KR101604319B1 - Geometrically exact isogeometric shape sensitivity analysis method in curvilinear coordinate system of shell structure - Google Patents
Geometrically exact isogeometric shape sensitivity analysis method in curvilinear coordinate system of shell structure Download PDFInfo
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- KR101604319B1 KR101604319B1 KR1020150060355A KR20150060355A KR101604319B1 KR 101604319 B1 KR101604319 B1 KR 101604319B1 KR 1020150060355 A KR1020150060355 A KR 1020150060355A KR 20150060355 A KR20150060355 A KR 20150060355A KR 101604319 B1 KR101604319 B1 KR 101604319B1
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Abstract
Description
The present invention relates to geometrically rigid isogeometric curvature shape design sensitivity analysis methods, and more particularly, to an accurate and continuous curved surface normal, To a geometrically rigorous isometric geometry design sensitivity sensitivity analysis method that can provide a precise shape design sensitivity analysis result by providing spatial derivatives (curvature, etc.) of the normal.
In general, to model and interpret a curved surface structure such as a shell structure in a Cartesian coordinate system in which a CAD model is implemented, a solid element widely used in finite element technology should be used. This solid element is relatively simple to form because it interpolates the nodal values through an isoparametric transformation to construct the shell surface from the solid element. However, since the analytical model consisting of only the nodal information expressed in the orthogonal coordinate system can not take into account the geometric information of the higher order such as the spatial differential (curvature, etc.) of the normal, a geometrically rigorous interpretation including the bending- it's difficult. In addition, since the solid element needs to be integrated in spite of the surface model, additional integration points in the thickness direction are required, and the integration points used in the actual calculation are ineffective because they are required for the analysis of the two-dimensional surface model. In addition, the influence of missing or inaccurate higher order geometric information becomes more important in the shape design sensitivity analysis of curved surfaces such as the shell structure.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for correcting curved surface design sensitivity in a curved surface design sensitivity analysis, Dimensional curvature shape design sensitivity sensitivity analysis method capable of obtaining a rigid shape design sensitivity analysis result by providing a spatial differential (curvature, etc.) of a normal line.
According to an aspect of the present invention, there is provided a geometrically rigid isothiometry curve design sensitivity analysis method comprising: inputting NURBS data by a NURBS data input unit; Generating a generalized curved surface coordinate system using the input NURBS data in a curved surface coordinate system generating unit; Normalizing the isothiometry analysis model by the iso geometry analysis model normalization unit using the generated generalized curved surface coordinate system; Analyzing the geometrically rigid curved surface by the curved surface analyzing unit using the normalized iso-geometric analytical model; And analyzing the design sensitivity of the curved surface shape by the design sensitivity analysis unit using the analyzed information of the curved surface.
In the geometrically rigid isometric geometric design sensitivity sensitivity analysis method of the present invention, the generalized curved surface coordinate system generation step may include a step of, by the curved surface coordinate system generation unit, Transforming the position vector in the orthogonal coordinate system into the position vector of the curved surface coordinate system, and obtaining the covariance basis vector of the curvature coordinate system.
In the geometrically rigorous isometric geometric design sensitivity analysis method according to the present invention, the step of normalizing the isometrics model is performed by the isomorphic model normalization section, Lt; RTI ID = 0.0 >
[here,
Represents a covariance basis vector of a curved surface coordinate system, x represents a position vector of a curved surface coordinate system, Represents a basal basis function, Represents a control point. CP = the total number of control points]Acquiring a Nurib basis function using the NURBS basis function; And using the obtained NLBF and the control point,
[S represents the specified NURBS surface,
And Represents surface coordinates]To define the NURBS surface.
In the geometrically rigid isometric geometric design sensitivity sensitivity analysis method according to the present invention, the step of analyzing the curved surface may include the step of: ≪ / RTI >
[
Represents the response coefficient of the control point, and d represents the displacement]To obtain the displacement.
In the geometrically rigorous isometric geometric design sensitivity analysis method according to the present invention, the step of analyzing the design sensitivity of the curved surface shape may be performed by the design sensitivity analysis unit using the position vector of the curved surface coordinate system and / Using the position vector of the neutral plane of the shell,
[x represents the position vector of the curved coordinate system,
Represents the position vector of the neutral plane of the shell, Represents the unit normal vector for a given plane, Represents the thickness coordinate of the shell]Obtaining a unit normal vector for a given plane; Using the NURBS basis function, the design change amount of the control point, and the unit normal vector, the following equations
[V represents the design speed field,
Represents the design variation of the control point]Acquiring a design speed field by means of a control unit; And using the velocity fields and displacements,
[z represents displacement,
Represents the amount of change in the shape of the design variable direction, Represents the design sensitivity of the displacement field]To obtain the design sensitivity of the displacement field.
According to the geometrically rigorous geometric isometric geometric design sensitivity analysis method of the present invention, a generalized surface coordinate system is generated by using input NURBS data, and an iso geometric analysis is performed using the generated generalized surface coordinate system In the sensitivity analysis of a curved surface design of a curved surface structure, it is possible to obtain accurate and continuous curved surface normals and normals in boundary integrations expressing the boundary conditions of a curved surface structure, (Curvature or the like) of the shape-design sensitivity can be obtained.
1 is a control block diagram of an apparatus for performing a geometrically rigorous isothiometric curved surface design sensitivity analysis method according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining a geometrically rigorous isothiometric curved shape design sensitivity analysis method according to an embodiment of the present invention.
3 is a diagram showing a change in the domain of a shell.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is a control block diagram of an apparatus for performing a geometrically rigorous isothiometric curved surface design sensitivity analysis method according to an embodiment of the present invention.
As shown in FIG. 1, an apparatus for performing a geometrically rigorous geometric shape design sensitivity analysis method according to an embodiment of the present invention includes a NURBS
The NURBS
The curved surface coordinate
The iso-geometric analysis
The curved
The design
The NURBS
A geometrically rigid isothiometric curved surface design sensitivity sensitivity analysis method using the apparatus according to an embodiment of the present invention will be described.
FIG. 2 is a flow chart for explaining a geometrically rigorous isothiometrical curved surface design sensitivity sensitivity analysis method according to an embodiment of the present invention, where S denotes a step.
First, the NURBS data is input from the NURBS
In step S20, the curved surface coordinate
The covariance base vector (
) (≪ RTI ID = 0.0 > ). Covalent base vectors are not necessarily orthogonal to each other, and covalent base vectors ( ) Is the relationship between common base vector pairs ). Then, the inner product of the other basis vectors and the covariance / semi-basis vectors defines a useful metric coefficient as shown in the following equation (1).
The determinant of the inner product is expressed as a Jacobian matrix < RTI ID = 0.0 >
≪ / RTI >
Since the basis vectors are no longer constant and their derivatives need not be considered, the derivatives in the surface coordinate system are more complex than the Cartesian coordinate system. To represent the partial derivative of the basis vectors, a second cristopel symbol is introduced as: < EMI ID = 3.0 >
Has a covariance of the basis vector as shown in the following Equation (4).
The surface area of this constant differential parallelepiped surface ). The tangent curves are plotted on a coordinate curve ( ) ( ≪ / RTI > Is constant. therefore Silver surface ( ). Similarly on other surfaces, And Respectively. Surface area ( ) Is calculated in accordance with the following equation (5), and the same is true in the other aspects.
The volume of the differential parallelepiped body (
) ≪ / RTI >
Note that the regular orthogonal coordinate system can be obtained by the following equation (7).
Thereafter, in step S30, the ice geometric analysis
[here,
Represents a covariance basis vector of a curved surface coordinate system, x represents a position vector of a curved surface coordinate system, Represents a basal basis function, Represents a control point. CP = the total number of control points]The iso-geometric analytical
[S represents the specified NURBS surface,
And Represents surface coordinates]The process of obtaining Equation (9) will be described in detail as follows.
First, the coordinates in the parametric space (
) Is a set of knot vectors in a one-dimensional space as follows.
[Where p and m represent the order and number of basis functions, respectively]
If the knots are equally spaced in the parametric space, they are called uniform knot vectors, otherwise they are uneven knot backers. The knots are repeated when the knots are repeated at the same coordinates, and the knots are opened when the end knots are repeated ( p +1) times. The B-spline basis functions are recursively defined as: < EMI ID = 11.0 >
Note that denominators with knot differences can be zero (in the case of repeated knots). In this case, the quotient is assumed to be zero. The B-spline has the desired characteristics as a basis function as shown in the following Equation (13).
The NURBS curves are based on the glass basis functions (
) And corresponding control points ( ). ≪ / RTI > The p -order B-spline basis function ( ) And the corresponding m pairs of corresponding (projecting) control points, the Nurbsc curve is represented by a single parametric coordinate ( ).
In Equation (14), the following equations (15), (16) and (17) are derived.
Points in the three-dimensional Euclidean space (d = 3)
), For example, the homogeneous coordinates in the four-dimensional space , ≪ / RTI > ). The same weight ( ) Is used, the NURBS curve becomes a B-spline curve. Using the tensor product of the coordinates, the NURBS planes are defined by the following equation (18).
Expression (18) is concisely expressed to derive Equation (9).
In step S40, the curved
Obtain displacement (d). The displacement d may be expressed by Equation (20).
Subsequently, in step S50, the design
[x represents the position vector of the curved coordinate system,
Represents the position vector of the neutral plane of the shell, Represents the unit normal vector for a given plane, Represents the thickness coordinate of the shell]The unit normal vector (< RTI ID = 0.0 >
),The design
[V represents the design speed field,
Represents the design variation of the control point]To obtain a design speed field (V)
The design
[z represents displacement,
Represents the amount of change in the shape of the design variable direction, Represents the design sensitivity of the displacement field]Design sensitivity of the displacement field by
).In Equation 24,
Represents the partial differentiation of the displacement z, and is expressed by the following equation 25
.
In Equation 25,
, , ) ≪ RTI ID = 0.0 >
[d 'represents the partial differential of the displacement (d =)
Lt; / RTI > And Indicates that the explicit change condition with the dependence of the argument on the shape design parameter is suppressed)And the remaining components in Equation 25 are calculated from NURBS data and the drawing information in FIG.
In Equation 24, the convection term (
) ≪ RTI ID = 0.0 >
Lt; / RTI >
On the other hand, the performance measurements of the shell structure are generally defined in the neutral plane,
As shown in Fig.
The first-order change with respect to the shape design parameter is derived as the following equation (29)
Here, the following Equation 30
, The material differential of the determinant of the Jacobian matrix is given by the following equation 31
.
The acquisition process of Equation (26) will be described in detail as follows.
First, considering the first-order change of the biaxial strain energy form and the linear load form with respect to the shape design parameter, the following equations (32) and
.
Here, the following facts (
) Is used to obtain the shape sensitivity equation (Equation 26).Here, Equation 34
And Equation 35
.
Referring to Equation (35), the following boundary integral equation expressing the boundary condition of the curved surface structure
And The normal of the continuous surface ( ), The spatial differential of the normal (curvature, etc.) ( ), It can be seen that a precise shape design sensitivity analysis result can be obtained.
According to the geometrically rigorous geometric shape design sensitivity analysis method according to the embodiment of the present invention, a generalized surface coordinate system is generated using input Nurbst data, and an iso geometric analysis is performed using the generated generalized surface coordinate system In the sensitivity analysis of a curved surface design of a curved surface structure, it is possible to obtain accurate and continuous curved surface normals and normals in boundary integrations expressing the boundary conditions of a curved surface structure, (Curvature, etc.) of the geometric design can be obtained.
Although the best mode has been shown and described in the drawings and specification, certain terminology has been used for the purpose of describing the embodiments of the invention and is not intended to be limiting or to limit the scope of the invention described in the claims. It is not. Therefore, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.
100: NURBS data input unit 200: Curved surface coordinate system generating unit
300: Isothermometric analysis model normalization section
400: Surface analysis unit 500: Design sensitivity analysis unit
Claims (5)
Inputting NURBS data by a NURBS data input unit;
Generating a generalized curved surface coordinate system using the input NURBS data in a curved surface coordinate system generating unit;
Normalizing the isothiometry analysis model by the iso geometry analysis model normalization unit using the generated generalized curved surface coordinate system;
Analyzing the geometrically rigid curved surface by the curved surface analyzing unit using the normalized iso-geometric analytical model; And
And analyzing the design sensitivity of the curved surface shape by the design sensitivity analysis unit using the analyzed information of the curved surface,
The generalized curved surface coordinate system generation step may include:
Transforming a position vector in an orthogonal coordinate system having a control point and a fixed base vector of the Nursk data into a position vector of a curved surface coordinate system;
Obtaining a covariance basis vector of the surface coordinate system;
Wherein the step of normalizing the isomorphic analytical model is performed by the isomorphic analytical model normalization section,
From the covariance base vector, the following equation
[here, Represents a covariance basis vector of a curved surface coordinate system, x represents a position vector of a curved surface coordinate system, Represents a basal basis function, Represents a control point. CP = the total number of control points]
To obtain a baseband function,
Using the obtained NLBF and the control point, the following equation
[S represents the specified NURBS surface, And Represents surface coordinates]
And defining a surface of the NURBS by the method.
The step of analyzing the curved surface may include:
Using the Nursing basis function and the response coefficient of the control point,
[ Represents the response coefficient of the control point, and d represents the displacement]
And obtaining a displacement by means of the first and second sensors.
The step of analyzing the design sensitivity of the curved surface shape may include:
Using the position vector of the curved surface coordinate system and the position vector of the neutral plane of the shell,
[x represents the position vector of the curved coordinate system, Represents the position vector of the neutral plane of the shell, Represents the unit normal vector for a given plane, Represents the thickness coordinate of the shell]
Obtaining a unit normal vector for a given plane;
Using the NURBS basis function, the design change amount of the control point, and the unit normal vector, the following equations
,
[V represents the design speed field, Represents the design variation of the control point]
Acquiring a design speed field by means of a control unit; And
Using the velocity fields and displacements,
[z represents displacement, Represents the amount of change in the shape of the design variable direction, Represents the design sensitivity of the displacement field]
And obtaining a design sensitivity of the displacement field by the second step.
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CN107563016A (en) * | 2017-08-15 | 2018-01-09 | 西北工业大学 | A kind of wing box section Parameter Sensitivity Analysis method based on ellipsoidal model |
CN108763658A (en) * | 2018-05-07 | 2018-11-06 | 长安大学 | Based on etc. methods of geometry combination thin-wall construction intrinsic frequency design method |
CN112419254A (en) * | 2020-11-16 | 2021-02-26 | 重庆长安汽车股份有限公司 | Method for analyzing visual continuity among uniform parting curved surfaces based on human visual limit |
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Cited By (6)
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CN107563016A (en) * | 2017-08-15 | 2018-01-09 | 西北工业大学 | A kind of wing box section Parameter Sensitivity Analysis method based on ellipsoidal model |
CN107563016B (en) * | 2017-08-15 | 2020-07-21 | 西北工业大学 | Method for analyzing sensitivity of structural parameters of wing box of wing based on ellipsoid model |
CN108763658A (en) * | 2018-05-07 | 2018-11-06 | 长安大学 | Based on etc. methods of geometry combination thin-wall construction intrinsic frequency design method |
CN108763658B (en) * | 2018-05-07 | 2022-05-20 | 长安大学 | Combined thin-wall structure natural frequency design method based on isogeometric method |
CN112419254A (en) * | 2020-11-16 | 2021-02-26 | 重庆长安汽车股份有限公司 | Method for analyzing visual continuity among uniform parting curved surfaces based on human visual limit |
CN112419254B (en) * | 2020-11-16 | 2024-02-09 | 重庆长安汽车股份有限公司 | Method for analyzing visual sense continuous sense between uniform parting curved surfaces based on human eye visual limit |
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