7th ECCOMAS Thematic Conference on Smart Structures and Materials SMART 2015 A.L. Araúo, C.A. Mota Soares, et al. (Editors) c  IDMEC 2015 STATISTICAL ANALYSIS FOR PIEZO-BASED STRUCTURAL DAMAGE DETECTION USING ENHANCED NONLINEAR CRACK-WAVE INTERACTIONS Kajetan Dziedziech ∗ , Konrad ˙ Zolna † , Lukasz Pieczonka ∗ , Wieslaw J. Staszewski ∗ , Piotr Kijanka ∗ ⋆ Department of Robotics and Mechatronics, AGH University of Science and Technology ul. Mickiewicza 30, 30-059 Kraków, Poland dziedzie@agh.edu.pl, lukasz.pieczonka@agh.edu.pl, w.j.staszewski@agh.edu.pl, pkijanka@agh.edu.pl † Institute of Mathematics, Jagiellonian University ul. Prof. Stanislawa Lojasiewicza 6, 30-348 Kraków, Poland konrad.zolna@gmail.com Keywords: Structural Health Monitoring, Non-Destructive Evaluation, Fatigue Crack detec- tion, Ultrasonic Waves, modulated Lamb waves, Non-linear Vibro-Acoustic Modulations. Summary: The paper presents statistical analysis of damage index used to detect structural damage in the recently developed enhanced nonlinear crack-wave interaction technique. Con- sidered damage detection technique combines Lamb waves propagation with nonlinear acous- tics. Low-frequency excitation is used to modulate propagating Lamb waves in the presence of fatigue cracks. Analysis of these modulations is used to detect the presence of damage. This method is extremely sensitive to any nonlinearity source present in an inspected object. It is, however, also sensitive to measurement noise. Therefore, currently it is necessary to perform high number of measurements in order to minimize the influence of noise on the results. A possi- ble solution to that problem is the use of statistical resampling techniques. This paper presents a method of measurement data resampling in order to artificially increment the population size and improve the quality of estimates. 1. INTRODUCTION Various damage detection methods based on ultrasonic wave propagation have been devel- oped for the last few decades [1, 2]. Within this group of methods there are the techniques based on nonlinear vibration and acoustic phenomena that gain an increasing attention in the scientific community [2, 3, 4]. This is mainly due to the fact that the nonlinear damage detection methods are usually much more sensitive to detect small damage severities than their linear counterparts [5]. The nonlinear vibro-acoustic modulation technique [8, 9, 10, 11, 12] is one of the most widely used approaches. The method allows for crack detection in metals [12, 13, 14] and