An approach for extracting non-manifold mid-surfaces of thin-wall solids using chordal axis transform

This paper proposes an approach for extracting non-manifold mid-surfaces of thin-wall solids using the chordal axis transform (CAT) (Prasad in CNLS Newsletter-Center for Nonlinear Studies, Los Alamos National Laboratory, vol 139, 1997). There is great demand for extracting mid-surfaces as it is used in dimension reduction. Quadros and Shimada previously used CAT in extracting 2-manifold mid-surfaces of a particular type of thin-wall solids. The proposed approach is an extension of the previous approach (Quadros and Shimada in 11th international meshing roundtable, 2002) in order to extract non-manifold mid-surfaces of general thin-wall solids. The three steps involved in extracting the mid-surface of a thin-wall solid are: (1) generating a tet mesh of a thin-wall solid without inserting interior nodes; (2) generating a raw mid-surface by smart cutting of tets; and (3) remeshing the raw mid-surface via smart clean-up. In the proposed approach, a discrete model (i.e., a tet mesh without any interior nodes) is used instead of working directly on a CAD model. The smart cutting of tets using CAT yields correct topology at the non-manifold region in the raw mid-surface. As the raw mid-surface is not directly suitable for engineering purposes, it is trimmed using a smart clean-up procedure and then remeshed. The proposed approach has been implemented using C++ in commercial ALGOR finite element analysis software. The proposed approach is computationally efficient and has shown effective results on industrial models.