FINAL INDEPENDENT PROJECT

Aim of the project is to find the tensile stress,strain of steel rod.

Actually why i have took this project is at present im working automobile and areospace manufacturing industry here we are manufacture the matreials in aluminium,brass, Ms, steel components. we are buying the raw materials outside supplier for customer required grades. For that materials we used to produce the RM test certificates for the customers for the clarification of hardness and combination of materials.while we are sending the reports we used creat the ppt and charts according to the RM test cerificates. this is the thing which made me to choose this project.

I took some values on my own for the data for strees strain 7009 T6 Aluminium materials.

Here in this projects i have done two different codings for one is stress stain for the steel and another one is splitwise method means for four different values in same graph to identify i have choosen different color for each data.

One more thing here i have choose apps in the matlab curve fit to know the goodness of fit R Square . instead of using the formulas in codings

codings

%function codings for stress and predicted stress

function [f]=fitness_characteristics(stress,predictedstress)
M=mean(stress);
ssr=0;
sse=0;
for i=1:length(stress)
sse=sse+(stress(i)-predictedstress(i))^2;
end
for i=1:length(stress)
ssr=ssr+(M-predictedstress(i))^2;
end
sst=sse+ssr;
Rsquare=ssr/sst
rmse=(sse/length(stress))^0.5
if (Rsuare>0.90)
disp('the fit is good bcz Rsquare>0.90')
else disp('the fit is not good bcz Rsquare<=0.90')
end

Main codings for curve fit and Quartic curve fit

clear all
close all
clc

%reading the files
stressdata=load('strain stress 7009 T6 Aluminium');
strain=stressdata(:,1);
stress=stressdata(:,2);
%curve fittings for cubic
coeff=polyfit(strain,stress,3);
predictedstress=polyval(coeff,strain);

%compare the cubic curve fit
figure(1)
plot(strain,stress,'linewidth',2,'color','r')
hold on
plot(strain,predictedstress,'linewidth',2,'color','b')
xlabel('strain')
ylabel('stress')
legend('original dataset','curvefit')
title('curve fit for a cubic polynomial')
hold off

%checking error
disp('cubic curve fit, we have found :')
%fitness_characteristics(stress,predictedstress)
%curve fitting for a quartic polynomial
coeff=polyfit(strain,stress,3);
predictedstress=polyval(coeff,strain);

%compare my curve fit
figure(2)
plot(strain,stress,'linewidth',2,'color','g')
hold on
plot(strain,predictedstress,'linewidth',2,'color','y')
xlabel('strain1')
ylabel('stress1')
legend('original dataset','curvefit')
title('curve fit for quartic polynomial')
hold off

%checking error
disp('for quartic curve fit, we have found :')
%fitness_characteristics(stress,predictedstress)

%finding the youngs's modulud
ultimate_tensile_strength = max(stress)
youngs_modulus =(495-196)/(0.002-0.0015)
yield_point=330

%Here the codings for the split wise method of curve fit

clear all
close all
clc

%reading the file
stressdata=load('strain stress 7009 T6 Aluminium');
strain=stressdata(:,1);
stress=stressdata(:,2);

%splitting the datas in four parts
strain1=stressdata(1:10,1);
stress1=stressdata(1:10,2);

strain2=stressdata(10:25,1);
stress2=stressdata(10:25,2);

strain3=stressdata(21:40,1);
stress3=stressdata(21:40,2);

strain4=stressdata(31:25,1);
stress4=stressdata(31:25,2);

%curve fitting for a quartic polynomial
num1=polyfit(strain1,stress1,4);
predictedstress1=polyval(num1,strain1);

num2=polyfit(strain2,stress2,4);
predictedstress2=polyval(num2,strain2);

num3=polyfit(strain3,stress3,4);
predictedstress3=polyval(num3,strain3);

num4=polyfit(strain4,stress4,4);
predictedstress4=polyval(num4,strain4);

%compare my quartic curve fit

plot(strain,stress,'linewidth',4,'color','r')
hold on
plot(strain1,predictedstress1,'linewidth',2,'color','b')
plot(strain2,predictedstress2,'linewidth',2,'color','g')
plot(strain3,predictedstress3,'linewidth',2,'color','y')
plot(strain4,predictedstress4,'linewidth',2,'color','g')
xlabel('strain splitwise')
ylabel('stress splitwise')
legend('original dataset','splitwise curvefit')
title('curvefit for splitwise')
hold off

predictedstress(1:10)=predictedstress1;
predictedstress(10:25)=predictedstress2;
predictedstress(21:40)=predictedstress3;
predictedstress(31:25)=predictedstress4;

%checking the errors
disp(' the quartic curve fit, we have found :')

here i have attached the backup documents for the codings ,graph images and goodness of fit reports for the two different codings for your persual.