Multi-level design process for 3-D preform shape optimization in metal forming

In this paper, a 3-D preform shape optimization method for the forging process using the reduced basis technique is developed. Several critical techniques and new advances that enable the use of the reduced basis technique are presented. The primary objective is to reduce the enormous number of design variables required to define the 3-D preform shape. The reduced basis technique is a weighted combination of several trial shapes to find the best combination using the weights for each billet shape as the design variables. A multi-level design process is developed to find suitable basis shapes or trial shapes at each level that can be used in the reduced basis technique. Each level is treated as a separate optimization problem until the required objective – minimum strain variance and complete die fill – is achieved. Excess material, or the flash, is predetermined as per industry requirements and the process is started with geometrically simple basis shapes that are defined by their shape co-ordinates. This method is demonstrated on the preform shape optimization of a geometrically complex 3-D steering link.