Learning Forum

[akndnzmn]

Hello,

I want to apply 3 loads in 1 cycle and 1 cycle should be like 1 second in static analysis fatigue tool. I thought used tabular data would be enough but I'm not confident about it. Can anyone explain how should I define 3 (same magnitude) loads in 1 second as a cycle, and get results as a life cycle. Also I use structural steel as a material, and acording to theory I choose gerber equation. Will it be enough to calculate?

Lastly in real life case I use EN-GJL-300 but since finding en gjl 300's S-N Curve is hard, can I use Structural Steel to calculate fatigue life? 

[danielshaw]

You have at least 2 options.

1.       You are just repeating a 0-25 MPa pressure cycle.  You can solve the model for a 25 MPa loading and use Constant Amplitude, Proportional loading in the Mechanical Fatigue Tool to calculate the life as the number of repeats of the 0-25 MPa cycle.  If you want the life to be reported in repeats of 3 cycles, you just need to divide the calculated life by 3.

 

2.       You can solve the model for a 25 MPa loading and use Non-Constant Amplitude, Proportional loading (history loading) in the Mechanical Fatigue Tool to calculate the life as the number of repeats of the loading history.  You would define a load history file that contained the following factors: 0, 1, 0, 1, 0, 1.

[akndnzmn]

Sorry for late reply, but thank you. Second method saved my life, but I wonder that does Bin Size or Display Time have any impact on the results that I found?

[danielshaw]

The bin size can have an effect, but the defect setting is almost always adequate.  You can request more bins to verify, but I doubt that the results are signficantly affected.

[akndnzmn]

Thank you daniel you helped me a lot