9.29 Consider the data for AISI 4340 steel at various mean stresses from Tables E9.1 and E9.5. a. Calculate ar values for the SWT mean stress relationship, Eq. 9.18, for the combined data from both tables, and plot these versus life. Add the ar versus Nf line from the constants in Table 9.1, and comment on the success of the correlation. Table E9.1 %a, MPa 948 834 703 631 579 524 Nf, cycles 222 992 6004 14130 43860 132150 Table E9.5 Ja, MPa 379 345 276 517 483 414 345 345 om, MPa 621 621 621 414 414 414 414 414 Nf, cycles 73 780 83 810 567 590 31 280 50 490 84 420 437 170 730 570 Ja, MPa 310 552 483 414 586 552 483 om, MPa 414 207 207 207 -207 -207 -207 Source: Data in [Dowling 73]. Note: All prestrained 10 cycles at &q=0.01. Nf, cycles 445 020 45 490 109 680 510 250 208 030 193 220 901 430 (9.18) o ar = ar max a = omax 1 - R 2 (max > 0) (a) (max > 0) (b)