*Advances in Fatigue and Fracture Testing and Modelling*

to fatigue that it can be used as evidence to identify the causes of fatigue failure [1]. With the advance of industry and the increase in the number of machines such as cars, airplanes, compressors, pumps, turbines, etc. that are under repeated load and vibration, fatigue has become more common. The main reason that fatigue failure is dangerous is that it occurs suddenly and invisibly [1]. The beginning of the failure of the part due to fatigue is the initiation of microscopic cracks and then their growth. Crack growth continues until the cross-section of the metal is so small that the stress on it is greater than the ultimate strength of the metal so brittle failure occurs in the specimen. For this reason, failure will be sudden. The fatigue failure surface consists of a smooth area due to friction with the growth of cracks in the section and a rough area that is softly broken in the part when the load is intolerance by the section [2]. **Figure 1** shows fatigue failure of the Bonanza F33 propeller, which is made of aluminum alloy 2025.

**Figure 1.** *Fatigue failure of bonanza F33 propeller.*

### **Figure 2.**

*Example of sources of acoustic emission. (a) Cracking. (b) Deformation and transformation. (c) Slip. (d) Leakage.*

*Determining the Characteristics of Acoustic Emission in the Fatigue Crack Growth of Aluminum… DOI: http://dx.doi.org/10.5772/intechopen.99360*
