In a previous research investigation, using the Mróz model and the endochronic
theory of plasticity as their bases, two sets of elastic-plastic constitutive
relations were identified that account for the interaction in stress fields between
adjacent particles in particulate metal matrix composites (PMMCs). In this
paper the ability of the two models to predict the behavior of PMMCs under
variable amplitude nonproportional cyclic loading paths is evaluated by
comparing the models predictions with experimental results obtained from a
series of biaxial (tension-torsion) cyclic tests performed on tubular specimens
made from 6061-T6 aluminum with 10 and 20% volume fractions of alumina
particles. For most of the investigated loading paths, both models predict
satisfactorily the amplitudes of the experimental strains. However, the endochronic
theory-based constitutive model generally gives better predictions of the measured
strains.
