Goodman-Smith Diagram: Calculating Stress Ratio, Max & Min Stress for 30CrNiMo8

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The discussion focuses on calculating the stress ratio, maximum and minimum stress, and necessary diameter for a tensile bar made of 30CrNiMo8 under specific loading conditions. The stress ratio is calculated as Fmin/Fmax, while the maximum and minimum stress values are derived from material limits, with references to the Goodman-Smith Diagram for guidance. The user seeks clarification on interpreting the Goodman-Smith Diagram, which combines Wöhler diagrams, but finds existing resources inadequate. The professor's suggested stress values differ from the user's calculations, prompting a request for further assistance. The conversation highlights the need for clearer explanations and resources on material fatigue strength and diagram interpretation.
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For material fatigue strenght.
Does anyone know about a source where i can read about them ?
unfortunatly google doesn't 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.
 
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I'm going to ressurrect this topic, because I need a little help

In some of my assigned reading, a "Smith Diagram" is explained, but poorly. I get that it's a combination of Wöhler diagrams, but I don't understand how to read it - can anybody help with this?
 

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