I have this real graphic from a tensile test

[Queren Suriano]

Homework Statement

How can I calculate the ultimate stress? (I refere to the stress that it's in the green rectangle). I have a real graphic, I have two deformations, (it was 2 test, from the same material) and only one stress. The orange curve is Stress versus unit deformation 1, and the gray one is stress vs. deformation 2 . The blue one is the average between the deformation 1 and 2 vs Stress. The REAL graphic from I want calculate this, it's in the last part of the post

Homework Equations

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The Attempt at a Solution

I know that fracture stress is in the red rectangle. I know that the graphic in the last part of the curves, it's illogic (because the deformation "decrease") but the stress is ok, because is the real fracture stress

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[paisiello2]

I don't think the red rectangles are the fracture stresses. When the specimens failed the testing machine probably rebounded and since the machine is most likely calibrated using a strain gauge it gave you some negative displacement values. Not sure why an increased load was measured but I would be attempted to ignore these values.

Also the blue curve does not look like the average of the two curves to me.

 

[Queren Suriano]

Thank you for your opinion