55 lines
2.0 KiB
Matlab
55 lines
2.0 KiB
Matlab
function[K]=StiffnessMatrix(material,mesh,quadrature,ShapeOption)
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K=zeros(mesh.nn*3);
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D_f=material.E/(1-material.v^2).*[1 material.v 0
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material.v 1 0
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0 0 (1-material.v)/2];%bending
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D_t=[material.G 0
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0 material.G];%shear
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alpha=5/6;% shear stress non-uniform modification factor
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beta=material.t^3/12; %integral(z^2,-t/2,t/2)
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if strcmp(ShapeOption,'Q4')
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shape_order=4;
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elseif strcmp(ShapeOption,'Q8')
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shape_order=8;
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elseif strcmp(ShapeOption,'Q9')
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shape_order=9;
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end
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for iel=1:mesh.ne
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KElem=zeros(shape_order*3);
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for ig=1:size(quadrature.points,1)
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shapeFunction=ShapeFunction(quadrature.points(ig,1),quadrature.points(ig,2),ShapeOption);%型函数在积分点处的值
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elemCoordinates=[mesh.Nid(mesh.Eid(iel,2:end),2), mesh.Nid(mesh.Eid(iel,2:end),3)];%四个节点的坐标
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jacobian=Jacobian(shapeFunction,elemCoordinates);%2*2矩阵
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Nd=jacobian.globalDerivatives;%型函数的物理坐标导数
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B_f=zeros(3,shape_order*3);%bending
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B_t=zeros(2,shape_order*3);%shear
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for ib=1:shape_order
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temp=[0 Nd(ib,1) 0 %
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0 0 Nd(ib,2)
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0 Nd(ib,2) Nd(ib,1)];
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B_f(:,ib*3-2:ib*3)=temp;%bending
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temp=[Nd(ib,1) shapeFunction.fun(ib) 0 %[Nd(ib,1) -shapeFunction.fun(ib) 0 参考徐斌的mindlin板元章节
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Nd(ib,2) 0 shapeFunction.fun(ib)]; %注意考虑剪切变形时候，这里的shapeFuncion.fun是否应该有负号
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B_t(:,ib*3-2:ib*3)=temp; %shear
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end
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KElem=KElem+quadrature.weights(ig)*(beta*B_f'*D_f*B_f+alpha*material.t*B_t'*D_t*B_t)*det(jacobian.matrix);%
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end
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ntot=mesh.Eid(iel,2:end)*3-2;%index of DOF
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%assemble to golobal stiffness matrix
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for j=1:numel(ntot)
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for k=1:numel(ntot)
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K(ntot(j):ntot(j)+2,ntot(k):ntot(k)+2) = K(ntot(j):ntot(j)+2,ntot(k):ntot(k)+2) + KElem(j*3-2:j*3,k*3-2:k*3);
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end
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end
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end
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return |