Question

Q.3. Three identical fatigue specimens (denoted A, B, and C) are fabricated from a nonferrous alloy. Each is subjected to one of the maximum-minimum stress cycles listed in the following table; the frequency is the same for all three Specimen Omax (MPa) Omin(MPa) tests. Rank the fatigue lifetimes of A + 450 150 these three specimens from the B + 300 300 shortest to the longest. с + 500 200

Answer 1

Ang. hriven: Speciman Tmax CMPa) Thin (MPa) A +45o 150 B +300 - 300 C + soo - 200 find mean Stress Vm = Tomax + Tmin 2 (TM)a 450-150 150 MPa 2 (Tm)s 11 300-300 2 (Tme 500-200 = 150mpa. 2 Tmax Now find min Ta= 2 Ta 450-6-150) = 3oompa 2 ((a)B - 30o-(-300) Boompa 2 (Ta) c = soo- (-200) = 350MPa 2

Im=150 Mpa Tan 3sompa 3oomla Nc MA Log cycles so NB) NA> Nc Rank so Speciman fatigul posed on of bcia life will B> ASC 'Ang.