Exploring the capability of acoustic emission technique in early detecting mode I and mixed mode fractures

Acoustic Emission non-destructive technique was used coupled with Digital Image Correlation to explore its early warning capability in detecting Mode I and mixed Mode fractures in Scots pine samples. The acoustic behaviour of the specimens, being different for tree rings number (high and low) and grain angle (0-20-40-60 degrees), was investigated while undergoing an external tensile load by a Universal Testing Machine. A risk amplitude threshold (51.9 dB) was experimentally computed a posteriori as an early warning indicator for Scots pine samples with mixed Mode fractures. In the case of Mode I fracture, as cracks occur instantaneously, the oncoming fracture could not be predicted.