Biomedical Engineering Reference
In-Depth Information
to strain rate and the duration of the applied loads (Carter and Hayes, 1976)
(Fig. 4.2). Elastic modulus and strength have a power law correlation with
strain rate with a coefficient of 0.06 approximately. The
in vivo
strain rate
for bone can vary from of 0.001 to 0.01 per second in the course of daily
activities. Thus, in this range of strain rate, the Young's modulus increases
by approximately 15% whereas it is about 20% stronger (Fig. 4.3).
400
Strain rate increase
300
200
0.01/sec
100
0
0.0
0.5
1.0
1.5
2.0
Strain (%)
4.2
Strain rate dependence of cortical bone material behavior. Both
modulus and strength increase for increased strain rates (adapted
from McElhaney, 1966).
300
70
Strength
Modulus
250
60
200
50
150
40
100
30
50
20
0
10
0.0001
0.01
1.0
100
Strain rate (strain s
-1
)
4.3
Dependence of modulus and ultimate tensile strength of human
cortical bone for longitudinal loading as a function of strain rate
(adapted from Wright and Hayes, 1976).
