PSI - Issue 2_A

Lenka Michalcová et al. / Procedia Structural Integrity 2 (2016) 3049–3056 Author name / Structural Integrity Procedia 00 (2016) 000–000

3056

8

4. Discussion The overall analyses indicate the following conclusions:

 The simultaneous measurement of UGW and AE is inappropriate due to the necessity of filtering a large amount of data.  Numerical models would be useful for the appropriate sensor placement and specification of elastic wave propagation. Without relevant information about the wave propagation, it is not possible to determine even the distance between sensors across the stringers for the purposes of the source localization. For the crack monitoring, the data clearly indicate whether the crack propagates in the stringer or in the skin.  The influence of the stringers on the AE signals is significant because the crack starts to propagate in the stringers. The beginning of the crack propagation in the stringers was determined by both parameters – the AE event duration ratio and by ∆t changes in trend as well. Regarding the duration ratio, the sensor placement was found to be important. If the sensors are mounted within the same skin (in between the stringers), the duration ratio increases during the crack propagation within the skin and decreases when the crack starts to propagate in the stringer. If the sensors are mounted on opposite sides of the stringer, an obvious increase in the AE event duration ratios occurs when the crack starts to propagate in that stringer. The occurrence of a crack in the stringers was indicated by the ∆t parameter as well, namely by the change of the ∆t level of the sensors behind the stringers. 5. Conclusions The purpose of this paper was to evaluate the suitability of the acoustic emission method for the structure health monitoring regarding the crack growth during the fatigue test of an integrally stiffened panel made from an aluminium alloy. It is evident that the study has been successful. Based on 2 physically different parameters, ∆t and event duration ratio, it was possible to determine when the crack started to propagate in the stringers. This conclusion is valid for pairs of sensors placed above each other and across the stringers as well. These configurations can be considered as complementary to each other. The next stage of our research will be focused on the experimental confirmation of these results during the forthcoming full-scale wing test of a commuter aircraft. References FAA, Advisory_Circular 43.13-1B [online], [cited 4-22- 2016], available from: http://www.faa.gov/documentLibrary/media/Advisory_Circular/Chapter_05.pdf Masaryk University, Faculty of Education, Acoustic emission [online], [cited 5-22- 2015], available from: http://www.ped.muni.cz/wphy/projekty/kemis.html Gardiner G., 2015. Structural health monitoring: NDT-integrated aerostructures enter service [online], [cited 5-22- 2015], In: Composites World, available from: http://www.compositesworld.com/articles/structural-health-monitoring-ndt-integrated-aerostructures-enter-service Khan Alahi Uddin, Non-destructive Testing Applications in Commercial Aircraft Maintenance [online], [cited 5-22- 2015], available from: http://www.ndt.net/article/ecndt98/aero/031/031.htm Li Li, Lomov Stepan V., YAN Xiong a Carvelli Valter, 2016, Cluster analysis of acoustic emission signals for 2D and 3D woven glass/epoxy composites. Composite Structures. 2014, 116, 286-299. available from: http://linkinghub.elsevier.com/retrieve/pii/S0263822314002335 Lu Chao, Ding Peng,Chen Zhenhua, 2011, Time-frequency Analysis of Acoustic Emission Signals Generated by Tension Damage in CFRP. Procedia Engineering. 23, 210-215. available from: http://linkinghub.elsevier.com/retrieve/pii/S1877705811053343 Michalcová, L., Kadlec, M., 2016, Carbon/epoxy composite delamination analysis by acoustic emission method under various environmental conditions. Engineering Failure Analysis. Thompson Donald O., Chimenti Dale E., 1993, editors of the Proceeding: Review of Progress in Quantitative Nondestructive Evaluation (Book 12), New York: Plenum Press. ISBN 03-064-4483-6. T. U. Delft, Structural Ingeneering Lectures, Chapter 5. Aircraft & Spacecraft Structures, 2010, [online], [cited 6-22- 2016], available from: https://ocw.tudelft.nl/course-readings/5-aircraft-spacecraft-structures/