ESTIMATION OF MECHANICAL DEFORMABILITY OF METALS BASED ON ENERGY DISSIPATION

Steels of various strength classes were distributed and analyzed  according to deformation resistance parameter. It is considered that  the deformation process in the thermodynamic aspect appears to be a  dissipative effect: a part of kinetic energy of the external mechanical  action transfers to the internal energy of the deformable metal with the  formation of a certain dislocation structure. Because of it the energy  criteria were proposed for the deformability of metal, determined in  the standard tensile test. The basis of these criteria is the deformation  work, which was determined by the area of the tension diagram. In this  case, the absorbed energy determines the unit rupture work, and the  rate of energy absorption determines the metal deformation resistance (compliance of plastic deformation). Quantitative assessment of dissipation effect demonstration with matching of the unit rupture work values and the compliance criteria was evaluated. The study was carried  out using standard tensile tests of samples, made of steels with various  strengths, achieved due to chemical composition (alloying) and heat  treatment, used to manufacture products of various structural purposes.  Herewith in the selected complex of steels, the yield strength range  was 210  –  1660  MPa, the ultimate strength was 840  – 1940  MPa. Consequently, it was established that unit rupture work of the concentrated  deformation much exceeds the unit rupture work of the uniform deformation. The criteria of the concentrated deformation compliance  are much lower than the criteria of uniform deformation compliance,  moreover, there is a noticeable correlation between it. The correlation  can be considered as a demonstration of the structural evolution of  metal in both stages of its deformation, in which, in the process of  self-organization of dissipative system, such as deformable metal, the  dislocation density serves as an internal parameter controlling the evolutionary transformation. The correlation between the compliance criteria and the ultimate stresses under uniform deformation and fracture  was established. Thereby, the ranking of steels with different strengths  per energy, absorbed during deformation, was conducted. In the applied aspect, the numerical values of the unit rupture work and the compliance criterion can be used for predicting the behavior of steels of  various strength classes under mechanical treatment and mechanical  action during operation.

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