A method and system for generating finite element mesh of a winding pressure vessel

Abstract

The application relates to a winding pressure container finite element grid generation method and system. The method comprises the following steps: discretizing the outer contour of a pressure container liner into uniformly distributed original discrete points and numbering; calculating the thickness value distribution on all the original discrete points according to a layering scheme; generating new contour discrete points according to the thickness value distribution, constituting a new contour after winding and numbering the new contour discrete points; generating a winding layer through a first discrete point number and a second discrete point number according to the new contour discrete points and the original discrete points, and determining the unit and unit number of the winding layer; taking the new contour discrete points as the original discrete points, returning to the step of calculating the thickness value distribution on all the original discrete points according to the layering scheme, until all the winding layers in the layering scheme are completed, and the finite element grid of the winding pressure container is generated. The application can improve the overall quality of the finite element grid.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of mesh generation, fiber-wound structure modeling simulation, in particular to a winding pressure vessel finite element mesh generation method and system. BACKGROUND

[0002] Composite gas cylinders began to be used in aerospace and military fields in the 1970s. With the transfer of military technology to civilian markets in the United States and Europe, its application fields are more extensive, such as respirators in the medical industry, natural gas pipelines in the chemical industry, and hydrogen storage cylinders in the new energy automobile field. Composite gas cylinders have greater carrying capacity and are less likely to explode than traditional metal gas cylinders, and have become a widely developed and applied direction.

[0003] High-pressure hydrogen storage cylinders are mainly used to store high-pressure gaseous hydrogen. With the current shortage of oil resources and global climate problems caused by carbon emissions, hydrogen storage cylinders have many advantages such as low cost and high safety compared to low-temperature liquid hydrogen storage and the use of hydrogen storage materials, and have been widely used in the field of new energy hydrogen fuel cell vehicles.

[0004] With the wide application of finite element simulation and the increasing demand for product quality, the design of the gas cylinder will inevitably involve the finite element checking of the gas cylinder, and the quality of the mesh often directly affects the accuracy of the finite element calculation results. The gas cylinder has a combination of longitudinal winding, hoop winding, hole expansion, and reinforcement winding methods, and the winding sequence is diverse. The general mesh generation algorithm often has poor mesh quality at the hole and equatorial positions, resulting in poor overall quality of the generated finite element mesh. SUMMARY

[0005] The purpose of the present application is to provide a winding pressure vessel finite element mesh generation method and system to solve the problem of poor overall quality of the finite element mesh generated by the general mesh generation algorithm.

[0006] To achieve the above purpose, the present application provides the following scheme:

[0007] A winding pressure vessel finite element mesh generation method, comprising:

[0008] Discretizing the outer contour of the pressure vessel liner into uniformly distributed original discrete points and numbering them to obtain the first discrete point number and the first discrete point coordinates of the original discrete points;

[0009] Calculating the thickness value distribution on all the original discrete points according to the layering scheme;

[0010] generating new profile discrete points according to the thickness value distribution, constituting a new profile after winding, numbering the new profile discrete points, obtaining second discrete point numbering and second discrete point coordinates of the new profile discrete points;

[0011] generating a winding layer according to the new profile discrete points and the original discrete points, the first discrete point numbering and the second discrete point numbering, and determining units and unit numbering of the winding layer;

[0012] returning to the step of calculating the thickness value distribution on all the original discrete points according to the layup scheme, taking the new profile discrete points as the original discrete points, until all the winding layers in the layup scheme are completed, and generating a finite element mesh of the wound pressure vessel; the finite element mesh includes unit numbering, discrete point numbering and discrete point coordinates of each winding layer; and the finite element mesh is used for simulating the pressure vessel.

[0013] Optionally, the step of calculating the thickness value distribution on all the original discrete points according to the layup scheme specifically includes:

[0014] determining boundary conditions according to the fiber winding forming process principle;

[0015] establishing a differential equation according to the boundary conditions, and calculating coefficients of a cubic spline formula;

[0016] determining the cubic spline formula according to the coefficients of the cubic spline formula;

[0017] predicting the thickness value distribution on all the original discrete points according to the layup scheme and the cubic spline formula.

[0018] Optionally, the boundary conditions specifically include that the number of yarn sheets at the pole hole position is equal to the number of segments of the cylinder body, the thickness at a position twice the width of the pole hole is equal to a function value of the cubic spline formula, the derivative of the thickness at twice the width is equal to a derivative value of the cubic spline formula, and the fiber volume content within twice the width is constant.

[0019] Optionally, the differential equation is:

[0020]

[0021]

[0022] wherein m1, m2, m3 and m4 are coefficients of the cubic spline formula; r is an integrand, r0 is a radius of the pole hole; r 2b is a parallel circle radius away from twice the width of the pole hole; t R = 2xt p is a thickness of the cylinder body after a complete winding cycle of the fiber winding layer; t pis the thickness of a single layer of fiber winding layer at the barrel; R is the barrel radius; α0 is the barrel winding angle; m0 represents the number of yarn sheets at the pole hole position; b is the winding bandwidth; m R is the number of yarn sheets of fiber in the barrel section; n R is the number of spiral winding layers of the cylinder; V const r is the volume of the yarn bundle space within twice the bandwidth; b It is the radius of the parallel circle at a distance of one times the bandwidth from the polar hole.

[0023] Optionally, the cubic spline formula is:

[0024]

[0025] Among them, t f (r i ) is the radius r i The thickness at r i is the radius of the parallel circle at the thickness position to be determined at the head.

[0026] Optionally, generating new contour discrete points according to the thickness value distribution to form a new contour after winding and numbering the new contour discrete points to obtain second discrete point numbers and second discrete point coordinates of the new contour discrete points specifically includes:

[0027] The new contour discrete points are numbered from left to right, and the numbering rule is a circular thickness value array. If the thickness value of the new contour discrete point is 0, the number of the new contour discrete point corresponding to the thickness value of the new contour discrete point is determined using the number of the corresponding discrete point of the previous contour layer, generating a second discrete point number and obtaining the coordinates of the second discrete point;

[0028] If the thickness value of the new contour discrete point is not 0, the value of 1000×the winding layer serial number+the new contour discrete point serial number is used as the second discrete point number, and the coordinates of the second discrete point are obtained.

[0029] A finite element mesh generation system for a wound pressure vessel, comprising:

[0030] a first discrete point numbering and first discrete point coordinate determination module, configured to discretize the outer contour of the pressure vessel liner into uniformly distributed original discrete points and number them, thereby obtaining first discrete point numbers and first discrete point coordinates of the original discrete points;

[0031] A thickness value distribution calculation module is used to calculate the thickness value distribution of all the original discrete points according to the ply plan;

[0032] The second discrete point number and the second discrete point coordinate determination module is configured to generate new profile discrete points according to the thickness value distribution, constitute a new profile after winding, and number the new profile discrete points to obtain second discrete point numbers and second discrete point coordinates of the new profile discrete points.

[0033] The winding layer generation module is configured to generate a winding layer according to the new profile discrete points and the original discrete points, and determine units and unit numbers of the winding layer by using the first discrete point numbers and the second discrete point numbers.

[0034] The finite element mesh generation module of the pressure vessel is configured to return to the step of calculating the thickness value distribution on all the original discrete points according to the layering scheme with the new profile discrete points as the original discrete points until all the winding layers in the layering scheme are completed, and generate a finite element mesh of the wound pressure vessel. The finite element mesh includes unit numbers, discrete point numbers and discrete point coordinates of each winding layer, and is used for simulating the pressure vessel.

[0035] Optionally, the thickness value distribution calculation module specifically includes:

[0036] The boundary condition determination unit is configured to determine boundary conditions according to the principle of the fiber winding forming process.

[0037] The coefficient calculation unit of the cubic spline formula is configured to establish a differential equation according to the boundary conditions, and calculate coefficients of the cubic spline formula.

[0038] The cubic spline formula determination unit is configured to determine the cubic spline formula according to the coefficients of the cubic spline formula.

[0039] The thickness value distribution calculation unit is configured to predict the thickness value distribution on all the original discrete points by using the cubic spline formula according to the layering scheme.

[0040] Optionally, the boundary conditions specifically include that the number of yarn sheets at the pole hole position is equal to the number of segments of the barrel body, the thickness at a position twice the width of the pole hole is equal to a function value of the cubic spline formula, the derivative of the thickness at the twice-width position is equal to a derivative value of the cubic spline formula, and the fiber volume content within the twice-width is constant.

[0041] Optionally, the differential equation is:

[0042]

[0043]

[0044] wherein m1, m2, m3 and m4 are coefficients of the cubic spline formula, r is an integrand, r0 is a radius of a pole hole, and r1 is a radius of a twice-width position.2b is the parallel garden radius away from the pole hole twice the bandwidth; t R = 2 x t p is the thickness of the fiber winding layer at the barrel after winding a complete cycle; t p is the single layer thickness of the fiber winding layer at the barrel; R is the barrel radius; a0 is the winding angle of the barrel section; m0 represents the number of yarn sheets at the pole hole position; b is the winding bandwidth; m R is the number of yarn sheets of the fiber of the barrel section; n R is the number of spiral winding layers of the barrel; V const is the yarn bundle space volume within the twice bandwidth.

[0045] According to the specific embodiments provided by the application, the following technical effects are disclosed: the application provides a winding pressure vessel finite element grid generation method and system, which discretizes a continuous model into a model spliced by multiple polygons, that is, a winding layer is generated through the discrete point numbering of two layers of contours, and the units and unit numbers of the winding layer are determined. Compared with the traditional method, the finite element grid generation method of the application is more uniform in discretization, and the generated grid quality is better. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0047] Figure 1 is the finite element grid generation method flowchart of the winding pressure vessel provided by the application;

[0048] Figure 2 is the finite element grid generation method flowchart of the gas cylinder composite winding layer model provided by the application;

[0049] Figure 3 is the gas cylinder model schematic diagram provided by the application;

[0050] Figure 4 is the partial discrete points and their numbering schematic diagram of the outer contour of the inner liner and the next layer of new contour provided by the application;

[0051] Figure 5 is the gas cylinder grid model diagram provided by the application;

[0052] Figure 6 is the finite element grid schematic diagram of the pressure vessel generated by the application;

[0053] Figure 7A schematic diagram of a finite element mesh for a pressure vessel generated using a conventional generation algorithm;

[0054] Figure 8 A structure diagram of a winding pressure vessel finite element mesh generation system provided by the present application. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0056] The purpose of the present application is to provide a winding pressure vessel finite element mesh generation method and system to improve the quality of the finite element mesh.

[0057] In order to make the above-mentioned purposes, characteristics and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0058] Figure 1 A flow chart of a winding pressure vessel finite element mesh generation method provided by the present application, as shown in Figure 1 The winding pressure vessel finite element mesh generation method comprises the following steps.

[0059] Step 101: Discretize the outer contour of the pressure vessel liner into uniformly distributed original discrete points and number them to obtain the first discrete point number and the first discrete point coordinates of the original discrete points.

[0060] The outer contour of the pressure vessel liner is divided into three parts, i.e. left head, cylinder and right head, and discretized into a group of uniformly distributed discrete points, and the number of discrete points is required to be less than 1000.

[0061] The discrete points of the outer contour of the liner are numbered from left to right, starting from 1, and the first discrete point number and the corresponding first discrete point coordinates are stored.

[0062] Step 102: Calculate the thickness value distribution on all the original discrete points according to the layering scheme. The layering scheme is a winding process scheme. Generally, there are various winding methods for fiber winding composites, such as spiral winding and hoop winding, and the winding process scheme is an ordered combination of various winding methods. For example, according to the winding structure parameters and internal pressure load parameters, 4 layers of spiral winding layers and 3 layers of hoop winding layers are calculated, and the ordering combination thereof according to the process conditions is the winding process scheme.

[0063] The step 102 specifically comprises: determining boundary conditions according to the principle of fiber winding forming process; establishing a differential equation according to the boundary conditions, calculating the coefficients of the cubic spline formula; determining the cubic spline formula according to the coefficients of the cubic spline formula; and predicting the thickness value distribution on all the original discrete points by using the cubic spline formula according to the layup scheme.

[0064] The boundary conditions specifically comprise: the number of yarn sheets at the pole hole position is equal to the number of segments of the barrel, the thickness at the position twice the width of the pole hole is equal to the function value of the cubic spline formula, the derivative of the thickness at twice the width is equal to the derivative value of the cubic spline formula, and the fiber volume content within twice the width is constant.

[0065] The differential equation is:

[0066]

[0067]

[0068] wherein m1, m2, m3 and m4 are the coefficients of the cubic spline formula; r is the integral quantity, and the integral range is r0 to r 2b ; r0 is the radius of the pole hole; r 2b is the parallel circle radius away from the position twice the width of the pole hole; t R = 2xt p is the thickness of the barrel at the complete winding cycle of the fiber winding layer; t p is the single layer thickness of the fiber winding layer at the barrel; R is the barrel radius; a0 is the winding angle of the barrel segment; m0 represents the number of yarn sheets at the pole hole position; b is the winding width; m R is the number of yarn sheets of the fiber at the barrel segment; n R is the number of spiral winding layers of the barrel; V const is the space volume of the yarn bundle within twice the width; r b is the parallel circle radius at the position one width away from the pole hole.

[0069] The cubic spline formula is:

[0070]

[0071] wherein t f (r i ) is the thickness at the radius r i ; r i is the parallel circle radius at the position of the thickness to be solved at the head.

[0072] The thickness values of the original discrete points on the outer contour of the liner are calculated by the cubic spline formula and stored. The thickness values of the original discrete points on the contour parts not wound during the reaming winding and the hoop winding are set to zero.

[0073] Step 103: generating new profile discrete points according to the thickness value distribution, constituting a new profile after winding, and numbering the new profile discrete points to obtain second discrete point numbering and second discrete point coordinates of the new profile discrete points.

[0074] The step 103 specifically comprises: numbering the new profile discrete points from left to right, the numbering rule being a circulating thickness value array, if the thickness value of the new profile discrete point is 0, using the numbering of the corresponding discrete point of the last profile to determine the numbering of the new profile discrete point corresponding to the thickness value of the new profile discrete point, generating second discrete point numbering and obtaining second discrete point coordinates; if the thickness value of the new profile discrete point is not 0, taking the value of 1000 x winding layer number + new profile discrete point number as the second discrete point numbering, and obtaining the second discrete point coordinates.

[0075] According to whether the thickness value of the discrete point of the inner liner outer profile is zero, if the thickness value is zero, the second discrete point numbering of the corresponding new profile is the same as the first discrete point numbering of the inner liner outer profile, if the thickness is not zero, the second discrete point numbering is the value of the first discrete point numbering of the corresponding inner profile plus 1000, the second discrete point numbering of the new profile and the corresponding second discrete point coordinates are stored.

[0076] Step 104: generating a winding layer according to the new profile discrete points and the original discrete points, the first discrete point numbering and the second discrete point numbering, and determining the unit and unit numbering of the winding layer.

[0077] Step 105: taking the new profile discrete points as the original discrete points, returning to step 102, until all winding layers in the layup scheme are completed, generating a finite element mesh of the wound pressure vessel; the finite element mesh comprises the unit numbering, discrete point numbering and discrete point coordinates of each winding layer; the finite element mesh is used for simulating the pressure vessel.

[0078] Repeat steps 102-104 to calculate the thickness of the outer profile, update the profile, and number the new discrete points until all the layups are cycled, at which time the discrete point numbering and coordinates of each layer profile, and the discrete point thickness value array of each layer are obtained.

[0079] Output the node numbering and its coordinates to the data input file of the finite element software, for example, output to the inp file in ABAQUS.

[0080] The format is: node number X-axis coordinate Y-axis coordinate.

[0081] Output the unit numbering and the node numbering consisting of the unit to the data input file of the finite element software, for example, output to the inp file in ABAQUS.

[0082] Format: unit number node1 node2 node3 node4.

[0083] In order to accurately find the nodes forming the unit and connect counterclockwise, starting from the number array of the first layer of contour points, traverse the whole array from left to right, if the value of the corresponding thickness array is zero, skip, if not, record the number, record it as A, extract the index IA of A in the current array, open the number array of the next layer of contour points and find the value at the index IA position, that is, the node number B corresponding to the second layer of contour corresponding position is obtained, and the four nodes of the unit are formed counterclockwise, that is, A, A+1, B+1, B. Repeat the traversal of the third, fourth and last layer, and the composition node number of all units is obtained.

[0084] Taking a gas cylinder as an example, help is provided for accurate and rapid finite element modeling and simulation of the gas cylinder.

[0085] The composite gas cylinder is formed by winding carbon fibers on a plastic liner with sealing and certain strength, wherein the carbon fiber reinforced composite material has many advantages such as high specific strength and high specific stiffness, and designability of material performance, etc., which provides strength for the gas cylinder and ensures that the gas cylinder meets the design load requirement.

[0086] As shown in Figure 2 , the application of the present application to the generation of finite element grid of high-quality gas cylinder composite winding layer model is applied, which specifically includes the following steps:

[0087] S1: Discretize the contour of the gas cylinder liner into a series of uniformly distributed points and number them. The gas cylinder model is as shown in Figure 3 , wherein 1 is the left joint, 2 is the liner, 3 is the composite winding layer, and 4 is the right joint.

[0088] As shown in Figure 4 , the discrete points are numbered from left to right, starting from 1, and the first discrete point number and its first discrete point coordinates of the original discrete points are output to the inp file for saving.

[0089] And in order to start the next layer number from 1001, the discrete points of the whole contour cannot exceed 1000, if the model is too large, the next layer number starts from 10001.

[0090] S2: Calculate the thickness of all discrete points on the contour according to the layup scheme and store it.

[0091] According to the layup scheme, the thickness distribution of the first winding layer on the discrete points of the liner contour is predicted using cubic spline method, and the cubic spline formula is:

[0092]

[0093] In the formula, mi (i = 1, 2, 3, 4) are the coefficients of the cubic spline formula, in order to solve the coefficients need to be established according to the boundary conditions of differential equations for solving, according to the principle of fiber winding forming process, the following boundary conditions can be obtained as shown below:

[0094] ① The number of yarn sheets at the position of the extreme hole is equal to that of the barrel section.

[0095] ② The thickness at the position of twice the width from the extreme hole is equal to the function value of the cubic spline formula.

[0096] ③ In order to ensure the smooth and continuous profile of the curve at the head, the derivative of the thickness at the position of twice the width from the extreme hole is equal to the derivative value of the cubic spline formula.

[0097] ④ The fiber volume content within twice the width from the extreme hole is constant.

[0098] Substituting the above four boundary conditions into the above formula can obtain the solving formula of the coefficients of the cubic spline formula as shown below:

[0099]

[0100]

[0101] In the formula, m1, m2, m3 and m4 are the coefficients of the cubic spline formula; r is the integral quantity; r0 is the radius of the extreme hole; r 2b is the parallel circle radius away from the position of twice the width from the extreme hole; t R = 2xt p is the thickness of the barrel at the complete winding cycle of the fiber winding layer; t p is the single layer thickness of the fiber winding layer at the barrel; R is the radius of the barrel; a0 is the winding angle of the barrel section; m0 represents the number of yarn sheets at the position of the extreme hole; b is the winding width; m R is the number of yarn sheets of the fiber at the barrel section; n R is the number of spiral winding layers of the barrel; V const is the space volume of the yarn bundle within twice the width; r b is the parallel circle radius at the position of one width from the extreme hole.

[0102] The thickness values corresponding to the original discrete points on the outer profile of the liner are calculated by the cubic spline formula and stored.

[0103] It should be noted that if this winding layer is circumferential winding, expanding hole winding or reinforcement, the thickness of the discrete points of the unwound part is set to 0, and the length of the thickness value array is equal to the number of discrete points.

[0104] S3: According to the thickness value distribution on the discrete points of the inner profile, new profile discrete points are generated in the original profile normal direction by the thickness value, to form the new profile after winding.

[0105] The new discrete points are numbered from left to right, and the numbering rule is the thickness value array, if the thickness value is zero, the second discrete point number of the corresponding discrete point uses the corresponding discrete point number of the last profile, if the thickness is not 0, the second discrete point number is 1000*the winding layer number + the discrete point number. In this way, it can be ensured that the numbering of the discrete points in the thickness direction is different only in the thousands, and the values of the hundreds, tens and individual bits are all the same, as shown in Figure 4 、 Figure 5 The second discrete point number of the new discrete point and the coordinates are output to the inp file for storage.

[0106] S4: obtaining the unit forming the winding layer from the new profile discrete point and the original profile discrete point.

[0107] The thickness value array is cycled, if the thickness value is not zero, the index of the value is extracted, and then the corresponding value of the new profile array is obtained through the index, that is, the number of the profile point, in this example, the first profile discrete point with a non-zero thickness value is numbered as 1, so it can be easily known that the four points 1, 2, 1002 and 1001 can form a unit, and the unit number is counted as 1 (that is, “1” in the hatched background in Figure 4 The thickness array is continued to be cycled, and all units in the winding layer are obtained. The unit number and the node numbers constituting the unit are output to the inp file for storage.

[0108] It should be noted that for the hole expansion, the ring and the reinforcing winding, as shown in Figure 5 , 1063, 2063, 1062 form a triangular unit, and as long as a conditional judgment statement is added when the first non-zero thickness value appears, the nodes forming the triangular unit can be found.

[0109] It can be seen that the essence of the present application is to discretize a continuous model into a model spliced by multiple quadrilaterals, and a unit of a winding layer is composed of three or four discrete points as corner points. When a unit of a winding layer is composed of four discrete points, two discrete points are on the last profile, and the other two discrete points are on the new profile. When a unit of a winding layer is composed of three discrete points, two discrete points are on the last profile, and one discrete point is on the new profile.

[0110] The finite element mesh generation method of the present application is more uniform in discretization, and the generated mesh is better in quality.

[0111] S5: cycling S2, S3 and S4, until all the plies are cycled, and a series of node numbers and coordinate values, unit numbers and nodes constituting the unit are obtained.

[0112] As shown in Figure 6 、 Figure 7The present application is more in line with the winding rule, that is, the profile of the new winding layer is formed by increasing the thickness on the basis of the last winding layer, skips the traditional finite element geometric modeling process, and the mesh generation speed is faster.

[0113] Compared with the traditional finite element simulation modeling method of the gas cylinder, the present application can not only provide more regular gas cylinder structure units for simulation, but also more accurate winding angles defined in the unit, thereby improving the accuracy of the finite element simulation of the gas cylinder and providing accurate simulation structure for the design of the gas cylinder; in addition, the present application has strong universality and can create high-quality axisymmetric element mesh and three-dimensional solid element mesh for all winding structures.

[0114] Figure 8 The structure diagram of the winding pressure vessel finite element mesh generation system provided by the present application is shown as Figure 8 The winding pressure vessel finite element mesh generation system comprises:

[0115] The first discrete point number and the first discrete point coordinate determination module 801 is used for dispersing the outer profile of the pressure vessel liner into uniformly distributed original discrete points and numbering, obtaining the first discrete point number and the first discrete point coordinates of the original discrete points.

[0116] The thickness value distribution calculation module 802 is used for calculating the thickness value distribution of all the original discrete points according to the layer scheme.

[0117] The thickness value distribution calculation module 802 specifically comprises: a boundary condition determination unit, which is used for determining the boundary condition according to the fiber winding forming process principle; a coefficient calculation unit of cubic spline formula, which is used for establishing a differential equation according to the boundary condition and calculating the coefficient of the cubic spline formula; a cubic spline formula determination unit, which is used for determining the cubic spline formula according to the coefficient of the cubic spline formula; and a thickness value distribution calculation unit, which is used for predicting the thickness value distribution of all the original discrete points according to the layer scheme and using the cubic spline formula.

[0118] The boundary condition specifically comprises: the number of yarn sheets at the pole hole position is equal to the number of segments of the cylinder body, the thickness at the position twice the width away from the pole hole is equal to the function value of the cubic spline formula, the derivative of the thickness at the twice width is equal to the derivative value of the cubic spline formula, and the fiber volume content within the twice width is constant.

[0119] The differential equation is:

[0120]

[0121]

[0122] Wherein, m1, m2, m3 and m4 are coefficients of cubic spline formula; r is the integral quantity; r0 is the radius of the parallel circle far from the pole hole; r 2b is the radius of the parallel circle at the position of double bandwidth far from the pole hole; t R = 2xt p is the thickness of the cylinder body after a complete winding cycle of the fiber winding layer; t p is the thickness of a single layer of the fiber winding layer at the cylinder body; R is the radius of the cylinder body; a0 is the winding angle of the cylinder body section; m0 represents the number of yarn sheets at the position of the pole hole; b is the winding bandwidth; m R is the number of yarn sheets of the fiber at the cylinder body section; n R is the number of spiral winding layers of the cylinder body; V const is the volume of the yarn bundle space within the double bandwidth; r b is the radius of the parallel circle at the position of single bandwidth far from the pole hole.

[0123] The boundary conditions provided by the application can obviously improve the grid quality at the pole hole and the equator position, and further improve the overall quality of the generated finite element grid.

[0124] The second discrete point numbering and coordinate determination module 803 is configured to generate new profile discrete points according to the thickness value distribution, number the new profile discrete points, and obtain second discrete point numbering and second discrete point coordinates of the new profile discrete points.

[0125] The winding layer generation module 804 is configured to generate a winding layer according to the new profile discrete points and the original discrete points, and determine the unit and unit number of the winding layer by using the first discrete point numbering and the second discrete point numbering.

[0126] The finite element grid generation module 805 of the pressure vessel is configured to return to the step of calculating the thickness value distribution at all the original discrete points according to the winding layer scheme, with the new profile discrete points as the original discrete points, until all the winding layers in the winding layer scheme are completed, and generate a finite element grid of the wound pressure vessel; the finite element grid comprises the unit number, discrete point number and discrete point coordinates of each winding layer; and the finite element grid is used for simulating the pressure vessel.

[0127] The application can improve the overall quality of the finite element grid.

[0128] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts of each embodiment can be referred to each other. For the system disclosed in the embodiments, the description is relatively simple because it corresponds to the method disclosed in the embodiments, and the relevant parts can be referred to the method part.

[0129] The principles and implementations of the present application are described in the specific examples, and the above examples are only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation and application range will be changed. In view of the above, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A finite element mesh generation method for a wound pressure vessel, characterized in that: The method comprises the following steps: discretize the outer contour of the pressure vessel liner into uniformly distributed original discrete points and number them to obtain first discrete point numbering and first discrete point coordinates of the original discrete points; calculate thickness value distribution on all the original discrete points according to the layering scheme, specifically comprising: determine boundary conditions according to the principle of fiber winding forming process; the boundary conditions specifically include: the number of yarn sheets at the extreme hole position is equal to the number of segments of the barrel body, the thickness at the position twice the width away from the extreme hole is equal to the function value of the cubic spline formula, the derivative of the thickness at twice the width is equal to the derivative value of the cubic spline formula, and the fiber volume content within twice the width is constant; establish a differential equation according to the boundary conditions to calculate the coefficients of the cubic spline formula; the differential equation is: wherein m1, m2, m3 and m4 are coefficients of the cubic spline formula; r is the integral quantity; r0 is the radius of the parallel circle at the pole hole; r 2b is the radius of the parallel circle at twice the pole hole distance; t R = 2xt p is the thickness of the cylinder at the pole hole; t p is the thickness of the fiber winding layer at the pole hole; R is the radius of the cylinder; a0 is the winding angle of the cylinder section; m0 is the number of yarn sheets at the pole hole; b is the winding width; m R is the number of yarn sheets of the fiber of the cylinder section; n R is the number of spiral winding layers of the cylinder; V const is the volume of the yarn bundle space within twice the width; r b is the radius of the parallel circle at the pole hole; determine the cubic spline formula according to the coefficients of the cubic spline formula; predict the thickness value distribution on all the original discrete points by using the cubic spline formula according to the layering scheme; generate new contour discrete points according to the thickness value distribution to form a new contour after winding and number the new contour discrete points to obtain second discrete point numbering and second discrete point coordinates of the new contour discrete points; generate a winding layer by the first discrete point numbering and the second discrete point numbering according to the new contour discrete points and the original discrete points, and determine the unit and unit numbering of the winding layer; return to the step of calculating the thickness value distribution on all the original discrete points according to the layering scheme with the new contour discrete points as the original discrete points until all the winding layers in the layering scheme are completed to generate a finite element mesh of the wound pressure vessel; the finite element mesh comprises the unit numbering, discrete point numbering and discrete point coordinates of each winding layer; and the finite element mesh is used for simulating the pressure vessel.

2. The method of claim 1, wherein, The cubic spline formula is: where t f (r i ) is the thickness at radius r i ; and r i is the parallel circle radius at the location of the thickness to be found at the head.

3. The method of claim 2, wherein, The step of generating new contour discrete points according to the thickness value distribution to form a new contour after winding and numbering the new contour discrete points to obtain second discrete point numbering and second discrete point coordinates of the new contour discrete points specifically comprises: number the new contour discrete points from left to right according to the cyclic thickness value array; if the thickness value of the new contour discrete point is 0, the numbering of the new contour discrete point corresponding to the thickness value of the new contour discrete point is determined by using the numbering of the corresponding discrete point of the last layer contour to generate second discrete point numbering and obtain second discrete point coordinates; if the thickness value of the new contour discrete point is not 0, the value of 1000* winding layer number + new contour discrete point number is used as the second discrete point numbering, and the second discrete point coordinates are obtained.

4. A system for generating finite element meshes for winding pressure vessels, characterized in that, The method comprises the following steps: a first discrete point numbering and first discrete point coordinate determination module is configured to discretize the outer contour of the pressure vessel liner into uniformly distributed original discrete points and number them to obtain first discrete point numbering and first discrete point coordinates of the original discrete points; a thickness value distribution calculation module is configured to calculate thickness value distribution on all the original discrete points according to the layering scheme; the thickness value distribution calculation module specifically comprises: The boundary condition determining unit is configured to determine boundary conditions according to the principle of the filament winding forming process. The boundary conditions specifically include that the number of yarn sheets at the pole hole position is equal to the number of segments of the barrel body, the thickness at a position twice the bandwidth away from the pole hole is equal to a function value of a cubic spline formula, the derivative of the thickness at the twice bandwidth position is equal to a derivative value of the cubic spline formula, and the fiber volume content within the twice bandwidth is constant. The coefficient calculating unit of the cubic spline formula is configured to establish a differential equation according to the boundary conditions, and calculate coefficients of the cubic spline formula. The differential equation is as follows: wherein m1, m2, m3 and m4 are coefficients of the cubic spline formula; r is the integrand; r0 is the radius of the polar hole; r 2b is the radius of the parallel circle at a distance of twice the band width from the polar hole; t R = 2xt p is the thickness of the cylinder at the position of the complete winding of the fiber winding layer; t p is the thickness of a single layer of the fiber winding layer at the cylinder; R is the radius of the cylinder; a0 is the winding angle of the cylinder section; m0 is the number of yarn sheets at the position of the polar hole; b is the winding band width; m R is the number of yarn sheets of the fiber of the cylinder section; n R is the number of layers of the helical winding of the cylinder; V const is the volume of the space of the yarn bundle within the double band width; r b is the radius of the parallel circle at a distance of one band width from the polar hole; The cubic spline formula determining unit is configured to determine the cubic spline formula according to the coefficients of the cubic spline formula. The thickness value distribution calculating unit is configured to predict the thickness value distribution at all the original discrete points by using the cubic spline formula according to the layup scheme. The second discrete point numbering and second discrete point coordinate determining module is configured to generate new profile discrete points according to the thickness value distribution, form a new profile after winding, number the new profile discrete points, and obtain second discrete point numbering and second discrete point coordinates of the new profile discrete points. The winding layer generating module is configured to generate a winding layer by using the first discrete point numbering and the second discrete point numbering according to the new profile discrete points and the original discrete points, and determine the unit and unit numbering of the winding layer. The finite element mesh generating module of the pressure vessel is configured to return to the step of calculating the thickness value distribution at all the original discrete points according to the layup scheme by using the new profile discrete points as the original discrete points, until all the winding layers in the layup scheme are completed, and generate a finite element mesh of the wound pressure vessel. The finite element mesh includes unit numbering, discrete point numbering and discrete point coordinates of each winding layer. The finite element mesh is used to simulate the pressure vessel.

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