Lightweight design method for protective cover of linear separation device

Abstract

The invention provides a lightweight design method for a protective cover of a linear separation device, the protective cover is provided with a charging groove, and the lightweight design method comprises the following steps: selecting a material of the protective cover by considering quasi-static mechanical properties and dynamic mechanical properties; the size of a connecting hole of an external connector of the protective cover and the thickness of the connecting position are designed according to the explosive loading amount in the explosive loading groove; the appearance of the protective cover around the charging groove is optimized according to detonation waves generated when the charged powder in the charging groove is detonated; and / or the connection between the protection cover and the separation component is designed into a simple support structure according to the stress direction, the action form and the main bearing position of the structure.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft structure technology, and the design technology is applicable to the protective cover of linear separation devices such as flexible detonating cord separation devices and shaped charge cutting cord separation devices. Background Technology

[0002] The structure of the flexible detonating cord and shaped charge cutting cord separation device is as follows: Figure 1 As shown, it mainly includes separation components, protective covers, connectors, and pyrotechnics (shaped charge cables or flexible cables). It has advantages such as good separation synchronization, reliable operation, light structural weight, and ease of bending into various shapes. Currently, flexible detonating cords and shaped charge cutting cords are widely used in the multi-stage separation of space launch vehicles; shaped charge cutting cords are also used in missile self-destruction systems, cutting various materials in emergency escape systems, and other applications.

[0003] With the increasing urgency of equipment lightweighting, it is necessary to reduce structural weight through design optimization without affecting equipment performance, thereby effectively reducing launch costs and increasing design flexibility. Flexible detonating cords, as important inter-stage linear separation devices in rockets, have always had separation performance as a key focus of structural design research. Current research on flexible detonating cord devices mainly includes calculating the critical charge of the flexible detonating cord, shock reduction design, and load-bearing capacity verification. However, research on lightweight design of flexible detonating cords is limited, and no relevant guidelines for lightweight design of flexible detonating cords have yet been developed. Summary of the Invention

[0004] The technical problem solved by this invention is: starting from the lightweight design of the flexible detonating cord separation structure, focusing on the optimized design and selection of the protective cover and fastening structure in the detonating cord, and achieving a lightweight design of the separation structure while maintaining separation performance.

[0005] The solution of this invention is: a lightweight design method for a protective cover of a linear separation device, wherein the protective cover is provided with a loading tank, including:

[0006] Considering both quasi-static and dynamic mechanical properties, select the material for the protective cover;

[0007] The size of the connection hole and the thickness of the connection point of the protective cover to the external interface are designed according to the amount of medicine in the medicine tank.

[0008] The shape of the protective cover around the charge tank is optimized based on the detonation wave generated when the charge is detonated in the charge tank; and / or the connection between the protective cover and the separation component is designed as a simply supported structure based on the direction of structural force, the mode of action, and the main load-bearing location.

[0009] Preferably, it includes aluminum alloy plates and forgings, including 7050-T7451 plates, 7A65, 2024 or 2024HDT-T351, 2A14 annealed or T4 plates, 6061T6 or T651 plates or forgings.

[0010] Preferably, the protective cover is made of a composite material, which is a composite material formed by molding or injection molding of a fiberglass cloth layer, 2.5D glass fiber, aramid fiber, Kevlar or PBO fiber woven structure, and epoxy resin or other types of resin with good toughness.

[0011] Preferably, the protective cover is made of a sandwich material. Utilizing the principle of impedance mismatch during wave propagation, a sandwich structure with a large density difference is employed to impede the transmission of the blast wave. Examples include steel-magnesium-steel, steel-aluminum-steel, steel-carbon fiber composite-steel, and aluminum-air-aluminum, where two adjacent materials... The larger the value, the more likely the impedance ratio is to be greater than 4 (the larger impedance ratio is the numerator, and the smaller impedance ratio is the denominator), the less smooth the wave transmission will be; or an interlayer compressible sandwich structure can be used, such as steel-aluminum foam-steel, carbon fiber composite-negative Poisson's ratio structure-aluminum alloy, and the sandwich layer can be made of low density, loose aluminum foam, aluminum honeycomb or negative Poisson's ratio structure, etc., which can cause the structure to undergo local deformation when subjected to pressure, absorb and dissipate the detonation energy, and ultimately remain unbroken and undamaged at a location far away from the pyrotechnics.

[0012] Preferably, the interlayer compressible sandwich structure includes an inner skin, a middle skin, and an outer skin, as well as a core disposed between the skins; the skin is made of carbon fiber, aluminum alloy, magnesium alloy, or steel, and the core is a low-density or loose structure such as aluminum honeycomb, aluminum foam, or negative Poisson's ratio structure.

[0013] Preferably, the shape of the protective cover around the charge tank is optimized to be of equal thickness with the charge tank as the center.

[0014] Preferably, when the separate components can participate in the optimized design, the stress form of the protective cover can be changed from a cantilever beam to a simply supported beam.

[0015] Preferably, when the charge in the charging tank is less than 3.0 g / m, the thickness of the equal-thickness design is ≥6 mm; when the charge is 3.0 to 4.0 g / m, the thickness is ≥8 mm; when the charge is greater than 4.0 g / m, a shaped charge cutting cable is generally used as the pyrotechnic device, with a thickness ≥8 mm. The specific thickness needs to be determined separately based on the actual charge.

[0016] Preferably, for a charge amount less than 3.0 g / m, steel bolts with a diameter of 5 or 6 mm are used to connect the external interface to the separation component; for a charge amount of 3.0 to 4.0 g / m, steel bolts with a diameter of 6 or 8 mm are used; and for a charge amount greater than 4.0 g / m, steel bolts with a diameter of ≥8 mm are used. The specific method needs to be determined separately based on the actual charge amount.

[0017] Preferably, at the non-connection hole of the mating interface, the material is thinned or hollowed out in a direction perpendicular to the cross-section.

[0018] The protective cover of the linear separation device has a lightweight structure, and the protective cover is provided with a charging slot, including a charging structure and an external interface;

[0019] The external interface is connected to the separation component by fasteners; the charge structure is a sandwich structure including an inner skin, a middle skin, and an outer skin, as well as a core disposed between the skins; the skin is made of carbon fiber, aluminum alloy, or magnesium alloy, and the core is made of aluminum honeycomb, aluminum foam, or negative Poisson's ratio structure; the external interface is a radial connection interface or an axial connection interface; the charge structure is designed with the charge groove as the center of equal thickness or forms a simply supported connection structure with the separation component.

[0020] The advantages of this invention compared to the prior art are:

[0021] This invention overcomes the design technology of multi-layer materials for protective covers. It utilizes the principle of impedance mismatch during wave propagation and adopts a sandwich structure with large density differences to impede the transmission of the detonation wave. Alternatively, it adopts a compressible sandwich structure between layers to allow the structure to undergo local deformation without breaking when subjected to pressure, thereby dissipating the detonation energy. Under the premise of meeting all performance requirements, the weight is reduced by about 10%.

[0022] This invention overcomes the design technology of the connection between the protective cover and the shell, and proposes to analyze the protective cover under the action of detonation using the static load-bearing stress method. It found that the load-bearing efficiency of the simply supported structure is higher than that of the cantilever structure, and improved the structural design of the protective cover. At the same time, it was found that the stress condition of the non-bolted connection is better, and it can be appropriately thinned or hollowed out to further reduce the mass in the direction perpendicular to the cross section, reducing the weight by about 15%. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the function of the flexible detonating cord / shaped charge cutting cord separation device.

[0024] Figure 2 This is a schematic diagram of the cross-sectional structure of the protective cover;

[0025] Figure 3 This is a schematic diagram of an interlayer compressible sandwich structure.

[0026] Figure 4 Schematic diagram of the semi-circular configuration for the explosive charge position of the protective shield.

[0027] Figure 5 For the connection between the protective cover and the nearby structure;

[0028] Figure 6 A diagram showing the structural comparison of the protective cover before and after optimization;

[0029] Figure 7 This is a diagram illustrating "reduction" at a non-stressed location.

[0030] Figure 8 Comparison of before and after photos of three multilayer material design schemes;

[0031] Figure 9 This is a diagram illustrating the comparison results of the three options. Detailed Implementation

[0032] The present invention will be further described below with reference to the embodiments.

[0033] The protective cover for the flexible detonating cord and shaped charge cutting cord separation device involved in this invention has three main functions:

[0034] 1. The protective cover must not break when the high-temperature and high-pressure gas and detonation wave generated by the internal pyrotechnics are in operation, so as to protect the instruments and equipment inside the cabin from damage.

[0035] 2. The protective cover must not be deformed significantly and must maintain a small space during the working time of the pyrotechnic device to prevent high pressure leakage from affecting the separation margin;

[0036] 3. Fix the position of the pyrotechnic device to ensure it functions effectively and has good environmental adaptability. This is illustrated in the basic structural outline of the protective cover. Figure 2 It has a charge tank, connection holes, a certain thickness in structure, and materials with a certain resistance to explosive impact.

[0037] Figure 2 In the process, a flexible detonating cord or shaped charge cutting cord is placed inside the charging tank. Its dimensions should match the dimensions of the pyrotechnic device. The connection hole is used for connecting the protective cover and the separation component, and its dimensions should match the fasteners. With these two parts' dimensions basically determined, the following section mainly introduces the design and selection methods for the protective cover's material, structural shape, and dimensions.

[0038] Both flexible detonating cord and shaped charge cutting cord are high-explosive pyrotechnic devices, containing powerful explosives with detonation velocities reaching 7000–8000 m / s. They have short operating times and high output power, belonging to the ultra-high-speed pyrotechnic type. The protective cover does not break or deform significantly when subjected to ultra-high-speed impacts.

[0039] In summary, the basic steps in designing a protective cover are as follows:

[0040] Step 1: Material Selection. Choose materials with relatively low density from commonly used load-bearing structures, taking into account both quasi-static and dynamic mechanical properties. Specifically:

[0041] 1. Single-element materials, aluminum alloy plates and forgings, with a density of approximately 2.8 g / m³, are lighter than steel and titanium alloys; compared to casting processes, they have fewer internal defects; choose heat treatment states with good toughness and high elongation to withstand large deformations without fracture, such as O-state, annealed state, T4 state, etc. At the same time, pay attention to the material having good impact toughness and minimal strain rate effect. For example: 7050-T7451 plates (tensile strength ≥510MPa, yield strength ≥441MPa, elongation ≥10%, fracture toughness LT direction ≥32), 7A65 (tensile strength ≥520MPa, yield strength ≥490MPa, elongation ≥11%, fracture toughness LT direction ≥43), 2024 or 2024HDT-T351 (tensile strength ≥450MPa, yield strength ≥340MPa, elongation ≥23%, fracture toughness LT direction ≥40). 2A14 annealed or T4 plate, 6061T6 or T651 plate or forging;

[0042] 2. Composite Material 1, Fiberglass. Density 1.8~2.0g / m³. Compared with carbon fiber lay-up and woven materials, it has lower strength but better toughness. A protective cover made of fiberglass cloth lay-up or 2.5D woven structure, and epoxy resin through molding or injection molding processes. Its performance indicators (tensile strength ≥300MPa, flexural strength ≥200MPa, impact toughness ≥200J / m²).

[0043] 3. Composite Material 2, Sandwich Material. During the propagation of the detonation wave generated by flexible detonating cords or shaped charge cutting cords, the principle of impedance mismatch during wave propagation can be utilized. A sandwich structure with significant density differences can be employed to hinder the propagation of the detonation wave. Alternatively, a compressible interlayer sandwich structure can be used, allowing the structure to undergo localized deformation without fracturing under pressure, thus dissipating the detonation energy. Figure 3 As shown. The outer / middle / inner skins can be made of lightweight materials such as carbon fiber plates, aluminum alloys, and magnesium alloys. The materials for sandwich 1 and sandwich 2 can be aluminum honeycomb, aluminum foam, or negative Poisson's ratio structures. The thickness of the skin, the strength and dimensions of the sandwich structure are matched to the explosive impact.

[0044] Following the design method in step one, a lightweight protective cover that meets the performance requirements can be designed from the perspective of material selection.

[0045] Step two, shape optimization design. The pyrotechnic device placed inside the protective shield is circular or U-shaped. During operation, the detonation wave on one side of the protective shield propagates outward in an approximately semi-circular pattern from the pyrotechnic device as the center, and the pressure is the same at equidistant locations from the pyrotechnic device. Therefore, the protective shield design generally adopts a design with a uniform thickness centered on the charge tank as a relatively reasonable and optimized solution. The thickness value is determined by the material's resistance to explosive impact and the amount of charge. Figure 4 As shown. Generally, the thickness should be ≥6mm for charge amounts less than 3.0g / m, ≥8mm for charge amounts of 3.0~4.0g / m, and the thickness should be increased according to the specific design for charge amounts greater than 4.0g / m.

[0046] Step two involves optimizing the design of the loading tank section to reduce the cross-sectional area of ​​the protective cover structure, thereby reducing its weight.

[0047] Step 3: External Interface Design. The protective cover needs to be connected to the shell structure. Its function is to ensure a good installation environment for pyrotechnics during transportation and flight, while maintaining a stable connection under the impact of an explosion. The design should exhibit no overall velocity, minimal local displacement, and no excess material buildup, thus protecting the equipment and instruments inside the cabin and preventing sudden pressure release that could affect separation performance. Therefore, in addition to the approximately semi-circular structure, an additional structure is needed for reliable connection; that is, an additional structure near the connection hole is required. See [link to relevant section]. Figure 5 The size of the connecting hole and the thickness of the connection are related to the charge amount. Generally speaking, steel bolts with a diameter of 5 or 6 mm are used for charges less than 3.0 g / m, steel bolts with a diameter of 6 or 8 mm are used for charges of 3.0 to 4.0 g / m, and the size is increased according to the specific design requirements for charges greater than 4.0 g / m.

[0048] Step three achieves a stable connection between the protective cover and the adjacent structure.

[0049] Step four, structural optimization design. After ensuring the protective cover's own structural design meets usage requirements, further optimization of the overall protective cover structure, as well as its compatibility with adjacent structures, is carried out. For example... Figure 6 As shown, the protective cover and the separation shell are connected together by bolts. When subjected to the detonation of the internal explosive charge, analysis of the structural force direction, action mode, and main load-bearing locations shows that the simply supported structure has a higher load-bearing efficiency than the cantilever structure. Weight reduction can be achieved by improving the structure along with nearby structures. This method and the second step... Figure 4 The optimized design allows you to choose one of the two options.

[0050] Furthermore, the stress condition at non-bolted joints (i.e., the area between any two bolts) is not severe, and the joints can be appropriately thinned or hollowed out to further reduce mass in the direction perpendicular to the cross-section, such as... Figure 7 As shown. This item describes the optimized design method for the protective cover and related structures.

[0051] Step four: Through stress analysis, the entire assembly was optimized, further reducing its weight.

[0052] The specific design process of this invention is not limited to the specific operational sequence of the above steps, as long as the final objective can be achieved by following the description of this invention.

[0053] Flexible detonating cords and shaped charge cutting cords are widely used in multi-stage separation of space launch vehicles. Shaped charge cutting cords are also used for missile self-destruction, cutting various materials in emergency escape systems, and other applications. Their reliability affects the overall implementation of the project. The applicant conducted extensive research and testing to develop the aforementioned technical solution. A brief description of some of the research results is provided below. Note: According to national military standards, the separation performance (separation can be achieved with 67% of the designed charge) and structural strength (the remaining structure is intact except for the separation surface) of the aerospace pyrotechnic separation device must simultaneously meet the requirements. Relevant tests were conducted according to national military standards.

[0054] Result 1: The selection of the protective cover's single-element material and the optimization design of its structural shape were partly conducted using simulation analysis and partly using experimental verification. The results show that, without significantly affecting separation performance and structural strength, the overall weight reduction of the separation device is no less than 10%.

[0055] During the optimization of the protective shield dimensions, the effects of reducing the average thickness of the protective shield and the "semi-circular" configuration on the critical charge were investigated. Simultaneously, the change in the shield stiffness after dimensional adjustment was calculated to explore the factors influencing the critical charge of the protective shield. Finally, the strength of the protective shield under high charge conditions was verified. Analysis / experimental results show that reducing the shield thickness and the "semi-circular" configuration within a certain range can effectively reduce the weight of the protective shield while simultaneously meeting both separation performance and structural strength requirements.

[0056] Effect 2: The multilayer material design technology was tested and verified. The results show that, without significantly affecting separation performance and structural strength, the overall weight reduction of the separation device is no less than 10%.

[0057] Three different multilayer material design schemes were developed: Scheme 1, "carbon fiber panel-aluminum honeycomb-carbon fiber panel-aluminum honeycomb-carbon fiber panel"; Scheme 2, "steel-aluminum honeycomb-copper-aluminum honeycomb-fiberglass cloth"; and Scheme 3, "aluminum alloy panel-aluminum honeycomb-aluminum plate". Experimental verification was completed, and the results are as follows: Figure 8As shown. After testing with Scheme 1 and Scheme 3 (120% of the design charge), the external structure remained intact, with no large displacement or overturning, no excess material, and the structural strength met the requirements. The structure tested with the small charge (67% of the design charge) could perform normal separation function tests. Scheme 2 had significant excess material and is not recommended.

[0058] Note: Considering the ease of processing aluminum honeycomb sandwich material and the main purpose of this experiment (to verify the effectiveness of the sandwich structure protective cover design), the protective cover in this experiment adopts a simple linear shape (not a semi-circular shape).

[0059] Effect 3: The optimized design technology for the protective cover and related structures was carried out using a combination of simulation analysis and experimental verification. The results show that, without significantly affecting separation performance and structural strength, the overall weight reduction of the separation device is no less than 15%.

[0060] When the protective shield is subjected to detonation, analysis of the structural force direction, action mode, and main load-bearing locations shows that the simply supported structure has a higher load-bearing efficiency than the cantilever structure. Furthermore, the stress condition at non-bolted connections is better, allowing for appropriate thinning or hollowing out to further reduce mass in the direction perpendicular to the cross-section. After the high-charge (120% design charge) test, the structure remained intact, with no large displacement or overturning, no excess material, and the structural strength met the requirements. The structure was able to perform normal separation function tests during the low-charge (67% design charge) test. Figure 9 The three schemes presented represent the parameter adjustment process in the weight reduction design after the cantilever was changed to a simply supported structure. Scheme 2 is the final design result, while the structural strength in Scheme 3 no longer meets the requirements.

[0061] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A lightweight design method for a protective cover of a linear separation device, wherein the protective cover is provided with a loading tank, characterized in that... include: Considering both quasi-static and dynamic mechanical properties, select the material for the protective cover; The size of the connection hole and the thickness of the connection point of the protective cover to the external interface are designed according to the amount of medicine in the medicine tank. The shape of the protective cover around the charge tank is optimized based on the detonation wave generated when the charge is detonated in the charge tank. The connection between the protective cover and the separation component is designed as a simply supported structure based on the direction of structural forces, the form of action, and the location of the main loads.

2. The method according to claim 1, characterized in that: The protective cover is made of a single material, including aluminum alloy plates and forgings, including 7050-T7451 plates, 7A65, 2024 or 2024HDT-T351, 2A14 annealed or T4 plates, 6061T6 or T651 plates or forgings.

3. The method according to claim 1, characterized in that: The protective cover is made of composite material, which is a composite material formed by molding or injection molding of glass cloth, 2.5D glass fiber, aramid fiber, Kevlar or PBO fiber woven structure, and epoxy resin or other types of resin with good toughness.

4. The method according to claim 1, characterized in that: The protective cover is made of a sandwich material. Based on the principle of impedance mismatch during wave propagation, a sandwich structure with large density differences is used to impede the transmission of the blast wave. It is recommended that the impedance ratio of the two adjacent materials be greater than 4; or a compressible sandwich structure between the layers is used so that the structure undergoes local deformation when subjected to pressure, absorbing and dissipating the blast energy, and ultimately not breaking or being damaged at a location far away from the pyrotechnics.

5. The method according to claim 1, characterized in that: The interlayer compressible sandwich structure includes an inner skin, a middle skin, and an outer skin, as well as a core sandwiched between the skins; the skin is made of carbon fiber, aluminum alloy, or steel, and the core is a low-density or loose structure such as aluminum honeycomb, aluminum foam, or negative Poisson's ratio structure.

6. The method according to claim 1, characterized in that: The shape of the protective cover around the charge tank has been optimized to a design with the charge tank as the center and the thickness equal.

7. The method according to claim 6, characterized in that: When the charge in the charging tank is less than 3.0 g / m, the thickness of the equal-thickness design should be ≥6 mm. When the charge is 3.0 to 4.0 g / m, the thickness should be ≥8 mm. When the charge is greater than 4.0 g / m, a shaped charge cutting cable should be used as the pyrotechnic device with a thickness ≥8 mm. The specific thickness needs to be determined separately based on the actual charge.

8. The method according to claim 1, characterized in that: When separate components are involved in the optimization design, the stress form of the protective cover is changed from a cantilever beam to a simply supported beam.

9. The method according to claim 1, characterized in that: For charges less than 3.0 g / m, steel bolts with a diameter of 5 or 6 mm are used to connect the external interface to the separation component. For charges of 3.0 to 4.0 g / m, steel bolts with a diameter of 6 or 8 mm are used. For charges greater than 4.0 g / m, steel bolts with a diameter of ≥8 mm are used. The specific amount to be determined based on the actual charge quantity.

10. A lightweight structure for the protective cover of a linear separation device, wherein a loading tank is provided on the protective cover, characterized in that: Including the propellant loading structure and external interfaces; The external interface is connected to the separation component by fasteners; the charge structure is a sandwich structure including an inner skin, a middle skin, and an outer skin, as well as a core disposed between the skins; the skin is made of carbon fiber, aluminum alloy, or magnesium alloy, and the core is made of aluminum honeycomb, aluminum foam, or negative Poisson's ratio structure; the external interface is a radial connection interface or an axial connection interface; the charge structure is designed with the charge groove as the center of equal thickness or forms a simply supported connection structure with the separation component.

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