Measuring Microscale In-Plane Indentation Displacement Field for Material Characterization

A method measuring microscale in-plane indentation displacement field
$\text{u}_{i}$
on the indented specimen surface is proposed by utilizing an optical flow (OF) algorithm. With images taken before and after indentation test, the calculated displacement field containing noise (
$\text{u}_{o}$
) is computed using the OF algorithm. Due to the microvibration and the repositioning error after indentation test, the originally calculated
$\text{u}_{o}$
contains the displacement error
$\text{u}_{e}$
. Thus,
$\text{u}_{e}$
is corrected using the origin-symmetric condition of indentation displacement field formed by the axisymmetric indenter. The effect of the grain size and the surface roughness of specimen on the
$\text{u}_{i}$
field are also investigated. The corrected
$\text{u}_{i}$
fields from the indentation tests for various materials (steel, copper, and aluminum) are verified by comparing to the indentation finite element analysis (FEA). After correcting the error
$\text{u}_{e}$
, the average correlation coefficient
$R^{2}$
between the displacement curve
$\text{u}_{i}$
from the OF and the indentation FEA is 99% for all materials. Finally, it is concluded that the proposed method can measure the accurate in-plane indentation displacement field
$\text{u}_{i}$
on a microscale.