Fracture Monitoring In Stainless Steel By Analyzing Acoustic Emissions And Infrared Thermography Signals

The purpose of this work is to make available, in a non-destructive way, data concerning the structural integrity of materials subjected to fatigue loads. The crack propagation was studied in AISI 430F/1 by using Acoustic Emission (AE) and Infrared Thermography (IT) at the same time. The main advantage connected with the use of both these approaches refers to the possibility to monitor the whole history of the specimen without scanning requiring and accessing from just one side of the specimen. For AE technique two sensors were placed on the surface of the specimen in order to detect the elastic waves emitted by mate-rial under stress and due to the activation of inner defects. By analyzing the overall acoustic signals, it is possible to associate a part of them specifically to the crack propagation phe-nomenon. At the same time a thermocamera was placed in front of the specimen to live monitor the variation of surface temperature. Above all, the rise of temperature around the crack tip was observed in order to evaluate the advancing of the crack during the test. As a final point, a comparison between the two techniques was carried out aiming to assess the capability of each approach in following the evolution of the fracture process.