Page 442 - Mechanical Behavior of Materials

442 Chapter 9 Fatigue of Materials: Introduction and Stress-Based Approach

8
50 Phenolic 6
S a , Stress Amplitude, MPa 30 S = 0 Diallyl- 4 S a
40
Epoxy
phthalate
m
Alkyd
30 Hz
ksi
20
Nylon (dry)
Polycarbonate
10
PTFE 2
Polysulfone
0 0
10 3 10 4 10 5 10 6 10 7
N , Cycles to Failure
f
Figure 9.23 Stress–life curves from cantilever bending of mineral and glass-filled thermosets
(solid lines) and unfilled thermoplastics (dashed lines). (Adapted from [Riddell 74]; used
with permission.)

σ , ksi
u
0 50 100 150 200 250 300
200
m = 0.6
e
1200
Carbon steels
Low-alloy steels 0.5 150
MPa Gray cast iron 0.4
Nodular cast iron
Limit, 800 Wrought iron ,ksi σ erb
Fatigue 100

,
σ erb 400 σ
400
erb = 700 MPa 50

0
0 400 800 1200 1600 2000
σ , Ultimate Tensile Strength, MPa
u
8
7
Figure 9.24 Rotating bending fatigue limits, or failure stresses for 10 to 10 cycles, from
polished specimens of various ferrous metals. The slopes m e = σ erb /σ u indicate the average and
approximate extremes of the data for σ u < 1400 MPa. (From data compiled by [Forrest 62].)