Biomedical Engineering Reference
In-Depth Information
a
b
100
100
100
100
50
50
50
50
0
0
0
0
-50
-50
-50
-50
-100
-100
-100
-100
1
1
10
10
5
7.5
100
0
100
0
1000
-5
1000
-7.5
-10
10000
10000
-15
D=5 µm
D=10 µm
c
d
100
100
100
100
50
50
50
50
0
0
0
0
-50
-50
-50
-50
-100
-100
-100
1
-100
1
10
10
20
10
100
0
100
1000
0
1000
-20
-10
10000
-40
10000
-20
D=20 µm
D=30 µm
Fig. 7.4
Friction logs of cortical cross section-TA2 pairs (normal load: 90 N; displacement
amplitude: 5-30
μ
m )
amplitude as a function of the number of cycles can be recorded as a friction log, as
shown in Fig.
7.4
. The frictional force increased linearly with the imposed ampli-
tude by the main accommodation of elastic deformation. However, under a given
normal load, classic friction logs transformed from partial slip to gross slip as the
imposed amplitude increased. Microscope examinations showed that the wear depth
of bone generally increased with the friction coeffi cient. The worn scar area on bone
was a little bit larger than that on the ball surface. The wear depth on the Ti ball was
only several microns, which was much less than that on bone. The friction coeffi -
cient of the bone-TC4 pair was higher than that of bone-TA2 pairs. The maximum
wear depth on bone against TA2 was about 40 % of the value of that on bone against
TC4. Obviously, the wear adaptability of the bone-TA2 pair seemed to be better
than that of the bone-TC4 pair (Fig.
7.5
). The abrasive wear and microfracture phe-
nomena were observed on the wear scar of cortical bone. In addition, some organic
matter ejected from the worn bone surface was examined, while its evolution at the
interface remains to be explored.
7.2.2
Radial Fretting Behavior
We performed radial fretting tests of the fl at cortical bone specimens from fresh
human femur against the titanium ball counterpart [
15
,
16
]. In order to maintain the
