image (67)

where ξ*image is a real number. To understand the meaning of Eq. (67), let us substitute it into the general expression Eq. (34); we get

uz(x,y,t)=h(y)ei(ξxωt)=h(y)ei(iξ*x)eiωt (68)

image (68)

i.e.,

uz(x,y,t)=[h(y)eξ*x]eiωt (69)

image (69)

Equation (69) describes an evanescent1 wave, which has a decaying amplitude and only exists close to the excitation ...

Get Structural Health Monitoring with Piezoelectric Wafer Active Sensors, 2nd Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.