modal_analysis.m

结构力学中的有限元例子,包含了7个分类文件夹

function [E_Vec_ok, wn] = modal_analysis ( obj , L, in_data)

% modal analysis for FEM model (system should have at least 2 modes)
% --------------------------------------------------------------------
% INPUT:
%        in_data: - input data structure: ND, EL, etc.
%        obj      - data about the the analyzed object: K, M
%        L        - constrains location vector
% OUTPUT:
%        E_Vec_ok - eigen-vectors 
%        wn       - natural freq vector
% --------------------------------------------------------------------
% uses: 'freq_damp.m', 'eigFEM.m'

   dofs = size(obj.M(L,L),1);
   [G_fact, E_Vec, eig_Values] = ...
      eigFEM (obj.Ksys.Kgl(L,L), obj.M(L,L), (ones(dofs,1).*in_data.dynam.DAMP_C(1))'); % E_Vec(i,mode#) 
   N=2; % damp_ is attributed only to N-th mode 
   bet = (2*in_data.dynam.DAMP_C(1)*eig_Values(dofs-(N-1))-2*in_data.dynam.DAMP_C(1)*eig_Values(dofs))/...
      (eig_Values(dofs-(N-1))^2-eig_Values(dofs)^2);
   alp = 2*in_data.dynam.DAMP_C(1)*eig_Values(dofs-(N-1)) - ...
      bet*eig_Values(dofs-(N-1))^2;

   [wn,damp] = freq_damp_FEM(obj.Ksys.Kgl(L,L),obj.M(L,L),alp,bet); 

   k=1;
   sd = size(E_Vec);
   E_Vec_ok = zeros(length(obj.M),sd(1));
   E_Vec_ok(L,:)=E_Vec;