  Most of crystalline materials exhibit a hysteresis on their deformation curve
when mechanically loaded in alternating directions. This Bauschinger effect is
the signature of mechanisms existing at the atomic scale and controlling the
materials damage and ultimately their failure. Here, three-dimensional
simulations of dislocation dynamics and statistical analyses of the
microstructure evolution reveal two original elementary mechanisms. An
asymmetry in the dislocation network junctions arising from the stress driven
curvatures and the partial reversibility of plastic avalanches give an
explanation to the traction-compression asymmetry observed in FCC
single-crystals. These mechanisms are then connected in a physically justified
way to larger-scale representations using a dislocation density based theory.
Parameter-free predictions of the Bauschinger effect and strain hardening
during cyclic deformation in different materials and over a range of loading
directions and different plastic strain amplitudes are found to be in excellent
agreement with experiments. This work brings invaluable mechanistic insights
for the interpretation of experiments and for the design of structural
components to consolidate their service life under cyclic load.
