Definition Method On Geometrical Information Of Multi-State Model For Aircraft Sheet Metal Parts

The geometrical information definition of workpieces is a bridge connecting digital design to manufacturing for aircraft sheet metal parts. Multi-state model is the information model which is made up of correlated workpiece states orienting the whole manufacturing process. Multi-state model is an abbreviation of Manufacturing-Oriented Multi-State Model for Aircraft Sheet Metal Parts (MOSS). States are the backbone of data organization and management. With every state consisting of geometrical models and other information of a workpiece, MOSS can provide integrated and uniform data for digital manufacturing of sheet metal parts. Geometrical information of states is the key and core of MOSS.In this paper, research on the content, data structure and representation, transformation regulation, definition sequence and method of geometrical information of MOSS is done, which develops the theory of MOSS. It has four aspects in detail:(1) Orienting digital manufacturing of sheet metal parts, some typical manufacturing states and their geometrical information content are analyzed and given.(2) With analyzing structure features of sheet metal parts, the geometrical information model is built on the basis of the hierarchy of structure feature, structure element and geometrical element. The tree-based data structure is adopted to organize geometrical information, and geometrical information models of frame and rib, integral panel and skin parts are given separately. The variety of structure elements in state transformation and the impact of working procedure on structure elements are analyzed. And the transformation process of geometrical information is described with the weight graph. According to geometrical information model, XML (extensible Markup Language) representation is proposed, with XML Schema of sheet metal structure features being built and geometrical information in different layers being expressed in XML.(3) The loop of states division, geometrical information definition and state model examination is applied to the solution of multi-state model. With analysis of relations between manufacturing states, the flowchart of defining geometrical information of multi-state model is proposed. To define the workpiece forming state, forming process-oriented design method of structure elements and springback correcting approach of straight flange are given. To define the intermediate workpiece state and the...