Specific Features of the Behavior of the Coercive Force in Low-Carbon Plastically Deformed Steels

The relationship between the coercive force in low-carbon steels under plastic extension and compression and the values of deformation and actual and residual stresses are studied. This relationship is investigated for both “ slow” loading (when an equilibrium deformation is attained for each load value) and “fast” loading (when such equilibrium is not attained). It is shown that (i) a comparatively small increase in the coercive force in a loaded condition is due only to an increase in the density of dislocations in the process of plastic extension; (ii) a significant steep increase in the coercive force accompanying removal of the load from a plastically stretched specimen is fully due to residual compression stresses; (iii) the values of the coercive force under “slow” and “fast” loading are significantly different in the region of small deformations less than 2.5%; (iv) these values are close to each other in the loaded state for all deformations up to 10%; (v) a relief of the compression stress that creates plastic deformations causes a steep decrease in the coercive force that is as large as its increase following relief of plastic extension; this is explained by the emergence of a significant residual tension stress. The obtained results are of importance for the use of the method based on measuring the coercive force to test steel structures under the conditions when plastic deformations develop.__________Translated from Defektoskopiya, Vol. 41, No. 5, 2005, pp. 24–38.Original Russian Text Copyright © 2005 by Kuleev, Tsar’kova, Nichipuruk.