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Random Response Analysis

Hello sir,

I am currently using MSC Nastran, Patran for random response anlysis because it is quite easy. I want to do that in hypermesh/optistruct. but the tutoril does not match with my requirement.

1. I have input in terms of acceleration as base excitation.

2. I have Frequency Input 20 to 2000 Hz with 100Hz increment.

3. I have a critical damping condition of 0.3.

4. I have PSD Input as follow

20 Hz- 0.056

100Hz - 0.28

700Hz- 0.28

2000 Hz- 0.0343

5. I want peak g rms and g rms at few nodes. I also want Von-Mises stress.

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Rahul Rajan_21763

Hi,

In tutorial we applied force.Hence we used DAREA card. Replace DAREA with SPCD for acceleration as base excitation.

See attached solver deck.

Regards

Rahul R

Unable to find an attachment - read this blog

Altair Forum User

Will you Please elaborate about cards like PARAM,G? and

How to specify the value of that?

can you please make an FEM file which is consistent with my inputs? So, It would be very helpful and I can co-relate easily.

-Thank you

-Nirav Modi

Altair Forum User

Hi Nirav Modi,

G is the Structural damping coefficient. Here G= 2* C/C0 (2 times the critical damping ratio)

Altair Forum User

I also want PSD respose curve at some selected node also.

I also want g r.ms value at base and some selected node . How can i get that ?

-Nirav Modi

-Thank you

Rahul Rajan_21763

Hi,

Could you please ask for the below output request

Acceleration (psdf) = all

This should write out both PSD and RMS responses to .h3d file which can import to HG to plot the curves.

In option set it to SID for Selected node set.See attached screenshot.Refer user guide for acceleration output.

Regards

Rahul R

<?xml version="1.0" encoding="UTF-8"?>

Unable to find an attachment - read this blog

Altair Forum User

I want to do for Acceleration(PSDF)=All .

but I also want PSDF-acceleration response curve for the base node and some selcted nodes. in a single graph for comparison .

In my friend's pc, using the same version of hypermesh, it doesn't show the option of Random(1) in acceleration and displacement ( in Global_Output_request ). It only shows for stress only. I also tried to change solver template but it was of no use. Please help me with that !

and your attachment Gr.m.s is not properly attached. I am unable to open it.