The Influence of Periodic Arrangement of Structural Geometry to Ultrasonic Waves

Abstract

In the current practice, the structural design and the damage detection methods are studied separately. However, the design can be integrated with the damage detection philosophy such that we can predict the damage presence through damage-induced imperfection in the design variables. New design approach is based on the placement of periodic subsystems, which have repetitive behavior from one subsystem (i.e. unit cell) to another. As each unit cell has the same geometric and materials properties, their frequency responses have similar characteristics until damage starts to form in a unit cell where the periodic behavior is modified. In this study, the periodic arrangements of different truss subsystems (used in bridges or tower designs) are studied using repetitive finite element approach. Their frequency responses are obtained for pristine condition and damage induced into different unit cells. The changes in the ultrasonic properties of each unit cell as functions of damage state are numerically and experimentally studied. The influences of non-periodic and period arrangements of truss systems to the ultrasonic wave are presented. It is shown that the periodic arrangement reduces the influence of boundary conditions to the frequency response of each subsystem, and the comparative approach of each unit cell behavior enables baseline-free damage detection approach.