ON THE EFFICIENT EXCITATION OF SECOND HARMONIC GENERATION USING LAMB WAVE MODES.

This research experimentally characterizes an efficient Lamb wave mode pair that generates the cumulative second harmonic in an undamaged aluminum plate. It has been shown that inherent material nonlinearity will generate a second harmonic component in an originally monochromatic ultrasonic Lamb wave signal if certain conditions are satisfied, and the normalized second harmonic amplitude should increase with propagation distance. Previous research has identified five Lamb wave mode types exhibiting second harmonic generation (SHG) and theoretically compares the rate of accumulation of the second harmonic over propagation distance for each mode. This research experimentally investigates a new Lamb mode pair that has a higher rate of accumulation than those studied in the existing literature, and develops improved experimental techniques that can be applied to other modes for SHG measurements. [ABSTRACT FROM AUTHOR]