Session: 05-01: Guided Waves I

Paper Number: 145488

145488 - Lamb Wave Mixing for Early Detection of Damage 

Abstract: 

Nonlinear ultrasonics enables detection of damage precursors because it is sensitive to material microstructure evolution. The material nonlinearity causes distortion of the waveform that is evident in the frequency spectrum. However, the distortion is small and often a challenge to detect. Therefore, researchers have sought ways to obtain a highly sensitive, reliable, and repeatable measurement. Mixing Lamb waves enables scanning reasonably large regions of interest in a plate. Using the fundamental Lamb wave modes at frequencies below the lowest cutoff is often preferred in NDE so that a single mode can be actuated. We propose to mix counter-propagating S0 and A0 Lamb waves in an aluminum plate. Frequency selection to obtain internally resonant secondary A0 waves at the difference frequency that propagate in the direction of the S0 waves is described. Transducer selection to predominantly generate S0 and A0 primary waves for structural health monitoring is also described. Nonlinear finite element analysis demonstrates the effect of the primary wave amplitudes on the secondary waves. Linear finite element analysis demonstrates the effect on the wavefield of fillets that reduce the plate width for fatigue testing. A laser Doppler vibrometer is used in the laboratory experiments to facilitate scanning the plate surface between the transducers. After all of the above considerations, signal processing is still critical, albeit straightforward. Results of ongoing experiments will be discussed.

Presenting Author: Cliff Lissenden Penn State

Presenting Author Biography: Cliff Lissenden is a professor of engineering science and mechanics at Penn State. He was the founding director of the Ben Franklin Center of Excellence in Structural Health Monitoring and is an ASME Fellow.

Authors:

Maryam Ghodousi Penn State
Hamidreza Afzalimir Penn State
Cliff Lissenden Penn State