Biomedical Engineering Reference
In-Depth Information
9.3 Microindentation Testing of Dry Cortical Bone Tissues
In Section 9.2, approaches for removing the soft tissue from bone samples
were described. Microindentation testing of these cleaned bone samples as
presented in Yin et al. [3] is discussed in this section. Typically, assessments
of the crack propagation and deformation behavior of dry cortical bone on
a microscopic scale by means of microindentation are described. It is well
known that microindentation offers a means of characterizing the defor-
mation properties of bone [24] and provides a basis for evaluating a range
of contact-related properties, particularly surface-damage phenomena in
sharp-particle compression [25].
9.3.1 Preparation of Bone Samples
To conduct the microindentation testing described in this section, Yin
et al. [3] purchased three lamb femurs from 6-month-old lambs from a local
supermarket and stored these femurs in a refrigerator at -20°C. The femurs
were macerated in a solution containing 40 g Biozet laundry powder (KAO,
Australia) and 2 L water for 5 days at room temperature in a fume cupboard.
(The composition of Biozet was described in Section 9.2.1.) The pH value of
the solution was 10.5. After 5 days, soft tissues were manually removed from
the femurs using a rod, a cooking knife, and a brush.
Yin et al. then cut transverse section samples of 10 mm thickness from the
central femurs using a diamond saw machine at a low rotary speed. Alcohol
was utilized as coolant during the cutting process. The samples were washed
to remove any residual abrasive from the cutting. They were then polished
using metallographic polishing techniques. The initial polishing was per-
formed on a series of silicon carbide papers of grit sizes 240, 320, 400, 600,
800, and 1,200. Fine polishing was performed using diamond suspension
slurries with grades 6, 3, 1, and 0.25 μm on polishing cloth. The samples were
cleaned before proceeding to the next finer level of polishing. After the final
polishing, the samples were stored in a fume cupboard at room temperature
for 2 weeks.
9.3.2 Standard Microhardness Indentation Testing
The polished dry bone surfaces were indented with a Vickers diamond
indenter in a microhardness tester (MHT-1, Matsuzawa Seiki, Japan) [3].
Five indentation loads of 0.245, 0.49, 1.96, 4.9, and 9.8 N were applied for 10 s.
Six indentations were made at each load on each transverse section. This
resulted in a total of 30 indentations in each sample. A distance of at least
twice the impression diagonal was kept between indentations to prevent
interactions between neighboring indentations. The lengths of the inden-
tation diagonals were measured using optical microscopy. Three samples
