# How to start modal analysis

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 January 12, 2006, 02:30 How to start modal analysis #1 Mvaz Guest   Posts: n/a hello to all of u I have a question how to start modal analysis on ansys. can u light on that? pl.

 January 12, 2006, 03:22 Re: How to start modal analysis #2 Ahmed Guest   Posts: n/a This is not the right forum to answer your question! But if you read the tutorials of Ansys you will get the answer, good luck and cheers

 January 12, 2006, 03:51 Re: How to start modal analysis #3 mvaz Guest   Posts: n/a i have gone through the tutorial that given in ansys help but i have a problem how to decide load and how to apply it? thxs

 January 12, 2006, 03:56 Re: How to start modal analysis #4 HVN Guest   Posts: n/a You could apply the loads on nodes, surfaces

 January 12, 2006, 04:54 Re: How to start modal analysis #5 Alex Muthaiah Guest   Posts: n/a Hi, Eventhough my specialisation is in CFD I can help u Modal analysis is a type of Dynamic analysis where in u r going to extarct natural frequencies of a structure.Required parameters for this is density of the structure and proper boundary conditions. Define number of modes u need extarct(generally first5),method of extraction its better to go for Lanczos method . which gives first 5 modal frequency values after solution the interpretaionis if anyone of the above frequency matches with ur operating one resonance will occur.Pls go through the tutorial of MODAL ANALYSIS OF A CANTILVER BEAM. regards Alex

 January 12, 2006, 08:33 Re: How to start modal analysis #6 Peter Attar Guest   Posts: n/a It's a modal analysis..ie eigenvalue problem therefore you don't apply loads.

 January 12, 2006, 10:58 Re: How to start modal analysis #7 HVN Guest   Posts: n/a What about fixed point or fixed surface?

 January 12, 2006, 11:07 Re: How to start modal analysis #8 Peter Attar Guest   Posts: n/a Well if you apply a static load in a nonlinear analysis you can then use the subsequent tangent stiffness matrix generated via the displacement due to this applied load in a modal analysis...but I don't think that is what the original poster was looking for.

 January 13, 2006, 03:17 Re: How to start modal analysis #9 HVN Guest   Posts: n/a OK thanks for the information

 January 16, 2006, 04:07 Re: How to start modal analysis #10 mvaz Guest   Posts: n/a how do v decide the no of mode to extract and the method to extract? does there any theory regarding this?

 January 16, 2006, 08:40 Re: How to start modal analysis #11 Alex Muthaiah Guest   Posts: n/a Hi I think I have already told u 1)The number of modes depends upon the number of DOF of the systems. So Usually it depends on Client request or generally we got first 6 modes (because we know 6 Dof 3 translate 3 rotary at a particular node). 2)Methods I.Tracking Method. II.Transormation Method. III.Lanczos Method But in Industry we always go for 3rd method. Refer 3rd method (Lanczos) in detail always good and stable. Also apply proper boundary conditon to extract eigen values, because it also depends on u r Bc's Alex