Uniaxial Ratcheting Behavior of Dual-Phase Steel Sheet

Uniaxial ratcheting behavior of an automotive-grade dual-phase steel sheet of 1.6 mm thickness has been investigated through engineering stress-controlled asymmetric cyclic loading experiments in the elastoplastic regime at ambient temperature (~ 28°C). Experiments have been performed keeping mean stress, stress amplitude or maximum stress constant. The effect of stress combinations on ratcheting deformation has been rationalized in terms of plastic strain amplitudes, both in loading and in unloading directions. It is found that for all stress combinations the steady-state ratcheting rate follows a perfect power relationship. Scanning electron fractography reveals that failure under asymmetric cyclic loading conditions occurs in a ductile manner through the formation of voids as it happens under tensile loading.