-Nominal stress amplitude versus cycles to failure data are given in Table P10.35 for completely reversed loading of notched members of 2014-T6 aluminum. The axially loaded test specimens were circumferentially notched round bars, with diameter in the bottom of the notch d1 = 10.16, major diameter d2 = 12.70, and notch radius ρ = 0.813 mm, giving an elastic stress concentration factor of kt = 2.65. Nominal stress S is defined based on the net area corresponding to d1, and the notch surface was polished. The material’s tensile properties were yield 438 MPa and ultimate 494 MPa. Estimate the nominal stress versus life S-N curve by the method of Juvinall, and graphically compare estimate and data.

-Nominal stress amplitude versus cycles to failure data are given in Table P10.34 for completely reversed (R = −1) loading of notched members of normalized SAE 4130 steel with yield strength σo = 679 MPa and ultimate tensile strength σu = 807 MPa. The axially loaded test specimens were double-edge-notched plates, as in Fig. A.11(b), with (net area) nominal stress S defined as shown. The dimensions were w1 = 38.10, w2 = 57.15, notch radius ρ = 8.06, and thickness t = 1.905 mm, giving an elastic stress concentration factor of kt = 2.15. The notch surface was electropolished. Estimate the nominal stress versus life S-N curve according to the procedures of (a) Juvinall and (b) Budynas. Then plot both estimates along with the data and comment on the success of the estimates.