A high-precision modeling method for aircraft long-strut stiffened panels based on triangular mesh

Abstract

The present invention discloses a high-precision modeling method for aircraft long-string reinforced wall panels based on triangular meshes. In the prior art, when modeling is performed by FEM software, the preliminary preparation for modeling must be careful, the measurement data must be accurate, and the workload during the modeling process is large. When modeling is performed by CAD software, the amount of manual operation is large, and the structural investigation and measurement must be targeted. The present invention first constructs an overall long-string reinforced wall panel cross-sectional model, and if it is a curved skin, it determines whether the degree of fit between each long stringer on the curved skin and the contact surface of the curved skin meets the requirements. If the requirements are not met, the grid is further subdivided and the model is reconstructed until the degree of fit between each long stringer on the curved skin and the contact surface of the curved skin meets the requirements, and finally a three-dimensional model is obtained by stretching. Compared with traditional FEM modeling or CAD modeling, the present invention has strong pertinence, improves modeling efficiency, has higher detail accuracy, and reduces manual labor while ensuring efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft long-string stiffened wall panel modeling, and in particular relates to a high-precision modeling method of aircraft long-string stiffened wall panels based on triangular meshes. Background Art

[0002] Composite long-string stiffened wall panels are a typical structural component of aircraft. Accurate three-dimensional computer modeling of them is the basis for the implementation of technologies such as simulation analysis and digital twin state monitoring. It is of great significance for reducing the weight of aircraft structures, improving structural bearing capacity, and improving structural safety.

[0003] In the prior art, the modeling of aircraft long-string stiffened wall panels is mainly divided into two categories: modeling in finite element analysis software and computer-aided modeling based on CAD. In FEM (finite element method) software, three-dimensional modeling is performed by decomposing actual objects into small discrete units. These units can be simple geometric shapes, such as triangles or quadrilaterals, or more complex voxels or polyhedrons. Each unit has associated physical properties and behaviors, such as material properties, stiffness and elasticity, etc., and for high-precision aircraft long-string stiffened wall panel modeling, modeling in FEM software has the following difficulties: on the one hand, the long stringers and stiffened wall panels have complex geometric shapes and structures, including curves, special-shaped sections and connection joints, etc., and it is a challenge to accurately convert these complex geometric shapes into discrete finite element models, which requires careful preliminary preparation and accurate measurement data; on the other hand, the behavior of the long stringers and stiffened wall panels is usually nonlinear, involving large deformation, material nonlinearity and contact, which requires more complex physical properties and behaviors to be considered in the modeling process, such as nonlinear stress-strain relationships of materials and contact boundary conditions, etc., which increases the modeling workload. Although the modeling method based on CAD computer-aided design can provide very accurate three-dimensional geometric models, the creation and modification of CAD models usually requires a lot of manual operations and a lot of targeted structural research and measurement, which may become a limitation in some applications. Therefore, there is an urgent need for a modeling method for aircraft long-truss stiffened wall panels that can save labor costs, improve the efficiency of related analysis and research, and is targeted and accurate. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and to propose a high-precision modeling method for aircraft long-string stiffened wall panels based on triangular meshes.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a high-precision modeling method for aircraft long-string stiffened wall panels based on triangular meshes, which is specifically as follows:

[0007] Step 1: Set the geometric parameters of the long stringer, straight skin and curved skin.

[0008] Step 2: Calculate the coordinates of pre-selected boundary points on the cross section of the long stringer and the straight skin or the curved skin in the same coordinate system according to the geometric parameters of the long stringer and the straight skin or the curved skin.

[0009] Step 3: Design a triangular mesh arrangement that traverses all boundary points on the cross section of the long stringer and the straight skin or the curved skin, and calculate the coordinates of all nodes on the cross section of the long stringer and the straight skin or the curved skin to complete the preliminary modeling of the cross section of the long stringer and the straight skin or the curved skin structure.

[0010] Step 4: Set the layout parameters of the long stringer.

[0011] Step 5: Based on the layout parameters of the girder, calculate the coordinates of all nodes when a girder is arranged on a straight skin or a curved skin.

[0012] Step 6. Perform coordinate transformation according to the model of the long stringer in step 5 to obtain the arrangement of the remaining long strings on the straight skin or curved skin. If it is a straight skin, the overall long stringer reinforced wall panel cross-section model is completed and step 8 is directly executed. If it is a curved skin, step 7 is executed.

[0013] Step 7: Determine whether the degree of fit between the contact surface of each long stringer on the curved skin and the curved skin meets the requirements. If not, change the position of each long stringer in contact with the curved skin to a curved structure composed of multiple smaller triangular meshes, and return to step 5; if it meets the requirements, determine that the overall long stringer reinforced wall panel cross-section model is completed, and execute step 8.

[0014] Step 8: By stretching along the Z direction perpendicular to the cross section of the long stringer, the final three-dimensional model of the long stringer reinforced wall panel is obtained.

[0015] Preferably, the geometric parameters of the long stringer, the straight skin and the curved skin in step 1 are set as follows: the bottom side length of the long stringer is a=2, the half bottom surface length of the cavity is b=2, the height is c=2, the half top surface length of the cavity is d=1, and the thickness is h 1 =0.5, longitudinal length l 1 =50; Assume that the horizontal length of the straight skin is L = 50, and the thickness is h 2 =0.5, longitudinal length l 2 =50; Assume that the angle of the bending skin is θ = 90, the inner diameter is R = 50, and the thickness is h 3 =0.5, longitudinal length l 3 =50.

[0016] Preferably, the layout parameter of the long stringers in step 4 is the number of long stringers n=5.

[0017] Preferably, since the three-dimensional model can be formed by stretching the two-dimensional model along the z direction, the z-direction component is not considered in the calculation of step five and step six, and the calculation is only performed on the cross section of the long stringer and the straight skin or the curved skin. When the straight skin is used in step six, the long stringer in step five is set at the side of the straight skin. According to the layout parameters of the long stringer, by translating the coordinates of the long stringer, the matrix composed of the horizontal coordinates of all nodes on the i-th long stringer away from the side of the straight skin is obtained:

[0018]

[0019] Among them, x 0 is the matrix composed of the horizontal coordinates of all nodes on the long stringer in step 5, L is the lateral length of the straight skin, a is the length of the bottom side of the long stringer, b is the length of the half bottom surface of the cavity of the long stringer, and n is the number of long strings;

[0020] The matrix composed of the ordinates of all nodes on the i-th long stringer from the side of the straight skin is:

[0021] y i =y 0

[0022] Among them, y 0 is the matrix composed of the ordinates of all nodes on the long girder in step 5;

[0023] When the skin is curved in step 6, the long stringer in step 5 is set in the middle of the curved skin, and the coordinates of the long stringer are rotated and arranged according to the layout parameters of the long stringer to calculate the coordinate matrix of all nodes on the i-th long stringer from the side of the curved skin as follows:

[0024] First, solve the arc length L of the long stringer on the upper surface of the curved skin truss :

[0025]

[0026] Then solve the arc length s between the center of the cavity bottom surface of the i-th long stringer from the side of the curved skin and the side of the curved skin i :

[0027]

[0028] Then solve the angle θ that the i-th long stringer at the side of the curved skin needs to rotate relative to the long stringer in step 5 i :

[0029]

[0030] Then the rotation matrix corresponding to the i-th stringer from the side of the curved skin is:

[0031]

[0032] The coordinate matrix of all nodes on the i-th stringer from the side of the curved skin is:

[0033] v i =A i *v 0

[0034] Where R is the inner diameter of the curved skin, θ is the angle of the curved skin, and v 0 is the coordinate matrix of all nodes on the long stringer in step 5, v i is the coordinate matrix of all nodes on the i-th stringer from the side of the curved skin, v 0 and v i They only contain two components: the horizontal axis and the vertical axis.

[0035] Preferably, in step 7, the center of the curved skin is taken as the coordinate origin, and the degree of fit between the contact surface of the long stringer and the curved skin is characterized by the distance between each node of the bottom edge of the long stringer and the coordinate origin and the mean square error δ of the inner diameter of the curved skin. If δ<0.005, it means that the degree of fit between the contact surface of the long stringer and the curved skin meets the requirement, otherwise it means that the degree of fit between the contact surface of the long stringer and the curved skin does not meet the requirement; wherein,

[0036]

[0037] N is the number of nodes at the bottom of the long girder, x j and j are the abscissa and ordinate of the jth node at the bottom of the stringer, and R is the inner diameter of the curved skin.

[0038] Preferably, the triangular mesh in step seven is an equilateral triangular mesh.

[0039] The beneficial effects of the present invention are as follows:

[0040] Compared with traditional FEM modeling or CAD modeling, the present invention takes into account the geometric and deformation characteristics of the aircraft long-truss stiffened wall panel structure, has strong pertinence, improves modeling efficiency, and has higher detail accuracy, while being able to reduce manual labor while ensuring efficiency; in addition, the model structure composed of triangular meshes in the present invention is simple, takes up little memory, and can be displayed in the viewport with high fluency. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a flow chart of the present invention;

[0042] Figure 2 It is a schematic diagram of a three-dimensional model of a long stringer in the present invention;

[0043] Figure 3A schematic diagram of a three-dimensional model of a flat skin in the present invention;

[0044] Figure 4 A schematic diagram of a three-dimensional model of a curved skin in the present invention;

[0045] Figure 5 This is a modeling effect diagram when the bottom edge of the long stringer in the present invention is fitted with the upper surface of the curved skin;

[0046] Figure 6 It is a schematic diagram of a three-dimensional model of a long-string reinforced wall panel composed of a straight skin and long strings in the present invention;

[0047] Figure 7 It is a schematic diagram of a three-dimensional model of a long-string reinforced wall panel composed of a curved skin and long strings in the present invention. DETAILED DESCRIPTION

[0048] The present invention is further described below in conjunction with the accompanying drawings.

[0049] like Figure 1 As shown, the present invention provides a high-precision modeling method for aircraft long-truss stiffened wall panels based on triangular meshes, which is specifically as follows:

[0050] Step 1: Set the geometric parameters of the long stringer and the skin: set the length of the bottom side of the long stringer a = 2, the length of the half bottom surface of the cavity b = 2, the height c = 2, the length of the half top surface of the cavity d = 1, and the thickness h 1 =0.5, longitudinal length l 1 =50, then the modeling result of the long girder in the current situation is as follows Figure 2 As shown; the skin is divided into straight skin and curved skin. Assume that the horizontal length of the straight skin is L = 50 and the thickness is h 2 =0.5, longitudinal length l 2 = 50, then the modeling result of the flat skin in the current case is as follows Figure 3 As shown, the angle of the curved skin (the central angle of the circle) is θ = 90, the inner diameter is R = 50, and the thickness is h 3 =0.5, longitudinal length l 3 = 50, then the modeling result of the curved skin in the current case is as follows Figure 4 As shown in FIG. 1 , the geometric parameter units of the long stringer, the straight skin and the curved skin can be changed according to actual needs.

[0051] Step 2: According to the geometric parameters of the long stringer, the straight skin and the curved skin, the coordinates of the pre-selected boundary points on the long stringer and the straight skin or the curved skin cross section are calculated in the same coordinate system. The coordinates of the pre-selected boundary points on the long stringer and the straight skin cross section are calculated in the rectangular coordinate system, and the coordinates of the pre-selected boundary points on the long stringer and the curved skin cross section are calculated in the polar coordinate system with the center of the curved skin as the coordinate origin.

[0052] Step 3: Design a triangular mesh arrangement that traverses all boundary points on the cross section of the stringer and the straight skin or the curved skin, and calculate the coordinates of all nodes on the cross section of the stringer and the straight skin or the curved skin, to complete the preliminary cross-sectional modeling of the stringer and the straight skin or the curved skin structure (including the local stringer model and the local skin model at the contact position between the stringer and the skin).

[0053] Step 4: Set the layout parameters of the long stringers to the number of long stringers n=5.

[0054] Step 5. According to the layout parameters of the long stringer, calculate the coordinates of all nodes when a long stringer is arranged on a straight skin or a curved skin. Since the three-dimensional model can be formed by stretching the two-dimensional model along the z direction, the z-direction component is not considered in the calculation, and the calculation is only performed on the cross section of the long stringer and the straight skin or the curved skin. When on the straight skin, the long stringer is set at the side of the straight skin. According to the layout parameters of the long stringer, by translating the coordinates of the long stringer, the matrix composed of the horizontal coordinates of all nodes on the i-th long stringer from the side of the straight skin is obtained:

[0055]

[0056] Among them, x 0 is the matrix composed of the horizontal coordinates of all nodes on the long beam.

[0057] The matrix composed of the ordinates of all nodes on the i-th long stringer from the side of the straight skin is:

[0058] y i =y 0

[0059] Among them, y 0 It is a matrix composed of the ordinates of all nodes on the stringer.

[0060] When on the curved skin, the long stringer is set in the middle of the curved skin. According to the layout parameters of the long stringer, the coordinates of the long stringer are rotated and arranged, and the coordinate matrix of all nodes on the i-th long stringer from the side of the curved skin is calculated as follows:

[0061] First, we need to solve the arc length L of the long stringer on the upper surface of the curved skin. truss :

[0062]

[0063] Then solve the arc length s between the center of the cavity bottom surface of the i-th long stringer from the side of the curved skin and the side of the curved skin i :

[0064]

[0065] Then calculate the angle θ that the i-th long stringer on the side of the curved skin needs to rotate relative to the long stringer i :

[0066]

[0067] Then the rotation matrix corresponding to the i-th stringer from the side of the curved skin is:

[0068]

[0069] The coordinate matrix of all nodes on the i-th stringer from the side of the curved skin is:

[0070] v i =A i *v 0

[0071] Among them, v 0 is the coordinate matrix of all nodes on the long stringer, v i is the coordinate matrix of all nodes on the i-th stringer from the side of the curved skin, v 0 and v i They only contain two components: the horizontal axis and the vertical axis.

[0072] Step 6. Perform coordinate transformation according to the model of the long stringer in step 5 to obtain the arrangement of the remaining long strings on the straight skin or curved skin. If it is a straight skin, the overall long stringer reinforced wall panel cross-section model is completed and step 8 is directly executed. If it is a curved skin, step 7 is executed.

[0073] Step 7: Determine whether the contact surfaces of the long stringers and the curved skin fit together. Take the center of the curved skin as the coordinate origin and calculate the distance between each node on the bottom edge of the long stringer and the coordinate origin and the mean square error δ of the inner diameter of the curved skin:

[0074]

[0075] Where N is the number of nodes at the bottom of the long stringer, x j and j are the horizontal and vertical coordinates of the jth node on the bottom side of the girder respectively.

[0076] If δ ≥ 0.005, it means that the contact surface between the long stringer and the curved skin does not meet the requirements. The contact position of each long stringer with the curved skin is changed to a curved structure composed of multiple smaller triangular meshes, such as Figure 5 As shown, return to step five; if δ<0.005, it means that the degree of fit between the contact surface of the long stringer and the curved skin meets the requirements, the overall long stringer stiffened wall panel cross-section model is completed, and step eight is executed.

[0077] Step 8: By stretching along the Z direction perpendicular to the cross section of the long stringer, the final three-dimensional model of the long stringer reinforced wall panel is obtained; wherein the three-dimensional model of the long stringer reinforced wall panel composed of the straight skin and the long stringers is as follows: Figure 6 As shown in the figure, the three-dimensional model of the long-strut stiffened wall panel composed of the curved skin and the long struts is as follows Figure 7 shown.

[0078] As a preferred embodiment, the triangular mesh in step seven is an equilateral triangular mesh.

Claims

1. A high-precision modeling method for aircraft long-string stiffened wall panels based on triangular meshes, characterized in that: The details are as follows: Step 1: Set the geometric parameters of the long stringer, straight skin and curved skin; Step 2: Calculate the coordinates of pre-selected boundary points on the cross section of the long stringer and the straight skin or the curved skin in the same coordinate system according to the geometric parameters of the long stringer, the straight skin and the curved skin; Step 3: Design a triangular mesh arrangement that traverses all boundary points on the cross section of the long stringer and the straight skin or the curved skin, and calculate the coordinates of all nodes on the cross section of the long stringer and the straight skin or the curved skin, to complete the preliminary cross-sectional modeling of the long stringer and the straight skin or the curved skin structure; Step 4: Set the layout parameters of the long stringer; Step 5: Calculate the coordinates of all nodes of a long stringer when it is arranged on a straight skin or a curved skin according to the layout parameters of the long stringer; Step 6: Perform coordinate transformation according to the model of the long stringer in step 5 to obtain the arrangement of the remaining long stringers on the straight skin or the curved skin. If it is a straight skin, the overall long stringer reinforced wall panel cross-section model is completed, and step 8 is directly executed. If it is a curved skin, step 7 is executed; Step 7: Determine whether the degree of fit between the contact surface of each long stringer on the curved skin and the curved skin meets the requirements. If not, change the position of each long stringer in contact with the curved skin to a curved structure composed of multiple smaller triangular meshes, and return to step 5; if it meets the requirements, determine that the overall long stringer reinforced wall panel cross-section model is completed, and execute step 8; Step 8: By stretching along the Z direction perpendicular to the cross section of the long stringer, the final three-dimensional model of the long stringer reinforced wall panel is obtained; The calculations in step 5 and step 6 are only performed on the cross section of the long stringer and the straight skin or the curved skin; when the straight skin is used in step 6, the long stringer in step 5 is set at the side of the straight skin, and according to the layout parameters of the long stringer, the coordinates of the long stringer are translated to obtain the matrix composed of the horizontal coordinates of all nodes on the i-th long stringer from the side of the straight skin: Among them, x0 is the matrix composed of the horizontal coordinates of all nodes on the long stringer in step 5, L is the lateral length of the straight skin, a is the bottom length of the long stringer, b is the half bottom length of the cavity of the long stringer, and n is the number of long strings; The matrix composed of the ordinates of all nodes on the i-th long stringer from the side of the straight skin is: and i =and 0 Among them, y0 is the matrix composed of the ordinates of all nodes on the long stringer in step 5; When the skin is curved in step 6, the long stringer in step 5 is set in the middle of the curved skin, and the coordinates of the long stringer are rotated and arranged according to the layout parameters of the long stringer to calculate the coordinate matrix of all nodes on the i-th long stringer from the side of the curved skin as follows: First, solve the arc length L of the long stringer on the upper surface of the curved skin truss : Then solve the arc length s between the center of the cavity bottom surface of the i-th long stringer and the side of the curved skin: i : Then solve the angle θ that the i-th long stringer at the side of the curved skin needs to rotate relative to the long stringer in step 5 i : Then the rotation matrix corresponding to the i-th stringer from the side of the curved skin is: The coordinate matrix of all nodes on the i-th stringer from the side of the curved skin is: v i =A i *v0 Where R is the inner diameter of the curved skin, θ is the angle of the curved skin, v0 is the coordinate matrix of all nodes on the long stringer in step 5, and v i is the coordinate matrix of all nodes on the i-th stringer at the side of the curved skin.

2. The high-precision modeling method of aircraft long-string reinforced wall panels based on triangular meshes according to claim 1 is characterized in that: In the step 1, the geometric parameters of the long stringer, the straight skin and the curved skin are set as follows: the bottom side length of the long stringer is set to be a=2, the half bottom surface length of the cavity is set to be b=2, the height is set to be c=2, the half top surface length of the cavity is set to be d=1, the thickness is set to be h1=0.5, and the longitudinal length is set to be l1=50; the transverse length of the straight skin is set to be L=50, the thickness is set to be h2=0.5, and the longitudinal length is set to be l2=50; the angle of the curved skin is set to be θ=90, the radius is set to be R=50, the thickness is set to be h3=0.5, and the longitudinal length is set to be l3=50.

3. The high-precision modeling method of aircraft long-string reinforced wall panels based on triangular mesh according to claim 1 is characterized in that: The layout parameter of the long stringers in step 4 is the number of long stringers n=5.

4. The high-precision modeling method of aircraft long-string stiffened wall panels based on triangular meshes according to claim 1 is characterized in that: In the step 7, the center of the curved skin is taken as the coordinate origin, and the degree of fit between the contact surface of the long stringer and the curved skin is characterized by the distance between each node of the bottom edge of the long stringer and the coordinate origin and the mean square error δ of the inner diameter of the curved skin. If δ<0.005, it means that the degree of fit between the contact surface of the long stringer and the curved skin meets the requirement, otherwise it means that the degree of fit between the contact surface of the long stringer and the curved skin does not meet the requirement; wherein, N is the number of nodes at the bottom of the long girder, x j and j are the abscissa and ordinate of the jth node at the bottom of the stringer, and R is the inner diameter of the curved skin.

5. The high-precision modeling method of aircraft long-string stiffened wall panels based on triangular meshes according to claim 1 is characterized in that: The triangular mesh in step seven is an equilateral triangular mesh.

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