Vdovychenko O. Characterization of mesostructure and properties of powder and composite materials by acoustic spectroscopy

This thesis focuses on the solution of an important scientific and technical problem of the development of new methodology for acoustic identification of structural features and properties of powder, composite and damaged materials based on analysis of resonance response to mechanical excitation for the development of the parts with specified physical, mechanic and functional characteristics. The influence of features of mesostructures of such materials on their macroscopic behavior is the subject of inquiry. As a basic, two different types of the structural features – pores and partly consolidated boundaries between particles or phases are considered. The methodology formulated and substantiated in the work allows to discern the contribution of the stated types of the features and to estimate their fractions that serve as a criterion for the refinement of technological processes of fabrication of studied classes of materials. The methodology is based on experimentally revealed dependence on state of the boundaries between particles in one hand, and non-symmetric response of the materials to the load of different directions in other hand. The response of materials is identified by the acoustical resonant technique elaborated in this work. A conception of non-linear elastic behavior of powder and damaged materials was used and extended. Based on the utilization of the developed methodology, the influence of the different types of mesostructural elements on elastic characteristics and damping capacities of powder metals (Fe, Ti, Al-6Cu-0,4Mn), ceramics (α-Al2O3) and composite materials (HAp/glass phase, aluminum alloys/SiC) was analyzed and the optimal structural and technological parameters of their fabrication were determined. The stated approaches were assumed as a basis for the development of techniques for reveal of structural changes in steels (Steel 20 and 12Kh1MF) during operations of parts under extreme conditions with the purpose of the substantiated overhaul-period renewals, and also for the technique of investigation of mechanisms of deformation of martensitic alloy Ti3Sn with high damping capacity. Keywords: powder and composite materials, ceramics, structure, pore, phase boundary, damage accumulation, non-linear elasticity, damping capacity, acoustic resonant techniques, non-destructive evaluation.