频率扫描求解固有频率出问题了，请师兄帮帮忙

lyh_lover

这是我编写的程序，原理就是利用Ax=0，x不全为0则A行列式必然为零的方法求固有频率，我就是假设固有频率带进行列式里看行列式是否为0，可很多都为0，弄得我不知道哪个才是真的。。。。，请师兄们帮忙解决下，谢谢了
>> for w=0:1:500
E=21e6;
rou=2340;
b=0.0485;
b1=0.005;
h=0.00182;
L1=0.5;
L2=0.2;
L3=0.2;
h1=0.00202;
h2=0.00252;
h3=0.00322;
A=b*h;
A2=2*h*(b-2*b1)+2*b1*(2*h+h2);
y=(2*h+h2)/2;
I1=b*h^3/12;
I2=b*(2*h+h2)^3/12-(b-2*b1)*h2^3/12;
I3=I1;
r1=((rou*A*w^2)/(E*I1))^0.25;
r2=((rou*A2*w^2)/(E*I2))^0.25;
r3=r1;
k=w*sqrt(rou/E);

d11=-sinh(r1*L1)+sin(r1*L1);
d21=-cosh(r1*L1)*r1+cos(r1*L1)*r1;
d31=-2*A*k*y^2*cosh(r1*L1)*cot(k*L1)*r1-2*sinh(r1*L1)*I1*r1^2+2*A*k*y^2*cos(r1*L1)*cot(k*L1)*r1-2*sin(r1*L1)*I1*r1^2;
d41=-2*cosh(r1*L1)*I1*r1^3-2*cos(r1*L1)*I1*r1^3;

d12=-cosh(r1*L1)+cos(r1*L1);
d22=-sinh(r1*L1)*r1-sin(r1*L1)*r1;
d32=-2*A*k*y^2*sin(r1*L1)*cot(k*L1)*r1-2*A*k*y^2*sinh(r1*L1)*cot(k*L1)*r1-2*cos(r1*L1)*I1*r1^2-2*cosh(r1*L1)*I1*r1^2;
d42=-2*sinh(r1*L1)*I1*r1^3-2*sin(r1*L1)*I1*r1^3;

d13=-sin(r2*L1);
d23=-cos(r2*L1)*r2;
d33=sin(r2*L1)*I2*r2^2;
d43=cos(r2*L1)*I2*r2^3;
d53=sin(r2*(L1+L2));
d63=cos(r2*(L1+L2))*r2;
d73=sin(r2*(L1+L2))*I2*r2^2;
d83=cos(r2*(L1+L2))*I2*r2^3;

d14=-cos(r2*L1);
d24=sin(r2*L1)*r2;
d34=cos(r2*L1)*I2*r2^2;
d44=-sin(r2*L1)*I2*r2^3;
d54=cos(r2*(L1+L2));
d64=-sin(r2*(L1+L2))*r2;
d74=cos(r2*(L1+L2))*I2*r2^2;
d84=-sin(r2*(L1+L2))*I2*r2^3;

d15=-sinh(r2*L1);
d25=-cosh(r2*L1)*r2;
d35=-sinh(r2*L1)*I2*r2^2;
d45=-cosh(r2*L1)*I2*r2^3;
d55=sinh(r2*(L1+L2));
d65=cosh(r2*(L1+L2))*r2;
d75=-sinh(r2*(L1+L2))*I2*r2^2;
d85=-cosh(r2*(L1+L2))*I2*r2^3;

d16=-cosh(r2*L1);
d26=-sinh(r2*L1)*r2;
d36=-cosh(r2*L1)*I2*r2^2;
d46=-sinh(r2*L1)*I2*r2^3;
d56=cosh(r2*(L1+L2));
d66=sinh(r2*(L1+L2))*r2;
d76=-cosh(r2*(L1+L2))*I2*r2^2;
d86=-sinh(r2*(L1+L2))*I2*r2^3;

d57=-cos(r3*(L1+L2));
d67=sin(r3*(L1+L2))*r3;
d77=-2*A*k*y^2*sin(r3*(L1+L2))*cot(k*(L1+L2))*r3-2*cos(r3*(L1+L2))*I3*r3^2;
d87=2*sin(r3*(L1+L2))*I3*r3^3;

d58=-cosh(r3*(L1+L2));
d68=sinh(r3*(L1+L2))*r3;
d78=2*A*k*y^2*sinh(r3*(L1+L2))*cot(k*(L1+L2))*r3+2*cosh(r3*(L1+L2))*I3*r3^2;
d88=2*sinh(r3*(L1+L2))*I3*r3^3;


   D=[d11 d12  d13   d14   d15   d16   0     0

      d21 d22  d23   d24   d25   d26   0     0

      d31 d32  d33   d34   d35   d36   0     0

      d41 d42  d43   d44   d45   d46   0     0

      0   0    d53   d54   d55   d56   d57   d58

      0   0    d63   d64   d65   d66   d67   d68

      0   0    d73   d74   d75   d76   d77   d78

      0   0    d83   d84   d85   d86   d87   d88];
F=det(D)
end

ChaChing

感觉LZ说明下原始的问题(如model)或许较容易理解

VibrationMaster

高度怀疑LZ弄错了概念.
行列式是一个标量结果, 矩阵有N*N个元素,这些元素按行列式规则得到一个标量值--这才是行列式.