General Design Principles for DuPont Engineering Polymers - Module

Figure 4.05 Creep in flexure of Zytel ® 101, 23°C (73°F), 50% RH
Strain, %
Figure 4.06 Isochronous stress vs. strain in flexure of Zytel ® 101, 23°C (73°F), 50% RH
Stress, MPa
5
4
3
2
0
0.001
20
15
10
5
1
0
0
Bending Load
If the same tubular part were used as a simply supported
beam loaded at the center with a 10 pound force,
then after 5000 hr what is the stress and deflection?
I = (Do4 – d4 )π 4 = 0.0169 in
64
Max Moment = WL = (10) (6) = 15 in·lb
4 4
S = Mc = (15) (0.5) = 444 psi
1 0.0169
13.8 MPa (2,000 psi)
0.01 0.1
1.0 10
100
1,000 10,000
Time, hours
0.
1 Hour
1
H
r
u
o
1
0
0
o
H
u
r
s
25
6.9 MPa (1,000 psi)
3.5 MPa (500 psi)
0.5 1.0
1.5 2.0
2.5
3.0 3.5 4.0
Strain, %
,
5
0
0
0
H
o
r
u
s
– 2,500
– 2,000
– 1,500
– 1,000
– 500
Stress, psi
From Figure 4.06, the strain at 444 psi after 5000 hr
is 0.6% or 0.006 in/in. Therefore, the apparent
modulus (EA) = 444 = 74,000 psi
.006
Thus, the deflection
y = WL3 = (10) × (6) 3
= 0.036 in
48EAI (48) (74,000) (0.0169)