Dynamic compression bar impact fatigue testing device

Abstract

The invention relates to the technical field of dynamic impact fatigue test equipment, in particular to a dynamic compression bar impact fatigue test device. A dynamic compression bar impact fatigue testing device can comprise a workbench, a first launching assembly, a compression bar assembly and a first momentum trap. The first launching assembly comprises a first driving unit, a first gun barrel and a first impact rod. The pressing rod assembly comprises a first pressing rod and a second pressing rod, and the first pressing rod is slidably connected with the workbench. The second pressing rod is in sliding connection with the workbench. A clamping space is formed between the first pressing rod and the second pressing rod. The first momentum trap includes a first collision unit and a first mass block. The first collision unit is detachably connected with the first pressing rod. The first mass block is detachably connected with the workbench. The first mass block is located on the side, away from the first transmitting assembly, of the first collision unit. A first gap is formed between the first mass block and the first collision unit. Therefore, the problem that the impact fatigue testing device cannot ensure single loading of the sample is solved.

Description

Technical Field

[0001] The invention relates to the technical field of dynamic impact fatigue testing equipment, in particular to a dynamic pressure rod impact fatigue testing device. Background Art

[0002] Impact fatigue refers to the process in which a material, after being subjected to repeated impact loads, eventually undergoes fatigue fracture due to the gradual change of the internal microstructure of the material and the accumulation of damage. This type of fatigue fracture is different from the fracture caused by a single high-energy impact. It focuses more on the impact of multiple small-energy impacts on the long-term performance of the material. Impact fatigue is of great significance in many engineering fields, especially in industries with extremely high requirements for material performance, such as aerospace, automobile manufacturing, and machinery manufacturing. In these industries, many key components (such as the blades of aircraft engines, the suspension system of automobiles, and the valve stems of internal combustion engines) may be affected by impact fatigue during long-term use. Taking the Hopkinson bar as an example, the material can be tested to provide important reference data for the design and optimization of engineering structures. The Hopkinson bar can apply high strain rate stress in a very short time, thereby meeting the requirements for studying the mechanical properties of materials under impact loads. The Hopkinson bar has the advantages of accurate and reliable data and a wide range of applications. The propagation of stress waves in the bar can be used to apply and measure the dynamic stress and strain of the sample. The Hopkinson bar usually includes an incident bar, a transmission bar, an impact device, and a data acquisition system. The impact bar or bullet is made to hit the incident bar through a pneumatic, hydraulic, or electromagnetic accelerator, thereby generating a stress wave in the incident bar. The stress wave propagates along the incident bar. When the stress wave reaches the contact surface between the incident bar and the sample, part of the stress wave is reflected, and the other part is transmitted through the sample to the transmission bar. The strain gauges installed on the incident bar and the transmission bar record the strain signal of the stress wave. By analyzing these signals, the stress, strain, and strain rate of the sample under high strain rate conditions can be calculated.

[0003] When conducting dynamic impact fatigue tests on materials, the current impact fatigue test equipment has the following main problems: the specimen cannot be loaded once during the loading process. That is, each time dynamic loading is performed, the stress wave generated will be reflected multiple times on the rod, forming alternating compression waves and tensile waves. Since the specimen is not separated from the rod, the specimen will be loaded with compression waves multiple times, and the size and number of multiple loadings cannot be controlled. As a result, the loading conditions of the specimen in each impact fatigue test are inconsistent with the description of the stress and strain curve, and multiple loadings will also conceal the true fatigue failure morphology of the specimen, which is not conducive to establishing an accurate relationship between dynamic impact load, number of dynamic impacts and fatigue failure mode. Summary of the invention

[0004] In order to solve the problem that the impact fatigue testing device cannot ensure single loading of the sample, the present invention provides a dynamic pressure rod impact fatigue testing device, comprising:

[0005] Workbench;

[0006] A first launching assembly, the first launching assembly comprising a first driving unit, a first barrel and a first impact rod; the first driving unit and the first barrel are detachably connected to the workbench respectively; the first impact rod is slidably connected to the first barrel;

[0007] A pressure rod assembly, the pressure rod assembly includes a first pressure rod and a second pressure rod, the first pressure rod is slidably connected to the workbench; the sliding direction of the first pressure rod is parallel to its own length direction; the first pressure rod and the first impact rod are coaxially arranged; the second pressure rod is slidably connected to the workbench; the sliding direction of the second pressure rod is parallel to its own length direction; there is a clamping space between the first pressure rod and the second pressure rod; the first pressure rod is located between the first barrel and the second pressure rod; the first pressure rod and the second pressure rod are coaxially arranged;

[0008] A first momentum trap, wherein the first momentum trap comprises a first collision unit and a first mass block; the first collision unit is detachably connected to the first pressure rod; the first mass block is detachably connected to the workbench; the first mass block is located on a side of the first collision unit away from the first launching assembly; a first gap is provided between the first mass block and the first collision unit; the first gap is calculated using the following formula:

[0009]

[0010] Wherein, d1 is the first gap; ε i1 In order to cancel the first momentum trap, when the first impact rod hits the first compression rod at a preset speed, the strain of the first compression rod is measured; c 01 is the wave velocity of the stress wave in the first compression rod; T 01 is the loading pulse width of the stress wave in the first compression rod.

[0011] In some embodiments, the second launching assembly comprises a second driving unit, a second barrel and a second impact rod; the second driving unit and the second barrel are detachably connected to the workbench respectively; the second impact rod is slidably connected to the second barrel; the second impact rod is coaxially arranged with the second pressure rod;

[0012] The second momentum trap comprises a second collision unit and a second mass block; the second collision unit is detachably connected to the second pressure rod; the second mass block is detachably connected to the workbench; the second mass block is located at a side of the second collision unit away from the second launching assembly; a second gap is provided between the second mass block and the second collision unit; the second gap is calculated using the following formula:

[0013]

[0014] where d 2 is the second gap; ε i2 In order to cancel the second momentum trap, when the second impact rod hits the second pressure rod at a preset speed, the strain of the second pressure rod is measured; c 02 is the wave velocity of the stress wave in the second compression rod; T 02 is the loading pulse width of the stress wave in the second compression rod.

[0015] In some embodiments, the first limiting assembly comprises a first limiting rod and a first guide portion; the first limiting rod is located between the first impact rod and the first pressure rod; the first guide portion is detachably connected to the workbench; the first limiting rod is slidably connected to the first guide portion; the sliding direction of the first limiting rod is parallel to its own length direction; the first guide portion limits the sliding distance of the first limiting rod; the first limiting rod is coaxially arranged with the first impact rod;

[0016] The second limiting assembly includes a second limiting rod and a second guide portion; the second limiting rod is located between the second impact rod and the second pressure rod; the second guide portion is detachably connected to the workbench; the second limiting rod is slidably connected to the second guide portion; the sliding direction of the second limiting rod is parallel to its own length direction; the second guide portion limits the sliding distance of the second limiting rod; the second limiting rod is coaxially arranged with the second impact rod.

[0017] In some embodiments, the first firing assembly further includes a first reset unit, the first reset unit including a first air pump and a first pressure-sensitive sensor; the first air pump is connected to the first barrel; the air suction port of the first air pump is located between the first drive unit and the first impact rod; the first pressure-sensitive sensor is detachably connected to the first barrel; the first pressure-sensitive sensor is located at the end of the first barrel facing the first drive unit;

[0018] The second firing assembly also includes a second reset unit, which includes a second vacuum pump and a second pressure-sensitive sensor; the second vacuum pump is connected to the second barrel; the vacuum port of the second vacuum pump is located between the second drive unit and the second impact rod; the second pressure-sensitive sensor is detachably connected to the second barrel; the second pressure-sensitive sensor is located at the end of the second barrel facing the second drive unit.

[0019] In some embodiments, the pressure rod assembly also includes a rod position control unit; the rod position control unit includes a magnetic part and a sliding part; the sliding part is detachably connected to the workbench; the magnetic part is detachably connected to the sliding part; the sliding part drives the magnetic part to move; the moving direction of the magnetic part is parallel to the moving direction of the first impact rod.

[0020] In some embodiments, the first momentum trap further comprises a first magnetic adsorption portion; the first magnetic adsorption portion is detachably connected to the first mass block; when the magnetic adsorption portion and the first magnetic adsorption portion are close to each other, there is an adsorption force between the two;

[0021] The second momentum trap further includes a second magnetic adsorption portion; the second magnetic adsorption portion is detachably connected to the second mass block; and when the magnetic adsorption portion and the second magnetic adsorption portion are close to each other, there is an adsorption force between the two.

[0022] In some embodiments, the pressure rod assembly also includes an auxiliary sleeve; the auxiliary sleeve has a first clamping cavity, an avoidance cavity and a second clamping cavity; one end of the first pressure rod is inserted into the first clamping cavity; one end of the second pressure rod is inserted into the second clamping cavity; when the sample is subjected to a loading test; the sample is located in the avoidance cavity; the inner wall of the avoidance cavity has a gap with the sample; the inner wall of the first clamping cavity can shrink and expand; the inner wall of the second clamping cavity can shrink and expand.

[0023] In some embodiments, the auxiliary sleeve includes a rigid outer sleeve, a rigid inner sleeve, a first elastic sleeve and a second elastic sleeve; the rigid inner sleeve is coaxially arranged inside the rigid outer sleeve; one end of the first elastic sleeve is fixedly connected to the rigid outer sleeve, and the other end of the first elastic sleeve is fixedly connected to the rigid inner sleeve; one end of the second elastic sleeve is fixedly connected to the rigid outer sleeve, and the other end of the second elastic sleeve is fixedly connected to the rigid inner sleeve; the rigid outer sleeve, the rigid inner sleeve, the first elastic sleeve and the second elastic sleeve cooperate to form an annular cylindrical inflation cavity; the internal cavity of the first elastic sleeve is the first clamping cavity; the internal cavity of the second elastic sleeve is the second clamping cavity.

[0024] In some embodiments, the auxiliary sleeve also includes a first force sensor and a second force sensor; the first force sensor is located in the first clamping cavity; the first force sensor is detachably connected to the inner wall of the first clamping cavity; the second force sensor is located in the second clamping cavity; the second force sensor is detachably connected to the inner wall of the second clamping cavity.

[0025] In some embodiments, the dynamic compression rod impact fatigue testing device includes a data acquisition component; the data acquisition component includes a first strain gauge, a second strain gauge, a first bridge box, a second bridge box, a strain amplifier and an oscilloscope, the first strain gauge is detachably connected to the first compression rod; the second strain gauge is detachably connected to the second compression rod; the first strain gauge and the second strain gauge are symmetrically arranged about the midpoint between the first compression rod and the second compression rod; the first bridge box is electrically connected to the first strain gauge and the strain amplifier, respectively; the second bridge box is electrically connected to the second strain gauge and the strain amplifier, respectively; the oscilloscope is electrically connected to the strain amplifier.

[0026] In order to solve the problem that the impact fatigue test device cannot ensure single loading of the specimen, the present invention has the following advantages:

[0027] The formula for adjusting the gap of the first momentum trap of the present invention is adjusted according to the difference in the material properties of the wave impedance of the first momentum trap and the first pressure rod, so the reflected tensile wave will be partially absorbed by the first momentum trap, while the other part will be reflected in the first momentum trap, and the effect of the first momentum trap on the wave is mainly to change the propagation direction of the wave, rather than to change the nature of the wave, so the reflected wave is still a tensile wave. That is, due to the combined effect of the obstruction of the first collision unit and the first mass block, the requirements of the boundary conditions, and the conservation of energy and momentum, in the reflection process of the tensile wave, part or all of the energy and momentum of the tensile wave can be reflected back, thereby forming a reflected wave with the same properties as the tensile wave. In this way, the specimen in the impact fatigue test can be subjected to a single loading of the compression wave, which is conducive to establishing an accurate relationship between the dynamic impact load, the number of dynamic impacts, and the fatigue failure mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic structural diagram of a dynamic compression rod impact fatigue testing device according to an embodiment is shown;

[0029] Figure 2 A schematic structural diagram of a dynamic compression rod impact fatigue testing device according to another embodiment is shown;

[0030] Figure 3 A schematic structural diagram of a dynamic compression rod impact fatigue testing device according to another embodiment is shown;

[0031] Figure 4 A schematic diagram showing the structure of a first limit assembly and a second limit assembly according to an embodiment is shown;

[0032] Figure 5 A schematic structural diagram of a rod position control unit according to an embodiment is shown;

[0033] Figure 6 A top view of an auxiliary sleeve of one embodiment is shown;

[0034] Figure 7 Shows Figure 6 A cross-sectional view of the auxiliary sleeve along AA;

[0035] Figure 8 A structural schematic diagram of a data acquisition component of an embodiment is shown.

[0036] Figure numerals: workbench 10; first launching assembly 20; first driving unit 21; first barrel 22; first impact rod 23; first reset unit 24; first air pump 241; first pressure-sensitive sensor 242; pressure rod assembly 30; first pressure rod 31; second pressure rod 32; rod position control unit 33; magnetic attraction part 331; sliding part 332; first momentum trap 40; first collision unit 41; first mass block 42; second launching assembly 50; second driving unit 51; second barrel 52; second impact rod 53; second reset unit 54; second air pump 541; second pressure-sensitive sensor 54 2; second momentum trap 60; second collision unit 61; second mass block 62; first limit assembly 70; first limit rod 71; first guide portion 72; second limit assembly 80; second limit rod 81; second guide portion 82; data acquisition assembly 90; first strain gauge 91; second strain gauge 92; first bridge box 93; second bridge box 94; strain amplifier 95; oscilloscope 96; auxiliary sleeve 100; first clamping cavity 110; second clamping cavity 120; avoidance cavity 130; rigid outer cylinder 140; rigid inner cylinder 150; first elastic sleeve 160; second elastic sleeve 170; specimen 180. DETAILED DESCRIPTION

[0037] The present disclosure will now be discussed with reference to several exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and thus implement the present disclosure, rather than implying any limitation on the scope of the present disclosure.

[0038] As used herein, the term "including" and its variants are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "based at least in part on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment". The term "another embodiment" is to be interpreted as "at least one other embodiment". The orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like is based on the orientation or position relationship shown in the accompanying drawings. These terms are mainly for better describing the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation. In addition, in addition to being used to indicate an orientation or position relationship, some of the above terms may also be used to indicate other meanings, such as the term "upper" may also be used to indicate a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to the specific circumstances. In addition, the terms "install", "set", "provided with", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be an internal connection between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0039] Impact fatigue testing is to provide important reference data for the design and optimization of engineering structures. At present, the Hopkinson bar is usually used to perform impact fatigue testing on the specimen. Although the Hopkinson bar can perform repeated dynamic loading tests on compression specimens, when the bullet hits the incident bar, the stress wave in the incident bar will undergo alternating changes in tensile waves and compression waves during the propagation process. Since the specimen and the bar are not separated, the stress wave formed will be reflected multiple times after hitting the specimen, forming alternating tensile waves and compression waves, so that the specimen will be loaded with compression waves multiple times, and the size and number of multiple loadings cannot be controlled. That is, it is impossible to ensure a single loading of the compression wave of the specimen. Therefore, the loading condition of the specimen in each impact fatigue test is inconsistent with the description of the stress and strain curve. And multiple loading will conceal the true fatigue failure morphology of the specimen, which is not conducive to establishing an accurate relationship between dynamic impact load, number of dynamic impacts and fatigue failure mode. In order to achieve single impact loading, the setting of the incident bar can be cancelled, and the bullet can be used to directly hit the specimen, but this will cause problems such as difficulty in verifying stress balance and inaccurate reset of the rod. Therefore, in order to solve the above problems, the present invention provides a dynamic pressure rod impact fatigue testing device, such as Figure 1 As shown, a dynamic compression rod impact fatigue testing device may include a workbench 10 , a first launching assembly 20 , a compression rod assembly 30 and a first momentum trap 40 .

[0040] In this embodiment, if Figure 1 As shown, the workbench 10 can be made of metal material, so as to ensure the stability of the first launching assembly 20 , the pressure rod assembly 30 and the first momentum trap 40 .

[0041] like Figure 1 As shown, the first launching assembly 20 may include a first driving unit 21, a first barrel 22 and a first impact rod 23. The first driving unit 21 and the first barrel 22 are detachably connected to the workbench 10 respectively. The first impact rod 23 may be a cylinder made of steel or aluminum, or may be a spindle or multi-step shape. The cross-sectional diameter of the first impact rod 23 may be the same as the inner diameter of the first barrel 22. The first impact rod 23 may be slidably connected to the first barrel 22. The first driving unit 21 may drive the first impact rod 23 to be ejected along the direction of the axis of the first barrel 22, thereby performing an impact loading test on the sample 180 and obtaining accurate experimental results.

[0042] like Figure 1As shown, the pressure rod assembly 30 may include a first pressure rod 31 and a second pressure rod 32. The first pressure rod 31 serves as an incident rod, and the second pressure rod 32 serves as a transmission rod. The first pressure rod 31 may be slidably connected to the workbench 10. The sliding direction of the first pressure rod 31 may be parallel to its own length direction, such as the horizontal direction. The first pressure rod 31 may be coaxially arranged with the first impact rod 23. The second pressure rod 32 may be slidably connected to the workbench 10. The sliding direction of the second pressure rod 32 may be parallel to its own length direction, such as the horizontal direction. A clamping space may be provided between the first pressure rod 31 and the second pressure rod 32. The sample 180 may be placed in the clamping space. The first pressure rod 31 may be located between the first barrel 22 and the second pressure rod 32. The first pressure rod 31 may be coaxially arranged with the second pressure rod 32. The first driving unit 21 may drive the first impact rod 23 to collide with the first pressure rod 31 to form a stress wave, and the stress wave is transmitted to the sample 180 along the first pressure rod 31, and a single impact loading test of a compression wave is performed on the sample 180. That is, when the first impact rod 23 hits the contact surface between the first pressure rod 31 and the sample 180, a part of the stress wave will be reflected, and the reflected stress wave will form an alternating change of tensile wave and compression wave, and the reflected tensile wave will be absorbed by the first momentum trap, thereby obtaining a single impact loading test of the compression wave on the sample 180. Another part of the stress wave will be transmitted to the second pressure rod 32 through the sample 180 for propagation. The first pressure rod 31 and the second pressure rod 32 can clamp and fix the sample 180, so that the generated stress can be buffered and the stress can be made more balanced, thereby weakening the loading force. Therefore, it is not easy to cause sudden changes when adjusting the loading force, so it is easy to control the size of the impact force applied by the first launch component 20 each time to be consistent with the actual situation. In this way, the cost of the impact fatigue test equipment can be reduced and the experimental efficiency can be improved.

[0043] like Figure 1 As shown, the first momentum trap 40 may include a first collision unit 41 and a first mass block 42. The first collision unit 41 may be detachably connected to the first pressure rod 31. The first mass block 42 may be detachably connected to the workbench 10. The first mass block 42 may be located on a side of the first collision unit 41 away from the first launch assembly 20. A first gap is provided between the first mass block 42 and the first collision unit 41. The first gap is calculated using the following formula:

[0044]

[0045] Where d1 is the first gap. i1 In order to cancel the first momentum trap 40, when the first impact rod 23 hits the first compression rod 31 at a preset speed, the strain of the first compression rod 31 is measured. 01 T is the wave velocity of the stress wave in the first compression rod 31. 01is the loading pulse width of the stress wave in the first pressure rod 31. The formula for adjusting the gap of the first momentum trap 40 is adjusted according to the difference in the material properties of the wave impedance of the first momentum trap 40 and the first pressure rod 31. Therefore, the tensile wave reflected from the contact surface of the first pressure rod 31 and the sample 180 will be absorbed by the first momentum trap 40, while the other part will be reflected in the first momentum trap 40. Since the effect of the first momentum trap 40 on the stress wave is to change the propagation direction rather than the nature of the wave, the reflected wave is still a tensile wave. That is, the propagation speed of the tensile wave in the medium depends on factors such as the elastic properties and density of the medium. Therefore, the measured wave speed can reflect the properties of the material, and then the gap of the momentum trap is adjusted accordingly, so that the reflected stress wave is a tensile wave. In this way, it can be ensured that the displacement of the first momentum trap 40 is zero and the stress is continuous, and the compression wave in the first pressure rod 31 is loaded on the sample 180 once, which is conducive to establishing an accurate relationship between the dynamic impact load, the number of dynamic impacts and the fatigue failure mode.

[0046] In this embodiment, if Figure 2 As shown, a dynamic compression rod impact fatigue testing device may include a second launching assembly 50 and a second momentum trap 60 .

[0047] like Figure 2 As shown, the second launching assembly 50 may include a second driving unit 51, a second barrel 52, and a second impact rod 53. The second driving unit 51 and the second barrel 52 may be detachably connected to the workbench 10, respectively. The second impact rod 53 may be slidably connected to the second barrel 52. The second impact rod 53 may be coaxially arranged with the second pressure rod 32. The second driving unit 51 may drive the second impact rod 53 to be ejected along the axial direction of the second barrel 52, and hit the second pressure rod 32 to form a stress wave, thereby testing the sample 180 and obtaining accurate experimental results.

[0048] like Figure 2 As shown, the second momentum trap 60 may include a second collision unit 61 and a second mass block 62. The second collision unit 61 may be detachably connected to the second pressure rod 32. The second mass block 62 may be detachably connected to the workbench 10. The second mass block 62 is located on a side of the second collision unit 61 away from the second launch assembly 50. A second gap is provided between the second mass block 62 and the second collision unit 61. The second gap is calculated using the following formula:

[0049]

[0050] Among them, d 2 is the second gap. i2 In order to cancel the second momentum trap 60, the strain of the second compression rod 32 is measured when the second impact rod 53 hits the second compression rod 32 at a preset speed.02 T is the wave velocity of the stress wave in the second compression rod 32. 02 is the loading pulse width of the stress wave in the second pressure rod 32. A part of the tensile wave reflected from the inside of the second pressure rod 32 will be absorbed by the second momentum trap 60, while the other part will be reflected in the second momentum trap 60. Since the second momentum trap 60 mainly changes the propagation direction of the wave rather than changing the nature of the wave, the reflected wave is still a tensile wave. Thus, a single impact loading test of the compression wave can be performed on the sample 180. When the first pressure rod 31 is used as the incident rod and the second pressure rod 32 is used as the transmission rod, after the sample 180 is subjected to an impact fatigue test in one direction, the second pressure rod 32 can be used as the incident rod and the first pressure rod 31 can be used as the transmission rod to perform a reverse impact loading test on the sample 180, so that a two-way alternating impact fatigue test can be performed. The parameters of multiple anti-impact loading fatigue of the sample 180 are obtained so as to ensure that the compression wave of the impact fatigue test is a single load, and at the same time, the experimental efficiency of the dynamic impact fatigue test on the sample 180 can be improved.

[0051] In this embodiment, if Figure 4 As shown, a dynamic compression rod impact fatigue testing device may include a first limiting assembly 70 and a second limiting assembly 80 .

[0052] like Figure 4 As shown, the first limiting assembly 70 may include a first limiting rod 71 and a first guide portion 72. The first limiting rod 71 may be located between the first impact rod 23 and the first pressure rod 31. The first guide portion 72 may be detachably connected to the workbench 10. The first limiting rod 71 may be slidably connected to the first guide portion 72. The sliding direction of the first limiting rod 71 may be parallel to its own length direction, such as the horizontal direction. The first guide portion 72 may limit the sliding distance of the first limiting rod 71. The first limiting rod 71 may be coaxially arranged with the first impact rod 23. The first limiting rod 71 may have a slight displacement space, and the first limiting rod 71 is slidably connected to the workbench 10, which can prevent the workbench 10 from affecting the conduction of the stress wave. The first limiting rod 71 is a variable cross-section cylinder, and increasing the contact section between the first limiting rod 71 and the first guide portion 72 can prevent the first pressure rod 31 from moving too much, thereby avoiding affecting the test results.

[0053] like Figure 4As shown, the second limiting assembly 80 may include a second limiting rod 81 and a second guide portion 82. The second limiting rod 81 may be located between the second impact rod 53 and the second pressure rod 32. The second guide portion 82 may be detachably connected to the workbench 10. The second limiting rod 81 may be slidably connected to the second guide portion 82. The sliding direction of the second limiting rod 81 may be parallel to its own length direction, such as the horizontal direction. The second guide portion 82 may limit the sliding distance of the second limiting rod 81. The second limiting rod 81 may be coaxially arranged with the second impact rod 53. The second limiting rod 81 may have a slight displacement space, and the second limiting rod 81 is slidably connected to the workbench 10, which can avoid the workbench 10 from affecting the conduction of the stress wave. And the second limiting rod 81 is a variable cross-section cylinder. Increasing the contact section between the second limiting rod 81 and the second guide portion 82 can prevent the second pressure rod 32 from moving too much, thereby avoiding affecting the test results.

[0054] In this embodiment, if Figure 3 As shown, the first firing assembly 20 may further include a first reset unit 24, and the first reset unit 24 may include a first air pump 241 and a first pressure-sensitive sensor 242. The first air pump 241 may be connected to the first barrel 22. The air suction port of the first air pump 241 may be located between the first drive unit 21 and the first impact rod 23. The first pressure-sensitive sensor 242 may be detachably connected to the first barrel 22. The first pressure-sensitive sensor 242 may be located at the end of the barrel facing the first drive unit 21. The first air pump 241 may extract the gas from the first barrel 22, so that after the impact fatigue test, the first impact rod 23 may be returned to the side of the first barrel 22 close to the first drive unit 21, that is, the first impact rod 23 is reset.

[0055] like Figure 2 , Figure 3 As shown, the second firing assembly 50 may further include a second reset unit 54, and the second reset unit 54 may include a second air pump 541 and a second pressure-sensitive sensor 542. The second air pump 541 may be connected to the second barrel 52. The air extraction port of the second air pump 541 may be located between the second drive unit 51 and the second impact rod 53. The second pressure-sensitive sensor 542 may be detachably connected to the second barrel 52. The second pressure-sensitive sensor 542 may be located at the end of the barrel facing the second drive unit 51. The second air pump 541 may extract the gas from the second barrel 52, so that after the impact fatigue test, the second impact rod 53 may be returned to the side of the second barrel 52 close to the second drive unit 51, that is, the reset of the second impact rod 53 is achieved.

[0056] The control time for the first air pump 241 to pump air until the first impact rod 23 is reset or the second air pump 541 to pump air until the second impact rod 53 is reset is:

[0057]

[0058] Among them, V G V is the gas volume in the space where the first impact rod 23 is close to the first driving unit 21 or the second impact rod 53 is close to the second driving unit 51; R is the pumping rate of the first pump 241 or the second pump 541; P a P is the air pressure in the first barrel 22 or the second barrel 52 before the air is evacuated, which is usually the atmospheric pressure 1013 Mbar; e The air pressure required to reset the first impact rod 23 or the second impact rod 53 in the first barrel 22 or the second barrel 52 is generally set to 400Mbar; k is a correction factor, which is usually set to 1.3. In this way, the air pumping time of the first air pump 241 and the second air pump 541 can be set more accurately, thereby controlling the reset of the first impact rod 23 or the second impact rod 53, and effectively avoiding the waste of energy by long-term air pumping.

[0059] In this embodiment, if Figure 3 , Figure 5 As shown, the pressure rod assembly 30 may also include a rod position control unit 33, and two rod position control units 33 may be provided. The rod position control unit 33 may include a magnetic attraction portion 331 and a sliding portion 332. The sliding portion 332 may be detachably connected to the workbench 10. The magnetic attraction portion 331 may be detachably connected to the sliding portion 332. The sliding portion 332 may drive the magnetic attraction portion 331 to move. The moving direction of the magnetic attraction portion 331 may be parallel to the moving direction of the first impact rod 23. The end of the magnetic attraction portion 331 away from the sliding portion 332 is an electromagnetic semicircular structure, and the diameter of the magnetic attraction portion 331 is the same as the cross-sectional diameter of the first pressure rod 31 and the second pressure rod 32. The semicircular structure may generate a strong magnet, and the first pressure rod 31 or the second pressure rod 32 may be adsorbed and slid along the sliding portion 332 through the magnetic attraction portion 331, so as to adjust the first pressure rod 31 to contact the end surface of the first limit rod 71. Or adjust the second pressing rod 32 to contact the end surface of the second limiting rod 81. This facilitates the control of the first pressing rod 31 and the second pressing rod 32 to reset, so as to facilitate the propagation of stress waves during the next dynamic impact loading.

[0060] In this embodiment, if Figure 3 As shown, the first momentum trap 40 may further include a first magnetic adsorption portion. The first magnetic adsorption portion may be detachably connected to the first mass block 42. The magnetic adsorption portion 331 may have an adsorption force with the first magnetic adsorption portion when the magnetic adsorption portion 331 is close to the first magnetic adsorption portion. This facilitates adjusting the gap of the first momentum trap using the rod position control unit 33 to ensure that a single impact loading is applied to the sample 180.

[0061] The second momentum trap 60 may further include a second magnetic adsorption portion. The second magnetic adsorption portion may be detachably connected to the second mass block 62. When the magnetic adsorption portion 331 and the second magnetic adsorption portion are close to each other, there is an adsorption force between the two. This facilitates the use of the rod position control unit 33 to adjust the gap of the second momentum trap, ensuring that a single impact loading is applied to the sample 180.

[0062] In this embodiment, Figure 6 , Figure 7 As shown, the pressure rod assembly 30 may also include an auxiliary sleeve 100. The auxiliary sleeve 100 is an open-and-close variable-section cylindrical structure. The auxiliary sleeve 100 may have a first clamping cavity 110, an avoidance cavity 130, and a second clamping cavity 120. One end of the first pressure rod 31 may be inserted into the first clamping cavity 110. One end of the second pressure rod 32 may be inserted into the second clamping cavity 120. When the sample 180 is subjected to a loading test, the sample 180 may be located in the avoidance cavity 130. There may be a gap between the inner wall of the avoidance cavity 130 and the sample 180. The inner wall of the first clamping cavity 110 can shrink and expand. The inner wall of the second clamping cavity 120 can shrink and expand. The inner diameter of the avoidance cavity 130 at the portion aligned with the sample 180 is larger than the cross-sectional diameter of the sample 180, thereby avoiding limiting the lateral expansion of the sample 180 during the impact loading process. When the first clamping cavity 110 and the second clamping cavity 120 are in a contracted state, when the first pressure rod 31 and the second pressure rod 32 are moved, the first pressure rod 31 and the second pressure rod 32 are moved synchronously, so that non-loading damage is not easily caused to the sample 180 .

[0063] In this embodiment, if Figure 7As shown, the auxiliary sleeve 100 may include a rigid outer cylinder 140, a rigid inner cylinder 150, a first elastic sleeve 160 and a second elastic sleeve 170. The rigid inner cylinder 150 may be coaxially arranged inside the rigid outer cylinder 140. One end of the first elastic sleeve 160 may be fixedly connected to the rigid outer cylinder 140, and the other end of the first elastic sleeve 160 may be fixedly connected to the rigid inner cylinder 150. One end of the second elastic sleeve 170 may be fixedly connected to the rigid outer cylinder 140, and the other end of the second elastic sleeve 170 may be fixedly connected to the rigid inner cylinder 150. The rigid outer cylinder 140, the rigid inner cylinder 150, the first elastic sleeve 160 and the second elastic sleeve 170 cooperate to form an annular cylindrical inflation cavity. The internal cavity of the first elastic sleeve 160 may be the first clamping cavity 110. The internal cavity of the second elastic sleeve 170 may be the second clamping cavity 120. The first elastic sleeve 160 and the second elastic sleeve 170 are made of flexible and high friction resistance materials. When the pressure rod assembly 30 is moved and adjusted, the contact surface between the first elastic sleeve 160 and the first pressure rod 31 is compressed and holds the rod, and the contact surface between the second elastic sleeve 170 and the second pressure rod 32 is compressed and holds the rod. Therefore, when one of the first pressure rod 31 or the second pressure rod 32 is moved by the rod position control unit 33, the other pressure rod will also be driven and adjusted to a proper position. This prevents the force of the pressure rod assembly 30 from being directly applied to the sample 180, resulting in non-loading damage to the sample 180.

[0064] In this embodiment, if Figure 7 As shown, the auxiliary sleeve 100 may also include a first force sensor and a second force sensor. The first force sensor may be located in the first clamping cavity 110. The first force sensor may be detachably connected to the inner wall of the first clamping cavity 110. The second force sensor may be located in the second clamping cavity 120. The second force sensor may be detachably connected to the inner wall of the second clamping cavity 120. The first force sensor may accurately monitor the magnitude of the loading force of the sample 180 close to one end of the first pressure rod 31 each time the first pressure rod 31 is impact loaded, and feedback to the computer. The second force sensor may accurately monitor the magnitude of the loading force of the sample 180 close to one end of the second pressure rod 32 each time the second pressure rod 32 is impact loaded, and feedback to the computer. Thus, the air pressure required for the next impact loading test may be adjusted, and the sample 180 may be subjected to an impact fatigue test.

[0065] In this embodiment, if Figure 3 , Figure 8As shown, the dynamic compression rod impact fatigue test device may include a data acquisition component 90. The data acquisition component 90 may include a first strain gauge 91, a second strain gauge 92, a first bridge box 93, a second bridge box 94, a strain amplifier 95 and an oscilloscope 96. The first strain gauge 91 is detachably connected to the first compression rod 31. The second strain gauge 92 is detachably connected to the second compression rod 32. The first strain gauge 91 and the second strain gauge 92 are symmetrically arranged about the midpoint between the first compression rod 31 and the second compression rod 32. The first bridge box 93 may be electrically connected to the first strain gauge 91 and the strain amplifier 95, respectively. The second bridge box 94 may be electrically connected to the second strain gauge 92 and the strain amplifier 95. The first bridge box 93 and the second bridge box 94 may convert the electrical signals generated by the first strain gauge 91 and the second strain gauge 92 into pulse signals for the characterization of stress and strain data. The strain amplifier 95 may amplify the transmitted weak pulse signal without distortion for the observation of the change law of stress and strain. The oscilloscope 96 is electrically connected to the strain amplifier 95. Oscilloscope 96 may be used to display real-time waveforms and to record and export test data.

[0066] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present disclosure, and in actual applications, various changes may be made thereto in form and detail without departing from the scope of the present disclosure.

Claims

1. A dynamic pressure rod impact fatigue testing device, characterized in that: The dynamic pressure rod impact fatigue testing device comprises: Workbench; A first launching assembly, the first launching assembly comprising a first driving unit, a first barrel and a first impact rod; the first driving unit and the first barrel are detachably connected to the workbench respectively; the first impact rod is slidably connected to the first barrel; A pressure rod assembly, the pressure rod assembly includes a first pressure rod and a second pressure rod, the first pressure rod is slidably connected to the workbench; the sliding direction of the first pressure rod is parallel to its own length direction; the first pressure rod and the first impact rod are coaxially arranged; the second pressure rod is slidably connected to the workbench; the sliding direction of the second pressure rod is parallel to its own length direction; there is a clamping space between the first pressure rod and the second pressure rod; the first pressure rod is located between the first barrel and the second pressure rod; the first pressure rod and the second pressure rod are coaxially arranged; A first momentum trap, wherein the first momentum trap comprises a first collision unit and a first mass block; the first collision unit is detachably connected to the first pressure rod; the first mass block is detachably connected to the workbench; the first mass block is located on a side of the first collision unit away from the first launching assembly; a first gap is provided between the first mass block and the first collision unit; the first gap is calculated using the following formula: Wherein, d1 is the first gap; ε i1 In order to cancel the first momentum trap, when the first impact rod hits the first compression rod at a preset speed, the strain of the first compression rod is measured; c 01 is the wave velocity of the stress wave in the first compression rod; T 01 is the loading pulse width of the stress wave in the first compression rod.

2. A dynamic compression rod impact fatigue testing device according to claim 1, characterized in that: The dynamic pressure rod impact fatigue testing device also includes: A second launching assembly, the second launching assembly comprising a second driving unit, a second barrel and a second impact rod; the second driving unit and the second barrel are detachably connected to the workbench respectively; the second impact rod is slidably connected to the second barrel; the second impact rod is coaxially arranged with the second pressure rod; The second momentum trap comprises a second collision unit and a second mass block; the second collision unit is detachably connected to the second pressure rod; the second mass block is detachably connected to the workbench; the second mass block is located at a side of the second collision unit away from the second launching assembly; a second gap is provided between the second mass block and the second collision unit; the second gap is calculated using the following formula: Wherein, d2 is the second gap; ε i2 In order to cancel the second momentum trap, when the second impact rod hits the second pressure rod at a preset speed, the strain of the second pressure rod is measured; c 02 is the wave velocity of the stress wave in the second compression rod; T 02 is the loading pulse width of the stress wave in the second compression rod.

3. A dynamic compression rod impact fatigue testing device according to claim 2, characterized in that: The dynamic pressure rod impact fatigue testing device also includes: A first limiting assembly, the first limiting assembly comprising a first limiting rod and a first guide portion; the first limiting rod is located between the first impact rod and the first pressure rod; the first guide portion is detachably connected to the workbench; the first limiting rod is slidably connected to the first guide portion; the sliding direction of the first limiting rod is parallel to its own length direction; the first guide portion limits the sliding distance of the first limiting rod; the first limiting rod is coaxially arranged with the first impact rod; The second limiting assembly includes a second limiting rod and a second guide portion; the second limiting rod is located between the second impact rod and the second pressure rod; the second guide portion is detachably connected to the workbench; the second limiting rod is slidably connected to the second guide portion; the sliding direction of the second limiting rod is parallel to its own length direction; the second guide portion limits the sliding distance of the second limiting rod; the second limiting rod is coaxially arranged with the second impact rod.

4. A dynamic compression rod impact fatigue testing device according to claim 2, characterized in that: The first firing assembly further includes a first reset unit, which includes a first air pump and a first pressure-sensitive sensor; the first air pump is connected to the first barrel; the air suction port of the first air pump is located between the first drive unit and the first impact rod; the first pressure-sensitive sensor is detachably connected to the first barrel; the first pressure-sensitive sensor is located at the end of the first barrel facing the first drive unit; The second firing assembly also includes a second reset unit, which includes a second vacuum pump and a second pressure-sensitive sensor; the second vacuum pump is connected to the second barrel; the vacuum port of the second vacuum pump is located between the second drive unit and the second impact rod; the second pressure-sensitive sensor is detachably connected to the second barrel; the second pressure-sensitive sensor is located at the end of the second barrel facing the second drive unit.

5. The dynamic compression rod impact fatigue testing device according to claim 2, characterized in that: The pressure rod assembly also includes a rod position control unit; the rod position control unit includes a magnetic part and a sliding part; the sliding part is detachably connected to the workbench; the magnetic part is detachably connected to the sliding part; the sliding part drives the magnetic part to move; the moving direction of the magnetic part is parallel to the moving direction of the first impact rod.

6. A dynamic compression rod impact fatigue testing device according to claim 5, characterized in that: The first momentum trap further includes a first magnetic adsorption portion; the first magnetic adsorption portion is detachably connected to the first mass block; when the magnetic adsorption portion and the first magnetic adsorption portion are close to each other, there is an adsorption force between the two; The second momentum trap further includes a second magnetic adsorption portion; the second magnetic adsorption portion is detachably connected to the second mass block; and when the magnetic adsorption portion and the second magnetic adsorption portion are close to each other, there is an adsorption force between the two.

7. The dynamic compression rod impact fatigue testing device according to claim 1, characterized in that: The pressure rod assembly also includes an auxiliary sleeve; the auxiliary sleeve has a first clamping cavity, an avoidance cavity and a second clamping cavity; one end of the first pressure rod is inserted into the first clamping cavity; one end of the second pressure rod is inserted into the second clamping cavity; when a loading test is performed on a specimen; the specimen is located in the avoidance cavity; the inner wall of the avoidance cavity has a gap with the specimen; the inner wall of the first clamping cavity can shrink and expand; the inner wall of the second clamping cavity can shrink and expand.

8. The dynamic compression rod impact fatigue testing device according to claim 7, characterized in that: The auxiliary sleeve includes a rigid outer sleeve, a rigid inner sleeve, a first elastic sleeve and a second elastic sleeve; the rigid inner sleeve is coaxially inserted into the rigid outer sleeve; one end of the first elastic sleeve is fixedly connected to the rigid outer sleeve, and the other end of the first elastic sleeve is fixedly connected to the rigid inner sleeve; one end of the second elastic sleeve is fixedly connected to the rigid outer sleeve, and the other end of the second elastic sleeve is fixedly connected to the rigid inner sleeve; the rigid outer sleeve, the rigid inner sleeve, the first elastic sleeve and the second elastic sleeve cooperate to form an annular cylindrical inflation cavity; the internal cavity of the first elastic sleeve is the first clamping cavity; the internal cavity of the second elastic sleeve is the second clamping cavity.

9. The dynamic compression rod impact fatigue testing device according to claim 7, characterized in that: The auxiliary sleeve also includes a first force sensor and a second force sensor; the first force sensor is located in the first clamping cavity; the first force sensor is detachably connected to the inner wall of the first clamping cavity; the second force sensor is located in the second clamping cavity; the second force sensor is detachably connected to the inner wall of the second clamping cavity.

10. The dynamic compression rod impact fatigue testing device according to claim 2, characterized in that: The dynamic compression rod impact fatigue testing device includes a data acquisition component; the data acquisition component includes a first strain gauge, a second strain gauge, a first bridge box, a second bridge box, a strain amplifier and an oscilloscope, the first strain gauge is detachably connected to the first compression rod; the second strain gauge is detachably connected to the second compression rod; the first strain gauge and the second strain gauge are symmetrically arranged about the midpoint between the first compression rod and the second compression rod; the first bridge box is electrically connected to the first strain gauge and the strain amplifier respectively; the second bridge box is electrically connected to the second strain gauge and the strain amplifier respectively; the oscilloscope is electrically connected to the strain amplifier.

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