Identification of strain-softening constitutive relation from uniaxial tests by series coupling model for localization

Recent studies of path stability in inelastic bifurcation problems have shown that, even if the specimen is stable, strain softening in uniaxial tests must localize right after the peak stress state into the smallest length permitted by the material, which is approximately equal to the characteristic length of nonlocal continuum. Without knowing this length, the uniaxial stress-strain relation cannot be identified from uniaxial test data. The post-peak stress-strain relation is analyzed on the basis of a series coupling hypotheses. Van Mier's uniaxial compression test results for specimens of different lengths show this hypothesis to be valid.