Biomedical Engineering Reference
In-Depth Information
F
z
L
L1
Δ
z
Δ
z
F
z
Fig. 8.6 Torsion of the bar
¼
L
1
L
1
2
F
z
L
1
L
L
1
2
¼
F
z
L
D
z
¼ y
(8.37)
'
I
p
'
I
p
2
F
z
D
2
'
I
p
r
¼
z
¼
(8.38)
L
1
L
As in previous cases we have:
L
A
¼
S
L
B
;
L
1A
¼
L
1B
;
'
A
¼ '
B
;
S
(8.39)
I
PA
=
S
4
·
I
PB
Substitution of equation (8.39) into equation (8.38) gives:
2
'
A
I
PA
2
'
B
S
4
I
PB
r
A
¼
L
A
¼
L
B
¼
S
r
B
(8.40)
L
1
A
L
1
B
S
2
S
The examples (8.3.2.1), (8.3.2.2), (8.3.2.3), (8.3.2.4) show that the rigidity of
device
A
is always greater than the rigidity of device
B
by
S
times. In other words,
the rigidity decreases linearly with the microdevice size diminution.
8.3.3 Forces of Inertia
8.3.3.1 Force of inertia. Linear movement with uniform acceleration
A component of the mass
m
moves from point 1 to point 2 with uniform accelera-
tion (Fig.
8.7
). The distance between points 1 and 2 is
L
. The initial velocity is
V
1
,
and the terminal velocity is
V
2
.
