Abstract: It is difficult to obtain trimming line using traditional prediction methods for 3D complex parts. In order to solve this problem, an initial geometrical development method with element layer is proposed based on one step inverse analysis theory. The flange mesh can be unfold onto the die surface layer by layer according to nodal adjacent element relation, then the above development mesh is smoothed by mesh smoothing method with sliding constraint surface in order to delete overlap and distorted mesh, the 3D initial mesh can be obtained for one step inverse analysis method. The precision trimming line of 3D complex part can be obtained by plasticity iteration of one step inverse analysis. The trimming line of an example part with flange is predicted by this method, the initial blank with this trimming line is used flange forming simulation, the comparison errors between the simulated forming height and designed height meet requirement. Another typical real example part of trimming line prediction is selected to prove this method, the comparison results between the simulated and experimental values show that this method has enough precision and can handle complex parts, satisfies the engineering practical demands.

Key words: Mesh smoothing, One step inverse analysis, Sliding constraint surface, Trimming