Pretensioned Modal Frequency Response Analysis

Neeraj Kumar

Hello,

I am doing Modal Frequency Response Analysis with Pretension in the bolts.

First, I created Linear Static Subcase for pretension. (Please check the picture attached)

Then, I created Modal Frequency Response Analysis subcase, in which I linked the pretension subcase through STATSUB(PRELOAD). (Please check the picture attached)

The Pretension subcase is working fine and I can see the stress results in Pretension Subcase. (Please check the picture attached)

But, in the Modal Frequency Response Analysis subcase results, there's no pretension stress. (Please check the picture attached)

Why is this happening and how to resolve this?

I have also attached the .fem file and .out file. Please go through it.

Thank You.

viniciusgomes

Hello Neeraj, 

Please check the below statement from Sine Sweep Fatigue Analysis from our documentation:

https://2022.help.altair.com/2022.1/hwsolvers/os/topics/solvers/os/sine_sweep_fatigue_analysis_c.htm#concept_hgg_5dz_kbb 

 

In our documentation you can also find a tutorial for Sine Sweep Fatigue: https://2022.help.altair.com/2022.1/hwsolvers/os/topics/solvers/os/sine_sweep_fatigue_sn_damage_tutorial_r.htm#reference_i53_rbk_j3b

 

Hope this clarifies your question. Thank you!

Vinicius Gomes 

viniciusgomes

Hello Neeraj, 

This is the expected behaviour, STATSUB(PRELOAD) will only include the effects of preloading as a weakening or a stiffening of the structure, but the results from the prestressed analysis do not include the preloading results. See below:

Neeraj Kumar

Vinicius Gomes thanks for the information.

I have created a Pretension subcase, which is linked which the subsequent Modal FRF load step and this FRF load is given as the input for Sine Sweep Fatigue. 

But, if the Modal FRF load step doesn't include the pretension stress, then the stress obtained in the FRF results will be lower and so the fatigue life obtained in the sine sweep fatigue results will be inaccurate.

Then, what model changes should I do. Please guide?

Thanks.

viniciusgomes

Hello Neeraj, 

Please check the below statement from Sine Sweep Fatigue Analysis from our documentation:

https://2022.help.altair.com/2022.1/hwsolvers/os/topics/solvers/os/sine_sweep_fatigue_analysis_c.htm#concept_hgg_5dz_kbb 

 

In our documentation you can also find a tutorial for Sine Sweep Fatigue: https://2022.help.altair.com/2022.1/hwsolvers/os/topics/solvers/os/sine_sweep_fatigue_sn_damage_tutorial_r.htm#reference_i53_rbk_j3b

 

Hope this clarifies your question. Thank you!

Vinicius Gomes 

Neeraj Kumar

Vinicius Gomes thank you for the query solution.