Dynamics of Delayed Fracture in a PC Steel Wire by an Analysis of Guided Waves
Takeshi AIHARA and Mikio TAKEMOTO
Abstract:This paper presents new methods for source location and fracture dynamics study of guided waves produced by the delayed fracture of a pre-stressed concrete (PC) steel wire. Utilizing the guided wave produced by laser ultrasonic system, the author first proposed a new source location method of guided waves in the PC wire of 7mm diameter. Source location in the transverse section was determined from the amplitude ratio of the maximum peak of flexural (F-) mode to that of first arrival longitudinal (L-) mode. Location in the axial direction was determined from the time difference between the first arrival L-mode and the peak arrival time of the F-mode. Estimated progression of micro-cracks agreed well with characteristic features observed on fracture surface. Dynamics of micro-cracks were estimated by the waveform matching of the first packet of the L-mode to the monitored one and found to be generated within 0.5 microseconds. Key Words:Delayed fracture, Guided wave, Acoustic emission, Source location, Source dynamics