CN-121999172-A - Automatic reconstruction method and system for isogeometric topological optimization result editable model

CN121999172ACN 121999172 ACN121999172 ACN 121999172ACN-121999172-A

Abstract

The invention discloses an automatic reconstruction method and system of an isogeometric topological optimization result editable model, wherein the method comprises the following steps of obtaining the isogeometric topological optimization result to obtain hypersurface model data; extracting contour lines of each layer in a layered manner according to a set density threshold, arranging seed points through the contour lines, dividing a background tetrahedron grid, searching the grid edges crossing the density threshold in depth, judging the corresponding relation among the contour lines, executing different reconstruction strategies according to different corresponding relations, generating NURBS curved surfaces by using an automatic skin technology and an adaptive fitting technology respectively, identifying the contour lines at the opening, determining the position relation between a cut area and each contour line, executing cutting operation to obtain a cutting curved surface, integrating the NURBS curved surfaces and the cutting curved surfaces, and outputting editable entities. The invention effectively reduces the complexity of extracting the equivalent surface of the optimized result, effectively improves the precision of the result model, and has the advantage of being editable and modifiable.

Inventors

WANG YINGJUN
YANG JIANGHONG

Assignees

华南理工大学

Dates

Publication Date: 20260508
Application Date: 20251216

Claims (10)

1. The automatic reconstruction method of the model with the editable isogeometric topological optimization result is characterized by comprising the following steps of: Obtaining an isogeometric topological optimization result to obtain hypersurface model data; Layering and extracting contour lines of each layer according to a set density threshold value; Arranging seed points through contour lines, distributing grids along the seed points, dividing a background tetrahedron grid, solving the density value of each grid vertex, and deeply searching grid edges crossing a density threshold value; Judging the corresponding relation among the contour lines, wherein the corresponding relation is divided into a one-to-one relation and an X-to-many relation, and executing different reconstruction strategies according to different corresponding relations; generating NURBS curved surfaces on contour lines in one-to-one relation by using an automatic skin technology; generating NURBS curved surfaces on the contour lines of the X-to-multiple relations by using an adaptive fitting technology; Identifying contour lines at the opening, determining the position relation between the cut area and each contour line, and executing cutting operation to obtain a cutting curved surface; integrating the NURBS curved surface and the clipping curved surface, and outputting the editable entity.
2. The method for automatically reconstructing the model capable of editing the isogeometric topological optimization result according to claim 1, wherein the method for obtaining the isogeometric topological optimization result to obtain hypersurface model data specifically comprises the following steps: and taking the pseudo density of the isogeometric topological optimization result as the coordinate of one dimension higher than the original NURBS model to obtain the data of the hypersurface model.
3. The method for automatically reconstructing the isogeometric topological optimization result editable model according to claim 1, wherein the step of hierarchically extracting each layer of contour lines according to a set density threshold value comprises the following steps: Setting slice direction and layer number, extracting parameter surface in layers, taking set density threshold value as height as plane, and obtaining layered contour line data layer by using curved surface and plane intersection algorithm.
4. The method for automatically reconstructing the isogeometric topological optimization result editable model according to claim 1, wherein the depth search of the grid edges crossing the density threshold value specifically comprises the following steps: Starting from any contour vertex, searching adjacent crossing density threshold grid edges along the depth direction until all contour lines are traversed, connecting all contour lines through the density threshold grid edges, and grouping and distributing.
5. The method for automatically reconstructing an isogeometric topological optimization result editable model according to claim 1, wherein the one-to-one relationship comprises: the adjacent two layers of sections are respectively provided with a contour line, and the number of the deficit of the grid formed by crossing the grid edges of the density threshold value is 0.
6. The method for automatically reconstructing an isogeometric topological optimization result editable model according to claim 1, wherein the X-to-many relation comprises: the adjacent two layers of cross sections totally comprise more than two contour lines; The adjacent two layers of sections are respectively provided with a contour line, but the number of the deficiency of the grids formed by crossing the grid edges of the density threshold value is more than 0; One of the sections has two contour lines, and the other section has no contour line; one of the sections has a contour and the other section has no contour.
7. The method for automatically reconstructing the isogeometric topological optimization result editable model according to claim 1, wherein the automatic skin technique is used for generating the NURBS curved surface for the contour lines with one-to-one relationship, and the method specifically comprises the following steps: And (3) making a horizontal line through the center of gravity of the convex hull of the profile line, taking the intersection point of the horizontal line and the leftmost end of the profile line as a parameter starting point, uniformly carrying out parameterization on the profile line again by using a chord length parameterization technology, and executing a curved surface skin operation to obtain the NURBS curved surface.
8. The method for automatically reconstructing the isogeometric topological optimization result editable model according to claim 1, wherein the method for generating the NURBS curved surface by using an adaptive fitting technology on the contour line of the X-to-multiple relationship is specifically comprising: and obtaining an interlayer triangular mesh model by using an isosurface extraction algorithm, carrying out semi-regular quadrangle on the triangular mesh, taking quadrangle mesh partition as a guide, and fitting into a NURBS curved surface by using a least square method.
9. The method for automatically reconstructing an editable model of an isogeometric topological optimization result according to claim 1, wherein the method for automatically reconstructing an editable model of an isogeometric topological optimization result is characterized by identifying contour lines at an opening, determining a positional relationship between a cut-out area and each contour line, and performing a cutting operation to obtain a cut curved surface, and specifically comprises: And identifying the contour lines at the opening, judging the inner and outer relations of the contour lines by taking the contour lines as cutting curves and the surface with the same parameters as cutting surfaces, starting from the contour line at the outermost layer, taking the outer side of the contour line as a cutting area, and then taking the inner side of the contour line at the inner layer as a cutting area, alternately determining the position relation between the cutting area and each contour line, and executing cutting operation to obtain the cutting curved surface.
10. An automatic reconstruction system of an isogeometric topological optimization result editable model is characterized by being used for realizing the automatic reconstruction method of the isogeometric topological optimization result editable model according to any one of claims 1-9, and comprises an isogeometric topological optimization module, a contour line layering extraction module, a depth search module, a contour line corresponding relation extraction module, an automatic curved surface skin module, a self-adaptive curved surface fitting module, an open contour repair module and a result output module; the isogeometric topological optimization module is used for outputting an isogeometric topological optimization result to obtain hypersurface model data; The contour line layered extraction module is used for extracting contour lines of all layers in a layered manner according to a set density threshold value; The depth search module is used for arranging seed points through contour lines, distributing grids along the seed points, dividing a background tetrahedron grid, solving the density value of each grid vertex, and searching the grid edges crossing the density threshold in depth; The contour line corresponding relation extraction module is used for judging the corresponding relation among contour lines, wherein the corresponding relation is divided into a one-to-one relation and an X-to-many relation, and different reconstruction strategies are executed according to different corresponding relations; the automatic curved surface skin module is used for generating NURBS curved surfaces for contour lines in one-to-one relation by using an automatic skin technology; the self-adaptive surface fitting module is used for generating a NURBS surface by using a self-adaptive fitting technology on the contour line of the X-to-many relation; The open contour repairing module is used for identifying contour lines at the opening, determining the position relation between the cut area and each contour line, and executing cutting operation to obtain a cut curved surface; and the result output module is used for integrating the NURBS curved surface and the clipping curved surface and outputting an editable entity.

Description

Automatic reconstruction method and system for isogeometric topological optimization result editable model Technical Field The invention relates to the technical field of isogeometric topological optimization, in particular to an automatic reconstruction method and an automatic reconstruction system for an isogeometric topological optimization result editable model. Background In 2005 Hughes et al propose isogeometric analysis, as NURBS basis functions in CAD are used as shape functions, conversion errors caused by grid approximation in the traditional CAE process are effectively eliminated, and the problem of model splitting of CAD and CAE is fundamentally solved. And the isogeometric analysis is applied to topology optimization, so that unified expression of a design model, an analysis model and an optimization model is realized. However, conventional isogeometric analysis results are represented by hypersurface, and because the optimization results tend to be multi-branch structures, the output as an editable model is generally difficult. The traditional method is to obtain a triangular mesh of an optimization result through an isosurface extraction algorithm, and output the triangular mesh as an STL model. But the STL model is not editable and therefore loses flexibility. In addition, there is a method for generating a borderable model by extracting skeleton lines and lofting, but the method is limited to truss-like results, and curved surfaces at branches cannot be accurately constructed, so that the method has a large limitation. In order to solve the above problems, a reconstruction method suitable for all types of isogeometric topological optimization results is needed to realize automatic reconstruction of an editable model of the optimization results, so that the final optimization results can be directly edited in CAD software, and the design flexibility is improved. Disclosure of Invention In order to overcome the defects and shortcomings in the prior art, the invention provides an automatic reconstruction method and an automatic reconstruction system for an isophthalmia topology optimization result editable model, the invention firstly carries out layered contour extraction on the optimization result model, then automatically determines the corresponding relation of the contour, and the automatic curved surface skin or the self-adaptive curved surface fitting is used for reconstructing the curved surface according to different corresponding relations, and finally the curved surface is output as an editable boundary expression model, so that the problems that the traditional optimized result output model cannot be edited and has poor universality are solved, and meanwhile, the method has the characteristics of simplicity in operation, short processing time, high result precision, low occupied space and the like. In order to achieve the above purpose, the present invention adopts the following technical scheme: the invention provides an automatic reconstruction method of an isophthalic topology optimization result editable model, which comprises the following steps: Obtaining an isogeometric topological optimization result to obtain hypersurface model data; Layering and extracting contour lines of each layer according to a set density threshold value; Arranging seed points through contour lines, distributing grids along the seed points, dividing a background tetrahedron grid, solving the density value of each grid vertex, and deeply searching grid edges crossing a density threshold value; Judging the corresponding relation among the contour lines, wherein the corresponding relation is divided into a one-to-one relation and an X-to-many relation, and executing different reconstruction strategies according to different corresponding relations; generating NURBS curved surfaces on contour lines in one-to-one relation by using an automatic skin technology; generating NURBS curved surfaces on the contour lines of the X-to-multiple relations by using an adaptive fitting technology; Identifying contour lines at the opening, determining the position relation between the cut area and each contour line, and executing cutting operation to obtain a cutting curved surface; integrating the NURBS curved surface and the clipping curved surface, and outputting the editable entity. As a preferable technical scheme, the method for obtaining the hypersurface model data by obtaining the isogeometric topological optimization result specifically comprises the following steps: and taking the pseudo density of the isogeometric topological optimization result as the coordinate of one dimension higher than the original NURBS model to obtain the data of the hypersurface model. As an optimal technical scheme, the method for extracting the contour lines of each layer in a layering manner according to the set density threshold comprises the following steps: Setting slice direction and layer number, extracting parameter surface