Mordyuk B. The pecularities of plastic deformation and structure changing of aluminium, copper and armko-iron under shock ultrasonic and shock low-frequency treatments

The dissertation work is devoted to theoretical and experimental investigations of plastic deformation process of aluminium, copper and armko-iron under effect of multiple shock treatments - ultrasonic and low-frequency ones and also to study of peculiarities of dislocation structure formation into near surface and balk layers above mentioned metals. The phenomenological model of metal deformation process under shock treatments was devoted. It was firstly shown that plastic strain accumulation under multiple shock loads is conditioned by relaxation processes that occurs during gap between consequent impacts and depends on frequency, amplitude and also on activation parameters of dislocation motion and temperature. It was shown that internal stress conditioned by dislocation play a determinative role in deformation process. Based on statistic analysis of chaotic distribution of internal stress and taking into account of local overstrain occurrence the refinement of residual strain dependencies on treatm ent time was carried out. Based on suggested treatment of experimental dependencies in coordinates true strain - square root of time and results of transmission electron microscopy investigations it was shown that the dislocation structure evolution of cooper can be described by scheme: wood - cell structure - return structure. The conducted work permits to explain a nature of essential reduction of yield stress under shock ultrasonic treatment of metals that have a scientific and practical importance.