Frequency Response and Random Response (Dynamic Response in Nastran)

[@muslimmukhtarkhanov8194]

an excellent lecture

[@captainvlog]

Dang, how do I even still have a job when you've turned what I do into something so simple! haha. Great presentation.

[@ManuelRamsaier]

Thank you very much for this video, it helped me understand PSD analysis quite a bit!

[@_Wai_Wai_]

I was actually on the WFIRST program at Goddard a few months ago. What a small world.

[@claude7473]

Interesting if the sound were not so distorted, words keep escaping my ears... recording sound thru a secondary connection instead of the original source is a terrible idea.

[@natarajanvenkatasubramania9721]

Hi, In the Random PSD plot, in the out put is it possible to evaluate the G value (Gpeak) for a particular frequency. How can I do that? There different versions to find the Gpeak is floating around. I need to find the correct one. Thanks.

[@CADIS_Software]

Thank you, Structures Aero!

[@stevengrobler4608]

Thanks for this example, I found it very useful. All of the random excitation examples I seen have a flat PSD for the input, which I suppose is essentially the definition of random. Supposing I want to use a PSD that is more peaky, ie it has peaks at harmonics of the machine operating speed - is the analysis still valid? For example are the 1-2-3-sigma percentage breakdowns still valid? Also, supposing I want to know the 0-sigma stress how do I find that value? One more question - if I have measured input PSDs in the X/Y/Z directions is it possible to apply a different PSD to each direction?

[@Tracks777]

Great content. Keep it up!

[@jrharrison3]

The input PSD you show at 34:58 doesnt match what you plot at 41:20. Do you know why? I appreciate your help.

[@jrharrison3]

I figured it out. From ---> community.plm.automation.siemens.com/t5/3D-Simulation-Femap-Forum/Random-Response-Analysis-ASD-Units/td-p/407823 "....For random response analysis, the loading is a unit acceleration( 1g) applied in the frequency response portion of the solution. If you want all of the response quantities(accel,force,stress etc) to have proper units, then this would 9.81m/sec^2 This means after scaling by the ASD, your acceleration results are actually (m/sec^2)^2, which may not be so handy to look at(since your input ASD is g^2/hz). But with Femap charting, you then scale the acceleration results back into g^2/hz by dividing by (9.81m/sec^2)^2 A good check to make is to always request accel response for your base drive node, it should match your input ASD if you are consistent with units. ..."

[@nitinks5140]

@@jrharrison3 thanks for letting others know what you figured out. 😃

[@mono7891]

Great explanation but would have liked it more if cards were shown in text editor.

[@upendranvs]

When i tried to solve im getting FATAL Error please help me in this USER FATAL MESSAGE 3046 (SQFREQ) THIS FREQUENCY RESPONSE ANALYSIS HAS NO EXCITATION SPECIFIED FOR IT. where to define a excitation

[@alexsanaei2931]

Hi, did you find the answer ?

[@Catlovers280]

Yes

[@nitinks5140]

Thank you Sir.

[@nghialuu2203]

Where can I download models? Thank you

[@myfem3102]

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