# In a typical tension test a dog bone shaped specimen

In a typical tension test a dog bone shaped specimen is pulled in a machine. During the test, the force F needed to pull the specimen and the length L of a gauge section are measured. This data is used for plotting a stress-strain diagram of the material. Two definitions, engineering and true, exist for stress and strain. The engineering stress Ïƒe and strain Îµe are defined by

Ïƒe = F/A0 and Îµe = L €“ Lo/L0, where L0 and A0 are the initial gauge length and the initial cross-sectional area of the specimen, respectively. The true stress Ïƒt and strain Îµt are defined by Ïƒt = F/A0 L/L0 and Îµt = ln L/L0.
The following are measurements of force and gauge length from a tension test with an aluminum specimen. The specimen has a round cross section with radius 6.4 mm (before the test). The initial gauge length is L0 = 25 mm. Use the data to calculate and generate the engineering and true stress-strain curves, both on the same plot. Label the axes and use a legend to identify the curves. Units: When the force is measured in newtons (N) and the area is calculated in m2, the unit of the stress is pascals (Pa).

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