Hello. As far as i know harmonic response is strongly linear analysis. That mean no nonlinear effect like contact and so on. So, you should try use Transient analysis, thats support all kind of nonlinearity and after this process the results by Fourier transform.

hi dear oleksii

I know that harmonic response is a linear analysis but if a structure has a nonlinear effect,this nonlinear effect can be seen in the harmonic response.

I want to make model by Ansys, Abaqus, MSC nastran or LSdyna in which a nonlinear harmonic response can be seen.

thanks for your response.

Hello again. I am afraid that is impossible in direct way. Ansys or Abqus can obtain only a linear response. So, it will be a good idea to use transient analysis and manually process it results.

All of the above are correct. There is no direct way. however non-linear solutions are step by step. So long as you know the structural non-linearity of the system then you can use fea to predict one solution at a time, but you are going to need to perform the non-linearity of the solution yourself. Now you could be clever and get the solution to do this for you as it is able to cope with non-linear solutions. The problem will be to get it to do exactly as you want. i suggest you look at some non-linear solutions in other disciplines, such as rotating machines, to see what the issues are.

good luck

p

Hello Ehsan,

I feel your question is a little vague and thus I do not feel able to provide you with a very good answer.

I have done some research work on a nearly identical structure under harmonic excitation in the past. Please lookat the two published papers below:

https://www.researchgate.net/publication/250696771_Simplified_models_of_bolted_joints_under_harmonic_loading?ev=prf_pub

https://www.researchgate.net/publication/228665909_Experimental_and_theoretical_studies_of_a_bolted_joint_excited_by_a_torsional_dynamic_load?ev=prf_pub

Article Simplified models of bolted joints under harmonic loading

Article Experimental and theoretical studies of a bolted joint excit...

Hi Ehsan, here is what I did for a similar problem I solved sometimes ago.

I used the MSc/MD Nastran software to get the nonlinear solution in time domain (in particularly I used SOL 400) then I obtained the frequency response by implementing an FFT in Matlab. I hope this will help you as well.

dear friends,

thanks for your helpful answers

I made a harmonic force in the Ansys workbench and obtained a non-linear response, so I could compute FRF.

In this way I want to appreciate who help me in this regard specially:

Oleksii Vodka,

Peter Ogrodnik,

DR. Huajiang Ouyang,

Aria Tsam,

Alfredo Lamberti

You are welcome Ehsan. It is a success story. Well done, everyone!

Hi Ehsan, Quick question, what is the non linear response you got from a harmonic analysis? can you share the details with me? Cause I am able to just view results based on frequency and not time.

Your help will be much appreciated.

hi vivek

In ansys you can't model a nonlinear system in modal or harmonic analysis.

because these analysis have linear solution.

LSDYNA explicit. you can model the contact. linear or non-linear material. but a few seconds only of the time varying loading.

Have you managed to find a way for the frequency response function analysis of a nonlinear system in ANSYS Workbench?

yes,

I made a harmonic force in the Ansys workbench and obtained a non-linear response, so I could compute FRF.

Haw have you made a harmonic force? I need to apply sinusoidal force to a nonlinear system. I applied force as a function of time in the transient structural module. Now I need to do the frequency response analysis of that system. So what should I do now? Will FRF be helpful in this regard? Thanks

yes,I obtained the frequency response by implementing an FFT in Matlab.

I have received the time history data from the transient structural analysis in ANSYS. How can I make progress for the FFT in Matlab with those data?

Interesting