Sensor placement technique using BaTiO3/epoxy resin piezoelectric composite sensors based on differential imaging method for damage detection in structural health monitoring

Abstract

Structural Health Monitoring (SHM) is an emerging technology in many engineering disciplines that aims at designing systems being able to continuously monitor ageing of structures throughout their life span. Damage monitoring using guided waves (GWs) is one promising approach in that regard. Principally a network of integrated piezoelectric transducer patches (actuators and sensors) on a structure generates GWs, where the GWs propagate through the structure and relative information about the damage is finally obtained. Based on damage mechanics principles and damage tolerance criteria, the structure’s remaining useful life is then be determined from the data recorded by the transducers and the need for structural maintenance actions can finally be derived accordingly. The detectability of the growing structural damage is highly dependent on the placement of actuators and sensors. This therefore requires an optimum placement of those transducers to be found, which is obtained through simulation. This need for simulation becomes specifically relevant when structures are large and complex. A new approach presented within the paper proposed has therefore been developed, which is based on differential imaging/signals, where the differential is determined from the difference of the wave patterns between an undamaged and a damaged condition. The resulting topology of the differential signal is considered to define the shape/pattern of the respective piezoelectric transducers, which will be placed on the structural component considered using a defined coating process. The coating and monitoring process applied using a BaTiO3/epoxy resin will be demonstrated on a thin aluminium test coupon with three holes where a crack of tolerable length has originated from one of the holes due to fatigue loading and the coated piezoelectric composite transducer pattern for monitoring the crack has been defined from the output of guided wave FEM simulations.