2614 高マンガン鋼レールに適した超音波探傷技術の基礎的検討(S22-3 非破壊評価とモニタリング(3),S22 非破壊評価とモニタリング)

概要

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A high manganese steel rail is currently used at crossing points for local line and the Shinkansen (bullet train) in Japan. These rails contain manganese of no less than 11 to 14%; however, common steel rails contain only about 1%. One of the advantages of using high manganese steel rails is that they have high damage tolerance to fatigue cracks and so a longer life span. By the way, usual rails are regularly inspected by ultrasonic testing (UT). But the UT isn't applied to high maganese steel rails. Because many ultrasonic scatterings occur in high manganese steel rails due tot heir larger crystal grains and casting defects. It is difficult to distinguish flaw echoes from scattered waves. This study aims to develop an ultrasonic testing method and systems which is applicable to high manganese steel rails. In this paper, we applied pulse compression techniques by frequency modulation. Frequency band of an input signal is optimized for inspecting the rail. Flaw echo can be distinguished by this optimization. SN ratio have been improved from -3.3dB (usual method) to 13.9dB (proposed method).
一般社団法人日本機械学会の論文
2007-09-07