A high-precision parametric modeling method for filament-wound shells

Abstract

The present invention relates to the technical field of solid rocket motor case modeling, and more specifically, to a high-precision parametric modeling method for filament-wound cases. The method comprises: obtaining the structural and process parameters of the wound case; obtaining the total thickness of the wound layers of the case's head section and the outer contour curve of the case; obtaining the upper edges of all spirally wound layers; and obtaining a three-dimensional finite element model of the case. This method improves the design efficiency of complex case structures, enabling accurate and rapid modeling of wound solid rocket motor cases, addressing the current issues of long modeling times and inaccurate structures for wound cases.

Description

Technical Field

[0001] The present invention relates to the technical field of solid rocket engine casing modeling, and in particular to a high-precision parameterized modeling method for a filament-wound casing. Background Art

[0002] The solid rocket motor case is both a vital component of the rocket engine and a major element of the spacecraft structure. Serving as the engine's propellant tank and combustion chamber, it must withstand high internal pressure loads during engine operation while also bearing and transmitting various external loads imposed on the spacecraft. The case characteristic coefficient PV / W (P, V, and W are the case's burst pressure, structural volume, and mass, respectively) is a key indicator of the case's design and production process, placing high demands on the overall performance of the engine case. Composite materials, with their exceptional properties of high specific strength, high specific stiffness, strong corrosion resistance, and customizable material properties, have found widespread application in the aerospace field. The use of filament winding as the forming process for composite pressure vessels enables the case to meet the requirements of lightweight and high internal pressure, achieving structural large-scale and low-cost design.

[0003] Filament-wound composite shells have complex characteristics such as anisotropy, variable thickness, and variable material angles, making many established design and calculation methods for metal pressure vessels inapplicable. Currently, the main shell design methods include grid theory, thin film theory, and the finite element method, but each method has its limitations, making accurate analysis of the shell's mechanical properties relatively complex. Zhang Qian et al. invented a solid rocket engine shell modeling method and system. Based on the outer contour of the core mold model in ABAQUS, they sequentially calculated the coordinates of the starting point of the thickness growth of each winding layer and used B-spline curve fitting to obtain the shell contour curve. This method was used to quickly construct a solid rocket engine shell model. However, it did not take into account complex structural features such as the skirt connection area. When the rocket body is subjected to complex aerodynamic forces, the shell will be subjected to complex loads such as pressure and bending moment through the skirt connection area, which cannot be ignored in structural analysis.

[0004] The wound shell structure is relatively complex, especially the variable angle and thickness distribution of the wound layer and the addition of reinforcement layers at the shell head. The manual modeling process in the commercial finite element software ABAQUS is very complicated and tedious. During the structural optimization process, the structural parameters need to be continuously modified, which consumes a lot of time.

[0005] Therefore, it is necessary to provide a high-precision parametric modeling method for fiber-wound shells to solve the above problems. Summary of the Invention

[0006] The present invention provides a high-precision parametric modeling method for filament-wound shells, which efficiently connects the shell design and analysis processes based on Python scripts, quickly evaluates the shell load-bearing performance during design, thereby shortening the design cycle and solving existing problems.

[0007] The present invention provides a high-precision parametric modeling method for a filament-wound shell using the following technical solutions, including:

[0008] Obtain the structural parameters and process parameters of the wound shell; wherein the structural parameters include: the radius of the barrel section, the length of the barrel section, the length of the major semi-axis of the inner contour ellipse of the head, the length of the minor semi-axis of the inner contour ellipse of the head, the radius of the large pole hole, and the radius of the small pole hole; the process parameters include: the winding layer, the sliding line coefficient, the spiral winding angle of the barrel, the number of cyclic windings, the thickness of the yarn, and the width of the yarn;

[0009] The total thickness of the winding layer of the barrel section is obtained according to the winding layer, and the total thickness of the winding layer of the head section of the shell is calculated according to the structural parameters and process parameters and the cubic spline thickness prediction formula;

[0010] According to the total thickness of the winding layer of the head section and the total thickness of the winding layer of the barrel section, the outer contour curve of the shell is drawn in sections using spline curves;

[0011] Define the upper surface meridian of each spiral winding layer section as the upper edge line, and the upper edge line of the core mold head section is the lower surface meridian line of the spiral winding layer section. Obtain the angle between the tangent line at different positions on the core mold head section contour curve and the shell axis. According to the angle and the total thickness of the winding layer of the head section, obtain the first coordinate change from the upper edge line of the core mold head section contour curve to the corresponding point of the upper edge line of the first spiral winding layer.

[0012] According to the first coordinate variation and the coordinates of the discrete points of the contour curve of the core mold head section, the position coordinates of the upper edge of the first spiral winding layer and each discrete point of the upper edge are obtained; based on the angles between the tangent at different positions on the upper edge of the first spiral winding layer and the axial direction of the shell, and the total thickness of the winding layer of the head section, the second coordinate variation from the upper edge of the first spiral winding layer to the upper edge of the second spiral winding layer is obtained; based on the second coordinate variation and the position coordinates of each point on the upper edge of the first spiral winding layer, the position coordinates of the upper edge of the second spiral winding layer and each point on the upper edge are obtained, and so on, the upper edges of all spiral winding layers are obtained;

[0013] According to the outer contour curve of the shell, a triangular resin-rich area is drawn between every two spiral winding layers on the equatorial circle at the connection between the barrel section and the head section to obtain a two-dimensional modeling curve diagram of the shell half section;

[0014] Based on the two-dimensional modeling curve graph of the shell half section, a three-dimensional finite element model is obtained.

[0015] Preferably, the step of obtaining the angle between the tangent line at different positions on the contour curve of the core mold head section and the axial direction of the shell is:

[0016] Formulate discrete partitioning principles, determine the partitions of the head section and barrel section corresponding to the core mold, and obtain the position coordinates of the corresponding discrete points in each partition on the core mold;

[0017] Obtain the tangent slope of the discrete point on the core mold head section contour curve according to the position coordinates of the discrete point on the core mold head section contour curve and the major semi-axis and minor semi-axis of the core mold head section cross-sectional area at the discrete point;

[0018] According to the slope of the tangent line of the discrete point on the contour curve of the core mold head section, the angle between the tangent line of the discrete point on the contour curve of the core mold head section and the axial direction of the shell is obtained.

[0019] Preferably, the angle between the tangent line of the discrete points on the contour curve of the core mold head section and the axial direction of the shell is expressed as follows:

[0020]

[0021] Where, It represents the angle between the tangent line at the discrete point (x, y) on the contour curve of the core mold head section and the shell axis; Represents the slope of the tangent line at the discrete point (x, y) on the contour curve of the core mold head section; Represents the major semi-axis of the contour curve of the core mold head section; Represents the short semi-axis of the contour curve of the core mold head section.

[0022] Preferably, the position coordinates of discrete points on the outer contour curve of the core mold are obtained according to the core mold reference curve equation.

[0023] Preferably, the expression for the relative coordinate change from the upper edge of the core mold head section to the corresponding point on the upper edge of the first winding layer is:

[0024]

[0025] Where, The first horizontal coordinate variation from the upper edge of the core mold end section to the corresponding point of the upper edge of the first winding layer; Indicates the change in the first ordinate from the upper edge of the core mold head section to the corresponding point on the upper edge of the first winding layer; Indicates the thickness of a single winding layer of the head section; It represents the angle between the tangent line at the discrete point (x, y) on the contour curve of the core mold head section and the shell axis.

[0026] Preferably, the steps of obtaining a three-dimensional finite element model are:

[0027] The starting position of the head of any winding layer in the two-dimensional modeling curve diagram of the half-section of the shell is retracted to obtain a two-dimensional modeling curve diagram after retraction, and the retraction length is less than twice the width of the winding tape;

[0028] Obtain the reinforcement layer in the winding layer corresponding to the two-dimensional modeling curve diagram after the retreat;

[0029] Reinforcing the reinforcement layer in the two-dimensional modeling curve diagram of the half-section of the shell to obtain a target two-dimensional modeling curve diagram;

[0030] Based on the target two-dimensional modeling curve, a three-dimensional finite element model of the shell is generated by rotating around the center of the core mold.

[0031] Preferably, the steps of obtaining the reinforcement layer are:

[0032] Obtaining the remainder after comparing the layer number of the winding layer in the three-dimensional finite element model with a preset value;

[0033] According to the remainder, it is determined whether the winding layer corresponding to the layer number is a reinforcement layer.

[0034] Preferably, the three-dimensional finite element models of the metal joint and the shell are combined to form a model, wherein the metal joint and the shell are bonded with a rubber layer.

[0035] Preferably, the method further comprises: constructing a finite element model of the skirt shell, wherein the steps of constructing the model are:

[0036] Draw the outer contour of the meridian section of the metal skirt according to the characteristic parameters of the metal skirt;

[0037] The outer contour image is used as the initial feature surface and rotated into a metal skirt model;

[0038] Add material properties to the metal skirt model and perform mesh division to obtain the metal skirt finite element model;

[0039] The connection area of ​​the finite element model of the shell and the finite element model of the metal skirt is assembled, and the load and boundary conditions are applied as required to add binding interactions to obtain the finite element model of the shell with skirt.

[0040] The beneficial effects of the present invention are:

[0041] A scripted model based on the Python language, which can be run in finite element software, enables secondary development of Abaqus. By modifying input parameters and running the script, the shell model can be automatically generated. This enables parametric design of wound shells, significantly improving the design efficiency of complex shell structures. It can accurately and quickly build models of wound shells for solid rocket motors, resolving the current issues of long modeling time and inaccurate structures for wound shells. This parametric script allows for multiple design iterations to optimize the performance of the shell model, which is of great significance to the design of composite pressure vessels. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 This is a flow chart of a high-precision parametric modeling method for a filament-wound shell according to the present invention;

[0044] Figure 2 Schematic diagram of fiber winding at the shell head;

[0045] Figure 3 is a schematic diagram of the thickness profile curve of the shell;

[0046] Figure 4 It is a schematic diagram of the resin-rich area at the equator;

[0047] Figure 5 Schematic diagram of the pole hole formed by the winding layer after retreat;

[0048] Figure 6 Schematic diagram of the reinforcement layer and the spiral winding layer;

[0049] Figure 7 It is a schematic diagram of the connection between the shell, metal joint and plug cover;

[0050] Figure 8 Schematic diagram of the curve of the winding angle on the head section changing with the axial position under different sliding line coefficients;

[0051] Figure 9 is a schematic diagram of the shell loading condition;

[0052] Figure 10 Schematic diagram of characteristic structure of skirt connection area;

[0053] Figure 11 Schematic diagram of the finite element model of the shell with skirt. DETAILED DESCRIPTION

[0054] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0055] An embodiment of a high-precision parametric modeling method for a fiber-wound shell of the present invention is described. This embodiment takes a composite material wound shell model with a diameter of φ480 mm after scaling as an example. Figure 1 As shown, this embodiment specifically includes:

[0056] S1. Obtaining structural parameters and process parameters of the winding shell;

[0057] The structural parameters in the embodiment include: a barrel section radius of 237 mm, a barrel section length of 270 mm, a major semi-axis length of the inner contour ellipse of the head of 237 mm, a minor semi-axis length of the inner contour ellipse of the head of 118.5 mm, a large pole hole radius of 120 mm, and a small pole hole radius of 86 mm; the process parameters include: 9 winding layers (i.e., 3 spiral winding layers and 6 circumferential winding layers), a sliding line coefficient of 0.1, a barrel spiral winding angle of 28°, a cyclic winding number of 182, a yarn thickness of 0.225 mm, and a yarn width of 7.5 mm.

[0058] S2. Obtain the total thickness of the winding layer of the head section of the shell and the outer contour curve of the shell;

[0059] Specifically, the total thickness of the winding layer of the barrel section is obtained according to the winding layer, and the total thickness of the winding layer of the head section of the shell is calculated according to the structural parameters and process parameters and the cubic spline thickness prediction formula; according to the total thickness of the winding layer of the head section and the total thickness of the winding layer of the barrel section, the outer contour curve of the shell is drawn in segments using a spline curve.

[0060] Step 21: The steps of obtaining the total thickness of the winding layer of the barrel section according to the winding layer are as follows:

[0061] In this embodiment, the total thickness of the winding layers of the barrel section is 2.7 mm according to the winding layers, that is, the number of winding layers is 3 spiral winding layers and 6 circumferential winding layers, wherein the ply angles of the spiral winding layers are counted as one layer (the thickness of one spiral winding layer is actually twice the thickness of the yarn tape), and the total thickness of the winding layers of the barrel section is 12 times the thickness of the yarn tape, that is, 2.7 mm.

[0062] Step 22: Calculate the total thickness of the winding layer of the head section of the shell according to the structural parameters and process parameters using the cubic spline thickness prediction formula:

[0063] When the fiber is wound around the shell head, the geometric relationship between the head and the yarn is as follows: Figure 2 As shown, assuming that the yarn is in the Figure 2 The straight line is shown below. According to the geometric relationship, in the area within the width of a yarn tape at the end of the end cap, the total thickness of the winding layer at point A is equal to the sum of the thickness of the yarn tape passing between BC during the winding process, that is, the total thickness formula of the winding layer within the width of a yarn tape at the end cap is:

[0064]

[0065] Where, is the number of cyclic windings; is the number of spiral winding layers; is the thickness of the gauze; is the width of the yarn; is the pole hole radius, and r represents the radial coordinate of the winding layer of the shell head section.

[0066] In the area outside the end hole of the head plus twice the width of the yarn tape, the total thickness of the winding layer at point A is:

[0067]

[0068] Where, is the equatorial radius;

[0069] Based on the formula for the total thickness of the winding layer within the polar hole of one yarn tape width, a cubic spline curve is used for fitting. The total thickness of the winding layer at the edge of the polar hole within the polar hole radius plus twice the yarn tape width is:

[0070]

[0071] In the formula, the four constants A, B, C and D are unknown and need to be solved by four constraint equations. According to the actual boundary conditions of the structural geometry, we can obtain: ① the total thickness of the winding layer at the edge of the pole hole; ② the total thickness of the winding layer at the two tape width positions; ③ the first-order derivative of the thickness at the two tape width positions is continuous; ④ the total amount of fiber bundles within the two tape widths is consistent. Solving the four constraint conditions ①, ②, ③, and ④, the total amount of fiber bundles within the two tape widths can be obtained as follows:

[0072]

[0073] Where, Indicates the total amount of fiber bundles within two tape widths; Indicates the number of loop windings; Indicates the number of layers of spiral winding; represents the polar aperture radius; Indicates the thickness of the yarn; It represents the pole hole radius plus twice the ribbon width; It represents the pole hole radius plus the width of the yarn tape; Represents the radial coordinate of the winding layer of the shell head section.

[0074] Finally, the total thickness of the winding layer in the area within the radius of the large head side pole hole plus twice the width of the yarn tape is:

[0075]

[0076] The total thickness of the winding layer in the area within the small head side pole hole radius plus twice the ribbon width is:

[0077]

[0078] The total thickness of the winding layer in the area outside the pole hole radius plus twice the width of the yarn is:

[0079]

[0080] Step 23: Draw the outer contour curve of the shell as follows:

[0081] Since the lower surface of the first winding layer is the outer contour of the core mold model, the outer contour coordinates of the core mold model can be obtained by the core mold reference curve equation Then, based on the total thickness of the winding layer of the head section and the total thickness of the winding layer of the barrel section obtained in step 22, the outer contour curve of the shell is drawn segmentally using a spline curve, such as Figure 3 As shown, the red line represents the outer contour curve of the shell, and the black line represents the inner contour curve of the shell (i.e. the outer contour curve of the core mold).

[0082] S3, obtaining the upper edges of all spirally wound layers;

[0083] Since the calculation of the contour curve of the shell's head section is an important step for multi-layer fiber-wound composite shells, the accurate generation of this data will directly affect the accuracy of the shell's finite element model. In addition, a certain point on the outer contour line of each spirally wound layer is obtained by offsetting a certain thickness value along the outer normal direction of the core mold at the corresponding point of the inner layer contour. The thickness direction of the shell head is the normal direction of the head curve, which cannot be directly used to calculate the coordinates of each shell winding layer. Therefore, it is necessary to calculate the change in thickness in the coordinate axis direction based on the relationship between the contour curve of the core mold head section and the coordinate axis. Therefore, the upper surface meridian of each spirally wound layer section is defined as the upper edge line, and the upper edge line of the core mold head section is the lower surface meridian of the spirally wound layer section.

[0084] Step 31: Obtaining the angles between the tangent lines at different positions on the core mold head section contour curve and the shell axis:

[0085] Step 311: formulate a discrete partitioning principle, determine the partitions of the head section and the barrel section corresponding to the core mold, and obtain the position coordinates of the corresponding discrete points in each partition on the core mold.

[0086] In this embodiment, because the thickness of each winding layer is taken into account during layer-by-layer modeling, the layup information for each winding layer is stored in three lists (0, 1, and 2), corresponding to the left head section, the barrel section, and the right head section, respectively. Each list is defined as a tuple. The principle of discrete partitioning is as follows: different discrete point step sizes are set for the head section and the barrel section of the shell (the same for the left and right head sections), and the number of partitions is determined with the discrete point as the center. In this embodiment, the head section of the shell is divided into 90 intervals and the barrel section is divided into 6 intervals. The head section and the barrel section are discretized in the axial and radial directions to ensure that areas of different curvatures can be carefully processed.

[0087] Step 312: Obtain the tangent slope of the discrete point on the core mold head section contour curve according to the position coordinates of the discrete point on the core mold head section contour curve and the major semi-axis and minor semi-axis of the core mold head section cross-sectional area at the discrete point, that is:

[0088] The core mold head section contour curve equation is derived to obtain the tangent slope at different positions on the core mold head section contour curve, that is, the tangent slope is:

[0089]

[0090] Where, It represents the slope of the tangent line at the discrete point (x, y) on the contour curve of the core mold head section; (x, y) represents the discrete point on the contour curve of the core mold head section; Represents the major semi-axis of the cross-sectional area at the discrete point (x, y) on the contour curve of the core mold head section; Represents the minor semi-axis of the cross-sectional area at the discrete point (x, y) on the contour curve of the core mold head section.

[0091] Step 313: Obtain the angle between the tangent line of the discrete point on the core mold head section contour curve and the shell axis according to the tangent line slope of the discrete point on the core mold head section contour curve, that is, the expression is:

[0092]

[0093] Where, It represents the angle between the tangent line at the discrete point (x, y) on the contour curve of the core mold head section and the shell axis; Represents the slope of the tangent line at the discrete point (x, y) on the contour curve of the core mold head section; Represents the major semi-axis of the contour curve of the core mold head section; Represents the short semi-axis of the contour curve of the core mold head section.

[0094] Step 32, obtaining the first coordinate variation from the upper edge of the core mold head section contour curve to the corresponding point of the upper edge of the first spiral winding layer is as follows:

[0095]

[0096] Where, Indicates the horizontal coordinate change from the upper edge of the core mold head section to the corresponding point of the upper edge of the first winding layer; Indicates the change in the ordinate from the upper edge of the core mold head section to the corresponding point on the upper edge of the first winding layer; Indicates the thickness of a single winding layer of the head section; It represents the angle between the tangent line at the discrete point (x, y) on the contour curve of the core mold head section and the shell axis.

[0097] Among them, in the barrel section , that is, the corresponding point of the upper edge line of the first spirally wound layer in the barrel section has only a change in the y direction (i.e., the radial direction of the barrel), and the change in the upper edge line of the first spirally wound layer in the barrel section can be obtained.

[0098] Step 34: According to the first coordinate variation and the coordinates of the discrete points of the contour curve of the core mold head section, the position coordinates of the upper edge of the first spiral winding layer and each discrete point of the upper edge are obtained; based on the angles between the tangent at different positions on the upper edge of the first spiral winding layer and the axial direction of the shell, and the total thickness of the winding layer of the head section, the second coordinate variation from the upper edge of the first spiral winding layer to the upper edge of the second spiral winding layer is obtained; based on the second coordinate variation and the position coordinates of each point of the upper edge of the first spiral winding layer, the position coordinates of the upper edge of the second spiral winding layer and each point of the upper edge are obtained, and so on, the upper edges of all spiral winding layers are obtained, wherein the position coordinates of each discrete point of the upper edge of the first spiral winding layer corresponding to the barrel section can be obtained based on the coordinates of the discrete points of the contour curve of the core mold barrel section and the variation of the barrel section, and so on, the coordinate information of each discrete point of the upper edge of the spiral winding layer is calculated layer by layer from bottom to top, and the upper edges of all spiral winding layers of the shell can be obtained.

[0099] S4, obtaining a three-dimensional finite element model of the shell;

[0100] Specifically, according to the outer contour curve of the shell, a triangular resin-rich area is drawn between every two spiral winding layers on the equatorial circle at the connection between the barrel section and the head section to obtain a two-dimensional modeling curve graph of the shell half section; based on the two-dimensional modeling curve graph of the shell half section, a three-dimensional finite element model of the shell is obtained.

[0101] Step 41: The steps of drawing a triangular resin-rich area between every two spirally wound layers on the equatorial circle at the connection between the barrel section and the head section are as follows:

[0102] Since the fiber winding process is carried out in a manner that the spiral winding layer and the hoop winding layer are spaced apart from each other, the hoop winding layer ends at the equatorial circle of the head, and a sudden change in thickness occurs at a local position. Therefore, when calculating the position of the hoop winding layer, special treatment is required at the equatorial circle. A triangular resin-rich area is added between every two winding layers on the equatorial circle at the connection between the barrel section and the head section. At this time, the coordinate points of the head area are not updated, and then the upper edge line of the next spiral winding layer is drawn, thereby realizing continuous change of the winding layer and obtaining the following: Figure 4 The two-dimensional modeling curve diagram of the shell half section is shown.

[0103] Step 42: Based on the two-dimensional modeling curve diagram of the half-section of the shell, the steps of obtaining a three-dimensional finite element model of the shell are as follows:

[0104] Step 421: The starting position of any winding layer in the two-dimensional modeling curve of the shell half section is deflected to obtain a two-dimensional modeling curve after deflection, and the deflection length is less than twice the width of the winding tape. That is, due to the consideration of the hole expansion process in the three-dimensional finite element model, the thickness of the fiber winding layer within twice the width of the smooth head opening edge is used. By setting the starting position of the thickness of any winding layer, different thickness distributions can be achieved, and the deflection length is less than twice the width of the tape, such as Figure 5 As shown, the shell structure of the pole hole area after the pole hole is wound to simulate the retreat. After the pole hole of the winding layer retreats, the pole hole radius of this layer increases, and the angle and thickness distribution of the winding layer are recalculated based on the non-geodesic linear design method and the cubic spline method.

[0105] Step 422, the step of obtaining the reinforcement layer in the winding layer corresponding to the two-dimensional modeling curve diagram after the retreat is:

[0106] In order to give full play to the performance of composite materials, the shell head can be reinforced to improve the head bearing capacity and the shell characteristic coefficient, that is, the three-dimensional finite element model is reinforced. The reinforcement steps are: obtain the remainder after comparing the layer number K of the winding layer in the three-dimensional finite element model with the preset value. In this embodiment, the preset value is set to 3. When the remainder after comparing K / 3 is 3 or 4, the winding layer corresponding to the layer number is the reinforcement layer; Figure 6 As shown, the reinforcement layer thickness and angle are set to reinforce the reinforcement layer. The ply angle is calculated based on relevant theories, and then the reinforcement area is identified and the corresponding reinforcement thickness and angle are set to accurately restore the distribution of the reinforcement material. It should be noted that the reinforcement layer is equivalent to adding a spiral layer between the two spirally wound layers at the head position.

[0107] Among them, when the remainder of K / 5 is 0, 1 or 2, the winding layer corresponding to the layer number is the hoop winding layer and the spiral winding layer, and the layer angles are 90°, and ( is the winding angle).

[0108] Step 423: Reinforce the reinforcement layer in the two-dimensional modeling curve diagram of the half-section of the shell to obtain a target two-dimensional modeling curve diagram; based on the target two-dimensional modeling curve diagram, rotate around the center of the core mold to generate a three-dimensional finite element model of the shell.

[0109] Step 4231. Since the geometric structure of the wound shell changes periodically along the circumferential direction, for this type of structure, by performing two-dimensional modeling of the shell half-section and then applying cyclic symmetry constraints on the circumferential boundary, the computational complexity of the three-dimensional finite element model can be greatly reduced while ensuring the analysis accuracy.

[0110] Step 4232: Use engineering constants to define the composite modulus of the 3D finite element model. Direct stiffness reduction is achieved through the user-defined field variable FIELD. The user subroutine USDFLD determines damage initiation and controls damage evolution. When the stress state at a material point meets the corresponding failure criterion, the value of the field variable changes from 0 to 1, reflecting the state of the damage variable. If damage occurs, the calculation is performed using the reduced material parameters. The load is then increased until the calculation is complete or converges. The material parameters are shown in Table 1.

[0111] Table 1

[0112]

[0113] Among them, the material is assigned to the three-dimensional finite element model: the partitions of each winding layer in the three-dimensional finite element model are assigned material directions according to their axial positions. A spiral winding layer is composed of two positive and negative winding layers, which are alternately wound with the hoop winding layer. The layers of the winding shell have The winding angles at different positions of the shell are calculated based on the non-geodesic winding line design theory. The principle formula is as follows:

[0114] The winding angle differential equation is:

[0115]

[0116] Where, is the sliding line coefficient, is the winding angle, Indicates the radial coordinate of the winding layer of the shell head section, corresponding to and The first and second derivatives of the radial coordinates of the winding layer are respectively calculated. The winding angle is determined by the geometric shape of the head surface and the sliding line coefficient, and is solved using the fourth-order Runge-Kutta method, as shown in Figure 8As shown in the figure, under different sliding line coefficients, the winding angle distribution of the shell head has greater changes and design space.

[0117] Step 4233: Set material properties, create material properties for the resin-rich area, metal skirt, metal joint, and rubber layer. All of them are isotropic materials, and assign them to the corresponding areas.

[0118] Step 4234: Divide the mesh. In this embodiment, eight-node linear hexahedral elements (C3D8R) are used in the shell wrapping layer area, and the hourglass control option is enhanced. Wedge elements (C3D6) are used in the resin-rich area. C3D8R elements are also used for the metal joints, metal skirts, and rubber layers.

[0119] Step 4235, interaction settings: According to step 4231, apply cyclic symmetry constraints on the annular boundary, with a total number of sectors of 360° / sector angle; apply binding constraints on the inner surface of the two metal joints and the corresponding rubber layer, and on the lower surface of the shell and the corresponding rubber layer; set the analysis step type to static general, turn on large geometric deformation, and specify a dissipated energy fraction of 0.02%. The load type is inside pressure, and the first step of the analysis step applies a pressure of 17MPa to the shell structure. After reaching a stable state, the pressure is gradually increased to 22MPa in the second step. Reduce the maximum incremental step size to facilitate observation of the failure state. Figure 9 As shown, the constraint method is to fix the upper end face of the joint and constrain the degrees of freedom other than the longitudinal displacement of the lower end face of the joint.

[0120] Step 4236, as Figure 7 As shown in the figure, when the shell is working, the entire internal surface is subjected to internal pressure load. The metal joints set at both ends of the shell are connected to the plugging cap to ensure the sealing of the container. Therefore, they cannot be ignored in the analysis. Therefore, the metal joints and the plugging cap are combined into a model in the three-dimensional finite element model of the shell, and a rubber layer is used to bond the metal joints to the shell.

[0121] In addition, the shell is usually connected to the rocket body structure through a metal skirt and a flange. The present invention constructs a finite element model of the shell including the skirt based on the flange structure parameters, skirt parameters, rubber layer parameters and winding layer parameters. The specific steps are as follows:

[0122] Step 1: Draw the outer contour of the meridian section of the metal skirt according to the characteristic parameters of the metal skirt. Figure 10 The metal skirt structure and characteristic parameters of the metal skirt are shown in Table 2.

[0123] Table 2

[0124]

[0125] Since the outer winding reinforcement layer of the metal skirt has a step change in thickness direction at the end of the metal skirt, there will be problems of discontinuous ply and excessive fiber turning angle. Therefore, a triangular area is designed at the end of the rubber layer to balance the thickness mutation generated by the metal skirt and the rubber. Among them, the outer winding reinforcement layer of the metal skirt is based on the geometric relationship. A spiral winding layer is added outside the outer contour curve of the meridian section of the metal skirt. The rubber layer is Figure 10 Medium purple area.

[0126] Step 2: Use the outer contour as the initial feature surface and rotate it into a metal skirt model.

[0127] Step 3: Add material properties to the metal skirt model and perform mesh division to obtain the finite element model of the metal skirt.

[0128] The steps for adding material properties are as follows: Draw a split sketch of the metal skirt model, then partition the model by rotational splitting, so that material properties can be assigned to each block. Referring to the characteristic parameters of the metal skirt, the metal skirt, rubber transition layer, and the axially wound reinforcement layer and circumferentially wound reinforcement layer on the skirt are separated, and then material properties are added to the metal skirt model. Referring to the reduction method of material properties under different damage failure modes, variables are read for each partition of the metal skirt model according to its geometric reference pattern coordinate position, material properties are set, and material orientation is set for the fiber layup in a discrete manner.

[0129] Then, meshing is performed to obtain the finite element model of the metal skirt.

[0130] Step 4: Assemble the connection area of ​​the shell finite element model and the metal skirt finite element model, apply loads and boundary conditions as required, add binding interactions, and obtain the finite element model of the shell with skirt. The finite element model of the shell with skirt is as follows: Figure 11 shown.

[0131] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-precision parametric modeling method for a filament-wound shell, characterized in that: include: Obtain the structural parameters and process parameters of the wound shell; wherein the structural parameters include: the radius of the barrel section, the length of the barrel section, the length of the major semi-axis of the inner contour ellipse of the head, the length of the minor semi-axis of the inner contour ellipse of the head, the radius of the large pole hole, and the radius of the small pole hole; the process parameters include: the winding layer, the sliding line coefficient, the spiral winding angle of the barrel, the number of cyclic windings, the thickness of the yarn, and the width of the yarn; The total thickness of the winding layer of the barrel section is obtained according to the winding layer, and the total thickness of the winding layer of the head section of the shell is calculated according to the structural parameters and process parameters and the cubic spline thickness prediction formula; According to the total thickness of the winding layer of the head section and the total thickness of the winding layer of the barrel section, the outer contour curve of the shell is drawn in sections using spline curves; Define the upper surface meridian of each spiral winding layer section as the upper edge line, and the upper edge line of the core mold head section is the lower surface meridian line of the spiral winding layer section. Obtain the angle between the tangent line at different positions on the core mold head section contour curve and the shell axis. According to the angle and the total thickness of the winding layer of the head section, obtain the first coordinate change from the upper edge line of the core mold head section contour curve to the corresponding point of the upper edge line of the first spiral winding layer. According to the first coordinate variation and the coordinates of the discrete points of the contour curve of the core mold head section, the position coordinates of the upper edge of the first spiral winding layer and each discrete point of the upper edge are obtained; based on the angles between the tangent at different positions on the upper edge of the first spiral winding layer and the axial direction of the shell, and the total thickness of the winding layer of the head section, the second coordinate variation from the upper edge of the first spiral winding layer to the upper edge of the second spiral winding layer is obtained; based on the second coordinate variation and the position coordinates of each point on the upper edge of the first spiral winding layer, the position coordinates of the upper edge of the second spiral winding layer and each point on the upper edge are obtained, and so on, the upper edges of all spiral winding layers are obtained; According to the outer contour curve of the shell, a triangular resin-rich area is drawn between every two spiral winding layers on the equatorial circle at the connection between the barrel section and the head section to obtain a two-dimensional modeling curve diagram of the shell half section; Based on the two-dimensional modeling curve graph of the shell half section, a three-dimensional finite element model is obtained.

2. A high-precision parametric modeling method for a filament-wound shell according to claim 1, characterized in that: The steps for obtaining the angle between the tangent line at different positions on the core mold head section contour curve and the shell axis are as follows: Formulate discrete partitioning principles, determine the partitions of the head section and barrel section corresponding to the core mold, and obtain the position coordinates of the corresponding discrete points in each partition on the core mold; Obtain the tangent slope of the discrete point on the core mold head section contour curve according to the position coordinates of the discrete point on the core mold head section contour curve and the major semi-axis and minor semi-axis of the core mold head section cross-sectional area at the discrete point; According to the slope of the tangent line of the discrete point on the contour curve of the core mold head section, the angle between the tangent line of the discrete point on the contour curve of the core mold head section and the axial direction of the shell is obtained.

3. A high-precision parametric modeling method for a filament-wound shell according to claim 2, characterized in that: The expression for the angle between the tangent line of the discrete points on the contour curve of the core mold head section and the shell axis is: Where, Represents the angle between the tangent line at the discrete point (x, y) on the contour curve of the core mold head section and the shell axis; Represents the slope of the tangent line at the discrete point (x, y) on the contour curve of the core mold head section; Indicates the major semi-axis of the contour curve of the core mold head section; Represents the short semi-axis of the contour curve of the core mold head section.

4. The high-precision parametric modeling method for a filament-wound shell according to claim 2, characterized in that: The position coordinates of discrete points on the outer contour curve of the core mold are obtained according to the core mold reference curve equation.

5. The high-precision parametric modeling method for a filament-wound shell according to claim 1, characterized in that: The expression of the first coordinate change from the upper edge of the core mold head section to the corresponding point of the upper edge of the first winding layer is: Where, The first horizontal coordinate variation from the upper edge of the core mold end section to the corresponding point of the upper edge of the first winding layer; Indicates the change in the first ordinate from the upper edge of the core mold head section to the corresponding point on the upper edge of the first winding layer; Indicates the thickness of a single winding layer of the head section; It represents the angle between the tangent line at the discrete point (x, y) on the contour curve of the core mold head section and the shell axis.

6. The high-precision parametric modeling method for a filament-wound shell according to claim 1, characterized in that: The steps to obtain a three-dimensional finite element model are: The starting position of the head of any winding layer in the two-dimensional modeling curve diagram of the half-section of the shell is retracted to obtain a two-dimensional modeling curve diagram after retraction, and the retraction length is less than twice the width of the winding tape; Obtain the reinforcement layer in the winding layer corresponding to the two-dimensional modeling curve diagram after the retreat; Reinforcing the reinforcement layer in the two-dimensional modeling curve diagram of the half-section of the shell to obtain a target two-dimensional modeling curve diagram; Based on the target two-dimensional modeling curve, a three-dimensional finite element model of the shell is generated by rotating around the center of the core mold.

7. A high-precision parametric modeling method for a filament-wound shell according to claim 6, characterized in that: The steps to obtain the reinforcement layer are: Obtaining the remainder after comparing the layer number of the winding layer in the three-dimensional finite element model with a preset value; According to the remainder, it is determined whether the winding layer corresponding to the layer number is a reinforcement layer.

8. The high-precision parametric modeling method for a filament-wound shell according to claim 1, characterized in that: The three-dimensional finite element models of the metal joint and the shell are combined and modeled, wherein the metal joint and the shell are bonded with a rubber layer.

9. The high-precision parametric modeling method for a filament-wound shell according to claim 1, characterized in that: Also includes: The finite element model of the skirt shell is constructed in the following steps: Draw the outer contour of the meridian section of the metal skirt according to the characteristic parameters of the metal skirt; The outer contour image is used as the initial feature surface and rotated into a metal skirt model; Add material properties to the metal skirt model and perform mesh division to obtain the metal skirt finite element model; The connection area of ​​the finite element model of the shell and the finite element model of the metal skirt is assembled, and the load and boundary conditions are applied as required to add binding interactions to obtain the finite element model of the shell with skirt.

Images