Finite element mesh modeling method for composite layer of composite material gas cylinder

Abstract

The invention relates to the technical field of high-pressure containers, in particular to a finite element mesh modeling method for a composite layer of a composite material gas cylinder, which comprises the following steps: firstly, acquiring a gas cylinder lining geometric model; importing finite element simulation software to carry out geometric editing and shell unit grid division; then, the thicknesses, the winding angles and the material attributes of the shell units at the end sockets and the barrel are assigned, the thicknesses and the winding angles of the barrel and the shell units are the same, and the thicknesses and the winding angles of the shell units are calculated according to the coordinates of the center points of the shell units for the end sockets; and finally, assigning the shell unit thickness, the winding angle and the material attribute of the transition area between the end socket and the cylinder. According to the method, the finite element mesh model of the composite layer of the composite gas cylinder based on the composite mesh theory is established, the geometric structure of the composite layer of the composite gas cylinder is restored to the maximum extent, the modeling efficiency is improved, the calculation error caused by mesh modeling is reduced, the calculation precision is improved, and the calculation cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of high-pressure vessels, and in particular to a finite element mesh modeling method for composite layers of composite gas cylinders. Background Art

[0002] Composite gas cylinder simulation analysis is an important tool for composite gas cylinder design. Through simulation analysis, it can be used to optimize the cylinder lining and composite layer structure, predict the cylinder burst pressure, and study operating characteristics.

[0003] The composite material layers in composite gas cylinders are anisotropically wound, resulting in complex distributions of composite layer thickness and winding angles at both the cylinder and head. Specifically, the cylinder utilizes both helical and circumferential winding, with the thickness and winding angles being consistent throughout. The head utilizes only helical winding, with the thickness and winding angles varying regularly from the major to the minor diameter of the head.

[0004] Based on the above structural characteristics, researchers proposed a finite element simulation method based on composite material mesh theory, which provides a powerful tool for the study of composite material gas cylinders. In the finite element mesh modeling process of the composite layer of the composite gas cylinder, in theory, it is only necessary to assign parameters such as thickness and winding angle to each composite material layer mesh unit. However, due to the large number of units and the large number of composite material layers, the modeling process requires a large number of repetitive calculations and operations, making it difficult to model efficiently and accurately. Once the parameters such as the cylinder structure size and composite material performance are modified, the assignment needs to be repeated, which is not conducive to the development of research related to composite gas cylinders. Summary of the Invention

[0005] The present application provides a finite element mesh modeling method for a composite material gas cylinder composite layer, which improves the efficiency of finite element mesh modeling of a composite material gas cylinder composite layer and reduces the calculation error caused by mesh modeling.

[0006] In order to achieve the above-mentioned purpose, the present application provides a finite element mesh modeling method for a composite material gas cylinder composite layer, comprising the following steps: Step 1: obtaining a geometric model of the gas cylinder lining, importing the geometric model into finite element simulation software, editing the geometric model to obtain the composite layer surface at the head and the cylinder; Step 2: dividing the head and the cylinder into quadrilateral shell element meshes; Step 3: extracting shell element information and node coordinates, grouping the shell elements according to the shell element node coordinates, and screening out representative shell elements; Step 4: outputting the four node coordinates of the representative shell element, and calculating the representative shell element according to the node coordinates. Center coordinates; Step 5: Take the center coordinates of the representative shell unit as input, and calculate the thickness and winding angle of the representative shell unit according to the composite layer structure of the head; Step 6: According to the shell unit grouping information, assign the thickness, winding angle and material properties of each group of shell units corresponding to each representative shell unit; Step 7: Input the head shell unit mesh information into the finite element simulation software; Step 8: According to the composite layer structure and performance parameters of the cylinder, assign the thickness, winding angle and material properties of the cylinder shell unit as a whole; Step 9: Optimize the shell unit thickness in the transition area of ​​the head and cylinder based on the thickness of the shell units.

[0007] Furthermore, in step 1, the geometric model of the gas cylinder liner includes: a three-dimensional geometric model of the axisymmetric 1 / 2 or 1 / 4 of the composite gas cylinder liner; and a two-dimensional geometric model of the composite material layer of the composite gas cylinder head and barrel.

[0008] Furthermore, in step 2, dividing the quadrilateral shell element mesh of the head and cylinder includes the following steps:

[0009] Step 2.1: Divide the cylinder head and cylinder into quadrilateral shell unit grids at intervals of 2 degrees along the circumferential direction of the cylinder head. Step 2.2: Arrange the grids neatly along the axial direction of the cylinder head, and the axial size of the grids decreases evenly from the major diameter to the minor diameter of the cylinder head.

[0010] Furthermore, in step 3, along the circumferential direction of the cylinder head, each column of shell elements is a group, and the shell element with the smallest number in each group of shell elements is the representative shell element.

[0011] Furthermore, in step 4, the center coordinates of the representative shell element are calculated using the following formula:

[0012]

[0013] Where i is the representative shell element number, xn(i, j), yn(i, j), and zn(i, j) are the coordinates of the jth node of the i-th element.

[0014] Furthermore, in step 5, the representative shell element thickness and winding angle are defined as functions of the shell element center coordinates.

[0015] Furthermore, in step 6, the thickness and winding angle of each group of shell elements are the same as the thickness and winding angle of the representative shell elements of the group.

[0016] Furthermore, in step 9, the thickness of the shell elements in the transition region is between the thickness of the shell elements in the head and the cylinder, and the thickness of the shell elements in the transition region decreases uniformly from the cylinder to the head.

[0017] This application provides a finite element mesh modeling method for composite gas cylinder composite layers, which has the following features:

[0018] Beneficial effects:

[0019] This application establishes a finite element mesh model of the composite layer of a composite gas cylinder based on composite mesh theory, which restores the geometric structure of the composite layer of the composite gas cylinder to the greatest extent, improves the efficiency of modeling, arranges the surface mesh unit specifications as a whole, reduces the calculation error caused by mesh modeling, improves the calculation accuracy and reduces the calculation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings that constitute part of this application are used to provide a further understanding of this application and make other features, objects and advantages of this application more apparent. The illustrative embodiment drawings of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0021] Figure 1 1 is a flow chart of a finite element mesh modeling method for a composite material gas cylinder composite layer according to an embodiment of the present application;

[0022] Figure 2 This is a schematic diagram of a three-dimensional geometric model of an axisymmetric 1 / 4 of a composite material gas cylinder liner provided in an embodiment of the present application;

[0023] Figure 3 Schematic diagram of a quadrilateral shell element mesh and a representative shell element provided according to an embodiment of the present application;

[0024] Figure 4 Schematic diagram of the Abaqus finite element simulation software assignment program interface provided according to an embodiment of the present application;

[0025] Figure 5 It is a schematic diagram of the assignment procedure flow provided according to an embodiment of the present application;

[0026] Figure 6 Schematic diagram of the thickness and angle distribution of the composite material layer head shell unit provided in an embodiment of the present application;

[0027] Figure 7 It is a schematic diagram of the finite element mesh (including the transition mesh area) of the composite layer of the composite gas cylinder provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0029] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0030] In this application, terms such as "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "center," "vertical," "horizontal," "transverse," and "longitudinal" indicate positions or locations based on the positions or locations shown in the accompanying drawings. These terms are primarily intended to better describe this application and its embodiments and are not intended to limit the devices, elements, or components indicated to having a specific orientation, or to being constructed or operated in a specific orientation.

[0031] Furthermore, some of the above terms may be used to express other meanings besides indicating a position or location. For example, the term "on" may also be used to indicate a dependency or connection in certain circumstances. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0032] Additionally, the term "plurality" shall mean two or more.

[0033] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] like Figure 1As shown, the present application provides a finite element mesh modeling method for a composite layer of a composite gas cylinder. First, the geometric model of the gas cylinder liner is obtained; then, the finite element simulation software is imported for geometric editing and shell element meshing; then, the thickness, winding angle, and material properties of the shell elements at the head and cylinder are assigned respectively. For the cylinder, the thickness and winding angle of the shell elements are the same everywhere. For the head, the shell element thickness and winding angle are calculated based on the coordinates of the center point of the shell element; finally, the shell element thickness, winding angle, and material properties of the transition area between the head and the cylinder are assigned. Specifically, the steps include:

[0035] Step 1: Obtain the geometric model of the cylinder liner, import the geometric model into the finite element simulation software, and edit the geometric model to obtain the composite layer surfaces at the head and barrel. The geometric model of the cylinder liner includes: a 3D geometric model of the axisymmetric 1 / 2 or 1 / 4 of the composite cylinder liner; and a 2D geometric model of the composite material layer of the composite cylinder head and barrel.

[0036] Specifically, in the embodiment of the present application, a three-dimensional geometric model of an axisymmetric 1 / 4 of the composite gas cylinder liner is taken as an example, where the cylinder axis coincides with the X-axis. The three-dimensional geometric model is imported into the Abaqus finite element simulation software, and all outer surfaces of the three-dimensional geometric model are extracted and retained, while other surfaces are deleted and the surface in contact with the composite layer is retained as the composite layer surface; Figure 2 As shown, the composite layer surface includes the head, the cylinder and the transition area between the two.

[0037] Step 2: Divide the quadrilateral shell element mesh of the head and cylinder, including:

[0038] Step 2.1: Divide the cylinder head and cylinder into quadrilateral shell element meshes at 2-degree intervals along the cylinder head circumference.

[0039] Step 2.2: The grids are arranged neatly along the axial direction of the cylinder head, and the axial size of the grids decreases evenly from the major diameter to the minor diameter of the cylinder head;

[0040] Specifically, in the embodiments of the present application, Figure 3 As shown in the figure, the composite shell unit is divided into regular grids, which are evenly divided into 45 parts along the circumferential direction and 62 parts along the axial direction. The grid density increases gradually from the large diameter to the small diameter of the head, and a row of axial units on the XY plane in the figure is selected as the representative unit.

[0041] Step 3: Extract shell element information and node coordinates, group shell elements according to the shell element node coordinates, and select representative shell elements;

[0042] Specifically, such as Figure 4-5As shown in the figure, write a program to input the geometric parameters of the gas cylinder, including: pole hole diameter (d0), liner outer diameter (D), spiral winding single layer thickness (hfa); input the head mesh information, including: total number of elements (Etotal), total number of nodes (Ntotal), maximum element number (Emax), minimum element number (Emin), number of circumferential meshes (Nθ); input the composite layer structure parameters at the head, including: material name (Material), number of integration points (Integration Points), layer name (Ply Name); read the coordinates of the head unit nodes.

[0043] More specifically, the shell elements are grouped according to the read shell element node coordinates. Each column of elements along the annular direction is divided into a group. The shell element with the smallest number in each group of shell elements is the representative shell element. The element number of each group and the representative element number are recorded.

[0044] Step 4: Output the four node coordinates of the representative shell element and calculate the center coordinates of the representative shell element based on the node coordinates;

[0045] Specifically, the following formula is used to calculate the center coordinates of the representative shell element:

[0046]

[0047] Where i is the representative shell element number, xn(i, j), yn(i, j), and zn(i, j) are the coordinates of the jth node of the i-th element.

[0048] Step 5: Using the center coordinates of the representative shell element as input, calculate the thickness and winding angle of the representative shell element according to the composite layer structure of the head;

[0049] Specifically, according to the distance calculation formula between a point and a line in the coordinate system, the distance between the center of the representative shell element and the axis of the gas cylinder is calculated, and the thickness and winding angle of the representative shell element are further calculated based on the distance result.

[0050] Step 6: Based on the shell element grouping information, assign values ​​for the shell element thickness, winding angle, and material properties for each group of representative shell elements, and output the head mesh parameters according to the Abaqus simulation software file format;

[0051] Step 7: Input the mesh information of the head shell unit into the Abaqus finite element simulation software, such as Figure 6 As shown, shell elements with consecutive identical colors have identical thickness and winding angles;

[0052] Step 8: Based on the structure and performance parameters of the cylinder composite layer, the thickness, winding angle and material properties of the cylinder shell element are assigned as a whole;

[0053] Step 9: Optimize the shell element thickness in the transition area of ​​the head and cylinder according to the shell element thickness, such as Figure 7 As shown;

[0054] Specifically, the shell element thickness in the transition region lies between that of the head and cylinder, and decreases evenly from the cylinder to the head. Because the cylinder is wound both helically and circumferentially, the shell element thickness is much greater than that at the major diameter of the head. Therefore, based on this difference in thickness, three groups of meshes in the transition region are selected and reassigned to achieve a smooth transition in thickness.

[0055] More specifically, the finite element mesh modeling method for the composite layer of the composite gas cylinder provided in the present application establishes a finite element mesh model of the composite layer of the composite gas cylinder based on the composite mesh theory, which restores the geometric structure of the composite layer of the composite gas cylinder to the greatest extent, greatly improves the efficiency of the finite element mesh modeling of the composite layer of the composite gas cylinder, reduces the calculation error caused by mesh modeling, improves the calculation accuracy and reduces the calculation cost.

[0056] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A finite element mesh modeling method for composite layer of composite gas cylinder, characterized in that: The steps include: Step 1: Obtain the geometric model of the cylinder liner, import the geometric model into the finite element simulation software, and edit the geometric model to obtain the composite layer surface of the head and cylinder; Step 2: Divide the head and cylinder into quadrilateral shell element meshes; Step 3: Extract shell element information and node coordinates, group shell elements according to the shell element node coordinates, and select representative shell elements; Step 4: Output the four node coordinates of the representative shell element and calculate the center coordinates of the representative shell element based on the node coordinates; Step 5: Using the center coordinates of the representative shell element as input, calculate the thickness and winding angle of the representative shell element according to the composite layer structure of the head; Step 6: According to the shell element grouping information, assign the shell element thickness, winding angle and material properties of each group corresponding to each representative shell element; Step 7: Input the head shell unit mesh information into the finite element simulation software; Step 8: Based on the structure and performance parameters of the cylinder composite layer, the thickness, winding angle and material properties of the cylinder shell element are assigned as a whole; Step 9: Optimize the shell element thickness in the transition area between the head and cylinder based on the shell element thickness.

2. The finite element mesh modeling method for composite layer of composite gas cylinder according to claim 1, characterized in that: In step 1, the geometric model of the cylinder liner includes: Axisymmetric 1 / 2 or 1 / 4 3D geometric model of composite gas cylinder liner; 2D geometric model of the composite material layer of the head and barrel of a composite gas cylinder.

3. The finite element mesh modeling method for composite layer of composite gas cylinder according to claim 2, characterized in that: In step 2, the meshing of the head and cylinder quadrilateral shell elements includes the following steps: Step 2.1: Divide the cylinder head and cylinder into quadrilateral shell element meshes at 2-degree intervals along the cylinder head circumference. Step 2.2: The grids are arranged neatly along the axial direction of the cylinder head, and the axial size of the grids decreases evenly from the major diameter to the minor diameter of the cylinder head.

4. The finite element mesh modeling method for composite layer of composite gas cylinder according to claim 3 is characterized in that: In step 3, along the circumferential direction of the cylinder head, each column of shell elements is a group, and the shell element with the smallest number in each group of shell elements is the representative shell element.

5. The finite element mesh modeling method for composite layer of composite gas cylinder according to claim 4, characterized in that: In step 4, the coordinates of the representative shell element center are calculated using the following formula: Where i is the representative shell element number, xn(i, j), yn(i, j), and zn(i, j) are the coordinates of the jth node of the i-th element.

6. The finite element mesh modeling method for composite layer of composite gas cylinder according to claim 5, characterized in that: In step 5, the representative shell element thickness and winding angle are defined as functions of the shell element center coordinates.

7. The finite element mesh modeling method for composite layer of composite gas cylinder according to claim 6, characterized in that: In step 6, the thickness and winding angle of each group of shell elements are the same as the thickness and winding angle of the representative shell elements of the group.

8. The finite element mesh modeling method for composite layer of composite gas cylinder according to claim 7, characterized in that: In step 9, the thickness of the shell elements in the transition region is between the thickness of the shell elements in the head and the cylinder, and the thickness of the shell elements in the transition region decreases uniformly from the cylinder to the head.

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