Help with a Matrix for different angles

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Eddy Ramirez 2021-3-28

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https://ww2.mathworks.cn/matlabcentral/answers/786156-help-with-a-matrix-for-different-angles

评论： Walter Roberson 2021-3-31

Greetings,

I am running the following code and I want to find out the value of sigma1, sigma2, and tau6 at each angle starting from 0. I was thinking of doing a for-lopp, but the problem is that I am not able to do negative thetas or 0.

I think the problem is that MatLAb is taking ALL the angles and creating one big solution based on all angles? i might be wrong here, but any help to achieve my goal would be greatly appreciated

theta=0:5:90;
m=cosd(theta);
n=sind(theta);
sigma1=sym('sigma_1');
sigma2=sym('sigma_2');
tau6=sym('tau_6');
stress=[sigma1; sigma2; tau6];
sigmax=0;
sigmay=0;
tau5=sym('taus');
stress_rotation=[sigmax; sigmay; tau5];
T=[m.^2  n.^2   2.*m.*n; 
   n.^2  m.^2  -2.*m.*n;
   -m.*n m.*n  m.^2-n.^2];
equation=stress==T.*stress_rotation;
solution=solve(equation, stress);
sigma1_f=vpa(solution.sigma_1);
sigma2_f=vpa(solution.sigma_2); 
tau6_f=vpa(solution.tau_6);

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Eddy Ramirez 2021-3-31

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yeah still no luck, i might have to recode it i just find it weird that a for loop doesnt do the trick. I wrote it as shown below but it does not work at all

theta=0:5:90;
m=cosd(theta);
n=sind(theta);
m2=m.^2;
n2=n.^2;
for i=1:length(theta)
    T=[m2(i)  n2(i)   2.*m(i).*n(i); 
       n2(i)  m2(i)  -2.*m(i).*n(i);
      -m(i)*n(i) m(i)*n(i)  m2(i)-n2(i)];
    
    sigma1=sym('sigma_1');
    sigma2=sym('sigma_2');
    tau6=sym('tau_6');
    stress=[sigma1; sigma2; tau6];
    sigmax=0;
    sigmay=0;
    tau5=sym('taus');
    stress_rotation=[sigmax; sigmay; tau5];
    
    equation=stress(i)==T.*stress_rotation(i);
    solution=solve(equation, stress);
    sigma1_f=vpa(solution.sigma_1);
    sigma2_f=vpa(solution.sigma_2); 
    tau6_f=vpa(solution.tau_6);
   
end