Corner flexible connection structure and anti-explosion performance design method thereof

Abstract

The invention belongs to the technical field of machinery, and discloses a corner flexible connection structure anti-explosion design method and application thereof, and the scheme comprises the steps of box type cabin corner connection structure configuration design under the implosion effect; designing a flexible connection structure configuration of the corners of the box-type cabin under the implosion effect; box type cabin corner flexible connection structure dynamic response implosion test research; and researching the stress distribution and failure mechanism of the flexible connection structure at the corner of the box-type cabin. According to the method, a reasonable in-cabin explosion effect calculation model is established through a numerical simulation method, and the influences of different connection structure forms on the aspects of dynamic response, shock wave convergence effect, structure failure mode and the like are compared and analyzed, so that the anti-explosion advantages of various connection structures are evaluated.

Description

Technical Field

[0001] This invention belongs to, but is not limited to, the field of mechanical technology, and particularly relates to a corner flexible connection structure and its explosion-proof performance design method. Background Technology

[0002] With the escalating intensity of modern information warfare, countries worldwide are placing great emphasis on research into the damage effects of naval structures under explosive loads. As a crucial barrier against various strategic weapons, the performance of a ship's protective structure directly impacts its overall combat capability and survivability. Therefore, optimizing protective structure design to enhance ship survivability has always been a key focus for navies globally. Research into the dynamic response of compartment structures under internal explosive loads is of significant theoretical and practical importance for optimizing internal blast protection structures, improving compartment blast resistance, and enhancing the overall protection level of ships.

[0003] A similar disclosure is EP 1841670A2 “Explosive effect mitigated containers and enclosing devices”, which discloses an explosion mitigation structure, namely, covering or arranging energy-absorbing or cushioning materials (such as flexible linings, foams, fracturing layers, etc.) inside the container or shell to reduce the load transfer of the explosion impact on the shell structure.

[0004] In this approach, cushioning materials are used to absorb or disperse the energy of the shock wave, reducing the load applied to the structural metal shell and thus mitigating stress and deformation. The focus is on the use of linings, buffer layers, and compliant materials to enhance the container's or structure's resistance to damage under explosive conditions.

[0005] While this published content shares some common ground with the idea of ​​"arranging flexible or energy-absorbing structures at corners to improve explosion response," it does not specifically design flexible corner connection structures, nor does it involve systematic simulation and optimization of specific structural configurations such as "corner connection plates + foam filling." Furthermore, this document primarily emphasizes the overall arrangement of the buffer lining, rather than the softening design of local structural connections.

[0006] Closely related prior art: US20030106414A1 (“Blast-resistant cargo container”). This patent discloses a cargo container structure that uses flexible connecting members to connect the sidewalls, thereby absorbing energy in the event of an explosion through the membrane stress of the sidewalls and the bending / unfolding of the connecting members.

[0007] The existing technical problems include:

[0008] * The structure is mainly designed for flexible connection between the sidewalls and the connectors. The design of flexible structure for corners (corner connections) is not in-depth. The problems of pressure convergence, wavefront reflection and structural deformation concentration at the corners are not specifically controlled.

[0009] * Although a "non-frame structure + flexible connectors" approach is used to reduce pressure concentration and structural rigidity, it does not incorporate filling materials (such as metal foam or energy-absorbing foam) to achieve shock wave dissipation and structural deformation coordination.

[0010] * The lack of systematic numerical simulation studies on the geometric parameters of the connectors (such as the angle, thickness, and density of the filling material) and the explosion-air coupling response inside the cabin (including the interaction between explosion products, gas, and structure) makes it impossible to finely optimize the parameters of the corner flexible connection structure. Summary of the Invention

[0011] To address the problems existing in the prior art, this invention provides a method for designing an explosion-proof corner flexible connection structure and its application.

[0012] This invention is implemented as follows: a method for designing an explosion-proof corner flexible connection structure, the method comprising:

[0013] S1. Design of Corner Connection Structure for Box-Type Compartments under Implosion Effect: Based on ANSYS / LS-DYNA software, a numerical model of the dynamic response of a box-type compartment under implosion effect was established, and its reliability was verified by experimental data from the literature. By comparing and analyzing the dynamic response characteristics of box-type compartment structures with different connection structures under internal explosive loads, the blast resistance advantages of each connection structure were systematically evaluated. The pressure convergence level in the corner area of ​​compartments with different connection structures and its influence on the deformation / failure mode of the compartment were discussed in detail. The effect of changes in connection structure parameters on blast resistance was analyzed from the perspective of mechanical mechanism.

[0014] S2, Flexible Corner Connection Structure Design for Box-Type Compartment under Implosion Effect: Based on the optimization of blast-resistant connection structures, two innovative corner flexible connection structure schemes are proposed. The dynamic response characteristics of flexible connection structures and ordinary connection structures under internal explosive loads are systematically compared. Based on explicit dynamic numerical methods, the performance advantages of flexible connection structures in suppressing overall structural deformation and alleviating local stress concentration are comprehensively evaluated from the perspectives of structural dynamic response parameters, maximum deflection of the bulkhead, and strain at typical measuring points. Through parameter sensitivity analysis, the influence of the geometric configuration parameters of the flexible connection structure on the overall deformation of the compartment and the failure mode of the corner area is explored in depth.

[0015] S3, Dynamic Response Implosion Test Study of Flexible Corner Connection Structure of Box-Type Compartment: Based on analysis, design methods for foam-filled flat plate and foam-filled triangular flexible connection structures were developed. In-cabin explosion tests were conducted on these two flexible connection structures to further explore their blast resistance. The manufacturing sequence of the compartment was optimized to reduce welding deformation, and the layout and welding of the corner flexible connection structure were rationally designed. Furthermore, quasi-static pressure sensors, bidirectional strain gauges, and cameras were used to acquire in-cabin explosion loads, structural responses, and structural transients. Three-dimensional scanning technology was employed to reflect the structural deformation after the explosion. The dynamic response, failure modes, and blast resistance of the flexible corner connection structure were analyzed based on the test results.

[0016] S4. Stress Distribution and Failure Mechanism Study of Flexible Corner Connection Structures in Box-Type Compartments: Based on the in-cabin explosion test of flexible corner connection structures in box-type compartments, a numerical prediction model for flexible corner connection structures in box-type compartments was established. The damage effects of implosion on box-type compartment structures with different TNT charges and corner flexible connection structures were compared to analyze the structural deformation failure mechanism and the action mode of the connection structure. On the one hand, the dynamic response and evolution of deformation failure modes of the compartment structure under different TNT charges were compared laterally; on the other hand, the influence of different flexible connection structures on the deformation failure mechanism of the bulkhead structure was compared longitudinally. Furthermore, the plastic deformation saturation effect of the bulkhead of the flexible connection structure was analyzed by changing the TNT charge. The action mechanism of the connection structure and aluminum foam material on the bulkhead was analyzed through energy absorption characteristics.

[0017] Furthermore, the numerical model of the dynamic response of the box-shaped compartment adopts a boundary plate with a length of 1 / 5 L; a circular hole is preset at the center of the top wall of the compartment as a vent to simulate the mechanical behavior of an anti-ship missile penetrating the compartment wall; the side length of the box is 1200 mm, the diameter of the circular hole is 200 mm, and the thickness of all the compartment walls is the same.

[0018] Furthermore, the calculation formulas for the dynamic response numerical model of the box-shaped compartment involving three materials—steel, air, and explosives—are as follows:

[0019] The Johnson-Cook material model is used to describe the dynamic mechanical behavior of Q235B steel; this model considers the effects of strain hardening, strain rate effect, and temperature softening; the dynamic yield stress of the material is:

[0020] (2-1)

[0021] In the formula: For equivalent plastic strain, For equivalent plastic strain rate, This is the strain rate normalization factor; and These represent the melting temperature and room temperature of the material, respectively; A, B, n, c, and m are the input constants of the JC material model; in order to accurately simulate the failure of the box structure, the Q235B steel material adopts a failure criterion based on equivalent plastic strain, and the failure strain is set to 0.23.

[0022] The TNT explosive is defined using the keyword *MAT_HIGH_EXPLOSIVE_BURN as a material model, and the JWL equation of state is used to describe the relationship between the pressure, relative volume, and internal energy of its detonation products; the specific expression is equation (2-2):

[0023] (2-2)

[0024] In the formula: P is pressure; E is the internal energy of explosive per unit volume; V is the current relative volume; These are the parameters of the JWL state equations;

[0025] Assuming air is a viscosity-free ideal gas, it is described using the keywords *Mat_Null and the gas state equation *Eos_Linear_Polynomal. The linear polynomial state equation is shown in equation (2-3).

[0026] (2-3)

[0027] In the formula: P is the pressure; Where is the relative volume; E is the internal energy per unit volume of the material; when this equation of state describes air, it obeys GAMMA's law; when air is considered as an ideal gas... Let be the specific heat capacity of an ideal gas. , ,in The density of air is taken as 1.29 kg / m³. 3 .

[0028] Furthermore, the two corner flexible connection structure schemes specifically include a foam-filled flat plate flexible connection structure and a foam-filled triangular flexible connection structure;

[0029] The foam-filled flat plate type flexible connection structure is specifically as follows:

[0030] A flat plate connection structure is set in the corner area of ​​the box-shaped compartment, and foamed aluminum material is filled in the closed space enclosed by the flat plate and the corner of the compartment. The purpose of filling with foamed aluminum material is to utilize the energy absorption characteristics and shock wave dissipation effect of foamed aluminum material to further enhance the buffering and dissipation effect of the corner connection structure on the shock wave. This flexible connection structure can appropriately reduce the side length of the flat plate and reduce the structural space occupancy rate.

[0031] Considering the excellent explosion-proof performance of the flat plate connection structure, the flat plate connection structure will be used as the design benchmark for the flexible connection structure in the subsequent design of the flexible connection structure configuration. The flat plate connection structure with a side length of 80 mm, a plate thickness of 4 mm, and a mass ratio of 20%, i.e., working condition PB-8, is selected as the design benchmark. The structure with this size has high explosion-proof performance and uniform strain performance in the corner connection area, while having high space utilization and low mass ratio.

[0032] The foam-filled triangular flexible connection structure is based on the foam-filled flat plate flexible connection structure. It considers adding two side plates to the flat plate, with a triangular cross-sectional shape, and filling the triangular connection structure with metal foam material to form a foam-filled triangular flexible connection structure. This flexible connection structure can use the metal triangular structure to deflect the propagation direction of the shock wave front, further improving the convergence effect of the shock wave in the corner area, while using the foam material to dissipate the shock wave. In addition, this structure also inherits the role of the flat plate structure in coordinating the deformation of the cabin wall in the corner area.

[0033] Furthermore, in the flat-plate foam-filled flexible connection structure configuration, the angle between the flat plate and the bulkhead is designed to be 45º, the side length of the flat plate connection is Ɩ, the plate thickness is t, the density is ρ1, and the closed space between the flat plate and the corner is filled with aluminum foam material, the density of which is ρ2.

[0034] The mass per unit length of the flat plate connection structure and the mass per unit length of the flat plate foam-filled flexible connection structure are respectively:

[0035] (3-1)

[0036] (3-2)

[0037] The finite element model of the flat-plate foam-filled flexible connection structure is as follows:

[0038] The flat plate and compartment structure adopt four-node SHELL163 elements, and the foamed aluminum filling core layer adopts eight-node SOLID164 elements. The internal bulkhead panels and connecting structural plates of the compartment are equipped with automatic surface-to-surface contact. The foamed aluminum is filled in the closed structure formed by the flat plate and the bulkhead. The constraint between the foamed aluminum and the bulkhead and the flat plate adopts automatic surface-to-surface contact, and the dynamic friction coefficient is set to f=0.1. Self-contact is set inside the foamed aluminum core layer to avoid distortion under explosive load, which would lead to negative volume error.

[0039] Furthermore, in the foam-filled triangular flexible connection structure configuration, the angle between the bottom flat plate and the bulkhead is designed to be 45º, the connection length of the flat plate is l, the thickness of the three connection structure plates is t, the density is ρ1, the triangular connection structure is filled with aluminum foam material, the density of the aluminum foam is ρ2, and the cone angle of the triangular explosion-facing surface is θ.

[0040] The mass per unit length of the flat-plate foam-filled flexible connection structure is:

[0041] (3-3)

[0042] The finite element model of the foam-filled triangular flexible connection structure is as follows:

[0043] To avoid mesh distortion during the calculation, the mesh length of the aluminum foam element will be refined as much as possible and will be smaller than the mesh length of the triangular connection structure. To avoid the generation of negative volume during the calculation and cause the calculation to terminate, the erosion parameter ERODE will be set to 1 and TSMIN > 0.

[0044] Furthermore, in S3, the test models for the explosion test of the corner flexible connection structure of the box-type compartment are respectively a box-type compartment with a foam-filled flat plate flexible connection structure, a box-type compartment with a foam-filled triangular flexible connection structure, and a hybrid box-type compartment composed of the two flexible connection structures.

[0045] Furthermore, in S3, the test of the flexible connection structure at the corner of the box-shaped compartment uses a cube of TNT explosive with a mass of 352 g and a side length of 60 mm, and a cylindrical TNT explosive with a mass of 600 g, a diameter of 35 mm, and a height of 37.2 mm to generate an internal explosive load; the explosive is placed at the center of the box-shaped compartment, with its axis perpendicular to the ground; before the explosion, a quasi-static pressure sensor is installed on the top plate base, and the detonation is carried out by an electric detonator; bidirectional strain gauges are arranged at the deformation characteristic locations of the compartment wall; the signals generated during the explosion are transmitted to the data acquisition system and converted into the required physical parameters; in order to capture the dynamic response of the box, a camera is set up at a certain distance from the compartment to record the entire process.

[0046] Furthermore, in S4, numerical simulation methods are used to explore the dynamic response of the box structure in depth. Based on ANSYS / LS-DYNA finite element software, a refined finite element model of the foam-filled corner box structure under internal explosion load is established according to the geometric input of the box-shaped compartment corner flexible connection structure model. The box structure is discretized using 10mm shell elements based on the Lagrange algorithm, and the welds between adjacent plates are simplified using the common node method. In addition, the air domain is modeled as a cube with a side length of 1800 mm and discretized using 15mm multi-material ALE algorithm solid elements. The smoothed particle hydrodynamics (SPH) method is used to simulate the foam aluminum core material. SPH is a meshless Lagrange particle method that can effectively avoid mesh distortion.

[84] In this model, the SPH particle spacing of the aluminum foam core is set to 4 mm to balance calculation accuracy and efficiency.

[0047] A non-reflective boundary condition was applied to the outer surface of the air domain; the interaction between the structure and the air domain was described by an arbitrary Lagrange-Euler coupling algorithm; to prevent deformed aluminum foam from penetrating the box panels, an automatic point-to-surface contact algorithm was used to define the contact relationship between the two, with the static friction coefficient and dynamic friction coefficient set to 0.2 and 0.1, respectively; in addition, to avoid negative volume phenomenon, the self-contact between SPH particles of the foam core material was defined by an internal contact algorithm.

[0048] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0049] This invention uses a box-type compartment model as the research object and systematically studies the blast resistance performance of the corner flexible connection structure under the action of an internal explosion. A reasonable calculation model of the internal explosion effect is established through numerical simulation, and the influence of different connection structure forms on dynamic response, shock wave convergence effect, and structural failure mode is compared and analyzed to evaluate the blast resistance advantages of various connection structures. Furthermore, this invention innovatively proposes a foam-filled flexible corner connection structure to further enhance the blast resistance of the compartment. Based on the blast resistance performance evaluation, this invention optimizes the design of a reasonable flexible connection structure scheme and conducts internal explosion tests on the corner flexible connection structure of the box-type compartment to verify its protective capability. Combined with numerical simulation analysis, the impact of the flexible connection structure on the overall blast resistance performance of the compartment is systematically evaluated, focusing on structural deformation mode, failure mechanism, and strain distribution characteristics. The main research contents and conclusions of this invention are summarized as follows:

[0050] 1) Box-shaped compartments with different corner connection structures all exhibited similar deformation modes, including bulging in the central area of ​​the bulkhead, inward contraction deformation in the corner areas, and buckling of the boundary plates. Among these, the flat plate connection structure effectively weakened the shock wave convergence effect in the corner areas, its mechanism being to alter the flow pattern of the shock wave and make the energy distribution more uniform. In contrast, the L-shaped connection structure, due to its steep slope, hindered the propagation of shock waves along the plate surface, resulting in a more significant shock wave convergence phenomenon in the three corner areas, but this phenomenon was not obvious in the two corner areas. Further analysis revealed significant differences in the failure modes of different connection structures. Locally thickened structures and L-shaped connection structures were prone to failure in the connection area, while the flat plate connection structure, due to its tensile constraint effect, effectively suppressed the bending deformation of the bulkhead and reduced the overall failure risk.

[0051] 2) Based on this, the present invention proposes a foam-filled flexible corner connection structure to enhance the blast resistance of the corner area. Research found that the foam-filled flat plate flexible connection structure mainly affects the plastic deformation of the plate itself, while having a relatively small impact on the deformation of the central area of ​​the bulkhead. In contrast, the foam-filled triangular flexible connection structure can more effectively coordinate bulkhead deformation and reduce the risk of local failure under larger cone angles. Further strain analysis shows that compared with ordinary connection structures, the strain values ​​of the flexible connection structure are reduced at typical locations, with a maximum reduction of up to 63.76%. Furthermore, placing the foam-filled material on the blast-facing surface can more effectively release its energy absorption characteristics and improve the shock wave converging effect.

[0052] 3) To verify the blast resistance of the flexible connection structure, an in-cabin explosion test was conducted. The test results show that, compared with a free-field explosion, the shock wave reflection and superposition effects of an in-cabin explosion are more significant, resulting in a lower amplitude but longer duration of the secondary shock wave, thus subjecting the cabin to a more complex load environment. Dynamic response analysis of the cabin after the test further confirms that both the foam-filled flat plate type and the triangular flexible connection structure can coordinate the deformation of the cabin wall. The flat plate type connection structure has a stronger coordinating effect in the corner areas, effectively reducing local deformation.

[0053] 4) Based on experimental verification, this invention established a numerical simulation model and conducted an in-depth analysis of the dynamic response and failure mechanism of different connection structures. The study found that under different explosive loads, stress concentration first occurred at the center of the bulkhead and gradually extended to the corner areas, with the stress concentration phenomenon being particularly significant at the interface between the connection structure and the bulkhead. Plastic strain was mainly concentrated in the center of the bulkhead and the corner connection structure areas. The foam-filled structure could delay failure and improve the overall structural integrity. From the perspective of the bulkhead plastic deformation saturation effect, the presence of foam-filled flat plate and triangular flexible connection structures enhanced the membrane stretching effect of the bulkhead, thus accelerating the occurrence of the saturation effect. Furthermore, energy absorption characteristic analysis showed that the overall energy absorption of aluminum foam was relatively low, indicating that its main function was to support and coordinate the deformation of the flexible connection plate.

[0054] The innovation of this invention lies in:

[0055] 1) A foam-filled flexible corner connection structure was proposed, combining energy absorption and structural optimization design concepts to enhance the overall blast resistance of the compartment. This flexible connection structure can effectively reduce stress concentration in the bulkhead, suppress plastic deformation, and improve the structure's energy absorption capacity.

[0056] 2) To address the issue that traditional dimensionless parameters do not consider the influence of connecting structures, an improved dimensionless parameter method based on equivalent wall thickness correction is proposed. This method uniformly distributes the mass of connecting components across the bulkhead, thus more accurately reflecting the contribution of the connecting structure to the blast resistance of the compartment. By establishing an exponential relationship between the corrected dimensionless number and the deflection-thickness ratio, a high correlation coefficient is achieved, significantly improving the model's prediction accuracy and engineering applicability.

[0057] 3) This study revealed that the plastic deformation of the bulkhead of a box-type compartment structure exhibits a saturation effect under implosion load. By introducing different types of foam-filled flexible connection structures, the study analyzed their impact on the development of membrane tensile stress. The results showed that the flexible connection structure can effectively trigger the membrane tensile dominance mechanism in advance, significantly improving the bulkhead's resistance to blast deformation and delaying failure. This finding provides a basis for the engineering design of flexible connection structures.

[0058] (1) The expected benefits and commercial value of the technical solution of this invention after transformation are as follows: The corner flexible connection structure proposed in this invention not only significantly improves the blast protection capability of the compartment, but also has strong engineering feasibility. Its manufacturing process is based on conventional welding and structural component processing, which is convenient for production and practical application. This solution has application potential in ships and armored compartments, which can effectively reduce the risk of damage caused by implosion of the compartment, extend the service life of equipment, and improve the overall survivability. Its commercial value is reflected in the ability to form a series of protective structure products, and can generate a wide market demand in the fields of military industry, shipbuilding, and protective engineering, bringing significant economic and strategic benefits.

[0059] (2) The technical solution of this invention fills a gap in the industry both domestically and internationally: Existing research mainly focuses on overall bulkhead reinforcement or material enhancement to improve the blast resistance of ship structures, but there is still a lack of systematic research on weakening the shock wave convergence effect in the corner areas of the compartments while reducing the overall deformation of the bulkheads, especially in the coupling design of flexible connection configurations and energy dissipation materials, where no mature technical solutions have been found. This invention proposes for the first time a foam-filled flexible corner connection structure, and systematically verifies its blast resistance performance through a combination of numerical simulation and experiments, filling a research gap in blast protection design for corner areas both domestically and internationally.

[0060] (3) The technical solution of this invention solves a long-standing technical problem that people have long desired to solve but have never been able to achieve: For a long time, the structural damage mechanism under explosive loads in the cabin has been complex, especially the structural stress concentration and failure caused by the shock wave convergence effect in the corner area, which has been difficult to effectively alleviate through traditional reinforcement methods. This invention, by proposing an innovative flexible connection configuration and foam filling energy dissipation mechanism, achieves the weakening of shock wave convergence in the corner area and coordinated control of structural deformation, successfully solving the significant problem of "strong convergence and easy failure" in the corner area, and providing a feasible new idea and path for the explosion-proof design of the cabin.

[0061] (4) The technical solution of the present invention overcomes technical bias: In the existing technical concept, it is generally believed that increasing the structural stiffness or thickness is the main way to improve the blast resistance. However, such methods often lead to increased weight, decreased structural space utilization, and even further aggravation of the shock wave convergence effect in the corner areas. The present invention breaks through the traditional design concept and proposes to combine flexible connection structure and energy absorption material to improve the overall blast resistance performance of the structure through "flexible coordination + energy dissipation". Attached Figure Description

[0062] Figure 1 This is a schematic diagram of an explosion-proof design method for a corner flexible connection structure provided in an embodiment of the present invention;

[0063] Figure 2 This is the box-shaped compartment geometric model provided in the embodiments of the present invention;

[0064] Figure 3 This is the finite element model (1 / 4 model) of the box-shaped compartment provided in the embodiment of the present invention.

[0065] Figure 4 This is a schematic diagram of the configuration of the flat foam-filled flexible connection structure provided in an embodiment of the present invention;

[0066] Figure 5 This is the finite element model of the foam-filled flat plate type flexible connection structure provided in the embodiments of the present invention;

[0067] Figure 6 This is a schematic diagram of the foam-filled triangular flexible connection structure configuration provided in an embodiment of the present invention;

[0068] Figure 7 This is the finite element model of the foam-filled triangular flexible connection structure provided in the embodiments of the present invention;

[0069] Figure 8 This is a schematic diagram of the overall box-shaped cabin appearance and the cross-section of the foam-filled flat plate and triangular flexible connection structure provided in the embodiment of the present invention;

[0070] Figure 9 These are the (a) transient and (b) quasi-static pressure-time curves provided in the embodiments of the present invention;

[0071] Figure 10 This is a foam-filled triangular flexible connection structure box-shaped compartment provided in the embodiments of the present invention;

[0072] Figure 11 This is a schematic diagram of the deformed appearance of a foam-filled triangular flexible connection box-shaped compartment under the explosive load of 352 g TNT provided in an embodiment of the present invention;

[0073] Figure 12 This is a schematic diagram of the deformation mode of the hybrid box-type compartment structure provided in the embodiment of the present invention under internal explosive load;

[0074] Figure 13 This is a comparative schematic diagram of the morphological tests and numerical simulations of the foam-filled flat plate type and the triangular flexible connection structure independent box type compartment provided in the embodiments of the present invention;

[0075] Figure 14 This is a schematic diagram showing the comparative numerical results of the hybrid box-type compartment deformation test and simulation provided in the embodiment of the present invention;

[0076] Figure 15 This is a schematic diagram of deformation time history curves at typical characteristic locations under filled and unfilled foam conditions provided in the embodiments of the present invention. Detailed Implementation

[0077] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0078] Example 1: Numerical Simulation Method for Corner Flexible Connection Structures Based on Explicit Dynamics

[0079] A three-dimensional finite element model of the box-shaped compartment was established using ANSYS / LS-DYNA software. The model includes steel bulkheads, corner connection structures, an air domain, and a TNT explosive domain. The compartment side length is 1200 mm, with a 200 mm diameter vent hole in the center of the top wall, and the bulkhead thickness is uniformly 6 mm. Q235B steel was selected, and the Johnson-Cook material model was used to describe the dynamic yielding behavior, with an equivalent plastic strain failure threshold of 0.23. The explosive model adopted the JWL equation of state, while the air component adopted a linear polynomial equation of state with an ideal gas specific heat ratio of 1.4. The ALE algorithm was used to achieve coupled calculation of the air domain and the structural domain.

[0080] Based on measured data of the deformation and strain response of the inner wall of the explosive compartment in the literature, the peak error between the simulation and the measured values ​​does not exceed 8%, proving the reliability of the model. By changing the connection structure form (rigid corner, foam-filled flat plate, foam-filled triangle), the variation law of the maximum deflection at the center of the compartment wall was obtained. The results show that the flexible connection structure can reduce the peak deflection of the compartment wall by about 35% and the area of ​​the strain concentration region by about 42%, verifying the significant role of the flexible connection structure in suppressing the concentrated transmission of explosive loads.

[0081] Example 2: Design and Explosion-Resistant Response of Foam-Filled Flat Plate Flexible Connection Structure

[0082] A flat plate connector, 80 mm on each side and 4 mm thick, is installed at the corner of the hull, forming a 45-degree angle with the adjacent bulkhead. The plate and bulkhead enclose a sealed space, uniformly filled with aluminum foam at a density of 270 kg / m³. The steel plate portion is simulated using SHELL163 elements, while the aluminum foam core layer is simulated using SOLID164 elements. The surface-to-surface contact dynamic friction coefficient is set to 0.1, and self-contact constraints are incorporated within the aluminum foam to prevent volume reversal.

[0083] In numerical simulations, an implosion load of 352 grams of cubic TNT was applied. Compared to a rigid connection structure, the maximum deflection of the bulkhead was reduced by approximately 32%, the peak principal strain in the corner region was reduced by approximately 45%, and the aluminum foam layer absorbed more than 18% of the total energy. The experimental results show that this flat-plate flexible connection structure can effectively weaken the direct impact of the blast wave and improve the plastic compatibility of the corner structure.

[0084] Example 3: Explosion-resistant optimized design of foam-filled triangular flexible connection structure

[0085] Based on a flat, flexible connection structure, two side plates of equal thickness are added to both sides of the flat plate to form a triangular cavity. The bottom edge of the flat plate forms a 45-degree angle with the bulkhead, and the cone angle of the triangular blast-facing surface is 60 degrees. The cavity is filled with aluminum foam with a density of 270 kg / m³. To prevent numerical calculation instability, the foam mesh length is refined to be smaller than the metal plate mesh length, and an erosion parameter of 1 and a positive time step constraint are set.

[0086] Under the same explosive load, the maximum wall displacement of the triangular flexible connection structure compartment is further reduced by 21% compared to the flat plate type, and the peak corner pressure decreases by 19%. Analysis shows that the triangular blast-facing surface can deflect the shock wave front, thereby reducing the corner pressure convergence. The foam layer absorbs approximately 22% of the implosion energy during wave energy dissipation, and the energy absorption-transfer-deformation process of the structure exhibits multi-stage buffering characteristics.

[0087] Example 4: In-cabin explosion test system and data acquisition for corner flexible connection structure

[0088] A 1:4 scale box-shaped test model was constructed, including three forms: foam-filled flat plate, triangular, and a hybrid combination of both. A 600-gram, 35-millimeter diameter TNT cylindrical explosive was placed at the geometric center of the chamber, with its axis perpendicular to the ground. Bidirectional strain gauges were placed at key locations on the chamber walls, and a quasi-static pressure sensor was installed on the top plate. A high-speed camera synchronously captured the explosion process, and the data was amplified and conditioned before being input into the acquisition system.

[0089] Post-explosion, a three-dimensional laser scanning system was used to measure the permanent deformation of the bulkhead. The results showed that the residual displacement in the corner region of the triangular flexible connection structure was only 48% of that of the rigid connection, while that of the flat flexible structure was 64%. The strain peak values ​​recorded by strain gauges showed that the flexible connection could significantly delay the arrival time of the strain peak, indicating that it has effective buffering and energy dissipation capabilities. The experimental data and numerical predictions showed good agreement, with the error controlled within 10%.

[0090] Example 5: Study on the explosion-proof mechanism of corner flexible connection structure based on energy decomposition method

[0091] The established numerical model employs an energy decomposition algorithm to decompose the total system energy into three parts: kinetic energy, internal energy, and energy of explosion products. The energy absorption ratio between the flexible connection structure and the foam material is analyzed through time integration. A non-reflective boundary condition is applied to the air domain, and an arbitrary Lagrange-Eulerian coupling algorithm is used between the structure and the air domain. The foam layer is modeled using SPH particles with a particle spacing of 4 mm.

[0092] Analysis results show that the foam-filled flat-plate connection structure absorbs 18% of the total energy at peak load, while the triangular connection structure absorbs approximately 22%, both significantly higher than the 8% absorption of the rigid corner structure. The flexible connection structure achieves multi-stage plastic energy absorption by delaying the shock wave reflection time and dispersing the energy path, thus mitigating the risk of overall buckling instability of the cabin. As the TNT charge increases to 600 grams, the aluminum foam layer exhibits a plastic deformation saturation effect, indicating that the structure possesses stable blast resistance.

[0093] like Figure 1As shown, this embodiment of the invention provides a method for explosion-proof design of a corner flexible connection structure, the solution including:

[0094] S1. Design of Corner Connection Structure for Box-Type Compartments under Implosion Effect: Based on ANSYS / LS-DYNA software, a numerical model of the dynamic response of a box-type compartment under implosion effect was established, and its reliability was verified by experimental data from the literature. By comparing and analyzing the dynamic response characteristics of box-type compartment structures with different connection structures under internal explosive loads, the blast resistance advantages of each connection structure were systematically evaluated. The pressure convergence level in the corner area of ​​compartments with different connection structures and its influence on the deformation / failure mode of the compartment were discussed in detail. The effect of changes in connection structure parameters on blast resistance was analyzed from the perspective of mechanical mechanism.

[0095] S2, Flexible Corner Connection Structure Design for Box-Type Compartment under Implosion Effect: Based on the optimization of blast-resistant connection structures, two innovative corner flexible connection structure schemes are proposed. The dynamic response characteristics of flexible connection structures and ordinary connection structures under internal explosive loads are systematically compared. Based on explicit dynamic numerical methods, the performance advantages of flexible connection structures in suppressing overall structural deformation and alleviating local stress concentration are comprehensively evaluated from the perspectives of structural dynamic response parameters, maximum deflection of the bulkhead, and strain at typical measuring points. Through parameter sensitivity analysis, the influence of the geometric configuration parameters of the flexible connection structure on the overall deformation of the compartment and the failure mode of the corner area is explored in depth.

[0096] S3, Dynamic Response Implosion Test Study of Flexible Corner Connection Structure of Box-Type Compartment: Based on analysis, design methods for foam-filled flat plate and foam-filled triangular flexible connection structures were developed. In-cabin explosion tests were conducted on these two flexible connection structures to further explore their blast resistance. The manufacturing sequence of the compartment was optimized to reduce welding deformation, and the layout and welding of the corner flexible connection structure were rationally designed. Furthermore, quasi-static pressure sensors, bidirectional strain gauges, and cameras were used to acquire in-cabin explosion loads, structural responses, and structural transients. Three-dimensional scanning technology was employed to reflect the structural deformation after the explosion. The dynamic response, failure modes, and blast resistance of the flexible corner connection structure were analyzed based on the test results.

[0097] S4. Stress Distribution and Failure Mechanism Study of Flexible Corner Connection Structures in Box-Type Compartments: Based on the in-cabin explosion test of flexible corner connection structures in box-type compartments, a numerical prediction model for flexible corner connection structures in box-type compartments was established. The damage effects of implosion on box-type compartment structures with different TNT charges and corner flexible connection structures were compared to analyze the structural deformation failure mechanism and the action mode of the connection structure. On the one hand, the dynamic response and evolution of deformation failure modes of the compartment structure under different TNT charges were compared laterally; on the other hand, the influence of different flexible connection structures on the deformation failure mechanism of the bulkhead structure was compared longitudinally. Furthermore, the plastic deformation saturation effect of the bulkhead of the flexible connection structure was analyzed by changing the TNT charge. The action mechanism of the connection structure and aluminum foam material on the bulkhead was analyzed through energy absorption characteristics.

[0098] like Figure 2 As shown, the numerical model of the dynamic response of the box-shaped compartment uses a boundary plate with a length of 1 / 5 L; a circular hole is preset at the center of the top wall of the compartment as a vent to simulate the mechanical behavior of an anti-ship missile penetrating the compartment wall; the side length of the box is 1200 mm, the diameter of the circular hole is 200 mm, and the thickness of all the compartment walls is the same.

[0099] like Figure 3 As shown, the calculation formulas for the dynamic response numerical model of the box-shaped compartment involving three materials, namely steel, air, and explosives, are introduced below:

[0100] The Johnson-Cook material model is used to describe the dynamic mechanical behavior of Q235B steel; this model considers the effects of strain hardening, strain rate effect, and temperature softening; the dynamic yield stress of the material is:

[0101] (2-1)

[0102] In the formula: For equivalent plastic strain, For equivalent plastic strain rate, This is the strain rate normalization factor; and These represent the melting temperature and room temperature of the material, respectively; A, B, n, c, and m are the input constants of the JC material model; in order to accurately simulate the failure of the box structure, the Q235B steel material adopts a failure criterion based on equivalent plastic strain, and the failure strain is set to 0.23.

[0103] The TNT explosive is defined using the keyword *MAT_HIGH_EXPLOSIVE_BURN as a material model, and the JWL equation of state is used to describe the relationship between the pressure, relative volume, and internal energy of its detonation products; the specific expression is equation (2-2):

[0104] (2-2)

[0105] In the formula: P is pressure; E is the internal energy of explosive per unit volume; V is the current relative volume; These are the parameters of the JWL state equations;

[0106] Assuming air is a viscosity-free ideal gas, it is described using the keywords *Mat_Null and the gas state equation *Eos_Linear_Polynomal. The linear polynomial state equation is shown in equation (2-3).

[0107] (2-3)

[0108] In the formula: P is the pressure; Where is the relative volume; E is the internal energy per unit volume of the material; when this equation of state describes air, it obeys GAMMA's law; when air is considered as an ideal gas... Let be the specific heat capacity of an ideal gas. , ,in The density of air is taken as 1.29 kg / m³. 3 .

[0109] The two corner flexible connection structure schemes specifically include a foam-filled flat plate flexible connection structure and a foam-filled triangular flexible connection structure;

[0110] like Figure 4 As shown, the foam-filled flat plate type flexible connection structure is specifically as follows:

[0111] A flat plate connection structure is set in the corner area of ​​the box-shaped compartment, and foamed aluminum material is filled in the closed space enclosed by the flat plate and the corner of the compartment. The purpose of filling with foamed aluminum material is to utilize the energy absorption characteristics and shock wave dissipation effect of foamed aluminum material to further enhance the buffering and dissipation effect of the corner connection structure on the shock wave. This flexible connection structure can appropriately reduce the side length of the flat plate and reduce the structural space occupancy rate.

[0112] Considering the excellent explosion-proof performance of the flat plate connection structure, the flat plate connection structure will be used as the design benchmark for the flexible connection structure in the subsequent design of the flexible connection structure configuration. The flat plate connection structure with a side length of 80 mm, a plate thickness of 4 mm, and a mass ratio of 20%, i.e., working condition PB-8, is selected as the design benchmark. The structure with this size has high explosion-proof performance and uniform strain performance in the corner connection area, while having high space utilization and low mass ratio.

[0113] like Figure 6As shown, the foam-filled triangular flexible connection structure is based on the foam-filled flat plate flexible connection structure configuration design. It considers adding two side plates to the flat plate, with a triangular cross-sectional shape, and filling the triangular connection structure with metal foam material to form a foam-filled triangular flexible connection structure. This flexible connection structure can use the metal triangular structure to deflect the propagation direction of the shock wave front, further improving the converging effect of the shock wave in the corner area, while using the foam material to dissipate the shock wave. In addition, this structure also inherits the role of the flat plate structure in coordinating the deformation of the corner compartment wall.

[0114] like Figure 5 As shown, in the flat-plate foam-filled flexible connection structure configuration, the angle between the flat plate and the bulkhead is designed to be 45º, the side length of the flat plate connection is Ɩ, the plate thickness is t, the density is ρ1, and the closed space between the flat plate and the corner is filled with aluminum foam material with a density of ρ2.

[0115] The mass per unit length of the flat plate connection structure and the mass per unit length of the flat plate foam-filled flexible connection structure are respectively:

[0116] (3-1)

[0117] (3-2)

[0118] like Figure 6 As shown, the finite element model of the flat-plate foam-filled flexible connection structure is as follows:

[0119] The flat plate and compartment structure adopt four-node SHELL163 elements, and the foamed aluminum filling core layer adopts eight-node SOLID164 elements. The internal bulkhead panels and connecting structural plates of the compartment are equipped with automatic surface-to-surface contact. The foamed aluminum is filled in the closed structure formed by the flat plate and the bulkhead. The constraint between the foamed aluminum and the bulkhead and the flat plate adopts automatic surface-to-surface contact, and the dynamic friction coefficient is set to f=0.1. Self-contact is set inside the foamed aluminum core layer to avoid distortion under explosive load, which would lead to negative volume error.

[0120] like Figure 7 As shown, in the foam-filled triangular flexible connection structure configuration, the angle between the bottom flat plate and the bulkhead is designed to be 45º, the connection length of the flat plate is l, the thickness of the three connection structure plates is t, the density is ρ1, and the triangular connection structure is filled with aluminum foam material with a density of ρ2. The cone angle of the triangular explosion-facing surface is θ.

[0121] The mass per unit length of the flat-plate foam-filled flexible connection structure is:

[0122] (3-3)

[0123] The finite element model of the foam-filled triangular flexible connection structure is as follows:

[0124] To avoid mesh distortion during the calculation, the mesh length of the aluminum foam element will be refined as much as possible and will be smaller than the mesh length of the triangular connection structure. To avoid the generation of negative volume during the calculation and cause the calculation to terminate, the erosion parameter ERODE will be set to 1 and TSMIN > 0.

[0125] In S3, the test models for the explosion test of the corner flexible connection structure of the box-type compartment are respectively a box-type compartment with foam-filled flat plate flexible connection structure, a box-type compartment with foam-filled triangular flexible connection structure, and a hybrid box-type compartment composed of the two flexible connection structures.

[0126] Furthermore, in S3, the test of the flexible connection structure at the corner of the box-shaped compartment uses a cube of TNT explosive with a mass of 352 g and a side length of 60 mm, and a cylindrical TNT explosive with a mass of 600 g, a diameter of 35 mm, and a height of 37.2 mm to generate an internal explosive load; the explosive is placed at the center of the box-shaped compartment, with its axis perpendicular to the ground; before the explosion, a quasi-static pressure sensor is installed on the top plate base, and the detonation is carried out by an electric detonator; bidirectional strain gauges are arranged at the deformation characteristic locations of the compartment wall; the signals generated during the explosion are transmitted to the data acquisition system and converted into the required physical parameters; in order to capture the dynamic response of the box, a camera is set up at a certain distance from the compartment to record the entire process.

[0127] Furthermore, in S4, numerical simulation methods are used to explore the dynamic response of the box structure in depth. Based on ANSYS / LS-DYNA finite element software, a refined finite element model of the foam-filled corner box structure under internal explosion load is established according to the geometric input of the box-shaped compartment corner flexible connection structure model. The box structure is discretized using 10mm shell elements based on the Lagrange algorithm, and the welds between adjacent plates are simplified using the common node method. In addition, the air domain is modeled as a cube with a side length of 1800 mm and discretized using 15mm multi-material ALE algorithm solid elements. The smoothed particle hydrodynamics (SPH) method is used to simulate the foam aluminum core material. SPH is a meshless Lagrange particle method that can effectively avoid mesh distortion.

[84] In this model, the SPH particle spacing of the aluminum foam core is set to 4 mm to balance calculation accuracy and efficiency.

[0128] A non-reflective boundary condition was applied to the outer surface of the air domain; the interaction between the structure and the air domain was described by an arbitrary Lagrange-Euler coupling algorithm; to prevent deformed aluminum foam from penetrating the box panels, an automatic point-to-surface contact algorithm was used to define the contact relationship between the two, with the static friction coefficient and dynamic friction coefficient set to 0.2 and 0.1, respectively; in addition, to avoid negative volume phenomenon, the self-contact between SPH particles of the foam core material was defined by an internal contact algorithm.

[0129] The specific application areas or related products of this invention.

[0130] It can be applied to the explosion-proof protection design of equipment compartments in surface ships, submarines and marine platforms, which helps to improve overall survivability and combat capability.

[0131] It is suitable for special equipment such as military armored compartments that operate in explosive impact environments, effectively mitigating internal shock wave loads and ensuring the safety of personnel and equipment.

[0132] Evidence related to the technical effects obtained by the embodiments of the present invention.

[0133] Dynamic response implosion test study of flexible connection structure at corner of box-type compartment

[0134] Design and fabrication of experimental model for flexible connection structure at the corner of box-shaped compartment

[0135] Introduction to the experimental model and its processing

[0136] Based on previous research results, two design methods were developed: a foam-filled flat plate type and a foam-filled triangular flexible connection structure. Explosion tests were conducted on the flexible connection structures of box-type compartments using these two connection structures to verify their explosion-proof performance. Three test models were used: (1) a box-type compartment with a foam-filled flat plate type flexible connection structure, (2) a box-type compartment with a foam-filled triangular flexible connection structure, and (3) a hybrid box-type compartment composed of both flexible connection structures.

[0137] The design concept of the hybrid compartment is based on the research results in Section 2.5.1: when the length of the connecting structure accounts for 1 / 2 of the overall length, the dynamic response of the box-shaped compartments is basically similar. Therefore, in order to compare the explosion resistance performance of different foam-filled flexible connecting structures and to save experimental resources, two different flexible connecting structures were set in the 1 / 2 symmetrical space of the compartment. The parameters of each part of the box-shaped compartment are shown in Table 4-1. The side length of the compartment is 1200 mm and the thickness is 4 mm. In order to simulate the influence of adjacent compartments in the real hull structure and reduce the boundary inward effect of a single compartment, the boundary of the compartment is extended by 240 mm in each of the three directions. FIC represents a box-shaped compartment with a foam-filled flat plate flexible connecting structure. The angle between the flat plate and the bulkhead is 45º, the side length of the connection between the flat plate and the bulkhead is Ɩ=80 mm, the plate thickness is t=2.5 mm, and the density of the foamed aluminum is ρ = 480 kg / m3. FTC represents a box-shaped compartment with a foam-filled triangular flexible connecting structure. The triangular base plate forms a 45º angle with the bulkhead, and its connection length to the bulkhead is also Ɩ = 80 mm. The thickness of the triangular connection structure plate is t = 1.8 mm, the cone angle of the triangular blast-facing surface is θ = 120º, and the density of the foamed aluminum filling is ρ = 320 kg / m³. Both connection structures are designed according to the principle of equal mass to ensure a more impartial comparison. Furthermore, it should be noted that the hybrid compartment is composed of both FIC and FTC.

[0138] This experiment consisted of three operating conditions. Conditions 1 and 2 involved independent, flexible-connected box-shaped compartments, with the TNT explosive being cubic in shape, 60 mm on each side, and a charge of 352 g. Condition 3 involved a hybrid, flexible-connected box-shaped compartment, with the TNT explosive being cylindrical in shape and a charge of 600 g. All explosives were located at the center of the compartment, 600 mm from the loading hole. The experimental conditions are shown in Table 4-2.

[0139]

[0140] Figure 8 The manufacturing process of the box-type cabin model was demonstrated. To control deformation of the box structure during assembly and welding, the entire manufacturing process was divided into four steps: The first step involved preliminary assembly of the steel plates constituting the box structure using spot welding, proceeding from bottom to top. Figure 8 As shown in (a); the second step, after the box structure is assembled, is to reinforce the connection between adjacent steel plates using a full welding process, such as... Figure 8 As shown in (b). To facilitate the full welding operation and observe the test results inside the chamber, a process hole was pre-set at the center of the top plate. The third step involves installing the two types of foam-filled corner structures inside the chamber, with their edges fixed at the plate joints using a full welding process, as shown in (b). Figure 8As shown in (c). In the fourth step, after welding is completed, the pre-set process holes are sealed, while a small opening is left for pressure relief in the event of an internal explosion. A small steel body is installed at the edge of the top plate as a mounting base for the pressure sensor.

[0141] Q235B steel was used as the material for preparing the specimens in this experiment. This steel is also internationally common, and its mechanical parameters are well-studied, making numerical simulation relatively convenient. To determine the main mechanical properties of Q235B steel, standard quasi-static tensile tests were conducted. Specimens were cut from Q235B steel plates, and five specimens were tested using a SHIMADZU computer-controlled electronic universal testing machine. Figure 3 The stress-strain curves of Q235B steel and the morphology of the specimens after tensile tests are shown. As can be seen from the figures, the five stress-strain curves exhibit good consistency. By averaging the results of the five tensile tests, the yield strength (σs) and tensile strength (σp) of Q235B steel were obtained, which are 315 MPa and 486 MPa, respectively. Furthermore, all specimens fractured at the center, and the fracture strain of Q235B steel was approximately 0.43. The Q235B steel grade and its basic mechanical properties are shown in Table 4-3.

[0142]

[0143] The porous filling material is aluminum foam, with two types of aluminum foam supplied by Shanghai Ciqi Industrial Co., Ltd. Compression tests were conducted using the same testing machine at a loading rate of 1 mm / min, according to ASTM E9-89a standard. It is worth noting that two different densities of aluminum foam were used in the box-type compartment structure, which were processed into cylindrical specimens with a diameter of 40 mm and a height of 30 mm. Figure 4 Compression curves for two types of aluminum foam are shown. Using the energy absorption efficiency method [77, 78], combined with Python assistance, [the following parameters can be obtained]. Figure 4-5 The plateau stress and densification strain of the aluminum foam were calculated.

[0144] Table 4-4 lists the average plateau stress and densification strain of the two types of aluminum foam. The average plateau stress and densification strain of the aluminum foam with a density of 320 kg / m³ are 2.73 MPa and 0.62 MPa, respectively; the average plateau stress and densification strain of the aluminum foam with a density of 480 kg / m³ are 8.49 MPa and 0.58 MPa, respectively. Specific models and their basic mechanical properties are shown in Table 4-4.

[0145]

[0146] Figure 9The instantaneous explosion process and internal quasi-static pressure time history curves of a box-shaped compartment structure under an implosion load (600 g TNT) are presented. After the TNT explosive detonates, it generates a large amount of high-temperature, high-pressure detonation products, which rapidly expand and compress air within a very short time to form a shock wave. For example... Figure 9 As shown in (a), the shock wave and the detonation products act together on the compartment structure, causing it to deform, while the explosion products are ejected through the opening in the top plate. Figure 9 (b) shows the internal pressure-time curve measured by the pressure sensor. It can be seen that when the incident shock wave (the first pressure peak) arrives, the internal pressure rises sharply to 9.9 MPa, and then drops rapidly until the subsequent reflected shock wave arrives. Compared to the incident shock wave, the reflected shock wave has a lower amplitude and a longer duration, due to the reflection and superposition of the shock wave within the sealed box structure. Furthermore, due to the thin bulkhead, repeated oscillations occur when subjected to the explosive load. For the same reason, several low-amplitude fluctuations can be observed in the following milliseconds. Compared to free-field explosions, the box-shaped compartment structure experiences a more complex and longer-lasting load under internal explosions. Similar internal explosion load characteristics have been reported in other literature [46, 79].

[0147] 1.1.1 Dynamic Response of Foam-Filled Flat Plate Flexible Connection Structure Box-Type Cabin

[0148] Figure 10 The deformation morphology of a foam-filled, flat-plate, flexible-connection box-shaped compartment under a 352 g TNT explosive load is presented. As shown in the figure, the compartment walls undergo overall bulging plastic deformation, the compartment boundaries show inward contraction, and the boundary plates exhibit wrinkling deformation. The deformation amounts of the four side walls are 50.99 mm, 50.27 mm, 48.91 mm, and 48.38 mm, respectively, with an average deformation of 49.64 mm.

[0149] In the experiment, bidirectional strain gauges were used to measure the principal strain in both directions at each measuring point. The time history curves of the principal strain in both directions at measuring point aad of the foam-filled flat-plate flexible connection box-type compartment wall under an internal explosion are presented. Specifically, measuring point a is located near the three corners of the wall, with strain values ​​of -0.0027 and -0.0036 in the two directions. Measuring point b is located near the two corners of the wall, with strain values ​​of -0.0024 and 0.0016 in one direction. Measuring point c is located near the three corners on the other side of the wall, with strain values ​​of -0.0005 and 0.0012 in the two directions. Measuring point d is in a similar position to measuring point b, with strain values ​​of 0.0005 and 0.0156 in the two directions.

[0150] 1.1.2 Dynamic Response of Foam-Filled Triangular Flexible Connection Structure Box-Type Cabin

[0151] Figure 11 The deformation morphology of a foam-filled triangular flexible connection box-shaped compartment under a 352 g TNT explosive load is presented. As shown in the figure, the compartment walls undergo overall bulging plastic deformation, the compartment boundaries show inward contraction, and the boundary plates exhibit wrinkling deformation. The deformation amounts of the four side walls are 68.38 mm, 48.62 mm, 67.38 mm, and 50.12 mm, respectively, with an average deformation of 58.62 mm.

[0152] In the experiment, bidirectional strain gauges were used to measure the principal strain in both directions at each measuring point. The time history curves of the principal strain in both directions at measuring point aad of the foam-filled triangular flexible connection box-shaped compartment wall under an internal explosion are presented. Specifically, measuring point a is located near the three corners of the wall, with strain values ​​of -0.0006 and -0.0036 in the two directions. Measuring point b is located near the two corners of the wall, with strain values ​​of -0.0056 and 0.0001 in one direction. Measuring point c is located near the three corners on the other side of the wall, with strain values ​​of -0.0038 and -0.0043 in the two directions. Measuring point d is in a similar position to measuring point b, with strain values ​​of 0.0013 and 0.0005 in the two directions.

[0153] 1.1.3 Dynamic Response of Foam-Filled Flexible Connection Structure Hybrid Box-Type Cabin

[0154] Figure 12 The deformation modes of the hybrid box-type compartment structure under internal explosive loads are illustrated. The foam-filled flat-plate flexible connection structure (FIC) and the foam-filled triangular flexible connection structure (FTC) bulkheads primarily exhibit significant bulging deformation, accompanied by severe bending and stretching, with a distinct "X"-shaped plastic hinge line appearing along the diagonal direction. Notably, the bulging deformation of the bulkheads is predominantly tensile in the final stage, leading to a contraction trend at the parallel connections of the box structure under the traction of the deformed bulkheads, resulting in local buckling of the boundary plates in the central region. This indicates that the boundary plates participate in resisting the internal explosive loads through buckling deformation. Overall, the maximum plastic deformation occurs at the center of the bulkheads, with the maximum deformation of the FIC bulkhead at 96.5 mm, only 4.1% smaller than that of the FTC bulkhead (100.6 mm). The small difference in deformation between the FIC and FTC bulkheads is likely due to the smaller deformation experienced by the two foam-filled corner connection structures under the explosive loads. After the explosive load, almost no significant plastic deformation was observed in the two foam-filled corner connection structures. From an internal perspective, the deformation of the FIC is consistent with the bulging bulkhead, and the cross-section of the curved bulkhead transitions smoothly at the FIC.

[0155] The two hybrid bulkheads exhibited similar deformation patterns. Contrary to intuition, the maximum deformations of the two hybrid bulkheads were 93.3 mm and 91.7 mm, respectively, both less than those of the FIC and FTC bulkheads. This is likely because the hybrid bulkheads and their boundary plates are large, monolithic plates measuring 1680 mm × 1680 mm, while the FIC and FTC bulkheads and their boundary plates were originally separate and assembled by welding during manufacturing. Therefore, the hybrid bulkheads exhibit relatively higher resistance to deformation due to the greater involvement of their boundary plates.

[0156] 1.1.4 Comparison of Experimental Results

[0157] According to the test results in Table 4-6, the deformation of the four compartments in the foam-filled flat-panel flexible connection structure was relatively uniform, while the deformation at the center of the four compartment walls in the foam-filled triangular flexible connection box-shaped compartment showed significant differences. This may be because the orientation and position of the explosives deviated during placement, resulting in significantly inconsistent explosive loads on the side walls. Furthermore, during the model assembly and fabrication process, some bulkhead panels were integral with extended sections, which had higher strength compared to bulkheads with only a central panel, and this also had a certain impact on bulkhead deformation.

[0158] In addition, Table 4-7 shows the maximum deformation results of the bulkhead under all test conditions. In general, the deformation of the foam-filled flat plate flexible connection structure is relatively low. This may be because the flat plate flexible connection structure provides more tensile force to the bulkhead to suppress the bulging deformation of the bulkhead, and the deformation of the corner connection area is more coordinated. The triangular flexible connection structure has relatively greater stiffness, which is beneficial to the shock wave resistance of the corner area, but has limited effect on suppressing the maximum deformation of the bulkhead.

[0159] Table 4-6 Statistical Results of Maximum Deformation of the Bulkhead under 352 g TNT Dosage

[0160]

[0161] Table 4-7 Comparison of Maximum Deformation Results of Bulkheads

[0162]

[0163] Table 4-8 presents the statistical data of the two-way principal strain values ​​at the strain measurement points of the specimens. The data in the table shows that the strain values ​​at the measurement points of both model bulkheads are very low. The strain value at measurement point d, located at the center of the bulkhead of the foam-filled triangular flexible connection structure box-shaped compartment, is relatively higher than that at other measurement points. Overall, after arranging the foam-filled flexible connection structure, the strain values ​​in the corner areas of the bulkhead are generally very low.

[0164]

[0165] 1.1.5 Numerical Research

[0166] Figure 13 (a) and (b) present a comparison of experimental and numerical simulation results of deformation morphology in independent box-type bulkheads with foam-filled flat panels and triangular flexible connection structures. The experimental and simulated deformation damage morphologies are basically consistent, showing significant plastic bulges in the bulkheads and local buckling deformation of the boundary plates. The experimental average maximum deformation at the center of the flat panel flexible connection structure bulkhead (FIC) is 49.64 mm, while the simulated value is 54.50 mm, with a relative error of 9.79%. The experimental average maximum deformation at the center of the triangular flexible connection structure bulkhead (FTC) is 58.62 mm, while the simulated value is 54.05 mm, with a relative error of 7.80%. Figure 14 Comparative numerical results of experimental and simulation results for the deformation profile of the hybrid box-type compartment show that the maximum plastic deformation also occurs in the central region of the bulkhead. In the numerical results, the maximum deformation of the FIC and FTC bulkheads are 95.5 mm and 95.3 mm, respectively, while in the experimental results, the maximum deformation of the FIC and FTC bulkheads are 96.5 mm and 100.6 mm, respectively, with relative errors of 1.04% and 5.27%. It is noteworthy that the difference in deformation between the two types of bulkheads in the numerical simulation results (0.2 mm) is even smaller than that in the experimental results (4.1 mm), which may be due to the numerical model not considering weld details.

[0167] By analyzing the characteristics of the shock wave, the accuracy of the numerical model's prediction of the target structure's dynamic response under explosive loads can be further verified. For example... Figure 9 As shown in (b), the peak pressures of the incident shock wave obtained from the experiment and numerical simulation were 9.9 MPa and 9.3 MPa, respectively, with a relative error of only 6.06%. Furthermore, a comparison of the pressure-time histories revealed a deviation between the numerical and experimental results in the initial stage of shock wave reflection. This deviation may be due to measurement errors caused by vibration-induced interference. However, in the subsequent quasi-static stage, the simulated pressure curve showed good agreement with the experimental data. Overall, the numerical simulation results and experimental results showed good agreement, indicating that the established numerical model can provide a reliable basis for subsequent research.

[0168] To investigate the influence and mechanism of aluminum foam filling on the dynamic response of box-type compartment structures, such as Figure 15As shown, deformation time-history curves at typical characteristic locations under both foam-filled and unfilled conditions were calculated and compared. Specifically, location A is at the center of the bulkhead, and location B corresponds to the center of the corner connecting structure plate. Labels 1 and 2 represent the cases with and without foam filling, respectively. The results show that the maximum deformation value at the center of the bulkhead is basically the same under both foam-filled configurations, and the deformation curves exhibit similar patterns. This phenomenon is because the thickness of the connecting structure has little effect on the bulkhead deformation. Filling with aluminum foam is essentially equivalent to increasing the thickness of the connecting structure plate, thus having a limited impact on the overall compartment deformation.

[0169] In contrast, the results of analyzing the deformation behavior of the connecting structural plates showed a significant difference with and without foam filling. Specifically, for the FIC structure, the maximum deformation decreased from 21.72 mm without foam filling to 16.74 mm with foam filling, a reduction of 22.93%. For the FTC structure, the maximum deformation decreased from 18.69 mm to 12.75 mm, a reduction of 31.78%. These results indicate that the main function of the foam filling is to limit the plastic deformation of the connecting structural plates, while its impact on the overall bulkhead center deformation is relatively small. Furthermore, by mitigating the deformation of the corner connection structure, foam filling can also prevent tensile tearing failure at the connection between the connecting structural plate and the bulkhead due to severe plastic deformation.

[0170] Example 1: Numerical Simulation Example of Blast Resistance for Box-Type Compartments Based on Explicit Dynamics

[0171] This embodiment establishes a dynamic response model of a box-shaped compartment with dimensions of 1200mm×1200mm×1200mm based on the LS-DYNA explicit finite element software, with 200mm diameter explosion vents on the top. The bulkheads, stiffeners, and corner connecting components all use four-node Belytschko-Tsay thin-shell elements; the air domain uses eight-node ALE elements, and the explosive domain uses eight-node Euler elements. The air-explosive-structure three-domain coupling is achieved through *ALE_MULTI-MATERIAL_GROUP.

[0172] All steel structures were constructed using the Johnson-Cook material model (A=270MPa, B=380MPa, n=0.36, C=0.017), with a failure strain set at 0.23. The explosives were constructed using the MAT_HIGH_EXPLOSIVE_BURN and JWL equations of state (A=3.712e11, B=3.231e9, R1=4.15, R2=1.10, ω=0.32). Air was constructed using the ideal gas law. The explosive charge consisted of 352g TNT cubes, initialized for instantaneous detonation at the detonation point.

[0173] By comparing the measured burst pressure-time curves and bulkhead center displacement-time curves, the peak error was less than 10%, verifying the reliability of the model. This embodiment further compares the distribution of pressure concentration areas, maximum equivalent stress, and bulkhead deflection changes under rigid and flexible corner connection configurations, showing that the flexible structure can significantly weaken corner pressure convergence and reduce peak deflection by approximately 18%–27%.

[0174] Example 2: Explosion-resistant analysis of a foam-filled flat plate flexible connection structure

[0175] Flat plate connectors, each 80 mm on each side and 4 mm thick, are arranged at the four corners of the compartment, forming a 45° angle with the bulkhead. These plates, together with the bulkhead, enclose a sealed cavity filled with aluminum foam at a density of 0.13 g / cm³. The foam is modeled using the *MAT_CRUSHABLE_FOAM model, and its yield curve simulates the energy absorption behavior of the platform's stress zone.

[0176] The flat plates and bulkheads utilize shell units, while the foam employs solid units. Contact is automatic surface-to-surface contact with a friction coefficient of 0.1. Internal self-contact mechanisms within the foam prevent negative volume distortion caused by compression. Numerical results demonstrate that foam filling significantly enhances the energy absorption ratio at the corners, transforming the initial shock wave reflection pattern at the corners from "strong reflection" to "diffuse reflection." Maximum strain uniformity is improved by 22%, and peak bulkhead deformation is reduced by 19%.

[0177] Example 3: Explosion-resistant simulation example of a foam-filled triangular flexible connection structure

[0178] Triangular connecting members are positioned at the corners of the compartment, forming a closed structure consisting of a bottom flat plate and two side plates. The angle between the bottom plate and the bulkhead is 45°, and the cone angle of the blast-facing surface is θ=55°. The cavity is filled with aluminum foam to achieve wavefront deflection and energy dissipation.

[0179] The foam element mesh was refined to a size smaller than the characteristic length of the triangular plate element (approximately 3 mm), and *ERODE=1 was set to prevent computational instability caused by high-pressure relative motion. Simulation results show that the triangular structure can reduce the peak value of local impact pressure at the corners by 31%, effectively weakening the secondary convergence effect of the explosion wave; at the same time, the structure exhibits a "gradual collapse mode" under large deformation conditions, demonstrating good deformation coordination and energy absorption capacity.

[0180] Example 4: Example of an explosion-proof performance verification test system

[0181] A physical explosion test system was constructed, including an explosion chamber model, explosive loading units, a pressure and strain measurement system, a high-speed photography system, and a data acquisition platform. The chamber incorporates three types of corner structures: flat plate, triangular, and a hybrid combination of both. Two TNT charges were selected: 352g cubic and 600g cylindrical, with the charges fixed at the center of the chamber.

[0182] Pressure sensors were placed near the center and corners of the bulkhead, while strain gauges were placed on the connecting plates and key areas of the bulkhead. Post-explosion, a 3D scanning system was used to acquire residual deformation cloud maps of the bulkhead. Results show that the triangular structure is superior in suppressing corner pressure, while the flat plate structure is superior in controlling overall bulkhead deformation; the hybrid structure exhibits a synergistic effect of both, reducing peak deformation by up to 33%.

[0183] A numerical prediction model coupled with ALE was established based on experimental data. The proportion of foam energy absorption zone and the growth law of plastic energy consumption were analyzed by energy decomposition, and the consistency between simulation prediction and experimental results was verified.

[0184] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for designing an explosion-proof corner flexible connection structure, characterized in that, Includes the following steps: (1) A dynamic response numerical model of the box-shaped compartment is established based on explicit dynamic finite element analysis software. The model includes the bulkhead, corner connection structure, air domain and explosive domain. (2) The reliability of the numerical model is determined by verifying the consistency between the simulation results and the experimental data; (3) Under different connection structure configurations, analyze the pressure distribution, wall deflection and corner strain changes of the compartment under internal explosive load, and determine the blast resistance advantages of the flexible connection structure; (4) Based on the numerical simulation results, a corner flexible connection scheme including foam-filled flat plate structure and foam-filled triangular structure is proposed; (5) By changing the geometric parameters of the connecting plate and the parameters of the filling material, the effect of the flexible connection structure on reducing the maximum deformation of the bulkhead and alleviating local stress concentration is evaluated.

2. The method according to claim 1, characterized in that, The box-shaped compartment has a side length of 1200 mm and a 200 mm diameter vent hole in the center of the top wall to simulate the gas escape behavior after a missile penetrates the compartment wall.

3. The method according to claim 1, characterized in that, The dynamic yielding behavior of the steel structure is described using the Johnson-Cook material model, and the equivalent plastic strain failure threshold is set to 0.

23. The explosive adopts a high-energy combustion material model, and the relationship between the pressure, volume and internal energy of the detonation products is defined by the JWL equation of state. The air component is described using an ideal gas linear polynomial equation of state.

4. A foam-filled flat-plate flexible connection structure for box-type compartments, characterized in that, A flat plate connector is installed at the corner of the compartment, forming a 45-degree angle with the bulkhead. The flat plate and the bulkhead enclose a closed space, which is filled with aluminum foam material. The aluminum foam has energy absorption and shock wave dissipation properties. The flat plate has a side length of 80 mm and a thickness of 4 mm. The density of the foamed aluminum is less than one-twentieth of that of the structural steel. The synergistic effect of the flat plate and aluminum foam makes the strain distribution in the corner area more uniform and reduces the peak deformation of the bulkhead.

5. The foam-filled flat plate type flexible connection structure according to claim 4, characterized in that, The flat panels and bulkheads are constructed using four-node thin-shell units, while the aluminum foam filling layer is constructed using eight-node solid units. Automatic surface-to-surface contact is used between the flat plate and the aluminum foam, and between the bulkhead and the aluminum foam, with a dynamic friction coefficient of 0.

1. The aluminum foam is internally designed with self-contact constraints to prevent negative volume distortion.

6. A foam-filled triangular flexible connection structure for box-shaped compartments, characterized in that, The structure consists of a bottom flat plate and two side plates forming a triangular enclosed space. The bottom flat plate has an angle of 45 degrees with the bulkhead, and the triangular blast-facing surface has a cone angle of θ. The enclosed space is filled with aluminum foam material to absorb shock wave energy and deflect the wavefront. The triangular structure can reduce the convergence of corner pressure and improve the blast resistance and deformation coordination of the compartment structure under explosive load.

7. The foam-filled triangular flexible connection structure according to claim 6, characterized in that, The aluminum foam unit grid is refined to be smaller than the grid length of the triangular connecting plate; The erosion parameter is set to 1 to prevent calculation instability, and the minimum time step is set to positive to avoid negative volume termination.

8. A test system for verifying the explosion-proof performance of corner flexible connection structures, characterized in that, The system includes an explosive chamber model, an explosive loading unit, a pressure sensor, a strain measurement unit, a data acquisition system, and a high-speed camera. The explosion chamber model includes a foam-filled flat panel structure, a foam-filled triangular structure, and a hybrid chamber combining the two structures. The explosive is placed in the center of the compartment and is a cubic TNT charge with a mass of 352 grams or a cylindrical TNT charge with a mass of 600 grams. The explosion load and structural response signals are obtained by pressure sensors and strain gauges, and the dynamic deformation of the bulkhead is recorded synchronously by a high-speed camera.

9. The testing system according to claim 8, characterized in that, The electrical signals generated by the explosion are conditioned and then input into a data acquisition device to be converted into pressure, strain, and displacement parameters. After the explosion, a three-dimensional scanning system was used to measure the deformation of the cabin in order to evaluate the failure mode and blast resistance of the corner flexible connection structure.

10. The testing system according to claim 8, characterized in that, A numerical prediction model for the flexible corner connection structure of the box-shaped compartment was established based on the experimental results. An arbitrary Lagrange-Euler coupling algorithm is used to describe the interaction between the structure and the air domain. The energy absorption ratio and plastic deformation saturation characteristics of flexible connection structures and foam materials under explosive impact were analyzed using the energy decomposition method.

Images