Guided Waves Mode

This research project is related to the study of optical strain sensor based on fibre Bragg gratings (FBG) application for symmetric and antisymmetric elastic guided wave mode sensing and mode separation. Guided wave propagation phenomenon is utilised in Structural Health Monitoring (SHM) systems for damage detection and localisation problems. Damage in the structure is a source of changes in elastic wave propagation. Based on registered changes in wave propagation and its processing it is possible to detect and localise damage. Very often elastic waves are excited and sensed using piezoelectric transducers. In the case of elastic wave sensing optical strain sensors based on Bragg gratings (FBG) are utilised since some period of time The aim of this research project is study of FBG sensors sensitivity to symmetric and antisymmetric elastic wave modes and possibility of sensing the effects of interaction of these modes with damage in the structure (reflections, and especially mode conversions). Research will be related to the separation of symmetric and antisymmetric modes due to different placement of FBG sensors (top and bottom surface). Results related to wave sensing obtained by FBG sensors will be compared with results obtained by piezoelectric sensors taking in consideration the possibility of damage detection. Research will be also related to connection of elastic wave sensing techniques based on piezoelectric and FBG optical sensors in order to improve the effectiveness of damage detection method. Piezoelectric based elastic wave sensors are influenced by electromagnetic interferences induced during the elastic wave excitation by piezoelectric actuator. This may lead to problems with damage detection and localisation. Aim of the project will be the development and validation of the hybrid piezoelectric-fibre Bragg grating (PT-FBG) elastic wave sensing method.