FRF with Excitation g value and moment

Teja_21569

Hello,

 

I want to carry out frf analysis in which Excitation g value coupled with moment. Can i carry out that analysis.

 

Thanks in advance

Teja_21569

Altair Forum User said:

Hello,

 

I want to carry out frf analysis in which Excitation g value coupled with moment. Can i carry out that analysis.

 

Thanks in advance

  Hello,

 

Can anyone help with this

Rahul Rajan_21763

Yes its possible...For acceleration you should use SPCD card and in RLOAD2 you can call moment (EXCITED)and acceleration(TB).

Teja_21569

Altair Forum User said:

Yes its possible...For acceleration you should use SPCD card and in RLOAD2 you can call moment (EXCITED)and acceleration(TB).

Thanks for your reply can you please explain how to define in RLOAD 2 . i can call either SPCD or force (for this case i am going with force) it is just a trail run.  

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Rahul Rajan_21763

Please refer attached deck for accel and ext force.In place of external force you can use moment.So need to have two RLOAD2 card and combine them with DLOAD card.

Unable to find an attachment - read this blog

Teja_21569

Hello sir, @Rahul R

 

I have  defined the SPCD in Rload and moment in Rload and combined them in Dload but i can't see the effect of moment and stress are very less. To verify i have applied only moment, from the displacement contour it is considering the Moment.  

 

I want to find out stresses when vibrating along SPCD and with moment,

 

Thanks in advance,

 

Regards,

Teja  

Rahul Rajan_21763

Dont create two rload2 card .Create moment with spcd load collector as active.

Teja_21569

hello sir , @Rahul R

 

It is not working sir, i think it is not taking moment.

 

Thanks in advance

Rahul Rajan_21763

Please ignore my last comment.Having two Rload2 card should work. For applying Moment you need to use the Analysis > moments option.SPCD is meant only for enforced motion excitations like Displacement / Velocity / Accelerations.I have attached a sample deck for Moment loading.

Unable to find an attachment - read this blog

Teja_21569

Hello sir, @Rahul R

No sir it is not working,

 

Let me explain my problem. My assembly consists of knob and rotor. A max moment of 24.7 N-m is applied on knob. But this assembly is placed on engine so, it always works under of vibrations. To find stress in knob and rotor assembly we need vibrate the assembly for that i need to give (spcd) and apply moment on knob parallel. For that i am applying SPCD in RLOAD2 and moment in RLOAD2 and combining them in Dload. 

 

But in results i couldn't see moment in knob, for checking my load card defined  correctly or not i went only with moment ( No SPCD) i could see moment at knob.

 

if you want i can share .hm file in secure dropbox

Rahul Rajan_21763

could you please share your .fem and h3d files to take a quick look?

Teja_21569

Hello sir, @Rahul R

I have already shared file. Please update the status

 

Thanks in advance 

 

Rahul Rajan_21763

Can you also share the fem and h3d file where you considered only moment load?

The file which you shared contains both acceleration and moment load. I also see you are not considering damping for the analysis.

You can give a try in above shared simple file with moment load then second run with moment + SPCD.

Rahul Rajan_21763

The files which you shared today still contains DLOAD with accel and moment.So it will have the effect of both.As mentioned above you can try this on simple file and test.

Teja_21569

Altair Forum User said:

The files which you shared today still contains DLOAD with accel and moment.So it will have the effect of both.As mentioned above you can try this on simple file and test.

 

Hello sir,

please check in loadstep i have specified only moment as input.

 

thanks for your reply

Rahul Rajan_21763

Sorry i just realized.I took a quick look in to stress output and observed difference in both case.Model with moment load is getting high stress (463) wheareas in accel/moment case we are getting very less stresses(negligible 1.51e-02).Logically we should get high stress for accel/moment case but since we are applying accel for a given freuqency range which led the structure to move along y direction which  also nullify the effect of moment.I guess this the reason for getting low stresses.