Rock dynamic bending test device and test method based on SHPB system

Abstract

The invention discloses a rock dynamic bending test device based on a SHPB system and a test method thereof. The rock dynamic bending test device based on the SHPB system comprises a launching device, an impact rod, an incident rod, a transmission rod, an absorption rod and a measuring system. The launching device is used for launching a bullet and impacting the incident rod through the impact rod. The incident rod, the transmission rod and the absorption rod are coaxially arranged. A gap is left between the incident rod and the transmission rod. The absorption rod is attached to one end of the transmission rod. The measuring system is used for capturing the impact effect of the incident rod and the transmission rod. A bending rod is connected to one end of the incident rod. A rock sample bending rod is connected to the transmission rod. A slot for placing a sample is provided at one end of the rock sample bending rod. An avoidance slot for the bending rod to extend into is also provided on the rock sample bending rod. The avoidance slot is communicated with the slot. The advantages are that the test is reliable and the test effect is good.

Description

Technical Field

[0001] The invention relates to the technical field of rock performance testing, and in particular to a rock dynamic bending test device based on a SHPB system and a test method thereof. Background Art

[0002] The research on dynamic compression and tension test of rock mainly adopts the Hopkinson pressure bar system, also known as SHPB system. The system mainly includes data acquisition and processing devices such as launch device, impact bar, incident bar, transmission bar, absorption bar, ultra-dynamic strain gauge, oscilloscope, etc. The incident pulse and reflected pulse signal are recorded by the strain gauge attached to the incident bar, and the transmission pulse signal is recorded by the strain gauge attached to the transmission bar. On this basis, the relevant dynamic mechanical performance data of the material can be obtained based on the one-dimensional stress wave theory. However, the system has not been expanded in the dynamic flexural test of rock. Due to the fact that there are engineering components with a large aspect ratio in the construction process of engineering projects, such as beam components in buildings and piles in bridges, the weak point of their destruction is breaking and losing their use function. After the infrastructure is built and put into operation, it will be subjected to more dynamic load impacts. The existing static flexural test obviously cannot meet the needs of actual engineering. Therefore, in order to serve the main battlefield of national economic construction, it is of great practical significance to develop a set of equipment for carrying out dynamic flexural test of rock. Summary of the invention

[0003] In order to solve the above-mentioned deficiencies in the prior art, the present invention provides a rock dynamic bending test device and a test method based on a SHPB system, which are reliable and have good test effects.

[0004] The technical solution adopted by the present invention to solve the above technical problems is: a rock dynamic bending test device based on the SHPB system, including a launching device, an impact rod, an incident rod, a transmission rod, an absorption rod and a measuring system, the launching device is used to launch a bullet and impact the incident rod through the impact rod, the incident rod, the transmission rod and the absorption rod are coaxially arranged, a gap is left between the incident rod and the transmission rod, the absorption rod is attached to one end of the transmission rod, the measuring system is used to capture the impact effect of the incident rod and the transmission rod, one end of the incident rod is connected to a bending rod, the transmission rod is connected to a rock sample bending rod, one end of the rock sample bending rod is provided with a slot for placing a sample, the rock sample bending rod is also provided with an avoidance groove for the bending rod to extend into, and the avoidance groove is connected to the slot.

[0005] The diameter of the bending rod is equal to the diameter of the rock sample folding rod, the length of the bending rod is equal to the length of the rock sample folding rod, one end of the bending rod has a wedge-shaped head, both sides of the wedge-shaped head are respectively provided with an arched surface, and the chord height of the arched surface is 1 / 4-1 / 2 of the length of the bending rod. In this structure, the bending rod and the rock sample folding rod have the same specifications, which is conducive to processing and manufacturing, saving manufacturing costs, and the wedge-shaped head at one end of the bending rod can bend the sample into the avoidance groove when it contacts the sample, which is convenient for testing.

[0006] The width of the avoidance groove is 1 / 3-2 / 5 of the diameter of the rock sample folding rod, and the depth of the avoidance groove is 1 / 4-1 / 2 of the length of the rock sample folding rod. The advantage is that it is compatible with the bending rod, which is conducive to the wedge-shaped head to smoothly and steadily enter the avoidance groove.

[0007] A first locking assembly is arranged between the bending rod and the incident rod. In this structure, the arrangement of the first locking assembly facilitates the quick disassembly and assembly of the bending rod and the incident rod, and the connection between the two is relatively firm.

[0008] The first locking assembly includes a first clamp and a second clamp, wherein the first clamp is tightly attached between the upper side wall of the bending rod and the upper side wall of the incident rod, and the second clamp is tightly attached between the lower side wall of the bending rod and the lower side wall of the incident rod, and the first clamp and the second clamp are fixed by a first locking bolt. In this structure, when the bending rod needs to be installed on the incident rod, the bending rod is first docked with the incident rod, and then the first clamp and the second clamp are installed in sequence, and finally the first clamp and the second clamp are locked by the first locking bolt, thereby realizing a reliable connection between the bending rod and the incident rod.

[0009] A second locking assembly is arranged between the transmission rod and the rock sample buckling rod. In this structure, the arrangement of the second locking assembly facilitates the rapid disassembly and assembly of the rock sample buckling rod and the transmission rod, and the connection between the two is relatively firm.

[0010] The second locking assembly includes a third clamp and a fourth clamp, wherein the third clamp is tightly attached between the upper side wall of the transmission rod and the upper side wall of the rock sample buckling rod, and the fourth clamp is tightly attached between the lower side wall of the transmission rod and the lower side wall of the rock sample buckling rod, and the third clamp and the fourth clamp are fixed by a second locking bolt. In this structure, when the rock sample buckling rod needs to be installed on the transmission rod, the rock sample buckling rod is first docked with the transmission rod, and then the third clamp and the fourth clamp are installed in sequence, and finally the third clamp and the fourth clamp are locked by the second locking bolt, thereby realizing a reliable connection between the rock sample buckling rod and the transmission rod.

[0011] The measuring system comprises a first strain gauge, a second strain gauge, a third strain gauge, a fourth strain gauge, a high-speed camera, a first super-dynamic strain gauge and a second super-dynamic strain gauge, wherein the first strain gauge is mounted on the incident rod, the second strain gauge is mounted on the transmission rod, the third strain gauge is mounted on the bending rod, and the fourth strain gauge is mounted on the rock sample impact rod. The high-speed camera records the destruction process of the sample when the bullet is fired and hits the sample. The first super-dynamic strain gauge is electrically connected to the first strain gauge and the second strain gauge respectively, and the second super-dynamic strain gauge is electrically connected to the third strain gauge and the fourth strain gauge respectively. The advantage is that the test results can be accurately recorded.

[0012] Vaseline is applied between the incident rod and the bending rod, and vaseline is also applied between the transmission rod and the rock sample bending rod, so that the shock wave can be transmitted better.

[0013] The present invention also discloses a rock dynamic bending test method based on the SHPB system, using a rock dynamic bending test device based on the SHPB system, comprising the following steps:

[0014] S1: The first voltage-time curve V of the incident strain of the Hopkinson bar measured by the first strain gauge i1 , the second voltage-time curve V of the Hopkinson bar transmission strain is measured by the second strain gauge t1 The third voltage-time curve V of the incident strain of the Hopkinson bar is measured by the third strain gauge i2 , the fourth voltage-time curve V of the Hopkinson bar transmission strain is measured by the fourth strain gauge t2 ;

[0015] S2: The first voltage-time curve V i1 Dividing by the magnification factor C, we get the first time history curve ε of the incident strain of the Hopkinson bar. i1 , the second voltage-time curve V t1 Divided by the magnification factor C, the second time history curve ε of the transmission strain of the Hopkinson pressure bar is obtained t1 , the third voltage time curve V i2 Divided by the magnification factor C, the third time history curve ε of the incident strain of the Hopkinson bar is obtained i2 , the fourth voltage time curve V t2 Dividing by the magnification factor C, we get the fourth time history curve ε of the transmission strain of the Hopkinson bar. t2 Then the first time history curve ε i1 and the third time curve ε i2 By comparison, the conversion coefficient η is obtained i, the second time history curve ε t1 and the fourth time curve ε t2 By comparison, the conversion coefficient η is obtained t , take η i With η t The larger value is divided by the smaller value. If the ratio of the two is between 1 and 1.2, go to step S3. If it exceeds this range, reinstall the bending rod and the rock sample bending rod until the requirements are met.

[0016] S3: Before the formal experiment, verify that the incident rod and the transmitted rod meet the one-dimensional stress wave condition σ i (t)+σ r (t) = σ t (t) Hopkinson pressure bar, where: σ i (t) represents the incident stress, σ r (t) represents the reflected stress, σ t (t) represents the transmission stress;

[0017] S4: The launching device is used to launch the bullet and hit the incident rod through the impact rod to load the sample so that its strain rate is 10 2 ~10 3 s -1 between;

[0018] S5: The incident wave and the transmitted wave in the Hopkinson bar are measured by setting the first strain gauge and the second strain gauge, and the average strain is calculated according to the following formula and mean stress The dynamic stress-strain relationship of the material is obtained.

[0019]

[0020]

[0021] Where: c is the longitudinal wave velocity m / s; l s is the sample length m; ε i is the incident strain, vector; ε r is the reflected strain, vector; ε t is the transmission strain, vector; A is the cross-sectional area of ​​the rod m 2 ; A S is the impact area of ​​the specimen m 2 ; E is the elastic modulus of the rod GPa;

[0022] S6: Calculate the dynamic flexural modulus of the sample according to the following formula:

[0023] Where E dz is the dynamic flexural modulus, P(t)max is the maximum value of the impact load P(t), L is the length of the specimen (mm), b is the width of the specimen section (mm), and h is the height of the specimen section (mm). The impact load P(t) is calculated using the following formula:

[0024]

[0025] Among them; ε i is the incident strain, vector; ε r is the reflected strain, vector; ε t is the transmission strain, vector; A is the cross-sectional area of ​​the rod m 2 ; E is the elastic modulus of the rod GPa;

[0026] S7: The fracture process of the sample is filmed with a high-speed camera to analyze and determine the macroscopic fracture failure mechanism of the sample. Then, the fracture site of the sample is scanned with an electron microscope to analyze the microscopic morphology of the fracture surface and the microscopic failure characteristics.

[0027] Compared with the prior art, the advantages of the present invention are: the slot on the rock sample bending rod is used to install the sample to be tested, and the avoidance groove provides an avoidance space so that the part of the sample to be tested can enter the avoidance groove after being bent; the bending rod is connected to the incident rod, and after receiving it, it acts on the sample to be tested to bend the sample to be tested, thereby performing a bending test; the test of this device is reliable and the test effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the present invention;

[0029] Figure 2 It is a schematic diagram of the three-dimensional structure when the bending rod and the rock sample bending rod in the present invention cooperate with each other;

[0030] Figure 3 For the present invention Figure 2 Schematic diagram of the three-dimensional structure in the decomposed state;

[0031] Figure 4 It is a schematic diagram of the three-dimensional structure of the bending rod in the present invention;

[0032] Figure 5 It is a schematic diagram of the three-dimensional structure of the rock sample folding rod in the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0034] Embodiment 1: As shown in the figure, a rock dynamic bending test device based on the SHPB system includes a launching device 1, an impact rod 2, an incident rod 3, a transmission rod 4, an absorption rod 5 and a measuring system 6. The launching device 1 is used to launch a bullet and impact the incident rod 3 through the impact rod 2. The incident rod 3, the transmission rod 4 and the absorption rod 5 are coaxially arranged. A gap is left between the incident rod 3 and the transmission rod 4. The absorption rod 5 is attached to one end of the transmission rod 4. The measuring system 6 is used to capture the impact effect of the incident rod 3 and the transmission rod 4. A bending rod 7 is connected to one end of the incident rod 3, and a rock sample bending rod 8 is connected to the transmission rod 4. A slot 81 for placing a sample is provided at one end of the rock sample bending rod 8. An avoidance groove 82 for the bending rod 7 to extend into is also provided on the rock sample bending rod 8, and the avoidance groove 82 is connected to the slot 81.

[0035] The diameter of the bending rod 7 is equal to the diameter of the rock sample buckling rod 8, the length of the bending rod 7 is equal to the length of the rock sample buckling rod 8, one end of the bending rod 7 has a wedge-shaped head 71, and both sides of the wedge-shaped head 71 are respectively provided with an arched surface 72, and the chord height of the arched surface 72 is 1 / 4-1 / 2 of the length of the bending rod 7. In this structure, the bending rod 7 and the rock sample buckling rod 8 have the same specifications, which is conducive to processing and manufacturing, saving manufacturing costs, and the wedge-shaped head 71 at one end of the bending rod 7 can bend the sample into the avoidance groove 82 when it contacts the sample, which is convenient for testing.

[0036] The width of the avoidance groove 82 is 1 / 3-2 / 5 of the diameter of the rock sample folding rod 8, and the depth of the avoidance groove 82 is 1 / 4-1 / 2 of the length of the rock sample folding rod 8. Its advantage is that it is compatible with the bending rod 7, which is conducive to the wedge-shaped head 71 to enter the avoidance groove 82 smoothly and steadily.

[0037] A first locking assembly 91 is provided between the bending rod 7 and the incident rod 3. In this structure, the provision of the first locking assembly 91 facilitates the quick disassembly and assembly of the bending rod 7 and the incident rod 3, and the connection between the two is relatively firm.

[0038] The first locking assembly 91 includes a first clamp 93 and a second clamp 94, the first clamp 93 is closely attached between the upper side wall of the bending rod 7 and the upper side wall of the incident rod 3, the second clamp 94 is closely attached between the lower side wall of the bending rod 7 and the lower side wall of the incident rod 3, and the first clamp and the second clamp are fixed by a first locking bolt 95. In this structure, when the bending rod 7 needs to be installed on the incident rod 3, the bending rod 7 is first docked with the incident rod 3, and then the first clamp and the second clamp are installed in sequence, and finally the first clamp and the second clamp are locked by the first locking bolt, so as to achieve a reliable connection between the bending rod 7 and the incident rod 3.

[0039] A second locking assembly 92 is provided between the transmission rod 4 and the rock sample buckling rod 8. In this structure, the provision of the second locking assembly 92 facilitates the rapid disassembly and assembly of the rock sample buckling rod 8 and the transmission rod 4, and the connection between the two is relatively firm.

[0040] The second locking assembly 92 includes a third clamp 96 and a fourth clamp 97, the third clamp 96 is closely attached between the upper side wall of the transmission rod 4 and the upper side wall of the rock sample buckling rod 8, the fourth clamp 97 is closely attached between the lower side wall of the transmission rod 4 and the lower side wall of the rock sample buckling rod 8, and the third clamp and the fourth clamp are fixed by a second locking bolt 98. In this structure, when the rock sample buckling rod 8 needs to be installed on the transmission rod 4, the rock sample buckling rod 8 is first docked with the transmission rod 4, and then the third clamp and the fourth clamp are installed in sequence, and finally the third clamp and the fourth clamp are locked by the second locking bolt, so as to achieve a reliable connection between the rock sample buckling rod 8 and the transmission rod 4.

[0041] The measuring system 6 includes a first strain gauge 61, a second strain gauge 62, a high-speed camera 63 and a first super-dynamic strain gauge 64. The first strain gauge 61 is installed on the incident rod 3, the second strain gauge 62 is installed on the transmission rod 4, the high-speed camera 63 records the entire destruction process of the sample when the bullet is fired and hits the sample, and the first super-dynamic strain gauge 64 is electrically connected to the first strain gauge 61 and the second strain gauge 62. The advantage is that the test results can be accurately recorded.

[0042] The measuring system 6 includes a third strain gauge 65, a fourth strain gauge 66 and a second super dynamic strain gauge 67. The third strain gauge 65 is mounted on the bending rod 7, the fourth strain gauge 66 is mounted on the rock sample bending rod 8, and the second super dynamic strain gauge 67 is electrically connected to the third strain gauge 65 and the fourth strain gauge 66. The advantage is that the test results can be accurately recorded.

[0043] Vaseline is smeared between the incident rod 3 and the bending rod 7, and vaseline is also smeared between the transmission rod 4 and the rock sample bending rod 8.

[0044] Embodiment 2: As shown in the figure, a rock dynamic bending test method based on the SHPB system, using the rock dynamic bending test device based on the SHPB system in Embodiment 1, includes the following steps:

[0045] S1: The first voltage-time curve V of the incident strain of the Hopkinson bar measured by the first strain gauge i1 , the second voltage-time curve V of the Hopkinson bar transmission strain is measured by the second strain gauge t1 The third voltage-time curve V of the incident strain of the Hopkinson bar is measured by the third strain gauge i2 , the fourth voltage-time curve V of the Hopkinson bar transmission strain is measured by the fourth strain gauget2 ;

[0046] S2: The first voltage-time curve V i1 Dividing by the magnification factor C, we get the first time history curve ε of the incident strain of the Hopkinson bar. i1 , the second voltage-time curve V t1 Divided by the magnification factor C, the second time history curve ε of the transmission strain of the Hopkinson bar is obtained t1 , the third voltage time curve V i2 Divided by the magnification factor C, the third time history curve ε of the incident strain of the Hopkinson bar is obtained i2 , the fourth voltage time curve V t2 Dividing by the magnification factor C, we get the fourth time history curve ε of the transmission strain of the Hopkinson bar. t2 Then the first time history curve ε i1 and the third time curve ε i2 By comparison, the conversion coefficient η is obtained i , the second time history curve ε t1 and the fourth time curve ε t2 By comparison, the conversion coefficient η is obtained t , take η i With η t The larger value is divided by the smaller value. If the ratio of the two is between 1 and 1.2, go to step S3. If it exceeds this range, reinstall the bending rod and the rock sample bending rod until the requirements are met.

[0047] S3: Before the formal experiment, verify that the incident rod and the transmitted rod meet the one-dimensional stress wave condition σ i (t)+σ r (t) = σ t (t) Hopkinson pressure bar, where: σ i (t) represents the incident stress, σ r (t) represents the reflected stress, σ t (t) represents the transmission stress;

[0048] S4: The launching device is used to launch the bullet and hit the incident rod through the impact rod to load the sample so that its strain rate is 10 2 ~10 3 s -1 between;

[0049] S5: The incident wave and the transmitted wave in the Hopkinson bar are measured by setting the first strain gauge and the second strain gauge, and the average strain is calculated according to the following formula and mean stress The dynamic stress-strain relationship of the material is obtained.

[0050]

[0051]

[0052] Where: c is the longitudinal wave velocity m / s; l s is the sample length m; ε i is the incident strain, vector; ε r is the reflected strain, vector; ε t is the transmission strain, vector; A is the cross-sectional area of ​​the rod m 2 ; A S is the impact area of ​​the specimen m 2 ; E is the elastic modulus of the rod GPa;

[0053] S6: Calculate the dynamic flexural modulus of the sample according to the following formula:

[0054] Where E dz is the dynamic flexural modulus, P(t) max is the maximum value of the impact load P(t), L is the length of the specimen (mm), b is the width of the specimen section (mm), and h is the height of the specimen section (mm). The impact load P(t) is calculated using the following formula:

[0055]

[0056] Among them; ε i is the incident strain, vector; ε r is the reflected strain, vector; ε t is the transmission strain, vector; A is the cross-sectional area of ​​the rod m 2 ; E is the elastic modulus of the rod GPa;

[0057] S7: The fracture process of the sample is filmed with a high-speed camera to analyze and determine the macroscopic fracture failure mechanism of the sample. Then, the fracture site of the sample is scanned with an electron microscope to analyze the microscopic morphology of the fracture surface and the microscopic failure characteristics.

[0058] The cross-sectional areas of the incident rod, bending rod, transmission rod and rock sample impact rod and the selected materials are consistent, so the cross-sectional area of ​​the rod and the elastic modulus of the rod are constant values, and the magnification coefficient C is the parameter of the equipment itself, and 600 is selected in this embodiment.

[0059] It is worth noting that the above is only a preferred embodiment of the present invention, and does not limit the scope of patent protection of the present invention. The present invention can also improve the materials and structures of the above-mentioned various parts, or replace them with technical equivalents. Therefore, all equivalent structural changes made by using the description and illustrations of the present invention, or directly or indirectly applied to other related technical fields are also included in the scope of the present invention.

Claims

1. A rock dynamic bending test method based on a SHPB system, using a rock dynamic bending test device based on a SHPB system, the rock dynamic bending test device based on the SHPB system comprising a launch device, a striker, an incident rod, a transmission rod, an absorption rod and a measurement system, the launch device is used to launch a bullet and impact the incident rod through the striker, the incident rod, the transmission rod and the absorption rod are coaxially arranged, a gap is left between the incident rod and the transmission rod, the absorption rod is attached to one end of the transmission rod, the measurement system is used to capture the impact effect of the incident rod and the transmission rod, one end of the incident rod is connected to a bending rod, the transmission rod is connected to a rock sample bending rod, one end of the rock sample bending rod is provided with a slot for placing a sample, the rock sample bending rod is also provided with an avoidance groove for the bending rod to extend into, and the avoidance groove is connected to the slot; The diameter of the bending rod is equal to the diameter of the rock sample bending rod, the length of the bending rod is equal to the length of the rock sample bending rod, one end of the bending rod has a wedge-shaped head, both sides of the wedge-shaped head are respectively provided with arched surfaces, the chord height of the arched surface is 1 / 4-1 / 2 of the length of the bending rod, the width of the avoidance groove is 1 / 3-2 / 5 of the diameter of the rock sample bending rod, and the depth of the avoidance groove is 1 / 4-1 / 2 of the length of the rock sample bending rod; A second locking assembly is provided between the transmission rod and the rock sample buckling rod, and the second locking assembly includes a third hoop and a fourth hoop, the third hoop is tightly attached between the upper side wall of the transmission rod and the upper side wall of the rock sample buckling rod, the fourth hoop is tightly attached between the lower side wall of the transmission rod and the lower side wall of the rock sample buckling rod, and the third hoop and the fourth hoop are fixed by a second locking bolt; The measuring system comprises a first strain gauge, a second strain gauge, a third strain gauge, a fourth strain gauge, a high-speed camera, a first ultra-dynamic strain gauge and a second ultra-dynamic strain gauge, wherein the first strain gauge is mounted on the incident rod, the second strain gauge is mounted on the transmission rod, the third strain gauge is mounted on the bending rod, and the fourth strain gauge is mounted on the rock sample impact rod. The high-speed camera records the destruction process of the sample when the bullet is fired and hits the sample. The first ultra-dynamic strain gauge is electrically connected to the first strain gauge and the second strain gauge, respectively, and the second ultra-dynamic strain gauge is electrically connected to the third strain gauge and the fourth strain gauge, respectively. The measuring system is characterized in that: The following steps are included: S1: The first voltage-time curve V of the incident strain of the Hopkinson bar measured by the first strain gauge i1 , the second voltage-time curve V of the Hopkinson bar transmission strain is measured by the second strain gauge t1 The third voltage-time curve V of the incident strain of the Hopkinson bar is measured by the third strain gauge i2 , the fourth voltage-time curve V of the Hopkinson bar transmission strain is measured by the fourth strain gauge t2 ; S2: The first voltage-time curve V i1 Dividing by the magnification factor C, we get the first time history curve ε of the incident strain of the Hopkinson bar. i1 , the second voltage-time curve V t1 Divided by the magnification factor C, the second time history curve ε of the transmission strain of the Hopkinson pressure bar is obtained t1 , the third voltage time curve V i2 Divided by the magnification factor C, the third time history curve ε of the incident strain of the Hopkinson bar is obtained i2 , the fourth voltage time curve V t2 Dividing by the magnification factor C, we get the fourth time history curve ε of the transmission strain of the Hopkinson bar. t2 Then the first time history curve ε i1 and the third time curve ε i2 By comparison, the conversion coefficient η is obtained i , the second time history curve ε t1 and the fourth time curve ε t2 By comparison, the conversion coefficient η is obtained t , take η i With η t The larger value is divided by the smaller value. If the ratio of the two is between 1 and 1.2, go to step S3. If it exceeds this range, reinstall the bending rod and the rock sample bending rod until the requirements are met. S3: Before the formal experiment, verify that the incident rod and the transmitted rod meet the one-dimensional stress wave condition σ i (t)+σ r (t) = σ t (t) Hopkinson pressure bar, where: σ i (t) represents the incident stress, σ r (t) represents the reflected stress, σ t (t) represents the transmission stress; S4: The launching device is used to launch the bullet and hit the incident rod through the impact rod to load the sample so that its strain rate is 10 2 ~10 3 s -1 between; S5: The incident wave and the transmitted wave in the Hopkinson bar are measured by setting the first strain gauge and the second strain gauge, and the average strain is calculated according to the following formula and mean stress The dynamic stress-strain relationship of the material is obtained. Where: c is the longitudinal wave velocity m / s; l s is the sample length m; ε i is the incident strain, vector; ε r is the reflected strain, vector; ε t is the transmission strain, vector; A is the cross-sectional area of ​​the rod m 2 ; A S is the impact area of ​​the specimen m 2 ; E is the elastic modulus of the rod GPa; S6: Calculate the dynamic flexural modulus of the sample according to the following formula: Where E dz is the dynamic flexural modulus, P(t) max is the maximum value of the impact load P(t), L is the length of the specimen (mm), b is the width of the specimen section (mm), and h is the height of the specimen section (mm). The impact load P(t) is calculated using the following formula: Among them; ε i is the incident strain, vector; ε r is the reflected strain, vector; ε t is the transmission strain, vector; A is the cross-sectional area of ​​the rod m 2 ; E is the elastic modulus of the rod GPa; S7: The fracture process of the sample is filmed with a high-speed camera to analyze and determine the macroscopic fracture failure mechanism of the sample. Then, the fracture site of the sample is scanned with an electron microscope to analyze the microscopic morphology of the fracture surface and the microscopic failure characteristics.

2. The rock dynamic bending test method based on the SHPB system according to claim 1 is characterized in that: A first locking assembly is arranged between the bending rod and the incident rod.

3. The rock dynamic bending test method based on the SHPB system according to claim 2 is characterized in that: The first locking assembly includes a first hoop and a second hoop, the first hoop is tightly attached between the upper side wall of the bending rod and the upper side wall of the incident rod, the second hoop is tightly attached between the lower side wall of the bending rod and the lower side wall of the incident rod, and the first hoop and the second hoop are fixed by a first locking bolt.

4. The rock dynamic bending test method based on the SHPB system according to claim 1 is characterized in that: Vaseline is smeared between the incident rod and the bending rod, and vaseline is also smeared between the transmission rod and the rock sample bending rod.

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