Fatigue analysis Minimum life is coming less than 1

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Hello all,

I have done static analysis of the structure using static load case of 971N. I have applied Fully reversible sinusoidal curve (100 cycles) for fatigue analysis in optistruct. SN curve is calculated in optistruct using UTS. After analysis i am getting minimum number of cycle as 1.581e-2 which seems unrealistic.

What can be the problem?

 

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited March 2017

    Hi,

     

    Fatigue life is mainly dependent on b and fatigue strength coefficient. Check the parameters and Stress amplitude is directly available from maximum and minimum loads and try again. 

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited March 2017

    @ Prakash Pagadala 

    I am using SN life method for stress calculation.

    For this SR1, B1 and NC1 values are directly estimated using UTS in fatigue process manager.

    I have used this approach. Are their any additional values needed ?

    TIA.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited March 2017

    I used following values 
    YS= 340 MPA
    UTS =  497 MPA
    Values calculated in Fatigue process manager for SN curve Plot (Estimated based on UTS option)
    SR1 = 2118.71
    B1= -0.125
    NC1 = 1e6
    B2, FL, SE are OFF.
     

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited March 2017

    Hi @bhumkaromkar

     

    What about Stress amplitude. I think this is what causing the problem. 

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