Monitoring the onset of crack extension using acoustic emissions during fracture toughness testing of WAAM 2.5%Cr-1%Mo steel

This study investigated the performance of Acoustic Emission (AE) techniques for detecting the onset of crack propagation during fracture toughness testing of Wire Arc Additive Manufactured (WAAM) 2.5%Cr–1%Mo steel. Compact tension (C(T)) specimens were machined in both the X–Z and Y–Z orientations from a WAAM-fabricated wall and tested at room temperature. AE signals were continuously monitored throughout standardized fracture toughness tests, and the resulting data were analyzed alongside detailed examinations of the fracture surfaces and conventional fracture toughness measurements. AE-based estimates of the fracture toughness at the onset of crack extension were compared with those obtained using the standard procedure for determining J IC . The AE results did not consistently align with the standard measurements and, in some cases, provided a more conservative estimate of the fracture toughness associated with the onset of crack extension. The findings also highlighted the influence of microstructural variations and manufacturing-induced discontinuities in the WAAM steel on both the fracture behavior and the AE response. This study advances the use of AE for real-time monitoring of crack initiation and damage evolution in WAAM steel, offering valuable insights into its potential for structural integrity assessment of WAAM components. At the same time, the results underscore the challenges and limitations of using AE to accurately determine fracture toughness at the onset of crack extension.