Hopkinson bar funnel-shaped protection box device

Abstract

The invention discloses a funnel-shaped protection box device for a Hopkinson bar, and belongs to the technical field of dynamic compression test devices for Hopkinson bars. The device comprises a protection box chamber, an acrylic plate, a funnel-shaped collection box, a first pipeline and a second pipeline. The acrylic plates 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 funnel-shaped collecting box and the pipelines are connected in a welded mode, the funnel-shaped collecting box is also embedded through the grooves in the protection box, the first pipeline and the second pipeline are customized through steel, the first pipeline is steep in gradient, and the second pipeline is steep in gradient. And the second pipeline is relatively smooth. According to the invention, the fragments of the test piece can be rapidly and safely collected in real time in the dynamic compression test of the Hopkinson bar.

Description

Technical Field

[0001] The invention relates to a Hopkinson bar funnel-shaped protection box device, belonging to the technical field of a Hopkinson bar dynamic compression test device. 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 mainly bear dynamic loads such as projectile invasion and high-speed impact. The mechanical properties of concrete under dynamic loads are very different from static mechanical properties. Research on the performance of concrete under dynamic impact loads has important guiding significance for the design and protection of various types of buildings and their fortifications. Currently, one of the most widely used and reliable impact loading methods is the separated Hopkinson bar device. However, the existing Hopkinson bar protection box still has defects in the collection of fragments, and there are omissions or safety issues in the collection of fragments of the damaged specimens. Therefore, it is very necessary to design and manufacture a Hopkinson bar funnel-shaped protection box device.

[0003] In recent years, people have used the Hopkinson bar device to conduct dynamic compression tests on related concrete, so the function of the protection box has gradually been valued and improved. Patent CN201720436707.6 designs a fragment collection box to collect concrete sample fragments after the compression test, but when pulling out the device after the experiment, it is still necessary to grab the outer side of the device by hand and pull it out. If there are sharp small gravel falling on the edge surface, it may still cause safety problems for the experimenter. Patent CN202223012388.6 designs a direct-impact Hopkinson bar protection device. The test process is enclosed in a rectangular frame, which is convenient for recovering the sample and effectively solves the problem of fragment splashing during the test. However, the design does not involve the fragment collection part, and it is possible that some fragments are missed when it collects the specimen fragments, which affects the experimental results. To this end, the present invention has developed a Hopkinson bar funnel-shaped protection box device. Summary of the invention

[0004] The purpose of the present invention is to provide a Hopkinson bar funnel-shaped protection box device to solve the problems of omission and potential safety hazards in the collection of specimen fragments in the Hopkinson bar dynamic compression test in the prior art. 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 then start the Hopkinson bar device to perform a dynamic compression experiment. The process of specimen compression destruction and fragment collection is completed in the protective box.

[0008] Step 3: Place the sieve plate at the outlet of the second pipe to sieve the specimen fragments. 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 at which the bullet hits 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. The dynamic compression test includes three waveforms, namely, the incident compression pulse generated by the collision of the shock wave with the incident rod, the reflected tensile pulse generated in the incident rod, and the transmission wave propagating in the transmission rod. During the test, a high-speed camera is used to observe and capture images of the destruction process of the concrete specimen;

[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 scheme, which is simple and feasible, without any difficulty in operation. The method of collecting fragments is faster and safer than the traditional manual collection method, effectively reduces the omission of fragments, and minimizes the impact of experimental errors. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0017] Figure 2 is a schematic structural diagram of a Hopkinson bar device provided by an embodiment of the present invention;

[0018] Figure 3 is a screening curve diagram of ordinary concrete and rubber concrete provided by an embodiment of the present invention; DETAILED DESCRIPTION

[0019] 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.

[0020] like Figure 1 As shown, the Hopkinson rod funnel-shaped protection box device provided by the embodiment of the present invention includes an acrylic plate 1, a funnel-shaped collecting box 2, a first pipe 3 and a second pipe 4.

[0021] like Figure 2 As shown, the Hopkinson bar device used in the embodiment of the present invention is composed of a bullet 5, an incident rod 6, a strain gauge 7 on the incident rod, a test piece 8, a transmission rod 9, a strain gauge 10 on the transmission rod and an absorption rod 11.

[0022] Embodiment 1: Before the test, the lengths of the bullet 5, the incident rod 6 and the transmission rod 9 were measured, which were 1000 mm, 5500 mm and 3500 mm respectively.

[0023] The incident rod 6 and the transmission rod 9 are respectively inserted into the interior of the protection box through two small holes on the protection box, and the test piece 8 is fixed between the incident rod 6 and the transmission rod 9 with molybdenum disulfide grease. Then the acrylic plate 1 is embedded through the groove on the protection box, and the funnel-shaped collecting box 2 is embedded through the groove below, so that a closed space is formed inside the protection box.

[0024] By adjusting the value of the air pressure to change the speed at which the bullet 5 hits the incident rod 6, the bullet 5 generates an incident stress wave in the incident rod 6 after hitting the incident rod, and the stress wave is recorded by the strain gauge 7 on the incident rod; then the incident rod 6 compresses the specimen 8, and a part of the incident stress wave is transmitted to the transmission rod 9 through the specimen, and is recorded by the strain gauge 10 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 6, and is again recorded by the strain gauge 7 on the incident rod, i.e., the reflected stress wave. The stress wave in the transmission rod 9 will eventually be absorbed by the absorption rod 11 by the way that the transmission rod 9 hits the absorption rod 11.

[0025] The compression and collection process of the specimen 8 are completed inside the protective box. After the specimen 8 is impacted and damaged, the fragments fall into the funnel-shaped collection box 2. Due to the funnel shape of the funnel-shaped collection box 2, the fragments enter the pipeline along the funnel mouth. The slope of the second pipeline 4 is gentler than that of the first pipeline 3, so that the fragments can slide slowly in the pipeline, and there will be no sudden splashing of fragments to injure people. Finally, the fragments are collected at the pipeline outlet by using a sieve plate for screening and analysis. The sizes of the sieve plates are 0.625mm, 1.25mm, 2.5mm, 5mm, 10mm and 20mm respectively. This operation is repeated for each concrete specimen.

[0026] 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 3 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.

[0027] 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. Hopkinson rod funnel-shaped protection box device, characterized in that: The device includes a protective box, an acrylic plate, a funnel-shaped collecting box, a first pipeline and a second pipeline. The acrylic plate can be embedded in the grooves on both sides of the protective box to form a closed space in the protective box. The funnel-shaped collecting box and the pipeline are connected by welding. The funnel-shaped collecting box is also embedded in the groove on the protective box. The first pipeline and the second pipeline are both customized with steel. The first pipeline has a steeper slope, while the second pipeline has a gentler slope.

2. The Hopkinson rod funnel-shaped protection box device according to claim 1, characterized in that: There are grooves on both sides of the steel plates directly in front and below the protective box. The acrylic plate is pushed in or pulled out through the vertical grooves on the steel plates on both sides, and the acrylic plate is slightly higher than the protective box.

3. The Hopkinson rod funnel-shaped protection box device according to claim 1, characterized in that: The funnel-shaped collection box is custom-made of steel, pushed in or pulled out through a groove, and has a 150mm wide square pipe opening at the connection with the pipeline.

4. The Hopkinson rod funnel-shaped protection box device according to claim 1, characterized in that: The first pipe and the second pipe are both custom-made steel and are both 150mm wide square pipes.

5. The Hopkinson rod funnel-shaped protection box device according to claim 1, characterized in that: The first pipe is connected to the funnel-shaped collecting box, and the first pipe extends out at an angle of 60 degrees to the horizontal line, with a length of 30 cm.

6. The Hopkinson rod funnel-shaped protection box device according to claim 1, characterized in that: The second pipe is connected to the first pipe, extends out at 150 degrees from the first pipe, and has a length of 40 cm.

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