Active Thermography for Residual Stresses Identification in Gears

Residual stresses are a topic of great interest in mechanical field since they can impact in a positive or negative manner on both materials and components. During the years, many efforts were done to identify and to characterize residual stresses and, in many cases, for this purpose destructive techniques are required. An innovative Non-Destructive Techniques (NDT) such as Active Thermography (AT), called also stimulated thermography, is widely used in industrial environment to investigate defects inside the material. Recent studies describe the potentiality of Active Thermography also for other mechanical fields like the material characterization or the damage investigation. In this work, an alternative application of Active Thermography is proposed to identify residual stresses generated from surface treatments. In particular, thermal responses were investigated for both samples and gears subjected to case hardening and shoot peening processes. Moreover, a careful analysis on both mechanical and physical properties were performed for both samples and gears aiming to verify the Active Thermography results.