The present paper evaluates two phenomenological plasticity models which account for the influence of strain-path change (SPC) on the stress-strain behavior. The HAH model (Barlat et al., 2014) is modified to capture SPC transients observed in aluminum, i.e., hardening stagnation after reverse SPCs and permanent softening after orthogonal SPCs. Predictions by the HAH model are compared to the MHH model (Mánik et al., 2015), which was originally developed for aluminum. The MHH model turned out to be directly applicable to an extra deep drawing quality (EDDQ) steel without any modifications. The MHH model predicts the stress-strain behavior after single SPCs slightly better than the HAH model for both aluminum and steel. It can also capture correctly R-value transients in aluminum after purely orthogonal SPCs. However, only the HAH model can capture transients after double SPCs qualitatively for low carbon steels. The applicability of these advanced continuum plasticity models to aluminum and steel and the differences in their mathematical formulation are discussed.

In this work, a new model is proposed for predicting stress transients caused by strain path changes. The model is formulated in stress space, where a second order tensor, i.e., the microstructure stress deviator, is used to memorize and model the evolution history of the microstructure. Both its direction and magnitude are used to transiently distort the yield surface and to modify the work hardening. Orthogonal strain-path changes are handled by yield surface distortions, while Bauschinger effects are described by a kinematic hardening formulation. The model is calibrated to, and captures well, earlier published experiments for commercial pure aluminum, an extra deep drawing quality steel and a dual-phase steel. The proposed model describes qualitatively the response to double strain-path changes in low carbon steels. Efforts are made to design a relatively simple model as compared to the high complexity of the experiments, applying simple mathematical sub-models with straightforward interpretations and enabling a numerically stable implementation.

The stress-strain behavior of the aluminum alloy AA3103 subjected to single and double strainpath changes (SPCs) is studied experimentally. The experimental program includes compression-tension, tension-tension, rolling-tension and tension-rolling-tension tests. The considered AA3103 plate exhibits plastic anisotropy, a strong Bauschinger effect with hardening stagnation after strain reversal, cross-hardening and permanent softening after orthogonal SPCs in the tension-tension tests. However, when instead the orthogonal SPCs are obtained by rolling-tension tests, cross-softening is observed. The same behavior is seen in more complex tension-rolling-tension tests. Three state-of-the-art advanced plasticity models are used in an attempt to model the experimentally observed behavior. These models all account for plastic anisotropy and transient effects after SPCs, using a microstructure deviator tensor to describe a fading memory of the deformation history. While the models successfully describe the behavior after strain reversals, they fail to represent the behavior after orthogonal SPCs. It is concluded that the Schmitt angle, on which the current models depend, is not sufficient for a fundamental description of SPCs for the considered AA3103 alloy.

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