PSI - Issue 52

Vitalijs Pavelko et al. / Procedia Structural Integrity 52 (2024) 382–390 Vitalijs Pavelko/ Structural Integrity Procedia 00 (2019) 000 – 000

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MPa. At this external load the mean stress in middle cross-section of PET is equal to 117.25 MPa. In the fatigue test with maximal stress in cycle 150 MPa and cycle coefficient 0.333 destruction of PET was observed after 140 kcycles. A similar result was obtained at static loading of composite plate equipped by several PETs whose longest side coincides with direction of tension of the host plate Meisner et al. (2015). The destruction of PET was indicated by a kink of the electrical charge curve at strain 3200 μm/m of host plate. So, all this shows that the static and fatigue strength of PET constrained state much more than at pure tension. Before all, it caused by difference of strass state. At pure tension there is homogenies stress state of PET, and its destruction is defined by the principle of “weak est link of chain”: destruction occurs in a cross -section with smallest strength. In the constrained state of PET its stress state is non-homogenies, and its destruction is defined by two factors: local stress and local strength. Destruction occurs in a cross-section in which at an increase of external load the stress achieves to the level of the local strength. The interesting effect of multiple destruction of brittle PET was established and was called as the process of equi fragmental crushing (EFC). The smatter of EFC is as follows. If PET installed to surface of uniformly deformed structural element, then at monotonic loading there are several levels of load on which of them each fragment of PET divides into two parts of approximately the same length. To each stable configuration of damaged transducer there are correspond: critical load and even number of fragments of approximately the same length. Similarly, there is a procedure of jump-type change of the electrical potential of PET at transition from one stable state to another. This effect was experimentally observed for electrical charge by Gall et al. (2009) and Meisner et al. (2015) for circular and rectangular PETs respectively. This is very simple means to indicate a crack occurrence in PET. Acknowledgement This study was funded by European Regional Development Fund (ERDF), Measure 1.1.1.5 “Support to international cooperation projects in research and innovation of RTU”. Project No. 1.1.1.5/18/I/008. Author is very grateful for this help and support Bin Lin, Giurgiutiu, V., Pollock, P., Buli Xu and James Doane, J., 2010. Durability and Survivability of Piezoelectric Wafer Active Sensors on Metallic Structure. AIAA Journal 201048:3, pp. 635 – 643. Buethe I., Moix - Bonet M., Wierach P., Fritzen C. - P., Check of Piezoelectric Transducers using the Electromechanical Impedance, 7th European Workshop on Structural Health Monitoring, Nantes, 2014, pp.748 - 755. Gall, M., Thielicke, B., Schmidt, I., 2009. Integrity of piezoceramic patch transducers under cyclic loading at different temperatures, Smart Materials and Structures 18. Hu Sun, Yishou Wang, Xinlin Qing , and Zhanjun Wu., 2018. High Strain Survivability of Piezoceramics by Optimal Bonding Adhesive Design. Sensors (Basel). Meisner, C., Stolz, C., F. Hofmann, F., 2015. Durability assessment of PZT -transducers for guided wave based SHM systems using tensile static and fatigue tests . Publication: 7th International Symposium on NDT in Aerospace, 16. - 18. Nov 2015, Bremen, Germany, paper Tu.2.A.1. Mizuno,M., Enomoto,Y., Okayasu, M., 2010. Fatigue life of piezoelectric ceramics and evaluation of internal damage. Procedia engineering 2, pp. 291-297 Pavelko, I., Pavelko,V., Ozolinsh, E., Pfeiffer,H., Wevers, M., 2010 (1). Pre-stressed ultrasonic sensor for structural health monitoring. International Conference "Research and Education in Aircraft Design 2010", Poland, Varšava . Pavelko, I., 2010. Research on the Protection of Piezoceramics Transducers from the Destruction by Mechanical Loading. Int.Virtual J. for Science, Technics and Innovations for the Industry, Issue 7, pp.17-21. Pavelko, I., Pavelko, V., Kuznetsov, O., Ozolinsh, E., Ozolinsh, I., Pfeiffer, I., Wevers, M.. 2010(2). Problems of structural health monitoring of aircraft component. The proceeding of 27th Congress of the International Council of the Aeronautical Sciences, Nice, France, paper ICAS 2010 10.6.1. Sun, C.T., 2000. Fracture and fatigue of piezoceramics under mechanical and electrical loads. Durability 2000 Proceedings of the Durability Workshop, Berkeley, California, pp. 231-244 Tanimoto, T., Yamamoto, K., and Morii, 1994. T. Nonlinear Stress-Strain Behaviour of Piezoelectric Ceramics under Tensile Loading. Proceedings of the 9th IEEE International Symposium on Applications of Ferroelectrics. IEEE, pp. 394-397 Wandowski, T., Moll, J.,Malinowski, P., Opoka, S., Ostachowicz, W., 2015. Assessment of piezoelectric sensor ad hesive bonding. Journal of Physics: Conference Series 628, 012114. References