# Stress-strain graph

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Junway on 9 Feb 2021
Edited: Walter Roberson on 10 Feb 2021 I want to make Stress-Strain with linear regression and 0.2% off set graph.
But My code does not show me normal Stress-Strain graph.
I import excel data to matlab. I want to delete First column (start 76) but i cannot deleted.
I want to linear regression from 0 to 593 row data.
can you help me?
AluminumW(1:75,:) = [];
AluminumW(593:end,:) = [];
disp = AluminumW(:,2);
force = AluminumW(:,3);
disp1 = table2array(disp);
force1 = table2array(force);
shift1 = disp1 - 0.081994;
shift2 = force1 - 0.11194;
d = 2.54;
r = d/2;
A = pi*r^2;
strain = shift1 / 12.7;
stress = shift2 / A;
figure(1)
plot(strain,stress)
xlabel('Engineering Strain')
ylabel('Engineering Stress (GPa)')
grid on
hold on
x = strain(60) - strain(1);
y = stress(60) - stress(1);
b1 = y / x;
slope = b1*strain;
plot(strain,slope,'g')
hold on
yield = strain + 0.002;
plot(yield,slope,'r')
hold off

randerss simil on 9 Feb 2021
Edited: randerss simil on 9 Feb 2021
To delete 1st column
AluminumW(1:75,1) = []; % to delete 1st column
Junway on 10 Feb 2021 How can I output like green line? I used excel file.
Two vertical lines are linear regression (Modules) 0.02 offset.
Steel(1480:end,:) = [];
Steel(1:64,:) = [];
Steel(114,:) = [];
disp = Steel(:,2);
force = Steel(:,3);
disp1 = table2array(disp);
force1 = table2array(force);
shift1 = disp1 + 0.088812;
shift2 = force1 - 0.004290;
d = 2.5;
r = d/2;
A = pi*r^2;
strain = shift1 / 14.8;
stress = shift2 / A;
figure(1)
plot(strain,stress)
xlim([-0.01,0.2])
ylim([0,.5])
xlabel('Engineering Strain')
ylabel('Engineering Stress (GPa)')
title('S v e')
grid on
hold on
x = strain(85) - strain(1);
y = stress(85) - stress(1);
b1 = y / x;
slope = b1*strain;
plot(strain,slope,'g')
hold on
yield = strain + 0.002;
plot(yield,slope,'r')
hold off