Affiliations: Structural Integrity Group, United Technologies
Research Center, East Hartford, CT 06108 (formerly National Research Council
Associate, NASA Langley Research Center, Hampton, VA, USA. E-mails:
anindo_ghoshal@yahoo.com or ghoshaa@utrc.utc.com | Naval Undersea Warfare Center, Newport, RI 02841,
USA. E-mail: MartinWN@Npt.NUWC.Navy.Mil | Associate. Department of Mechanical Engineering,
University of Cincinnati, OH 45221, USA. E-mail: mark.j.schulz@uc.edu | MS 231, NESB, 3B Taylor St, NASA Langley Research
Center, Hampton, VA 23681, USA. E-mail: William.H.Prosser@nasa.gov | Department of Mechanical Engineering and Aerospace
Engineering, Arizona State University, Tempe, AZ 85287, USA. E-mail:
aditi@asu.edu
Abstract: Two approaches used for monitoring the health of thin aerospace
structures are active interrogation and passive monitoring. The active
interrogation approach generates and receives diagnostic Lamb waves to detect
damage, while the passive monitoring technique listens for acoustic waves
caused by damage growth. For the application of both methods, it is necessary
to understand how Lamb waves propagate through a structure. In this paper, a
Physics-Based Model (PBM) using classical plate theory is developed to provide
a basic understanding of the actual physical process of asymmetric Lamb mode
wave generation and propagation in a plate. The closed-form model uses modal
superposition to simulate waves generated by piezoceramic patches and by
simulated acoustic emissions. The generation, propagation, reflection,
interference, and the sensing of the waves are represented in the model, but
damage is not explicitly modeled. The developed model is expected to be a
useful tool for the Structural Health Monitoring (SHM) community, particularly
for studying high frequency acoustic wave generation and propagation in lieu of
Finite Element models and other numerical models that require significant
computational resources. The PBM is capable of simulating many possible
scenarios including a variety of test cases, whereas experimental measurements
of all of the cases can be costly and time consuming. The model also
incorporates the sensor measurement effect, which is an important aspect in
damage detection. Continuous and array sensors are modeled, which are efficient
for measuring waves because of their distributed nature.
