clc,clear
E=70*10^9;%弹性模量
de=2700;% 密度
l=0.8;% 长
b=50*10^(-3);% 宽
h=3*10^(-3);% 高
I=b*h^3/12;% 惯性矩
A0=b*h;%横截面积
b11=1.875;
b21=4.694;
b31=7.855;
b41=10.996;
b1=b11/l;
b2=b21/l;
b3=b31/l;
b4=b41/l;
%前4阶固有频率
w1=b1^2*sqrt(E*1/(de*A0));
w2=b2^2*sqrt(E*I/(de*A0));
w3=b3^2*sqrt(E*I/(de*A0));
w4=b4^2*sqrt(E*I/(de*A0));
w=[w1,w2,w3,w4];%角频率(rad)
f=w/2/pi;%频率(Hz)
rl=-(cos(b11)+cosh(b11))/(sin(b11)+sinh(b11));
r2=-(cos(b21)+cosh(b21))/(sin(b21)+sinh(b21));
r3=-(cos(b31)+cosh(b31))/(sin(b31)+sinh(b31));
r4=-(cos(b41)+cosh(b41))/(sin(b41)+sinh(b41));
syms x
Y01=cos(b1*x)-cosh(b1*x)+rl*(sin(b1*x)-sinh(b1*x));
Y02=cos(b2*x)-cosh(b2*x)+r2*(sin(b2*x)-sinh(b2*x));
Y03=cos(b3*x)-cosh(b3*x)+r3*(sin(b3*x)-sinh(b3*x));
Y04=cos(b4*x)-cosh(b4*x)+r4*(sin(b4*x)-sinh(b4*x));
C1=double(sqrt(l/int(de*A0*Y01^2,x,0,l)));
C2=double(sqrt(l/int(de*A0*Y02^2,x,0,l)));
C3=double(sqrt(l/int(de*A0*Y03^2,x,0,l)));
C4=double(sqrt(l/int(de*A0*Y04^2,x,0,l)));
x=0:0.001:l;
Yl=C1*(cos(b1*x)-cosh(b1*x)+rl*(sin(b1*x)-sinh(b1*x)));
Y2=C2*(cos(b2*x)-cosh(b2*x)+r2*(sin(b2*x)-sinh(b2*x)));
Y3=C3*(cos(b3*x)-cosh(b3*x)+r3*(sin(b3*x)-sinh(b3*x)));
Y4=C4*(cos(b4*x)-cosh(b4*x)+r4*(sin(b4*x)-sinh(b4*x)));
hf=figure('units','normalized','position',[0.4 0.4 0.5 0.4]); % [x,y,宽,高]
plot(x,zeros(1,length(x)),'.')
hold on
plot(x,Yl,'-')
plot(x,Y2,'--')
plot(x,Y3,':')
plot(x,Y4,'-.')
legend('参考位置','一阶主振型','二阶主振型','三阶主振型','四阶主振型')
web('http://www.ilovematlab.cn/forum-235-1.html','-browser')