TY - JOUR
T1 - Depth evaluation of shallow surface cracks in metals using rectangular waveguides at millimeter-wave frequencies
AU - McClanahan, Andrew
AU - Kharkovsky, Sergey N.
AU - Maxon, Andrew R.
AU - Zoughi, Reza
AU - Palmer, David D.
PY - 2010
Y1 - 2010
N2 - This paper presents a resonant technique, which is founded on previous extensive work on millimeter-wave surface crack detection and sizing, for the accurate depth evaluation of long and shallow surface damages (scratches or cracks), which are represented as rectangular slots, in metal plates. A crack in a metal plate may be considered a short-circuited rectangular waveguide, which presents certain resonant characteristics when its electrical depth coincides with a quarter of the operating wavelength. Furthermore, a shallow crack may be filled with a dielectric material to electromagnetically make it appear deeper and hence facilitate its depth evaluation. The resonant properties of a crack depend on the dielectric properties of the material filling the crack and the crack dimensions. It is shown that a slight amount of loss, which is associated with the dielectric material, causes a relatively significant and characteristic change in the reflection coefficient measured using a probing rectangular waveguide aperture. In particular, this change affects the magnitude of the reflection coefficient, which is an easier parameter to measure than the phase. This information, as a function of frequency, may then be used to determine the shallow crack depth. This paper presents the foundation of this technique at millimeter-wave frequencies, along with supporting electromagnetic simulations and experimental results.
AB - This paper presents a resonant technique, which is founded on previous extensive work on millimeter-wave surface crack detection and sizing, for the accurate depth evaluation of long and shallow surface damages (scratches or cracks), which are represented as rectangular slots, in metal plates. A crack in a metal plate may be considered a short-circuited rectangular waveguide, which presents certain resonant characteristics when its electrical depth coincides with a quarter of the operating wavelength. Furthermore, a shallow crack may be filled with a dielectric material to electromagnetically make it appear deeper and hence facilitate its depth evaluation. The resonant properties of a crack depend on the dielectric properties of the material filling the crack and the crack dimensions. It is shown that a slight amount of loss, which is associated with the dielectric material, causes a relatively significant and characteristic change in the reflection coefficient measured using a probing rectangular waveguide aperture. In particular, this change affects the magnitude of the reflection coefficient, which is an easier parameter to measure than the phase. This information, as a function of frequency, may then be used to determine the shallow crack depth. This paper presents the foundation of this technique at millimeter-wave frequencies, along with supporting electromagnetic simulations and experimental results.
KW - aluminium
KW - crack detection
KW - cracks
KW - filled cracks
KW - millimetre wave imaging
KW - rectangular waveguides
KW - resonance
UR - http://handle.uws.edu.au:8081/1959.7/511629
M3 - Article
SN - 1557-9662
SN - 0018-9456
JO - IEEE Transactions on Instrumentation and Measurement
JF - IEEE Transactions on Instrumentation and Measurement
ER -