General Mechanical

General Mechanical

unable to find FOS using fatigue tool

    • KumarVaibhav
      Subscriber

      I am simulating a case similar to a cantilever but i am not able to find the FOS using fatigue tool?However i have been able to find the FOS using stress tool.CAN SOMEONE EXPLAIN ME the difference between the two.What is the significance of the two.My geometry shows different regions with FOS marked by colour notations.pls explain

    • Sandeep Medikonda
      Ansys Employee

      Hi Vaibhav,


      Fatigue Safety Factor is a contour plot of the factor of safety with respect to a fatigue failure at a given design life. The maximum Factor of Safety displayed is 15. For Fatigue Safety Factor, values less than one indicates a failure before the design life is reached. 


      In a Stress Life fatigue analysis, one always needs to query an SN curve to relate the fatigue life to the stress state. Can you confirm if you have this in your Engineering Data because the error is pointing to missing/invalid data?


      Safety factor in the stress is a term describing the load carrying capability of a system beyond the expected or actual loads just in that analysis. This is typically calculated based on the Maximum shear stress but there are other options available. So the selected failure theory selected predicts a minimum safety factor of just over 1.


      Hope this helps,


      Regards,


      Sandeep

    • melalisa96
      Subscriber

      Hi Sandeep


      Can I just check, where in Engineering Data do I include the SN curve? Because I have input all the data required but I just can't seem to get the 'correct' safety factor out? It all shows me 15. 

    • peteroznewman
      Subscriber

      Helpful post.


      In that image, you can see the Toolbox on the left has a Life category and the S-N Curve object has been added to the material, Structural Steel and the data for the curve added.

    • 1KarthiKEYAN
      Subscriber

      Hi, u can add it in altenating stress in ur engineering data...it will already present for structural steel as default..check over it..

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