I have no idea on how to proceed with this problem. The problem is: reducing the vibration in exhaust pipe line using rubber dampers and by counter weights. I have modeled a sample of exhaust pipe line and conducted modal analysis in ANSYS and found out the forces reaction and stress at each support points. But, I have retrieved the results for first 6 modes. For observation, which mode should I take as reference and also what input should i give for static analysis. Can I use the force reaction obtained from modal analysis as input for static analysis? I have just one week time gap.
I am not sure that am understand well your problem.Anyway, with the modal analysis you can get the the modal-displacement amplitudes of the response as well as postprocess it to obtain modal-reactions or modal-stress. They are not useful for static analysis because the modal analysis gives you the mode fi of free vibration and it is displacement=Constant*fi. And this Constant is undeterminated. If I am understanding your problem, to determine the reactions at each support points you should perform an harmonic analysis (steady-state analysis) which should not be difficult to you to perform in Ansys.
Ya sir, as your said for harmonic analysis, i find a problem in applying the loads. Harmonic analysis needs a load conditions, but i have no idea on what kind of load to be applied. thanks for information that, the output of modal cannot be applied for static analysis. And sir, i have came across a report(i have attached the report along with this), in which they have conducted static analysis using gravity as loads. There they have applied 10 times the gravity for worst condition. is that a assumption or is there any rules to be followed for selection 10 times the gravity. Also they have assumed the moment load as 100,000 N-mm. Can i use the same moment, or should i proceed without moment load.
Let us look only at the static analysis (and at this moment forget the harmonic analysis and other analysis mentioned in your pdf). From the pdf I understand that for the static analysis, you need to build the FE model with the displacement boundary conditions only. Next, impose an acceleration of 10 Gs (the worst scenary) which corresponds to apply an inertia force defined with that input data of acceleration (material density have to be defined at your model). Solve it to obtain the deflection. The hanger forces (reactions) are determined along with stresses using posprocessing. My quick interpretation is that the mentioned moment is for the dynamic analysis and not for the static one. So, it is not needed (in my opinion).
Ya sir, but, you have mentioned as "you need to build the FE model with the displacement boundary conditions only." Displacement boundary conditions - refers to what...? is that the output of modal analysis. (right now, i am in confusion)
I think you are using Ansys Workbench. I am not familiar with workbench but it should be straight forward if you select the proper constraints and model properties.
@Jawad: Ya sir, its Ansys Workbench and its ok sir, also the constraints are set accordingly and i have done the free vibration analyis. Now waiting for static structural analysis.
@Miguel Matos Neves : The FE model with displacement boundaries requires the phase angle value. the default value is 0 degree. As far as my Ansys classes are passed by, i can find the phase angle by using harmonic analysis. But for harmonic analysis i need hanger loads which cannot (shouldn't) be retrieved from modal analysis...
Now i am in confused state in further proceedings.
please mail me exhaust pipe model, I am also interested in this problem. if you don't have any problem with sharing ... [[email protected]]
boss...go through CFD...put the BC's....then you can study all vibration parameters..
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