Acoustic Emission Entropy as a Measure of Damage in Materials.

In this paper, we propose the information entropy of acoustic emission (AE) signatures as an index for assessment of degradation in materials. This is a new method for health monitoring of materials and structures that relies on the estimation of the information entropy from the AE signals detected, for example from cyclic fatigue loading of the materials. Different ways of calculation of the information entropy from AE signals are explored and discussed in this paper. As an example of the materials degradation, this study investigates the behavior of maximum entropy (S_max) at the time of the materials' failure using a series of fatigue cracking tests on titanium alloy, a material commonly used in certain aircraft structures. This paper describes the fatigue tests in which AE waves and features were measured and discusses the various approaches to estimate the information entropy corresponding to the detected AE. The results show that fatigue failure occurs at the same maximum entropy value regardless of the trajectory of the fatigue crack growth and loading conditions that caused the fatigue. [ABSTRACT FROM AUTHOR]