steel - Nouvelle page 1 - Free

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MMPDS-01
31 January 2003
Maximum Stress, ksi
250
225
200
175
150
125
100
75
50
25
+
+
+
+
+
+
+ +
+ + +
AISI 4340 RT Kt=3.0
Stress Ratio
-1.00
0.00
+ 0.54
→
+ →
+ → →
→ →
→→→
Runout
Note: Stresses are based
on net section.
0
10 3 10 4 10 5 10 6 10 7 10 8
Fatigue Life, Cycles
Figure 2.3.1.3.8(o). Best-fit S/N curves for notched, K t = 3.0, AISI 4340 alloy steel bar,
F tu = 260 ksi, longitudinal direction.
Correlative Information for Figure 2.3.1.3.8(o)
Product Form: Rolled bar, 1.125 inch diameter,
air melted
Properties: TUS, ksi TYS, ksi Temp., EF
266 232 RT
(unnotched)
352 — RT
(notched)
Specimen Details: Notched, V-Groove, K t = 3.0
0.270 inch gross diameter
0.220 inch net diameter
0.010 inch root radius, r
60E flank angle, ω
Surface Condition: Lathe turned to RMS 10
Reference: 2.3.1.3.8(a)
Test Parameters:
Loading—Axial
Frequency—2000 to 2500 cpm
Temperature—RT
Atmosphere—Air
No. of Heats/Lots: 1
Equivalent Stress Equation:
Log N f = 7.14-1.74 log (S eq - 56.4)
S eq = S max (1-R) 0.51
Std. Error of Estimate, Log (Life) = 0.32
Standard Deviation, Log (Life) = 0.59
R 2 = 71%
Sample Size = 29
[Caution: The equivalent stress model may
provide unrealistic life predictions for stress
ratios beyond those represented above.]
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