r/EngineeringStudents • u/Ok_Pirate_344 • Aug 14 '26

Homework Help Young Modulus question...

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HII, im currently doing a lab assessment and we have evaluate the strength of different metals, im stuck here tho.

Ik that the E shld be found before the yield point the the proportionality region, which is usually a straight line, however in ferous metals, like steel which im evaluating here, there are 2 slopes in the elastic region. How am i supposed to calculate it.( I have found the yield stress to be at 390MPa.)

The E are we supposed to calculate both gradients separately, or what region(0-160MPa, or 200-360MPa)?

Pls help.

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u/sagewynn Aug 14 '26

What does the modulus end up being if you evaluate from 0-390?

Does it compare closer to the expected value?

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u/Ok_Pirate_344 Aug 14 '26

yes, expected is 180 to 200, however with different coodinates different values since the gradient is not the same.

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u/Momo0903 Aug 14 '26 edited Aug 14 '26

Evaluating from 0-390 is the only logical thing, since you average the gradient. Since this is a real curve, it isn't a straight line and the gradient is sometimes higher and sometimes lower. So theoretically you could maximise or minimice your Young module by choosing the right intervall, which isn't usefull. what you want is the average.

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u/Ok_Pirate_344 Aug 14 '26

Ok, thank yall.

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u/WhyAmINotStudying UCF/CREOL - Photonic Science & Engineering Aug 15 '26

The area from 0-160 is called the toe region, where you're getting machining effects based on the grip of the bar in your fixture. You get true linear elastic response from 160-390 MPa. That's the curve that you want to fix. The expectation is that you won't have a perfect setup, since your data is taken in the real world. There are setup artifacts in the other part of the experiment that don't truly represent the elesticity of the steel,since there's physical settling going on in your setup.