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48 lines
1.5 KiB
48 lines
1.5 KiB
4 years ago
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%--------------------------
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% @Author: Jingqiao Hu
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% @Date: 2020-12-16 14:45:35
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% @LastEditTime: 2021-01-10 15:11:37
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%--------------------------
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function K = update_stiffness(dNh, edofMat_mi, edofMat_ma, n, global_u, global_l, dx, iK, jK)
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eleNum_mi = size(edofMat_mi, 1);
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eleNum_ma = size(edofMat_ma, 1);
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I = eye(eleNum_mi);
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jac = dx^2/4;
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sK = zeros(size(edofMat_ma,2)^2, eleNum_ma);
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tmp_edof = edofMat_mi';
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for ele_ma = 1:eleNum_ma
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u = global_u{ele_ma}(:);
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l = global_l{ele_ma}(:);
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ne = n{ele_ma}; % [2v, 2n]
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n1 = ne(:, tmp_edof(:))'; % [8m, 2v]
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ke = 0;
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for gp = 1:4
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dNh_g = dNh{gp}; % [4, 8]
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dNh1 = kron(I, dNh_g); % [4m, 8m]
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dNH = dNh1 * n1; % [4m, 2v]
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% reshape dNH to [4,2v,m]
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dN1 = reshape(dNH, 4,eleNum_mi,[]); % [4,m,2v]
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dN = permute(dN1, [1,3,2]); % [4,2v,m]
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dP1 = dPdF_fast_linear(u, l, dN); % 4 * l * m
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dPT = permute(dP1, [2,1,3]); % l * 4 * m
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dP2 = reshape(dPT, [], 4*eleNum_mi); % l * 4m
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dF1 = permute(dN, [2,1,3]); % l * 4 * m
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dF1 = dF1(:, [1,3,2,4], :); % NOTE:
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dF2 = reshape(dF1, [], 4*eleNum_mi)'; % 4m * l
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ke_g = dP2 * dF2; % lenout * lenout
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ke = ke + ke_g * jac;
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end
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sK(:, ele_ma) = ke(:);
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end
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K = sparse(iK, jK, sK);
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K = (K + K')/2;
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end
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