*Article* **Using AE Signals to Investigate the Fracture Process in an Al–Ti Laminate**

### **Grzegorz Swit ´ 1,\*, Aleksandra Krampikowska 1, Tadeusz Pała 2, Sebastian Lipiec 2 and Ihor Dzioba 2**


Received: 7 June 2020; Accepted: 26 June 2020; Published: 29 June 2020

**Abstract:** The paper describes tests conducted to identify the mechanisms occurring during the fracture of single-edge notches loaded in three-point bending (SENB) specimens made from an Al–Ti laminate. The experimental tests were complemented with microstructural analyses of the specimens' fracture surfaces and an in-depth analysis of acoustic emission (AE) signals. The paper presents the application of the AE method to identify fracture processes in the layered Al–Ti composite using a non-hierarchical method for clustering AE signals (k-means) and analyses using waveform time domain, waveform time domain (autocorrelation), fast Fourier transform (FFT Real) and waveform continuous wavelet based on the Morlet wavelet. These analyses made it possible to identify different fracture mechanisms in Al–Ti composites which is very significant to the assessment of the safety of structures made of this material.

**Keywords:** Al–Ti laminate; fracture; acoustic emission diagnostic; pattern recognition; clustering AE signal
