Fd. Fischer et al., TRANSFORMATION-INDUCED PLASTICITY REVISED AN UPDATED FORMULATION, International journal of solids and structures, 35(18), 1998, pp. 2209-2227
An externally stressed specimen in the process of a phase transformati
on may show a significant nonlinear behavior which is known as transfo
rmation-induced plasticity (TRIP). The TRIP-strain can be irreversible
as in the case of steels, or reversible with a certain hysteresis as
in the case of shape memory alloys. The basic mechanisms contributing
to this nonlinear phenomena are the accommodation process of the trans
formation strain and the orientation process of the transforming micro
regions. TRIP strain formulations carried out so far do not meet both
effects. A thermodynamical concept is presented in this paper to find
a TRIP strain rate which takes into account the coupling of phase tran
sformation and microplasticity. The start and progress of the transfor
mation condition, during which the plastic behavior governs the transf
ormation/plastic processes, are derived by solving a conditional extre
mum problem, composed of the dissipation inequality and the constraint
conditions: the transformation condition and the yield condition. The
thermomechanical and calorimetric constitutive equations are derived
in rate form when the transformation and the plastic processes are ful
ly coupled. Some illustrative examples are discussed by assuming a con
crete form of the Gibbs free energy and the transformation/yield condi
tions. The cross-coupling effect of the transformation and plasticity
is well understood in the TRIP strain rate and the transformation kine
tics. (C) 1998 Elsevier Science Ltd. All rights reserved.