Fatigue Cracking and Acoustic Emission Regularities in Metals: Crack Origination and Growth

Abstract:

Specimens of Al-and Ti-alloys and turbine blades of Ni-based alloy were considered in the case of crack origination at the surface, subsurface, and at the inner surface of turbine blades. Aircraft structures such as hydrocylinders of Al-based alloy and landing gear of high-strength-steel were also considered. There was used acoustic emission (AE) monitoring to fix moment of crack occurring and, then, analyzing its growth. Fracture surface features appearance was compared with AE-signals regularities based on fractographic analyses. To indicate the crack origination moment it was introduced α-criterion. This criterion characterized drastically increase in summarized AE-signals appearing in dependence on cyclic loads number. During crack propagation, there was used Elber-portion of opened crack to register AE-signals in cyclic loads. It was demonstrated crack increment in unloading portion of cyclic loads with fatigue striations formation. Two aircraft structures of hydrocylinders and shock strut of landing gear were tested on the special test facilities and AE-monitoring was conducted. Effectiveness of α-criterion using for crack registration in the high-cycle fatigue regime was demonstrated applicably to crack appearance on the internal surface and subsurface. The discovered dependences of summarized AE-signals on number of cycles were compared with fracture surface patterns and briefly discussed.

• Periodical: Key Engineering Materials (Volumes 592-593)
• Pages: 735-740
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.592-593.735
• Online since: November 2013
• Authors: Andrey Shanyavskiy*, Mukharbiy Banov
• Keywords: Acoustic Emission (AE), Crack Growth, Crack Origination, Fractography, Fracture Surface, Internal, Mechanism, Monitoring, Subsurface

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