Strain vs. Stress Fatigue Analysis Result

- May 15, 2024 at 5:58 am
  
  Jeonee
  Subscriber
  
  Hi,
  I have done fatigue analysis which was result 4523 cycle in stress-life, so I decided to do strain-life analysis because of the 4523 cycle. After the strain life analysis, I found the result as 15312 cycle. Which cycle must be chosen? 4523 or 15312? Can you help me, please?
  Sincerely,
- May 15, 2024 at 1:33 pm
  
  danielshaw
  Ansys Employee
  
  Do the elastically calculated stresses exceed the material yield strength? If so, then the SN results maybe suspect, and the EN results maybe more accurate. However, often SN test data is more extensive and reliable than EN data for the same material, so the SN result might be based on superior test data.
  Note: SN and EN test data are developed using different test methodologies and the failure criteria are different, so I would not expect SN and EN to produce identical results. 4,500 vs 15,000 predicted cycles between them is not a signficant difference.
  - May 20, 2024 at 1:16 am
    
    Jeonee
    Subscriber
    
    Normally, I did 1N fatigue analysis whose result was 192 MPa. There was 2,5N load which had 460 MPa (the material's yield strength is 450 MPa) in time-series method in nCode designlife. In this way, the cycle is lower than 10^4 cycles, and I decided to do low-cycle fatigue analysis.
    In addition, I want to learn that I do nonlinear static analysis (because of the nonlinear contacts) , but nCode calculates the result as linear superposition. Must I do transient analysis or not?