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Infrastructure Resilience Conference 2018

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Resilience of Load-Carrying Structures in Mechanical Engineering

Load-carrying structures in mechanical engineering have traditionally been developed for a given design point (e.g. a given load the structure should be able to sustain). In the last decades and in the course of many catastrophes and product recalls, however, researchers have realized that uncertainty is part of any application of a product and cannot be disregarded in the design of load-carrying structures. While designing structures which fulfill their purpose in a whole neighborhood of the design point, the so-called uncertainty set, already mitigates some of the uncertainty, the next logical step is to design resilient structures that can even cope with failures of components or other effects disregarded during design phase.

For this reason, in 2016, the German Research Foundation extended the collaborative research centre SFB 805 "Control of Uncertainty in Load-Carrying Structures in Mechanical Engineering" to a third funding period with "Methods and Technologies for Resilient Systems" being one of the main research topics. At SFB 805, researchers from the fields of mechanical engineering, mathematics and law work closely together in order to control uncertainty. Aim of the collaborative research centre is to combine methods and technologies from all stages of the product life – product development, manufacturing and usage phase – to design resilient structures.

In product development, design requirements for resilient systems need to be identified through vulnerability analyses. Furthermore, mathematical optimization methods can be applied to design resilient structures under consideration of failures. For example, mixed-integer programming can be used to plan the optimal layout of water supply systems for high operational resilience in different failure scenarios. Moreover, it is possible to design truss structures with minimal volume which can still sustain uncertain forces after failure of a given number of arbitrary bars. However, considering all possible failures in such optimization problems renders them practically unsolvable by current techniques, given realistic problem sizes. Therefore, new approaches need to be developed to dynamically generate and assess relevant failure scenarios during the optimization process and thus speed up the computation time.

In order to build up resilient production processes that integrate the resilience strategies monitoring, responding, learning and anticipating, new technologies need to be developed. One of these technologies investigated at SFB 805 is a sensor-integrated tapping tool. As a first step towards a resilient tapping process the tool monitors the occurring loads. The collection and a real time analysis of the recorded data enables the process not only to identify errors, but also to learn and anticipate recommended actions to prevent tool damage. The changes in the process parameters will then be automatically executed by the machine control. With this technology the narrow tolerances of the manufacturing process can be guaranteed under uncertainty and even under partial failures of the system (e.g. geometrical irregularities in the used tapping tool).

For controlling uncertainty during the usage phase of load-carrying structures, advanced mechatronic and adaptronic technologies are developed at SFB 805: Semi-active and active technologies such as buckling control, vibration attenuation and load path redistribution allow to react to disturbances, changes in environmental conditions or component failure. Above mentioned technologies can be combined into a demonstrator system which is inspired by an aircraft undercarriage. The resilience of this exemplary system can be investigated by comparing its performance with the developed technologies to the performance without them, given unexpected usage parameters.

In summary, by combining resilience-enhancing components optimally within systems and producing them through resilient process chains, further contributions to controlling uncertainty can be made. To measure this progress, specific metrics are established to compare systems and processes with regards to their resilience and their impact on controlling uncertainty. This tutorial will provide an overview of the research on resilient systems at SFB 805 and give application examples from the different stages of the product life.

Lena Altherr, Dr.-Ing.
Chair of Fluid Systems, Technische Universität Darmstadt
Germany

Peter Pelz, Prof. Dr.-Ing.
Chair of Fluid Systems, Technische Universität Darmstadt / Speaker Collaborative Research Centre 805
Germany

 

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