Integration of functional materials

The aim of this project is to integrate functional elements, like sensors or piezo stack actuators, in load-bearing structures by rotary swaging. This cold forming technique is an incremental process, whereby the net shape of a part is reached in many small forming steps. Four oscillating tools reduce the diameter of a tubular work piece with alternating strokes. The demand for a flexible outer contour of the processed tubular parts requires an adapted process control and the utilization of mandrels.

Motivation

Uncertainty in load-bearing structures is present in the design, production and utilization phase of machine elements. An approach to control this uncertainty is to equip mechanical structures with additional functional elements like sensors, actuators and required periphery. In order to allow a wide-spread utilization, there is a need for cost-efficient large-scale production processes which allow a safe coupling of brittle and sensitive functional elements simultaneously to the forming of the part.

[1] Integrated functional elements a) Piezoelectric stack actuator, b) strain-gauge based sensor element

Approach

An effective utilization of the functional compound requires the elements to lie in the path of forces which is ensured by an axial pretension. By this, the functional structure is able to detect tensile forces by an integrated sensor in a wide range. This pretension is generated by a directed material flow on the end caps which lead to compression forces inside the functional element. The mechanisms and influencing factors in this process are investigated experimentally and numerically by finite element analysis. In order to set up the targeted pretensions experimentally, the integrated sensory elements itself can be utilized during the forming process. For this, a telemetry unit is attached to the rotating work piece (Figure [2]).

Picture: PtU Bildarchiv
[2] Setup of the rotary swaging machine with attached telemetry system

Acknowledgements

The authors want to express their gratitude to the DFG (Deutsche Forschungsgemeinschaft) for the support of the subproject “Integration of Functional Materials” within the Collaborative Research Centre 805.

German Resear ch Foundation