Monitoring of Initiation and Propagation of Fatigue Cracks in Steel Plate Deck by FSM

Abstract

Fatigue test for the steel plate deck was carried out by using the wheel load traveling test machine. The position where fatigue crack initiation was specified by FSM (Field Signature Method) could be confirmed by visual inspection (9-11)×10⁴ cycles later. The time of initiation of small crack (less than 150mm), which cannot be confirmed by visual inspection, could be specified by FCs value that is the deviation of FC value. The direction of propagation and the length of fatigue crack could be specified.
Being conscious of the site, it was investigated whether initiation and propagation of fatigue crack can be detected with high accuracy and extensively or not by impressing pulse current in the wide range (1200×1600 (in mm)) and by extending the distance (80, 160 and 240 (in mm)) between pairs. Although FC value became small as the distance extended, FC values increased with the similar tendency. So, specification of fatigue cracks was not difficult.