中文摘要：

为了解决目前检索到的三维CAD模型难以重用的问题，提出一种针对Brep表示的cAD模型重用方法．首先提出一种自动识别B—rep模型中对称特征的算法，依据面的属性对B—rep模型所有的面进行排序，将具有相同属性的面分为一类，并通过不同类之间的合并形成B—rep模型中的对称特征，同时提取该对称特征的约束知识；然后交互式地定义Brep模型的其他特征，使Brep模型中的任一面都属于模型的某一特征（主形状特征或局部形状特征）；最后以B—rep模型的主形状特征为特征树的根节点，依据特征之间的邻接关系逐次递归地建立特征之间的依赖关系，并自动创建B—rep模型的特征树．与NX“同步建模方法进行比较的实验结果表明，文中方法利用模型高层次的设计知识重用已有模型，使模型在修改过程中始终保持原有的设计意图，在模型的重用过程中具有一定的优越性．

英文摘要：

The retrieved models are difficult to reuse in the current 3D model search. To solve this problem, a new method is proposed to reuse the CAD models represented by B-rep. An algorithm for automatically detecting the symmetry of B-rep model is first defined to reduce the feature interaction. The faces of the B-rep model are permuted based on their attributes. The identical faces are classified into different groups and groups are merged to produce symmetric features while the symmetric constraints are also obtained. Then the rest of features of the B-rep model are specified interactively. This makes all the faces of the B-rep model belong to a feature, primary feature or subsidiary feature. Finally the primary feature is taken as the root of feature tree. The dependent relationships between the features are detected and all the features are added to the feature tree iteratively. This feature tree, as the high level of design knowledge, is a robust way of reusing the existing CAD models. In the experiments, the method presented in this paper is compared with NXTM synchronous modeling method. Our method preserving the original design intent is better than the synchronous modeling in the process of reusing the retrieved model.