Effects of Material Variation on Acoustic Emissions-Based, Large-Crack Growth Model

Acoustic emissions (AE) collected during fatigue crack-growth in a titanium alloy were analyzed and compared with a previously proposed AE-based, crack-growth model used for an aluminum alloy. Acoustic emission technology has the potential for on-line structural health monitoring; a desired procedure for evaluating material degradation in military and commercial aircraft. Both aluminum and titanium alloys are prevalent materials in aerospace structures which prompted this current investigation. Acoustic emissions are stress waves that propagate through a material as a result of applied stresses. When a material is subjected to cyclic fatigue loading, AE signals are generated due to dislocation movements and microstructural changes. These waves can be detected by piezoelectric sensors when placed on the surface of the material. Previous research proposed a linear relationship between the logarithm of AE count rate (dc/dN) and the logarithm of crack growth rate (da/dN) for the aluminum alloy, Al7075-T6, at various loading conditions and loading frequencies. This paper summarizes and compares the results obtained from identical experiments using titanium alloy Ti-6Al-4V with the previous study. The results suggest the linear model used to relate AE and crack growth in Al7075-T6 holds true for the titanium alloy while, as expected, the model parameters are material dependent. With each material, the model parameters and their distributions were estimated using a Bayesian regression technique.


 1. Rabiei, M. (2011). A Bayesian framework for structural health management using Acoustic Emission

monitoring and periodic inspections. PhD dissertation, University of Maryland, College Park, MD.

2. Bassim, M. N., S. St. Lawrence, and C. D. Liu. (1994). Detection of the onset of fatigue crack growth in rail

steels using Acoustic Emission, 41(2), 207–214.

3. Beattie, A. G. (1983). Acoustic emission, principles and instrumentation. Journal of Acoustic Emission, 2, 95–


4. Berkovits, A., and D. Fang. (1995). Study of fatigue crack characteristics by acoustic emission. Engineering

Fracture Mechanics, 51(3), 401–416.

5. Wang, Z. F., J. Li, W. Ke, and Z. Zhu. (1992). Acoustic emission monitoring of fatigue crack closure. Scripta

Metallurgica et Materialia, 27(12), 1691–1694.

6. Mix, P.E., 2005. Introduction to nondestructive testing: a training guide, Wiley-Interscience.

7. Iyyer, N., S. Sarkar, R. Merrill, and N. Phan. (2007). Aircraft life management using crack initiation and crack

growth models – P-3C Aircraft experience. International Journal of Fatigue, 29(9-11), 1584–1607.

8. Krupp, U. (2007) Crack Propagation: Microstructural Aspects, in Fatigue Crack Propagation in Metals and

Alloys: Microstructural Aspects and Modelling Concepts, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim,


9. Biancolini, M., C. Brutti, G. Paparo, and A. Zanini. (2006). Fatigue cracks nucleation on steel, acoustic

emission and fractal analysis. International Journal of Fatigue, 28(12), 1820–1825.

10. Keshtgar, A. (2013). Acoustic emission-based structural health management and prognostics subject to small

fatigue cracks. PhD dissertation, University of Maryland, College Park, MD.

11. Keshtgar, A., Modarres, M. (2013). Acoustic emission-based fatigue crack growth prediction. Proceedings of

the 2013 Reliability and Maintainability Symposium (RAMS), 1-5.

12. ASTM E647-08, 2008. Standard Test Method for Measurement of Fatigue Crack Growth Rates, ASTM


13. Gauthier, Michelle M. (1995) Engineered materials handbook – desk edition, ASM International, Materials

Park, OH.

14. AEwin Software User’s Manual. (2007). Physical Acoustic Corporation, Princeton Junction, NJ.

Usage Shares
Total Views
5 Page Views
Total Shares
0 Tweets
0 PDF Downloads
0 Facebook Shares
Total Usage