New Results in the Application of E/m Impedance Method to Machinery Health Monitoring and Failure Prevention

The electro-mechanical (E/M) impedance method for structural health monitoring, damage detection and failure prevention is a new technology utilizing the emitter-detector properties of active material sensors and the structural drive point mechanical impedance. In previous work, the authors showed that changes in the drive point mechanical impedance of a structure or machinery can be sensed in the form of changes in the apparent E/M impedance of the active material sensor. Subsequently, a number of situations have been considered for the use of E/M impedance method in conjunction with active material sensors to important health monitoring and failure prevention applications. The paper starts with a brief review of the electro-mechanical (E/M) impedance method for structural health monitoring and non-destructive evaluation. Experimental results from tests conducted on various pieces of structures and machinery are presented. The experimental set-up consisted of an HP 4194A impedance analyzer, Pentium computer, National Instruments data acquisition hardware and software, and an array of PZT active sensors. These proof-ofconcept demonstration experiments proved the suitability of the electromechanical (E/M) impedance method to a number of industrial applications. This paper brings together, in a unified format, a large body of knowledge that has been accumulated regarding the electro-mechanical (E/M) impedance method and indicates its suitability to failure prevention monitoring in complex machinery. The theoretical and practical issues posed by its further development and wide industrial applications are also addressed.