Functional gradient buffer structure for high-speed water entry of cross-medium navigation body

Abstract

The invention discloses a functional gradient buffer structure suitable for a high-speed water entry process of a cross-medium navigation body, and aims to effectively improve the structural safety and integrity of the navigation body when the navigation body bears a high impact load. The structure mainly comprises a pointed arch-cylinder combined housing, a functional gradient buffer layer and a locking device. Wherein the functional gradient buffer layer is formed by sequentially and tightly attaching high-density (200kg / m < 3 >) rigid polyurethane foam, medium-density (100kg / m < 3 >) rigid polyurethane foam and low-density (50kg / m < 3 >) rigid polyurethane foam, a filling structure with gradually-decreased density is formed in the axial direction, the functional gradient buffer layer is arranged in a cavity between the housing and the navigation body, and the low-density layer is close to the head of the navigation body. The locking device achieves axial limiting and anti-falling fixing of the housing through an annular structure. Under the condition of 100 m / s vertical entry water impact, numerical simulation analysis shows that the structure can reduce the peak value of the impact load coefficient borne by the navigation body to 0.88, and compared with a single-layer buffer structure with the same volume density (100 kg / m < 3 >), the impact load coefficient of the structure is reduced by 27.3%.

Description

Technical Field

[0001] This invention relates to the protective design of the hull structure for high-speed water entry of cross-medium vehicles, and more particularly to a functional gradient buffer structure for cross-medium vehicles. Background Technology

[0002] As a major maritime power, my country possesses a long coastline and abundant marine resources. To better safeguard national maritime sovereignty, it is imperative to strengthen the monitoring and response capabilities against maritime and underwater intrusions. However, most current vessels can only operate in a single-medium environment, such as land, air, surface, underwater, or space. With the development of military strategic needs and technology, vessels capable of performing tasks such as target engagement, information monitoring, and situational awareness in a single medium are gradually showing their limitations. Therefore, cross-medium navigation systems capable of freely switching between multiple media (such as water and air) urgently need to be developed.

[0003] The water entry process, as one of the key technical challenges in the design of cross-medium navigation vehicles, has attracted widespread attention. Due to the significant density difference between air and water, when a vehicle impacts a free liquid surface with a certain initial velocity and crosses the air-water interface, its nose will generate impact loads characterized by strong transient, unsteady, and high intensity. Under high-speed water entry conditions, the vehicle structure may experience localized fractures due to significant deformation, or even lead to overall structural failure. Therefore, how to effectively reduce the impact load on the vehicle while ensuring its structural integrity and mission performance has become a critical issue affecting the safety and reliability of cross-medium navigation. Summary of the Invention

[0004] Purpose of the invention:

[0005] The technical problem this invention aims to solve is to overcome the shortcomings of existing single-density buffer structures in high-speed water entry scenarios for cross-medium vessels, such as insufficient energy absorption efficiency and uneven stress distribution. It provides a buffer structure with functionally graded characteristics, which significantly improves impact energy absorption capacity and load distribution uniformity under the same mass conditions, effectively protecting the structural integrity of the vessel.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a functional gradient buffer structure for high-speed water entry of a cross-medium vehicle, characterized by comprising: a shell (1), which adopts a shell structure combining a pointed arched head and a cylindrical tail, used to tightly cover the head of the vehicle to ensure aerodynamic stability during flight; and a functional gradient buffer layer, disposed in the cavity between the shell (1) and the vehicle (6), composed of a density of 200 kg / m³. 3 High-density cushioning material (2), with a density of 100 kg / m³ 3Medium-density cushioning material (3) and a density of 50 kg / m³ 3 The low-density buffer material (4) is tightly bonded together along the head to the tail of the aircraft body to form a gradient distribution with continuously decreasing density; the locking device (5) is installed at the tail of the cover (1), adopts a ring structure and the inner diameter matches the outer diameter of the aircraft body, and is used to accurately fix the axial position of the cover and prevent it from falling off during flight.

[0008] The gradient buffer materials (2), (3), and (4) are made of rigid polyurethane foam (generated by the reaction of polyol and isocyanate), which has a closed-cell structure and oleophilic and hydrophobic properties. The buffer materials are seamlessly and tightly bonded to each other and there is no adhesive at the interface, forming a gapless buffer layer as a whole.

[0009] The low-density buffer material (4) is in direct contact with the head of the aircraft (6), and the high-density buffer material (2) is located on the outermost side and closely attached to the inner wall of the shell (1).

[0010] The locking device (5) adopts a ring structure, and its base material is unsaturated polyurethane resin. The failure mode is brittle fracture. The inner diameter of the device matches the outer diameter of the naval body to realize the mechanical connection between the cover and the naval body, and is used to realize the limiting and fixing functions.

[0011] Compared to traditional single-density buffer structures, this invention has the following outstanding advantages:

[0012] 1. Staged energy absorption for enhanced efficiency, achieving 200kg / m³ 3 →100kg / m 3 →50kg / m 3 The density gradient design enables the gradual dissipation of impact energy. The high-density layer breaks and absorbs the initial impact energy, the medium-density layer gradually attenuates the energy, and the low-density layer softens and transfers the remaining load, thereby improving the overall energy absorption efficiency.

[0013] 2. Stress distribution optimization and gradient structure effectively smooth stress wave propagation, effectively reducing peak stress and avoiding stress concentration that could cause the nose of the aircraft to crush.

[0014] 3. Lightweight and high performance are combined. While keeping the total mass of the buffer structure unchanged, the energy absorption ratio per unit mass is significantly improved, directly supporting the lightweight design requirements of the aircraft body. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall installation of the functional gradient buffer structure.

[0016] Figure 2 This is a longitudinal cross-sectional view of the present invention along axis AA.

[0017] Figure 3This is a comparison curve of the vertical water impact load coefficient of the present invention. Detailed Implementation

[0018] To make the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] like Figure 1 The diagram shows an overall schematic of a functional gradient buffer structure for high-speed water entry of a transmedium-based vehicle. As can be seen, under the action of the locking device, the casing can completely enclose the head of the vehicle. The diameter D1 of the transmedium-based vehicle is 324 mm, and the overall length L1 is 1170 mm. The casing adopts a pointed arch structure to ensure good aerodynamic shape during flight. K1 represents the curvature of the outermost pointed arch of the casing, which in this embodiment is 2.29 × 10⁻⁶. - 3 mm -1 .

[0020] like Figure 2 The figure shows a schematic diagram of the AA cross-sectional structure of a functional gradient buffer structure for high-speed water entry of a cross-medium vehicle. As can be seen from the figure, the shell (1) adopts a uniform thickness shell structure with a thickness of 3 mm. Buffer materials (2), (3), and (4) fill the cavity area between the shell and the vehicle, together forming a functional gradient buffer layer. The buffer material is rigid polyurethane foam with an overall average density of 100 kg / m³. 3 The layers are arranged in a decreasing density pattern, with the first layer being a high-density buffer material (2) with a density of 200 kg / m³. 3 The second layer is a medium-density cushioning material (3), with a density of 100 kg / m³. 3 The third layer is a low-density cushioning material (4), with a density of 50 kg / m³. 3 The total length L2 of the gradient buffer material is 250mm, and the total mass is 0.926kg. The hull (6) is an aluminum alloy shell structure of equal thickness, with a shell thickness of 10mm and an overall length L3 of 900mm.

[0021] like Figure 3 As shown, the performance of the functional gradient buffer structure proposed in this invention for high-speed water entry of cross-medium vehicles was simulated and verified, and its response under impact load was compared with that of a single-density buffer structure. To more intuitively compare the impact loads experienced by the vehicle, a dimensionless parameter C was introduced. p As the impact load factor of the aircraft body, its definition is as follows:

[0022]

[0023] Where m represents the mass of the vehicle, a represents the acceleration of the vehicle, ρ represents the density of water, r represents the radius of the vehicle, and v represents the entry velocity of the vehicle into the water, which is taken as 100 m / s in this simulation, and the entry angle is perpendicular to the water surface, that is, the angle between the velocity direction and the water surface is 90 degrees. Figure 3 It is evident that the functionally graded buffer structure employed in this invention exhibits significant advantages over single-density buffer structures in suppressing impact load coefficients. In the single-density case, C p The peak value is 1.21, while under the functionally graded buffer structure condition, C p The peak value was 0.88, a decrease of 27.3% compared to the peak value under the single-density condition. This result further demonstrates that the functionally graded buffer structure of the present invention exhibits a significant performance advantage in reducing impact loads.

[0024] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A functional gradient buffer structure for high-speed water entry of a cross-medium vehicle, characterized in that, include: The shell (1) has a combined pointed arch and cylindrical shell structure, used to tightly cover the transmedium vehicle (6); the functional gradient buffer layer is disposed in the cavity between the shell (1) and the transmedium vehicle (6), the functional gradient buffer layer is composed of buffer materials with decreasing density along the direction from the head to the tail of the vehicle, including a high-density buffer material (2), a medium-density buffer material (3) and a low-density buffer material (4) that are tightly bonded together in sequence, wherein the density of the high-density buffer material (2) is 200 kg / m³. 3 The density of the medium-density buffer material (3) is 100 kg / m³. 3 The density of the low-density buffer material (4) is 50 kg / m³. 3 ; and a locking device (5) is provided at the tail of the cover (1) for fixing the cover (1) to the transmedium vehicle (6) and preventing it from falling off during flight.

2. The functional gradient buffer structure for high-speed water entry of a cross-medium vehicle according to claim 1, characterized in that: The high-density cushioning material (2), medium-density cushioning material (3) and low-density cushioning material (4) are all rigid polyurethane foam materials.

3. The functional gradient buffer structure for high-speed water entry of a cross-medium vehicle according to claim 1, characterized in that: The high-density buffer material (2) and the medium-density buffer material (3) are tightly bonded together, and the medium-density buffer material (3) and the low-density buffer material (4) are tightly bonded together. The functional gradient buffer layer is seamless.

4. The functional gradient buffer structure for high-speed water entry of a cross-medium vehicle according to claim 1, characterized in that: The functional gradient buffer layer is in close contact with the inner wall of the shell (1), and the low-density buffer material (4) is in close contact with the head of the transmedium vehicle (6).

5. The functional gradient buffer structure for high-speed water entry of a cross-medium vehicle according to claim 1, characterized in that: The locking device (5) is a ring structure, and its inner diameter matches the outer diameter of the transmedium vehicle (6). The locking device (5) connects the cover (1) and the transmedium vehicle (6) respectively, and is used to limit the axial position of the cover (1) and fix it.

Images