Search Results

The work describes an approach for a closer interface between product design and manufacturing. Starting from the part print a finite element model of the final part is constructed. The model is used for a one step unfolding of the part to determine the blank shape. In addition, by tracking the shape of the material “finite” elements before and under unfolding, the approximate forming severity of the stamping can be obtained. The one step unfolding solution also provides the thickness distribution together with the yield stress distribution in the stamped part. This information is of great value to product design for the performance of a more realistic fatigue analysis. Since during product design many design alternatives are to be evaluated, the finite element formulation used at this stage is based on a one step approach, with the emphasis on solution speed as opposed to exactness.

The paper describes some advances in the use of grid analysis and forming limit diagram techniques. It is shown that a limited amount of process or tooling related information can be derived from the measurements of the grid distortion at localized areas. It is illustrated that a full three dimensional grid analysis of the part is required for a comprehensive understanding of the interrelation between the state of deformation at different regions and the possible improvement in process.

The theme of this work is the interaction of the part geometry, material properties, forming severity and tooling design for box-shaped stampings. It is shown that the forming severity decreases with the increase of material normal anisotropy and corner radius. The lower the material normal anisotropy, the larger are the required tooling clearances and the thickening of the material under the blankholder. Understanding these relationships is of primary importance in applications requiring a major change in material properties, such as cold-rolled to hot-rolled conversion of products, or product shape redesign. The work also introduces a new type of idealization to metal forming problems. Beside the traditional continuum mechanics axisymmetric and plane strain idealizations, the work introduces the “corner analysis” approximation.

The paper describes a system currently under development, intended to be the spine for organizing an open-ended knowledge-based system for stampings within the sheet metal industry. The system is designed for those not necessarily expert in plasticity and strain theory, as well as applications where lead time is of prime importance. The objectives of the system are to develop: i a common vocabulary for BASIC SHAPES and DEFORMATION MODES ii an open-ended filing system for the organization of the knowledge i.e. the documentation of solutions and procedures used, as well as assessing historical data iii a procedure for deriving the FIRST FORM SHAPE and the number of forming stages and iv a system for the assessment of forming severity, force and energy calculations, material selection, tribological requirements and process planning.