A solid engine shell strength analysis modeling method

Abstract

This invention relates to the field of solid rocket motor technology, specifically to a method for strength analysis and modeling of solid rocket motor casings. The steps are as follows: S1, import the 3D model of the metal casing into ANSYS software; S2, perform a series of cutting, merging, and deleting operations on the 3D model to convert it into a 2D model; S3, assign material properties to the 2D model and divide it into quadrilateral meshes to obtain a 2D finite element model; S4, based on the coordinate characteristics of the geometric model, select the inner hole line numbers of the front and rear joints of the casing, and sequentially select the inner line groups of the casing according to "points attached to lines" and "lines associated with points," thereby determining the application position of the pressure load; S5, rotate the 2D finite element model by a certain angle to expand it into a 3D model; S6, after applying the pressure load, solve the problem and extract the equivalent stress to evaluate the structural strength of the metal casing. This invention reduces the difficulty of simulation, significantly improves work efficiency, and has good versatility.

Description

Technical Field

[0001] This invention relates to the field of solid rocket motor technology research, specifically to a method for strength analysis and modeling of solid rocket motor casing. Background Technology

[0002] Metal casings not only offer simple manufacturing processes and reliable product performance but also boast low costs, leading to their widespread application in low-cost missile propulsion systems and their increasing use in launch vehicles. On the other hand, with the increasing workload of solid rocket engine development and the significant improvement in engine performance indicators, coupled with a shortened development cycle, higher demands are placed on the speed and efficiency of solid rocket engine feasibility studies. The engine casing structure is simple, easily simplified to a rotating body, and mesh generation is straightforward during preprocessing. Furthermore, metallic materials are typically isotropic, eliminating the need to consider material orientation and layup processes during simulation. Therefore, metal casings better meet the requirements for rapid feasibility studies. In engineering, 3D modeling software is commonly used for geometric design, followed by conversion of the designed geometric model into an intermediate format, and finally importing it into commercial finite element software for simulation calculations to determine the strength performance of the casing structure. However, this method requires casing designers to have considerable simulation experience, and the conversion of various file formats and preprocessing operations are time-consuming and laborious, making it difficult to meet the requirements of rapid feasibility studies. Experienced simulation engineers can use the APDL language provided by ANSYS software for secondary development, summarizing the casing simulation process to form a semi-automated simulation program. Users need to modify the simulation program each time they use it, and the shell model topology applicable to this simulation program must be consistent with the model used when the simulation program was developed, which has obvious limitations. Some engineers adopt the method of directly modeling in the simulation software to achieve parameterization of the geometric model, thereby facilitating pre- and post-processing operations for simulation. However, the modeling operation of the simulation software is too cumbersome, and some complex geometric features cannot even be created. To meet the needs of design and manufacturing, designers must also redraw the model in 3D modeling software, which increases the actual workload by more than double and reduces the efficiency of demonstration. In view of the above reasons, this invention adopts a secondary development approach to develop a structural strength analysis modeling method for solid rocket motor metal shells based on ANSYS software. It can automatically identify the component types in the imported metal shell model and further perform a series of simulation operations such as geometric pre-processing, mesh generation, load application, solution calculation, and result post-processing for each component. The structural strength simulation of the metal shell can be achieved without human intervention, which greatly improves the work efficiency of designers and provides important technical support for the rapid demonstration of solid rocket motors.

[0003] The drawbacks of using existing technologies for structural strength simulation of metal shells are as follows: First, importing the geometric model into commercial simulation software or directly modeling it within commercial software before performing shell structural strength simulation requires operators with certain simulation engineering experience, making it difficult for non-simulation-specialized structural designers to learn. Second, a single shell structural strength simulation generally requires three steps: preprocessing, solution calculation, and post-processing. This involves multiple screening, merging, and deletion operations, making the simulation process overly cumbersome and time-consuming, failing to meet the needs of rapid verification. Third, due to the design habits of different designers, the geometric topologies of different shells vary, requiring semi-automated simulation programs developed based on topology to be modified to varying degrees each time they are used, lacking universality and thus failing to meet practical engineering applications. Finally, due to the lack of conditions for conducting rapid simulation of metal shell structural strength, designers, in order to complete the design within a short timeframe, are forced to artificially increase design margins to ensure structural safety and reliability, but this reduces the overall performance of the engine. In conclusion, this technological bottleneck has become one of the key factors restricting the effective improvement of engine R&D capabilities. Summary of the Invention

[0004] The technical problem to be solved by the present invention

[0005] This invention provides a solid rocket motor casing strength analysis and modeling method to solve the problems of existing casing structure strength simulation requiring high designer expertise, lack of universality, and cumbersome and time-consuming simulation process.

[0006] The technical solution adopted by this invention to solve the technical problem

[0007] A method for strength analysis and modeling of solid engine casing, comprising the following steps:

[0008] S1: Import the 3D model of the metal shell into ANSYS software;

[0009] S2: Perform a series of cutting, merging, and deleting operations on the 3D model to convert it into a 2D model;

[0010] S3: Assign material properties to the two-dimensional model and mesh it with quadrilaterals to obtain a two-dimensional finite element model;

[0011] S4: Based on the coordinate characteristics of the geometric model, screen the inner hole line numbers of the front and rear joints of the shell, and successively select the inner line group of the shell according to the "point attached to the line" and "line associated with the point" to determine the application position of the pressure load.

[0012] S5: Rotate the two-dimensional finite element model by a certain angle to expand it into a three-dimensional model;

[0013] S6: After applying the pressure load, the solution is calculated, and finally the equivalent stress is extracted to evaluate the strength of the metal shell structure.

[0014] Further, step S2 is as follows:

[0015] S21: Restore the working plane coordinates to a position that completely coincides with the global coordinate system, and use the working plane to cut the 3D model to generate a 2D cross section;

[0016] S22: Directly delete all volume elements. At this point, the geometric model contains no volume elements, only point, line, and surface elements.

[0017] S23: Remove face elements with Z=0 by filtering by position. Execute the "Delete face and elements below face" command, and the geometric model will only have point, line and face elements at Z=0.

[0018] S24: Select elements with Y>0 by filtering by position, and delete faces and elements below faces with Y<0; use the Glue and Merge commands to merge all faces, lines and points, thereby forming common edges between different faces.

[0019] Furthermore, the geometric coordinates of S4 are determined with the midpoint of the shell axis as the reference. The shell is regarded as two parts, front and back. Then the minimum radial coordinate of the line element of the front half is the radius of the front pole hole, and the minimum radial coordinate of the line element of the back half is the radius of the rear pole hole.

[0020] Furthermore, the rotation angle of S5 is 30°.

[0021] Furthermore, the quadrilateral meshing of S3 adopts a free mode, and the element type is selected as the 4-node MESH200 element that does not participate in the solution.

[0022] Beneficial effects obtained by the present invention

[0023] This invention provides a method for strength analysis and modeling of the metal shell structure of a solid rocket engine. It encapsulates the main steps of the metal shell structure strength simulation process, such as preprocessing, solution calculation, and postprocessing, into a unified simulation method. This method is integrated into the commercial finite element simulation software ANSYS, enabling engineers to obtain the structural strength of the metal shell in a fast and universal way, thus providing technical support for the design and performance simulation of engine metal shell structures.

[0024] This invention employs an automatic identification method for shell components and a screening method for surfaces to be loaded, transforming the traditional manual process of simulating the strength of metal shell structures into an automated process. This significantly improves work efficiency and plays a crucial supporting role in the rapid demonstration of solid rocket engines. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 Flowchart for strength analysis and modeling of solid rocket motor metal casing structure;

[0027] Figure 2 Entry point for strength analysis and modeling methods for metal shell structures;

[0028] Figure 3 Model of the metal casing of a solid rocket motor;

[0029] Figure 4 Two-dimensional simulation model of the metal casing of a solid rocket motor;

[0030] Figure 5 : A three-dimensional simulation model of the metal casing of a solid rocket motor;

[0031] Figure 6 Equivalent stress distribution cloud map of the metal casing of a solid rocket motor. Detailed Implementation

[0032] This invention provides a structural strength analysis and modeling method for the metal shell of a solid rocket engine. After being embedded into ANSYS software, it can simplify the geometric model of the metal shell imported into ANSYS software with one click, automatically complete mesh generation, load application, solution calculation and result post-processing, and quickly complete the structural strength simulation of the metal shell without human intervention. It has good versatility and provides technical support for the rapid demonstration of solid rocket engines.

[0033] To make the objectives, features, and advantages of the technical solution proposed in this invention more apparent and understandable, the embodiments of the technical solution proposed in this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the proposed technical solution, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] like Figure 1The diagram illustrates the structural strength analysis and modeling process for the metal shell of a solid rocket motor. The 3D model of the metal shell is imported into ANSYS software. First, the working plane coordinates are restored to a position completely aligned with the global coordinate system. The working plane is then used to cut the 3D model, generating a 2D cross-section. Next, all volume elements are directly deleted, leaving the geometric model with only points, lines, and faces. Then, face elements with Z=0 are removed using position filtering. The "Delete face and elements below face" command is executed, leaving only points, lines, and faces at Z=0. Further position filtering retains elements with Y>0, while faces and elements below Y<0 are deleted. The Glue and Merge commands are used to merge all faces, lines, and points, creating common edges between different faces. At this point, the 3D model is converted into a 2D model. Then, the two-dimensional model is assigned the metal material properties of the shell, and the element type is selected as the 4-node MESH200 element that does not participate in the solution. The mesh is generated according to the free mode to obtain the two-dimensional finite element model. At the same time, the minimum and maximum axial coordinates of the model are determined to indirectly determine the axial length of the shell. Taking the midpoint of the shell's axial direction as the reference, the shell is regarded as two parts, front and back. Then, the minimum radial coordinate of the line element of the front half is the radius of the front polar hole, and the minimum radial coordinate of the line element of the back half is the radius of the rear polar hole. Based on the coordinate characteristics of the front and back polar holes, the inner hole line numbers of the front and back joints of the shell can be selected. By iteratively selecting line groups on the inner side of the shell according to "points attached to lines" and "lines associated with points," the Loop function for selecting line elements in the GUI interface is realized, allowing for the selection of connected line elements at once, i.e., the line group for applying the pressure load. Rotating the 2D finite element model by a certain angle, typically 30°, selecting SOLID185 elements for the element expansion option, choosing "from face" for the material properties, and selecting 15 elements, the 2D model is expanded into a 3D model through rotation. Selecting the associated face elements from the pressure load application line group determines the face elements to be subjected to the pressure load, completing the loading process. A portion of the outer contour lines can be obtained based on the model's maximum radial coordinate. Then, the face with the smallest axial coordinate is selected, which is the front skirt end face of the engine shell, and axial constraints are applied to it. The circumferential sections of the geometric model are selected according to angle, and symmetrical constraints are applied. The analysis type is selected as a static problem, and the solution is calculated. Finally, the equivalent stress is extracted to evaluate the strength of the metal shell structure.

[0035] like Figure 2 As shown, this is the entry point for the metal shell structure strength analysis and modeling method. After encapsulating the solid rocket motor metal shell structure strength analysis and modeling method into the ANSYS software, users only need to click the "CASE" button on the ANSYS toolbar, and the software can automatically complete the shell structure strength simulation without human intervention.

[0036] like Figure 3 As shown, this is a model of the metal casing of a solid rocket motor. Using the import function of ANSYS software, the geometric model of the metal casing, drawn in 3D modeling software, was directly imported into ANSYS.

[0037] like Figure 4 As shown, a two-dimensional simulation model of the metal casing of a solid rocket motor is obtained by performing a series of operations such as cutting, merging, and deleting on the imported three-dimensional model.

[0038] like Figure 5 As shown, a three-dimensional simulation model of the metal casing of a solid rocket motor is obtained by rotating the two-dimensional simulation model by a certain angle.

[0039] like Figure 6 The diagram shows the equivalent stress distribution cloud map of the metal casing of a solid rocket motor. After calculation, the equivalent stress distribution of the metal casing under pressure load can be obtained.

[0040] In practice, ① first launch the ANSYS software and select the working directory; ② import the geometric model of the metal shell through the ANSYS software; ③ click the "Case" button on the ANSYS toolbar to automatically start the strength simulation of the metal shell structure. The simulation model and simulation results are automatically saved in the working directory of the ANSYS software.

[0041] This invention summarizes the general steps for simulating the structural strength of solid rocket motor metal shells, introducing an automatic identification method for shell components and a method for screening surfaces to be loaded. This transforms the traditionally manual process of simulating metal shell structural strength into an automated workflow, requiring no prior simulation experience and allowing for one-click operation. This reduces the difficulty of simulating metal shell structural strength, significantly shortens operation time, and markedly improves work efficiency. Furthermore, because this invention can automatically identify the imported geometric features of the metal shell, it has no specific requirements on the shell's topology, exhibiting good versatility.

[0042] To address the complexity of strength simulation operations for metal shell structures, an automatic identification method for shell components and a method for screening surfaces to be loaded were adopted. This transformed the traditionally manual process of strength simulation for metal shell structures into an automated workflow, significantly improving work efficiency and providing crucial support for the rapid demonstration of solid rocket engines.

[0043] This invention provides important technical support for the rapid demonstration of solid rocket engines, greatly improves design efficiency, and shortens engine development time to a certain extent, demonstrating significant application value.

Claims

1. A method for strength analysis and modeling of a solid engine casing, characterized in that, The specific steps are as follows: S1: Import the 3D model of the metal shell into ANSYS software; S2: Perform a series of cutting, merging, and deleting operations on the 3D model to convert it into a 2D model; S3: Assign material properties to the two-dimensional model and divide it into quadrilateral meshes to obtain a two-dimensional finite element model; S4: Based on the coordinate characteristics of the geometric model, screen the inner hole line numbers of the front and rear joints of the shell, and successively select the inner line group of the shell according to "points attached to the line" and "lines associated with the points" to determine the application position of the pressure load. S5: Rotate the two-dimensional finite element model by a certain angle to expand it into a three-dimensional model; S6: After applying the pressure load, solve the calculation and finally extract the equivalent stress to evaluate the strength of the metal shell structure; Specifically, S2 is: S21: Restore the working plane coordinates to a position that completely coincides with the global coordinate system, and use the working plane to cut the 3D model to generate a 2D cross section; S22: Directly delete all volume elements. At this point, the geometric model contains no volume elements, only point, line, and surface elements. S23: Filter face elements by location, execute the "Delete face and elements below face" command, and the geometric model will only have point, line and face elements at Z=0; S24: Select elements with Y>0 by filtering by position, and delete faces and elements below faces with Y<0; use the Glue and Merge commands to merge all faces, lines and points, thereby forming common edges between different faces.

2. The solid rocket motor casing strength analysis and modeling method according to claim 1, characterized in that: The geometric coordinates of S4 are determined with the midpoint of the shell axis as the reference. The shell is regarded as two parts, front and back. Then the minimum radial coordinate of the line element of the front half is the radius of the front pole hole, and the minimum radial coordinate of the line element of the back half is the radius of the rear pole hole.

3. The solid rocket motor casing strength analysis and modeling method according to claim 1, characterized in that: The rotation angle of S5 is 30°.

4. The solid rocket motor casing strength analysis and modeling method according to claim 1, characterized in that: The quadrilateral meshing of S3 adopts a free mode, and the element type is selected as the 4-node MESH200 element that does not participate in the solution.

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