Plakhtiy R. Development of a method for diagnostics of brittle fracture in materials using parameters of acoustic emission signals.

Fields of acoustic waves generated during initiation and propagation of cracks in solids under quasistatic loading conditions. Development of both a method and the instrumentation for diagnostics of brittle fracture in solids under quasistatic loading according to the changes of the most stable parameters of the acoustic emission (AE) signals. Linear fracture mechanics approaches, spectral analysis of AE signals, mathematic modeling, mechanical testing, circuit modeling and breadboarding, statistical analysis of the experimental data. Physical model has been developed and phenomenological criterion has been introduced for classification of fracture types. This criterion incorporates such parameters as AE signal rise time, the changes in the amplitude-vs.-frequency characteristics and the basic parameters of measuring channel of the AE instrument. The criterion has been used for detection of brittle fracture during AE diagnostics of the parts of working structures. Novel quantitative data on the attenuation coefficients for the elastic AE wave propagation in different structural materials have been obtained and a new effective method for AE diagnostics and monitoring of structural health has been proposed. A new concept of an analog highway for the AE instrumentation, a multichannel portable AE measuring system, and a method for AE diagnostics of products and structural elements have been developed. The results of this work have been used for AE diagnostics of the following objects: bridges, reinforced concrete parts of civil structures, oil storage tank; and for the evaluation of mechanical properties and crack propagation resistance of materials. Area of application - construction and facility maintenance in oil and natural gas transportation industry.