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Lightweight design is a key challenge to further reduce the worldwide greenhouse gas emissions. To be able to design lightweight concepts in a fast-changing environment, a stronger interlinking between engineering disciplines is required. Therefore, the generic and extendable method of component-oriented material design is postulated. In this method, not only the standardized material properties are considered during the development process, but rather the material properties tailored to the application (e.g., stress-state-dependent strain variable) and the component performance (e.g., energy absorption capacity) are formulated based on simulations as target variables within the material design process. The developed method’s potential was demon­strated for a lean medium manganese steel (MMnS) on the example of a b-pillar subjected to quasi-static loading in a side impact test. The results show that the designed MMnS exhibits better ductility properties (εkrit = 0,52) compared to the reference material 22MnB5 (εkrit = 0,17). The strength (Rp0.2 = 1049 MPa, Rm = 1404 MPa) is at similar level to that of the reference material. Subsequently, from the concluding numerical evaluation of the component performance, it is evident that the energy absorption potential of the b-pillar consisting of the developed steel could be significantly increased compared to the reference material.

In the last decades, the application of automatic control techniques in freeform bending processes was limited to the motion control of the bending die, i.e., the workpiece itself was not considered inside the closed-loop control system. In a previous work, a simple preliminary model for the workpiece was used as a foundation for developing a closed-loop system for freeform bending that includes both the geometry and the mechanical properties of the semi-finished product. However, this approach did not consider the fact that the same geometry can be reached by either over- or underbending the tube. In this work, the previously developed system model is extended to include this physical property of the system.

The superordinate goal of this study is to develop a closed-loop control for a property-controlled freeform bending process based on the prediction of the residual stresses and further mechanical properties by a soft sensor. Therefore, it is hypothesized that different combinations of freeform bending process parameters lead to matching geometry pairs with different residual stresses that can be influenced by the bending die position. A novel correlation between the bending die position, residual stresses and hardness provides the basis for the soft sensor and for closed-loop control design.This paper focuses on freeform bending with movable die, for which a novel bending strategy is developed that results in a set geometry while also providing various residual stress states in the tube. A numerical simulation model for freeform bending with movable die successfully models the variation in degrees of freedom of the machine and provides high qualitative and quantitative results regarding the identification of geometry and residual stresses. Real freeform bent validation experiments and HV 10 Vickers hardness measurements were carried out. HV 10 Vickers hardness tests were identified as a suitable parameter for preliminary system identification and validation, hence making it an appropriate parameter for soft sensor development.