Inspection of dissimilar metal-composite adhesive joint is a complex task, as the acoustic impedances
of the adherents differ, meaning that there will be strong reflection at the interface of two dissimilar materials even without defect in it -.
The acoustic impedance
(in Rayl/[m.sup.2] or ([lb.sub.f]/[ft.sup.2])/([ft.sup.3]/s)) relates the particle velocity ([??]) directed away from the source to the acoustic pressure ([??]) and can be expressed as
The condition of the acoustic microscopic analysis is the difference between the acoustic impedance
of the materials.
1, we applied the transfer matrix formalism combined with the annealing algorithm to design the optimum arrangement of 6 layers with different lengths and acoustic impedances
. The experimental data were plotted in the domain 20 Hz-200 Hz.
It is here noted that the amount of seismic energy transmitted or refracted in the earth is influenced by the acoustic impedance
contrast between the lithologic bed boundary.
As a longitudinal wave normally travels from medium 1 to medium 2 with acoustic impedances
[Z.sub.1] = [[rho].sub.1][V.sub.1] and [Z.sub.2] = [[rho].sub.2][V.sub.2], respectively, the wave is partially reflected and partly transmitted.
If, during its real-world application the AET measures, the wave of other type that propagates in a material with substantially different acoustic impedance
, then the transducer characteristics obtained during calibration are not comprehensive enough.
Goran, "Influence of ultrasonic transducer acoustic impedances
and dimensions on its input electrical impedance," Working and Living Environmental Protection, vol.
This is caused by the higher acoustic impedance
in sclerotic bone since acoustic impedance
is directly related to density that increases in sclerosis .
The electromechanical coupling coefficient, kt, in the thickness direction, along with other characteristics, such as the mechanical quality factor, [Q.sub.m], and acoustic impedance
, [Z.sub.a], have been found from measurements on the electrical impedance of the piezoelectric composites.
It can be incorporated into a surface mounted AE sensor (5), where the electroactive composite is adhered to a backing material of the same acoustic impedance
and electrical contacts are made to both faces, or be embedded into a fiber reinforced epoxy laminate structure (6).
For the case of identical materials (of the acoustic impedance
Z) on both sides of the gap and the gap distance, d, being much less than V/2[pi]f (V is the wave speed), or d << V/2[pi]f, we have an approximate expression for T from Krautkramer  as