Romanyshyn R. Development of the Ultrasonic Method of Metal Damage Diagnosing Based on the Recorded Back-scattered Signal

The thesis goal is to solve the important scientific and technical issue of the development of ultrasonic tomographical diagnostic technologies for pre-defect state of construction materials evaluation. These technologies are based on statistical processing of back-scattered ultrasonic signals ("structural noise") and tomographical reconstruction of the damage state of material. The object of the research is the dependence of the parameters of ultrasonic signal on the parameters of the material damage state. The limitation of the existing methods and devices as to the retrieval of information about spatial distribution of material scattered damage before macro-flows are formed is found. The expediency of using the back-scattered signal (as it is the most sensitive as for scattered damage dynamics) is proved. The acoustic receiving channel of A-Scans registration was analyzed, the model of the recorded signal was suggested and the processing technologies were developed in order to consider the acoustic contact factor, amplification, device noise, signal attenuation while propagation. The method of ultrasonic back-scattering profile definition along the direction of ultrasound propagation is developed. The method is based on A-Scan signals registration and statistical processing. The back-scattering profile is the base of tomographical reconstruction of material scattered damage. A new approach to tomographical reconstruction of the curved projections and for objects with curved boundaries is developed in order to optimize tomographical reconstruction procedures, to perform statistical processing of the recorded signals and to obtain back-scattering profile of the material experimentally. This information is the base of new ultrasonic techniques as to complex structured materials diagnostics before the flaws are formed but there are already places with scattered damage. The new ultrasonic technology for the evaluation of the damage state of steel and alloys of the feed-water pipelines is developed and tested experimentally in "Rovno NPP". The technology is based on the disorder level of the tomographical pictures calculation. The disorder of the tomographical pictures usually is increased with the material damage state increase. The new ultrasonic technique of weld joint quality evaluation is developed in order to perform diagnostics of material in cases where standard techniques (e. g. B-Scan) are not informative because of the flaws are not formed. The developed technique can be used for the evaluation of the weld joints uniformity along the joint and symmetry across the joint and for welding process adjustment. The technique is automated and can be used for the weld joints monitoring in order to detect the high scattered damage and further flaw appearance allocations. The new ultrasonic technique of scattered damage of metal while different types of loading is developed. The technique is based on multiple recording and compatible processing of back scattered signal. The compatible processing is based on the obtaining of back-scattered signal deviations histograms on comparable products and their comparison in order to evaluate the scattered damage of each product and resolution of the approach. The technique of adhesive strength of the gas-thermal coating mapping is suggested. It is based on the identification of delaminated places in the product using backscattered signal approach. The new ultrasonic technique of the evaluation of the state of hydrogen attacked material is developed. It allows the hydrogen damage unhomogeneity in the product evaluation. The developed techniques are implemented in the ultrasound computerized tomograph UST5M and are tested experimentally in the laboratory and in industrial conditions in "Rovno NPP" while the implementation of the projects under the program "Resource".