A three-dimensional digital image correlation technique for strain
measurements in microstructures
Journal of Biomechanics, 37 (9):
1313--1320 (September 2004)DOI: 10.1016/j.jbiomech.2003.12.036
Zusammenfassung
A three-dimensional digital image correlation technique is presented
for strain measurements in open-cell structures such as trabecular
bone. The technique uses high-resolution computed tomography images
for displacement measurements in the solid structure. In order to
determine the local strain-state within single trabeculae, a tetrahedronization
method is used to fill the solid structure with tetrahedrae. Displacements
are calculated at the nodes of the tetrahedrae. The displacement
data is subsequently converted to a deformation tensor in each of
the tetrahedral element centers with a least-squares estimation method.
Because the trabeculae are represented by a mesh, it is possible
to deform this mesh according to the deformation tensor and, at the
same time, visualize the calculated local strain in the deformed
mesh with a finite element post-processing tool. In this way, the
deformation of a single trabecula from an aluminum foam sample was
determined and validated with rendered images of the three-dimensional
sample. A precision analysis showed that a rigid translation or rotation
does not affect the accuracy. Typical values for the standard deviation
in the displacement and strain components are 2.0μm and 0.01, respectively.
Presently, the precision limits the technique to strain measurements
beyond the yield strain.