Damage detection using finite element and laser operational deflection shapes

Damage detection can increase safety, extend serviceability, reduce maintenance costs, and define reduced operating limits for structures. Vibration-based methods are a new approach for damage detection and are more globally sensitive to damage than localized methods such as ultrasonic and eddy current methods. The interpretation of vibration responses to identify damage is dependent on the numbers and types of sensors and actuators used. One technique that is promising is the use of operational deflection shapes (ODS) for structural damage detection. The ODS are the actual vibration displacement or velocity patterns of a structure that is vibrating in the steady-state condition due to a specific structural loading. In this paper, the ODS are represented as summations of scaled mode shapes and it is demonstrated through finite-element simulations how the vibration excitation parameters can be chosen to aid in identifying structural damages. Generation of experimental ODS is performed using a scanning laser Doppler vibrometer and piezoceramic actuators, and examples of damage detection on a beam are presented.