changing platform and the X-axis micro positioning platform to perform macro movement and positioning along the X-axis. The X-axis micro positioning platform drives the YZ point changing platform to perform micro movement and positioning along the X-axis. The YZ point changing platform drives the piezoelectric force sensor and the specimen table to change points along the YZ direction.

6. The momentum exchange driven impact indentation testing device according to claim 1, characterized in that: The probe is installed on the three-dimensional motion platform III through the probe base. The probe is connected to the laser interferometer controller through an optical fiber. The probe adjusts its spatial position through the three-dimensional motion platform III so that its measurement axis is in the same horizontal plane as the center of the right-angle prism and the center of the reflector, and the incident light and the reflected light of the reflector coincide and are parallel to the axis of the indenter, thereby realizing the measurement of the indentation displacement.

7. The momentum exchange driven impact indentation testing device according to claim 1, characterized in that: The measuring end of the piezoelectric force sensor is fixedly connected to an adapter plate VII, and the right-angle prism and the tested object are mounted on the same side of the adapter plate VII.

8. The momentum exchange driven impact indentation testing device according to claim 1, characterized in that: The photoelectric switch is installed on the photoelectric switch seat through the mounting frame and the adapter frame, and the photoelectric switch seat is installed on the mounting plate V.

9. The momentum exchange driven impact indentation testing device according to claim 1, characterized in that: The testing device further comprises a vibration isolation platform, on which the in-situ observation unit, the positioning and point changing unit, the driving unit and the measuring unit are all mounted.

10. A momentum exchange driven impact indentation test method, characterized in that: The momentum exchange driven impact indentation testing device according to claim 1 is implemented, comprising the following steps: Step 1: Use the X-axis macro positioning platform, X-axis micro positioning platform and YZ point changing platform to bring the test piece into pre-contact with the indenter, and then lock the three platforms; Step 2: Keep the electromagnetic clutch normally closed, and the encoder will provide real-time feedback of the pendulum shaft position and motion status to the motion control card and control system; Step 3: After setting the pendulum lifting height, the measurement begins. The control system monitors the operating status of the test device according to the feedback value of the encoder and gives instructions. The control command is sent from the control system to the motion control card. The motion control card outputs an electrical signal to drive the motor to drive the pendulum to the set height. Step 4: The control system detects that the feedback value of the encoder matches the set height, sends a command to control the motion control card to output a signal to disconnect the electromagnetic clutch, and the hammer head hits the moving part of the flexible hinge to drive the indenter to complete an impact loading. The force and displacement information during the impact indentation test is picked up by the measurement unit; Step 5: The flexible hinge moving part moves backward under the deformation of the flexible hinge deforming part to strike the hammer head to exchange momentum. The flexible hinge moving part stays at the impact point, and the whole body centered on the hammer head starts to move backward, driving the pendulum shaft to rotate in the opposite direction. Step 6: The encoder detects the reverse displacement value and sends it to the motion control card and control system in real time. The control system sends a control instruction to the electromagnetic clutch to close it. The pendulum shaft is captured by the electromagnetic clutch, the motor is in a self-locking state, and the pendulum shaft stops moving. The dynamic hardness of the test piece can be calculated based on the force and displacement information of the impact indentation process. The formula is in H Dyn is the dynamic hardness, m eff is the sum of the equivalent mass of the moving part of the flexible hinge and the pressure head, V inciden t is the speed of the indenter when it just contacts the test piece, V rebound is the speed of the indenter at the same position after it completes the pressing. h rest is the residual depth of the impact indentation, f DAF ( h ) is the area function of the pressure head; Step 7: During the impact indentation process, the strain rate at different times and in different deformation areas will change, and the indentation depth will be h The strain rate is The average strain rate of the entire process is used as the characteristic strain rate of the experiment. Through multiple experiments with different impact energies, the mapping relationship between the characteristic strain rate and dynamic hardness of the test piece is established to obtain the dynamic mechanical properties of the test piece.

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