Explosion Specific Impulse Measurement Platform

Abstract

The present invention provides an explosion specific impulse measurement platform, which includes a top fixed end. Below the top fixed end, an impulse catcher is fixed by a suspension wire. Right below the impulse catcher, there is a sand bucket fixed on a base, and a quantitative explosive is buried in the sand bucket. A reflector and a calibration plate are respectively arranged in front of and behind the impulse catcher, and the calibration plate is fixed by a bracket. A high-speed camera is arranged obliquely in front of the impulse catcher. The center of the high-speed camera lens is at the same height as the upper end of the impulse catcher, and together with the reflector and the calibration plate, they form a reflection optical path. The platform provided by the present invention can measure the specific impulse distribution and specific impulse magnitude of soil explosion, carry out research on the influence of factors such as explosive shape, soil type, and target plate shape on impulse transfer, reveal the significant degree and variation law of the influence of each factor on impulse transfer, has a reasonable structure design, is simple to operate, has a low cost, and has good versatility.

Description

Technical Field

[0001] The present invention relates to the field of military vehicle protective armor design, belonging to the direction of impact dynamics. Specifically, it is a measurement platform for the specific impulse distribution of shallow-buried high-energy explosive explosions. Background Art

[0002] In modern asymmetric warfare, landmines, improvised explosive devices (IEDs), and roadside bombs, as effective anti-maneuver weapons, play a significant role in blocking and damaging armored vehicles and even unarmored vehicles (such as logistics transport vehicles). Especially for shallow-buried high-energy explosives, the shock waves and ejecta generated by their explosive energy concentration will cause devastating blows to the armor, structure, mobility of motor vehicles, and vehicle occupants. Even if the vehicle body structure remains intact, the momentum transmitted to the vehicle under the combined action of the explosion pressure and ejected soil may still endanger the lives of the occupants. For example, a large overall acceleration can cause damage to the brain and spine, while lower limb injuries result from local accelerations caused by deformation at the bottom of the vehicle. To address such threats, it is necessary to design a shallow-buried explosive explosion simulation experiment by taking the quantitative analysis of the impulse load borne by the protective design structure as the starting point, and conduct research on the detonation process of high-energy explosives and their damage mechanisms, so as to design armor and structures with better protective effects.

[0003] Shallow-buried soil explosion experiments have the characteristics of short action time and extremely high load intensity. At the same time, due to the interference of soil ejection on conventional optical measuring instruments, directly measuring the distribution law of the load caused by the explosion in time and space is a research hotspot among scholars in various countries. Westine et al. used a "pulse piston" technique to measure the impulse received at each point on the target plate. In this method, a series of holes were pre-drilled at different positions on the target plate, and then small and rigid plugs were inserted into the holes. By measuring the velocity of each plug during the explosion, the impulse received at each point on the plate was obtained. Held et al. designed a new experimental platform. By placing detection steel blocks along the center line on the upper surface of the target plate, the take-off velocity of the detection steel blocks was calculated using high-speed photography to obtain the distribution of specific impulse on the target plate. Rigby et al. measured the spatial impulse distribution of the plate at different explosion distances through 17 Hopkinson bars and a high-speed photography device. The measured pressure-time history and impulse-time history curves can be used to verify the effectiveness of numerical simulation calculations.

[0004] However, most of the current research on the impulse generated by shallow-buried explosive explosions focuses on flat target plates, and columnar or disk-shaped explosives are mostly used for testing. There are also no reports on the influence of different explosive shapes on the impulse transfer of curved target plates. Designing and developing a platform that can be used for the impulse distribution of curved target materials can effectively fill the gap in such research. Summary of the Invention

[0005] In order to solve the problems of the prior art, the present invention provides an explosion specific impulse measurement platform, which can measure the specific impulse distribution and magnitude of soil explosion. At the same time, this platform can measure the specific impulse obtained by different bottom surface shape structures (such as plane, conical surface, arc surface, hemispherical surface, etc.). Using this experimental platform, research work on the influence of factors such as explosive shape (round cake shape, cylindrical shape, etc.), soil type (sand, gravel, clay, etc.), and target plate shape on impulse transfer can be carried out, revealing the significant degree and variation law of the influence of each factor on impulse transfer.

[0006] The present invention includes a top fixed end, and an impulse catcher is fixed below the top fixed end by a suspension wire; a sand bucket fixed on a base is arranged directly below the impulse catcher, and a quantitative explosive is buried in the sand bucket; a reflector and a calibration plate are respectively arranged in front of and behind the impulse catcher, and the calibration plate is fixed by a bracket; a high-speed camera is arranged obliquely in front of the impulse catcher, and the center of the high-speed camera lens is at the same height as the impulse catcher, and together with the reflector and the calibration plate, they form a reflection optical path.

[0007] Further improvement, the bottom of the impulse catcher is a curved surface structure with good load-bearing capacity, including conical, arc-shaped, and hemispherical shapes.

[0008] Further improvement, the impulse catcher is composed of a plurality of concentric rings and a central cylinder, and hooks are arranged on the upper surface of each concentric ring; each ring is concentric, and there are gaps between the concentric rings and the cylinder. The upper surface heights of each ring decrease successively from the inside to the outside to realize the observation of each concentric ring and the cylinder, avoiding the shielding effect of the inner ring when the outer ring is vertically projected upward by the explosion shock, so that it is difficult for the high-speed camera to capture the motion characteristics of the inner ring.

[0009] Further improvement, lubricating oil is applied to the gaps between the concentric rings of the impulse catcher and between the concentric rings and the cylinder to reduce the friction coefficient between each component.

[0010] Further improvement, the impulse catcher is made of a material with high strength and good impact resistance, such as 45 steel or 40Cr steel.

[0011] Further improvement, the suspension wire uses a light and good load-bearing steel wire rope, and the gap between the bottom of the impulse catcher and the upper surface of the sand bucket is adjusted by adjusting the length of the suspension wire.

[0012] Further improvement, the reflection optical path composed of the high-speed camera, the reflector, and the calibration plate is used to indirectly observe the position of the impulse catcher. The reflector is placed at a certain reflection angle, and the reflection angle can be set to 20° - 70°.

[0013] For further improvement, the rearview mirror is a coated optical flat mirror with a reflectivity of more than 95% in the visible light band.

[0014] After the shallowly buried explosive in the sand bucket is detonated, it will cause the extrusion and ejection of the surrounding sand. The ejecta generates an impact load on the bottom of the impulse catcher, causing a certain vertically upward initial velocity of each concentric ring and the central cylinder. The initial velocity can be measured by a high-speed camera and a calibration plate. Given the bottom area and mass of each ring, the specific impulse of each ring and the central cylinder can be obtained, and the annular distribution of the specific impulse of the explosive impact load can be obtained.

[0015] The beneficial effects of the present invention are as follows:

[0016] 1. The present invention provides a set of underground shallowly buried explosive explosion simulation devices, which are used to measure the impact load distribution of sand ejecta on the target plate and solve the structural design problems of curved target plates with different shapes. The structure is simple and reasonable. Through the impulse catcher, the annular distribution of the impulse of the explosive impact load can be directly obtained, with high accuracy.

[0017] 2. The device of the present invention uses a mirror to transmit the optical path, has strong anti-explosion interference ability, and has a certain protective effect on structures such as high-speed cameras.

[0018] 3. The present invention can be used to simulate and measure the specific impulse distribution of curved target plates (such as conical, circular arc, hemispherical), and has good experimental guiding significance for the design of new protection structures.

[0019] 4. The device of the present invention has strong versatility and can simulate the influence of shallowly buried explosive explosion impact on curved target plates under different soil types and explosive shapes.

[0020] 5. The present invention adopts an appropriate ratio to conduct experiments on a laboratory scale, effectively reducing the experimental cost and improving the experimental safety while ensuring the experimental accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the test platform of the present invention, which is an isometric view.

[0022] Figure 2 It is the front view and top view of the impulse catcher structure.

[0023] Figure 3 It is the front view and top view of the bottom structure of the optional impulse catcher. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be further described below with reference to the accompanying drawings.

[0025] The structure of the present invention is as shown in Figure 1As shown in the figure, it includes a suspension wire 1, an impulse catcher 2, concentric rings 2-1, a hook 2-2, a mirror 4, a base 5, a high-speed camera 6, a bracket 7, a calibration plate 8, and a top fixed end 9.

[0026] The impulse catcher 2 is fixed on the top fixed end 9 by the suspension wire 1. The suspension wire 1 is made of a light and high-load-bearing steel wire rope. The sand bucket 3 is located directly below the impulse catcher 2 and is placed on the base 5 to ensure that the impulse catcher 2 is only subjected to a vertically upward impact load, and the circumferential impact load is basically cancelled out. The mirror 4 is located Figure 1 in front of the impulse catcher 2 in the isometric view. The mirror surface forms a certain angle with the front, and the design range is between 20° and 70° to ensure the reflection effect. The lens center of the high-speed camera 6 and the lowest point on the upper surface of the impulse catcher 2 are at the same height at the initial moment, and a coaxial optical path is formed by the mirror 4 (indicated by a dotted line in Figure 1 ). The calibration plate 8 is fixed on the bracket 7 and is located Figure 1 behind the impulse catcher 2 in the isometric view, and can calibrate the rising height of each concentric ring 2-1 of the impulse catcher 2.

[0027] The concentric ring structure 2-1 (including 1 central cylinder) and the hook 2-2 together form the impulse catcher 2, and its material can be selected from materials with good strength and impact resistance such as 45 steel or 40Cr steel. As Figure 2 shown in the figure, the impulse catcher 2 in the figure contains 7 concentric rings and 1 central cylinder. In the actual design process, the number of concentric rings can be increased or decreased considering the manufacturing cost and the required circumferential accuracy of the impulse distribution. There is a certain gap between each ring and between the ring and the cylinder, which is designed to be 0.2 mm and is coated with lubricating oil to achieve relative slippage between the two components. The upper surface heights of the rings decrease sequentially from the inside to the outside, showing a stepped nesting, so that the high-speed camera 6 can capture the initial motion characteristics of all the rings and the cylinder.

[0028] As a further improvement to the above embodiment, the bottom structure of the impulse catcher 2 is as Figure 2 shown in the figure, which is a conical curved surface configuration. This configuration can effectively reduce the impulse transmitted by the shock wave and soil ejecta generated by the explosive to the target, and achieve a good protection effect. Figure 2 The taper of the conical surface in the figure is 1:8. To achieve a better protection structure design, the taper of the cone can be adjusted.

[0029] In some embodiments, the bottom of the impulse catcher 2 can also adopt other curved surface configurations with good load-bearing capacity, such as arc-shaped, hemispherical, etc. Figure 3The impulse catcher with an arc-shaped bottom has a central angle of 60°, and the degree of the central angle can also be adjusted to achieve a better protective structure design.

[0030] Furthermore, there is still a certain gap between the upper surface of the sand bucket 3 and the bottom of the impulse catcher 2. The size of the gap can be adjusted by adjusting the length of the suspension line 1 or the height of the top fixed end 9. The sand and explosive types in the bucket can also be replaced with various types according to the required actual simulated soil environment, and the burial depth of the explosive can also be adjusted to meet different experimental requirements.

[0031] The specific working process is as follows: After the explosive in the sand bucket 3 is detonated, the soil above and around it is ejected. After the explosion shock wave and the ejecta collide with the bottom of the impulse catcher 2, part of the impulse is transmitted to the impulse catcher 2 and makes it generate an initial upward velocity. This impulse transmission process is extremely short, about 2 milliseconds. The initial upward velocities of each concentric ring 2-1 of the impulse catcher 2 are determined by shooting the relative displacements presented by each concentric ring 2-1 on the calibration plate 8 through the high-speed camera 6. Due to the interference of the flame and sand generated by the explosion at the initial moment, the initial velocities of each concentric ring 2-1 are calculated by measuring the total time from the upward throw to the fall back to the initial height. The calculation formula is as follows:

[0032]

[0033] In formula (1), v0 is the initial upward velocity of the ring, and t f is the total time from the upward throw to the fall back of the ring. It should be noted that since the timer of the high-speed camera 6 and the explosive are triggered simultaneously, the t here f is the remaining time after subtracting the impulse transmission time of 2 milliseconds. g is the acceleration due to gravity, and here the constant g = 9.81 m / s is taken.

[0034] The specific impulse of the corresponding ring can be obtained from (1), and the calculation formula is as follows:

[0035]

[0036] In formula (2), i s is the specific impulse of the concentric ring 2-1 in space, and its unit is kg·m -1 ·s -1 , the direction is vertically upward, m is the mass of the ring, v0 is the initial upward velocity of the ring, and S is the upper surface area of the ring.

[0037] By solving the specific impulse of each concentric ring 2-1, the radial specific impulse distribution at the bottom of the impulse catcher 2 can be obtained. Using this explosion specific impulse distribution measurement platform, systematic experimental studies can be carried out on the shape of the bottom target plate, the shape of the explosive, and the type of soil, and a better evaluation of the protection performance of the target plate can be achieved. In addition, through the high-speed camera 6, the formation process of the blasting funnel and the movement trajectory of the sandy soil during the explosion process can be obtained, which has good reference value for understanding the interaction mechanism between the sandy soil and the target plate.

[0038] There are many specific application ways of the present invention. The above description is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements can be made, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. An explosion specific impulse measurement platform, characterized in that: It includes a top fixed end. An impulse catcher is fixed below the top fixed end by a suspension wire. The bottom of the impulse catcher is a curved surface structure. The impulse catcher is composed of multiple concentric rings and a central cylinder. Hooks are arranged on the upper surface of each concentric ring; each ring is concentric, and there are gaps between the concentric rings and the cylinder. The upper surface heights of the rings decrease successively from the inside to the outside; a sand bucket fixed on a base is arranged directly below the impulse catcher, and a fixed amount of explosive is buried in the sand bucket; a reflector and a calibration plate are respectively arranged in front of and behind the impulse catcher. The calibration plate is fixed by a bracket; a high-speed camera is arranged obliquely in front of the impulse catcher. The center of the high-speed camera lens is at the same height as the impulse catcher, and together with the reflector and the calibration plate, they form a reflection optical path.

2. The explosion specific impulse measurement platform according to claim 1, characterized in that: Lubricating oil is coated in the gaps between the concentric rings of the impulse catcher and between the concentric rings and the cylinder.

3. The explosion specific impulse measurement platform according to claim 1, characterized in that: The impulse catcher is made of 45 steel or 40Cr steel.

4. The explosion specific impulse measurement platform according to claim 1, characterized in that: The suspension wire uses a steel wire rope, and the gap between the bottom of the impulse catcher and the upper surface of the sand bucket is adjusted by adjusting the length of the suspension wire.

5. The explosion specific impulse measurement platform according to claim 1, characterized in that: In the reflection optical path jointly formed by the high-speed camera, the impulse catcher, the reflector, and the calibration plate, the reflector is placed at a certain reflection angle, and the reflection angle is 20° to 70°.

6. The explosion specific impulse measurement platform according to claim 1, characterized in that: The reflector selected is a coated optical flat mirror with a reflectivity of more than 95% in the visible light band.

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