Energy-Efficient Compliant Structures with Functional Spring-Damper-Characteristics

Prof. L. Zentner

On the one hand, vibrations and shock loads lead to dynamic stress surges, which can cause strength problems in devices, machines and systems. On the other hand, in certain technical systems, such as medical aids (prostheses) or handling systems, displacement- or speed-dependent defined transmission characteristics (spring-damper characteristics) are required at components or coupling points. For compensation and function adaptation (e.g. characteristic curve), increasingly complex automated spring-damper systems are currently being developed. In many cases, however, the desired characteristic can be achieved in whole or in part by the specific design of compliant structures.

For the development of the actuators, a model-based synthesis method was developed, which combines the finite element method and the analytical method. Scaling considerations performed showed that geometrically similar hollow cylindrical rods with embedded filament and with identical material and internal pressure achieved geometrically similar shape. This finding enabled the theoretical and experimental investigations to be carried out at an enlarged scale.

It could be demonstrated on two types of actuators (straight in the initial state and pre-curved actuators), that the desired deformations of the actuators can be achieved. This allowed the verification of the developed synthesis method. Furthermore, experimental insertion tests on the scaled cochlea model showed that the insertion forces acting on the cochlea during insertion can be reduced.

The aim of the project is to develop flexible structures with functional spring-damper properties that do not require any additional energy supply in order to adapt to changing operating and environmental conditions. To this end, classic spring materials, such as metals and plastics, are to be combined with intelligent materials (e.g. filled or encased). Novel, energy-efficient components are to be created in order to reduce the complexity, the required installation space, the weight and the high energy requirements of conventional systems. The structures to be developed adapt to different conditions in a purely mechanical and thus energy-efficient manner while maintaining a comparable performance profile. Basic principles are to be developed as to how adaptable structural behavior can be achieved through the use of functional materials with load-dependent properties (e.g. parameters of displacement, velocity or temperature) and a targeted geometric design. To realize the temperature-dependent properties, only parasitic (heat generation by friction) or peripheral energy sources (change of ambient temperature) are to be used. Demonstrators will be built and tested to prove the functional properties.

TU Ilmenau - Machine Elements Group

03/2015 - 12/2017

DFG - Deutsche Forschungsgemeinschaft ; Project: https://gepris.dfg.de/gepris/projekt/203302371
DFG - reference number: ZE 714/6-2