VISUALIZATION OF KINETICS OF PLASTIC DEFORMATIONS IN STEEL PRODUCTS BY INFRARED RADIATION

The purpose of this article is to identify the possibility of infrared computer thermography for diagnosing the development of plastic deformations of steel products. Methods of conducted experimental studies were published. The results of experiments are presented and analyzed. The possibility of application of infrared computer thermography for research of regularities of origin, propagation and localization of plastic deformation in steel elements during their deformation at room temperatures and after preliminary cooling is substantiated. It is shown that for smooth specimens with distance from the machine grip, the temperature of near-surface layers differs to a greater extent from the corresponding temperature for the mid-surface layers. The excess of the deformation temperature of the surface layers over the mid-surface layers depends on the stage of deformation of the sample material. At the end of the elastic stage of the specimen, the temperatures differ by 1.7 °C, and at the beginning of fracture with the formation of the neck, the excess of surface layer temperatures reached 4.5 °C. In specimens with lateral notches with a distance from the machine grip, the surface temperature did not change during loading. In the sections passing through the zone of scale delamination near the notches, the surface temperature in the middle part of the specimen is higher by 3.0–3.5 °C than in the vicinity. The maximum temperature of the metal surface during deformation reached 70 °C. It was found that the sections of the specimen adjacent to the notch in the process of deformation lose position stability, manifested in the change of the initial position to the deformed one. At the same time, the metal adjacent to the notch in the form of a prism with a triangular base and a height equal to the sheet thickness lost stability under the action of normal and tangential stresses. The metal in the prism volume was practically not deformed. The prism base temperature increased slightly only after the initiation of the notch crack.