A method for expansion loading of annular specimens based on instantaneous cracking

Abstract

The present invention discloses a method for expanding and loading an annular specimen based on instantaneous bursting, and relates to the technical field of measuring the deformation and fracture characteristics of materials under dynamic loading. The loading system adopted by the method includes a test frame, an instantaneous bursting cylinder device, an inflatable airbag, an initiating device, an annular specimen and an expansion agent. The expansion agent includes rice husk / coal gangue and a combustion aid. The expansion agent is set in the first cylinder body and the second cylinder body, and the expansion agent is connected to the initiating device. The loading method is as follows: inflate the airbag body until the pressure reaches 240-250kPa, then stop inflating; turn on the initiating device, the expansion agent is excited by electric current and changes from solid to gas in a short time, generating pressure to drive the airbag body to expand, thereby loading the annular specimen. The present invention avoids excessive temperature rise of the specimen and experimental errors caused by stress wave effects, and achieves a more accurate loading effect.

Description

Technical Field

[0001] The present invention relates to the technical field of measuring deformation and fracture characteristics of materials under dynamic loading, and in particular to a ring-shaped specimen expansion loading method based on instantaneous bursting. Background Art

[0002] The deformation and fracture characteristics of materials under dynamic loading are of great research value in various fields, including industry, military, and national defense. The expansion ring experimental technique, a key method for studying the dynamic tensile properties and fracture behavior of materials, has attracted considerable attention due to its ability to achieve uniform one-dimensional tensile stress. Currently, explosive expansion rings and electromagnetic expansion rings are the most widely used techniques. Many researchers have used these techniques to study the dynamic mechanisms under quasi-one-dimensional stress states, but both have certain technical limitations.

[0003] The explosive expansion ring experimental device detonates a central charge, utilizing the pressure of the explosion products to drive the rapid expansion of a specimen ring. During the expansion process, stress wave reflection and tensile unloading waves cause the specimen ring to enter a free expansion phase. Advantages of this method include: limited specimen size; high strain rates; and minimal temperature rise in the ring during loading. However, this method also has significant disadvantages: the inevitable generation of shock waves, rarefaction waves, and lateral effects during loading make it difficult to fully achieve a one-dimensional tensile stress state; impedance mismatch between the driver and the specimen ring material affects the stability of the experimental results; and the device requires high processing and operation, resulting in low experimental safety.

[0004] The electromagnetic expansion ring experimental setup uses a solenoid to generate a strong magnetic field, driving the expansion of the specimen ring via the Lorentz force. Advantages of this method include: the Lorentz force acts uniformly on the specimen ring, avoiding wave effects caused by mechanical loading; the expansion rate and strain rate of the specimen ring can be precisely controlled by adjusting circuit parameters; and the measurement of flow stress, plastic strain, and strain rate history is simplified. However, the electromagnetic expansion ring also has drawbacks: the loading strain rate is low, limiting the specimen ring size; and the high current causes a significant temperature rise in the specimen ring, affecting the accuracy of dynamic performance testing.

[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 cracking, 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 solutions: a method for expanding and loading an annular specimen based on instantaneous bursting, wherein the loading system adopted 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 provided 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 is provided in the internal cavity of the cylinder body. The inflatable airbag includes an airbag body, and outward protrusions are provided 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 exactly located in the two limit plates, and the annular sample is tightly placed on the two protrusions.

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

[0009] The loading method comprises the following steps: Step 1, inflating the airbag body until the pressure reaches 240-250 kPa, and then stopping the inflation.

[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. The pressure generated drives 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 ring 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 expansion loading method for annular specimens based on instantaneous cracking, formula (1) is derived from formulas (2), (3), and (4):

[0015] (2).

[0016] (3).

[0017] (4).

[0018] In formula (2): is the hoop stress of the ring 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.

[0019] 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 ring specimen; is the gas pressure in the cylinder body; is the height of the airbag body.

[0020] In formula (4): is the hoop stress of the airbag body; For strain.

[0021] In the above-mentioned method for expanding and loading an annular specimen based on instantaneous bursting, an inflation valve is provided 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.

[0022] The above-mentioned method for expanding and loading annular specimens based on instantaneous bursting, the detonating device includes a detonator, a fuse and an initiating head, the bursting agent is connected to the initiating head, and the initiating head provides current to the bursting agent to stimulate the bursting agent to instantly change from solid to gas.

[0023] In the above-mentioned expansion loading method for annular specimens based on instantaneous bursting, the first cylinder body and the second cylinder body are respectively fixed to the test frame by hinges, and the annular specimen is made of metal, resin or glass.

[0024] In the above-mentioned expansion loading method of annular specimen based on instantaneous bursting, rice husks or coal gangue are both in granular form. When the detonator provides current, the combustion aid burns and causes the rice husks or coal gangue to be instantly converted into gas.

[0025] Compared with the existing technology, 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 and stress wave effect of the sample; compared with 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.

[0026] The present invention proposes an expansion loading method for annular specimens based on instantaneous expansion, which uses an instantaneous expander as a driving device, avoids the explosion risk that may occur in traditional explosive expansion ring loading devices, and significantly improves the safety of the experimental process.

[0027] The present invention proposes a ring 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 ring specimen and experimental errors caused by stress wave effects, and achieves a more accurate loading effect.

[0028] The invention proposes 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.

[0029] The present invention proposes an annular specimen expansion loading method based on instantaneous bursting. By precisely controlling the excitation process of the instantaneous burster, the present invention can achieve high strain rate loading in a relatively short time, thus meeting the requirements of high strain rate experiments.

[0030] The invention proposes an annular specimen expansion loading method based on instantaneous bursting, which can be widely used in fields such as material mechanics, explosives, aerospace, and military industry. It has strong applicability and scalability and is suitable for various experimental needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a front view of the loading system of the present invention.

[0032] Figure 2 It is a top view of the loading system of the present invention.

[0033] Figure 3 It is a schematic structural diagram of the inflatable airbag of the present invention.

[0034] Figure 4 It is a structural schematic diagram of the airbag body of the present invention.

[0035] Figure 5 It is a top view of the annular specimen of the present invention.

[0036] In the figure: 1. Test frame, 101. Column, 102. Beam, 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, 301. Airbag body, 302. Inflating valve, 303. Inflating 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 specimen, 7. Bursting agent. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application.

[0038] It is understood that the connection relationships described in this application refer to direct or indirect connections. 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 via one or more other electrical components. For example, A and C can be directly connected, and C can be directly connected to B, so that A and B are connected through C. It is also understood that the description of "A connecting to B" in this application can be a direct connection between A and B or an indirect connection between A and B via one or more other electrical components.

[0039] In the description of this application, unless otherwise specified, " / " means "or". For example, A / B can mean A or B. "And / or" in this document is simply a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0040] In the description of this application, words such as "first" and "second" are used only to distinguish different objects and do not limit the quantity or execution order. In addition, words such as "first" and "second" do not necessarily mean different. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0041] The technical solution of the present application is further described in detail below with reference to the accompanying drawings.

[0042] 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.

[0043] Combine Figure 1 、 Figure 2 As shown, the loading system of the present invention includes a test frame 1, an instantaneous bursting cylinder device 2, an inflatable air bag 3, an initiating device 4, an annular specimen 6 and a bursting agent 7.

[0044] The test frame 1 consists of four top and bottom crossbeams 102, supported by four columns 101. This provides a stable support for the instantaneous bursting cylinder device 2. The top crossbeam 102 is hinged to the outer wall 202 of the first cylinder body, while the bottom crossbeam 102 is hinged to the outer wall 204 of the second cylinder body. Both are connected in the same manner to ensure symmetry and stability.

[0045] The instantaneous bursting cylinder device 2 is located within the test frame 1. Specifically, the instantaneous 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: 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 and an internal cavity 203 of the first cylinder body. The second cylinder body includes an outer wall 204 and an internal cavity 205 of the second cylinder body.

[0046] Two outwardly extending stop plates are disposed at opposing locations of the first and second cylinder bodies. The two stop plates are symmetrically arranged along the central axis of the cylinder bodies. In other words, when the first and second cylinder bodies are positioned opposite each other, the cavity formed by the two stop plates can limit the raised portion of the inflatable airbag 3.

[0047] 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 provided in the internal cavity of the cylinder body. The inflatable airbag body 3 includes an airbag body 301. Outward protrusions are provided on both sides of the airbag body 301. 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 exactly located in the two limit plates, and the annular sample 6 is tightly placed on the two protrusions.

[0048] The airbag body 301 is equipped with an inflation valve 302, which is connected to an inflation device 303 via an air tube 304. The inflation device 303 inflates the airbag body 301 with gas, stopping when the pressure reaches 240-250 kPa. The inflation device 303 ensures uniform inflation and automatically stops when the pressure reaches a set value, thereby precisely controlling the expansion speed of the airbag body 301.

[0049] The cracking agent 7 comprises rice husk / coal gangue and an oxidizing agent. The cracking agent 7 is disposed within both the first and second cylinder bodies and is connected to an initiating device 4. The initiating device 4 is used to initiate the current excitation of the cracking agent 7. The initiating device 4 comprises a detonator 401, leads, and an initiating head. The leads are used to connect the initiating head to the detonator 401. The leads comprise 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 heads comprise a first initiating head 408 and a second initiating head 409. The cracking agents 7 within the first and second cylinder bodies are respectively bound to the first initiating head 408 and the second initiating head 409, and are internally housed within the cylinder bodies for excitation by current.

[0050] The shape of the ring sample 6 is as follows Figure 5 As shown, the annular sample 6 is made of a brittle material such as metal, resin or glass, and is subjected to a high strain rate load under the expansion of the airbag body 301 .

[0051] Rice husks or coal gangue are both granular. When the initiator is triggered by electric current, high-temperature gas is instantly generated, causing a sharp increase in pressure in the cylinder body, thereby instantly expanding the inflatable airbag 3 and then loading the annular sample 6.

[0052] 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, thereby obtaining different strain rates.

[0053] The present invention proposes a ring-shaped specimen expansion loading method based on instantaneous bursting, which utilizes the above-mentioned loading system and includes the following steps: Step 1, fix the ring-shaped specimen 6 on the periphery of the raised portion of the airbag body 301, and the inflation device 303 is connected to the air pipe 304 and the inflation valve 302 to inflate the airbag body 301. When the pressure reaches 240~250kPa, stop inflation.

[0054] 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.

[0055] Step 3: Check all leads for shorts or breaks to ensure proper connection. Once the circuits are correct, press the switch on detonator 401 to complete the detonation. The current excites the bursting agent 7, transforming it from a solid to a gas within 0.05-0.5 seconds. The resulting pressure drives the airbag body 301 to expand, thereby loading the annular specimen 6.

[0056] Step 4: Calculate the annular stress of the annular specimen 6 using formula (1). Formula (1) is derived from (2), (3), and (4).

[0057] (1).

[0058] (2).

[0059] (3).

[0060] (4).

[0061] In formula (1): is the hoop stress of the ring 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.

[0062] In formula (2): is the hoop stress of the ring 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.

[0063] 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 ring specimen; is the gas pressure in the cylinder body; is the height of the airbag body.

[0064] In formula (4): is the hoop stress of the airbag body; For strain.

[0065] In summary, the present invention can effectively solve the safety, operability and specimen thermal effect problems of traditional explosive expansion rings and electromagnetic expansion rings in practical applications, ensuring higher experimental accuracy and broader application prospects.

[0066] Parts not described in the present invention can be implemented by referring to the existing technology.

[0067] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present application and are not intended to limit the present application. Any appropriate changes and modifications to the above embodiments should fall within the scope of protection of the claims of the present application as long as they are within the spirit 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, 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, the cylinder body is divided into two parts, namely a first cylinder body located at the upper end and a second cylinder body located at the lower end, two limit plates extending outward are provided at opposite positions of the first cylinder body and the second cylinder body; the first cylinder plug and the second cylinder plug are respectively mounted on the first cylinder body and the second cylinder body, the inflatable airbag is provided in the internal cavity of the cylinder body, the inflatable airbag comprises an airbag body, outward protrusions are provided 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 is arranged in the first cylinder body and the second cylinder body, and is connected to 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 the current and changes from solid to gas in 0.05 to 0.5 seconds. The pressure generated drives the airbag body to expand, thereby loading the annular sample. Step 3: Calculate the annular stress of the annular specimen using formula (1): In formula (1): X is the hoop stress of the ring specimen; A X is the cross-sectional area of ​​the annular specimen; H Y is the height of the airbag body; F is the axial positive pressure of the cylinder body; A1 is the projected area of ​​the combination of the annular specimen and the airbag body where the axial force acts; A Y is the cross-sectional area of ​​the airbag body; σ Y is the hoop stress of the airbag body; where ∈ is the strain.

2. The method for expanding and loading annular specimens based on instantaneous cracking according to claim 1, characterized in that: Formula (1) is derived from formulas (2), (3), and (4): s X A X =60*p a *H X (2); σ Y AND Y =60*p a *H X =60*p1*H Y (3); s Y =s Y (∈) (4); In formula (2): X is the hoop stress of the ring specimen; A X is the cross-sectional area of ​​the annular specimen; p a is the contact surface pressure between the airbag body and the annular sample; H X is the height of the ring specimen; In formula (3): Y A is the hoop stress of the airbag body; Y is the cross-sectional area of ​​the airbag body; p a is the contact surface pressure between the airbag body and the annular sample; H X is the height of the annular sample; p1 is the gas pressure in the cylinder body; H Y is the height of the airbag body; In formula (4): Y is the hoop stress of the airbag body; where ∈ is the strain.

3. The method for expanding and loading annular specimens based on instantaneous cracking according to claim 1, characterized in that: An inflation valve is provided on the airbag body, and the inflation valve is connected to an inflation device through an air pipe, and the inflation device is located outside the cylinder body.

4. The method for expanding and loading an annular specimen based on instantaneous cracking according to claim 1, characterized in that: The initiating device comprises a detonator, a fuse and an initiating head. The bursting agent is connected to 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 expanding and loading an annular specimen based on instantaneous cracking according to claim 1, characterized in that: The first cylinder body and the second cylinder body are fixed on the test frame respectively through hinges, and the annular sample is made of metal, resin or glass.

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

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