Changes in the three-dimensional (3D) shapes of roughened surfaces and the
inhomogeneous deformation behaviors of individual grains during uniaxial te
nsion of polycrystalline iron are experimentally investigated. The principa
l strains of each grain are evaluated by obtaining the approximated ellipse
of the strain distribution of the grain, and then the relationship between
the change in surface roughening and grain deformation is discussed. It is
found that the mountains and the valleys of the roughened surface elongate
in the axial direction with increasing amplitude during uniaxial tension.
The grains continue to deform with the applied strain, though the rate of i
ncrease of the maximum principal strain differs among grains. From the comp
arison between the roughening phenomenon and the deformation of grains, it
is found that surface roughening is closely related to the mutual rotation
of grains. Thus, roughness increases due to the different deformation behav
iors of individual grains.