1999 Volume 48 Issue 11 Pages 733-738
With the aim of studying the kinetics and mechanism of environmental assisted cracking such as stress corrosion cracking and delayed fracture in small diameter rod specimens, we developed a new signal processing method of the guided waves monitored by resonant-type AE sensors mounted on the outer surface of the rod. Source location of AE events can be identified by utilizing the ratio A/S of the maximum amplitude A of zero-th order anti-symmetric mode to the peak amplitude S of the first zero-th order symmetric mode waves. Here, the guided waves must be measured by four AE sensors mounted on the surface in 90° step at the same distance from the source. Fracture kinetics, limited to only the Mode-I fracture, were estimated by the So-packet waveform simulation by utilizing the overall transfer function determined as a response to a small compression-mode PZT element excited by a pulse. This simulation method, though needs some special techniques and depends on the frequency of the element, enables us to estimate the fracture kinetics with source rise time less than 1μs. The proposed method was adopted to tetrathionic SCC of sensitized SUS304 stainless steel rod, and revealed that fast cleavage-type fractures with rise time of 0.4μs to 2.5μs occurred during the SCC progression.
