IMECE 2008-66555 USE OF NONLINEAR VIBRATION FREQUENCIES AND ELECTRICAL CONDUCTIVITY MEASUREMENTS IN THE SEPARATION OF INTERNAL AND BOUNDARY DAMAGE IN STRUCTURES

ABSTRACT The paper addresses one of the key problems in structural health monitoring -how to separate defects, both microscopic and macroscopic, accumulated in structural members from damage in the joints and boundaries. It is suggested to use a simultaneous set of measurements -nonlinear vibration frequencies and electrical conductivities -to distinguish between three distinct types of defects. Nonlinearities occur as a result of breathing internal cracks and slapping in damaged joints. The use of proper orthogonal decomposition and a local equivalent linear stiffness method allows for model updating to account for the damage. The theory is presented for full threedimensional elastic solids and illustrated via the problem of a beam damaged both internally as well as at the boundaries