A Study on Object Modeling for X-ray CT based Engineering

在本研究项目中，研究了基于x射线CT扫描仪的先进数字工程系统的建模方法。我们特别感兴趣的是从CT数据中生成三角形网格或其他形式的表面信息，这些信息可用于数字工程系统。这种网格生成的一种标准方法是所谓的“等距轮廓”方法。在这个为期2年的项目的第一年，我们开发了一种方法来同时生成不同材料零件之间的边界表面。它可以应用于汽车发动机缸体等由铁和铝制成的机械部件。该方法是基于材料分割的三维图像分析和我们基于“匹配立方性”理论的创新轮廓方法。在第二年，我们专注于薄板结构的建模技术。重点研究了CT数据中内侧面的提取方法。中间表面对设计师设计薄板结构更有用。因此，从CT图像中提取它们的需求很大。我们的方法是将体积建模和网格建模相结合的混合方法。我们首先提取与中间表面相关的体素。然后我们应用我们的等高线算法生成一个三角形网格的中间表面。由于我们还可以提取薄板结构的边界表面，因此可以评估薄板的厚度分布。在我们的工业应用中，精度是相当重要的。我们设计和制造特定的样品（模型）来检查我们的内表面的准确性。我们的实验表明，中间面的精度与边界面的精度一样好。此外，我们正在解决焊接件的问题。薄板结构通常由几片薄板焊接而成。使用x射线CT，无法从图像中识别出这种焊接部分。然而，在数字工程应用中，焊接前每个单独部件的网格和有关焊接位置的信息很重要。因此，我们研究了一种将复杂焊接组件的CT数据分离到其各个部分的方法。虽然还存在一些难题，但对于典型的焊接件，我们已经取得了成功。少

In this research project, modeling methods to be used in advanced digital engineering systems based on X-ray CT scanner are investigated. Our particular interest is in generation of triangular meshes or other forms of surface information from CT data, which can be used in the digital engineering systems. One standard methods for this mesh generation is so-called "iso-contouring" method. In the first year of this 2 year project, we developed a method to generate boundary surfaces between different material parts simultaneously. It can be applied to such a mechanical part as automotive engine blocks which are made of iron and aluminum. This method is based on three dimensional image analysis for material segmentation and also on our innovative contouring method based on our "Matching Cubeablity" theory.In the second year, we were concentrated on modeling technologies for thin plate structures. Particularly we studied methods for extracting medial surface from CT data. A medial surface is … More useful for designers to design thin plate structures. So there is large demand to extract them from CT images. Our method is hybrid by combining volumetric modeling and mesh modeling. We first extract voxels which are related to the medial surface. Then we apply our contouring algorithm to generate a triangle mesh for the medial surface. Since we can also extract the boundary surface of the thin plate structure, thickness distribution of the thin plate can be evaluated. In our industrial applications, accuracy is rather important. We design and manufacture specific samples (phantom) to examine the accuracy of our medial surface. Our experiment shows that the accuracy of the medial surface is as good as that of the boundary surface.Furthermore we are working on the problem of welded parts. A thin plate structures are usually made of several pieces of thin plate which are welded together. Using X-ray CT, it is impossible to identify such welded part from the images. However, in digital engineering applications, meshes for each individual part before welding and information about the welding positions are important. So we studied a method to separate CT data of a complex welded assembly into its parts. Though there are still difficult problems, we have succeeded for typical welded parts. Less