Exploiting Microstructural Evolution for Material and Damage State Sensing

The objective of this project is to develop a multi-purpose combination type optical fiber sensor that enables simultaneous sensing of microstructural evolutions in the sensor materials and the environmental conditions such as pressure and temperature. It is very well known that materials subjected to fatigue and high temperature will go through microstructural changes such as plastic deformation, grain coarsen, precipitation generation, phase transition, and surface roughening. While extensive researches have been conducted to develop non-destructive detection techniques to measure these microstructural changes using ultrasonic wave, most of these techniques excite acoustic wave in the service components directly and therefore require high power excitation sources and bulky detection units. To overcome these difficulties, the proposed sensor measures the microstructural changes of a sensor material that is subjected to the same operational conditions as the service components do. The microstructural evolution of the sensor material is then used to interrogate the damage state of the service components. The proposed sensor is a stand-alone sensor probe combining laser-acoustic, laser scattering, and optical fiber interferometric sensing techniques to measure the material microstructure. In addition to its capability to measure multiple physical parameters simultaneously, the optical fiber sensor also has the advantages of being compact, lightweight, remotely operational, capable of operating in harsh environments, and immune to electro-magnetic interference.