Stankevych O. Acoustic emission diagnostics of fracture types of structural materials

Dynamic displacement fields generated by surface displacement during crack advancement for different types of cracks in elastic half space are the object of the research. The objective of this research is to develop a methodology for quantitative evaluation and identification of fracture types for structural materials using АE-signal wavelet transform. There were used the mathematical modeling, a boundary integral equation method, spectral analysis and wavelet transform of AE-signals, numerical methods of calculation, statistical analysis, physical experiment. The mathematical models are built for displacement fields initiated by surface displacement of internal penny-shaped crack of modes I, II and III in elastic isotropic half space. There were revealed the changes in spectral characteristics of elastic oscillations in half space for the different sizes of defects. Also, the specific features of displacement fields at a half space surface for different crack types were studied. For fracture types identification a new criterion was proposed, which uses wavelet transform parameters obtained from AE-signals. The results of this work were used during AE-diagnostics of the oil-pumping equipment at the following stations, subsidiaries to oil-trunk pipelines Druzhba: "Chyhzivka", "Zhulyn", "Dolyna". The results of this research could be used for: improvement of the existent methods of technical AE-diagnostics, optimization of a criterion for fracture type identification, generalization of certain statements for AE-signal selection, development of novel instrumentation for in-service AE-monitoring.