hello Everyone,
Iam having a problem with the GA and Direct Search toolbox of MATLAB. Iam not able to find how to specify lower and upper bounds of design variables. How does one specify that?
In addition, if I want to specify equality and inequality constraints, how does one achieve it? Is it...
Hi,
I see that ANSYS has this new MPDMPR where damping can be specified for different materials..
With the full method in harmonic response analysis does MPDMPR formulate it according to the complex modulus approach?
Thanks.
-Emily
Em.
Hello!
With the introduction of ANSYS 8.1, there now seems to be two methods to represent material damping in a full harmonic response analysis (HROPT,FULL). They are:
---reference to exclusively the FULL method in the harmonic analysis--
a. MP,DAMP: Stiffness matrix multiplier representing...
Oh..This post is getting very inetresting..and Iam learning a lot of new stuff!!
Thank you very much Greg and Michael F Platten..It has answered a lot of questions.
I would be interested to know how to process the data if the shaker is at a compound angle.
Awaiting more discussion...
-Em
HI Greg,
Thank you for your response..
this raises a few questions (sorry to bother you again!)
Is there any mathematical explanation for this? Is there a name for such a behaviour? or any better explanation? or is it just a *common thing* in experimental modal analysis..I tried doing some...
Hello All,
Iam trying to get some modal results (nat freqs and damping constants) for a frame type structure.
Iam using a shaker excitation (periodic) to excite my structure in the 0-500Hz freq range. The problem Iam suffering is that, when I excite the structure in say Z direction, I miss the...
Hi Greg,
But Iam already working with Hz. during my harmonic analysis.
Do I still need to convert to radians?
Instead I thought it (variable 100) needs to be just sqrt(-1)
Please advice me if Iam wrong.
Emily.
Hello Everyone,
Thanks for helping me with the Mobility FRF problem.
Once I got my displacements from my ANSYS model, I created the following variables (working in Hz.)
created variable 100 (-1*Pi)
created variable 101 (100*freq)
created variable 102 (101*disp)
Variable 102 is mobility...
Ok Drej, Iam sorry..didn't read your post properly.
Yes, its ANSYS implementation was what I was after..Sorry if my post wasnt clear.
So, what I did was(working in Hz.):
created variable 100 (-1*Pi)
created variable 101 (100*freq)
created variable 102 (101*disp)
Variable 102 is mobility...
Again, everything you said is correct, but I dispute your 'fact' that velocities/accelerence cannot be obtained from a FE displacement result set.
Look at this thread..I had posted the same question:
http://www.eng-tips.com/viewthread.cfm?qid=115189&page=1
See, others do understand me...
I strongly feel you are wrong. There are tons of papers where researchers have calculated the velocity from response obtained from a harmonic analysis.
Velocity is simply {v}=j*omega*{u}
where {u} is nodal displacement and {v} the nodal velocity.
Emily
Hi Logesh,
Thank you for your response.
Yes, I need to create variables in time-history post processor and then plot the same.
Meanwhile, I was reading a book, and it said:
{v}=j*omega*{u}
I dont see the 2*Pi .. Is that to convert rad/s to Hz?
Thank you..
Sorry again, if the question was...
Thanks everyone for the response..yes, srinivas, iam trying to do something like what you have described exp frf vs fe-frf's. Modal analysis of a simple frame.
I have the computed displacements using ansys, so I now probably need to write a little code to multiply my displacements by...
Hello,
Iam trying to get a mobility plot (velocity/frequency) from my ansys model. I ran a full harmonic analysis and I have the displacements.
I would like to convert these displacements to velocities, to plot mobility FRF's.
Could anyone tell me how to do it in ANSYS?
Sorry if its a basic...
Hello,
Iam trying to get a mobility plot (velocity/frequency) from my ansys model. I ran a full harmonic analysis and I have the displacements.
I would like to convert these displacements to velocities, to plot mobility FRF's.
Could anyone tell me how to do it in ANSYS?
Sorry if its a basic...
