N. Majic

Stiffening of sheet metal with failure-free bead patterns

In this study, the methodology of ManuBeadOpt (Manufacturing based Bead Optimization) including new functionalities for a failure-free based bead optimization of sheet metal is presented. The objective of this optimization strategy is to design automatically a beaded sheet metal which is both optimal for stiffness and manufacturing. In this context, shape optimization is combined with a forming simulation based on an inverse approach to evaluate formability. Two types of shape optimization methods are considered: A bead optimization until failure identification and a shape optimization with local modifications to guarantee failure-free geometries. So, this optimization tool makes an important contribution considering manufacturing aspects in bead optimization processes. Hence, product development cycles can be reduced by increasing quality of beaded sheet metal components. As example, a flat round plate as initial geometry is used to demonstrate the new iterative procedure of ManuBeadOpt.Copyright

Development and statistical evaluation of manufacturing-oriented bead patterns

There is an increasing interest of combining multiple software disciplines using in different engineering design stages in order to reduce product development cycles. In this paper a new function is presented to design manufacturing-oriented FEM-based bead cross-sections. This function is implemented in the commercial optimization tool TOSCA Structure.bead. A simple round plate is used for the algorithm verification. This function allows an improved controlling functionality to consider manufacturing aspects when designing sheet metal with beads. In this context, Optimus as process optimization tool is used to build up an automated multi-disciplinary simulation chain performing a Design of Experiments (DoEs) which involves a bead generation for sheet metal stiffening and a one-step inverse forming simulation for formability verification. A first application is shown with an oil pan geometry as real-world example. The main conclusion is that larger bead widths improve the manufacturability, but leads to less optimal designs regarding stiffness.

Automated Bead Design Considering Production Constraints

For design of stiff and lightweight sheet metal parts different construction methods are practicable. One important is weight neutral stiffness increasing using beads. Mostly empiric guidelines are used for designing bead structures until now. Alternatively rudiment simulation based methods for optimizing bead structures exist. But they do not consider production constraints such as formability or forming history. Users have to interpret optimizing results and have to transfer them into forming tools. Thus stiffness properties can be easily changed in a wrong way. Within the framework of a research project funded by the Deutsche Forschungsgemeinschaft a new method for automated design of bead structures considering production constraints, defined as ManuBeadOpt (Manufacturing based Bead Optimization), is developed. The methods substantial goal is linking forming simulation (based on inverse approach) and bead optimization to generate iteratively an optimal production-oriented bead structure. Therefore a forming tool based on the Nakazima-experiment for determining forming limit curves has been developed where punch is scaled on 400 mm diameter. Depending on this punch diameter a selected preformed area on pole of test pieces will be used for bead punching. Thereby specific strain allocations are possible, which accordingly affect the final test piece geometry. Afterwards the beaded area will be blanked and tested concerning stiffness behavior depending on bending, torsion and shear load cases. So relations between forming history, bead geometry, bead depth, stiffness, tool parameters, etc. will be identified. This knowledge is integrated in ManuBeadOpt for automatic evaluation of manufacturing. Tool, experimental and simulation results as well as the optimization method ManuBeadOpt will be shown.