Thickness prediction method and system for winding composite material pressure vessel end socket

Abstract

The invention discloses a thickness prediction method and system for winding a composite material pressure vessel end socket, and belongs to the technical field of simulation modeling. The method comprises the steps that the surface of a core mold of the oval end socket of the composite material pressure container serves as a galloon winding face of a first winding layer, and the first winding layer serves as a current winding layer; determining a left boundary and a right boundary of the galloon; determining second scatter points corresponding to the first scatter points on the galloon winding surface by utilizing the left boundary and the right boundary of the galloon so as to form a new galloon winding surface; judging whether the current winding layer is the last winding layer or not, and if yes, ending; and if not, taking the new galloon winding surface as the galloon winding surface of the next winding layer of the current winding layer, taking the next winding layer as the current winding layer, and returning to the step S2. According to the method, the thickness characteristics of the end socket of the wound composite material pressure vessel can be reflected more accurately during simulation modeling, and more refined modeling of the pressure vessel is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of simulation modeling, and in particular relates to a thickness prediction method and system for a wound composite pressure vessel head. Background Art

[0002] Compared to metal pressure vessels, composite pressure vessels offer higher strength, a lighter design, and superior corrosion resistance, and are increasingly being used in aerospace, hydrogen storage, and transportation, among other technical fields. With the development of winding manufacturing and computer technology, the finite element method (FEM) has become one of the primary methods for optimizing the strength design of pressure vessels. However, when the tape is wrapped around the head of the pressure vessel, not only does the winding angle change, but it also accumulates around the pole hole. Furthermore, the tape may become suspended or slip during the manufacturing process. These issues pose significant challenges to obtaining an accurate finite element simulation model of the pressure vessel, particularly the contours of the head area.

[0003] The profile of the pressure vessel head region is influenced by multiple factors, including the winding trajectory, the cross-sectional shape of the yarn, and the core mold profile. To date, numerous theoretical calculation methods for predicting the pressure vessel head profile have been developed, and these methods are constantly being further developed and refined. The classic single-formula method, proposed in 1963, laid the foundation for head profile prediction. However, the thickness predicted by this method tends to infinity near the bore. In 1971, the Knoell equation was developed, using two formulas to calculate the two parts of the head profile, using one-time bandwidth as the boundary. This prevents the thickness prediction near the bore from tending to infinity. In recent years, the dual-formula method has been further developed. Although the prediction accuracy of the head profile has improved, the peak at one-time bandwidth does not match the actual product. Wang et al. further considered the continuity of the first-order derivative of the prediction formula based on the dual-formula method and smoothed the predicted head profile through cubic spline curve fitting. Although many methods have been developed to predict the variable thickness head of a pressure vessel, these methods either do not consider the influence of the previous layer of yarn on the surface shape of the head after winding, or directly project the ellipsoidal pressure vessel head along the axial direction without considering the three-dimensional winding shape of the yarn after each layer of winding. In addition, there are burrs on the surface of the yarn after each layer of winding, which reduces the thickness prediction result of the pressure vessel head and cannot achieve more refined modeling of the pressure vessel. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a thickness prediction method for a wound composite pressure vessel head. This method can more accurately reflect the thickness characteristics of the wound composite pressure vessel head during simulation modeling, ensure the thickness prediction results of the pressure vessel head, and is suitable for more refined modeling of pressure vessels.

[0005] A second object of the present invention is to provide a thickness prediction system for wound composite pressure vessel heads.

[0006] In order to achieve one of the above purposes, the present invention adopts the following technical solutions:

[0007] A thickness prediction method for a wound composite pressure vessel head, the thickness prediction method comprising:

[0008] Step S1: using the core mold surface of the elliptical head of the composite pressure vessel as the yarn winding surface of the first winding layer, and using the first winding layer as the current winding layer;

[0009] Step S2: determining the left and right boundaries of the yarn on the current winding layer by using the rotation axis of the yarn winding surface of the current winding layer and the polar hole direction of the elliptical head of the composite pressure vessel;

[0010] Step S3: using the left boundary and the right boundary of the tape on the current winding layer, determining second scattered points corresponding to the first scattered points on the tape winding surface of the current winding layer to form a new tape winding surface;

[0011] Step S4, determine whether the current winding layer is the last winding layer. If so, use the new tape winding surface as the outermost contour of the elliptical head of the composite pressure vessel, and end; if not, use the new tape winding surface as the tape winding surface of the next winding layer of the current winding layer, and use the next winding layer as the current winding layer, and return to step S2.

[0012] Furthermore, in step S2, when the current winding layer is the first winding layer, the specific process of determining the left boundary and the right boundary of the yarn tape on the current winding layer includes:

[0013] Step S211: aligning the rotation axis of the elliptical head of the composite pressure vessel with the Z axis of the cylindrical coordinate system, setting the direction from the equator to the polar hole as the positive direction, and constructing a cylindrical coordinate system to determine the tape winding trajectory of the current winding layer on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system;

[0014] Step S212: performing a Cartesian coordinate transformation on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system to calculate an equivalent point on the equivalent sphere of each third scattered point on the winding trajectory of the yarn on the current winding layer;

[0015] Step S213: Calculate the shortest distance between two equivalent points on the equivalent sphere using the yarn width to determine the left and right boundaries of the yarn of the current winding layer;

[0016] Furthermore, in step S2, when the current winding layer is not the first winding layer, the specific process of determining the left boundary and the right boundary of the yarn tape on the current winding layer includes:

[0017] Step S221: performing discrete processing on the tape winding surface on the current winding layer to obtain the tape winding trajectory on the current winding layer;

[0018] Step S222: using the differential relationship between two adjacent fifth scattered points, solving the coordinates of each fifth scattered point on the winding trajectory of the tape on the current winding layer to determine the left boundary and the right boundary of the tape on the winding layer.

[0019] Furthermore, in step S3, the specific process of forming a new tape winding surface includes:

[0020] Step S31, using the left boundary and the right boundary of the yarn on the current winding layer, calculating the thickness value of each first scattered point on the yarn winding surface;

[0021] Step S32, obtaining perpendicular lines of tangents of the ribbon winding surface at each first scattered point on the meridian plane;

[0022] Step S33, increasing the thickness value at each first scattered point on the tape winding surface along the perpendicular direction of the corresponding first scattered point to obtain a second scattered point corresponding to each first scattered point on the tape winding surface;

[0023] Step S34: Fit the second scattered points and connect them with line segments to form a new yarn winding surface.

[0024] Furthermore, in step S31, the thickness value at each first scattered point on the winding surface of the ribbon is:

[0025]

[0026] in, is the thickness of the first scattered point j″ on the winding surface of the yarn on the i-th winding layer; n b is the number of times the ribbon passes through the equator when it completely wraps the equator; θ i′,j″ t is the central angle occupied by the intersection of the yarn at the j″th first scattered point on the i-th winding layer and the parallel circle on the vertical line; b is the thickness of the gauze.

[0027] In order to achieve the second of the above objectives, the present invention adopts the following technical solutions:

[0028] A thickness prediction system for a wound composite pressure vessel head, the thickness prediction system comprising:

[0029] As a module, it is used to use the core mold surface of the elliptical head of the composite pressure vessel as the yarn winding surface of the first winding layer, and use the first winding layer as the current winding layer;

[0030] a determination module, configured to determine the left and right boundaries of the yarn on the current winding layer by using the rotation axis of the yarn winding surface of the current winding layer and the polar hole direction of the elliptical head of the composite pressure vessel;

[0031] a forming module, configured to determine, by using the left boundary and the right boundary of the tape on the current winding layer, second scattered points corresponding to the first scattered points on the tape winding surface of the current winding layer, so as to form a new tape winding surface;

[0032] The judgment module is used to judge whether the current winding layer is the last winding layer. If so, the new yarn tape winding surface is used as the outermost contour of the elliptical head of the composite pressure vessel, and the process ends; if not, the new yarn tape winding surface is used as the yarn tape winding surface of the next winding layer of the current winding layer, and the next winding layer is used as the current winding layer, and transmitted to the determination module.

[0033] Further, when the current winding layer is the first winding layer, the determining module includes:

[0034] A construction submodule is used to coincide the rotation axis of the elliptical head of the composite pressure vessel with the Z axis of the cylindrical coordinate system, set the direction from the equator to the polar hole as the positive direction, and construct a cylindrical coordinate system to determine the yarn winding trajectory of the current winding layer on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system;

[0035] a conversion submodule, configured to perform Cartesian coordinate conversion on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system, so as to calculate an equivalent point on the equivalent sphere of each third scattered point on the winding trajectory of the yarn on the current winding layer;

[0036] The first calculation submodule is configured to calculate the shortest distance between two equivalent points on the equivalent sphere using the width of the yarn tape, so as to determine the left boundary and the right boundary of the yarn tape of the current winding layer.

[0037] Furthermore, when the current winding layer is not the first winding layer, the determining module includes:

[0038] a discrete processing submodule, configured to perform discrete processing on the tape winding surface on the current winding layer to obtain the tape winding trajectory on the current winding layer;

[0039] The solving submodule is used to solve the coordinates of each fifth scattered point on the winding trajectory of the tape on the current winding layer by using the differential relationship between two adjacent fifth scattered points to determine the left boundary and the right boundary of the tape on the winding layer.

[0040] Furthermore, the forming module includes:

[0041] A second calculation submodule is configured to calculate the thickness value of each first scattered point on the winding surface of the yarn tape by using the left boundary and the right boundary of the yarn tape on the current winding layer;

[0042] An acquisition submodule, configured to acquire a perpendicular line of a tangent line of the ribbon winding surface at each first scattered point on the meridian plane;

[0043] An adding submodule, configured to increase the thickness value at each first scattered point on the tape winding surface along a perpendicular direction corresponding to the first scattered point, to obtain second scattered points corresponding to each first scattered point on the tape winding surface;

[0044] The connecting submodule is used to connect the second scattered points with line segments after fitting to form a new yarn winding surface.

[0045] In summary, the technical solution of the present invention has the following technical effects:

[0046] The present invention uses the core mold surface of the elliptical head of the composite pressure vessel as the yarn winding surface of the first winding layer, and uses the yarn winding surface of the previous winding layer as the yarn winding surface of the next winding layer. This not only takes into account the influence of the yarn winding of the first winding layer of the elliptical head of the composite pressure vessel on the three-dimensional shape of the subsequent yarn, but also takes into account the influence of each layer of yarn winding on the head surface. This ensures the accuracy of the three-dimensional winding shape of the yarn on the pressure vessel head, determines the contours of each layer of the pressure vessel head, more accurately reflects the thickness characteristics of the wound composite pressure vessel head, ensures the thickness prediction result of the pressure vessel head, and is suitable for more refined modeling of pressure vessels. Compared with traditional methods, the present invention can more accurately predict the contour characteristics on the pressure vessel head, and provides a reference for establishing a refined simulation method for pressure vessels. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0048] Figure 1Schematic diagram of the process of thickness prediction method for wound composite pressure vessel head according to an embodiment of the present invention;

[0049] Figure 2 Schematic diagram of different winding layers;

[0050] Figure 3 This is a schematic diagram of the rotation profile of the pressure vessel head;

[0051] Figure 4 This is a schematic diagram of the three-dimensional shape of the first layer of yarn;

[0052] Figure 5 It is a schematic diagram of two equivalent points on the equivalent sphere;

[0053] Figure 6 It is a schematic diagram of the discrete points of the yarn tape;

[0054] Figure 7 Fitting diagram of the second scatter point;

[0055] Figure 8 Schematic diagram for solving the three-dimensional shape and thickness of the yarn tape other than the first winding layer;

[0056] Figure 9 Schematic diagram for solving the thickness of the pressure vessel head;

[0057] Figure 10 This is a schematic diagram of a thickness prediction result case after the implementation of the present invention. DETAILED DESCRIPTION

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of 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 of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0059] This embodiment provides a thickness prediction method for wound composite pressure vessel heads. Figure 1 , the thickness prediction method includes:

[0060] Step S1: Using the core mold surface of the elliptical head of the composite pressure vessel as the yarn winding surface of the first winding layer, and using the first winding layer as the current winding layer.

[0061] The wound composite pressure vessel in this embodiment includes multiple wound layers, such as Figure 2The composite pressure vessel shown has six wrapping layers. The first wrapping layer is the one directly wrapped around the core mold surface of the elliptical head (i.e., the first wrapping layer refers to the composite wrapping layer formed when the yarn is directly wrapped around the core mold surface). Starting with the first wrapping layer, the wrapping layer number increases by one with each wrapping of the yarn. The wrapping surface of the yarn wrapped around the wrapping layer is not the first wrapping layer.

[0062] Step S2: Determine the left and right boundaries of the yarn on the current winding layer by using the rotation axis of the yarn winding surface of the current winding layer and the polar hole direction of the elliptical head of the composite pressure vessel.

[0063] If the current winding layer is the first winding layer, the scattered points on the yarn winding trajectory on the ellipsoidal surface are calculated using the geodesic equation or non-geodesic equation. Then, the equivalent sphere of the ellipsoidal surface is solved to calculate the equivalent points of the scattered points on the yarn winding trajectory (i.e.) on the equivalent sphere. The shortest distance between two points on the equivalent sphere is solved based on the minor arc, and the scattered points on the three-dimensional left and right boundaries of the yarn are solved by combining the bisection method. The specific process of determining the left and right boundaries of the yarn on the current winding layer includes:

[0064] Step S211: Align the rotation axis of the elliptical head of the composite pressure vessel with the Z axis of the cylindrical coordinate system, set the direction of the equator pointing to the polar hole as the positive direction, and construct a cylindrical coordinate system to determine the tape winding trajectory on the current winding layer (i.e., the first winding layer) on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system.

[0065] Combine Figure 3 The rotation profile of the pressure vessel head shown in FIG. 1 is an elliptical surface (i.e., the expression of the elliptical curve of the elliptical surface on the meridian plane) on the ellipsoidal surface (i.e., the rotation profile of the pressure vessel head) of the composite pressure vessel elliptical head in this embodiment:

[0066]

[0067] The tape winding trajectory on the current winding layer (i.e., the first winding layer) in this embodiment is:

[0068]

[0069] Wherein, α is the winding angle of the yarn winding trajectory on the front winding layer, θ is the central angle of the yarn winding trajectory on the front winding layer, θ∈[0,2π); λ is the slip coefficient, when λ=0, the yarn winding is geodesic winding; when λ≠0, the yarn winding is non-geodesic winding; r is the radius of the intersection of the plane passing through any point on the yarn winding trajectory on the front winding layer and perpendicular to the rotation axis with the core mold surface; R eis the long diameter of the elliptical head of the composite pressure vessel, r∈[R e ,R p ], R p R is the radius of the hole of the elliptical head of the composite pressure vessel; d is the short diameter of the elliptical head of the composite pressure vessel; and are the first and second derivatives of r with respect to z, respectively. The winding angle of the first point on the yarn winding trajectory in this embodiment is 89.5°. The yarn winding trajectory in this embodiment can be used as the center line of the yarn.

[0070] Step S212: performing a Cartesian coordinate transformation on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system to calculate an equivalent point on the equivalent sphere of each third scattered point on the tape winding trajectory on the current winding layer.

[0071] The ellipsoidal surface after the Cartesian coordinate system conversion in this embodiment is:

[0072]

[0073] The ellipsoidal surface of the elliptical head of the composite pressure vessel is mapped one by one to the equivalent spherical surface, as shown in Figure 5 As shown, the equivalent sphere in this embodiment is:

[0074]

[0075] Wherein, (x, y, z) is the coordinate of the third scattered point on the yarn winding trajectory on the current winding layer; (x′, y′, z′) is the coordinate of the equivalent point on the equivalent sphere, and z′ ≥ 0.

[0076] Step S213: Calculate the shortest distance between two equivalent points on the equivalent sphere using the width of the yarn tape to determine the left boundary and the right boundary of the yarn tape of the current winding layer.

[0077] If there are two points on the ellipsoid, there is a shortest path along the ellipsoid. When this shortest path is mapped to the equivalent sphere, it is the minor arc between the two corresponding points on the sphere.

[0078] The minimum value of the shortest path from any point on the tape boundary along the elliptical surface to all scattered points on the tape winding trajectory is half the bandwidth. The specific process is: an initial point is projected onto the ellipsoid, the initial point is mapped onto the equivalent sphere, and the inferior arcs between the initial point and all discrete points on the tape winding trajectory are calculated. All inferior arcs are discretized into a finite number of scattered points and then mapped back onto the ellipsoid. The path length is calculated using the sum of straight line segments. The minimum value of the shortest path length is half the bandwidth, otherwise the point is re-projected.

[0079] like Figure 6 As shown, the shortest distance between two points on the ellipsoidal surface corresponding to two equivalent points on the equivalent sphere in this embodiment is:

[0080]

[0081] in, The left boundary line T on the yarn winding track on the current winding layer 2m Along the core mold surface to the yarn winding track T m The distance to the hth equivalent point on the , h=1,2,...,H, H is the number of equivalent points; T i′ Left boundary line T 2m and tape winding trajectory T m The i′th curve after the yarn tape between them is discretized; W b is the width of the yarn, i′=m,m+1,...,2m-1, m is the left boundary line T 2m and tape winding trajectory T m The number of curves after the yarn tape is discretized; (*) min Take the minimum value.

[0082] For any point on the ellipsoid, the shortest path distances between it and the centerline trajectory point (i.e., the tape winding trajectory point) can be obtained through the minor arc of the equivalent point. Among these shortest paths, if the minimum value is less than the tape width W b If the shortest path is half the width, re-project the points away from the centerline trajectory; conversely, re-project the points toward the trajectory. The shortest path minimum is recalculated until its difference from half the width does not exceed a set threshold. By continuously projecting points on different z-planes, a series of tape boundary points can be obtained.

[0083] If the current winding layer is not the first winding layer, the geodesic equation of the yarn is solved by the discrete method to obtain the scattered points on the winding trajectory of the current winding layer. Then, the scattered points on the left and right boundaries of the head surface corresponding to the winding trajectory are determined by the derived differential relationship. The specific process of determining the left and right boundaries of the yarn on the current winding layer includes:

[0084] Step S221: Discretely process the tape winding surface on the current winding layer to obtain the tape winding trajectory on the current winding layer (ie, not the first winding layer).

[0085] If the current winding layer is not the first winding layer, the yarn winding surface is composed of the obtained scattered points, and the shape can be described as z = f i (r), i>1, i represents the number of layers currently wrapped, which is composed of a series of scattered points It is composed of connected straight line segments, refer to Figure 8 .

[0086] The yarn winding trajectory in this step is:

[0087]

[0088] Among them, α i,j is the winding angle of the tape winding trajectory on the i-th winding layer at the j-th fourth scattered point; θ i,j is the central angle of the tape winding trajectory on the i-th winding layer at the j-th fourth scattered point; (r r,j ,θ i,j ,z i,j ) is the coordinate of the jth fourth scattered point of the tape winding trajectory on the i-th winding layer in the cylindrical coordinate system, i>1; λ is the slip coefficient.

[0089] Step S222: using the differential relationship between two adjacent fifth scattered points, solving the coordinates of each fifth scattered point on the winding trajectory of the tape on the current winding layer to determine the left boundary and the right boundary of the tape on the winding layer.

[0090] For any discrete point on the center trajectory (i.e., the yarn winding trajectory), the boundary point corresponding to the point can be calculated by performing J calculations in combination with formula (10). The same operation is performed on all scattered points on the yarn winding trajectory to finally determine the boundary of the yarn on the current winding layer and its three-dimensional shape.

[0091] The differential relationship between two adjacent fifth scattered points in this embodiment is:

[0092]

[0093] Among them, (r j′ ,θ j′ ,z j′ ) and (r j′ +dr j′+1 ,θ j′ +dθ j′+1 ,z j′ +dz j′+1 ) are the coordinates of the j′th fifth scattered point on the yarn winding trajectory; dr j′+1 , dθ j′+1 and dz j′+1 are the differences in the corresponding coordinate axes between the j′+1th fifth scattered point and the j′th fifth scattered point on the yarn winding trajectory; is the angle between the line segment in the width direction of the yarn and the tangent; j′=1,2,...,J, J is the fifth scattered point number on the yarn winding trajectory; |*| is the absolute value.

[0094] Step S3: using the left boundary and the right boundary of the tape on the current winding layer, determine second scattered points corresponding to the first scattered points on the tape winding surface of the current winding layer to form a new tape winding surface.

[0095] The three-dimensional winding form of the yarn on any layer (such as Figure 4 After the thickness of the tape is determined (as shown), according to the winding boundary of each layer of tape, the thickness of different positions on the tape winding surface (such as the core mold surface of the elliptical head of the composite pressure vessel, or the previous layer) is solved. Then, on the meridian plane, the tangents at different positions of the previous head contour are solved. If it is a curve connected by discrete points, the straight line at that position with the same angle as the line segment formed by the front and rear scattered points is regarded as the tangent at that position. Then solve the perpendicular line of the tangent at different positions, increase the thickness value of the pressure vessel head at different positions along the perpendicular direction, and obtain scattered points corresponding to the scattered points on the current contour one by one. After connecting these scattered points through line segments, a new surface (i.e., a new tape winding surface) is formed. The specific formation process of the new tape winding surface includes:

[0096] Step S31: Calculate the thickness value of each first scattered point on the winding surface of the tape using the left boundary and the right boundary of the tape on the current winding layer.

[0097] like Figure 9 As shown, for any z plane, it has an intersection with the left and right boundaries of the three-dimensional yarn. Combining the arc between the intersection points and the radius of the parallel circle, the central angle of the yarn in the z plane is obtained, and then the thickness in the z plane is calculated.

[0098] The thickness values at each first scattered point on the winding surface of the yarn tape in this embodiment are:

[0099]

[0100] in, is the thickness of the first scattered point j″ on the winding surface of the yarn on the i-th winding layer; n b is the number of times the ribbon passes through the equator when it completely wraps the equator; θ i′,j″ t is the central angle occupied by the intersection of the yarn at the j″th first scattered point on the i-th winding layer and the parallel circle on the vertical line; b is the thickness of the gauze.

[0101] Step S32, obtaining perpendicular lines of tangents of the ribbon winding surface at each first scattered point on the meridian plane;

[0102] The tangent line of a point on the inner contour line of the first winding layer (i.e., the yarn winding surface) is expressed by formula (12).

[0103]

[0104] The tangent of a point on the inner contour line of a non-first winding layer (i.e., the yarn winding surface): is determined by the straight line segments connecting the point and the adjacent points on both sides. The angles between the tangent and the two straight line segments satisfy the equality relationship, that is, any first scattered point on the yarn winding surface on the meridian plane is connected to its adjacent points on both sides to obtain two straight line segments; then, the angles formed by the tangent and the two straight line segments are equal to determine the tangent at any first scattered point on the yarn winding surface on the meridian plane.

[0105] Step S33: increasing the thickness value at each first scattered point on the tape winding surface along the perpendicular direction of the corresponding first scattered point to obtain second scattered points corresponding to each first scattered point on the tape winding surface.

[0106] Increase the thickness at the inner contour point (i.e. the first scattered point) in the direction perpendicular to the tangent to obtain the point on the outer contour of the current winding layer (i.e. the second scattered point on the new yarn winding surface), refer to Figure 8 and Figure 9 , the point on the outer contour of the current winding layer (i.e. the second scattered point on the new yarn winding surface) is:

[0107]

[0108] Among them, r B and z B is the coordinate of the second scattered point B in the cylindrical coordinate system; r i，,j″ and z i，,j″ are the coordinates of the j″th first scattered point on the winding surface of the yarn on the i-th winding layer in the cylindrical coordinate system; is the slope of the tangent line at the j″th first scattered point on the winding surface of the yarn on the i-th winding layer.

[0109] Step S34: Fit the second scattered points and connect them with line segments to form a new yarn winding surface.

[0110] In order to reduce the deviation of the thickness prediction result of the pressure vessel head caused by the burrs on the surface of each layer of yarn tape, this embodiment uses the following quadratic equation to fit the second scattered point:

[0111] z=a1r 2 +a2r+a3; (14)

[0112] Among them, z represents the height position of the second scattered point; r represents the radius position of the second scattered point; a1, a2 and a3 are fitting coefficients. The least squares method is used to solve the (local) second scattered point. The fitting results are referenced to Figure 7 .

[0113] This embodiment achieves smooth fitting of the tape winding surface by fitting the second scattered points, ensures the smoothness of the tape winding surface of each layer, and further improves the accuracy of the thickness prediction result of the pressure vessel head.

[0114] Connect these points (the second scattered points after fitting) through straight line segments to form the next rotation profile z=f of the yarn winding surface i (r).

[0115] Step S4, determine whether the current winding layer is the last winding layer. If so, use the new tape winding surface as the outermost contour of the elliptical head of the composite pressure vessel, and end; if not, use the new tape winding surface as the tape winding surface of the next winding layer of the current winding layer, and use the next winding layer as the current winding layer, and return to step S2.

[0116] refer to Figure 10 , showing the outer contour prediction results of the pressure vessel.

[0117] This embodiment uses the core mold surface of the elliptical head of the composite pressure vessel as the tape winding surface of the first winding layer, and the tape winding surface of the previous winding layer as the tape winding surface of the next winding layer. It not only takes into account the influence of the tape winding of the first winding layer on the three-dimensional shape of the subsequent tapes of the elliptical head of the composite pressure vessel, but also takes into account the influence of each layer of tape winding on the head surface. It ensures the accuracy of the three-dimensional winding shape of the tape on the pressure vessel head, determines the contours of each layer of the pressure vessel head, more accurately reflects the thickness characteristics of the wound composite pressure vessel head, ensures the thickness prediction results of the pressure vessel head, and is suitable for more refined modeling of pressure vessels. Compared with traditional methods, this embodiment can more accurately predict the contour characteristics on the pressure vessel head, and provide a reference for establishing a refined simulation method for pressure vessels.

[0118] The technical solutions of the above embodiments can be implemented using the technical solutions of the following embodiments:

[0119] Another embodiment provides a thickness prediction system for a wound composite pressure vessel head, the thickness prediction system comprising:

[0120] As a module, it is used to use the core mold surface of the elliptical head of the composite pressure vessel as the yarn winding surface of the first winding layer, and use the first winding layer as the current winding layer;

[0121] a determination module, configured to determine the left and right boundaries of the yarn on the current winding layer by using the rotation axis of the yarn winding surface of the current winding layer and the polar hole direction of the elliptical head of the composite pressure vessel;

[0122] a forming module, configured to determine, by using the left boundary and the right boundary of the tape on the current winding layer, second scattered points corresponding to the first scattered points on the tape winding surface of the current winding layer, so as to form a new tape winding surface;

[0123] The judgment module is used to judge whether the current winding layer is the last winding layer. If so, the new yarn tape winding surface is used as the outermost contour of the elliptical head of the composite pressure vessel, and the process ends; if not, the new yarn tape winding surface is used as the yarn tape winding surface of the next winding layer of the current winding layer, and the next winding layer is used as the current winding layer, and transmitted to the determination module.

[0124] Further, when the current winding layer is the first winding layer, the determining module includes:

[0125] A construction submodule is used to coincide the rotation axis of the elliptical head of the composite pressure vessel with the Z axis of the cylindrical coordinate system, set the direction from the equator to the polar hole as the positive direction, and construct a cylindrical coordinate system to determine the yarn winding trajectory of the current winding layer on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system;

[0126] a conversion submodule, configured to perform Cartesian coordinate conversion on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system, so as to calculate an equivalent point on the equivalent sphere of each third scattered point on the winding trajectory of the yarn on the current winding layer;

[0127] A first calculation submodule is configured to calculate the shortest distance between two equivalent points on the equivalent sphere using the width of the yarn tape to determine the left boundary and the right boundary of the yarn tape of the current winding layer;

[0128] Furthermore, when the current winding layer is not the first winding layer, the determining module includes:

[0129] a discrete processing submodule, configured to perform discrete processing on the tape winding surface on the current winding layer to obtain the tape winding trajectory on the current winding layer;

[0130] The solving submodule is used to solve the coordinates of each fifth scattered point on the winding trajectory of the tape on the current winding layer by using the differential relationship between two adjacent fifth scattered points to determine the left boundary and the right boundary of the tape on the winding layer.

[0131] Furthermore, the forming module includes:

[0132] A second calculation submodule is configured to calculate the thickness value of each first scattered point on the winding surface of the yarn tape by using the left boundary and the right boundary of the yarn tape on the current winding layer;

[0133] An acquisition submodule, configured to acquire a perpendicular line of a tangent line of the ribbon winding surface at each first scattered point on the meridian plane;

[0134] An adding submodule, configured to increase the thickness value at each first scattered point on the tape winding surface along a perpendicular direction corresponding to the first scattered point, to obtain second scattered points corresponding to each first scattered point on the tape winding surface;

[0135] The connecting submodule is used to connect the second scattered points with line segments after fitting to form a new yarn winding surface.

[0136] The principles, formulas and parameter definitions involved in the above embodiments are all applicable and will not be described in detail here.

[0137] The above embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A thickness prediction method for wound composite pressure vessel heads, characterized in that: The thickness prediction method comprises: Step S1: using the core mold surface of the elliptical head of the composite pressure vessel as the yarn winding surface of the first winding layer, and using the first winding layer as the current winding layer; Step S2: determining the left and right boundaries of the yarn on the current winding layer by using the rotation axis of the yarn winding surface of the current winding layer and the polar hole direction of the elliptical head of the composite pressure vessel; Step S3: using the left boundary and the right boundary of the tape on the current winding layer, determining second scattered points corresponding to the first scattered points on the tape winding surface of the current winding layer to form a new tape winding surface; Step S4, determine whether the current winding layer is the last winding layer. If so, use the new tape winding surface as the outermost contour of the elliptical head of the composite pressure vessel, and end; if not, use the new tape winding surface as the tape winding surface of the next winding layer of the current winding layer, and use the next winding layer as the current winding layer, and return to step S2.

2. The thickness prediction method according to claim 1, characterized in that: In step S2, when the current winding layer is the first winding layer, the specific process of determining the left boundary and the right boundary of the yarn tape on the current winding layer includes: Step S211: aligning the rotation axis of the elliptical head of the composite pressure vessel with the Z axis of the cylindrical coordinate system, setting the direction from the equator to the polar hole as the positive direction, and constructing a cylindrical coordinate system to determine the tape winding trajectory of the current winding layer on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system; Step S212: performing a Cartesian coordinate transformation on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system to calculate an equivalent point on the equivalent sphere of each third scattered point on the winding trajectory of the yarn on the current winding layer; Step S213: Calculate the shortest distance between two equivalent points on the equivalent sphere using the width of the yarn tape to determine the left boundary and the right boundary of the yarn tape of the current winding layer.

3. The thickness prediction method according to claim 1, characterized in that: In step S2, when the current winding layer is not the first winding layer, the specific process of determining the left boundary and the right boundary of the yarn tape on the current winding layer includes: Step S221: performing discrete processing on the tape winding surface on the current winding layer to obtain the tape winding trajectory on the current winding layer; Step S222: using the differential relationship between two adjacent fifth scattered points, solving the coordinates of each fifth scattered point on the winding trajectory of the tape on the current winding layer to determine the left boundary and the right boundary of the tape on the winding layer.

4. The thickness prediction method according to any one of claims 1 to 3, characterized in that: In step S3, the specific process of forming a new tape winding surface includes: Step S31, using the left boundary and the right boundary of the yarn on the current winding layer, calculating the thickness value of each first scattered point on the yarn winding surface; Step S32, obtaining perpendicular lines of tangents of the ribbon winding surface at each first scattered point on the meridian plane; Step S33, increasing the thickness value at each first scattered point on the tape winding surface along the perpendicular direction of the corresponding first scattered point to obtain a second scattered point corresponding to each first scattered point on the tape winding surface; Step S34: Fit the second scattered points and connect them with line segments to form a new yarn winding surface.

5. The thickness prediction method according to claim 4, characterized in that: In step S31, the thickness value at each first scattered point on the winding surface of the ribbon is: in, is the thickness of the first scattered point j″ on the winding surface of the yarn on the i-th winding layer; n b is the number of times the ribbon passes through the equator when it completely wraps the equator; θ i ' ,j″ t is the central angle occupied by the intersection of the yarn at the j″th first scattered point on the i-th winding layer and the parallel circle on the vertical line; b is the thickness of the gauze.

6. A thickness prediction system for wound composite pressure vessel heads, characterized in that: The thickness prediction system comprises: As a module, it is used to use the core mold surface of the elliptical head of the composite pressure vessel as the yarn winding surface of the first winding layer, and use the first winding layer as the current winding layer; a determination module, configured to determine the left and right boundaries of the yarn on the current winding layer by using the rotation axis of the yarn winding surface of the current winding layer and the polar hole direction of the elliptical head of the composite pressure vessel; a forming module, configured to determine, by using the left boundary and the right boundary of the tape on the current winding layer, second scattered points corresponding to the first scattered points on the tape winding surface of the current winding layer, so as to form a new tape winding surface; The judgment module is used to judge whether the current winding layer is the last winding layer. If so, the new yarn tape winding surface is used as the outermost contour of the elliptical head of the composite pressure vessel, and the process ends; if not, the new yarn tape winding surface is used as the yarn tape winding surface of the next winding layer of the current winding layer, and the next winding layer is used as the current winding layer, and transmitted to the determination module.

7. The thickness prediction system according to claim 6, characterized in that: When the current winding layer is the first winding layer, the determining module includes: A construction submodule is used to coincide the rotation axis of the elliptical head of the composite pressure vessel with the Z axis of the cylindrical coordinate system, set the direction from the equator to the polar hole as the positive direction, and construct a cylindrical coordinate system to determine the yarn winding trajectory of the current winding layer on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system; a conversion submodule, configured to perform Cartesian coordinate conversion on the ellipsoidal surface of the elliptical head of the composite pressure vessel in the cylindrical coordinate system, so as to calculate an equivalent point on the equivalent sphere of each third scattered point on the winding trajectory of the yarn on the current winding layer; The first calculation submodule is configured to calculate the shortest distance between two equivalent points on the equivalent sphere using the width of the yarn tape, so as to determine the left boundary and the right boundary of the yarn tape of the current winding layer.

8. The thickness prediction system according to claim 6, characterized in that: When the current winding layer is not the first winding layer, the determining module includes: a discrete processing submodule, configured to perform discrete processing on the tape winding surface on the current winding layer to obtain the tape winding trajectory on the current winding layer; The solving submodule is used to solve the coordinates of each fifth scattered point on the winding trajectory of the tape on the current winding layer by using the differential relationship between two adjacent fifth scattered points to determine the left boundary and the right boundary of the tape on the winding layer.

9. The thickness prediction system according to any one of claims 6 to 8, characterized in that: The formation module includes: A second calculation submodule is configured to calculate the thickness value of each first scattered point on the winding surface of the yarn tape by using the left boundary and the right boundary of the yarn tape on the current winding layer; An acquisition submodule, configured to acquire a perpendicular line of a tangent line of the tape winding surface at each first scattered point on the meridian plane; An adding submodule, configured to increase the thickness value at each first scattered point on the tape winding surface along a perpendicular direction corresponding to the first scattered point, to obtain second scattered points corresponding to each first scattered point on the tape winding surface; The connecting submodule is used to connect the second scattered points with line segments after fitting to form a new yarn winding surface.

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