The fatigue data for a ductile cast iron are given as follows:

(a) Make an S-N plot (stress amplitude versus logarithm cycles to failure) using these data.
(b) What is the fatigue limit for this alloy?
(c) Determine fatigue lifetimes at stress amplitudes of 230 MPa (33,500 psi) and 175 MPa (25,000 psi).
(d) Estimate fatigue strengths at 2 × 105 and 6 × 106 cycles.

Transcribed Image Text:

Stress Amplitude MPa (ksi)l 248 (36.0) 236 (34.2) 224 (32.5) 213 (30.9) 201 (29.1) 193 (28.0) 193 (28.0 193 (28.0) Cycles to Failure 1 x 103 3 x 10 1 x 10% 3×10 1 x 107 3 x 10 1 x 10 3x 10%