Hopkinson bar test piece bracket protection box device

Abstract

The invention discloses a Hopkinson bar test piece bracket protection box device, and belongs to the technical field of Hopkinson bar dynamic compression test devices. The device comprises a protection box chamber, an acrylic plate, a through hole, a base plate, a bottom support and a bracket. The acrylic plate can be embedded through grooves in the two sides of the protection box to enable a protection box chamber to form a closed space, the bracket can support a concrete test piece, the base plates, the bottom support and the bracket are all made of steel, the two base plates are welded to the inner walls of the two sides of the protection box respectively, the bottom support is welded to the middle of the two base plates, and the bracket is welded to the middle of the bottom support. According to the invention, the test piece is stably supported and fixed in the Hopkinson bar dynamic compression test.

Description

Technical Field

[0001] The invention relates to a Hopkinson bar test piece bracket protection box device, and belongs to the technical field of Hopkinson bar dynamic compression test devices. Background Art

[0002] As an excellent building material, concrete is widely used in military and civilian construction due to its excellent performance. When buildings are targeted for attack, how to effectively play a protective role is a research focus in the field of engineering protection. Protection projects are mainly subjected to dynamic loads such as projectile attack and high-speed impact. The mechanical properties of concrete under dynamic loads are very different from those of static loads. Research on the performance of concrete under dynamic impact loads has important guiding significance for the design and protection of various buildings and their fortifications. One of the most widely used and reliable impact loading methods is the split Hopkinson bar device.

[0003] In recent years, people have used the Hopkinson bar device to conduct dynamic compression tests on relevant concrete. In the test, the specimen is fixed in the middle of the Hopkinson bar by applying vaseline or molybdenum disulfide grease on both ends of the specimen. However, sometimes the specimen often falls off between the two bars, and it takes time and effort to re-place the specimen. For this reason, the present invention has developed a Hopkinson bar specimen bracket protection box device. Summary of the invention

[0004] The purpose of the present invention is to provide a Hopkinson bar specimen bracket protection box device to solve the problem in the prior art that the specimen often falls off between the two bars in the Hopkinson bar dynamic compression test. The method is simple and feasible, and there is no difficulty in operation.

[0005] To achieve the above purpose, the present invention adopts the following steps to achieve:

[0006] Step 1: Prepare the Hopkinson bar device used in the experiment, including the bullet, incident bar and transmission bar, and measure the length of each part;

[0007] Step 2: Install the protective box, place the concrete specimen between the incident rod and the transmission rod, and adjust the specimen position so that the bracket is just at the bottom of the specimen. Then start the Hopkinson bar device to perform a dynamic compression test. The process of specimen compression and fragment collection is completed in the protective box.

[0008] Step 3: Screen the specimen fragments, and the sieve plate sizes are 0.625mm, 1.25mm, 2.5mm, 5mm, 10mm and 20mm.

[0009] Step 4: Weigh the mass of the fragments of each sieve size, record their particle size distribution and draw their screening curve to analyze the crack resistance of concrete materials under dynamic loads.

[0010] In the step 1, the lengths of the bullet, the incident rod and the transmission rod are 1000 mm, 5500 mm and 3500 mm respectively;

[0011] In step 2, the loading drive device in the dynamic compression test is composed of compressed nitrogen and an air pressure control system, and the speed of the bullet hitting the incident rod is changed by adjusting the value of the air pressure. The specimen is fixed between the incident rod and the transmission rod with molybdenum disulfide grease, and the position of the specimen is adjusted so that the bracket is just located at the bottom of the specimen. The dynamic compression test contains three waveforms, namely, the incident wave generated by the collision of the shock wave with the incident rod, the reflected wave generated in the incident rod, and the transmitted wave propagating in the transmission rod;

[0012] The concrete specimens used in the test were normal concrete (NC) and rubber concrete (RC);

[0013] The rubber in the rubber concrete replaces the sand in the concrete at an equal volume replacement rate of 10%.

[0014] Compared with the background technology, the present invention has the following effects:

[0015] The present invention adopts the above-mentioned solution, which is simple and feasible, has no difficulty in operation, effectively avoids the situation that the test piece falls off between the incident rod and the transmission rod, and saves test time cost and energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a Hopkinson bar specimen bracket protection box device provided by an embodiment of the present invention;

[0017] Figure 2 It is a front cross-sectional schematic diagram of a Hopkinson bar specimen bracket protection box device provided by an embodiment of the present invention;

[0018] Figure 3 It is a top cross-sectional schematic diagram of a Hopkinson bar specimen bracket protection box device provided by an embodiment of the present invention;

[0019] Figure 4 is a schematic diagram of a Hopkinson bar device provided by an embodiment of the present invention;

[0020] Figure 5 is a screening curve diagram of ordinary concrete and rubber concrete provided by an embodiment of the present invention; DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be understood as limiting.

[0022] like Figure 1As shown, the Hopkinson rod funnel-shaped protection box device provided by the embodiment of the present invention includes a through hole 1, a cushion block 2, a bracket 3, a bottom bracket 4 and an acrylic plate 5.

[0023] like Figure 4 As shown, the Hopkinson bar device used in the embodiment of the present invention is composed of a bullet 6, an incident rod 7, a strain gauge 8 on the incident rod, a test piece 9, a transmission rod 10, a strain gauge 11 on the transmission rod and an absorption rod 12.

[0024] Embodiment 1: Before the test, the lengths of the bullet 6, the incident rod 7 and the transmission rod 10 were measured, which were 1000 mm, 5500 mm and 3500 mm respectively.

[0025] The incident rod 7 and the transmission rod 10 are respectively inserted into the protection box through the two through holes 1 on the protection box, and the test piece 9 is fixed between the incident rod 7 and the transmission rod 10 with molybdenum disulfide grease, and the position of the test piece 9 is adjusted so that the bracket 3 is just located at the bottom of the test piece 9. Then the acrylic plate 5 is embedded through the groove on the protection box to form a closed space inside the protection box.

[0026] By adjusting the value of the air pressure to change the speed at which the bullet 6 hits the incident rod 7, the bullet 6 generates an incident stress wave in the incident rod 7 after hitting the incident rod, and the stress wave is recorded by the strain gauge 8 on the incident rod; then the incident rod 7 compresses the specimen 9, and a part of the incident stress wave is transmitted to the transmission rod 10 through the specimen, and is recorded by the strain gauge 11 on the transmission rod, i.e., the transmission stress wave; the other part of the stress wave is reflected along the original path of the incident rod 7, and is again recorded by the strain gauge 8 on the incident rod, i.e., the reflected stress wave. The stress wave in the transmission rod 10 will eventually be absorbed by the absorption rod 12 by the way that the transmission rod 10 hits the absorption rod 12.

[0027] The compression and collection process of the specimen 9 is completed inside the protective box. After the specimen 9 is impacted and broken, fragments are formed. After the test, the acrylic plate 5 is pulled out and the fragments are collected by a tray for sieving and analysis. The sizes of the sieve trays are 0.625 mm, 1.25 mm, 2.5 mm, 5 mm, 10 mm and 20 mm. This operation is repeated for each concrete specimen.

[0028] The mass of the fragments of each screen size was weighed, and the particle size distribution was recorded and plotted for various concretes at similar strain rates (strain rate of about 135s -1 ) screening curve, such as Figure 5 As shown in the figure, it can be seen that no matter which screening size is used, the screening rate of ordinary concrete is greater than that of rubber concrete, which shows that the overall fragment size of ordinary concrete is the smallest. In other words, rubber particles inhibit the generation and expansion of cracks in concrete materials when they are loaded to a certain extent, and improve the crack resistance of concrete.

[0029] The embodiments are only a part of the invention and are only used to demonstrate the use of the method and its improvements. For technicians engaged in this field, they can make appropriate improvements to the patent within the scope of protection of the invention without departing from the method of the patent.

Claims

1. A Hopkinson bar specimen bracket protection box device, characterized in that: The device includes a protective box chamber, an acrylic plate, a through hole, a pad, a bottom bracket and a bracket. The acrylic plate can be embedded through the grooves on both sides of the protective box to form a closed space in the protective box chamber, and the bracket can support the concrete specimen. The pad, the bottom bracket and the bracket are all customized with steel. There are two pads, which are welded on the inner walls of both sides of the protective box respectively, the bottom bracket is welded between the two pads, and the bracket is welded in the middle of the bottom bracket.

2. The Hopkinson bar specimen bracket protection box device according to claim 1, characterized in that: Grooves are arranged on the inner walls on both sides of the protection box, and the acrylic plate is pushed in or pulled out through the vertical grooves on the inner walls on both sides, and the acrylic plate is slightly higher than the protection box.

3. The Hopkinson bar specimen bracket protection box device according to claim 1, characterized in that: The pad, base and bracket are all customized with steel. There are two pads, which are welded on the inner walls on both sides of the protective box. They are cubes with a width of 100 mm and a thickness of 10 mm.

4. The Hopkinson bar specimen bracket protection box device according to claim 1, characterized in that: The bottom support is welded to connect two pads, 80mm wide and 10mm thick.

5. The Hopkinson bar specimen bracket protection box device according to claim 1, characterized in that: The bracket is welded in the middle part of the base, with a height of 130mm, a width of 60mm and a thickness of 10mm.

6. The Hopkinson bar specimen bracket protection box device according to claim 1, characterized in that: The height of the bracket is just level with the bottom surface of the Hopkinson bar and can support and fix the specimen.

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