Hopkinson pressure bar testing device for controllable continuous multi-pulse loading

Abstract

A Hopkinson pressure bar test device for controllable continuous multi-pulse loading belongs to the technical field of material high-strain-rate dynamic mechanical property testing, and aims at solving the problem that the existing multi-pulse loading test cannot accurately control the pulse width of each loading. The device comprises a bullet rod launching unit, multi-stage bullet rods and an incident rod, the bullet rod launching unit launches the multi-stage bullet rods on the incident rod; the multi-stage bullet rods are of n-stage sleeve type structure, the incident rod is provided with n rings of shapers at the end, and each ring of shapers corresponds to the position of one-stage bullet rod; the bullet rod launching unit launches the multi-stage bullet rods, and the n-stage bullet rods of the multi-stage bullet rods hit the corresponding shapers at the end of the incident rod from the outer stage to the inner stage in sequence to realize multi-pulse loading. The device independently designs the loading pulses formed by n times of collision in cooperation with the shapers.

Description

Technical Field

[0001] This invention belongs to the field of dynamic mechanical property testing technology for materials at high strain rates. Background Technology

[0002] In engineering, rocks and other brittle materials are frequently subjected to multiple impact loads in a short period, such as during explosive processes. An important research focus in studying these problems is investigating the influence of loading history paths at high strain rates on the mechanical response of materials.

[0003] Numerous studies have shown that the constitutive relations, damage, phase transformation, and stress relaxation behaviors of materials are all related to their loading history. Investigating the influence of historical loading paths on the mechanical response of materials typically involves cyclic loading and unloading tests. Under quasi-static and low strain rate conditions, these tests are generally performed using a universal testing machine. The key to performing loading and unloading tests at high strain rates is achieving continuous and precisely controllable multi-pulse loading. Although some scholars and engineers have conducted multi-pulse loading tests—for example, patent CN11948074A discloses a multi-pulse loaded bullet simulating a penetration process, and patent CN113848132A discloses a gunpowder-driven long-pulse loading device—the problem of individually and precisely controlling the width of each loading pulse in multi-pulse loading remains. Therefore, there is an urgent need for a controllable continuous multi-pulse loading test device and method that can achieve individual and precise control of the amplitude, pulse width, and waveform of each pulse under laboratory conditions. Summary of the Invention

[0004] To address the problem that existing multi-pulse loading tests cannot accurately control the width of each loading pulse, this invention provides a Hopkinson bar testing device for controllable continuous multi-pulse loading.

[0005] The Hopkinson bar test apparatus for controllable continuous multi-pulse loading described in this invention includes a bullet bar launching unit 2, a multi-stage bullet bar 3, and an incident bar 4. The bullet bar launching unit 2 launches the multi-stage bullet bar 3 to hit the incident bar 4.

[0006] The multi-stage bullet rod 3 is an n-stage sleeve structure, where n>2. The multi-stage bullet rod 3 includes an outer barrel bullet rod, a central cylindrical bullet rod, and n-2 intermediate cylindrical bullet rods. The outer barrel bullet rod is a barrel-shaped structure with closed ends and open ends. The n-2 intermediate cylindrical bullet rods are sleeved inside the outer barrel bullet rod and outside the central cylindrical bullet rod. The n-stage bullet rods can slide relative to each other along the axial direction. The axial length of all bullet rods decreases sequentially from the outside to the inside.

[0007] The end of the incident rod 4 is equipped with n rings of shapers, each ring of shaper corresponding to the position of the first-stage bullet rod;

[0008] The bullet rod launching unit 2 launches a multi-stage bullet rod 3. The n-stage bullet rods of the multi-stage bullet rod 3 strike the shaper corresponding to the end of the incident rod 4 in sequence from the outer stage to the inner stage, thereby achieving multi-pulse loading.

[0009] Preferably, n-1 screws are provided at the end of the outer barrel bullet rod. The n-1 screws are screwed into the end of the outer barrel bullet rod and press against the end of each bullet rod. Each screw is screwed into a different depth to adjust the distance between each bullet rod and the head end of the multi-stage bullet rod 3.

[0010] Preferably, each screw is secured in its axial position with a nut.

[0011] Preferably, each ring of shapers is arranged in a circular pattern with m shapers arranged in the circumferential direction, where m = 1 to 12, and from the outside to the inside, they are the 1st ring, the 2nd ring, ..., the nth ring. The nth ring has 1 shaper or an even number of shapers arranged symmetrically in the circumferential direction, and the 1st ring, the 2nd ring, ..., the (n-1th ring) all have an even number of shapers arranged symmetrically in the circumferential direction.

[0012] Preferably, the bullet rods of the multi-stage bullet rod 3 are defined from the outside to the inside as stage 1, stage 2, ..., stage n. The axial lengths of the n-stage bullet rods are L1, L2, ..., Ln, respectively. The axial gap between the tip of the stage 2 bullet rod and the tip of the stage 1 bullet rod is defined as d1. The axial gaps between the tips of adjacent stages are defined as d1, d2, d3, ..., dn-1, respectively. The cross-sectional areas of the n-stage bullet rods are A1, A2, ..., An, respectively. The total area of ​​each ring in the n-ring shaper is B1, B2, ..., Bn, respectively. The waveform of the multi-pulse is adjusted by adjusting the axial gaps d1, d2, d3, ..., dn-1 between the tips of adjacent stages, the cross-sectional areas A1, A2, ..., An of the n-stage bullet rods, and the total area B1, B2, ..., Bn of each ring in the n-ring shaper.

[0013] Preferably, the shaping device is made of brass or lead.

[0014] Preferably, the size of the shaper is smaller than the wall thickness of the corresponding grade bullet rod.

[0015] Preferably, the axial clearance d1, d2, d3, ... dn-1 between adjacent first ends is selected as 5mm to 10mm.

[0016] The beneficial effects of this invention are:

[0017] 1. This invention is based on the Hopkinson pressure bar platform and modifies the bullet to form controllable continuous multi-pulse in the incident rod. It has low modification cost for existing equipment and is easy to promote and use.

[0018] 2. This invention employs a semi-open multi-stage bullet structure. The outermost first-stage bullet is a hollow, closed-tail structure with an open impact end. The next outermost second-stage bullet is also a hollow, uniform-section cylindrical structure, and the innermost third-stage bullet is a solid round rod structure. The pulse width is determined by the bullet length and the shaper. Since the three impacts are caused by the three bullet rods striking the bullet rods independently and sequentially, and each bullet stage can be shaped independently without interference, the loading pulses generated by the three impacts can be independently designed in conjunction with the shaper. This ensures that each loading pulse is individually controllable, maintaining a constant strain rate for the sample during each loading. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the Hopkinson bar testing device for controllable continuous multi-pulse loading as described in this invention;

[0020] Figure 2 This is a diagram showing the connection between the multi-stage bullet rod and the incident rod;

[0021] Figure 3 This is a diagram showing the distribution of the shaper at the end of the incident rod;

[0022] Figure 4 This is a diagram showing the propagation of the pulse in the incident rod when the bullet rod is working without using a shaper;

[0023] Figure 5 This is a typical multi-pulse loading signal diagram without deformation: the loading pulse amplitudes are equal;

[0024] Figure 6 This is a typical multi-pulse loading signal diagram using shaping: the loading pulse amplitude decreases sequentially;

[0025] Figure 7 This is a typical multi-pulse loading signal diagram using shaping: the loading pulse amplitude increases sequentially. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0029] Specific Implementation Method 1: The following is combined with... Figures 1 to 7 This embodiment describes the Hopkinson bar testing apparatus for controllable continuous multi-pulse loading. See [link to previous document]. Figure 1 The test platform is based on a Hopkinson pressure bar platform and includes a fixed support platform 1, a bullet launch unit 2, multi-stage bullet rods 3, an incident rod 4, a transmission rod 5, an absorption rod 6, a buffer 7, and a sample 8. The fixed support platform 1 supports the launch unit 2, the incident rod 4, the transmission rod 5, the absorption rod 6, and the buffer 7. The multi-stage bullet rods 3 are located inside the launch tube of the launch unit 1. Multiple stress wave pulses are generated by the sequential impact of each stage of the multi-stage bullet rods 3 against the incident rod 4, loading the sample 8 between the incident rod 4 and the transmission rod 5. The bullet launch unit 2 is powered by high-pressure gas and includes a gas chamber, control valves, and a launch tube. The materials of each stage of the multi-stage bullet rods 3, the incident rod 4, and the transmission rod 5 can be the same or different.

[0030] The multi-stage bullet rod 3 is an n-stage sleeve structure, where n>2. The multi-stage bullet rod 3 includes an outer barrel bullet rod, a central cylindrical bullet rod, and n-2 intermediate cylindrical bullet rods. The outer barrel bullet rod is a barrel-shaped structure with closed ends and open ends. The n-2 intermediate cylindrical bullet rods are sleeved inside the outer barrel bullet rod and outside the central cylindrical bullet rod. The n-stage bullet rods can slide relative to each other along the axial direction. The axial length of all bullet rods decreases sequentially from the outside to the inside.

[0031] The end of the incident rod 4 is equipped with n rings of shapers, each ring of shaper corresponding to the position of the first-stage bullet rod;

[0032] The bullet rod launching unit 2 launches a multi-stage bullet rod 3. The n-stage bullet rods of the multi-stage bullet rod 3 strike the shaper corresponding to the end of the incident rod 4 in sequence from the outer stage to the inner stage, thereby achieving multi-pulse loading.

[0033] n-1 screws are installed at the end of the outer barrel bullet rod. These n-1 screws are screwed into the end of the outer barrel bullet rod and press against the end of each bullet rod. Each screw is screwed in to a different depth to adjust the distance between each bullet rod and the beginning of the multi-stage bullet rod. Each screw is tightened with a nut to secure its axial position.

[0034] Each ring of shapers is arranged in a circular pattern with m shapers in the circumferential direction, where m = 1 to 12. From the outside to the inside, they are the 1st ring, the 2nd ring, ..., the nth ring. The nth ring has one shaper or an even number of shapers arranged symmetrically in the circumference. The 1st ring, the 2nd ring, ..., the (n-1th ring) all have an even number of shapers arranged symmetrically in the circumference.

[0035] The bullet rods of the multi-stage bullet rod 3 are defined as the 1st stage, the 2nd stage, …, the nth stage from the outside to the inside. The axial lengths of the n-stage bullet rods are L1, L2, …, Ln in sequence. The axial gap between the head end of the 2nd-stage bullet rod and the head end of the 1st-stage bullet rod is defined as d1. In this way, the axial gaps between the head ends of adjacent two stages are defined as d1, d2, d3, …, dn-1 in sequence. The cross-sectional areas of the n-stage bullet rods are A1, A2, …, An in sequence. The total area of each turn in the n-turn shaper is B1, B2, …, Bn in sequence. The waveform of the multi-pulse is adjusted by adjusting the axial gaps d1, d2, d3, …, dn-1 between the head ends of adjacent two stages, the cross-sectional areas A1, A2, …, An of the n-stage bullet rods, and the total area B1, B2, …, Bn of each turn in the n-turn shaper.

[0036] This embodiment is described by taking n = 3 as an example.

[0037] The multi-stage bullet rod 3 is a three-stage bullet. The structure of the three-stage bullet is as Figure 2 shown. The length of the innermost 3rd-stage bullet rod 3-3 is less than that of the middle 2nd-stage bullet rod 3-2, and the length of the 2nd-stage bullet rod 3-2 is less than that of the outermost 1st-stage bullet rod 3-1, that is, L3 < L2 < L1. However, the length difference between the three-stage bullets should not be too large, and it is preferably 5 - 10 mm. The outermost 1st-stage bullet rod 3-1 of the multi-stage sandwich bullet is a semi-open barrel-shaped bullet with a closed tail; at the positions corresponding to the 2nd-stage and 3rd-stage bullet rods at the bullet tail of the 1st-stage bullet rod 3-1, there are gap adjustment screws 3-4 and 3-5 respectively, which are used to adjust the gaps d1 and d2 between the impact surfaces of each stage of bullets to control the interval time between the loading pulses of each stage; the 2nd-stage bullet rod 3-2 is an equal-section circular cylindrical bullet; the 3rd-stage bullet rod 3-3 is a cylindrical bullet. To prevent the relative positions of each stage of bullets from sliding during the launch process of the launch tube, the adjustment screw 3-4 is fastened with a nut 3-6, and the adjustment screw 3-5 is fastened with a nut 3-7 to determine the axial positions of the two screws, and then the head end gap values of the 1st, 2nd, and 3rd-stage bullet rods are determined. The 3rd-stage bullet rod 3-3 can slide freely inside the 2nd-stage bullet rod 3-2, and the 2nd-stage bullet rod 3-2 can slide freely inside the 1st-stage bullet rod 3-1.

[0038] The cross-sectional areas of the three-stage bullet rods are A1, A2, A3 in sequence. The preferred scheme in this embodiment is: A1 = A2 = A3. The cross-sectional area of the incident rod 4 is A0.

[0039] Taking m=4 as an example, the shaping device is explained as follows: A third-stage shaping device 11 is set at the middle of the end of the incident rod 4. Its cross-sectional area is smaller than that of the third-stage bullet rod 3-3. The two are positioned opposite each other. After the third-stage bullet rod 3-3 is launched, it will impact the third-stage shaping device 11. In this embodiment, the third-stage shaping device 11 uses a single shaping device. A second-stage shaping device 10 is set at a position corresponding to the second-stage bullet rod 3-2. The second-stage shaping device 10 consists of four shaping devices 10-1 to 10-4 symmetrically arranged. After the second-stage bullet rod 3-2 is launched... The bullet will impact 10-1 to 10-4 in the second ring shaper 10. The dimensions of 10-1 to 10-4 in the second ring shaper 10 are smaller than the wall thickness of the second-stage bullet rod 3-2. Similarly, the first ring shaper 9 is set at the position corresponding to the first-stage bullet rod 3-1. The first ring shaper 9 is arranged in a circle and consists of 4 shapers 9-1 to 9-4 symmetrically arranged. After the first-stage bullet rod 3-1 is fired, it will impact 9-1 to 9-4 in the first ring shaper 9. The dimensions of 9-1 to 9-4 in the first ring shaper 9 are smaller than the wall thickness of the first-stage bullet rod 3-1.

[0040] The total area of ​​each ring in the n-ring shaping device is B1, B2, and B3 respectively. It is recommended to use copper, lead, or other materials for the shaping device.

[0041] The waveform of the multi-pulse is adjusted by regulating the axial gaps d1, d2, d3 between adjacent ends, the cross-sectional areas A1, A2, A3 of the three-stage bullet rods, and the total area B1, B2, B3 of each ring in the three-ring shaper. Specifically, the gaps between the bullet rods in the multi-stage bullet rod 3 are adjusted by screwing in the screws. The bullet rod launching unit 2 fires bullets, and the three-stage bullet rods have the same initial impact velocity V0 before impact. The three-stage bullet rods sequentially impact the shaper at the end of the incident rod 4, forming three sequential loading pulses in the incident rod 4 to load the sample 8. Strain gauges attached to the incident rod 4 and the transmission rod 5 are connected to a strain gauge and an oscilloscope to measure and store the signals. Subsequently, the signals are processed according to the Hopkinson bar data processing method to obtain the cyclic loading and unloading mechanical properties of the test sample 8 under high strain rate.

[0042] See Figure 4Initially, the gap between the first and second stage bullet rods is d1, and the gap between the second and third stage bullet rods is d2. After the first stage bullet rod impacts the incident rod 4, the first incident loading pulse is formed in the incident rod 4. Simultaneously, during the impact of the first stage bullet on the incident rod 4, the first stage bullet and the incident rod 4 move in the impact direction together until the first stage bullet completes the impact. After the first stage bullet completes the impact, because the generalized wave impedance of the first stage bullet is less than the generalized wave impedance of the incident rod 4, the first stage bullet will gain a velocity opposite to the impact direction and move in the opposite direction, while the end face of the incident rod 4 stops moving. At this time, during the impact of the first stage bullet, the end face of the incident rod 4 has moved forward by a distance Δd1 compared to when the first stage bullet just impacted the incident rod 4. The second and third stage bullets are not disturbed by the first stage bullet before they impact the incident rod 4 and continue to move forward with an initial velocity V0. The second-stage bullet will obviously travel a distance of (d1 + Δd1) before striking the incident rod 4, generating a second loading pulse. The time interval between the first and second impacts is easily calculated as t1 = (d1 + Δd1) / V0. At the very moment the second-stage bullet first strikes the incident rod 4, the distance between the third-stage bullet and the incident rod 4 is d2. Similarly, during the impact of the second-stage bullet, the incident rod 4 will move forward again along with the second-stage bullet. After the second-stage bullet's impact, the incident rod 4 will move forward another distance of Δd2. Clearly, after the second-stage bullet strikes the incident rod 4, the third-stage bullet will travel forward at a speed of V0 for a distance of (d2 + Δd2) before striking the incident rod 4, forming a third loading pulse. The time interval between the second and third loading pulses is easily calculated as t2 = (d2 + Δd2) / V0.

[0043] The three-stage bullet rod impacts the shaper with a time difference; the pulse width is adjusted by regulating the gaps at each stage. The adjustment of the pulse amplitude is related to various factors. Several waveform adjustment examples are given below; those skilled in the art can make corresponding adjustments according to their needs.

[0044] When the required loading waveform for the measured material is a rectangular wave, a shaper is not needed. The cross-sectional areas of the first, second, and third stage bullet rods are A1, A2, and A3, respectively, and the cross-sectional area of ​​the incident rod 4 is A0. Adjust the adjusting screws so that the gap between the impact surfaces of the first and second stage bullet rods is d1, and the gap between the second and third stage bullets is d2. When the multi-stage bullet rod 3 is fired, the first, second, and third stage bullet rods will strike the incident rod 4 sequentially at the same velocity V0. A strong discontinuous elastic wave propagating to the right is formed at the impact end of the incident rod 4, while a leftward elastic wave is formed within the bullet. After the impact, let the loading pulse amplitudes formed by the three stages of the bullet in the incident rod 4 be σ1, σ2, and σ3, respectively. Figure 5The lengths of the first-stage bullet rods are L1 = 400 mm, L2 = 380 mm, and L3 = 375 mm. The cross-sectional areas of all three bullet rods are equal, at 418 mm². 2 When the impact velocity V0 = 10 m / s and the bullet gap is set to d1 = d2 = 1.5 mm, the three loading pulses generated in the incident rod show that the amplitudes of the three loading pulses are equal.

[0045] When using a shaper, a pre-impact test without a specimen is required before the formal experiment. The method is as follows: Adjust the adjusting screws so that the gap between the impact surfaces of the first and second stage bullets is d1, and the gap between the second and third stage bullets is d2. The shaper is positioned at the end of the incident rod 4, as shown in the diagram. Figure 3 As shown, bullets are fired at a certain speed. Figure 6 The lengths of the first-stage bullet rods are L1 = 400 mm, the second-stage bullet rods are L2 = 380 mm, and the third-stage bullet rods are L3 = 375 mm. The cross-sectional areas of the three bullet rods are equal: A1 = A2 = A3 = 418 mm². 2 Impact velocity V0 = 10 m / s, bullet gap set as d1 = d2 = 2 mm, brass shapers used, total area of ​​each shaper equal B1 = B2 = B3 = 52 mm² 2 At that time, the three loading pulses generated in the incident rod 4 are the same as those in the third-stage bullet material, and the amplitudes of the three pulses decrease sequentially.

[0046] When it is necessary to generate progressively stronger loading pulses, the implementation method is as follows: Adjust the adjusting screw so that the gap between the impact surfaces of the first and second stage bullet rods is d1, and the gap between the second and third stage bullets is d2. Arrange a shaper at the end of the incident rod 4, as shown in the diagram. Figure 3 As shown, bullets are fired at a certain speed, and loading signals are recorded. Based on the loading signals, gaps d1 and d2, the size and number of shapers corresponding to each bullet stage, and the bullet firing speed are adjusted to a suitable position. Then, sample 8 is placed between incident rod 4 and transmission rod 5 for loading test. Figure 7 The lengths of the first-stage bullet rods are L1 = 400 mm, the second-stage bullet rods are L2 = 380 mm, and the third-stage bullet rods are L3 = 375 mm. The cross-sectional areas of the three bullet rods are equal: A1 = A2 = A3 = 418 mm². 2 Impact velocity V0 = 10 m / s, bullet gap set as d1 = d2 = 2 mm, brass shaper used, total area of ​​first-stage shaper B1 = 52 mm² 2 The total area of ​​the second-stage shaper, B2, is 81 mm². 2 The total area of ​​the third-level shaping device, B3, is 210 mm². 2The first-stage bullet rod is made of aluminum alloy, while the second and third-stage bullet rods are made of the same high-strength stainless steel as the incident rod 4. The amplitude of the three loading pulses generated in the incident rod 4 increases sequentially.

[0047] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A Hopkinson bar testing apparatus for controllable continuous multi-pulse loading, characterized in that, It includes a bullet rod launching unit (2), a multi-stage bullet rod (3) and an incident rod (4). The bullet rod launching unit (2) launches the multi-stage bullet rod (3) and hits the incident rod (4). The multi-stage bullet rod (3) is an n-stage sleeve structure, n>2. The multi-stage bullet rod (3) includes an outer barrel bullet rod, a central cylindrical bullet rod, and n-2 intermediate cylindrical bullet rods. The outer barrel bullet rod is a barrel-shaped structure with closed ends and open ends. The n-2 intermediate cylindrical bullet rods are sleeved inside the outer barrel bullet rod and outside the central cylindrical bullet rod. The n-stage bullet rods can slide relative to each other along the axial direction. The axial length of all bullet rods decreases from the outside to the inside. The end of the incident rod (4) is equipped with n rings of shapers, each ring of shapers corresponding to the position of the first-stage bullet rod; each ring of shapers is arranged in a circular manner with m shapers arranged in the circumferential direction, m=1~12, from the outside to the inside as the 1st ring, the 2nd ring, ..., the nth ring, where the nth ring is equipped with 1 shaper or an even number of shapers arranged symmetrically in the circumferential direction, and the 1st ring, the 2nd ring, ..., the n-1th ring are all arranged with an even number of shapers arranged symmetrically in the circumferential direction; The bullet launcher unit (2) launches a multi-stage bullet rod (3). The n-stage bullet rods of the multi-stage bullet rod (3) strike the shaper corresponding to the end of the incident rod (4) in sequence from the outer stage to the inner stage, realizing multi-pulse loading. The bullet rods of the multi-stage bullet rod (3) are defined as stage 1, stage 2, ..., stage n from the outside to the inside. The axial lengths of the n-stage bullet rods are L1, L2, ..., Ln in sequence. The axial gap between the head end of the stage 2 bullet rod and the head end of the stage 1 bullet rod is defined as d1. The axial gaps between adjacent ends are d1, d2, d3, ..., dn-1, respectively; the cross-sectional areas of the n-stage bullet rod are A1, A2, ..., An, respectively; and the total area of ​​each ring in the n-ring shaper is B1, B2, ..., Bn, respectively. The waveform of the multi-pulse is adjusted by regulating the axial gaps d1, d2, d3, ..., dn-1 between adjacent ends, the cross-sectional areas A1, A2, ..., An of the n-stage bullet rod, and the total area B1, B2, ..., Bn of each ring in the n-ring shaper.

2. The Hopkinson bar testing apparatus for controllable continuous multi-pulse loading according to claim 1, characterized in that, n-1 screws are set at the end of the outer barrel bullet rod. The n-1 screws are screwed into the end of the outer barrel bullet rod and press against the end of each bullet rod. Each screw is screwed into a different depth to adjust the distance between each bullet rod and the head of the multi-stage bullet rod (3).

3. The Hopkinson bar testing apparatus for controllable continuous multi-pulse loading according to claim 2, characterized in that, Each screw is secured in its axial position with a nut.

4. The Hopkinson bar testing apparatus for controllable continuous multi-pulse loading according to claim 1, characterized in that, The shaping instrument is made of brass or lead.

5. The Hopkinson bar testing apparatus for controllable continuous multi-pulse loading according to claim 1, characterized in that, The size of the shaping device is smaller than the wall thickness of the corresponding grade bullet rod.

6. The Hopkinson bar testing apparatus for controllable continuous multi-pulse loading according to claim 1, characterized in that, The axial clearances d1, d2, d3, ... dn-1 between adjacent stage ends are selected as 5 mm to 10 mm.

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