Design method for destroy-resistant structure of separated flight recorder based on multi-layer lattice structure

Abstract

The invention discloses a design method of a disconnectable flight recorder destroy-resistant structure based on a multi-layer lattice structure, and relates to the field of shock-resistant structure design, comprising the following steps: designing a disconnectable flight data recording system destroy-resistant protective structure; designing a multi-layer lattice structure of a mechanical shell layer; establishing an impact numerical simulation model for the multi-layer lattice cell element structure, and verifying the axial compression performance of the structure based on an explicit dynamics method; a crushable foam model is adopted to simulate buckling deformation of the lattice structure, and protection structure impact simulation analysis is carried out to verify the overall impact strength of the recorder protection structure; a design variable is selected, a test design method is selected to establish a response surface agent model based on the simulation sample, and an optimization algorithm is selected to carry out impact resistance optimization design; the problem of crash protection of the separated flight data recording system is solved, the design and optimization of the shock-resistant protection structure of the separated flight data recording system are realized, and the method has a good engineering application prospect.

Description

Technical Field

[0001] The invention belongs to the field of impact-resistant structure design, and in particular relates to a method for designing an anti-destruction structure of a separated flight recorder based on a multi-layer lattice structure. Background Art

[0002] The flight data recorder's protective structure refers to the design and materials that can protect the internal module recording medium after withstanding strong impact loads. The separated flight data recorder system faces strong impact, high overload working environment and various complex environmental conditions. The recorder's protective structure must ensure the survivability and working reliability of the internal storage module.

[0003] The anti-destruction protection structure of the flight data recorder is usually composed of a shell, a temperature insulation layer and an insulation layer. The shell is usually made of a metal alloy material with high strength and high toughness mechanical properties, and the temperature insulation layer and the insulation layer are made of thermal protection materials or non-metal buffer materials. The storage module is encapsulated in the potting material to further delay and weaken the damage to the storage module caused by the impact.

[0004] Flight data recorders play an important role in aircraft accident investigation, maintenance and flight tests. Their crash protection has always been a research topic for scholars at home and abroad. The currently widely used fixed recorders weigh up to 20 to 30 kilograms. Although they can withstand 3400G acceleration (6.5ms), 1100℃ high temperature (1 hour) and 6000 meters underwater burial (30 days), there are still many flight accidents where the black box cannot be found or the black box data cannot be recovered. The separated flight data recording system can solve the pain points of the traditional recorder being difficult to search and long decryption time. It is necessary to carry out anti-impact protection research on the separated flight data recording system, which has good engineering application prospects. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a method for designing a destructible structure of a separate flight recorder based on a multi-layer lattice structure, so as to solve the problem of crash protection of the ejection recorder in the system.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The design method of the survivable structure of a separated flight recorder based on a multi-layer lattice structure has the following steps:

[0008] 1) Designing an anti-destruction protection structure according to the anti-impact protection performance index and design principle of the separated emergency flight data recording system of civil aircraft, wherein the anti-destruction protection structure includes a mechanical shell layer structure;

[0009] 2) Based on the mechanical shell layer structure, a multi-layer lattice structure design is performed on the mechanical shell layer based on the lightweight design criteria of the impact-resistant protective structure;

[0010] 3) According to the mechanical shell layer lattice structure, an explicit dynamics impact numerical simulation model of the multi-layer lattice cell structure based on the explicit dynamics method is established, and the impact resistance of the cell structure is analyzed based on the numerical simulation results of the explicit dynamics impact numerical simulation model;

[0011] 4) According to the numerical simulation results of the explicit dynamic impact numerical simulation model, the lattice structure is simplified into a solid structure through an equivalent model method, and an overall explicit dynamic numerical simulation model of the protective structure based on the explicit dynamic method is established, and the overall anti-destruction performance of the protective structure is verified through the numerical simulation results of the explicit dynamic numerical simulation model;

[0012] 5) According to the lattice structure of the mechanical shell layer, key structural parameters are selected as design variables, and experimental design methods are selected based on the design variables to form experimental sample points. A simulation database of the impact resistance of the cellular structure is established based on the experimental sample points through the impact numerical simulation model in step 3), and an optimization algorithm is selected by establishing a proxy model to carry out the optimization design of the impact resistance of the lattice structure.

[0013] Furthermore, in the step 2), the multi-layer lattice structure of the mechanical shell layer is designed as a shell outer layer-opening cavity lattice cell structure-shell inner layer design, and the open cavity lattice cell structure is approximately a cube-shaped protective structure with openings at the upper and lower bottoms.

[0014] Furthermore, in the step 3), the explicit dynamics numerical simulation model is a simple stacked multi-layer lattice cell structure model, and axial compression simulation is completed under the impact of a rigid plate at a set speed, and the impact resistance of the structure is evaluated based on the numerical simulation results; the numerical simulation results include the deformation of the model, stress cloud map, impact load and impact displacement; the explicit dynamics method is to use the central difference method to perform explicit time integration to solve the motion equation.

[0015] Furthermore, in the step 4), the equivalent model method is to equate the elastoplastic model of the lattice structure metal alloy material to the isotropic crushable foam material model provided in the finite element software, and the impact numerical simulation result is the engineering stress-strain curve of the lattice cell structure. The engineering stress-strain curve is converted into the hardening curve required for the crushable foam material model through formula transformation, and the material parameters of the crushable foam properties are calculated; the overall impact resistance evaluation of the protective structure is to analyze the stress peak and deformation of the circuit board during the numerical simulation process to verify the impact strength of the protective structure.

[0016] As a preferred trial method of the present application, the protective structure includes a mechanical shell layer, a buffer protective layer, a circuit body, a battery, and a steel plate; the overall explicit dynamic numerical simulation model of the protective structure is that the protective structure hits the hard surface of the steel plate at a set speed;

[0017] Furthermore, in the step 5), the key structural parameters are used as design variables, and the optimal Latin hypercube method is used to perform experimental design of sample points;

[0018] The simulation database of the cell structure is constructed based on the sample points of the selected design variables. The impact numerical simulation model in step 3) is used to perform axial compression simulation analysis on the model of each sample point. The sample points of the design variables and the simulation results obtained constitute the simulation database.

[0019] Furthermore, the proxy model is a polynomial response surface proxy model, which establishes a polynomial function to fit the relationship between the design variables and the impact resistance of the cellular structure; selects the second-generation non-inferior sorting genetic algorithm as the optimization algorithm, takes the effective range of the structural parameters and the impact resistance as constraints, and selects the impact resistance evaluation index as the objective function to achieve the optimal design of the impact resistance of the lattice cellular structure.

[0020] Beneficial effects of the present invention:

[0021] The present invention takes the anti-impact protection design of a separate flight data recorder system as the research background, and based on the strong vibration, high overload, strong impact working environment and complex natural environmental conditions faced by the system, a design method for the anti-destruction structure of a separate flight recorder based on a multi-layer lattice structure is proposed. The present invention ensures the survivability and working reliability of the storage module of the separate flight data recorder system under external high impact loads and complex environmental conditions. At the same time, based on the lightweight design criteria of the protective structure, the lattice structure of the mechanical shell layer is designed, and the lattice structure is optimized and designed using a multi-objective optimization method based on an agent model, and the modeling and numerical simulation process is simplified using an equivalent model method. Compared with the protective structure of a traditional recorder, the anti-impact protection structure of the separate flight data recorder system designed by the present invention uses a metal lattice structure on the basis of ensuring the survivability and working reliability of the recorder. The structure is lighter in weight, and the use of additive manufacturing technology shortens the engineering cycle, realizing the integrated design of structure and function. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of the method of the present invention;

[0023] Figure 2 Design drawings of the protective structure for the detachable flight data recorder;

[0024] Figure 3 This is the design drawing of the multi-layer lattice structure of the mechanical shell layer;

[0025] Figure 4 It is a schematic diagram of the model of the lattice structure;

[0026] Figure 5 This is the model diagram of impact numerical simulation;

[0027] Figure 6 Comparison diagram of the model data fitting curve and experimental curve for crushable materials;

[0028] Figure 7 This is a schematic diagram of the numerical simulation of the impact of the overall protective structure;

[0029] Figure 8 This is the numerical simulation result diagram of the impact of the protective structure in the vertical direction;

[0030] Fig. 9 This is the stress distribution diagram of the circuit board in the vertical impact simulation result;

[0031] Fig.10 This is the numerical simulation result diagram of the protective structure collision in the lateral direction;

[0032] Fig.11 This is the stress distribution diagram of the circuit board as a result of the side impact simulation. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments and drawings. The contents mentioned in the implementation modes are not intended to limit the present invention.

[0034] like Figure 1 As shown, the present invention is a design method for a detachable flight recorder anti-destruction structure based on a multi-layer lattice structure, and the specific implementation method is as follows:

[0035] Specifically, the step 1) includes:

[0036] The impact resistance performance index of the anti-destruction protection structure is based on some requirements of the European Civil Aviation Equipment Organization EUROCAE standard ED-112A "Minimum Performance Requirements for Crash-Resistant Airborne Recording Systems" cited in the Chinese Civil Aviation Technical Standard CTSO-C124c "Flight Data Recorder". The crash protection requirements for ejection recorders in terms of strong impact resistance stipulate: In the most vulnerable direction of the crash protection component in the most likely landing attitude, use a hard surface (a 50mm thick steel plate with a diameter greater than the entire size of the recorder) to hit or impact this surface at a minimum speed of 46.33m / s (152f / s).

[0037] The impact resistance design principle of the anti-destruction protection structure is based on the stress wave attenuation theory. Stress waves are mainly isolated by the difference in acoustic impedance between the external mechanical shell and the internal buffer material. After the impact protection structure collides with the hard surface, stress is generated. The stress propagates in the protection structure in the form of stress waves. Under the impact load, the recorder's protection system can store and dissipate the energy generated by the impact. The stress wave has reflection and transmission phenomena at the boundary of the medium with variable cross-section, and has the characteristics of propagation attenuation, which is the stress wave attenuation theory.

[0038] Assume that the stress wave intensity of the incident layer material is σ1, and the wave impedance of the material is Z1; the stress wave intensity of the transmission layer material is σ2, and the wave impedance of the material is Z2. Then the stress wave propagates from the incident layer to the transmission layer:

[0039]

[0040] It is not difficult to see that when the wave impedance Z1 of the incident layer material is much larger than the wave impedance Z2 of the transmission layer, the stress wave intensity σ2 is much smaller than σ1, that is, when a stress wave with a very high peak value is transmitted from a material with high wave impedance to a material with low wave impedance, its intensity will be greatly reduced.

[0041] The design of the mechanical shell layer mainly uses high-strength and rigid metal alloys to resist the deformation of the shell, and isolates stress waves through the difference in acoustic impedance with the internal buffer material. The mechanical shell layer faces a working environment with strong vibration, high overload, and strong impact. The design must consider the comprehensive mechanical properties of the material, as well as the system maintainability, reliability, and system performance, and minimize the mass of the protective structure while ensuring the impact resistance.

[0042] The design of the buffer protection layer is mainly to reduce the vibration of the circuit board through packaging, isolate the external environment and achieve insulation protection, and use the difference in acoustic impedance with the external mechanical shell to isolate stress waves. The design of the buffer protection layer should take into account the material's energy absorption capacity, mechanical properties, thermal properties, operability and electrical properties.

[0043] like Figure 2 As shown in the figure, a cylindrical protective structure with a diameter of 90 mm and a height of 140 mm was designed based on the impact resistance performance index and design principles of the anti-destruction protective structure, including a circuit board, a battery assembly, a mechanical shell layer, and a buffer protective layer. The rounded corner design avoids stress concentration. The material of the mechanical shell layer of the protective structure is AlSi10Mg aluminum alloy, and the material of the buffer protective layer is modified epoxy resin glue.

[0044] Specifically, the step 2) includes:

[0045] like Figure 3As shown, based on the design principle of lightweight impact protection structure, a multi-layer lattice structure design is adopted in the design of the mechanical shell layer. For the 8mm thick mechanical shell layer of the anti-destruction protection structure, an outer shell-opening cavity lattice structure-inner shell is designed. The thickness of the outer shell H1 and the thickness of the inner shell H2 are both 1mm, and the uniform wall thickness T of the shell cell is 1mm. Each cell structure is approximately a cavity cube with a length, width and height of 6mm, and holes are opened at the upper and lower bottoms. The hole diameter D is 3mm, which further reduces the structural mass and can also solve the problem of powder discharge during 3D printing. Figure 4 The schematic diagram of the model of the lattice structure is shown. At the same time, the horizontal perforated grille can ensure the lateral impact resistance of the structure and ensure that the impact protection performance of the protective structure in all possible directions meets the requirements.

[0046] Specifically, the step 3) includes:

[0047] like Figure 5 As shown in Figure 1, a numerical impact simulation model of the structure is established in the finite element software ABAQUS based on the lattice cell structure. The basic material parameters of the model are shown in Table 1.

[0048] Table 1

[0049]

[0050] The cell structure is placed between the upper and lower rigid plates. The lower plate is coupled to the structural reference point and fully fixed. The upper rigid plate is compressed downward at a uniform speed of 10 m / s, and the impact compression distance is 75% of the length of the structure. General contact is set between the rigid plate and the structure, a penalty function is set for tangential contact, and hard contact is set for normal contact.

[0051] The upper and lower plates are considered as rigid bodies, and C3D8R units are selected. The cell structure belongs to the shell unit, and the mesh type is the reduced integration SR4 unit. The mesh sensitivity verification analysis of the impact numerical simulation model is carried out, and the energy conservation problem in the numerical simulation process is verified. During the axial compression process, the deformation and stress distribution of the output model, as well as the reaction force and displacement curves of the upper plate reference point over time are output to obtain the compression impact force-displacement curve of the structure. After calculation, the model's energy absorption, specific energy absorption, initial peak force and other impact resistance evaluation indicators are obtained.

[0052] The calculation formula for energy absorption is:

[0053]

[0054] Where F(x) represents the compressive load and x represents the compressive displacement.

[0055] The calculation formula of specific energy absorption is:

[0056]

[0057] Wherein, M represents the mass of the energy absorbing structure.

[0058] The initial peak force is the peak impact force at the initial stage of compression, which is obtained from the impact force-displacement curve.

[0059] Based on the numerical simulation results, the influence of the change of impact velocity on the impact resistance of the structure is analyzed. First, the deformation of the model at different impact velocities is compared; then, the energy absorption of the model at different impact velocities is compared; finally, the initial peak force of the model at different impact velocities is compared.

[0060] Based on the results of numerical simulation, the influence of the change of wall thickness on the impact resistance of the structure is analyzed. First, the deformation mode of different wall thickness models is observed during the numerical simulation process, and three time points, namely the elastic section, platform section, and densification section, are selected for comparison. The uniform and stable deformation of the structure means high impact strength. Then, the specific energy absorption and initial peak force of different wall thickness models are compared. The change of wall thickness will affect the stiffness of the structure, and the impact resistance index will change accordingly. Finally, the stress distribution of different wall thickness models in the elastic stage is compared. The stress distribution in the elastic stage affects the yield behavior of the structure.

[0061] Based on the results of numerical simulation, the influence of the change of aperture on the impact resistance of the structure is analyzed. First, the deformation mode of different aperture models is observed during the numerical simulation process, and the three time points of elastic section, platform section and densification section are also selected for comparison. The uniform and stable deformation of the structure means high impact strength; then, the specific energy absorption and initial peak force of different aperture models are compared. The change of aperture affects the strength of the connection of the multilayer cell structure, directly affects the deformation of the structure, and the impact resistance index will change accordingly; finally, the stress distribution of different wall thickness models in the elastic stage is compared. The stress distribution in the elastic stage affects the yield behavior of the structure.

[0062] Specifically, the step 4) includes:

[0063] The equivalent model method is that the lattice structure elastic-plastic model of the protective structure mechanical shell layer selects the crushable foam material model of the isotropic hardening criterion provided in the ABAQUS finite element software. As shown in Table 2, the material parameters required by the model are the elastic properties of the material and the crushable foam properties.

[0064] Table 2

[0065]

[0066]

[0067] Based on the simulation results of the impact numerical simulation model in step 3), the engineering stress-engineering strain curve in the impact numerical simulation process of the optimized structure can be obtained, which can be converted into a true stress-true strain curve through the formula and input into the ABAQUS software in the form of a data table. The data fitting curve and the experimental curve are shown in Figure 6 As shown. For general metal alloy materials, the true stress σ true and the true strain ε true and engineering stress σ eng and engineering strain ε eng The relationship between: true =σ eng (1+ε eng )

[0068] ε true =ln(1+ε eng )

[0069] Other material models and related model parameters of the protective structure are shown in Table 3.

[0070] Table 3

[0071]

[0072] The ABAQUS explicit dynamics method is used to simulate the experiment. The simulation diagram is shown in Figure 7 As shown, a steel plate is used to simulate a hard surface, and a fixed constraint is applied to the bottom of the steel plate. The circuit board, battery assembly, buffer protection layer, and mechanical shell layer models are assembled, and the material model and material parameters are defined. C3D8R units are used for meshing, and general contact and penalty functions are set during the simulation process. The initial velocity of 46.33 m / s is applied to the protective structure as a whole, so as to hit the steel plate at a direction of 60° to the surface of the steel plate.

[0073] The simulation results are as follows Figure 8 As shown in Figure 2, at t = 0.49ms, the protective structure hits the steel plate surface; at t = 0.84ms, the deformation of the structure reaches the maximum; at t = 0.96ms, the protective structure leaves the steel plate surface. Fig. 9 As shown in the figure, among the three circuit boards, the stress of the bottom circuit board close to the steel plate is greater, and finally it is verified that the stress peak of the circuit board is far less than the allowable strength of the material. Under high-speed impact, only the mechanical shell undergoes a small deformation, and the circuit board does not have excessive stress and obvious deformation, so the impact resistance of the protective structure is verified.

[0074] In order to verify the impact resistance of the protective structure in the lateral direction, a finite element simulation analysis was performed on the model impacting the steel plate in the lateral direction. The simulation results are shown in Figure 2. Fig.10As shown in the figure, the protective structure has a small deformation under the impact load. In terms of duration, the contact time between the structure and the steel plate, the time required to reach the maximum deformation, and the time to rebound from the steel plate surface are shorter, which means that the structure needs to withstand a stronger impact load in a shorter time. Fig.11 As shown, the peak stress of the circuit board during the impact is 167MPa, which is within the maximum stress range that the circuit board can withstand. Therefore, the protective structure still maintains good impact resistance during lateral impact.

[0075] Specifically, the step 5) includes:

[0076] Based on the impact numerical simulation model in step 3), with shell thickness H1, shell thickness H2, cell wall thickness T and opening diameter D as design variables, 20 sample points were selected within the parameter range of the design variables through optimal Latin hypercube design to ensure the uniform distribution of the sample points in the design space, and the relationship between the design variables of the response surface proxy model and the impact resistance of the structure was established. The mathematical expression of the actual response between the design variables of the polynomial response surface model and the objective function is:

[0077]

[0078] In the formula, f(x) is the actual value of the response and is an unknown function; is the response approximation, which is a known polynomial; ε is the random error between the approximation and the actual value, which obeys (0,σ 2 )’s standard normal distribution; x is an m-dimensional independent design variable; β i is the unknown coefficient of the basis function; M is the basis function φ i The number of (x).

[0079] In this optimization problem, a second-order polynomial response surface surrogate model is used to establish the objective function, and its approximate response surface can be expressed as:

[0080]

[0081] The second generation non-inferior sorting genetic algorithm is a multi-objective genetic algorithm based on the basic operations of selection, crossover and mutation of genetic algorithms, and uses the ideas of fast non-dominated sorting and crowding distance sorting for optimization.

[0082] The second generation non-inferior sorting genetic algorithm uses the idea of ​​"crowding distance" and "crowding distance sorting" on the basis of general genetic algorithms to sort individuals with the same Pareto order, which can make the individuals of the next generation closer to the Pareto frontier. The crowding distance of each individual is the sum of the differences in the sub-objective functions of the two individuals before and after the individual. The crowding distance of individual i with r sub-objectives is:

[0083]

[0084] in, For individual i in sub-goal f k The function value on .

[0085] In this optimization problem, the impact resistance indexes SEA and PCF of the structure are used as the objective functions. In the two-dimensional target, the above crowding distance calculation formula is:

[0086]

[0087] The second generation non-inferior sorting genetic algorithm uses the simulated binary crossover (SBX) method for crossover and mutation operations. The parent population is crossovered and mutated to obtain a sub-population, and the two populations are merged to obtain a new parent population. In the population, the individuals in the population are compared pairwise according to their objective function vectors through the target space Pareto optimal relationship, and the individuals are controlled in turn for sorting. Individuals in the same Pareto layer are compared by crowding distance, and individuals with larger crowding distance are selected; individuals in different Pareto layers, individuals close to the Pareto frontier are selected.

[0088] SBX crossover operation:

[0089]

[0090] in, and represents the two individuals produced in the tth generation, and represents the two individuals produced in the t+1th generation; β qi It is obtained dynamically and randomly through the distribution factor.

[0091] SBX mutation operation:

[0092]

[0093] in, and represents the upper and lower bounds of the i-th variable; η m is the distribution index; u is a random number between 0 and 1.

[0094] like Figure 8 As shown, the second generation non-inferior sorting genetic algorithm comprises the following steps:

[0095] Step 1) Initialize the population, set the population size, and set the number of evolution generations;

[0096] Step 2) sorting the population according to the non-dominated relationship, and obtaining the first generation offspring population through selection, crossover, and mutation;

[0097] Step 3) Merge the parent population with the child population and perform a fast non-dominated sort.

[0098] Step 4) Sort the individuals by crowding distance, and select individuals to form a new parent population based on non-dominated relationships and crowding distances;

[0099] Step 5) Produce a new generation of offspring population through selection, crossover, and mutation;

[0100] Step 6) determines whether the termination condition is met, if not, repeats steps 3) to 6).

[0101] After the optimization is completed, the optimal parameter configuration of the lattice structure is obtained. Based on the optimization results and the impact numerical simulation model in step 3), the axial compression analysis is re-performed. The simulation results are compared with the optimization results. The smaller error indicates that the reliability of the optimization model is higher.

[0102] The present invention has many specific application paths. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principle of the present invention. These improvements should also be regarded as the protection scope of the present invention.

Claims

1. A design method for a detachable flight recorder anti-destruction structure based on a multi-layer lattice structure, characterized in that: Here are the steps: 1) Design an anti-destruction protection structure based on the impact protection performance indicators and design principles of the separated emergency flight data recording system of civil aircraft, wherein the anti-destruction protection structure includes a mechanical shell layer structure; 2) Based on the mechanical shell layer structure, a multi-layer lattice structure design is performed on the mechanical shell layer based on the lightweight design criteria of the impact-resistant protective structure; 3) According to the mechanical shell layer lattice structure, an explicit dynamics impact numerical simulation model of the multi-layer lattice cell structure based on the explicit dynamics method is established, and the impact resistance of the cell structure is analyzed based on the numerical simulation results of the explicit dynamics impact numerical simulation model; 4) According to the numerical simulation results of the explicit dynamic impact numerical simulation model, the lattice structure is simplified into a solid structure through an equivalent model method, and an overall explicit dynamic numerical simulation model of the protective structure based on the explicit dynamic method is established. The overall anti-destruction performance of the protective structure is verified through the numerical simulation results of the explicit dynamic numerical simulation model; 5) According to the lattice structure of the mechanical shell layer, key structural parameters are selected as design variables, and experimental design methods are selected based on the design variables to form experimental sample points. A simulation database of the impact resistance of the cellular structure is established based on the experimental sample points through the impact numerical simulation model in step 3), and an optimization algorithm is selected by establishing a proxy model to carry out the optimization design of the impact resistance of the lattice structure.

2. The method for designing a survivable structure of a separated flight recorder based on a multi-layer lattice structure according to claim 1, characterized in that: In the step 2), the multi-layer lattice structure of the mechanical shell layer is designed as a shell outer layer-opening cavity lattice cell structure-shell inner layer design, and the open cavity lattice cell structure is approximately a cube-shaped protective structure with openings at the upper and lower bottoms.

3. The method for designing a survivable structure of a separated flight recorder based on a multi-layer lattice structure according to claim 1, characterized in that: In the step 3), the explicit dynamics numerical simulation model is a simple stacked multi-layer lattice cell structure model, and axial compression simulation is completed under the impact of a rigid plate at a set speed, and the impact resistance of the structure is evaluated based on the numerical simulation results; the numerical simulation results include the deformation of the model, stress cloud diagram, impact load and impact displacement; the explicit dynamics method is to use the central difference method to perform explicit time integration to solve the motion equation.

4. The method for designing a survivable structure of a separated flight recorder based on a multi-layer lattice structure according to claim 1, characterized in that: In the step 4), the equivalent model method is to equate the lattice structure metal alloy material elastic-plastic model to the isotropic crushable foam material model provided in the finite element software, and the impact numerical simulation result is the engineering stress-strain curve of the lattice cell structure. The engineering stress-strain curve is converted into the hardening curve required by the crushable foam material model through formula transformation, and the material parameters of the crushable foam properties are calculated; the overall impact resistance evaluation of the protective structure is to analyze the stress peak and deformation of the circuit board during the numerical simulation process to verify the impact strength of the protective structure.

5. The method for designing a survivable structure of a separated flight recorder based on a multi-layer lattice structure according to any one of claims 1 to 4, characterized in that: The protective structure comprises a mechanical shell layer, a buffer protective layer, a circuit body, a battery, and a steel plate; the overall explicit dynamic numerical simulation model of the protective structure is that the protective structure hits the hard surface of the steel plate at a set speed.

6. The method for designing a survivable structure of a separated flight recorder based on a multi-layer lattice structure according to claim 1, characterized in that: In the step 5), the key structural parameters are used as design variables, and the optimal Latin hypercube method is used to perform experimental design of sample points; The simulation database of the cell structure is constructed based on the sample points of the selected design variables. The impact numerical simulation model in step 3) is used to perform axial compression simulation analysis on the model of each sample point. The sample points of the design variables and the simulation results obtained constitute the simulation database.

7. The method for designing a survivable structure of a separated flight recorder based on a multi-layer lattice structure according to claim 1, characterized in that: The surrogate model is a polynomial response surface surrogate model, which establishes a relationship between a polynomial function fitting design variable and the impact resistance of a cell structure; selects a second-generation non-inferior sorting genetic algorithm as an optimization algorithm, takes the effective range of structural parameters and the impact resistance as constraints, and selects an impact resistance evaluation index as an objective function, thereby achieving an optimized design of the impact resistance of a lattice cell structure.

Images