ABSTRACT
The detection of defects and the characterization of material properties without affecting the integrity of the material or structure require the use of nondestructive testing (NDT) or nondestructive evaluation (NDE) methods. Increasingly, during service and in the field at real or near real time, nondestructive health monitoring (HM) methods are used to monitor the health of structures or determine various properties. Common NDT and NDE methods include ultrasonic, thermal, magnetic-particle, liquid penetrant, radiographic, visual inspection, eddy-current testing, and laser interferometry. These methods are widely used in industry, mechanical engineering, electrical engineering, civil engineering, systems engineering, aeronautical engineering, medicine, and even in art. Just like monitoring the health of our body, it is essential to monitor and control the material properties and integrity of critical structures at all stages of life, from cradle to retirement. A typical HM system consists of a sensor, data acquisition system, control computer or microprocessor, and software (embedded or otherwise) for analysis. While most NDE methods are applied at room temperatures, the HM methods of high-temperature materials and mechanisms need to be applied at the relevant temperatures.
