Fatigue analysis Minimum life is coming less than 1

Altair Forum User

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?

 

Altair Forum User

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

@ 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

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

Hi @bhumkaromkar

 

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