Biomedical Engineering Reference
In-Depth Information
table 24.2
distribution of tissue von mises Stress, and the amounts of tissue elements yielded in
Compression and tension at the apparent yield Point in each loading Condition
lontitudinal direction
transverse direction
Compression
tension
Compression
tension
Distribution of
tissue von
Mises stresses
(MPa)
(mean±SD)
Trabecular
specimen A
55.41±38.10
40.02±26.68
24.04±23.52
20.76±19.06
Trabecular
specimen B
44.74±33.95
35.29±25.20
23.74±20.58
19.47±17.53
Amount of
tissue
elements
yielded in
compression
(%)
Trabecular
specimen A
7.4730
0.1928
1.0072
0.0640
Trabecular
specimen B
4.1022
0.1581
0.9128
0.0941
Amount of
tissue
elements
yielded in
tension (%)
Trabecular
specimen A
2.7220
10.6903
0.6426
2.3876
Trabecular
specimen B
2.3514
2.9208
0.8224
2.0527
to evaluate the structure model type, which relates to the convexity of the structure to a model
type (Hilderbrand and Rüegsegger, 1997). Our previous study found that vertebral trabecular
bone with different three-dimensional microstructural properties based on their SMI values
had different fracture risks (Gong et al., 2006). Trabecular specimen 1 in this study belonged
to a low-SMI group, and specimen 2 belonged to a high-SMI group. They underwent different
yield behaviors, which can be quantified by apparent yield stress and apparent yield strain at
the apparent level, and von Mises stress distribution, the amount of tissue elements yielded in
compression as well as in tension at the tissue level. The vertebral body is a weight-bearing bone.
The internal trabecular bone represented more superior mechanical properties in the longitu-
dinal direction in comparison with the transverse direction, that is, a higher apparent Young's
modulus, yield stress, and tissue von Mises stresses, and more elements yielded in compression
and tension at the apparent yield point when compressed in the longitudinal direction, showing
more elements performing at the maximum load-bearing capacity. More trabecular specimens
need to be investigated for a more detailed relationship between trabecular bone yield behaviors
and their microstructures.
In the current study, the hard tissue was highly homogeneous, which can be seen in Figure 24.1.
Hence, all the bone tissue material was assumed to have the same bilinear, tissue-level, constitutive
behavior. The role of bone material heterogeneity on the apparent and tissue-level yield behaviors
cannot be derived accordingly. Trabecular specimens from other locations with hard tissue hetero-
geneity need to be further investigated.
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