Effects of strain rate and notch on acoustic emission during the tensile deformation of a discontinuous yielding material

The acoustic emission (AE) generated during tensile tests performed on Q345 steel specimens was investigated in this study. Two typical types of AE signals were obtained during the test: Type A signals with burst type waveforms in the micro-yielding and work-hardening stages and Type B signals with continuous-type waveforms during the discontinuous yielding (Luders band propagation) stage. The effects of the strain rate and notch on these two types of signals were studied. The AE energy of Type B signals increased with increasing strain rate and was much higher in notched specimens compared to unnotched ones at high strain rates. However, for Type A signals, less AE energy was generated in notched specimens than in unnotched specimens, and it showed little sensitivity to changes in the strain rate. These results were fully analyzed by relating the AE behavior to the deformation properties and transmission electron microscope (TEM) observations of the materials. Thus, the AE source mechanisms and the effects of the strain rate and notch during plastic deformation were determined for discontinuous yielding materials.