Design method of non-fragmentation explosion-proof structure and non-fragmentation explosion-proof structure

Abstract

The present invention provides a design method of a non-fragmentation explosion-proof structure and a non-fragmentation explosion-proof structure. The explosion-proof structure is designed by the design method to ensure that the outermost layer of the explosion-proof structure does not break, thereby improving the safety and reliability of the explosion-proof structure. The specific steps of the method are: firstly, the explosion-proof structure is structurally designed to obtain the number of layers of the explosion-proof structure, the protective materials used in each layer, and the thickness of each layer; and the attenuation coefficient of the shock wave in each layer of the explosion-proof structure is calculated; then the stress wave peak value at the boundary of the outermost structure of the explosion-proof structure caused by the shock wave is calculated; and then it is determined whether the strength of the outermost material is greater than the stress wave peak value; if it is greater, it is considered that the outermost structure will not break; if it is not greater, it is considered that the outermost structure will break, and the explosion-proof structure is redesigned and the stress wave peak value at the boundary of the outermost structure of the explosion-proof structure caused by the shock wave is recalculated.

Description

Technical Field

[0001] The invention relates to a method for designing an explosion-proof structure, in particular to a method for designing a non-fragmentation explosion-proof structure, and belongs to the field of police and military public safety and defense equipment. Background Art

[0002] Explosions are characterized by rapid eruption and wide destruction. How to quickly deal with explosives is an important issue in the current security and military fields. Traditional explosion-proof equipment mainly includes metal explosion-proof tanks and explosion-proof balls. Metal explosion-proof tanks and explosion-proof balls are heavy and inconvenient to move. Explosion-proof products made of flexible composite materials are a trend in the current explosion-proof field. Flexible composite explosion-proof products are light in weight, and excessive explosions will not cause secondary damage, which can control the damage within a limited range.

[0003] The design of metal explosion-proof tanks uses high-strength steel materials of a certain thickness. The detection method is generally to check whether there are penetrating holes in the structure after the explosion to determine whether it is qualified. For explosion-proof equipment made of flexible composite materials, there is currently no universal testing standard. Generally, pine wood target plates set in a certain safe place are used to determine whether fragments fly out of the flexible explosion-proof equipment.

[0004] Since it is made of composite materials, its protection against fragments is mainly through high-strength multi-layer fibers that intercept the fragments inside. Since the fibers produced by different manufacturers have different characteristics, some have strong bulletproof ability but weak tear resistance; some have strong tear resistance but weak bulletproof ability. When designing current composite explosion-proof equipment, it is generally based on the perspective of fragments, and multi-layer fibers are designed for fragment protection. The design scheme uses a certain bulletproof fiber without a composite layer. As long as the fiber thickness is sufficient, it can play a bulletproof role. However, there is currently no corresponding design method for composite products to protect against explosion shock waves. Generally speaking, there are three main solutions for composite explosion-proof products: ① Through continuous winding of a certain specific bulletproof fiber; ② Solidifying the fiber into a whole through resin; ③ Sewing and stacking the fibers.

[0005] For near-field explosions or bare explosives, the main effect on the structure is the shock wave. Generally speaking, the shock wave will propagate quickly and act on the explosion-proof structure, and then the fragments will act on the explosion-proof structure. If the shock wave tears the structure in advance, and the fragments have a low speed, after the structure is torn, the medium and low-speed fragments will fly out from the tear, causing casualties. For the above-mentioned ① and ② schemes, when the explosion occurs, the fiber will be torn in the outermost layer under the action of the stress wave, which poses a certain risk. Although increasing the thickness of the fiber can reduce the occurrence of this situation to a certain extent, it will cause an increase in cost and weight, and increasing the thickness of the fiber will not significantly increase the protective effect against shock waves. For the ③ scheme, at the moment of the explosion, the seams are prone to tearing, and the overall structure is broken, which also poses a certain risk.

[0006] In general, how to prevent the tearing and breakage of the outermost fiber structure is a difficult problem in the current design of composite explosion-proof equipment. Summary of the invention

[0007] In view of this, the present invention provides a design method for a non-fragmentation explosion-proof structure. The explosion-proof structure is designed by using the design method to ensure that the outermost layer of the explosion-proof structure does not break, thereby improving the safety and reliability of the explosion-proof structure.

[0008] A design method for a non-fragmentation explosion-proof structure, the specific steps are:

[0009] Step 1: Design the explosion-proof structure to obtain the number of layers, protective materials used for each layer, and thickness of each layer;

[0010] Step 2: Calculate the attenuation coefficient of the shock wave in each layer of the designed explosion-proof structure through simulation;

[0011] Step 3: Calculate the peak value of the stress wave when the shock wave acts on the outermost structural boundary of the explosion-proof structure;

[0012] Step 4: Determine whether the strength of the outermost structural material is greater than the peak value of the stress wave of the shock wave at the outermost structural boundary of the explosion-proof structure calculated in step 3;

[0013] If it is greater than, it is considered that the outermost structure will not be broken, and the current explosion-proof structure is regarded as a non-fragmentation explosion-proof structure;

[0014] If it is not greater than, it is considered that the outermost structure will be broken, and the explosion-proof structure should be redesigned and the stress wave peak value of the shock wave acting on the boundary of the outermost structure should be recalculated until the outermost structure will not be broken.

[0015] As a preferred embodiment of the present invention, the composite explosion-proof structure has n layers, and the first layer, the second layer, ... the nth layer are arranged from the explosion-facing surface to the back explosion surface of the composite explosion-proof structure;

[0016] Then the peak value of the stress wave at the outermost boundary of the composite explosion-proof structure is for:

[0017]

[0018] Where: P0 is the intensity of the shock wave incident on the first layer; K i is the wave impedance of the protective material used in the i-th layer; x i is the thickness of the i-th layer, α i is the attenuation coefficient of the i-th layer.

[0019] As a preferred embodiment of the present invention, when the explosion-proof structure needs to be redesigned, the arrangement of each layer is modified or the number of layers of the explosion-proof structure is increased.

[0020] As a preferred embodiment of the present invention, when the explosion-proof structure needs to be redesigned, the thickness of one or more layers of protective material in the composite explosion-proof structure is increased.

[0021] As a preferred embodiment of the present invention, when the explosion-proof structure needs to be redesigned, the type of one or more layers of protective material is changed.

[0022] In addition, the present invention provides a non-fragmentation explosion-proof structure: it is at least a three-layer structure, and the strength of the outermost structural material is greater than the stress wave peak value of the shock wave at the outermost structural boundary of the explosion-proof structure.

[0023] As a preferred embodiment of the present invention: the explosion-proof structure is a three-layer structure, the first layer is an inner protective layer, the second layer is a stress wave adjustment layer, and the third layer is an outer protective layer;

[0024] The materials of the inner protective layer and the outer protective layer are bulletproof fibers, the material of the stress wave regulating layer is a material with wave impedance lower than that of the bulletproof fibers; the material strength of the outer protective layer is greater than the stress wave peak value of the shock wave at the boundary of the outer protective layer.

[0025] As a preferred embodiment of the present invention: the explosion-proof structure is a four-layer structure, the first layer is an inner protective layer, the second layer is a stress wave adjustment layer, the third layer is an outer protective layer, and the fourth layer is a stress wave adjustment layer;

[0026] The materials of the inner protective layer and the outer protective layer are bulletproof fibers, and the materials of the inner stress wave regulating layer and the outer stress wave regulating layer are materials with wave impedance lower than that of the bulletproof fibers; the material strength of the outer protective layer is greater than the stress wave peak value of the shock wave at the boundary of the outer protective layer.

[0027] Beneficial effects:

[0028] (1) When the design method of the present invention is used to design an explosion-proof structure, the relationship between the peak value of the stress wave at the boundary of the outermost structure of the explosion-proof structure acted by the shock wave and the strength of the outermost material is considered. Therefore, active design can be used during the design stage to ensure that the outermost layer of the composite explosion-proof structure does not rupture, thereby improving the safety and reliability of the composite explosion-proof structure. The design method is also universal.

[0029] (2) When shock waves propagate in different media, there will be reflection and refraction. When calculating the peak value of the stress wave when the shock wave acts on the outermost structure of the explosion-proof structure, the reflection and refraction are comprehensively considered to ensure the accuracy of the calculation results.

[0030] (3) When it is calculated that the outermost structure will be broken, the explosion-proof layer arrangement is modified or the number of layers of the explosion-proof structure is increased, one or more layers of protective materials are changed, or the thickness of one or more layers of protective materials is increased according to the principle of wave impedance matching; and the above structural parameters can be changed one by one, or multiple structural parameters can be changed at the same time; the explosion-proof structure is redesigned to ensure the overall safety of the designed explosion-proof structure.

[0031] (4) The typical non-fragmentation explosion-proof structures designed all include a protective layer and a stress wave regulation layer, wherein the stress wave regulation layer mainly plays a role in stress wave regulation, which can reduce the peak value of the stress wave incident on the lower layer and avoid the outermost layer of the structure from being crushed.

[0032] (5) When a four-layer non-fragmentation explosion-proof structure is used, an external stress wave adjustment layer is provided on the outermost layer to reduce the tearing of the outer protective layer caused by the stress wave reflection loading; at the same time, a material with a wave impedance lower than that of the outer protective layer is used to reduce the intensity of the reflected stress wave. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a flow chart of the design method of the non-fragmentation explosion-proof structure of the present invention;

[0034] Figure 2 Schematic diagram of shock wave propagation in a single-layer protective structure;

[0035] Figure 3 Schematic diagram of shock wave propagation in a multi-layer protective structure;

[0036] Figure 4 This is a schematic diagram of the structure of a typical four-layer non-fragmentation explosion-proof structure.

[0037] Among them: 1-inner protective layer, 2-inner stress wave regulating layer, 3-outer protective layer, 4-outer stress wave regulating layer. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0039] This embodiment provides a design method for a non-fragmentation explosion-proof structure. By adopting this design method to design an explosion-proof structure, it is possible to ensure that the outermost layer of the explosion-proof structure does not break.

[0040] This article takes the non-fragmentation flexible composite explosion-proof structure as an example and introduces its structural design process in detail.

[0041] like Figure 1 As shown, the specific steps of the method are:

[0042] Step 1: Design the structure of the flexible composite explosion-proof structure according to a conventional design method of the flexible composite explosion-proof structure (such as the design method of the non-contact flexible explosion-proof device in the prior art) to obtain the number of layers of the flexible composite explosion-proof structure, the protective material used for each layer, and the thickness of each layer;

[0043] Step 2: Calculate the attenuation coefficient of the shock wave in each layer of material (i.e., each layer of medium) of the flexible composite explosion-proof structure designed in step 1 through simulation:

[0044] Generally speaking, the propagation of shock waves in dense media is exponentially attenuated, and the attenuation coefficient can be tested through corresponding experiments or simulations. For general flexible explosion-proof structures, typical dense protective materials include PE fiber, aramid fiber, and rubber materials; through simulation calculations, it can be obtained that the shock wave attenuation coefficient in PE material is 0.0025 (kPa / mm), the shock wave attenuation coefficient in aramid fiber material is 0.0035 (kPa / mm), and the shock wave attenuation coefficient in rubber material is 0.0112 (kPa / mm).

[0045] Step 3: Calculate the peak value of the stress wave when the shock wave acts on the outermost structure of the flexible explosion-proof structure:

[0046] When this design method is used to design an explosion-proof structure, the intensity of the shock wave incident on the interior of the protection structure is first calculated based on the protection equivalent and protection distance of the designed explosion-proof structure, and then the peak value of the stress wave of the outermost structure of the flexible explosion-proof structure is further calculated.

[0047] When shock waves propagate in different media, there will be reflection and refraction. The calculation of reflection and refraction is mainly related to the wave impedance of the material (wave impedance = sound speed of the material * density of the material).

[0048] Step three calculates the peak value of the stress wave transmitted to the outermost structure boundary of the flexible composite explosion-proof structure (ie, the outer surface of the outermost structure).

[0049] For a single-layer protective structure, since the wave impedance of air is much smaller than that of general solid materials, if a single-layer continuous material is used, the stress wave at the material boundary will be completely reflected, forming a double stress state.

[0050] like Figure 2 As shown, at time T0, the shock wave enters the protective structure, and at time T1, the shock wave reaches the outer surface of the protective structure and is emitted; let its thickness be x1, the attenuation coefficient be α1 (calculated in step 2), and the intensity of the shock wave incident on the inside of the protective structure at time T0 be P0, then the stress wave peak value at its boundary (the outer surface of the single-layer protective structure, i.e., the back explosion surface) is for:

[0051]

[0052] When the shock wave propagates in different media, it will encounter transmission and reflection phenomena. The calculation of its reflection and refraction is mainly related to the wave impedance of the material (wave impedance = sound speed of the material * density of the material). For multi-layer protective structures, since each layer of the structure is made of different materials, the same phenomenon will occur when the shock wave acts on the explosion-proof structure. Figure 3 As shown, the intensity of the shock wave incident on the protective structure is P0; under the approximate condition and without considering the shock wave attenuation, let the two adjacent materials be material I and material T, where material T is located on the back explosion side of material I. When the shock wave reaches the interface between material I and material T, transmission and reflection will occur; let the intensity of the shock wave reaching the interface, i.e. the incident shock wave, be P I , the intensity of the transmitted shock wave transmitted into the material T is P T ( Figure 3 Medium I ′ is the intensity of the reflected shock wave reflected at the butt surface); then according to the transmission law of waves on different medium surfaces:

[0053]

[0054] From this, we can get the intensity of the transmitted shock wave that penetrates into the material T as P T for:

[0055]

[0056] Among them, K T =ρ T C T is the wave impedance of material T, ρ T is the density of material T, C T is the sound velocity of material T; K I =ρ I C I is the wave impedance of material I, ρ Iis the density of material I, C I is the sound velocity of material I.

[0057] Based on this, for the double-layer protection structure, Figure 3 As shown in the figure, the intensity of the shock wave incident into the protective structure is P0, and the intensity of the shock wave reaching the interface between the two layers of material is: Let the first layer (i.e., inner layer) have a thickness of x1, an attenuation coefficient of α1, and a wave impedance of K1; let the second layer (i.e., outer layer) have a thickness of x2, an attenuation coefficient of α2, and a wave impedance of K2; then the peak value of the stress wave at the outermost boundary is for:

[0058]

[0059] Similarly, for a three-layer structure: let the first layer (i.e., inner layer) have a thickness of x1, an attenuation coefficient of α1, and a wave impedance of K1; let the second layer (i.e., middle layer) have a thickness of x2, an attenuation coefficient of α2, and a wave impedance of K2; let the third layer (i.e., outermost layer) have a thickness of x3, an attenuation coefficient of α3, and a wave impedance of K3; then the stress wave peak value at the outermost boundary is for:

[0060]

[0061] By analogy, for an n-layer structure, the peak value of the stress wave at the boundary of its outermost layer (i.e., the nth layer, let the n-layer structure from the explosion-proof structure's front explosion surface to the back explosion surface be the first layer, the second layer...the nth layer) is for:

[0062]

[0063] Step 4: Compare the peak value of the shock wave calculated in step 3 at the boundary of the outermost structure of the flexible explosion-proof structure with the strength of the outermost material to determine whether the outermost structure will be broken:

[0064] For a single-layer protective structure, the conditions for the outermost layer not to rupture are:

[0065]

[0066] in is the material strength of the single-layer protective structure.

[0067] If a single layer of continuous material is used, the stress wave will be completely reflected at the material boundary, forming a double stress state, which will cause tearing or collapse at the material boundary.

[0068] Based on this, flexible composite explosion-proof structures generally adopt a multi-layer structure. The general condition for the outermost layer of the flexible composite explosion-proof structure not to tear is that the peak value of the stress wave transmitted to the outermost boundary of the flexible composite explosion-proof structure does not exceed the strength of the outermost structural material.

[0069] For a double-layer protective structure, let the strength of the outermost layer be The conditions for the outermost layer of material not to break are:

[0070]

[0071] Similarly, for a three-layer structure, let the strength of the outermost layer be The condition that the outermost layer does not rupture is:

[0072]

[0073] For an n-layer structure, let the strength of the outermost layer be The condition that the outermost layer does not rupture is:

[0074]

[0075] According to the above conditions, it is judged whether the outermost material of the flexible composite explosion-proof structure will be broken; if it is judged that the strength of the outermost material is not greater than the peak value of the stress wave transmitted to the outermost boundary of the flexible composite explosion-proof structure, it is considered that the outermost material will be broken; at this time, in order to ensure that the outermost layer of the designed flexible composite explosion-proof structure does not break, return to step one, modify the structural parameters of the designed flexible composite explosion-proof structure, such as designing according to the wave impedance matching principle, modifying the arrangement of the composite explosion-proof layer or increasing the number of layers of the composite explosion-proof structure, changing one or more layers of protective materials, and increasing the thickness of one or more layers of protective materials (i.e., increasing the number of winding layers); the above structural parameters can be changed one by one, or multiple structural parameters can be changed at the same time; thereby realizing the redesign of the flexible composite explosion-proof structure; after modifying the structural parameters, the above steps two to four are calculated again until it is judged that the outermost material of the flexible composite explosion-proof structure will not be broken according to the above conditions (i.e., the strength of the outermost material is greater than the peak value of the stress wave transmitted to the outermost boundary of the flexible composite explosion-proof structure).

[0076] If no new protective material is added when modifying the structural parameters of the designed flexible composite explosion-proof structure, there is no need to repeat the calculation in step 2.

[0077] For commonly used flexible composite explosion-proof structure materials, such as PE, aramid and other composite fibers, in a limited space, a continuous winding protection structure is generally used, which can be approximately regarded as a continuous medium. For PE, its application in the field of bulletproof and explosion-proof generally uses PE raw silk, which is coupled with resin to form PE continuous fabric; PE continuous fabric is then formed into a protective structure through hot pressing, resin bonding, stacking packaging or continuous winding. For PE raw silk, it has very strong tensile strength, and its tensile strength is generally around 2 to 5Gpa. For PE cured resin, the strength is relatively low, and its tensile strength is generally around 20 to 40Mpa. It fails under the action of shock waves, which reduces the density of raw silk fibers, and the fibers are directly displaced and dislocated, resulting in cracking or fragmentation, thereby causing protection risks.

[0078] The typical flexible composite explosion-proof structure designed in step 1 is as follows Figure 4 In the four-layer structure shown, the first layer is an inner protective layer 1 , the second layer is an inner stress wave regulating layer 2 , the third layer is an outer protective layer 3 , and the fourth layer is an outer stress wave regulating layer 4 .

[0079] The inner protective layer 1 is made of high-performance fiber materials such as aramid and PE; it tries to use materials with good anti-elasticity, which can attenuate the speed of the bullet to the greatest extent in the first layer, and its thickness is smaller than that of the outer protective layer 2.

[0080] The second layer is the inner stress wave regulating layer 2, whose wave impedance is lower than that of the inner protective layer 1. At the same time, such a structure has a certain rigidity to ensure the uprightness of the structure. Preferably, a foam layer or a rubber layer with fiber strength can be used, which mainly plays a role in stress wave regulation, can reduce the peak value of the stress wave incident on the third layer, and avoid the outermost layer of the structure from being broken.

[0081] The third layer is the outer protective layer 3, which is the main bulletproof and explosion-proof layer. High-strength fibers such as aramid or PE can be used. It is required to have good bulletproof performance and good tear resistance. Its thickness is greater than that of the inner protective layer 1. It can attenuate the peak value of the stress wave incident to its outer layer boundary as much as possible during an explosion, thereby avoiding cracking and fragmentation of the outer layer.

[0082] The fourth layer is the outer stress wave regulating layer 4, which is mainly used to reduce the tearing of the outer protective layer 3 caused by the stress wave reflection loading, and at the same time has a certain supporting effect. Foam or rubber can be used. Rubber has good elasticity and can undergo large deformation without breaking. At the same time, the wave impedance of the foam or rubber layer used is lower than that of the outer protective layer 3, which reduces the intensity of the reflected stress wave.

[0083] Example Analysis 1:

[0084] Here is a single-layer flexible composite explosion-proof structure for analysis:

[0085] The explosion-proof structure is a single-layer 40mm thick protective structure formed by hot pressing, density stacking or continuous tight winding of PE fiber layers. The density of PE fiber material is 970kg / m 3 , the speed of sound is 5300m / s. According to general bulletproof design experience, a 40mm thick PE layer can achieve very good anti-fragmentation performance, but for shock wave protection, the following calculation is required:

[0086] For example, for the protection of 500g explosives, the distance from the explosives is 200mm. Through simulation or theoretical calculation, the shock wave pressure incident on the PE fiber protective layer is 20Mpa. Through simulation or experiment, the attenuation coefficient of the PE material is 0.0025 (kPa / mm). At the outermost boundary of the protective structure, considering the total reflection of the stress wave at the boundary, we have:

[0087]

[0088] That is, through calculation, it is obtained that the stress wave is about 36Mpa in the outermost layer of the protective material. Therefore, when the material strength of the single-layer explosion-proof structure is lower than 36Mpa, there is a certain risk of damage; and the resin strength of general PE fiber may be lower than 36Mpa, which will cause the outermost layer of the protective structure to crack and break.

[0089] Furthermore, if the thickness of the explosion-proof structure is increased and a 60 mm thick fiber layer is used, then:

[0090]

[0091] It can be seen that increasing the thickness by 20 mm does not significantly improve the anti-crushing ability of the structure. Therefore, flexible composite explosion-proof structures generally adopt multi-layer structures.

[0092] Example Analysis 2:

[0093] The explosion-proof structure adopts double-layer fiber. The first layer (i.e. inner layer) is made of 20mm thick aramid fiber, and the second layer (i.e. outer layer) is made of 20mm thick PE. The density of aramid fiber is 1650kg / m 3 , the speed of sound is 2860m / s, the attenuation coefficient is 0.0035 (kPa / mm), and the density of PE is 970kg / m 3 , the speed of sound is 5300m / s, and the PE attenuation coefficient is 0.0025 (kPa / mm).

[0094] Similarly, if the shock wave pressure incident on the first layer is 20 MPa, then at the outermost side of the second layer, considering that the stress wave is reflected at the boundary, we have:

[0095]

[0096] Through calculation, it is found that the shock wave pressure of the outermost layer of the explosion-proof structure is 34Mpa. When the strength of the outermost layer material is lower than 34Mpa, there is a certain risk of damage. This double-layer structure has improved explosion-proof performance to a certain extent compared with the single-layer structure, but the improvement is not large. The resin strength of general PE fiber may be lower than 30Mpa, which will cause the outermost layer of the protective structure to crack and break.

[0097] Example Analysis 3:

[0098] The explosion-proof structure adopts a three-layer structure. The first layer (i.e. the inner layer) is a 10mm thick PE protective layer; the second layer (i.e. the middle layer) is a 10mm rubber material, which is a stress wave adjustment layer; the third layer (i.e. the outermost layer) is a 10mm thick PE protective layer. The density of PE is 970kg / m 3 , the speed of sound is 5300m / s, the PE attenuation coefficient is 0.0025 (kPa / mm), and the density of the rubber material is 1000kg / m 3 , the speed of sound is 640m / s, and the attenuation coefficient of rubber is 0.0112 (kPa / mm).

[0099] Similarly, if the shock wave pressure incident on the first layer is 20 MPa, then at the outermost side of the third layer, considering that the stress wave is reflected at the boundary, we have:

[0100]

[0101] Through calculation, it is found that the shock wave pressure of the shock wave in the outermost layer of the explosion-proof structure is 15.5Mpa. General resins can achieve this kind of strength. This three-layer structure has good protective performance.

[0102] Example Analysis 4:

[0103] The explosion-proof structure adopts a four-layer structure. The first layer is used as the inner protection layer, which is made of 10mm thick PE fiber material. The second layer is the stress wave adjustment layer, which is made of 10mm thick rubber material. The third layer is used as the outer protection layer, which is made of 30mm thick PE material. The fourth layer is the stress wave adjustment layer, which is made of 5mm thick rubber material. The density of PE fiber material is 970kg / m 3 , the speed of sound is 5300m / s, the attenuation coefficient of PE fiber material is 0.0025 (kPa / mm), and the density of rubber material is 1000kg / m 3, the speed of sound is 640m / s, and the attenuation coefficient of rubber is 0.0112 (kPa / mm).

[0104] Similarly, considering that the pressure of the shock wave incident on the first layer is 20Mpa, then in the outermost layer of the stress wave adjustment layer, considering that the stress wave is reflected at the boundary, we have:

[0105]

[0106] Through calculation, it is found that the shock wave pressure of the shock wave on the outermost layer of the explosion-proof structure is 2.7Mpa, which can reach the tear resistance strength of general rubber. Furthermore, after the stress wave is reflected by the outermost layer, the stress wave incident on the third layer again is:

[0107]

[0108] It can be seen that the four-layer structure can better prevent the structure from breaking. The stress wave of the outermost layer is less than 3Mpa, and the stress wave of the third layer is 4.5Mpa. General resins can achieve this strength. The designed protective structure can greatly improve the protection performance against explosion and crushing while meeting the bulletproof performance.

[0109] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. The design method of non-fragmentation explosion-proof structure is characterized by: Used to ensure that the outermost layer of the explosion-proof structure does not break; the explosion-proof structure is a composite explosion-proof structure; Step 1: Design the explosion-proof structure to obtain the number of layers, protective materials used for each layer, and thickness of each layer; Step 2: Calculate the attenuation coefficient of the shock wave in each layer of the designed explosion-proof structure; Step 3: Calculate the peak value of the stress wave when the shock wave acts on the outermost structural boundary of the explosion-proof structure; Step 4: Determine whether the strength of the outermost structural material is greater than the peak value of the stress wave of the shock wave at the outermost structural boundary of the explosion-proof structure calculated in step 3; If it is greater than, it is considered that the outermost structure will not be broken, and the current explosion-proof structure is regarded as a non-fragmentation explosion-proof structure; If it is not greater than, it is considered that the outermost structure will be broken, and the explosion-proof structure should be redesigned and the peak value of the stress wave at the boundary of the outermost structure when the shock wave acts on it should be recalculated until the outermost structure will not be broken; According to the protection equivalent and protection distance of the designed explosion-proof structure, the intensity of the shock wave incident on the protection structure is first calculated, and then the peak value of the stress wave of the outermost structure of the flexible explosion-proof structure is further calculated; The explosion-proof structure has n layers, and the first layer, the second layer, ... the nth layer are arranged from the explosion-facing surface to the back explosion surface of the explosion-proof structure; Then the peak value of the stress wave at the outermost structure boundary of the explosion-proof structure is for: Where: P0 is the intensity of the shock wave incident on the first layer of the structure; K i is the wave impedance of the material used in the i-th layer structure; x i is the thickness of the i-th layer structure, α i is the attenuation coefficient of the i-th layer structure; When the explosion-proof structure needs to be redesigned, the arrangement of each layer is modified or the number of layers of the explosion-proof structure is increased and / or the thickness of one or more layers of protective material in the explosion-proof structure is increased and / or the type of one or more layers of protective material is changed.

2. Non-fragmentation explosion-proof structure, characterized by: The explosion-proof structure adopts the design method described in claim 1; The explosion-proof structure is at least a three-layer structure, and the strength of the outermost layer of the structural material is greater than the peak value of the stress wave of the shock wave at the outermost layer of the explosion-proof structure.

3. The non-fragmentation explosion-proof structure according to claim 2, characterized in that: The explosion-proof structure is a three-layer structure, the first layer is an inner protective layer, the second layer is a stress wave adjustment layer, and the third layer is an outer protective layer; The inner protective layer and the outer protective layer are made of bulletproof fiber, and the stress wave adjustment layer is made of a material with a wave impedance lower than that of the bulletproof fiber; The material strength of the outer protective layer is greater than the stress wave peak value of the shock wave at the boundary of the outer protective layer.

4. The non-fragmentation explosion-proof structure according to claim 3, characterized in that: The stress wave adjustment layer is a foam layer or a rubber layer with fiber strength.

5. The non-fragmentation explosion-proof structure according to claim 2, characterized in that: The explosion-proof structure is a four-layer structure, the first layer is an inner protective layer, the second layer is an inner stress wave regulating layer, the third layer is an outer protective layer, and the fourth layer is an outer stress wave regulating layer; The inner protective layer and the outer protective layer are made of bulletproof fiber, and the inner stress wave regulating layer and the outer stress wave regulating layer are made of materials with lower wave impedance than the bulletproof fiber; The material strength of the outer protective layer is greater than the stress wave peak value of the shock wave at the boundary of the outer protective layer.

6. The non-fragmentation explosion-proof structure according to claim 5, characterized in that: The inner stress wave regulating layer and the outer stress wave regulating layer are both foam layers or rubber layers with fiber strength.

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