自己相関ロックイン赤外線サーモグラフィ法による鋼床版デッキ貫通型疲労き裂の検出

概要

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A new remote nondestructive inspection technique, based on thermoelastic temperature measurement by infrared thermography, is developed for detection and evaluation of fatigue cracks propagating from welded joints in steel bridges. Fatigue cracks are detected from localized high thermoelastic temperature change at crack tips due to stress singularity under variable loading from traffics on the bridge. Self-reference lock-in data processing technique is developed for the improvement of signal/noise ratio in the crack detection process. The technique makes it possible to perform correlation processing without an external reference signal. In this paper, self-reference lock-in thermography is applied for crack identification based on the detection of the singular stress field in the vicinity of crack tips. Experiments are conducted using steel deck specimen, which simulates an actual steel bridge using steel deck in crack propagation test. It is found that significant stress concentration zone can be observed near the crack front, which enabled us to detect through deck type fatigue cracks.
2010-06-25