The elastic portion of the stress–strain diagram for an aluminum alloy is shown in the figure - 3-27

3–27. The elastic portion of the stress–strain diagram for an aluminum alloy is shown in the figure. The specimen from which it was obtained had an original diameter of 12.7 mm and a gage length of 50.8 mm. When the applied load on the specimen is 50 kN, the diameter is 12.67494 mm. Determine Poisson’s ratio for the material.

All problems from Mechanics of Materials Eleventh Edition by Russell C. Hibbeler.