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The geometric parameters are listed below:
symbol parameter (mm)
l Pitch length 5.65
l1 Bead width 3.2
l2 Width of the film part 3.35
r Radius of the bead (1/2 of l1) 1.6
h Height of the side ring of the bead 0.75
H
Height from HADT centre axis to the top of the side ring of the
bead
When the origin of the co-ordinators is as in the figure above, the expression of the
semi-circle is:
2 2 2 2 2
y r ( x r) H 1.6 ( x 1.6) 10.4 3.2x x 10.4
So the semi-circular revolved surface area is [70]:
3.2
2
Acb 2 y 1 ( y) dx
0
Where
Thus
y x x
2 1/2
[(3.2 ) ]
1.6 x
3.2x
x
2
and
- 188 -
1 ( )
2
y
2.56
3.2x
x
2
3.2 3.2
2
3.2x x 10.4
0 =360.63 (mm
0
2
2 )
Acb 2 y 1 ( y ) dx 2 2.56 [ ] dx
3.2x
x
The area of the two flat rings (see Figure IV 3):
A 2 ( H R ) 2 (10.4 9.65 ) =94.48 (mm 2 )
r
2 2
2
2 2
The two parts of the film are like two frusta of cones (see Figure IV. 1) and the area can
be calculated as:
l2
2 2 2.95 2 2
Af 2 [ ( R1 R2 ) ( ) ( R1 R2)
] 2 [ (10.35 9.65) ( ) (10.35 9.65) ]
2 2
=205.17 (mm 2 )
2
.
10.4