TY - EJOU
AU - Swenson, E.D.
AU - Soni, S.R.
TI - Damage Detection in a Geometrically Constrained Area1
T2 - Structural Longevity
PY - 2009
VL - 1
IS - 2
SN - 1944-6128
AB - A "hot-spot" structural health monitoring (SHM) approach that uses
lead zirconate titanate (PZT) sensor pairs to generate and sense Lamb waves is
evaluated on a test article that accurately represents the complex geometry of a relatively inaccessible bulkhead section of an existing aircraft. This work is motivated
by the fact that fatigue cracks have been known to propagate in this particular bulkhead in several aircraft. In order to simulate damage, electrical discharge machine
(EDM) cuts are made to simulate real cracks in a test article. Because the damage occurs in a region of restricted geometry, PZT sensors must be placed in close
proximity to each other, but on opposing sides of the expected crack. The close
proximity of the piezoelectric sensors and restricted geometry create challenges in
determining which portion of the collected response should be analyzed. The first
approach evaluated is a tuning approach where specific excitation frequencies are
chosen based on the relative S0 and A0 Lamb wave mode amplitudes. Theoretical
time of arrival window lengths for the S0 and A0 Lamb wave modes are reduced in
size to minimize the contribution of reflected wave energy. The second approach
involves evaluating responses over a wide range of excitation frequencies in combination with only evaluating the responses in the dominant mode’s theoretical time
of arrival window. A simple damage metric is applied to demonstrate that the presence of cracks can be detected as well as the length can be roughly approximated.
This approach is further validated with laser vibrometery scans of the test article in
both healthy and damaged states.
KW - Damage detection
KW - structural health monitoring
KW - SHM
KW - PZT
KW - Lamb wave
KW - laser vibrometry
DO - 10.3970/sl.2009.001.095