normally we'll do 3 times tensile test to obtain the average value but the rate of elongation is different for the 3 specimens. Eg: Strain value at UTS for the first sample is 0.2mm/mm but second sample is 0.35mm/mm. So how do we standardize the stress-strain curve. Thank you
The simplest and easier way to do this is to add the three values of strains at the same time increment and divide the number by 3. As example, you did three tests (1,2 and 3) each has time from t= 0 to t = 10000 s, at a certain moment you can apply this (\epsilon_1+\epsilon_2+\epsilon_3)/3 = \epsilon_av.
Thank you Ahmed. The time increment is same but the rate of elongation is different. eg: UTS of sample 1 is at 5000s but the UTS of sample 2 is at 6000s and UTS of sample 3 is at 5800s. So, I can only get the average UTS by adding the 3 values of UTS and divided by 3. Then, how can i show the average stress-strain curve?
Thank you.
If you add the the values of the three tests at each increment, you will obtain an average stress strain curve and the maximum strain will be different from the individual value for each specimen. and you will get the whole average stress-strain curve for this material.
This article explains and get the medium curve.
Bergner, F. & Zouhar, G., 2000, “A New Approach to the Correlation Between the Coefficient and the Exponent in the Power Law Equation of Fatigue Crack Growth”. International Journal of Fatigue, pp. 229-239.