Modal Frequency response analysis

sravankumar

Hi i am performing Modal Frequency response analysis for  motor assembly in optistruct but i am getting zero displacement values when giving unit excitation load. Please do the needful.

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

Rahul Rajan_21763

Please try plotting curve using h3d file.

sravankumar

Thanks for your response sir. I am attaching my deck file, could you please check whether the load collectors are correct or not. 

Unable to find an attachment - read this blog

Rahul Rajan_21763

Could you also share .out file of the run?

sravankumar

Yes sir

Unable to find an attachment - read this blog

sravankumar

Replying to previous comment, there is no difference by plotting the curve using h3d file. 

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

Rahul Rajan_21763

I guess the issue is with frequency range defined in Freq card and Tabled1.1st frequency of the assembly itself is 345hz and you are evaluating it for 100hz.

sravankumar

Actually the maximum speed of the motor is 3200rpm i.e., 53.33Hz . If we give the frequency range from 345Hz means it will be exceeding the maximum speed of the motor-pump assembly.

I am attaching the frequencies attained from Modal analysis.

Please do the needful.

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

sravankumar

Replying to the previous comment, after changing the frequency range to 0-1000 Hz the displacement is zero. 

Please do the needful.

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

Simon Križnik

Hi,

 

you are getting zero displacements because the output set contains 8 nodes constrained by SPC in all DOF. Only unconstrained nodes should have non-zero displacements.