Quantitative testing of tightly closed, small backwall cracks in steel objects has been investigated under load-free conditions. Both the fully open and tightly closed fatigue cracks in two different structural materials of interest are considered. The investigation has been carried out using a new ultrasonic angle beam technique, which has the capability of sensitively dealing with very small, tight cracks. Using the technique, both the crack size and the extent of crack closure of an unknown crack can be determined simultaneously from the measured response by solving an inverse problem. Based on the experimental observation, an evaluation algorithm has been developed for the characterization of an unknown crack (open/closed) in both stainless and carbon steel structures, where a theoretical model of crack closure is used. Results of the present investigation are compared and discussed in light of those obtained using the standard ultrasonic techniques of testing.
|出版ステータス||Published - 2006 8 1|
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