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MMPDS-01<br />

31 January 2003<br />

Figure 2.3.1.3.8(i). Best-fit S/N curves for unnotched AISI 4340 alloy <strong>steel</strong> bar at<br />

1000EF, F tu<br />

= 150 ksi, longitudinal direction.<br />

Correlative Information for Figure 2.3.1.3.8(i)<br />

Product Form: Rolled bar, 1.125 inch diameter,<br />

air melted<br />

Properties: TUS, ksi TYS, ksi Temp., EF<br />

158 147 RT<br />

(unnotched)<br />

81 63 1000EF<br />

(unnotched)<br />

190 — RT<br />

(notched)<br />

98 — 1000EF<br />

(notched)<br />

Specimen Details:<br />

Unnotched<br />

0.400 inch diameter<br />

Surface Condition: Hand polished to RMS 10<br />

Reference:<br />

2.3.1.3.8(b)<br />

Test Parameters:<br />

Loading - Axial<br />

Frequency - 2000 to 2500 cpm<br />

Temperature - 1000EF<br />

Atmosphere - Air<br />

No. of Heat/Lots: 1<br />

Equivalent Stress Equation:<br />

Log N f = 16.85-7.02 log (S eq -40.0)<br />

S eq = S max (1-R) 0.80<br />

Std. Error of Estimate, Log (Life) = 0.42<br />

Standard Deviation, Log (Life) = 1.20<br />

R 2 = 88%<br />

Sample Size = 13<br />

[Caution: The equivalent stress model may<br />

provide unrealistic life predictions for stress<br />

ratios beyond those represented above.]<br />

2-53

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