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Roy Duan

How to output reaction force frequency response?

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Hello everyone,

      A  frequency response analysis was done, and I want to get the reaction force frequency response at the SPC nodes. The following control cards were used. However, I cannot get the reaction force frequency response.

FORMAT OPTI    
FORMAT H3D     
OUTPUT,HGFREQ,ALL
SPCFORCE(H3D,REAL) = 1

 

Which output control should be used to get the reaction force frequency response? 

 

 

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5 hours ago, Prakash Pagadala said:

Hi @Roy Duan

 

Can you try with .pch format instead of H3d?

Hi Prakash,

From the manual,  The Nastran punch file format (.pch file) is output. I think this file should be viewed by Nastran.

It's so strange that I can get the displacement frequency response by the output control I mentioned before. However, I cannot get the reaction force frequency response. How should I do?

 

Best Wishes

Roy

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12 minutes ago, Roy Duan said:

The Nastran punch file format (.pch file) is output. I think this file should be viewed by Nastran.

Yeah but it is possible to plot the graph in HyperGraph.

 

I am able to see SPCforces and moments on a test model. Can you remove the output format and try again?

Freq4.fem

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1 hour ago, Prakash Pagadala said:

Yeah but it is possible to plot the graph in HyperGraph.

 

I am able to see SPCforces and moments on a test model. Can you remove the output format and try again?

Freq4.fem

Hi Prakash,

Maybe I have not expressed my problem clearly. I want to output the reaction force vs frequency curve at some spc nodes. I have ran the input file you provided, However, I cannot get the spc node reaction force VS frequency curve by HyperGraph. 

I wish I have expressed my question clearly. 

 

Best Wishes

Roy

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12 hours ago, Prakash Pagadala said:

Hi Prakash,

From the video you provided, the curve was about force amplitude VS Angle at certain frequency. 

However, my purpose is about outputting force amplitude VS frequency, that is the abscissa axis of the curve is frequency not angle.

How should I do to get this curve?

 

Best Wishes

Roy

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1 hour ago, Prakash Pagadala said:

Roy,

 

The methodology is same. In-fact you can load the h3d in HG and plot graph.

HG.PNG

Hi Prakash,

Thank you for your reply. The spc force frequency response can be gotten by reading H3D file into HG.

From the example of optistruct frequency response help, the amplitude VS frequency curve can be viewed by open _freq.mvw file. However, this file cannot be gotten for spc reaction force.

DisplacementFrequencyResponse.thumb.png.3138da9deca7d268b0330500f62c494f.png

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Hi all,

Is it possible to get a section (with multi nodes) force frequency response curve in a direct frequency response analysis? I think the phase of this nodes were not the same. So we cannot get the section force by simply plus force frequency curve of every node.

 

How to solve this?

 

Best Wishes

Roy

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Hi @Roy Duan

 

As said, SPCF with set of grids is available from OS but such diagnostics to check the phase needs to be done in post-processing.

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10 hours ago, Prakash Pagadala said:

Hi @Roy Duan

 

As said, SPCF with set of grids is available from OS but such diagnostics to check the phase needs to be done in post-processing.

Hi Prakash,

I don't think I have gotten your meaning. Could you explain it detailedly ?

 

Thank you

 

Roy

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Hi Prakash,

As you said, I have gotten the SPCF frequency response curve by reading the .h3d file into HyperGraph.

In the Y component, does the MAGI X and PHAI X mean amplitude and phase respectively?

In addition, from the figure blew, different FRF curves have different phase for different nodes, so how to evaluate the total SPCF frequency response for a constrained location with several nodes?

59534267d5cb6_SPCFcurveplot.thumb.JPG.bd0dbb3063c6d4e249ec5c241cc88576.JPG

 

5953427e4e1f6_SPCFFrequencyResponse.thumb.JPG.1a932c86babf5cdd21c22f9af4c55ea6.JPG

 

Could you give me some advice? Thank you.

 

Best Wishes

Roy

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