Volume 31, Issue 4 (July 2003)
The Determination of JIc Using the Time-Frequency Analysis Method
Elastic-plastic fracture toughness, JIc, can be used as an effective design criterion. Among the JIc test methods approved by ASTM, the unloading compliance method has been used in this paper. In order to examine the relationship between the fracture behavior of the JIc test and acoustic emission (AE) signals, the post processing of AE signals was carried out by a joint time-frequency analysis method, i.e., the fast Fourier transform. The objective of this study is to evaluate the application of the characterization of AE signals for the unloading compliance method of the JIc test. Using a time-frequency analysis, AE signals can be extracted from the raw signal and be analyzed at the same time. The AE signal generated in the elastic-plastic fracture of material shows different aspects in the elastic and the plastic range or at the first portion of the crack growth by fracture. For example, energy obtained from the AE count method increases rapidly at the beginning of the plastic fracture. The elastic-plastic fracture of the material can be analyzed using real time AE characteristics.