Analysis of the hysteresis loop in stainless steels I. Austenitic and ferritic steels

In constant amplitude cyclic straining the hysteresis loops of an austeniti c and a ferritic steer were recorded and their shape was analysed. The gene ralised statistical theory of the hysteresis loop based on the Masing hypot hesis that considers the effective stress and the distribution of the criti cal internal stresses of the elementary volumes was employed. The second de rivative of the hysteresis half-loop yields information on the effective st ress and the probability density function of the critical internal stresses and its evolution in cyclic straining and in dependence on the strain ampl itude. The changes of the effective modulus are also reported. The total cy clic stress can be separated into the effective and internal stress compone nts. The high effective stress in ferritic steel-is connected with the diff icult motion of screw dislocations in the b.c.c. structure. The evolution o f the probability density function of the austenitic and ferritic steels du ring cyclic straining is discussed in terms of changes of the internal disl ocation arrangement. (C) 2001 Elsevier Science B.V. All rights reserved.