Discontinuities of microstructure in steels induce stress concentrations. Microplasticity is
the plasticity which exists locally at these stress concentrations, whereas the remainder
of the material is in the elastic domain. The microplasticity threshold is the nominal
stress in uniaxial loading from which microplasticity exists. During fatigue tests,
this threshold has been determined for the 304 L stainless steel by measurements of
temperature variations, informations derived from hysteresis loops, observations of
microstructure at the surface of polished specimens. The microplasticity threshold
of the studied material is between 60 and 75 MPa.