Effective plastic strain is a monotonically increasing scalar value which is calculated incrementally as a function of (Dp)ij, the plastic component of the rate of deformation tensor. In tensorial notation, this is expressed as…
epspl=integral over time of (depspl)=integral[sqrt(2/3(Dp)ij*(Dp)ij)]*dt
Effective plastic strain grows whenever the material is actively yielding, i.e., whenever the state of stress is on the yield surface.
In contrast, the tensorial strain values, written by LS-DYNA when
STRFLG is set to 1 in
*DATABASE_EXTENT_BINARY, are not necessarily monotonically increasing as they reflect the current, total (
elastic+plastic) state of deformation. To fringe the tensorial strains in LS-PrePost, click
Fcomp > Strain.
Effective strain, expressed in tensorial notation, is
sqrt(2/3(eps)ij*(eps)ij); (See p. 461 of LS-DYNA Theory Manual 2006). This is NOT the same thing as effective plastic strain.
Other measures of strain can be fringed in LS-PrePost but these are calculated by LS-PrePost from nodal displacements, e.g.,
FCOMP > Infin ; (infinitesimal or engineering strain)
FCOMP > Green
FCOMP > Almansi
Effective stress, also known as von Mises stress, is defined as follows: