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.

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%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

Accepted Answer

SYED IMTIAZ ALI SHAH
SYED IMTIAZ ALI SHAH on 10 Aug 2019
syms Th;
km = (2*T)/(Sx-Sy);
eq1 = tan(2*Th) == km;
solvth = solve(eq1);
solvth = double(solvth)
Hope this will work
  4 Comments
SYED IMTIAZ ALI SHAH
SYED IMTIAZ ALI SHAH on 11 Aug 2019
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

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More Answers (1)

Douglas Leaffer
Douglas Leaffer on 5 Apr 2021
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

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