Virtual sensors for the optimization of a SHM sensor network based on Lamb wave propagation

Abstract

The design of a sensor network is required for a successful SHM system applied to complex structures. The wave propagation can be very complex due to reflections, interferences or mode conversions. The knowledge of the wave behaviour is necessary for an optimal sensor configuration. An air-coupled scan technique in conjunction with data storage can be used for wave field recording. Such a volume data file consists of all digitalized amplitude values in the scanning time window for every scanning point. The wave propagation behaviour can be analysed from these data and visualized. Furthermore, it is possible to use the recorded wave field data for the calculation of a virtual sensor signal being recorded for a cohesive area. Such a virtual sensor with an arbitrary layout can be defined and selected by software. After setting its position within the scanning area a special algorithm calculates the sensor signal like a real sensor being bonded on the structural surface. The algorithm which is based on the Lamb wave theory considers material parameters of the specimen, different coupling techniques between recording and, calculation and different sensor behaviour. The method for the design and optimization of SHM network comprised of a number of sensors, their layout and position without additional experiments. The method delivers the sensor response and allows specification of damage detection algorithms.