Research On Heterogeneous Object Modeling Based On NURBS Method

Heterogeneous object refers to a solid component consisting of two or more primarymaterials (or pore spaces) distributed continuously or discontinuously within an object,which often shows multiple special performance. In order to obtain the excellent propertyof such novel material parts, efficient modeling methodology for complex heterogeneousobject is primary and crucial. NURBS (Non-Uniform Rational B-Spline) method which isthe main modeling method for industrial products is applied into the heterogeneous objectdesign in this paper. Heterogeneous object modeling design based on NURBS method isintroduced systematically. The creative contributions of this paper summarized as follows.1. According to the characteristic of heterogeneous NURBS object, NURBS material datastructure is presented which represents the point by homogeneous coordinates. Auniform modeling method for normal heterogeneous NURBS object is presented whichincludes three forms for heterogeneous NURBS curve, heterogeneous NURBS surfaceand heterogeneous NURBS object. Construction techniques and representationmethods for special heterogeneous NURBS object are introduced which includeheterogeneous line, heterogeneous circle, heterogeneous revolution object,heterogeneous cylinder object, heterogeneous cone object, heterogeneous sphere object,heterogeneous extruded object, heterogeneous general cylinder object, heterogeneouslinear interpolated object, heterogeneous sweeping object, heterogeneous swung object,heterogeneous Coons object. All the key elements in these heterogeneous NURBSexpressions are introduced in detail in terms of theory and practice.2. A layered integrating method for heterogeneous NURBS object is presented. Geometrymodel and material model are expressed in different forms and they could be integratedin one layer in the process of modeling to generate complex heterogeneous object. Withthis method, storage space of material model could be reduced, but it still keeps thecontinuity of material distribution and increase the diversity of material transition.3. Two inverse construction methods are presented to create heterogeneous NURBSobjects. Interpolated method of tensor product is fit for the discrete points which aredistributed in uniform rectangular grid layers. RBF-NURBS inverse constructionmethod is fit for the discrete points which are distributed irregularly and randomly.4. A practical and multifunctional computer aided design software system is developedwhich is named as NURBS-HO-CAD. In this system, heterogeneous object could bedesigned by “one step method” or “two steps method”, and could be saved and open indifferent ways. Data exchange between NURBS-HO-CAD and other normalCAD/CAM system is realized in this novel system.