Smart Systems for Enhanced Integrity of Existing and Future Structures
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Smart Systems for Enhanced Integrity of Existing and Future Structures Christian Boller The University of Sheffield, Department of Mechanical Engineering, Sheffield S1 3JD, UK [email protected]
ABSTRACT Ageing is a general problem also applicable in engineering. Many of our engineering structures are seemingly built ageless. Others were built with higher safety factors to cope with the lack of engineering knowledge at the time, where enhanced knowledge nowadays allows these structures to be used longer than initially anticipated. Consequently new design principles may allow future structures to be further built lighter weight. Much of this enhancement can result from the implementation of smart systems technologies into design. This paper will give a few examples based on integrated sensing as well as actuation principles into structures. INTRODUCTION Many of our engineering structures have been designed with no specific end of life. A good example is civil infrastructure, where people even use the word ‘ageless’. Experience however shows that any engineering structure degrades and the fiction of ‘ageless’ can only be met by a continuously increasing maintenance effort. Another example is transportation vehicles, which are designed for a defined life but also for a specific operation. As soon as this operation may change or the operator decides to use the vehicle longer than anticipated a problem emerges as to which the new operating conditions may either expand or shorten operational life. A similar problem may also exist with heavy machines, although their operational conditions will not change as dramatic but the high investment cost may drive the operator to expand the machines’ operational life if possible. All these changes in operational conditions are associated with uncertainties due to lack of information which have to be covered by increased safety factors resulting in lower allowable stresses and thus higher weight. With sensing technology however emerging at highly exciting speed there is a true opportunity to get the gap in lack of structural information versus maximum structural performance possibly significantly reduced. This opportunity is the motivation which has triggered a current boom in the field of structural health monitoring (SHM) [1-3]. A further look into structural design shows that design quality very much depends on factors such as: • knowledge of the loads applied to the structure, • structural material used with respect to the material’s endurance and the damage mechanisms generated, combined with the means on how to detect the material’s integrity based on non-destructive testing (NDT) technologies applied, • analytical tools that allow structural damage to be assessed. These factors are summarised in figure 1 and the question to be raised is now: What measures can be taken to improve those factors? Principally this question is answered through provision of more useful information and in practical terms this can mean to implement sensors into a structure to pro
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