these are my notes on Unit 7 - Spare Part Surgery (SUR) AKA materials and lenses
well written and laid out
i am predicted an A* in a level physics
compatible with edexcel a level or AS level physics students
We can replace many tissues with prosthetics
eg . Skin
bone
lens in eyes
valve in hearts
cartilidge
some muscles eg heart
.
nerves (wiring)
When replacing mechanical tissues (movement /support) it is important ,
to
match the PROPERTIES of the original tissue with the replacement's.
Stiffness is of limited use as it is specific to a sample ,
so
that
generic property material
eg DENSITY
we need a
of a .
tells us how a material behaves when a force is applied
2
↓
--
YOUNGS MODULUS
Wh
↑--
Y
F
>
-
&
Al
- I
compressed
STRESS =
Oce Nim(pal [PREssum]
G
STRAIN tension th
E
YOUNG'S STRESS Strain
(Pa) is unitless
=
as
MODULUS RAIN
-
E - o
S
STRESS (Pa)
E o
vo = YOUNGS
T MODULUS E
STRAIN E
, BONE
E = 2x10"Pa-HUGEi need big forces to deform bones by
small amounts
CARTILAGE STEEL COPPER
E = 5x10
°
Pa E = 2x10"Pa E = 1 -
2x10"Pa
Im
T
↑
Y
↑
am
3m 3m
== 2x10n
IIm
-
&
10 cm
(0" 33x10"Pa
E-
= f = = 0 .
6
3
= =
E =
3340" = 0 .
33x10
o 565
=
3
m
= .
3
3 =
0012 = 4 8x10-
.
01 = 1 2c m
.
2 5
.
z =
22565x102 =
7 .
43x10'4Pa
3
4 8x10
-
.
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