Question

A steel rotating-beam test specimen has an ultimate strength, Sut of 1600 MPa (232 kpsi). Estimate the life of the specimen if it is tested at a completely reversed stress amplitude, Orev, of 900 MPa. Take the value of the fatigue strength fraction, fto be 0.77 The life of the specimen is cycles.

Answer 1

Given that - ultimate Skolength of the material Sut= 1600 mpa reversed stress amplito de = 400 MPa fatigure strength fraction = 0.77 6 endorana strength Se= 0.5 sut = 10° asl Se= (6.5) C16oo) = 800 mpa fatigue strength spo 0.77 sut - L=103 cu 1232 mea from in basquin Power law Az GCLB - ) A = (800) C1063) ?) Az (1232) (103B). elo (1232) 1038 =) B= 0.0625 Put B in A= 800 C10 (0.0625)6)] 1897.28

0.0625 1897.28 z (o) (L) o-) 900 mea [z? 0.0625 => 1893. 28" = (900) (L) =) Le 152016.65 cyclu The life of the specimen