How would I create a stress curve using this given data: Time(s),Extension(mm),Load(N,Tensile strain (Extension)(mm/mm),Tensile extension(mm)
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$\begingroup$ What kind of stress curve? I assume you mean stress-strain; but you could graph a few things here. It's basically just plotting numbers in a graph though, there isn't much engineering required here. $\endgroup$– JMacCommented Jul 23, 2018 at 16:08
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to calculate the stress, you divide load by the surface area of your section be it a wire or rod or square bar.
Remember $$\sigma = \frac{F}{Area} $$
But if you want to graph a stress/strain curve, you divide all the strains to initial length of your sample. you get numbers starting at 1 and increasing to say 1.0, 1.03 corresponding to increasing loads. You drop the 1 and plot the decimal parts on x axis and stresses on the y axis.
Edit Explaining why i did not consider the change in surface area of the wire or bar. Usually we ignored narrowing of the specimen before we reached plastic region in our lab. And bottle necking happens just before the rapture. You can estimate 30% of tensile strain but it doesn't add up to a significant amount. Say you have 6% tensile strain , you get 0.018 radial shrinking which raised to the power of two is 0.0036 which is smaller than tolerance of many of the jacks you use to test the tensile strain.
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1$\begingroup$ But there are different definitions for stress. For example the area can be taken as constant, namely the area before any force is applied, or the true area which will shrink as the sample stretches. $\endgroup$ Commented Jul 23, 2018 at 17:41
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$\begingroup$ @fibonatic true but usually you dont know the new area $\endgroup$– joojaaCommented Jul 23, 2018 at 19:49