Design Rule Checker for Sheet MetalComponents using Medial Axis Transforms andGeometric
Design Rule Checker is an essential component of design automation and for making design, process planning and manufacturing concurrent. In this paper, a set of algorithms are presented for detecting design violations in sheet metal components. Violations in sheet metal components occur when holes, slots, or other features are too close to one another. These violations, if undetected during design, increase the design life cycle of the product. Thus it is very essential to detect, if not eliminate these violations at the early stages of design. Typically sheet metal components have a number of features serving various purposes which include ventilation and fastening. As the contour of the parts gets complicated and the number of features on the sheet metal part increases it is diicult to check the rules exhaustively as it may lead to combinatorial explosion. 1 The algorithm presented here, uses Medial axis transformation to decompose a given domain thus preventing a combinatorial explosion, and also provides a means to integrate the rule checker with a design adviser.
Voronoi Diagram for Multiply-Connected Polygonal Domains I: Algorithm
Voronoi diagrams of multiply-connected polygonal domains (polygons with holes) can be of use in computer-aided design. We describe a simple algorithm that computes such Voronoi diagrams in O(N(log
 2 N+H)) time, where N is the number of edges and H is the number of holes.
Microstructure of the solder-casting zone in bridges of dental gold alloys.
The composition and structure were studied in the cast and in the solder of bridges which had failed clinically. Both materials were gold alloys but with different contents of Pt, Ag and Zn. The metallographic investigation revealed defects mostly in the solder, situated in the subsurface layer. SEM studied of the fracture surface revealed large porosites and a structure of dense parallel lines--striations--, indicating that the material had failed from fatigue. The materials in the fractured bridges were identified by micro-probe measurements. It was stated that cast material and solder material used together, were of different composition.