Issue 38

G. S. Serovaev et alii, Frattura ed Integrità Strutturale, 38 (2016) 392-398; DOI: 10.3221/IGF-ESIS.38.48 398 The sharpness of the frequency spectrum picture will significantly depend on relative location of impact and the measurement and type of impact load. C ONCLUSIONS he comparison of the three considered models of delamination with respect to their applicability to the solution of the problem of analysis of changes of natural frequencies of a composite plate shows that in spite of the indisputable simplicity of the free mode model, the results show an excessive drop in eigenfrequencies. The constrained and the contact models yield qualitative agreement in shifts of natural frequencies with a change of the defect size. The calculation of the constrained model is much easier and faster. However, the algorithm of calculation of the model with the contact repeats the steps performed during the experiment and more fully reflects special features typical for real structures. The results suggest that for detection of defects at an early stage of their development it is necessary to record the change in the spectrum in the high frequency range (in this case greater than 4 kHz). A numerical model of the studied structure allows to analyse frequency response to the occurrence of the defect and to determine the most sensitive of them to a specific type of defect. A CKNOWLEDGMENTS he study was performed in Perm National Research Polytechnic University with the support of the Russian Science Foundation (project №15-19-00243) R EFERENCES [1] Zhang, Z., Shankar, K., Ray, T., Morozov, E.V., Tahtali, M., Vibration-based inverse algorithms for detection of delamination in composites, Composite Structures, 102 (2013) 226-236. [2] Stepinski, T., Uhl, T., Staszewski, W., Advanced Structural Damage Detection: From Theory to Engineering Applications, John Wiley & Sons, (2013). [3] Adams, D.E., Health Monitoring of Structural Materials and Components, John Wiley & Sons, (2007). [4] Morassi, A., Vestroni, F., Dynamic methods for damage detection in structures. Springer Wien New York, (2008). [5] Zou, Y., Tong, L., Steven, G.P., Vibration-based model-dependent damage (delamination) identification and health monitoring for composite structures – a review. Journal of Sound and Vibration, 230(2) (2000) 357-378. [6] Wang, J.T.S., Liu, Y.Y., Gibby, J.B., Vibrations of split beams. Journal of Sound and Vibration, 84 (1982) 491-502. [7] Mujumdar, P.M., Suryanarayan, S., Flexural vibrations of beams with delaminations, Journal of Sound and Vibration, 125(3) (1988) 441-461. [8] Lee, J., Free vibration analysis of delaminated composite beams. Computers and Structures, 74 (2000) 121-129. [9] Shen, M.H., J.E. Grady. Free vibrations of delaminated beams. AIAA Journal. 30(5) (1992) 1361-1370. [10] Valdes Diaz, S.H., Soutis, C., Delamination detection in composite laminates from variations of their modal characteristics. Journal of Sound and vibration, 228(1) (1999) 1-9. [11] Chuang, K.-C., Liou, H.-C., Ma, C.-C., Investigation of Polyvinylidene Fluoride(PVDF) Films in Identifying High- Frequency Vibration Modes of Flexible Plates. IEEE Transactions on Ultrasonic, Ferroelectrics, and Frequency Control, 61(6) (2014) 1047-1058. [12] Yan, W., Wang, J., Chen, W.Q., Delamination assessment of a laminated composite beam using distributed piezoelectric sensor/actuator, Smart. Mater. Struct., 20 (2011) 1-14. [13] Rout., M., Baishya, N., Effects of delamination on the vibration characteristics of composite beams, Noize and Vibration Worldwide, 24-29 (2010). [14] Muc, A., Stawiarski, A., Identification of damages in composite multilayered cylindrical panels with delaminations. Composite Structures. 94 (2012) 1871-1879. [15] Dey, S., Karmakar, A., Free vibration analyses of multiple delaminated angle-ply composite conical shells – A finite element approach, Composite Structures. 94 (2012) 2188-2196. T T