Annular sample expansion loading method based on instantaneous spalling

Abstract

The invention discloses an annular sample expansion loading method based on instantaneous spalling, and relates to the technical field of deformation and fracture characteristic measurement of materials under dynamic loading. A loading system adopted by the method comprises a test frame, an instantaneous spalling air cylinder device, an inflatable airbag body, a detonating device, an annular sample and spalling agents, the spalling agents comprise rice hulls / coal gangue and combustion improvers, the spalling agents are arranged in a first air cylinder body and a second air cylinder body, and the spalling agents are connected with the detonating device. The loading method comprises the following steps: inflating the air bag main body, and stopping inflating when the pressure of the air bag main body reaches 240-250kPa; the detonating device is started, the spalling agent is excited by current and is converted into gas from solid in a short time, pressure is generated to drive the air bag body to expand, and then the annular sample is loaded. According to the invention, experimental errors caused by too high temperature rise of the sample and stress wave effect are avoided, and a more accurate loading effect is realized.

Description

Technical Field

[0001] The invention relates to the technical field of deformation and fracture characteristic measurement of materials under dynamic loading, and in particular to an annular sample expansion loading method based on instantaneous expansion and cracking. Background Art

[0002] The deformation and fracture characteristics of materials under dynamic loading have important research value in the fields of industry, military, and national defense. Among them, the expansion ring experimental technology, as an important means to study the dynamic tensile properties and fracture behavior of materials, has attracted much attention because it can achieve uniform one-dimensional tensile stress. At present, explosive expansion rings and electromagnetic expansion rings are the most widely used technologies. Many scholars have used these two technologies to study the dynamic mechanism under quasi-one-dimensional stress state, but both have certain technical limitations.

[0003] The explosive expansion ring experimental device detonates the central charge and uses the pressure of the explosion product to drive the sample ring to expand at a high speed. During the expansion process, stress wave reflection and tensile unloading wave cause the sample ring to enter the free expansion stage. The advantages of this method include: small sample size restrictions; high strain rate can be achieved; the temperature rise of the ring during loading is not significant. However, this method also has obvious disadvantages: shock waves, rarefaction waves and lateral effects are inevitably generated during loading, making it difficult to fully achieve a one-dimensional tensile stress state; the impedance of the driver and the sample ring material does not match, affecting the stability of the experimental results; the device processing and operation requirements are high, and the experimental safety is low.

[0004] The electromagnetic expansion ring experimental device uses a solenoid to generate a strong magnetic field and drives the sample ring to expand through the Lorentz force. The advantages of this method are: the Lorentz force acts evenly on the sample ring, avoiding the wave effect caused by mechanical loading; the expansion speed and strain rate of the sample ring can be accurately controlled by adjusting the circuit parameters; and it is simpler to measure the flow stress, plastic strain and strain rate history. However, the electromagnetic expansion ring also has shortcomings: the loading strain rate is low and the size of the sample ring is limited; the high current causes a significant temperature rise in the sample ring, affecting the accuracy of the dynamic performance test.

[0005] This shows that the prior art needs to be further improved. Summary of the invention

[0006] The purpose of the present invention is to provide an annular specimen expansion loading method based on instantaneous bursting, which avoids excessive temperature rise of the specimen and experimental errors caused by stress wave effects and achieves a more accurate loading effect.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a method for expanding and loading an annular specimen based on instantaneous bursting, wherein the loading system adopted by the method comprises a test frame, an instantaneous bursting cylinder device, an inflatable airbag, an initiating device, an annular specimen and an expansion agent, wherein the instantaneous bursting cylinder device is located in the test frame; the instantaneous bursting cylinder device comprises a cylinder body, a first cylinder plug and a second cylinder plug, wherein the cylinder body is divided into two parts, namely a first cylinder body located at the top and a second cylinder body located at the bottom, wherein the first cylinder body and the second cylinder plug are connected to each other. Two limit plates extending outward are arranged at opposite positions of the cylinder body; the first cylinder plug and the second cylinder plug are respectively installed on the first cylinder body and the second cylinder body, and the inflatable airbag body is arranged in the internal cavity of the cylinder body. The inflatable airbag body includes an airbag body, and outward protrusions are arranged on both sides of the airbag body. The two protrusions are symmetrical with respect to the central axis of the airbag body. When gas is injected into the airbag body, the protrusions on both sides are just located in the two limit plates, and the annular sample is tightly mounted on the two protrusions.

[0008] The expansion and cracking agent comprises rice husk / coal gangue and combustion aid, and the expansion and cracking agent is arranged in the first cylinder body and the second cylinder body, and the expansion and cracking agent is connected with the detonating device.

[0009] The loading method comprises the following steps: Step 1, inflating the airbag body to stop inflation when the pressure reaches 240-250 kPa.

[0010] Step 2: Turn on the detonator, the bursting agent is excited by electric current, and changes from solid to gas in 0.05 to 0.5 seconds, and generates pressure to drive the airbag body to expand, thereby loading the annular sample.

[0011] Step 3: Use formula (1) to calculate the annular stress of the annular specimen.

[0012] (1).

[0013] In formula (1): is the hoop stress of the annular specimen; is the cross-sectional area of ​​the annular specimen; is the height of the airbag body; F is the axial positive pressure of the cylinder body; It is the projected area of ​​the combination of the annular specimen and the airbag body where the axial force acts; is the cross-sectional area of ​​the airbag body; is the hoop stress of the airbag body; For strain.

[0014] The above-mentioned method of expansion loading of annular specimen based on instantaneous cracking, formula (1) is derived from formulas (2), (3) and (4): (2).

[0015] (3).

[0016] (4).

[0017] In formula (2): is the hoop stress of the annular specimen; is the cross-sectional area of ​​the annular specimen; is the contact surface pressure between the airbag body and the annular specimen; is the height of the ring specimen.

[0018] In formula (3): is the hoop stress of the airbag body; is the cross-sectional area of ​​the airbag body; is the contact surface pressure between the airbag body and the annular specimen; is the height of the annular specimen; is the gas pressure in the cylinder body; is the height of the airbag body.

[0019] In formula (4): is the hoop stress of the airbag body; For strain.

[0020] In the above-mentioned method for expanding and loading an annular specimen based on instantaneous bursting, an inflation valve is arranged on the airbag body, the inflation valve is connected to an inflation device through an air pipe, and the inflation device is located outside the cylinder body.

[0021] The above-mentioned method for expanding and loading annular specimens based on instantaneous bursting, the detonating device comprises a detonator, a fuse and an initiating head, the bursting agent is connected to the initiating head, and the initiating head provides electric current to the bursting agent to stimulate the bursting agent to instantly change from solid to gas.

[0022] In the above-mentioned method for expanding and loading annular specimens based on instantaneous bursting, the first cylinder body and the second cylinder body are respectively fixed on the test frame by hinges, and the annular specimen is made of metal, resin or glass.

[0023] In the above-mentioned annular sample expansion loading method based on instantaneous expansion and cracking, the rice husk or coal gangue is in granular form. When the detonator provides current, the combustion aid burns and causes the rice husk or coal gangue to be instantly converted into gas.

[0024] Compared with the prior art, the present invention brings the following beneficial technical effects: in the loading system of the present invention, an airbag body is arranged in the cylinder body, and the airbag body is approximately incompressible. Its rapid expansion can effectively convert the energy of the high-pressure gas into a high expansion rate, avoiding the temperature rise of the sample and the stress wave effect; compared with the traditional explosive expansion and electromagnetic expansion methods, the method of the present invention has high safety, simple operation, and is convenient for technology promotion, and is particularly suitable for the study of dynamic tensile properties and fracture behavior of materials.

[0025] The present invention proposes an annular specimen expansion loading method based on instantaneous expansion, which adopts an instantaneous expander as a driving device, avoids the explosion risk that may occur in a traditional explosive expansion ring loading device, and significantly improves the safety of the experimental process.

[0026] The present invention proposes an annular specimen expansion loading method based on instantaneous bursting. Compared with the existing explosive expansion ring device and electromagnetic expansion ring device, the present invention avoids excessive temperature rise of the annular specimen and experimental errors caused by stress wave effects, and achieves a more accurate loading effect.

[0027] The invention provides an annular specimen expansion loading method based on instantaneous bursting, wherein the loading process is easy to control, and the instantaneous burster and the airbag body used reduce complicated operation steps and improve the experimental efficiency.

[0028] The present invention proposes an annular specimen expansion loading method based on instantaneous expansion and cracking. By accurately controlling the excitation process of the instantaneous cracker, the present invention can achieve high strain rate loading in a relatively short time and meet the needs of high strain rate experiments.

[0029] The invention provides an annular specimen expansion loading method based on instantaneous bursting, which can be widely used in the fields of material mechanics, explosives, aerospace, military industry, etc., has strong applicability and expansibility, and is suitable for various experimental needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a front view of the loading system of the present invention.

[0031] Figure 2 It is a top view of the loading system of the present invention.

[0032] Figure 3 It is a schematic diagram of the structure of the inflatable airbag of the present invention.

[0033] Figure 4 It is a schematic structural diagram of the airbag body of the present invention.

[0034] Figure 5 It is a top view of the annular sample of the present invention.

[0035] In the figure: 1. test frame, 101. column, 102. crossbeam, 2. instantaneous bursting cylinder device, 201. first cylinder plug, 202. outer wall of the first cylinder body, 203. internal cavity of the first cylinder body, 204. outer wall of the second cylinder body, 205. internal cavity of the second cylinder body, 206. second cylinder plug, 3. inflatable airbag body, 301. airbag body, 302. inflation valve, 303. inflation device, 304. air pipe, 4. detonating device, 401. detonator, 402. first fuse, 403. second fuse, 404. third fuse, 405. fourth fuse, 406. fifth fuse, 407. sixth fuse, 408. first initiating head, 409. second initiating head, 6. ring-shaped specimen, 7. bursting agent. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0037] It is understandable that the connection relationship described in this application refers to direct or indirect connection. For example, the connection between A and B can be either a direct connection between A and B or an indirect connection between A and B through one or more other electrical components. For example, A and C can be directly connected, and C and B can be directly connected, so that A and B are connected through C. It is also understandable that the "A connects B" described in this application can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0038] In the description of this application, unless otherwise specified, " / " means "or", for example, A / B can mean A or B. "And / or" in this article is only a way to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0039] In the description of this application, words such as "first" and "second" are only used to distinguish different objects, and do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit differences. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0040] The technical solution of the present application is further described in detail below in conjunction with the accompanying drawings.

[0041] The working principle of the loading system of the present invention is as follows: the high-pressure gas generated by the instantaneous burster is used to drive the airbag body 301 to expand rapidly in the radial direction, thereby squeezing the annular sample 6 to achieve high strain rate loading.

[0042] Combination Figure 1 , Figure 2 As shown, the loading system of the present invention comprises a test frame 1, an instantaneous bursting cylinder device 2, an inflatable airbag 3, an initiating device 4, an annular specimen 6 and a bursting agent 7.

[0043] The test frame 1 is composed of four upper and lower cross beams 102 and four columns 101 therebetween, so as to form a stable support, and the test frame 1 is used to carry the instantaneous bursting cylinder device 2. The cross beam 102 at the top is connected to the outer wall 202 of the first cylinder body, and the cross beam 102 at the bottom is connected to the outer wall 204 of the second cylinder body through a hinge, and the two are connected in the same way to ensure the symmetry and stability of the device.

[0044] The instant bursting cylinder device 2 is located in the test frame 1. Specifically, the instant bursting cylinder device 2 includes a cylinder body, a first cylinder plug 201 and a second cylinder plug 206. The cylinder body is divided into two parts, namely, a first cylinder body located at the top and a second cylinder body located at the bottom. The first cylinder body includes an outer wall 202 of the first cylinder body and an internal cavity 203 of the first cylinder body. The second cylinder body includes an outer wall 204 of the second cylinder body and an internal cavity 205 of the second cylinder body.

[0045] Two limit plates extending outward are arranged at the positions opposite to the first cylinder body and the second cylinder body, and the two limit plates are symmetrically arranged along the central axis of the cylinder body. That is, when the first cylinder body and the second cylinder body are located opposite to each other, the cavity formed by the two limit plates can limit the raised portion of the inflatable airbag body 3.

[0046] The first cylinder plug 201 and the second cylinder plug 206 are respectively installed on the first cylinder body and the second cylinder body. Figure 3 , Figure 4 As shown, an inflatable airbag body 3 is arranged in the internal cavity of the cylinder body, and the inflatable airbag body 3 includes an airbag body 301. Outward protrusions are arranged on both sides of the airbag body 301, and the two protrusions are symmetrical with respect to the central axis of the airbag body 301. When gas is injected into the airbag body 301, the protrusions on both sides are just located in the two limit plates, and the annular sample 6 is tightly mounted on the two protrusions.

[0047] The airbag body 301 is provided with an inflation valve 302, which is connected to an inflation device 303 through an air pipe 304. The airbag body 301 is inflated with gas through the inflation device 303, and inflation is stopped when the pressure reaches 240-250 kPa. The inflation device 303 can achieve uniform inflation and automatically stop when the air pressure reaches a set value, thereby accurately controlling the expansion speed of the airbag body 301.

[0048] The bursting agent 7 includes rice husk / coal gangue and combustion aid, and the bursting agent 7 is arranged in the first cylinder body and the second cylinder body, and the bursting agent 7 is connected to the detonator 4. The detonator 4 is used to start the current excitation of the bursting agent 7, and the detonator 4 includes a detonator 401, a lead and an initiating head, and the lead is used to connect the initiating head and the detonator 401. The lead includes a first lead 402, a second lead 403, a third lead 404, a fourth lead 405, a fifth lead 406, and a sixth lead 407. The initiating head includes a first initiating head 408 and a second initiating head 409. The bursting agent 7 located in the first cylinder body and the second cylinder body is respectively bound with the first initiating head 408 and the second initiating head 409, and is built into the cylinder body and excited by current.

[0049] The shape of the ring sample 6 is as follows Figure 5 As shown, the annular sample 6 is made of brittle materials such as metal, resin or glass, and is subjected to high strain rate loading under the expansion of the airbag body 301 .

[0050] Rice husks or coal gangue are both in granular form. When the initiator head is triggered by electric current, high-temperature gas is instantly generated and the pressure in the cylinder body is increased sharply, thereby instantly expanding the inflatable airbag 3 and then loading the annular sample 6.

[0051] The internal cavity volume of the cylinder body is a fixed value. By adjusting the content of the bursting agent 7, the air pressure value can be changed to obtain different strain rates.

[0052] The present invention proposes an expansion loading method for an annular sample based on instantaneous bursting, which utilizes the above-mentioned loading system and includes the following steps: Step 1, fix the annular sample 6 on the periphery of the raised portion of the airbag body 301, and the inflation device 303 inflates the airbag body 301 through the air pipe 304 and the inflation valve 302. When the pressure reaches 240-250 kPa, stop the inflation.

[0053] Step 2: Place the bursting agent 7 into the internal cavity 203 of the first cylinder body and the internal cavity 205 of the second cylinder body. The bursting agent 7 is bundled together with the first initiating head 408 and the second initiating head 409, and is connected to the third lead 404 and the fifth lead 406 through the first lead 402. Another set of second leads 403 is connected to the fourth lead 405 and the sixth lead 407.

[0054] Step 3: Check whether the circuits of all leads are short-circuited or open-circuited to ensure that the circuits are connected normally. After checking that the circuits are correct, press the switch of the detonator 401 to complete the detonation operation. The bursting agent 7 is excited by the current and changes from solid to gas in 0.05 to 0.5 seconds, and generates pressure to drive the airbag body 301 to expand, thereby loading the annular sample 6.

[0055] Step 4: Calculate the annular stress of the annular specimen 6 using formula (1). Formula (1) is derived from (2), (3), and (4).

[0056] (1).

[0057] (2).

[0058] (3).

[0059] (4).

[0060] In formula (1): is the hoop stress of the annular specimen; is the cross-sectional area of ​​the annular specimen; is the height of the airbag body; F is the axial positive pressure of the cylinder body; It is the projected area of ​​the combination of the annular specimen and the airbag body where the axial force acts; is the cross-sectional area of ​​the airbag body; is the hoop stress of the airbag body; For strain.

[0061] In formula (2): is the hoop stress of the annular specimen; is the cross-sectional area of ​​the annular specimen; is the contact surface pressure between the airbag body and the annular specimen; is the height of the ring specimen.

[0062] In formula (3): is the hoop stress of the airbag body; is the cross-sectional area of ​​the airbag body; is the contact surface pressure between the airbag body and the annular specimen; is the height of the annular specimen; is the gas pressure in the cylinder body; is the height of the airbag body.

[0063] In formula (4): is the hoop stress of the airbag body; For strain.

[0064] In summary, the present invention can effectively solve the problems of safety, operability and thermal effect of test pieces in practical applications of traditional explosive expansion rings and electromagnetic expansion rings, ensuring higher experimental accuracy and wider application prospects.

[0065] Parts not described in the present invention can be implemented by referring to the existing technology.

[0066] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to be limiting of the present application. As long as they are within the spirit of the present application, appropriate changes and modifications to the above embodiments should fall within the scope of protection of the claims of the present application.

Claims

1. A ring specimen expansion loading method based on instantaneous cracking, characterized in that: The loading system adopted by the invention comprises a test frame, an instantaneous bursting cylinder device, an inflatable airbag, an initiating device, an annular specimen and an expanding agent. The instantaneous bursting cylinder device is located in the test frame; the instantaneous bursting cylinder device comprises a cylinder body, a first cylinder plug and a second cylinder plug. The cylinder body is divided into two parts, namely a first cylinder body located at the top and a second cylinder body located at the bottom. Two limit plates extending outward are arranged at the opposite positions of the first cylinder body and the second cylinder body; the first cylinder plug and the second cylinder plug are respectively installed on the first cylinder body and the second cylinder body. The inflatable airbag is arranged in the inner cavity of the cylinder body. The inflatable airbag comprises an airbag body. Outward protrusions are arranged on both sides of the airbag body. The two protrusions are symmetrical with respect to the central axis of the airbag body. When gas is injected into the airbag body, the protrusions on both sides are just located in the two limit plates, and the annular specimen is tightly sleeved on the two protrusions. The said bursting agent comprises rice husk / coal gangue and combustion aid, and the said bursting agent is arranged in the first cylinder body and the second cylinder body, and the said bursting agent is connected with the detonating device; The loading method comprises the following steps: Step 1: Inflate the airbag body until the pressure reaches 240-250 kPa, then stop inflating; Step 2: Turn on the detonator, the bursting agent is excited by electric current, and changes from solid to gas in 0.05 to 0.5 seconds, and generates pressure to drive the airbag body to expand, thereby loading the annular sample; Step 3: Calculate the annular stress of the annular specimen using formula (1): （1）； In formula (1): is the hoop stress of the annular specimen; is the cross-sectional area of ​​the annular specimen; is the height of the airbag body; F is the axial positive pressure of the cylinder body; It is the projected area of ​​the combination of the annular specimen and the airbag body where the axial force acts; is the cross-sectional area of ​​the airbag body; is the hoop stress of the airbag body; For strain.

2. The method for loading annular specimen by expansion based on instantaneous bursting according to claim 1, characterized in that: Formula (1) is derived from formulas (2), (3), and (4): （2）； （3）； （4）； In formula (2): is the hoop stress of the annular specimen; is the cross-sectional area of ​​the annular specimen; is the contact surface pressure between the airbag body and the annular specimen; is the height of the annular specimen; In formula (3): is the hoop stress of the airbag body; is the cross-sectional area of ​​the airbag body; is the contact surface pressure between the airbag body and the annular specimen; is the height of the annular specimen; is the gas pressure in the cylinder body; is the height of the airbag body; In formula (4): is the hoop stress of the airbag body; For strain.

3. The method for loading annular specimen by expansion based on instantaneous bursting according to claim 1, characterized in that: An inflation valve is arranged on the airbag body, and the inflation valve is connected with an inflation device through an air pipe, and the inflation device is located outside the cylinder body.

4. The method for loading annular specimen by expansion based on instantaneous bursting according to claim 1, characterized in that: The detonating device comprises a detonator, a fuse and an initiating head. The bursting agent is connected with the initiating head. The initiating head provides electric current to the bursting agent to stimulate the bursting agent to instantly change from solid to gas.

5. The method for loading annular specimen by expansion based on instantaneous bursting according to claim 1, characterized in that: The first cylinder body and the second cylinder body are fixed on the test frame through hinges respectively, and the annular test specimen is made of metal, resin or glass.

6. The method for loading annular specimen by expansion based on instantaneous bursting according to claim 1, characterized in that: Rice husks or coal gangue are both in granular form. When the detonator provides electric current, the combustion aid burns and causes the rice husks or coal gangue to be instantly converted into gas.

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