STUDY ACOUSTIC EMISSION SIGNALS AT TENSION STEEL 20

An investigation was made of acoustic emission signals during uniaxial tensile testing of flat specimens of steel 20 used for parts of welded structures with a large volume of welding, as well as pipelines, collectors and other parts operating at temperatures from –40 to 450 °C under pressure. Tensile testing with simultaneous registration of acoustic emission was carried out on a universal testing machine manufactured by Tinius OIlsen Ltd, model H100KU, at a movement speed of the active gripper of 0.05 meters per minute. Registration of AE signals was carried out using wideband GT350 sensors from GlobalTest and an analog-to-digital converter NationalInstruments 6363X with subsequent storage of the registration results in the form of a time series in the computer memory. A comparative analysis of the amplitude distribution of the AE signal for the area of the yield area and the area of destruction was carried out according to the value of information entropy, fractal dimension, and self-organization parameter. It was found that the parameter of self-organization of the amplitude distribution of the signal is the most informative in describing the processes associated with acoustic emission. As additional information, it is advisable to use data on the structure of the self-organization parameter. The results obtained indicate the possibility of using the statistical model of the Dirichlet distribution as a model of processes associated with the appearance of acoustic emission signals from sources of incipient and developing defects during routine tests of products made of structural carbon high-quality steels with a pearlite-ferrite structure. The paper presents a version of the model and modeling algorithms for FE-modeling corrosion cracking processes in structural elements loaded by pressure and exposed to aggressive corrosion media. To assess the effectiveness of the present models and algorithms, the failure process of a thin-walled tubular specimen partly submerged into a chlorine-containing liquid and loaded by axial tension is numerically modeled.