Learning Forum

[dada taka]

Hello,
I am going to do fatigue analysis for alloy 2024-T6 and alloy 2099. But in fatigue analysis settings there is "Fatigue Strength 
Factor (Kf)" section. What should i do in here? For the aluminium alloys, is there a general Kf value?

Thanks

[dada taka]

Is there anybody who can help ?

[danielshaw]

Kf is just a general modification factor (always equal to or less than 1.0) used to reduce the fatigue resistance.  For example, the test specimens used to develop the S-N curve are typically polished, but the actual material might have a rough surface finish.  Kf can be used include the surface finish effect.

[dada taka]

Is there a handbook, table or formulation on what the Kf value should be? I am not sure what value I should take.

[danielshaw]

No.  Typically Kf=1.  You need to understand how the S-N curve was developed and how the part was manufactured to assess if another Kf is appropriate.  Based on that knowledge, you might be able to find a reference that discusses the appropriate Kf.