For material fatigue strenght. Does anyone know about a source where i can read about them ? unfortunatly google doesnt give any reasonable options, or maybe someone here will be ready to answer my question for the problems ive encountered with them. And the Problem: A tensile bar made of 30CrNiMo8 is subjected to swelling loading Fmax=72kN and Fmin=12kN. Please Calculate: a. Stress Ratio b. Max and Min. Stress c. Neccesary diameter of the bad in this case with a safety factor 1.7/ So, my attemt was: a. Stress Ratio is simple Fmin/Fmax , i know this question is kinda mocking the intelligence of the people here, but i though it might lead to the right solution. b. Max and Min Stress: The table i have shows for that metal allowed limit stress of 870Mpa, the G-S Diagram shows range of 800Mpa to Zero. Solution of my proffesor was Max tension of 950~900MPa and Min 220~260Mpa. I would say these values are on the same vertical line in the Goodman-Smith diagram, but with no special notance, would appreciate of someone can give a hint. All the best, Amit.