Biomedical Engineering Reference
In-Depth Information
table 15.3
dynamic maximum and minimum Facet Contact Forces for different Cases and
Static Facet Contact Force under a 400-n Static Compressive load
Contact Forces
Contact
Forces
Contact
Forces
Case*
Case
Case
Items
values
(n)
Items
values
(n)
Items
values
(n)
D
max
D
min
S
400
11.8
3.39
8.41
D
max
D
min
S
400
15.6
2.57
8.41
D
max
D
min
S
400
9.73
6.35
8.41
Case 1
Case 2
Case 3
D
max
D
min
S
400
11.2
4.93
8.41
D
max
D
min
S
400
10.7
6.43
8.41
D
max
D
min
S
400
31.6
12.8
18.3
Case 4
Case 5
Case 6
D
max
D
min
S
400
31.7
14.8
18.3
D
max
D
min
S
400
31.5
14.7
18.3
Case 7
Case 8
Note:
D
max
and D
min
are the maximum and minimum values of facet contact forces during the first vibration period.
The static facet contact force S
400
is the predicted facet contact force under 400-N static compressive loads.
*
Instruction of different cases in this study
.
Case 1:
Intact/5Hz/no damp/40N
Case 2:
Intact/10Hz/no damp/40N
Case 3:
Intact/5Hz/no damp/20N
Case 4:
Intact/5Hz/damp0.08/40N
Case 5:
Intact/5Hz/damp0.15/40N
Case 6:
Denucleated/5Hz/no damp/40N
Case 7:
Denucleated/5Hz/damp0.08/40N
Case 8:
Denucleated/5Hz/damp0.15/40N
the load coefficient of the dynamic load against the preload. In this study, the dynamic load force
F
dynamic
is 40 N, and the preload force
F
preload
is 400 N.
After the transient dynamic analyses, the values of facet contact forces in the sagittal plane were
recorded. The plots of predicted results as a function of time revealed a cyclic response with some
fluctuations and distortions, as shown in Figures 15.9 and 15.10. For the sake of comparison, the
mechanical responses of the static axial loads of 400 N were also computed. Table 15.3 exhibits the
dynamic maximum and minimum of the facet contact forces of different cases in the first vibration
period.
For example, the dynamic maximum and minimum facet contact forces are 11.8 and 3.39 N for
the intact model without damping under a 5-Hz cyclic axial load of 40 N and upper body preload
of 40 kg (case 1), and the corresponding static facet contact force is 8.41 N under a 400-N static
compressive force. The higher frequency cyclic compressive loads will increase the facet contact
force. The results in Table 15.3 and Figure 15.9a show that the dynamic maximum and minimum
facet contact forces are 15.6 and 2.57 N, respectively, using a 10-Hz cyclic load of 40 N for the intact
model without damping (case 2). In addition, when comparing different magnitudes of external load
(Figure 15.9b), although the external load doubled (from 20 N—case 3—to 40 N), the amplitude
of the contact force increased by 1.49 (Table 15.4). This implies that the facet force contact force
exhibits nonlinear behavior under different magnitudes of external vibration loads.
The dynamic maximum and minimum facet contact forces of the denucleated model (case
6) were 31.6 and 12.8 N (see Table 15.3 and Figure 15.9a). The static facet force of the denucle-
ated model (case 6) under a 400-N compressive load was 18.3 N. Compared with the intact
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