Hey there, I am trying to write a code for 2D-Mohr's circle and i need to generate a circle for x value of Sx, radius(r) of T.

%this is the code(incomplete) for 2D Mohrs circle, looking for assistance.
Sx = input('Enter value of stress in x direction in N/mm2:  ');
Sy = input('Enter value of stress in y direction in N/mm2:  ');
T = input('Enter value of shear stress in N/mm2:  ');

%Maximum and Minimum principal stress, Maximum shear stress
S1 = ((Sx+Sy)/2) + sqrt((((Sx-Sy)/2)^2) + (T^2))
S2 = ((Sx+Sy)/2) - sqrt((((Sx-Sy)/2)^2) + (T^2))
Tm = sqrt((((Sx-Sy)/2)^2) + (T^2))

syms Th;

eq1 = tan(2*Th) == ((2*T)/(Sx-Sy));
Th = solve(eq1, Th)
% Im having a problem outputting Th in numeric values 

[darova]

It is math. The question has nothing to do with MATLAB

→

Answer 1

[SYED IMTIAZ ALI SHAH]

syms Th;
km = (2*T)/(Sx-Sy);
eq1 = tan(2*Th) == km;
solvth = solve(eq1);
solvth = double(solvth)

Hope this will work

[Syed Mustaqhim]

Mr. Syed, can you share the code for drawing a mohrs circle with the above mentioned variables (Sx and r)

[SYED IMTIAZ ALI SHAH]

Ok

[SYED IMTIAZ ALI SHAH]

Below is the code, it may not be very efficient (Time constraint) however it will work.

% Center of Mohr Circle
sigma_x = 7;
sigma_y = 5;
sigma_c = (sigma_x+sigma_y)/2;
% Center = (sigma_c,0)
shear_t = 3;
% Radius of Mohr Circle
r = sqrt(((sigma_x-sigma_y)/2)^2+shear_t^2);
twotheta = atan(shear_t/((sigma_x-sigma_y)/2));
theta  = twotheta/2;
theta_2 = 0:1:360;
theta_2 = theta_2.*pi/180;
x = r*cos(theta_2)+sigma_c;
y = r*sin(theta_2);
sigma_1 = max(x);
sigma_2 = min(x);
Sx = [sigma_x shear_t];
Sy = [sigma_y -shear_t];
% all points together
allpoints = [sigma_c 0; sigma_1 0; sigma_2 0; sigma_x shear_t; sigma_y -shear_t];

plot(sigma_1,0,'o','LineWidth',2,'color','k')
hold on
plot(sigma_2,0,'o','LineWidth',2,'color','k')
plot(sigma_c,0,'o','LineWidth',2,'color','k')
plot([Sx(:,1) Sy(:,1)],[Sx(:,2) Sy(:,2)],'LineWidth',2,'color','k')
plot(x,y)
labels = {'C','P Str','P Str','B','A'};
labelpoints(allpoints(:,1), allpoints(:,2),labels,'SE',0.5,1)
grid on
axis equal

[Syed Mustaqhim]

Thanks a lot!

Answer 2

[Douglas Leaffer]

ADD the following function call to your script:

circle((S1+S2)/2, 0, Tm) % function call

Then create a new function and save to the same (current) folder as your script:

function h = circle(x,y,r)

hold on

th = 0:pi/50:2*pi;

xunit = r * cos(th) + x;

yunit = r * sin(th) + y;

h = plot(xunit, yunit);

grid on

hold off

end