Design method of tension system for solid rocket engine composite case with propellant winding forming

Abstract

This scheme discloses a method for designing the tension regime of propellant winding molding for solid rocket motor composite shells, including: inputting the winding parameters of the engine composite shell; establishing a propellant winding model of the engine composite shell based on the input shell winding parameters; obtaining the theoretical initial stress regime through inverse solving using an iterative algorithm and converting it into the tension regime of each layer; performing simulation calculations to obtain the residual stress field after propellant winding of the shell, and verifying whether the safety factor of the propellant grain meets the design requirements; establishing a propellant curing calculation model, performing simulation calculations based on the residual stress field after propellant winding of the shell, and superimposing the thermo-chemical stress generated during the curing process to obtain the final manufacturing residual stress field of the shell; establishing a composite shell internal pressure strength calculation model, performing simulation calculations based on the final manufacturing residual stress field of the shell, and verifying whether the internal pressure strength of the shell meets the design requirements; if it meets the requirements, outputting the tension regime; otherwise, redesigning the tension regime.

Description

Technical Field

[0001] This solution relates to the field of solid rocket motor design optimization, specifically to a design method for the tension regime of propellant winding molding of a solid rocket motor composite shell. Background Technology

[0002] Composite material winding technology is widely used in aerospace, automotive, and shipbuilding industries. This technology can manufacture lightweight, high-strength structural components, greatly improving energy efficiency and structural performance. In the aerospace field, composite materials are widely used in modern cutting-edge equipment, such as solid rockets. The composite material wound shell, as a key component of solid rocket engines, serves as both the propellant tank and the combustion site, and its mechanical properties directly determine the performance of the solid rocket engine.

[0003] Existing solid rocket motor manufacturing technologies involve separate steps for propellant loading and shell winding. Free loading introduces gaps, reducing the propellant loading coefficient; while wall-mounted casting is prone to stress, leading to interface debonding. Integrated winding molding, with fibers directly wound onto the outer surface of the solid propellant charge, ensures seamless contact between the combustion chamber shell, insulation layer, and propellant, achieving zero-gap loading. This improves the propellant loading coefficient while reducing the risk of interface debonding.

[0004] However, existing technologies have several limitations that make it difficult to design the fiber winding tension regime during the drug-loaded winding process. These limitations mainly include three aspects: First, using the drug cartridge as a mandrel, due to its unique mechanical properties, the inner fibers experience stress relaxation and even wrinkling during winding, resulting in an inner fiber structure that deviates significantly from the predicted results. Second, the drug cartridge is prone to deformation and failure under the influence of the fibers during winding. Third, the composite material undergoes complex physicochemical changes during curing, generating residual stress that affects the shell's pressure-bearing performance. Summary of the Invention

[0005] The purpose of this solution is to provide a method for designing the tension regime of propellant winding in the composite shell of a solid rocket motor, in order to solve the problem of designing the fiber winding tension regime in the existing propellant winding process.

[0006] To achieve the above objectives, this solution adopts the following technical approach: A method for designing tension regimes for propellant winding molding of composite shells for solid rocket motors, including: Input the winding parameters for the engine composite material housing; Based on the input shell winding parameters, a propellant winding model for engine composite shell is established to describe the stress transfer from the fiber layer to the propellant mandrel and the interlayer stress superposition effect during the winding process. Using the target residual stress as the objective, the shell-loaded winding model is used as a forward calculator. An iterative algorithm is used to solve the initial winding tension values ​​of each layer that satisfy the target residual stress, thereby obtaining the theoretical initial stress regime and converting it into the tension regime of each layer. Simulation calculations are performed based on the obtained tension regime to obtain the residual stress field after the shell is wrapped with the explosive, and to check whether the safety factor of the explosive charge meets the design requirements. If it does, proceed to the next step; if it does not, adjust the target residual stress and iterate the solution of the tension regime again. A calculation model for curing with medicated material was established. The residual stress field after the shell was wrapped with medicated material was simulated and calculated. The thermo-chemical stress generated during the curing process was superimposed to obtain the final manufacturing residual stress field of the shell. Establish a calculation model for the internal pressure strength of the composite material shell, perform simulation calculations based on the final manufacturing residual stress field of the shell, and check whether the internal pressure strength of the shell meets the design requirements; if it does, output the tension regime; otherwise, redesign the tension regime.

[0007] Furthermore, the construction process of the propellant-wrapped model of the engine composite housing is as follows: The winding mandrel is made of isotropic material, and its radial displacement field can be obtained based on the thick-walled cylinder theory. With radial stress field The analytical expression for the circumferential strain can be derived by analyzing the radial and circumferential deformations of the infinitesimal element. Radial strain expression ; For the expression of circumferential strain Differentiation yields the strain compatibility equation; by setting the boundary conditions for the composite fiber-wound shell and considering the core mold as a thick-walled cylindrical structure subjected only to equivalent external pressure, the circumferential stress is obtained. With radial stress Analytical expression; Solve for the inner diameter. The displacement field at the point is determined, and then, under the assumption of small deformation, the differential equations of radial stress and circumferential stress with respect to radial displacement are obtained, thus yielding the utilization coefficient. Radial displacement of the composite fiber winding layer characterized A general solution formula is used to determine the radial and circumferential stresses of the fiber winding layer, and the formula is expressed using multiple material property coefficients. Define the winding tension as the winding radius as The tension per unit bandwidth of the winding layer when winding is complete is defined as the winding radius. The circumferential winding tension component of the composite material winding layer is Based on the circumferential winding tension component The winding radius is obtained as Circumferential stress of the winding layer ; Determine the radius as The winding layer, with its radial back pressure generated by the circumferential winding tension component, introduces equilibrium conditions at the interface, thereby affecting the coefficient. Solve to determine the radial displacement. Then we obtain the radius as the winding radius as The radial and circumferential stresses of the winding layer; With the first Analysis of the fiber winding layer determined that it exists in the middle layer. The remaining circumferential stress and remaining circumferential tension on the layer are then converted into remaining stress.

[0008] Furthermore, the expression for the residual stress is as follows: ; in For the first The circumferential stress of the winding layer, where h is the thickness of a single layer of the winding layer. To simplify the calculation settings, ; For the radial stiffness of the propellant core mold, The outer diameter of the drug cartridge core mold. The outer diameter after winding is complete. External radial pressure, , , , The material property coefficients are as follows: , , , ; in, Poisson's ratio represents the circumferential strain caused by radial stress. Poisson's ratio for radial strain caused by circumferential stress; , , These are the elastic moduli of the fiber winding layer in the circumferential and radial directions, respectively. For the first The radius of the winding layer, where M is the total number of winding layers. Let m be the inner diameter of the m-th winding layer. for Circumferential stress at the location.

[0009] Furthermore, the initial winding tension values ​​of each layer that satisfy the target residual stress are solved in reverse using an iterative algorithm, including: In the initial calculation, the initial prestress of each layer is set to be equal to the target value; No. kIn the second iteration, the residual stress is recursively updated based on the deviation between the previously calculated residual stress and the target value. Initial stress estimate of the layer The updated initial stress estimate Substituting the shell-borne explosive winding model again, the remaining winding stress was calculated. With initial prestress and The difference and error threshold are used to determine convergence. The iteration terminates when the condition is met. This is the desired theoretical initial stress regime, which is then converted into the tension regime of each layer.

[0010] Furthermore, according to The tension system of each layer is obtained through conversion. ;in The thickness of a single layer of fiber winding is given. For the first Layer fiber winding angle, For the first N Layer process tension.

[0011] Furthermore, a refined model of single-fiber layer winding was constructed using the tensile profile method, and the winding and forming process of the propellant mid-section fiber with propellant grain structure was simulated. Construct a numerical simulation boundary condition and constraint system for the circumferential and longitudinal winding process; convert it into equivalent circumferential stress or radial pressure load according to the step tension regime; apply these loads step by step in the finite element simulation model to simulate the layer-by-layer accumulation and distribution of stress during the winding process; The equivalent temperature field distribution of each fiber layer is determined by layer-by-layer inversion using a trial-and-error method, so that the combined stress field formed by the temperature field and the winding tension has an equivalent mechanical response. Run a simulation of the winding process to obtain the stress state after all winding layers have been applied and reached equilibrium; output the residual stress field of the shell after the drug is wound. The stress field of the propellant core mold is extracted from the residual stress field after the propellant is wrapped in the shell. The safety factor is calculated based on the yield strength or allowable strain criterion of the propellant material. The safety factor is checked to see if it meets the design requirements. If it does, the residual stress field after the propellant is wrapped in the shell is output. If it does not, the target residual stress is adjusted and the tension regime is iteratively solved again.

[0012] Furthermore, using the residual stress field after the shell is wrapped with the drug as the initial stress field, a drug-coated curing calculation model is loaded, and a thermo-mechanical-chemical coupled finite element analysis is performed; temperature field boundary conditions are set, i.e. curing regime; and the residual stress field after the shell is cured with the drug is calculated.

[0013] Furthermore, a calculation model for the internal compressive strength of the composite material shell is established, including: A refined finite element model of the shell, including fiber trajectories, is established, comprising four factors: layup sequence, fiber trajectory, tensile stress field, and curing residual stress field; individual winding layers are sequentially established based on winding process parameters. Calculate the interlayer connection path and, based on the winding direction conversion characteristics, classify the interlayer connection structure into two typical working conditions: longitudinal-circular transition structure and circumferential-longitudinal transition structure; A finite element calculation model for the internal compressive strength of the composite shell was established; the residual stress fields after the shell was wrapped with the drug and after the shell was cured with the drug were added to the initial analysis state in the form of predefined fields, and the results of the internal compressive stress-strain field of the shell were calculated. A design internal pressure load is applied to the inner surface of the shell model, and a static analysis is performed to calculate the total stress field of the shell under the combined action of internal pressure and residual stress. Based on the total stress field, check the internal pressure strength of the shell; if it meets the design requirements, output the tension regime.

[0014] A terminal device includes a processor, a memory, and a computer program stored in the memory; when the processor executes the computer program, it implements the design method for the tension regime of the propellant winding molding of the solid rocket motor composite shell.

[0015] A computer-readable storage medium storing a computer program; when executed by a processor, the computer program implements the design method for the tension regime of the propellant winding molding of the solid rocket motor composite shell.

[0016] Compared with existing technologies, this solution has the following technical features: This scheme comprehensively considers multiple aspects such as the winding process, curing process, and pressure bearing performance of composite material shells with medicated winding, and can output a perfect and reliable tension regime; this design method is also applicable to the design of tension regimes for composite material winding molding of other viscoelastic mandrels. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall process of the design method for this solution; Figure 2 This is the cross-section of a composite fiber winding model; Figure 3 Flowchart of the iterative search process; Figure 4 The diagrams show the geometric model and the finite element model; where (a) is the geometric model and (b) is the finite element model. Figure 5The simulation results of residual stress in constant tension winding are shown below; (a) is the residual stress distribution cloud map, (b) is the isometric view of the stress distribution in the propellant core mold, (c) is the front view of the stress distribution in the propellant core mold, (d) is the stress distribution in the composite fiber winding layer, and (e) is the stress distribution in the composite fiber winding layer. Figure 6 The finite element simulation model of the winding process is shown in (a), where (b) is the finite element model and (a) is the mesh generation diagram. Figure 7 This is a schematic diagram of the boundary conditions and constraint system for the tension winding process; where (a) represents the circumferential winding boundary conditions and constraints, and (b) represents the longitudinal winding boundary conditions and constraints. Figure 8 The stress and strain field distribution of the longitudinally wound propellant and fiber is shown; where (a) is the stress cloud map of the fiber band, (b) is the stress cloud map of the propellant, (c) is the strain cloud map of the fiber band, and (d) is the strain cloud map of the propellant. Figure 9 This is a schematic diagram of the solidification simulation calculation process; Figure 10 The diagrams show the stress-strain contours of the fiber layer in the composite material; where (a) is the overall residual stress diagram of the fiber layer in the composite material, and (b) is the residual strain contour diagram of the fiber layer in the composite material. Figure 11 The model consists of a single winding layer; where (a) is the first longitudinal winding, (b) is the first circumferential winding, (c) is the second longitudinal winding, and (d) is the second and third circumferential windings. Figure 12 The model is a layer-to-layer winding structure; where (a) is a longitudinal-to-circular transition and (b) is a circumferential-to-longitudinal transition. Figure 13 To simulate and calculate a 1 / 16 scale solid model; Figure 14 The loads and boundary conditions for the finite element model of the composite shell are: (a) is the uniformly distributed water pressure, (b) is the fixed constraint of the polar hole, (c) is the cyclic symmetric constraint, and (d) is the symmetric constraint. Figure 15 The diagram shows the stress distribution contours; (a) is an isometric view and (b) is a sectional view. Detailed Implementation

[0018] To address the challenge of designing tension regimes for propellant winding molding of composite material shells, this solution provides a method for designing tension regimes for propellant winding molding of solid rocket motor composite shells, comprising the following steps: Step 1: Input the winding parameters of the engine composite material shell to provide basic data for all subsequent modeling and calculations.

[0019] The shell winding parameters include the total number of fiber winding layers. n, angle of fiber winding in each layer α Fiber material parameters (elastic modulus) E f Poisson's ratio ν f The single-layer thickness of the fiber winding layer t f etc.), parameters of the mandrel material (elastic modulus of the mandrel material), etc. E c Poisson's ratio ν c , inner diameter a , outer diameter b ).

[0020] Step 2: Based on the input shell winding parameters, establish a propellant winding model for the engine composite shell. This model describes the stress transfer from the fiber layer to the propellant core mold and the interlayer stress superposition effect during the winding process, thus providing the core calculation basis for the tension iteration solution in Step 3.

[0021] The construction process of the engine composite material casing explosive-wound model is as follows: For the composite structure consisting of a propellant core mold and a multilayer composite winding layer (see cross-sectional form) Figure 2 A theoretical analytical model was established; to improve computational efficiency and ensure accuracy, the model parameters and boundary conditions were specified as follows: the subscript is " "and" "" represents physical quantities along the radial and circumferential directions, respectively; the subscript is " "and" "These are the physical quantities corresponding to the composite fiber and the propellant core mold, respectively." Based on the mechanical properties of composite structures and the characteristics of winding processes, the following core assumptions are set: Ideal interlayer contact assumption: The interlayer interfaces of the composite material winding are completely bonded, without gaps or delamination defects; Frictionless constraint assumption: Frictional effects are ignored at the interlayer contact surfaces, but relative slippage between the winding layers is guaranteed; Simplified load condition assumptions: The inner cylinder and the winding layer are only subjected to equivalent uniform external pressure; body forces, axial stress and strain, and residual stress caused by temperature gradients are ignored; Linear elastic response assumption: During the winding process, all materials are in the linear elastic deformation stage, with no plastic or nonlinear behavior; Geometric symmetry assumptions: The inner cylinder is a strictly cylindrical structure; the outer winding satisfies the axisymmetric condition and the circumferential physical quantities are uniformly distributed.

[0022] Table 1. Symbol Conventions for Theoretical Analysis of Tension System

[0023] When using a weak stiffness propellant charge as a core mold structure, its mechanical behavior under the combined action of internal and external pressure must be strictly limited to the elastic deformation range; if the elastic limit is exceeded, the propellant charge will yield or become unstable, leading to structural failure and failing to meet the engineering design requirements.

[0024] By coupling geometric equations, linear elastic constitutive relations, and static equilibrium equations, a set of governing equations describing the evolution of the stress field can be established. Specifically, the geometric equations characterize the differential relationship between strain and displacement, the constitutive equations reflect the elastic response characteristics of the material, and the equilibrium equations reveal the mechanical equilibrium conditions between the radial stress gradient and the circumferential stress. Solving this set of equations simultaneously yields the radial stress. With circumferential stress The parsing expression. The winding mandrel is made of isotropic material, and its radial displacement field can be obtained based on the thick-walled cylinder theory. With radial stress field The parsing expression: ; In the formula: These are the general solution coefficients for displacement; The winding radius is in meters. The Poisson's ratio of the core sample. The elastic modulus of the propellant core mold. is the Poisson's ratio of the propellant core mold.

[0025] By analyzing the radial and circumferential deformation of the infinitesimal element, the expressions for the strain components can be derived: ; ; Where u represents radial displacement, du represents the differential of radial displacement, dr is the differential of radial coordinate, and dθ is the differential of circumferential angle.

[0026] For the expression of circumferential strain Differentiating, we obtain the strain compatibility equation: ; In the formula: The radial strain of the propellant core mold. For the circumferential strain of the propellant core mold; The value is the winding radius in meters (m).

[0027] Assume the boundary conditions for the composite fiber-wound shell are as follows: when hour, ; when hour, ; In the formula: The inner diameter of the propellant core mold; This is the outer diameter after winding is completed; , The mandrel has a winding radius of 100 mm. and Radial stress at the location / N , This is the radial stress.

[0028] The propellant core mold can be considered as a thick-walled cylindrical structure that only bears the equivalent external pressure, and its circumferential stress With radial stress The analytical expression is: ; ; In the formula: ; These are the inner and outer diameters (in meters) of the propellant core mold, respectively. To act on the outer surface of the propellant core mold The equivalent external pressure at the location, The value is the winding radius in meters (m).

[0029] Solve for the inner diameter. Displacement field at : ; in, The Poisson's ratio of the propellant core mold. This is the elastic modulus of the propellant core mold.

[0030] Under the assumption of small deformation, the differential equations of radial stress and circumferential stress versus radial displacement are obtained: ; in For radial displacement, , for The first and second differentials, The anisotropic parameters of the winding layer are given.

[0031] The radial displacement of the composite fiber winding layer was obtained. General solution formula: ; In the formula: For coefficients, , , These are the elastic moduli of the fiber winding layer in the circumferential and radial directions, respectively.

[0032] get: ; ; In the formula: , The radial and circumferential stresses of the fiber winding layer, , , , The material property coefficients are as follows: , , , .

[0033] in, Poisson's ratio represents the circumferential strain caused by radial stress. Poisson's ratio for radial strain caused by circumferential stress; Define winding tension The winding radius is The tension per unit bandwidth of the winding layer when winding is complete, in units of ,Right now: ; In the formula: To apply the winding force in the fiber direction / N ; The width of the prepreg fiber for composite materials is 1000 m.

[0034] Define the winding radius as The circumferential winding tension component of the composite material winding layer is : ; In the formula: The fiber winding angle is the angle between the fiber direction and the axial direction, expressed in rad. This value can be used to convert winding tension at different angles into circumferential winding tension.

[0035] Based on the circumferential winding tension component The winding radius is obtained as Circumferential stress of the winding layer : ; In the formula: The thickness of a single layer of the winding is expressed in meters (m).

[0036] radius is The winding layer, from the circumferential winding tension component The resulting radial back pressure for: ; Substituting the equilibrium condition at the boundary, we get: ; ; In the formula: Radial stiffness of the propellant core mold / N·m -1 It is only related to the inner and outer diameters of the propellant core mold and the material parameters; The outer diameter of the propellant core mold is in meters (m). The outer diameter after winding is complete. This refers to the external radial pressure.

[0037] For coefficients and Solving for the problem, we get: ; ; In the formula: To simplify the calculation settings, .

[0038] The radius obtained is the winding radius. The radial and circumferential stresses of the winding layer are: ; ; in, The outer diameter of the first layer of winding.

[0039] With the first Analysis of the fiber winding layer revealed that it exists in the middle layer. layer Residual circumferential stress on for: ; In the formula: For the first Circumferential stress of the layer winding, The winding radius The circumferential winding tension component of the winding layer, They represent the first Layer winding layer to the first The influence of circumferential stress on the winding layers, where M is the total number of winding layers and h is the thickness of a single winding layer. This represents the effect of the m-th winding layer on the circumferential stress of the k-th winding layer.

[0040] Obtain the middle one layer Residual circumferential tension on : ; In the formula: For the first layer inner winding layer The resulting equivalent external pressure / N, Let m be the inner diameter of the m-th winding layer.

[0041] The formula Convert to residual stress expression: ; By inversely solving the initial tension gradient with equal residual stress as the optimization objective, the residual stress distribution of each layer after winding can be obtained based on any given initial winding tension, thus laying the foundation for inversely solving the tension regime.

[0042] Step 3: Solve the tension regime using an iterative search method.

[0043] This step takes the target residual stress as the objective. The shell-loaded winding model in step 2 is used as a forward calculator. The initial winding tension values ​​of each layer that meet the target residual stress are solved in reverse through an iterative algorithm. The theoretical initial stress regime is obtained and converted into the tension regime of each layer.

[0044] Based on the principle of numerical iteration, Matlab software is used to perform iterative search calculations of the stress distribution in the winding layer. The calculation process is as follows: Figure 3 As shown in Table 2, for ease of calculation, the parameter definitions are as follows: Table 2. Definition of Parameters for Iterative Search Calculation of Stress Distribution in Wrapped Layer

[0045] Step 3-1, Initialization.

[0046] In the initial calculation, the initial prestress of each layer is set to be equal to the target value: ; Substituting the above equation into the theoretical model in step 2, the residual stress of the first iteration is calculated. .

[0047] Step 3-2, iterative correction.

[0048] No. k The next iteration ( When the target value is calculated, the remaining stress is updated according to the recursive formula based on the deviation between the previously calculated remaining stress and the target value. Initial stress estimate of the layer : ; in, For the first k- The remaining winding stress of the i-th layer during the first iteration.

[0049] Updated initial stress estimate Substituting the theoretical model from step 2 back into the model, the remaining winding stress is calculated. .

[0050] Step 3-3, convergence judgment.

[0051] When the following conditions are met: ; (in ξ The iteration terminates when a minimum error threshold (e.g., 0.1 MPa) is preset, at which point the remaining winding stress in each layer meets the equal stress design requirements; at this point... This is the desired theoretical initial stress regime, based on... The tension system of each layer is obtained through conversion. ;in The thickness of a single layer of fiber winding is given. For the first Layer fiber winding angle, For the first N Layer process tension.

[0052] Step 4: Perform simulation calculations based on the tension regime obtained in Step 3 to obtain the residual stress field after the shell is wrapped with the explosive, and check whether the safety factor of the explosive charge meets the design requirements; if it does, proceed to Step 5; if it does not, return to Step 3 to adjust the target residual stress and then iterate and solve the tension regime again.

[0053] This step uses high-fidelity finite element simulation to accurately calculate the actual stress field after winding under the tension regime obtained in step 3, and verifies the structural safety of the propellant grain in this state for the first time.

[0054] A composite fiber winding model was established using the rotating profile method. For circumferential fiber structures with standard symmetry characteristics and circumferential tension load conditions, a 1 / 4-inch propellant core mold was used as the simulation object to improve computational efficiency (see model details). Figure 4 Based on the principle of tension superposition, the tension load of each layer of wound fibers is applied stepwise to obtain the residual stress field of each fiber layer after stress redistribution. Figure 5 The stress cloud diagram shown clearly demonstrates the gradient distribution characteristics of the residual stress in the winding layer along the wall thickness.

[0055] Step 4-1: Establish a finite element simulation model of the winding process.

[0056] A refined model of single-fiber layer winding was constructed using the tensile profile method, and the winding process of the propellant mid-section fiber in the propellant grain structure was simulated (see details of the geometric configuration). Figure 6 ).

[0057] For the propellant core mold assembly, motion coupling is established between the core mold and the central axis (Z-axis), and its X and Y degree of freedom is constrained to simulate the fixed state of the fixture. At the same time, the central axis is given rotational motion parameters around the Z-axis to realize the core mold's rotation function. The lateral feed motion of the fiber guiding device in the winding process is simulated by applying a translational velocity along the Z-axis. For the fiber tape assembly, the motion association between the initial end face of the fiber and the center of the propellant core is established by beam element connection. A concentrated load along the fiber axis is applied at the coupling reference point on the fiber end face to characterize the winding tension. At the same time, the Z-direction displacement of the fiber tape side is constrained to prevent spatial deflection and twisting phenomena that may occur during the process.

[0058] Step 4-2, the boundary conditions and constraint system for the numerical simulation of the circumferential and longitudinal winding processes are as follows: Figure 7 As shown. Based on the tension regime output in step 3, it is converted into equivalent circumferential stress or radial pressure load. These loads are applied step by step in the finite element simulation model to simulate the layer-by-layer accumulation and distribution of stress during the winding process.

[0059] Step 4-3: The equivalent temperature field distribution of each fiber layer is determined by layer-by-layer inversion using a trial-and-error algorithm, so that the combined stress field formed by the temperature field and the winding tension has an equivalent mechanical response.

[0060] Step 4-4: Run the winding process simulation to obtain the stress state after all winding layers have been applied and reached equilibrium; output the residual stress field of the shell after the drug is wound. σ wrapped This includes detailed stress and strain contour maps and data for the propellant grain and each fiber layer, such as... Figure 8 As shown.

[0061] Steps 4-5: Residual stress field after the drug is wrapped around the shell. σ wrapped The stress field of the propellant core mold is extracted, and its safety factor is calculated based on the yield strength or allowable strain criterion of the propellant material. The safety factor is then checked to ensure it meets design requirements. If it does, the residual stress field of the shell after propellant winding is output. σ wrapped Proceed to the next calculation. If the conditions are not met, return to step 3, adjust the target residual stress, and iterate the solution of the tension regime again.

[0062] Step 5: Establish a calculation model for the curing of the drug-coated shell, based on the residual stress field obtained in Step 4 after the shell is wrapped with the drug. σ wrapped Simulation calculations were performed to superimpose the thermo-chemical stresses generated during the curing process, thereby obtaining the final manufacturing residual stress field of the shell.

[0063] Step 5-1, the mathematical expression of the heat conduction equation is: ; in, This refers to the transient change in the internal energy of the material; This is the heat conduction term, describing the heat diffusion process; This is an exothermic term for chemical reactions, and is a nonlinear heat source unique to the curing process; Density of composite material / kg·m -3 This determines the thermal inertia of the material and affects the hysteresis effect of temperature changes; Specific heat capacity / J·(kg·K) -1 ; Thermal conductivity / W·(m·K) -1 The anisotropic properties of the thermal conductivity of materials (such as the thermal conductivity along the fiber direction being significantly higher than that in the perpendicular direction in fiber-reinforced composites) directly determine the heat diffusion rate. Enthalpy of reaction / kJ·mol -1 ; The curing reaction rate is given by T, where T is temperature and t is time. For vector differential operators, This refers to the degree of curing.

[0064] Using the third type of boundary condition (convective heat transfer): ; In the formula: h The convective heat transfer coefficient; The ambient temperature is represented in K, and in segmented temperature control processes, it can be set as a time-varying function to simulate the actual heating curve. n represents the normal direction.

[0065] The resin curing process is divided into two stages, and the curing reaction rate is expressed as:

[0066] in:

[0067] In the formula: The curing reaction rate constant is ; It is a natural constant. Pre-exponential factor / s -1 , Activation energy / kJ·mol -1 , is the ideal gas constant.

[0068] Step 5-2: Establish a composite material property evolution model.

[0069] resin modulus With degree of curing The changes can be divided into two phases: Before glue dots ( The resin did not form a continuous network, resulting in a low modulus.

[0070] ; After the gel point ( ): The resin crosslinks, and the modulus increases linearly with the degree of curing.

[0071] ; In the formula: This is the correlation coefficient for the degree of cure. The resin modulus before gelation is expressed in MPa. The modulus of fully cured resin in MPa. This refers to the degree of curing at the gel point.

[0072] Step 5-3: Establish the expansion strain model.

[0073] Thermal expansion strain :

[0074] In the formula: This is the coefficient of thermal expansion of the resin. This represents the resin volume fraction. This is a reference temperature.

[0075] The equivalent thermal expansion coefficient is approximately:

[0076] In the formula: It is the equivalent thermal expansion coefficient. This represents the fiber volume fraction. , The values ​​represent fiber modulus and resin modulus in MPa.

[0077] Chemical contraction strain: During resin crosslinking and curing, molecular chain rearrangement leads to volume shrinkage, and its strain rate is positively correlated with the curing rate. ; In the formula: For chemical shrinkage strain rate, Curing rate, The chemical shrinkage coefficient was determined by differential scanning calorimetry (DSC) and volume shrinkage experiments.

[0078] Step 5-4, Coupled expansion strain model.

[0079] Total expansion strain This can be represented as a linear superposition of thermal expansion and chemical contraction:

[0080] Initial conditions (t=0): t is time. It is the equivalent thermal expansion coefficient.

[0081] Temperature history: defined by the curing process regime.

[0082] The residual stress field of the shell after the drug is wrapped, as output in step 4-2 σ wrapped As the initial stress field, the above model was loaded, and a thermo-mechanical-chemical coupled finite element analysis was performed; temperature field boundary conditions, i.e., curing regime, were set; and the residual stress field after the shell with the drug-coated material was calculated. σ cured ,like Figure 10 As shown.

[0083] Step 6: Establish a calculation model for the internal pressure strength of the composite material shell. Perform simulation calculations based on the final manufacturing residual stress field of the shell obtained in Step 5 to check whether the internal pressure strength of the shell meets the design requirements. If it does, output the tension regime; otherwise, return to Step 3.

[0084] Step 6-1: Establish a refined finite element model of the shell including fiber trajectories, mainly including four factors: layup sequence, fiber trajectory, tensile stress field, and curing residual stress field; based on the winding process parameters, establish the sequence for each individual winding layer. The effect of each individual winding layer is obtained as follows: Figure 11 As shown. Step 6-2: Calculate the interlayer connection path. Based on the winding direction conversion characteristics, the interlayer connection structure is divided into two typical working conditions: longitudinal-circular (longitudinal-circular) transition structure and circumferential-longitudinal (circular-longitudinal) transition structure. Specific structures are as follows... Figure 12 As shown.

[0085] Step 6-3: Establish a finite element calculation model for the internal pressure strength of the composite material shell.

[0086] Leveraging the rotational symmetry of the shell structure and fully utilizing its axisymmetric geometry, a significant reduction in computational dimensionality is achieved by constructing a 1 / 16-period symmetric reduction model. Gradient hydraulic loads are applied to the inner surface, and the large-aperture end face is subjected to full-degree-of-freedom constraints to simulate flange fixation, while the small-aperture end remains unconstrained. Figure 14 As shown.

[0087] The residual stress field after the explosive-loaded shell was obtained in step 4 was analyzed using a restart analysis. σ wrapped The residual stress field of the shell after curing with the drug obtained in step 5 σ curedThe predefined fields are added to the initial analysis state to calculate the compressive stress and strain field results within the shell, such as... Figure 15 As shown.

[0088] Step 6-4: Apply the designed internal pressure load to the inner surface of the shell model, perform static analysis, and calculate the total stress field of the shell under the combined action of internal pressure and residual stress. σ total .

[0089] Step 6-5, based on the total stress field σ total Check the internal pressure strength of the shell; if it meets the design requirements, output the tension regime obtained in step 3; if it does not meet the requirements, return to redesign and recalculate.

[0090] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for designing the tension regime of propellant winding molding for composite shells of solid rocket motors, characterized in that, include: Input the winding parameters for the engine composite material housing; Based on the input shell winding parameters, a propellant winding model for engine composite shell is established to describe the stress transfer from the fiber layer to the propellant mandrel and the interlayer stress superposition effect during the winding process. Using the target residual stress as the objective, the shell-loaded winding model is used as a forward calculator. An iterative algorithm is used to solve the initial winding tension values ​​of each layer that satisfy the target residual stress, thereby obtaining the theoretical initial stress regime and converting it into the tension regime of each layer. Simulation calculations are performed based on the obtained tension regime to obtain the residual stress field after the shell is wrapped with the explosive, and to check whether the safety factor of the explosive charge meets the design requirements. If it does, proceed to the next step; if it does not, adjust the target residual stress and iterate the solution of the tension regime again. A calculation model for curing with medicated material was established. The residual stress field after the shell was wrapped with medicated material was simulated and calculated. The thermo-chemical stress generated during the curing process was superimposed to obtain the final manufacturing residual stress field of the shell. Establish a calculation model for the internal pressure strength of the composite material shell, perform simulation calculations based on the final manufacturing residual stress field of the shell, and check whether the internal pressure strength of the shell meets the design requirements; if it does, output the tension regime; otherwise, redesign the tension regime.

2. The method for designing the tension regime of propellant winding molding for solid rocket motor composite shells according to claim 1, characterized in that, The construction process of the engine composite material casing explosive-wound model is as follows: The winding mandrel is made of isotropic material, and its radial displacement field can be obtained based on the thick-walled cylinder theory. With radial stress field The analytical expression for the circumferential strain can be derived by analyzing the radial and circumferential deformations of the infinitesimal element. Radial strain expression ; For the expression of circumferential strain Differentiation yields the strain compatibility equation; by setting the boundary conditions for the composite fiber-wound shell and considering the core mold as a thick-walled cylindrical structure subjected only to equivalent external pressure, the circumferential stress is obtained. With radial stress Analytical expression; Solve for the inner diameter. The displacement field at the point is determined, and then, under the assumption of small deformation, the differential equations of radial stress and circumferential stress with respect to radial displacement are obtained, thus yielding the utilization coefficient. Radial displacement of the composite fiber winding layer characterized A general solution formula is used to determine the radial and circumferential stresses of the fiber winding layer, and the formula is expressed using multiple material property coefficients. Define the winding tension as the winding radius as The tension per unit bandwidth of the winding layer when winding is complete is defined as the winding radius. The circumferential winding tension component of the composite material winding layer is ; Based on the circumferential winding tension component The winding radius is obtained as Circumferential stress of the winding layer ; Determine the radius as The winding layer, with its radial back pressure generated by the circumferential winding tension component, introduces equilibrium conditions at the interface, thereby affecting the coefficient. Solve to determine the radial displacement. Then we obtain the radius as the winding radius as The radial and circumferential stresses of the winding layer; With the first Analysis of the fiber winding layer determined that it exists in the middle layer. The remaining circumferential stress and remaining circumferential tension on the layer are then converted into remaining stress.

3. The method for designing the tension regime of propellant winding molding for solid rocket motor composite shells according to claim 2, characterized in that, The expression for residual stress is as follows: ； in For the first The circumferential stress of the winding layer, where h is the thickness of a single layer of the winding layer. To simplify the calculation settings, ; For the radial stiffness of the propellant core mold, The outer diameter of the drug cartridge core mold. The outer diameter after winding is complete. External radial pressure, , , , The material property coefficients are as follows: ， ， ， ； in, Poisson's ratio represents the circumferential strain caused by radial stress. Poisson's ratio for radial strain caused by circumferential stress; , , These are the elastic moduli of the fiber winding layer in the circumferential and radial directions, respectively. For the first The radius of the winding layer, where M is the total number of winding layers. Let m be the inner diameter of the m-th winding layer. for Circumferential stress at the location.

4. The method for designing the tension regime of propellant winding molding for solid rocket motor composite shells according to claim 1, characterized in that, The initial winding tension values ​​of each layer that satisfy the target residual stress are obtained by reverse engineering using an iterative algorithm, including: In the initial calculation, the initial prestress of each layer is set to be equal to the target value; No. k In the second iteration, the residual stress is recursively updated based on the deviation between the previously calculated residual stress and the target value. Initial stress estimate of the layer The updated initial stress estimate Substituting the shell-borne explosive winding model again, the remaining winding stress was calculated. With initial prestress and The difference and error threshold are used to determine convergence. The iteration terminates when the condition is met. This is the desired theoretical initial stress regime, which is then converted into the tension regime of each layer.

5. The method for designing the tension regime of propellant winding molding for solid rocket motor composite shells according to claim 4, characterized in that, according to The tension system of each layer is obtained through conversion. ;in The thickness of a single layer of fiber winding is given. For the first Layer fiber winding angle, For the first N Layer process tension.

6. The method for designing the tension regime of propellant winding molding for solid rocket motor composite shells according to claim 1, characterized in that, A refined model of single-fiber layer winding was constructed using the tensile profile method, and the winding and forming process of the mid-section fiber of the propellant containing a propellant grain structure was simulated. Construct a numerical simulation boundary condition and constraint system for circumferential and longitudinal winding processes; Based on the step tension system, it is converted into an equivalent circumferential stress or radial pressure load; These loads are applied step by step in the finite element simulation model to simulate the layer-by-layer accumulation and distribution of stress during the winding process; The equivalent temperature field distribution of each fiber layer is determined by layer-by-layer inversion using a trial-and-error method, so that the combined stress field formed by the temperature field and the winding tension has an equivalent mechanical response. Run a simulation of the winding process to obtain the stress state after all winding layers have been applied and reached equilibrium; output the residual stress field of the shell after the drug is wound. The stress field of the propellant core mold is extracted from the residual stress field after the propellant is wrapped in the shell, and its safety factor is calculated based on the yield strength or allowable strain criterion of the propellant material. Check whether the safety factor meets the design requirements; if it does, output the residual stress field after the shell is wrapped with the drug; if it does not, adjust the target residual stress and iterate the solution of the tension regime again.

7. The method for designing the tension regime of propellant winding molding for solid rocket motor composite shells according to claim 1, characterized in that, Using the residual stress field after the shell is wrapped with the drug as the initial stress field, a drug-coated curing calculation model is loaded, and a thermo-mechanical-chemical coupled finite element analysis is performed; temperature field boundary conditions, i.e. curing regime, are set; and the residual stress field after the shell is cured with the drug is calculated.

8. The method for designing the tension regime of propellant winding molding for solid rocket motor composite shells according to claim 1, characterized in that, Establish a calculation model for the internal compressive strength of composite material shells, including: A refined finite element model of the shell, including fiber trajectories, is established, comprising four factors: layup sequence, fiber trajectory, tensile stress field, and curing residual stress field; individual winding layers are sequentially established based on winding process parameters. Calculate the interlayer connection path and, based on the winding direction conversion characteristics, classify the interlayer connection structure into two typical working conditions: longitudinal-circular transition structure and circumferential-longitudinal transition structure; A finite element calculation model for the internal compressive strength of the composite shell was established; the residual stress fields after the shell was wrapped with the drug and after the shell was cured with the drug were added to the initial analysis state in the form of predefined fields, and the results of the internal compressive stress-strain field of the shell were calculated. A design internal pressure load is applied to the inner surface of the shell model, and a static analysis is performed to calculate the total stress field of the shell under the combined action of internal pressure and residual stress. Based on the total stress field, check the internal pressure strength of the shell; if it meets the design requirements, output the tension regime.

9. A terminal device, comprising a processor, a memory, and a computer program stored in the memory; characterized in that, When the processor executes the computer program, it implements the design method for the tension regime of propellant winding molding of the solid rocket motor composite shell as described in any one of claims 1-8.

10. A computer-readable storage medium storing a computer program; characterized in that, When the computer program is executed by the processor, it implements the design method for the tension regime of propellant winding molding of the solid rocket motor composite shell as described in any one of claims 1-8.

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