cannot solve for unknown variable

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Md Shariful Islam
Md Shariful Islam 2022-7-19
评论： Md Shariful Islam 2022-7-19
I am trying to solve for unknown variable P in the following code. I determined value of P= 2.945e-5 manually. However, I am not getting that value with the code. As a matter of fact, if I change the constant (1.9664e+08) in the sigma equation, the result is not changing.
Can anyone help in this?
%Constants
L= 300e-6;
O= 5e-6;
theta= atan(2*O/L);
E= 188e9;
w= 1.57e-6;
h= 2.5e-6;
I= (h*w^3)/12;
L_0 = (L/2)*(tan(theta))^2;
%Calculations
syms P real
k= sqrt(P/(E*I));
G= tan((k*L)/4);
L_p= ((tan(theta))^2/(4*k))*( 2*G + k*L + k*L*G^2 + sin(k*L) - 2*G*cos(k*L) - G^2*sin(k*L));
delta_L = L_p - L_0;
sigma = (E/L)*(delta_L + ((P*L)/(E*w*h))) -1.9664e+08==0;
F = vpasolve(sigma, P)

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采纳的回答

Walter Roberson
Walter Roberson 2022-7-19
vpasolve(sigma, [0 .5e-4])
There is a discontinuity before 1e-4 so if you do not confine the search range the discontinuity can cause search failures
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显示 1更早的评论
Walter Roberson
Walter Roberson 2022-7-19
fplot(lhs(sigma), [0 1e-4])
Notice how the plot goes up to about 1e11 in the middle

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