A compression strain control mechanism and a hopkinson bar testing device

Abstract

This invention discloses a compression strain control mechanism and a Hopkinson bar testing device. The compression strain control mechanism includes a base, a limiting sleeve, a flexible support ring, and an adjusting screw. The base has a guide hole larger than the diameter of the Hopkinson bar; the limiting sleeve slides within the guide hole, and its inner ends are respectively provided with limiting holes and adjusting threaded holes, the diameter of the limiting hole being 0.5 to 0.7 times the diameter of the Hopkinson bar; the flexible support ring is sleeved on the test piece and fits within the limiting hole; the adjusting screw is screwed into the adjusting threaded hole and its inner end extends into the limiting hole, both ends of which have flat force transmission planes; the front end of the limiting sleeve is located within the guide hole, forming a protective space. This invention achieves precise adjustment of the plastic deformation of the test piece through the adjusting screw; and effectively prevents the splashing of sample debris through the protective space, significantly improving the accuracy and safety of the experiment.

Description

Technical Field

[0001] This invention relates to the field of dynamic mechanical property testing and high strain rate experimental technology for materials, specifically to a compression strain control mechanism and a Hopkinson bar testing device. Background Technology In the study of dynamic mechanical properties of materials, when using the Hopkinson bar test apparatus for impact compression tests, the test results obtained are the results under the entire loading pulse. However, the damage state of the specimen after the test is the state after multiple loadings. For materials with small failure strain, the specimen is usually in a fractured state after the test. Depending on the requirements of the material's service conditions, it is sometimes necessary to set and control the compressive strain of the specimen during the test to study the mechanical properties of the material under specific strain and to analyze the material's failure morphology. Therefore, it is necessary to achieve effective compressive strain control in the traditional Hopkinson bar test.

[0002] To address this, several related patents have been published in Chinese patent literature, such as those with publication numbers CN106483028A and CN210638994U, which involve setting a fixed-height "bearing ring" or "blocking ring" between the incident rod and the transmission rod. However, the fixed height of this "bearing ring" or "blocking ring" makes multi-level adjustment impossible, requiring customization of different sizes of "bearing ring" or "blocking ring" according to different compression amounts. Furthermore, gaps are reserved within the ring to allow for specimen expansion, causing the specimen to sag under gravity and fail to maintain coaxiality with the incident rod, severely affecting the accuracy of stress wave transmission. To solve these coaxiality and jamming problems, patents with publication numbers CN112146986A and CN116165083A employ an upper and lower spliced ​​"sleeve" to enclose the specimen, removing the sleeve and extracting the deformed specimen after testing. However, this rigid wrapping method imposes additional radial constraints on the specimen during testing, affecting the actual axial deformation of the specimen and the accuracy of the test; moreover, the fixed-diameter sleeve is not compatible with test specimens of different diameters. Summary of the Invention

[0003] To address the shortcomings of the prior art, the technical problem to be solved by the present invention is: how to provide a compression strain control mechanism and Hopkinson bar testing device that is convenient for controlling and adjusting deformation, compatible with specimens of various diameters, ensures coaxiality while providing radial deformation space for the specimen, and facilitates non-destructive removal of the specimen after testing.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A compression strain control mechanism, comprising: The base has a guide hole that extends through the axial direction of the Hopkinson bar, the diameter of which is larger than the diameter of the Hopkinson bar; A limiting sleeve is slidably fitted coaxially within the guide hole. One end of the limiting sleeve has a coaxially arranged limiting hole, and the other end has a coaxially penetrating adjusting threaded hole. The diameter of the adjusting threaded hole is less than or equal to the inner diameter of the limiting hole, and the diameter of the limiting hole is 0.5 to 0.7 times the diameter of the Hopkinson rod. A flexible support ring is used to be fitted onto the test piece; the outer diameter of the flexible support ring matches the inner diameter of the limiting hole and is detachably fitted into the limiting hole; An adjusting screw is adjusted by threading at one end of the adjusting screw thread hole away from the limiting hole. The outer end of the adjusting screw has at least two parallel planes in the circumferential direction, and the inner end is located inside the limiting hole. Both ends of the adjusting screw have flat force transmission planes. The end of the limiting sleeve that is away from the adjusting screw is located inside the guide hole to form a protective space.

[0005] As an optimization, two parallel adjusting planes are symmetrically arranged on the outer peripheral wall of the limiting sleeve. Each adjusting plane has a strip-shaped hole that extends radially through the limiting sleeve, and the strip-shaped hole is located axially at the end of the limiting hole closest to the adjusting threaded hole. The strip-shaped hole extends axially along the limiting sleeve and its width is greater than the diameter of the test piece. A plug block that can move along the strip-shaped hole is inserted into the strip-shaped hole. An arc-shaped groove communicating circumferentially with the limiting sleeve is formed between the two adjusting planes. Adjusting plug pieces, integrally U-shaped, are detachably engaged at the arc-shaped groove and the two adjusting planes. The adjusting plug piece abuts against the side of the plug block opposite to the adjusting screw. The outer contour of the adjusting plug piece is circular, and its diameter is the same as the diameter of the limiting sleeve, and it is coaxially fitted onto the limiting sleeve.

[0006] Furthermore, the two adjustment planes are vertically oriented, and the arc-shaped groove is located at the top of the limiting sleeve.

[0007] Furthermore, the vertical distance from the adjustment plane to the axis of the limiting sleeve is greater than the radius of the limiting hole; the cross-sectional area of ​​the limiting sleeve at the two adjustment planes is greater than or equal to the cross-sectional area of ​​the Hopkinson rod.

[0008] As an optimization, the inner wall of the guide hole has a guide groove that is opened along the axial direction; the outer peripheral wall of the limiting sleeve is provided with an anti-rotation protrusion, and the anti-rotation protrusion is slidably fitted in the guide groove.

[0009] As an optimization, the end of the guide hole opposite to the protective space has an annular limiting ring, the inner diameter of which is larger than the diameter of the adjusting screw and the Hopkinson rod; a removable baffle is also provided on the inner side of the limiting ring, and a locking mechanism is provided between the base and the limiting sleeve for abutting the adjusting screw against the baffle to form a fixed position.

[0010] Furthermore, the limiting retaining ring is integrally formed on the base, and the locking mechanism includes a pressure ring detachably installed on the side of the guide hole away from the limiting retaining ring. The inner hole of the pressure ring is coaxially arranged with the guide hole and its diameter is larger than that of the Hopkinson rod. A helical spring is provided between the pressure ring and the limiting sleeve for compression.

[0011] Furthermore, the material strength and elastic modulus of the limiting sleeve, the adjusting screw, the plug block, and the adjusting plug are all not less than the material strength and elastic modulus of the Hopkinson rod.

[0012] Furthermore, multiple adjustable plugs are provided, each with a different standard thickness; the outer surface of the adjustable plug is engraved with marking information matching the standard thickness; and the outer wall of the limiting sleeve is provided with scale lines along the axial direction to indicate the adjustment depth.

[0013] Furthermore, the base has an integrally formed base plate, the base plate has a positioning groove that matches the support guide rail of the Hopkinson bar experimental system, the positioning groove is arranged through the axial direction of the guide hole; the base plate is also provided with a through-hole for fixing fastening bolts.

[0014] Compared with the prior art, the present invention has the following advantages: 1. This invention uses an adjusting bolt to hold the test piece against itself, thereby controlling the length of the test piece extending from the limiting hole. Since the diameter of the limiting hole is 0.5 to 0.7 times the diameter of the Hopkinson bar, once the test piece is compressed, the Hopkinson bar will directly impact the end face of the limiting sleeve, thus preventing further compression of the test piece. Simultaneously, a flexible support ring supports the test piece within the limiting hole, ensuring reliable coaxiality between the test piece and the Hopkinson bar while providing sufficient space for expansion and deformation.

[0015] 2. This invention employs a structure of a radially penetrating strip-shaped hole, a plug block, and a U-shaped adjusting plug. Upon impact, the residual impact force absorbed by the limiting sleeve is sequentially transmitted through the front wall of the strip-shaped hole, the adjusting plug, and the plug block, ultimately reaching the flat inner end face of the adjusting screw. This force transmission path directly bypasses the threaded connection surface between the limiting sleeve and the adjusting screw, converting the impact shear force borne by the threads into pure compressive stress between the end faces of each component, effectively avoiding thread stripping and breakage under high strain rate impacts.

[0016] 3. In this invention, the outer contour of the adjustable plug is designed to be circular with the same diameter as the limiting sleeve. When the limiting sleeve slides into the guide hole of the base, the inner wall of the guide hole naturally forms a radial physical enclosure and limitation on the adjustable plug. This radial self-locking design eliminates the need for additional fasteners and prevents the plug from coming off under high-frequency vibration; at the same time, the closed space formed by the guide hole and the limiting sleeve can effectively prevent the splashing of specimen fragments.

[0017] 4. The base of the present invention also has a limiting ring, which allows the limiting sleeve to abut against the limiting ring under the action of the bolt to form a fixed position, thus satisfying the impact test of double-sided force transmission and the impact test of single-sided force. Attached Figure Description

[0018] Figure 1 This is a structural diagram of the base.

[0019] Figure 2 for Figure 1 A cross-sectional structural diagram.

[0020] Figure 3 This is a schematic diagram of the limiting sleeve.

[0021] Figure 4 for Figure 3 A cross-sectional structural diagram.

[0022] Figure 5 This is a structural diagram showing the assembly state of the limiting sleeve, plug, adjusting plug, and adjusting bolt.

[0023] Figure 6 for Figure 5 A schematic diagram of its decomposed structure.

[0024] Figure 7 This is a schematic cross-sectional view of the overall structure under impact test conditions with a transmission rod.

[0025] Figure 8 This is a schematic cross-sectional view of the overall structure under impact test conditions without the transmission rod. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments.

[0027] This embodiment provides a Hopkinson bar testing apparatus, mainly used in a split Hopkinson bar (SHPB) testing system. It includes a compression strain control mechanism, and works with an incident bar 9, a transmission bar 10, and related testing instruments to conduct dynamic impact compression tests. The compression strain control mechanism includes a base 1, as shown below. Figure 1 and Figure 2As shown, the base 1 has a guide hole 11 extending through the axial direction of the Hopkinson rod. The diameter of the guide hole 11 is larger than the diameter of the Hopkinson rod, allowing the Hopkinson rod to extend into the guide hole 11. The base 1 has an integrally formed base plate 13, which has a positioning groove 14 that matches the support rail of the Hopkinson rod experimental system. The positioning groove 14 extends through the axial direction of the guide hole 11. The base plate 13 also has through-holes 15 for fixing. The base 1 engages with the support rail of the Hopkinson rod experimental system through the positioning groove 14, forming a positioning in the axial and width directions. It is then fixedly connected to the platform of the Hopkinson rod experimental system by bolts passing through the fastening bolt holes, providing reliable support.

[0028] The guide hole 11 is coaxially and slidably fitted with a limiting sleeve 2, such as Figure 3 and Figure 4 As shown, one end of the limiting sleeve 2 has a coaxially arranged limiting hole 21, and the other end has a coaxially through adjusting threaded hole 22. The diameter of the adjusting threaded hole 22 is less than or equal to the inner diameter of the limiting hole 21, and the inner diameter of the limiting hole 21 is 0.5 to 0.7 times the diameter of the Hopkinson rod. Since the inner diameter of the limiting hole 21 is 0.5 to 0.7 times the diameter of the Hopkinson rod, the Hopkinson rod can only abut against the outer end face of the limiting hole 21, and the area of ​​the annular bearing surface formed by the two abutting against each other is not less than half of the end face area of ​​the Hopkinson rod. This ensures that the end face of the limiting sleeve has sufficient bearing capacity, thereby reliably limiting the impact of the Hopkinson rod.

[0029] The end of the adjustable threaded hole 22 opposite to the limiting hole 21 is adjustablely fitted with an adjusting screw 4 via a thread. The outer end of the adjusting screw 4 has at least two parallel planes in the circumferential direction, and the inner end is located inside the limiting hole 21. In this embodiment, the outer end of the adjusting screw 4 is a regular hexagonal nut. Unlike traditional screws, both ends of the adjusting screw 4 in this embodiment have flat force transmission planes, so that both ends of the adjusting screw 4 can reliably fit and abut against the adjacent force-bearing or force-applying component, and bear and transmit axial impact force.

[0030] It also includes a flexible support ring 3 for fitting onto the test piece. The outer diameter of the flexible support ring 3 matches the inner diameter of the limiting hole 21 and is detachably fitted within the limiting hole 21. The flexible support ring 3 is made of an elastic material, such as silicone or rubber. This allows sufficient expansion and deformation space in the circumferential direction of the test piece, and also enables the test piece to be coaxially positioned within the limiting hole 21, ensuring coaxiality between the test piece and the Hopkinson bar. This method is more stable and reliable than the traditional method of using grease to position the test piece during experiments.

[0031] In this embodiment, the length of the guide hole 11 is greater than the length of the limiting sleeve 2, and the end of the limiting sleeve 2 that is away from the adjusting screw 4 is located inside the guide hole 11 to form a protective space.

[0032] Considering the different lengths and compression amounts of various test specimens, this embodiment also includes an adjustment structure for the specimen insertion depth. Specifically, two parallel adjusting planes 23 are symmetrically arranged on the outer peripheral wall of the limiting sleeve 2. Each adjusting plane 23 has a strip-shaped hole 24 that extends radially through the limiting sleeve 2. The width of the strip-shaped hole 24 is greater than the diameter of the test specimen. The strip-shaped hole 24 extends axially along the limiting sleeve 2 and is located axially near the adjusting threaded hole 22. One end; a plug 5 that can move along the strip hole 24 is inserted into the strip hole 24; an arc-shaped groove 25 that communicates circumferentially with the limiting sleeve 2 is opened between the two adjusting planes 23; an adjusting plug 6 that is integrally U-shaped is detachably engaged at the arc-shaped groove 25 and the two adjusting planes 23; the adjusting plug 6 abuts against the side of the plug 5 away from the adjusting screw 4; the outer contour of the adjusting plug 6 is circular and its diameter is the same as the diameter of the limiting sleeve 2, and it is coaxially fitted on the limiting sleeve 2. Figure 5 and Figure 6 As shown, multiple adjustable plugs 6 are provided, each with a different standard thickness; the outer surface of each adjustable plug 6 is engraved with marking information matching the standard thickness; the outer wall of the limiting sleeve 2 is provided with axially arranged scale lines (not shown in the figure) for indicating the adjustment depth. The material strength and elastic modulus of the limiting sleeve 2, the adjusting screw 4, the plug block 5, and the adjustable plug 6 are all not less than the material strength and elastic modulus of the Hopkinson rod.

[0033] During testing, at least two flexible support rings 3 are fitted onto the test piece, and the test piece is supported within the limiting hole by the flexible support rings 3, so that the end of the test piece abuts against the plug block 5. The insertion depth of the test piece is calculated based on its length and preset compression amount. Based on the insertion depth and the initial distance from the adjusting plane 23 to the end face of the limiting sleeve 2 facing the protective space, the thickness of the adjusting plug is calculated. Based on this thickness, an appropriate number and thickness of adjusting plugs 6 are selected and placed on the side of the plug block 5 away from the adjusting screw 4. The adjusting screw 4 is adjusted so that the inner end of the adjusting screw 4 abuts against the plug block 5, and both ends of the plug block 5 abut against the adjusting plugs 6, so that the adjusting screw 4, the plug block 5, the adjusting plugs 6, and the base form a stable and reliable force-bearing whole.

[0034] To prevent the limiting sleeve 2 from rotating within the guide hole 11, in this embodiment, the inner wall of the guide hole 11 has a guide groove 12 opened along the axial direction; the outer peripheral wall of the limiting sleeve 2 is provided with an anti-rotation protrusion 26, which is slidably fitted within the guide groove 12.

[0035] To allow the adjusting insert 6 to be better positioned on the arc-shaped groove 25, the two adjusting planes 23 are vertically arranged, and the arc-shaped groove 25 is located at the top of the limiting sleeve 2. Simultaneously, the vertical distance from the adjusting plane 23 to the axis of the limiting sleeve 2 is greater than the radius of the limiting hole 21; the cross-sectional area of ​​the limiting sleeve 2 at the two adjusting planes 23 is greater than or equal to the cross-sectional area of ​​the Hopkinson rod.

[0036] Considering that a unilateral impact test may be required during the specific experiment, in this embodiment, the end of the guide hole 11 facing away from the protective space has an annular limiting ring. The inner diameter of the limiting ring is larger than the diameter of the adjusting screw 4 and the Hopkinson rod. A removable baffle 7 is also provided on the inner side of the limiting ring. A locking mechanism is provided between the base 1 and the limiting sleeve 2 to abut the adjusting screw 4 against the baffle 7 to form a fixed lock.

[0037] To further improve the stress distribution on the base, the limiting retaining ring is integrally formed on the base 1. The locking mechanism includes a pressure ring 8 detachably mounted on the side of the guide hole 11 opposite to the limiting retaining ring. The inner hole of the pressure ring 8 is coaxially arranged with the guide hole 11, and its diameter is larger than the diameter of the Hopkinson rod. A compressed helical spring (not shown in the figure) is provided between the pressure ring 8 and the limiting sleeve 2. In this embodiment, the pressure ring 8 is fixedly mounted on the base 1 by a plurality of bolts evenly distributed along the circumference.

[0038] Based on the above structure, this device can flexibly adapt to different experimental modes. During a conventional precision controlled impact test with a transmission rod, the base 1 is first fixed to the support rail of the Hopkinson pressure bar via a positioning groove and fastening bolts. Next, the test piece with the flexible support ring 3 is inserted into the limiting hole 21 of the limiting sleeve 2. Based on the preset target amount of plastic deformation, an adjustable plug 6 with a corresponding thickness combination is selected and inserted from top to bottom along the arc groove 25 to the rear side of the plug block 5. Then, the adjusting screw 4 is rotated so that its flat inner end face tightly presses against the plug block 5 to eliminate internal assembly gaps. After completing the internal assembly of the test piece and the limiting sleeve 2, the limiting sleeve 2 is pushed into the base 1 along the guide hole 11. The sliding cooperation between the anti-rotation protrusion 26 and the guide groove 12 keeps the adjustable plug 6 always facing upwards, while a splash-proof enclosed protective space is formed inside the base 1. Finally, apply a suitable amount of lubricant to the end faces of the incident rod 9 and the transmission rod 10 to reduce end face friction, and push the two rods to extend into the guide holes 11 from both sides and fit against the two end faces of the specimen. Figure 7 As shown. After the firing system is activated, the impact load of the incident rod 9 causes plastic compression of the specimen. When the specimen deforms to the preset value, the excess residual impact force will be transmitted sequentially to the end face of the adjusting screw 4 via the adjusting plug 6 and the plug block 5. This stress transmission path removes the axial impact load from the threaded connection, achieving precise deformation cutoff while protecting the adjusting threaded hole 22 from shear damage.

[0039] When a single-sided independent impact forming test is required without the transmission rod, the transmission rod can be removed and a single-sided fixing structure can be used. During operation, firstly, a solid baffle 7 is inserted into the end of the guide hole 11 away from the protective space, so that it abuts against the inner side of the limiting retaining ring. Following the same assembly method described above, the limiting sleeve 2, containing the specimen, adjusting plug 6, and adjusting screw 4, is pushed into the guide hole 11 of the base 1, so that the outer end face of the adjusting screw 4 abuts against the baffle 7. Subsequently, a pressure ring 8 is fixedly installed on the side of the base 1 facing the incident rod 9, so that the coil spring compressed between the pressure ring 8 and the limiting sleeve 2 generates a continuous backward elastic force. This elastic force pushes the limiting sleeve 2 and the internal adjusting screw 4 backward as a whole, so that the outer end face of the adjusting screw 4 reliably abuts against the baffle 7, as... Figure 8 As shown. In this single-sided fixed mode, when the incident rod 9 applies an extremely high impact load to the specimen, the impact force will pass through the plug 5 and the adjusting screw 4 in sequence and be directly transmitted to the baffle 7, and finally absorbed by the integrally formed limiting ring on the base 1 and the experimental platform. This process ensures that the huge impact force is completely rigidly borne by the large-area metal end face, completely eliminating the risk of thread failure between the adjusting screw 4 and the adjusting threaded hole 22, and meeting the requirements of dynamic forming test of high strain rate materials under conditions without a transmission rod.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A compression strain control mechanism, characterized in that, include: The base (1) has a guide hole (11) that extends through the axial direction of the Hopkinson rod, the diameter of which is larger than the diameter of the Hopkinson rod. The limiting sleeve (2) is slidably fitted coaxially in the guide hole (11). One end of the limiting sleeve (2) has a limiting hole (21) coaxially arranged, and the other end has a coaxially penetrating adjusting thread hole (22). The diameter of the adjusting thread hole (22) is less than or equal to the inner diameter of the limiting hole (21). The diameter of the limiting hole (21) is 0.5 to 0.7 times the diameter of the Hopkinson rod. A flexible support ring (3) is used to be fitted onto the test piece; the outer diameter of the flexible support ring (3) matches the inner diameter of the limiting hole (21) and is detachably fitted into the limiting hole (21); The adjusting screw (4) is adjusted by thread to fit into the adjusting threaded hole (22) at one end away from the limiting hole (21). The outer end of the adjusting screw (4) has at least two mutually parallel planes in the circumferential direction, and the inner end is located in the limiting hole (21). Both ends of the adjusting screw (4) have flat force transmission planes. The end of the limiting sleeve (2) facing away from the adjusting screw (4) is located in the guide hole (11) to form a protective space.

2. The compression strain control mechanism according to claim 1, characterized in that, Two parallel adjusting planes (23) are symmetrically arranged on the outer peripheral wall of the limiting sleeve (2). The adjusting plane (23) has a strip hole (24) that runs radially through the limiting sleeve (2), and the strip hole (24) is located axially at the end of the limiting hole near the adjusting threaded hole (22). The strip hole (24) extends axially along the limiting sleeve (2) and its width is greater than the diameter of the test piece. A movable part is inserted into the strip hole (24). The plug (5); an arc groove (25) is provided between the two adjustment planes (23) and is connected in the circumference of the limiting sleeve (2); an adjustment plug (6) in the whole U shape is detachably clamped at the arc groove (25) and the two adjustment planes (23); the adjustment plug (6) abuts against the side of the plug (5) away from the adjustment screw (4); the outer contour of the adjustment plug (6) is circular and the diameter is the same as the diameter of the limiting sleeve (2), and it is coaxially fitted on the limiting sleeve (2).

3. The compression strain control mechanism according to claim 2, characterized in that, The two adjustable planes (23) are vertically arranged, and the arc groove (25) is located at the top of the limiting sleeve (2).

4. The compression strain control mechanism according to claim 2, characterized in that, The vertical distance from the adjustment plane (23) to the axis of the limiting sleeve (2) is greater than the radius of the limiting hole (21); the cross-sectional area of ​​the limiting sleeve (2) at the two adjustment planes (23) is greater than or equal to the cross-sectional area of ​​the Hopkinson rod.

5. The compression strain control mechanism according to claim 1, characterized in that, The inner wall of the guide hole (11) has a guide groove (12) opened along the axial direction; the outer peripheral wall of the limiting sleeve (2) is provided with an anti-rotation protrusion (26), which is slidably fitted in the guide groove (12).

6. The compression strain control mechanism according to claim 1, characterized in that, The guide hole (11) has an annular retaining ring at one end away from the protective space. The inner diameter of the retaining ring is larger than the diameter of the adjusting screw (4) and the Hopkinson rod. A removable baffle (7) is also provided on the inner side of the retaining ring. The base (1) and the retaining sleeve (2) have a locking mechanism for abutting the adjusting screw (4) against the baffle (7) to form a fixed position.

7. The compression strain control mechanism according to claim 6, characterized in that, The limiting retaining ring is integrally formed on the base (1). The locking mechanism includes a pressure ring (8) detachably installed on the side of the guide hole (11) away from the limiting retaining ring. The inner hole of the pressure ring (8) is coaxially arranged with the guide hole (11) and its diameter is larger than that of the Hopkinson rod. There is a compressed helical spring between the pressure ring (8) and the limiting sleeve (2).

8. The compression strain control mechanism according to claim 2, characterized in that, The material strength and elastic modulus of the limiting sleeve (2), the adjusting screw (4), the plug (5), and the adjusting plug (6) are all not less than the material strength and elastic modulus of the Hopkinson rod.

9. The compression strain control mechanism according to claim 2, characterized in that, Multiple adjustable plugs (6) are provided, and they have different standard thicknesses; the outer surface of the adjustable plugs (6) is engraved with identification information that matches the standard thickness; the outer side wall of the limiting sleeve (2) is provided with scale lines along the axial direction to indicate the adjustment depth.

10. A Hopkinson bar testing apparatus, characterized in that, Includes the compression strain control mechanism as described in any one of claims 1 to 9.

Images