Gunpowder type dynamic tensile test device and method

Abstract

The invention discloses a gunpowder type dynamic tensile test device and method, and relates to the technical field of dynamic tensile tests. Compared with a previous tensile test device, the problem that the size of a test piece is limited by an existing test device is solved; the dynamic tensile property of a large-size material cannot be tested. The novel material dynamic tensile test technology which is economical, practical and scientific in design principle is provided, gunpowder serves as a tensile power source, the rapid loading direct simulation type tensile test technology is adopted, the dynamic tensile mechanical properties of the material at different loading rates can be obtained by selecting different gunpowder, the loading rate change range is large, and the mechanical property of the material can be improved. The stretching requirements of large-size materials can be met; the method can correspond to static stretching measurement, and analysis and comparison of materials are facilitated; a specific material loading condition can be easily simulated, and the dynamic performance of the material can be tested; and the device is simple in structure and stable in performance.

Description

Technical Field

[0001] The invention relates to the technical field of dynamic tensile testing, and in particular to a gunpowder type dynamic tensile testing device and method. Background Art

[0002] With the development of science and technology and production, the scientific and technological community has made great progress in the study of the mechanical properties of materials under high strain rates. The research and use of the separated (Hopkinson bar) Hopkinson test technology has been widely carried out. It uses the strain signal recorded in the test to obtain the stress, strain and strain rate curves of the tested material according to the one-dimensional plane stress wave theory. However, due to some structural and technical reasons of the test device, the size of the test specimen is subject to certain restrictions, such as the test of the dynamic properties of reinforced concrete; in addition, the compression and tensile properties of many materials are significantly different. How to test the dynamic tensile properties of large-size materials has become a difficulty in the existing technology.

[0003] In order to solve the above problems, the present invention proposes a gunpowder type dynamic tensile testing device and method. Summary of the invention

[0004] The purpose of the present invention is to provide a gunpowder type dynamic tensile test device and method to solve the problems raised in the background technology:

[0005] Existing test equipment limits the size of test specimens; it is not possible to test the dynamic tensile properties of large-sized materials.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The explosive type dynamic tensile test device comprises: a dynamic pressure generator and left and right clamps;

[0008] The dynamic pressure generator is a side-mounted U-shaped structure, with a pressure sensor position point arranged above the dynamic pressure generator, a small opening arranged on one side for loading gunpowder into the groove, and a T-shaped sliding block arranged at the groove opening on the other side. Two parallel force transmission rods are vertically arranged at the top of both ends of the T-shaped transverse end of the sliding block, and the other end of the force transmission rod is fixed on the U-shaped frame. The other ends of the two force transmission rods are also fixed by a transverse force transmission rod, and left and right clamps are vertically arranged at the midpoint of the transverse force transmission rod; the two clamps of the left and right clamps are both T-shaped structures with the transverse ends arranged opposite to each other, wherein the vertical end of the right clamp is fixed at the midpoint of the transverse force transmission rod, and the vertical end of the left clamp is fixed inside the device.

[0009] Preferably, an acceleration sensor position point is disposed at the vertical end of the right clamp, and a force sensor position point is disposed at the vertical end of the left clamp.

[0010] Preferably, it also includes a tension transmission system, a force application scheme monitoring system, and a tension and deformation recording system, which are respectively used for tension transmission and data monitoring at corresponding positions.

[0011] The explosive type dynamic tensile test method comprises the following steps:

[0012] S1: Configure and test the dynamic pressure generator, left and right grippers, pressure sensor, force sensor, acceleration sensor, tension transmission system, force application scheme monitoring, tension and deformation recording system;

[0013] S2: Clamp the specimen between the left and right clamps;

[0014] S3: According to the loading rate required by the specimen, select the corresponding gunpowder as the power source;

[0015] S4: Charge ignition work, through the force transmission rod, sliding block and left and right clamps, the specimen is loaded and stretched, and the specimen undergoes elastic, plastic and fracture changes in sequence at the corresponding deformation rate;

[0016] S5: The force application scheme monitoring, tension and deformation recording system records the mechanical parameter values ​​of the test process;

[0017] S6: Obtain relevant data of the specimen through curve calibration and data processing;

[0018] S7: By adjusting the parameters of the gunpowder and the installation posture of the specimen, the tensile properties of the specimen under different loading rates are tested to obtain the dynamic tensile curves under different strain rates.

[0019] Preferably, in S2, the specimen is clamped by aligning it with the center of the left and right clamps, and the specimen is ensured to be subjected to axial force.

[0020] Preferably, in S5, the pressure sensor records the pressure-time variation curve of the dynamic pressure generator when it is working, the force sensor records the force-time variation curve of the specimen when it is tensilely deformed, and the acceleration sensor records the acceleration-time variation curve of the sliding block moving with the specimen.

[0021] Preferably, in S6, the dynamic yield stress of the material is calculated based on the elastic-plastic modified theory and the elastic-plastic theory respectively;

[0022] The improved elastic-plastic theory uses the energy conservation equation on the plastic wave front to establish the relationship between the dynamic yield stress of the material:

[0023]

[0024] Among them, σ Dis the yield stress value of the material under test; ρ is the density of the material under test; v0 is the tensile speed of the material under test; e0, is the axial engineering strain of the material under test corresponding to v0; n1 is the unit direction of plastic flow of the material under test;

[0025] The elastic-plastic theory establishes the relationship between the dynamic yield stress of the material under the condition that the plastic wave front is exactly located at the rigid-incremental interface:

[0026]

[0027] Wherein, L1 is the length of the material after being stretched; L0 is the initial unstretched length of the material under test; and h is the length change of the material under test after stretching.

[0028] Compared with the prior art, the present invention provides a gunpowder type dynamic tensile test device and method, which has the following beneficial effects:

[0029] The invention provides a new, economical and practical material dynamic tensile test technology with scientific design principles. The invention uses gunpowder as a tensile power source and a rapid loading direct simulation tensile test technology. By selecting different gunpowders, the dynamic tensile mechanical properties of the material under different loading rates can be obtained, and the loading rate has a large variation range and can adapt to the tensile requirements of large-size materials. The invention can correspond to static tensile measurement and is convenient for material analysis and comparison. The invention is easy to simulate specific material loading conditions and realize the test of the dynamic properties of the material. The device of the invention has a simple structure and stable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the test device mentioned in Example 1 of the present invention;

[0031] Figure 2 Schematic diagram of the laser interferometer micro-displacement measurement test device mentioned in Example 2 of the present invention.

[0032] Meaning of the symbols in the figure:

[0033] 1. Gunpowder; 2. Dynamic pressure generator; 3. Test piece; 4. Left and right clamps; 5. Force transmission rod; 6. Pressure sensor location point; 7. Force sensor location point; 8. Acceleration sensor location point; 9. Sliding block; 10. Laser interferometer micro-displacement measuring device. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0035] The present invention provides a new, economical and practical material dynamic tensile test technology with scientific design principles. It uses gunpowder as the tensile power source and a rapid loading direct simulation tensile test technology. By selecting different gunpowders, the dynamic tensile mechanical properties of materials at different loading rates can be obtained, and the loading rate has a large range of variation, which can meet the tensile requirements of large-size materials; it can correspond to static tensile measurement, which is convenient for material analysis and comparison; it is easy to simulate specific material loading conditions and realize the test of material dynamic properties; and the device of the present invention has a simple structure and stable performance. Specifically, it includes the following contents.

[0036] Embodiment 1:

[0037] See also Figure 1 The explosive type dynamic tensile test device of the present invention comprises: a dynamic pressure generator 2, left and right clamps 4, a tension transmission system and a force application scheme monitoring, tension and deformation recording system;

[0038] The dynamic pressure generator 2 is a U-shaped structure placed on the side. A pressure sensor position point 6 is arranged above the dynamic pressure generator 2. A small opening is arranged on one side for loading gunpowder 1 into the groove. A T-shaped sliding block 9 is arranged at the groove opening on the other side. Two parallel force transmission rods 5 are vertically arranged at the top of the two ends of the T-shaped transverse end of the sliding block 9. The other end of the force transmission rod 5 is fixed on the U-shaped frame. The other ends of the two force transmission rods 5 are also fixed by a transverse force transmission rod 5. The left and right clamps 4 are vertically arranged at the midpoint of the transverse force transmission rod 5. The two clamps of the left and right clamps 4 are both T-shaped structures with the transverse ends facing each other. Among them, the vertical end of the right clamp is fixed at the midpoint of the transverse force transmission rod 5, and the vertical end of the left clamp is fixed inside the device. An acceleration sensor position point 8 is arranged at the vertical end of the right clamp, and a force sensor position point 7 is arranged at the vertical end of the left clamp. The tension transmission system, force application scheme monitoring, tension and deformation recording system are used for tension transmission and data monitoring at corresponding positions respectively.

[0039] Embodiment 2:

[0040] Reference Figure 1-2 , the explosive type dynamic tensile test method comprises the following steps:

[0041] S1: configure and test the dynamic pressure generator 2, left and right clamps 4, pressure sensors, force sensors, acceleration sensors, tension transmission system, and force scheme monitoring, tension and deformation recording system;

[0042] S2: Clamp the specimen 3 between the left and right clamps 4, ensure that the specimen 3 is aligned with the center of the left and right clamps 4, and that the specimen 3 is subjected to axial force;

[0043] S3: According to the loading rate required by the specimen 3, select the corresponding gunpowder 1 as the power source;

[0044] S4: The charge is ignited, and the test piece 3 is loaded and stretched through the force transmission rod 5, the sliding block 9 and the left and right clamps 4. The test piece 3 undergoes elastic, plastic and fracture changes in sequence at the corresponding deformation rate;

[0045] S5: The force application scheme monitoring, tension and deformation recording system records the mechanical parameter values ​​of the test process; the pressure sensor records the pressure-time variation curve of the dynamic pressure generator 2 when it is working, the force sensor records the force-time variation curve of the test piece 3 when it is tensilely deformed, and the acceleration sensor records the acceleration-time variation curve of the sliding block 9 moving together with the test piece 3;

[0046] S6: Obtain relevant data of specimen 3 through curve calibration and data processing; calculate the dynamic yield stress of the material based on the elastic-plastic modified theory and the elastic-plastic theory respectively;

[0047] Elastic-plastic improvement theory: Assuming that the material is a rigid body, stretching only causes plastic deformation of the material. In the case of actual high-speed deformation, the plastic deformation zone still has a certain radial velocity, and as the stretching velocity increases, the plastic deformation zone will also increase, and the energy consumed by radial deformation will also increase. At this time, the dynamic conservation law is no longer applicable, so Hawkyarol used the energy conservation equation on the plastic wave front to establish the relationship between the dynamic yield stress of the material:

[0048]

[0049] Among them, σ D is the yield stress value of the material under test; ρ is the density of the material under test; v0 is the tensile speed of the material under test; e0, is the axial engineering strain of the material under test corresponding to v0; n1 is the unit direction of plastic flow of the material under test;

[0050] The elastic-plastic theory uses the HEMP program to numerically simulate the stretching process, and on this basis, experimental research is carried out. According to the deceleration equation of the undeformed section of the projectile during the stretching process, through numerical simulation and theoretical analysis, under the assumption that the plastic wave front is exactly located at the rigid-incremental interface, the relationship between the dynamic yield stress of the material is established:

[0051]

[0052] Wherein, L1 is the length of the material after being stretched; L0 is the initial unstretched length of the material under test; and h is the length change of the material under test after stretching.

[0053] The dynamic properties of materials can also be measured by using laser interferometry micro-displacement measurement. Figure 2Before the experiment, two laser reflective plates with the same material and diameter as the rod are glued to the end face of the material to be tested with high-strength glue. The thickness of the laser reflective plate is 1mm, and the ear size R is equivalent to the size of the fiber optic probe. During the experiment, the material sample to be tested is installed between the two reflective ears, and the fiber optic probe in the laser interferometer micro-displacement measurement system is aligned with the center of the ear on the reflective plate. When the left and right end faces of the sample are respectively affected by the incident pulse and the transmitted pulse, the end face velocities v1(t) and v2(t) generated are measured in real time by the fiber optic probe through the reflective ears.

[0054] The dynamic mechanical properties of the tested material can be obtained by the following formula;

[0055]

[0056] Among them, σ * (t) is the dynamic yield stress at time t; E is the energy consumed by deformation; A0 is the initial cross-sectional area of ​​specimen 3; A S is the test cross-sectional area of ​​specimen 3; C0 is the system parameter constant; L S represents the tensile length of specimen 3; ε S (t) is the strain at time t; is the strain rate at time t;

[0057] S7: By adjusting the parameters of the gunpowder 1 and the installation posture of the specimen 3, the tensile properties of the specimen 3 at different loading rates are tested to obtain dynamic tensile curves at different strain rates.

[0058] Dynamic tensile tests were performed on copper and D60 steel. The specific test and calculation results can be found in Table 1-Table 2:

[0059] Table 1 Yield stress of copper at different elongation rates

[0060]

[0061]

[0062] Table 2 Yield stress of D60 steel at different tensile rates

[0063]

[0064] The yield stress of copper and D60 steel at different tensile instantaneous speeds can be obtained more accurately from the table.

[0065] Based on the above strategy, by selecting different gunpowders 1, the dynamic mechanical properties of the material under different loading rates can be obtained, which can correspond to the static tensile measurement and facilitate the analysis and comparison of the material.

[0066] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. Explosive powder type dynamic tensile testing device, characterized in that: include: A dynamic pressure generator (2) and left and right clamps (4); The dynamic pressure generator (2) is in a side-mounted U-shaped structure. A pressure sensor position point (6) is arranged above the dynamic pressure generator (2). A small opening is arranged on one side for loading gunpowder (1) into the groove. A T-shaped sliding block (9) is arranged at the groove opening on the other side. Two mutually parallel force transmission rods (5) are vertically arranged at the top of both ends of the T-shaped transverse end of the sliding block (9). The other end of the force transmission rod (5) is fixed on the U-shaped frame. The other ends of the two force transmission rods (5) are also fixed by a transverse force transmission rod (5). Left and right clamps (4) are vertically arranged at the midpoint of the transverse force transmission rod (5); the two clamps of the left and right clamps (4) are both in a T-shaped structure with the transverse ends arranged opposite to each other, wherein the vertical end of the right clamp is fixed at the midpoint of the transverse force transmission rod (5), and the vertical end of the left clamp is fixed inside the device.

2. The explosive type dynamic tensile testing device according to claim 1, characterized in that: An acceleration sensor position point (8) is arranged at the vertical end of the right clamp, and a force sensor position point (7) is arranged at the vertical end of the left clamp.

3. The explosive type dynamic tensile testing device according to claim 1, characterized in that: It also includes a tension transmission system, a force application scheme monitoring system, and a tension and deformation recording system, which are used for tension transmission and data monitoring at corresponding positions respectively.

4. The explosive type dynamic tensile test method according to any one of claims 1 to 3, characterized in that: The steps include: S1: configure and test the dynamic pressure generator (2), left and right clamps (4), pressure sensors, force sensors, acceleration sensors, tension transmission system, and force application scheme monitoring, tension and deformation recording system; S2: clamp the test piece (3) between the left and right clamps (4); S3: According to the loading rate required by the specimen (3), select the corresponding gunpowder (1) as the power source; S4: the charge is ignited, and the test piece (3) is loaded and stretched through the force transmission rod (5), the sliding block (9) and the left and right clamps (4). The test piece (3) undergoes elastic, plastic and fracture changes in sequence at corresponding deformation rates; S5: The force application scheme monitoring, tension and deformation recording system records the mechanical parameter values ​​of the test process; S6: Obtain relevant data of the specimen (3) through curve calibration and data processing; S7: By adjusting the parameters of the gunpowder (1) and the installation posture of the test piece (3), the tensile properties of the test piece (3) at different loading rates are tested to obtain dynamic tensile curves at different strain rates.

5. The explosive type dynamic tensile test method according to claim 4, characterized in that: In S2, the test piece (3) is aligned with the center of the left and right clamps (4) for clamping, and the test piece (3) is ensured to be subjected to axial force.

6. The explosive type dynamic tensile test method according to claim 4, characterized in that: In the above S5, the pressure sensor records the pressure-time variation curve of the dynamic pressure generator (2) when it is working, the force sensor records the force-time variation curve of the test piece (3) when it is tensilely deformed, and the acceleration sensor records the acceleration-time variation curve of the sliding block (9) moving together with the test piece (3).

7. The explosive type dynamic tensile test method according to claim 4, characterized in that: In S6, the dynamic yield stress of the material is calculated based on the elastic-plastic modified theory and the elastic-plastic theory respectively; The improved elastic-plastic theory uses the energy conservation equation on the plastic wave front to establish the relationship between the dynamic yield stress of the material: Among them, σ D is the yield stress value of the material under test; ρ is the density of the material under test; v0 is the tensile speed of the material under test; e0, is the axial engineering strain of the material under test corresponding to v0; n1 is the unit direction of plastic flow of the material under test; The elastic-plastic theory establishes the relationship between the dynamic yield stress of the material under the condition that the plastic wave front is exactly located at the rigid-incremental interface: Wherein, L1 is the length of the material after being stretched; L0 is the initial unstretched length of the material under test; and h is the length change of the material under test after stretching.

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