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

  • Thread starter Thread starter amitjakob
  • Start date Start date
  • Tags Tags
    Diagram
Click For Summary
SUMMARY

The discussion centers on calculating the stress ratio, maximum and minimum stress for a tensile bar made of 30CrNiMo8 under specific loading conditions (Fmax=72kN and Fmin=12kN). The stress ratio is calculated as Fmin/Fmax, while the maximum and minimum stress values are derived from the Goodman-Smith diagram, with the professor suggesting a maximum tension of approximately 900MPa and a minimum of 240MPa. The Goodman-Smith diagram is referenced as a crucial tool for understanding material fatigue strength, particularly in relation to Wöhler diagrams.

PREREQUISITES
  • Understanding of material fatigue strength concepts
  • Familiarity with the Goodman-Smith diagram
  • Knowledge of tensile loading and stress calculations
  • Basic principles of safety factors in engineering
NEXT STEPS
  • Study the Goodman-Smith diagram in detail
  • Learn about Wöhler diagrams and their applications
  • Research material properties of 30CrNiMo8
  • Explore calculations involving safety factors in mechanical design
USEFUL FOR

Mechanical engineers, materials scientists, and students studying fatigue analysis and stress calculations in engineering applications.

amitjakob
Messages
17
Reaction score
0
For material fatigue strenght.
Does anyone know about a source where i can read about them ?
unfortunately 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.
 
Engineering news on Phys.org
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?