Relation stress life-FOS fatigue analysis - Torsion fatigue limit

LZanell

Hello,

I open this discussion because, in the SIMLAB fatigue analysis I raised the question related the Torsion fatigue limit. In detail is a parameter that I cannot find in material datasheet and also into the Altair material database is a parameter.

Considering that I would like also to run not only stress life fatigue analysis but also FOS analysis I think it's important to set the right parameter.

As alternative, there is a way to calculate Safety factor in SIMLAB staring from stress life fatigue analysis?

thanks everybody

solon

Hello,

In general the torsional fatigue limit can be obtained from fully reversal torsion testing.

To calculate the Safety factor in SIMLAB from stress life fatigue analysis, you can follow the bellow steps:

Output the .fem file, manually edit it in a text pad and run the analysis outside SIMLAB with Compute Console (Optistruct). In the .fem file under the FATPARM bulk data entry add the FOS continuation line, specify the method (constant mean stress or constant stress ratio or scale) and the target life at which the Safety Factor is evaluated.

Optistruct documentation section bellow:

https://2024.help.altair.com/2024/hwsolvers/os/topics/solvers/os/fatparm_bulk_r.htm#fatparm_bulk_r__fatparm_bulk_r_li_mvj_fry_kzb:~:text=Flag-,indicating,-that%20Safety%20Factor

Additionally, add the FOS I/O Option inside the Fatigue subcase definition to generate the safety factor output in the .h3d file.

Optistruct documentation section bellow:

https://2024.help.altair.com/2024/hwsolvers/os/topics/solvers/os/fos_io_r.htm?zoom_highlight=fos