Over the past decade, the significance of guided waves in structural health monitoring and remote inspection has increased manifold. There is a need for the development of structures, such as phononic crystals and metamaterials; which can manipulate guided waves in order to suit such applications. The MS thesis research that will be presented in this seminar is organized into two parts. The first part investigates the manipulation of ultrasonic guided waves for high temperature applications. To facilitate remote inspection using waveguide sensors, a conical transition profile is designed through numerical simulation studies. The objective of engineering such a profile is to enable the effective transfer of ultrasound from waveguide to the test material for thickness gauging. The feasibility of implementation of such a design is validated experimentally.
Part 2 of the work examines the manipulation of heat waves by using phononic structures known as Thermal Wave Crystals (TWCs). The TWC conceptualised in this work is made from Silicon and Germanium; materials commonly used in semiconductor devices. The objective is to implement TWC to induce bandgaps in the dispersion of thermal phonons, in the GHz range. Analytical formulations are used to study the variation of unit cell dimensions and their corresponding effect on the bandgap frequencies and bandwidth. The control of thermal waves using such crystals holds promise for better heat management solutions.