Detection of Crack Initiation and Propagation in Aluminum Alloy Under Tensile Loading, Comparing Signals Acquired by Acoustic Emission and Vibration Sensors

Abstract

The application of aluminum alloys in various industries such as automotive and aerospace, is inclusive. In addition, in these industries, holes in these materials are used for bolts and rivets. Accordingly, in this article, the initiation and the propagation of cracks in the 2024 aluminum alloy were detected, by means of two methods including acoustic emission and vibration analysis approaches. For this objective, acoustic and vibration sensors were connected to the open-hole aluminum specimen under tensile loading and signals were acquired. Obtained results indicated that the energy of signals, which was recorded by sensors, was comparable to the stress–strain diagram and therefore, the efficiency of two methods in detecting the crack initiation was proved. The calculated maximum stress at the specimen edge by the vibration analysis was closer to experimental data, in comparison to the acoustic emission approach. Then, the fracture frequency of the aluminum alloy was calculated using two mentioned methods and by the fast Fourier transform. By the use of the cumulative energy, which was calculated from recorded signals, the crack propagation was also detected by both approaches and a better efficiency for predicting the fracture by the acoustic emission method was shown. At the end, images of the scanning electron microscopy from the crack and the fracture surface were also demonstrated.