Finite element analysis-based unlocking simulation and prestress influence analysis method for pyrotechnic separation device

Abstract

The invention discloses a pyrotechnic separation device unlocking simulation and prestress influence analysis method based on finite element analysis, a pyrotechnic separation device comprises a structural plate, a stud, a shell, an air cylinder, a locking flap, a piston and explosive, and the method comprises the following specific steps: S1, establishing a finite element model of the pyrotechnic separation device according to the actual situation of pyrotechnic impact; s2, establishing a related prestress analysis model, and solving a prestress solution of each unit; and S3, importing a pre-stress result into the pyrotechnic separation finite element model to realize separation unlocking process simulation and pre-stress influence analysis. According to the pyrotechnic separation device unlocking simulation and prestress influence analysis method based on finite element analysis, the prestress result of each unit is calculated, finite element analysis is carried out on the pyrotechnic separation device by using an S-ALE fluid-solid coupling method, the modeling efficiency is high, the simulation precision is high, and the method is closer to reality.

Description

Technical field:

[0001] The invention relates to an unlocking simulation and prestress influence analysis method of a pyrotechnic separation device based on finite element analysis, and belongs to the field of pyrotechnic separation. Background technology:

[0002] In aerospace engineering, pyrotechnic separation devices are widely used to achieve the connection-separation function of launch vehicles and satellites. Common pyrotechnic separation devices can be simply divided into three types according to their different configurations: point-type pyrotechnic separation devices, line-type pyrotechnic separation devices, and point-line mixed types. For example, point-type ones include explosive bolts, pyrotechnic separation devices, shear pins, and pyrotechnic locks; line-type ones include pyrotechnic cutting ropes and expansion tubes; and point-line combination types include belt-type pyrotechnic separation devices. These pyrotechnic separation devices usually have the advantages of short action time and high reliability, which are favored by aerospace engineers. Before launch, the satellite is fixed to the last stage of the launch vehicle through a pyrotechnic separation device, and a certain preload is applied to the pyrotechnic separation device to generate reliable connection stiffness at the satellite-rocket connection interface. When receiving the separation command, these pyrotechnic separation devices are triggered by electric detonators, and the internal pyrotechnic products ignite and explode to produce detonation product gas. The gas drives the internal structure to move or uses the shock wave generated by it to act on the weak parts of the structure to cause fracture, thereby completing the unlocking action. Due to the impact of the pyrotechnic explosion, a strong shock wave will be generated in the internal structure of the pyrotechnic separation device, which will gradually be transmitted to the far-field satellite structure, causing an impact response of the satellite structure. This structural impact response caused by the shock wave during the satellite-rocket separation process is characterized by high frequency, transient and high magnitude, and is generally referred to as the satellite-rocket separation shock environment. Usually, the satellite-rocket separation shock environment has little effect on the satellite structure, but it will cause damage to components or equipment that are sensitive to shock, such as relay disconnection, ceramic material cracking, brazing shedding and antenna breakage, etc., which will cause single-machine equipment failure or even the failure of the entire space mission.

[0003] Therefore, the accurate prediction and simulation of the pyrotechnic impact environment of complex satellite structures during satellite-rocket separation has become a bottleneck restricting the development of my country's satellite research and development towards short cycles and economical development, and is a hot issue that needs to be urgently resolved in the current aerospace field. Summary of the invention:

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a method for unlocking simulation and prestress influence analysis of a pyrotechnic separation device based on finite element analysis. It calculates the prestress results of each unit and uses the S-ALE fluid-solid coupling method to perform finite element analysis on the pyrotechnic separation device. It has high modeling efficiency and simulation accuracy and is closer to reality.

[0005] The technical solutions adopted by the present invention are as follows: A method for unlocking simulation and prestress influence analysis of an explosive separation device based on finite element analysis. The explosive separation device includes a structural plate, a stud, a housing, a cylinder, a locking flap, a piston, and explosives. The specific steps are as follows:

[0006] Step S1: Establish a finite element model of the explosive separation device according to the actual situation of explosive impact;

[0007] Step S2: Establish a relevant prestress analysis model and solve the prestress solutions of each element;

[0008] Step S3: Import the prestress results into the explosive separation finite element model to realize the simulation of the separation unlocking process and the analysis of the influence of prestress.

[0009] Further, the specific steps of Step S1 include:

[0010] Step S11: Use SolidWorks to establish a three-dimensional model of the explosive separation device, simplify the three-dimensional model into a quarter model, and then import the quarter model into HyperMesh software for mesh generation. The structured ALE (S-ALE) algorithm in LS-DYNA is used. The algorithm defines the flow field action area through three-dimensional coordinates and directly generates structured three-dimensional meshes;

[0011] Step S12: Define the constitutive and state equations of each component and air in the explosive separation device. The structural plate, stud, housing, cylinder, locking flap, and piston adopt the *MAT_ELASTIC linear elastic constitutive equation. The structural plate adopts the *MAT_ELASTIC constitutive equation, the stud and the locking flap adopt the *MAT_ELASTIC constitutive equation, and the cylinder, piston, and housing adopt the *MAT_RIGID constitutive equation; The explosive is selected with the *HIGH_EXPLOSIVE_BURN constitutive equation and adopts the three-term JWL state equation. Its model expression is as follows:

[0012] p = Fp eos (V,E)

[0013] In the formula, F is the combustion coefficient, p eos is the pressure of the state equation, V is the relative volume, and E is the internal energy density per unit initial volume;

[0014] Air adopts the *MAT_NUL constitutive equation, and the state equation adopts *EOS_LINEAR_POLYNOMIAL. The state equation expression is as follows:

[0015] p = C0 + C1μ + C2μ 2 + C3μ 3 +(C4 + C5μ + C6μ 2 )E

[0016]

[0017] In the formula, C0, C1, C2, C3, C4, C5, and C6 are the coefficients of the linear state equation, and ρ and ρ0 are the current density and the reference density, respectively;

[0018] Finally, explosives and air are automatically generated through the two keywords *ALE_STRUCTURED_MULTI-MATERIAL_GROUP and *ALE_STRUCTURED_MESH_VOLUME_FILLING in the S-ALE method.

[0019] Step S13: Set the boundary conditions of the pyrotechnic separation finite element model. Apply symmetric constraints to the solid domain using *BOUNDARY_SPC_SET, set the fluid domain boundary using NONREFL and SYM in *BOUNDARY_SALE_MESH_FACE, and at the same time control the explosive detonation time through the INITIAL_DETONATION keyword;

[0020] Step S14: Perform fluid-structure interaction settings on the finite element model. The structured mesh generated by the keywords *ALE_STRUCTURED_MESH and *ALE_STRUCTURED_MESH_CONTROL_POINTS directly calls the S-ALE solver during the solution process. Finally, fluid-structure interaction is realized using the *ALE_STRUCTURED_FSI keyword. The fluid-structure interaction adopts the penalty function method to automatically control the number of coupling points, leakage control, normal type, edge coupling, and erosion coupling. In this keyword card, the user needs to input three important parameters, namely the coupling material, penalty factor, and friction coefficient, to control the fluid-structure interaction;

[0021] Step S15: Set the surface-to-surface contact of the finite element model using *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE. At the same time, set the calculation time, time step, output, and energy of the finite element model. Finally, start the MPP (distributed computing) solver of the S-ALE algorithm through the *CONTROL_MPP_DECOMPOSITION_DISTRIBUTE_ALE_ELEMENTS keyword card.

[0022] Further, the specific steps of step S2 include:

[0023] Step S21: Establish a prestress calculation model, calculate the prestress of each element, and import it into the subsequent finite element analysis model as the initial condition. The preload is applied by applying a certain torque to the stud in the split bolt. The relationship between the torque applied to the stud of the split bolt and the prestress generated by the stud cross-section is as follows:

[0024]

[0025] In the formula, σ is the prestress of the stud cross-section, T is the torque applied to the stud, K is the torque coefficient, taking 0.2, and d is the stud diameter;

[0026] Step S22: Implement the prestress loading through the three keyword cards of *DATABASE_CROSS_SECTION_PLANE, *INITIAL_STRESS_SECTION, and *DEFINE_CURVE;

[0027] Step S23: Set the corresponding calculation time, time step, output, energy, and hourglass control, and set the implicit solver through *CONTROL_IMPLICIT_AUTO, *CONTROL_IMPLICIT_GENERAL, and *CONTROL_IMPLICIT_SOLUTION;

[0028] Step S24: Finally, implement the conversion of the implicit result to the explicit result by setting the *INTERFACE_SPRINGBACK_LSDYNA keyword.

[0029] Furthermore, the specific steps of step S3 include:

[0030] Step S31: Import the prestress result into the pyroseparation finite element model. In the pyroseparation finite element model, import the simulation analysis result file 'dynain' of the prestress in step S2, and delete the duplicate elements generated during the import. In this way, the relevant data of the prestress are obtained in the two keywords of *INITIAL_STRAIN_SOLID and *INITIAL_STRESS_SOLID of the model to be solved;

[0031] Step S32: Open LS-run and perform finite element analysis. Select the appropriate number of NCPUs and MEMORY, select lsdyna_mpp_dp_impi.exe, that is, the double-precision MPP solver, and achieve parallel computing by allocating independent CPU memory.

[0032] Further, in step S12, when the explosive starts to detonate, the burning time of each unit is calculated by dividing the distance from the detonation point to the unit center by the detonation velocity D of the explosive. If many detonation points are defined, the closest detonation point will be determined, and the burning coefficient is taken as the maximum value:

[0033] F = max(F1, F2)

[0034] The JWL equation of state is as follows:

[0035]

[0036] In the formula, A, B, R1, R2, and ω are undetermined parameters, and their parameters are calibrated by the cylindrical detonation test.

[0037] The present invention has the following beneficial effects:

[0038] (1) High modeling efficiency and high simulation accuracy. By adopting the structured ALE (S-ALE) fluid-structure interaction algorithm, a structured three-dimensional grid is directly generated, avoiding the complex processing flow of traditional unstructured grids, significantly shortening the modeling time and reducing memory occupancy. At the same time, the node connection relationship of the structured grid is clear, simplifying the fluid-structure interaction search algorithm and improving the simulation accuracy of the propagation of explosion shock waves.

[0039] (2) Truly reflect the influence of prestress on the separation process. By independently establishing a prestress analysis model, accurately calculating the pre-tightening force of the stud, and importing it as an initial condition into the dynamic unlocking simulation, the problem of error accumulation caused by directly loading prestress in the traditional method is solved. Combining the torque-prestress relationship ensures the engineering accuracy of the pre-tightening force loading, making the simulation results closer to the actual satellite-rocket separation conditions.

[0040] (3) Efficiently handle transient explosion and large deformation problems. Adopting the S-ALE method combined with the MPP (distributed computing) solver, the solution efficiency is greatly improved through parallel computing, which is suitable for high-fidelity simulation of the transient response of explosion shock waves. The fluid-structure interaction automatically controls the number of coupling points and leakage through the penalty function, reducing manual intervention, and at the same time supporting the simulation of the dynamic mixing process of multi-material explosion products.

[0041] (4) Optimization of the constitutive model and equation of state. Different constitutive models (such as elastic constitutive, rigid body constitutive, detonation combustion constitutive) are selected according to the characteristics of different components, and the JWL equation of state is used to accurately describe the detonation process of explosives. Combining the linear polynomial equation of state to simulate the aerodynamic behavior significantly improves the reliability of the analysis of the propagation of explosion shock waves and the structural response.

[0042] (5) It has strong engineering practicability. By means of quarter-model simplification, symmetric boundary condition setting and implicit-explicit result conversion technology (*INTERFACE_SPRINGBACK_LSDYNA), while ensuring the calculation accuracy, the model complexity is reduced, providing an efficient and reliable simulation tool for the design optimization and shock environment prediction of pyrotechnic separation devices in aerospace engineering. Description of the Drawings:

[0043] Figure 1 This is a flowchart of the method for simulating the unlocking of a pyrotechnic separation device and analyzing the influence of prestress based on finite element analysis according to the present invention.

[0044] Figure 2 This is a schematic diagram of the three-dimensional model structure of the pyrotechnic separation device in the specific embodiment of the present invention.

[0045] Figure 3 This is a schematic diagram of the quarter-mesh model structure in the specific embodiment of the present invention.

[0046] Figure 4 This is a schematic diagram of the finite element model structure for prestress calculation in the specific embodiment of the present invention.

[0047] Figure 5 This is the Von-Mises stress nephogram of the prestress model in the specific embodiment of the present invention.

[0048] Figure 6 This is a diagram of the pyrotechnic separation unlocking process in the specific embodiment of the present invention.

[0049] Figure 7 This is a schematic diagram of the influence of different prestresses on pyrotechnic shock in the specific embodiment of the present invention. Specific Embodiment:

[0050] The present invention will be further described below with reference to the accompanying drawings.

[0051] The method for simulating the unlocking of a pyrotechnic separation device and analyzing the influence of prestress based on finite element analysis according to the present invention, wherein the pyrotechnic separation device includes a structural plate 1, a stud 2, a housing 3, a cylinder 4, a locking flap 5, a piston 6 and an explosive. Its working mechanism is that before separation, they are tightly fitted together by applying a pre-tightening force to the stud to ensure its reliable connection. When receiving the separation instruction, the explosive inside the pyrotechnic separation device ignites and detonates, instantaneously reacting to high-temperature and high-pressure detonation gas, which rapidly flows upward along the internal channel and generates a strong air pressure impact on the lower part of the piston. As the gas fills the entire internal cavity of the housing, the product gas is fully mixed and begins to push the cylinder downward. When the cylinder descends to a certain position, its radial constraint on the locking flap is released, and at this time, the separation is completed. The specific steps are as follows:

[0052] Step S1: Establish a finite element model of the pyrotechnic separation device according to the actual situation of pyrotechnic impact;

[0053] Step S2: Establish a relevant prestress analysis model and solve the prestress solutions of each element;

[0054] Step S3: Import the prestress results into the pyrotechnic separation finite element model to realize the simulation of the separation unlocking process and the analysis of the influence of prestress.

[0055] Among them, step S1 specifically includes:

[0056] Step S11: Use SolidWorks to establish a three-dimensional model of the pyrotechnic separation device as shown in the appendix, and then import the model into HyperMesh software for mesh division. To save calculation time, the model is simplified to a quarter model (see appendix Figure 2 ); Figure 3 )

[0057] Perform fluid-structure interaction settings on the above three-dimensional model. Considering the response of the structure under transient large deformation conditions under the action of explosion shock waves, the present invention adopts the structured ALE (S-ALE) algorithm in LS-DYNA. The algorithm defines the flow field action area through three-dimensional coordinates and directly generates structured three-dimensional meshes, thus avoiding the process of reading mesh element and node information, significantly accelerating the calculation speed and reducing memory occupancy. At the same time, the structured meshes make the connection relationship between elements and nodes simple and clear, simplifying the search algorithm during ALE coupling.

[0058] Step S12: Define the constitutive and state equations of each component and air in the pyrotechnic separation device. In view of the fact that the present invention mainly analyzes the unlocking process and the influence of prestress of the pyrotechnic separation device, the present invention adopts the *MAT_ELASTIC linear elastic constitutive equation instead of the Johnson-Cook constitutive equation commonly used for explosion shock. See appendix Figure 2 . For components with relatively linear motion trajectories, rigid body constraints are applied to further simplify the model. Among them, the structural plate uses Al6061 and adopts the *MAT_ELASTIC constitutive; other components are made of 30CrMnSiNi2 high-strength manganese steel. Among them, the studs and locking petals adopt the *MAT_ELASTIC constitutive, while the cylinder, piston and shell adopt the *MAT_RIGID constitutive.

[0059] In addition, the constitutive and state equations of explosives and air also need to be defined. The explosive uses PETN. To simulate its explosion process, the *HIGH_EXPLOSIVE_BURN constitutive model is selected and the three-term JWL state equation is adopted. The model expression is as follows:

[0060] p = Fp eos (V,E)

[0061] where F is the combustion coefficient, p eos is the pressure of the equation of state, V is the relative volume, and E is the internal energy density per unit initial volume.

[0062] When the explosive starts to detonate, the combustion time of each element can be calculated by dividing the distance from the detonation point to the element center by the detonation velocity D of the explosive. If multiple detonation points are defined, the closest detonation point will be determined. The combustion coefficient is taken as the maximum value:

[0063] F = max(F1, F2)

[0064] The JWL equation of state is as follows:

[0065]

[0066] where A, B, R1, R2, ω are undetermined parameters, and their values are calibrated by cylinder detonation tests.

[0067] Air is regarded as an ideal gas. The constitutive equation adopts *MAT_NULL, and the equation of state adopts *EOS_LINEAR_POLYNOMIAL. The expression of the equation of state is as follows:

[0068] p = C0 + C1μ + C2μ 2 + C3μ 3 +(C4 + C5μ + C6μ 2 )E

[0069]

[0070] where C0, C1, C2, C3, C4, C5, C6 are the coefficients of the linear equation of state, and ρ, ρ0 are the current density and reference density, respectively.

[0071] Finally, the explosive and air are automatically generated through the two keywords *ALE_STRUCTURED_MULTI-MATERIAL_GROUP and *ALE_STRUCTURED_MESH_VOLUME_FILLING in the S-ALE method.

[0072] Step S13: Set the boundary conditions of the pyrotechnic separation finite element model. The *BOUNDARY_SPC_SET is used to apply symmetric constraints to the solid domain, and the NONREFL (non-reflective boundary condition) and SYM (symmetric constraint) in *BOUNDARY_SALE_MESH_FACE are used to set the fluid domain boundary. At the same time, the INITIAL_DETONATION keyword is used to control the explosive detonation time.

[0073] Step S14: Perform fluid-structure interaction (FSI) settings on the finite element model. The structured mesh generated by the keywords *ALE_STRUCTURED_MESH and *ALE_STRUCTURED_MESH_CONTROL_POINTS directly calls the S-ALE solver during the solution process, without occupying additional memory, thus significantly saving computational time. Finally, the *ALE_STRUCTURED_FSI keyword is used to implement fluid-structure interaction. The fluid-structure interaction adopts the penalty function method, which automatically controls the number of coupling points, leakage control, normal type, edge coupling, and erosion coupling, without the need for users to set them in advance. In this keyword card, users need to input three important parameters, namely MCOUP (coupling material), PFAC (penalty factor), and FRIC (friction coefficient), to control the fluid-structure interaction.

[0074] Step S15: Set the surface-to-surface contact of the finite element model through *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE. At the same time, set the calculation time, time step, output, and energy of the finite element model. Finally, start the MPP (distributed computing) solver of the S-ALE algorithm through the *CONTROL_MPP_DECOMPOSITION_DISTRIBUTE_ALE_ELEMENTS keyword card.

[0075] Through the above steps, the establishment of the unlocking model of the pyrotechnic separation device is achieved.

[0076] Preferably, step S2 includes:

[0077] Step S21: Establish the prestress calculation model as shown in the appendix, calculate the prestress of each element, and import it into the subsequent finite element analysis model as the initial condition. In engineering, the preload is generally applied by applying a certain torque to the stud in the separation bolt. The relationship between the torque applied to the stud of the separation bolt and the prestress generated by the stud cross-section is as follows: Figure 4 In the formula, σ is the prestress of the stud cross-section, T is the torque applied to the stud, K is the torque coefficient, taking 0.2, and d is the stud diameter. In actual engineering, when this separation bolt is used for the star-rocket connection, the torque is 65 Mpa, and the diameter of the stud cross-section is 1.2 cm. Therefore, the prestress value generated in the stud structure can be calculated from the above formula to be approximately 240 MPa;

[0078]

[0079]

[0080] ​Step S22: Implement the prestress loading through the three keyword cards of *DATABASE_CROSS_SECTION_PLANE, *INITIAL_STRESS_SECTION, and *DEFINE_CURVE.

[0081] Step S23: Set the corresponding calculation time, time step, output, energy, and hourglass control, and set the implicit solver through *CONTROL_IMPLICIT_AUTO, *CONTROL_IMPLICIT_GENERAL, and *CONTROL_IMPLICIT_SOLUTION;

[0082] Step S24: Finally, implement the conversion of the implicit result to the explicit result by setting the *INTERFACE_SPRINGBACK_LSDYNA keyword;

[0083] Through the above steps, the establishment of the prestress model is achieved. The prestress applied by this method has the advantage of being more accurate compared to directly applying prestress in a single model.

[0084] Preferably, step S3 includes:

[0085] Step S31: Import the prestress result into the pyrotechnic separation finite element model. In the pyrotechnic separation finite element model, import the simulation analysis result file 'dynain' of the prestress in step S2, and delete the duplicate elements generated during the import. In this way, the relevant data of the prestress is obtained in the two keywords of *INITIAL_STRAIN_SOLID and *INITIAL_STRESS_SOLID of the model to be solved, and its axial stress nephogram is as shown in the appendix Figure 5 as follows.

[0086] Step S32: Open LS-run and perform finite element analysis. Select the appropriate number of NCPUs and MEMORY, and select lsdyna_mpp_dp_impi.exe as the solver, that is, the double-precision MPP (distributed computing) solver. The separation and unlocking process obtained by the simulation and the influence of the prestress are as shown in the appendix Figure 6 and 7 as follows.

[0087] The unlocking simulation and prestress influence analysis method of the pyro - separation device based on finite element analysis. By adopting the structured ALE (S - ALE) fluid - structure coupling algorithm, a structured three - dimensional mesh is directly generated, avoiding the complex processing flow of traditional unstructured meshes, significantly shortening the modeling time and reducing the memory occupation. At the same time, the node connection relationship of the structured mesh is clear, simplifying the fluid - structure coupling search algorithm and improving the simulation accuracy of the propagation of explosion shock waves. By independently establishing a prestress analysis model, accurately calculating the stud pre - tightening force and importing it as an initial condition into the dynamic unlocking simulation, the problem of error accumulation caused by directly loading prestress in traditional methods is solved. Combining the torque - prestress relationship formula ensures the engineering accuracy of prestress loading, making the simulation results closer to the actual satellite - rocket separation working conditions. Using the S - ALE method combined with the MPP (distributed computing) solver, the solution efficiency is greatly improved through parallel computing, which is suitable for high - fidelity simulation of explosion shock transient responses. The fluid - structure coupling automatically controls the number of coupling points and leakage through penalty functions, reducing manual intervention and supporting the simulation of the dynamic mixing process of multi - material explosion products. Different constitutive models (such as elastic constitutive, rigid body constitutive, detonation combustion constitutive) are selected according to the characteristics of different components, and the JWL equation of state is used to accurately describe the explosive detonation process, combined with the linear polynomial equation of state to simulate the aerodynamic behavior, significantly improving the reliability of the analysis of explosion shock wave propagation and structural response. Through quarter - model simplification, symmetric boundary condition setting and implicit - explicit result conversion technology (*INTERFACE_SPRINGBACK_LSDYNA), while ensuring the calculation accuracy, the model complexity is reduced, providing an efficient and reliable simulation tool for the design optimization and shock environment prediction of pyro - separation devices in aerospace engineering.

[0088] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A method for simulating the unlocking of an explosive separation device and analyzing the influence of prestress based on finite element analysis. The explosive separation device includes a structural plate, a stud, a housing, a cylinder, a locking flap, a piston, and an explosive, and is characterized in that: The specific steps are as follows: Step S1: Establish a finite element model of the pyrotechnic separation device according to the actual situation of the pyrotechnic impact; Step S2: Establish a relevant prestress analysis model and solve the prestress solutions of each element; Step S3: Import the prestress results into the pyrotechnic separation finite element model to simulate the separation and unlocking process and analyze the influence of prestress.

2. The method for unlocking simulation and prestress influence analysis of the pyrotechnic separation device based on finite element analysis according to claim 1, wherein: The specific content of step S1 includes: Step S11: Use SolidWorks to establish a three-dimensional model of the pyrotechnic separation device, simplify the three-dimensional model into a quarter model, and then import the quarter model into HyperMesh software for mesh generation. The structured ALE (S-ALE) algorithm in LS-DYNA is used. The algorithm defines the flow field action area through three-dimensional coordinates and directly generates structured three-dimensional meshes; Step S12: Define the constitutive and state equations of each component and air in the pyrotechnic separation device. The structural plate, stud, housing, cylinder, locking flap, and piston adopt the *MAT_ELASTIC linear elastic constitutive equation. The structural plate adopts the *MAT_ELASTIC constitutive equation, the stud and locking flap adopt the *MAT_ELASTIC constitutive equation, and the cylinder, piston, and housing adopt the *MAT_RIGID constitutive equation; The explosive is selected with the *HIGH_EXPLOSIVE_BURN constitutive equation and adopts the three-term JWL state equation. The model expression is as follows: p = Fp eos (V, E) where F is the combustion coefficient, p eos is the pressure of the equation of state, V is the relative volume, and E is the internal energy density per unit initial volume; Air adopts the *MAT_NUL constitutive equation, and the state equation adopts *EOS_LINEAR_POLYNOMIAL. The state equation expression is as follows: p = C0 + C1μ + C2μ 2 + C3μ 3 +(C4 + C5μ + C6μ 2 )E In the formula, C0, C1, C2, C3, C4, C5, C6 are the coefficients of the linear state equation, and ρ and ρ0 are the current density and reference density respectively; Finally, the explosive and air are automatically generated through the two keywords *ALE_STRUCTURED_MULTI-MATERIAL_GROUP and *ALE_STRUCTURED_MESH_VOLUME_FILLING in the S-ALE method; Step S13: Set the boundary conditions of the pyrotechnic separation finite element model. Apply symmetric constraints to the solid domain using *BOUNDARY_SPC_SET, set the fluid domain boundary using NONREFL and SYM in *BOUNDARY_SALE_MESH_FACE, and control the explosive explosion time through the INITIAL_DETONATION keyword. Step S14: Perform fluid-structure interaction (FSI) settings on the finite element model. The structured mesh generated by the keywords *ALE_STRUCTURED_MESH and *ALE_STRUCTURED_MESH_CONTROL_POINTS directly calls the S-ALE solver during the solution process. Finally, use the *ALE_STRUCTURED_FSI keyword to achieve fluid-structure interaction. The fluid-structure interaction adopts the penalty function method to automatically control the number of coupling points, leakage control, normal type, edge coupling, and erosion coupling. In this keyword card, the user needs to input three important parameters, namely coupling material, penalty factor, and friction coefficient, to control the fluid-structure interaction; Step S15: Set the surface-to-surface contact of the finite element model through *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE. At the same time, set the calculation time, time step, output, and energy of the finite element model. Finally, start the MPP (distributed computing) solver of the S-ALE algorithm through the *CONTROL_MPP_DECOMPOSITION_DISTRIBUTE_ALE_ELEMENTS keyword card.

3. The unlocking simulation of the pyroseparation device based on finite element analysis and the analysis method of the influence of prestress according to claim 2, characterized in that: The specific steps of step S2 include: Step S21: Establish a prestress calculation model, calculate the prestress of each element and import it into the subsequent finite element analysis model as the initial condition. Apply a certain torque to the stud in the split bolt to achieve preload. The relationship between the torque applied to the stud of the split bolt and the prestress generated by the stud cross-section is as follows: In the formula, σ is the prestress of the stud cross-section, T is the torque applied to the stud, K is the torque coefficient, taking 0.2, and d is the stud diameter; Step S22: Use the three keyword cards *DATABASE_CROSS_SECTION_PLANE, *INITIAL_STRESS_SECTION, and *DEFINE_CURVE to achieve the loading of prestress; Step S23: Set the corresponding calculation time, time step, output, energy, and hourglass control, and set the implicit solver through *CONTROL_IMPLICIT_AUTO, *CONTROL_IMPLICIT_GENERAL, and *CONTROL_IMPLICIT_SOLUTION; Step S24: Finally, achieve the conversion of implicit results to explicit results by setting the *INTERFACE_SPRINGBACK_LSDYNA keyword.

4. The unlocking simulation and prestress influence analysis method of the pyro separation device based on finite element analysis according to claim 3, characterized in that: The specific steps of step S3 include: Step S31: Import the prestress results into the pyrotechnic separation finite element model. In the pyrotechnic separation finite element model, import the simulation analysis result file 'dynain' of the prestress in step S2 and delete the duplicate elements generated during the import. In this way, the relevant data of the prestress is obtained in the two keywords *INITIAL_STRAIN_SOLID and *INITIAL_STRESS_SOLID of the model to be solved; Step S32: Open LS-run and perform finite element analysis. Select the appropriate number of NCPUs and MEMORY, and select lsdyna_mpp_dp_impi.exe, which is a double-precision MPP solver, to achieve parallel computing by allocating independent CPU memory.

5. The method for unlocking simulation and prestress influence analysis of the pyrotechnic separation device based on finite element analysis according to claim 4, wherein: In step S12, when the explosive starts to detonate, the combustion time of each cell is calculated by dividing the distance from the detonation point to the cell center by the detonation velocity D of the explosive. If many detonation points are defined, the closest detonation point will be determined, and the combustion coefficient is taken as the maximum value: F = max(F1, F2) The JWL equation of state is as follows: In the formula, A, B, R1, R2, and ω are undetermined parameters, and their parameters are calibrated by cylinder detonation tests.

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