Fall 2012 ME 395 - GSI Josh Lacey

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 Uncertainty Calculations

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Posts : 13
Join date : 2012-10-01

PostSubject: Uncertainty Calculations   Tue Oct 02, 2012 4:41 pm

Do we need to calculate the uncertainty for all of the load, stress and strain values that we got from the lab or do we assume that there is no uncertainty in those values?
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GSI Overlord

Posts : 126
Join date : 2012-08-30

PostSubject: Re: Uncertainty Calculations   Tue Oct 02, 2012 7:10 pm

There is ALWAYS uncertainty when you take experimental measurements.

You will definitely want to report your elastic modulus, yield strength, and ultimate tensile strength with an uncertainty (the tensile strength precision uncertainty will come from using the other lab sections' data).

As for your stress-strain curves...it's probably just ok to include one set of error bars on the figures that represent the uncertainty of the whole curve (it should be reasonably constant over the entire range of strain). You'll have 3 sources of uncertainty as always...accuracy error comes from the noise in the signal that you might have had to remove via filtering, etc. (this you will probably just have to estimate and likely will be small), resolution error from the analog to digital conversion (same as the resolution error of the Instron in lab 1) and you could quantify precision error using the data from your lab section (the two curves won't be exactly the same).
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Uncertainty Calculations
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Fall 2012 ME 395 - GSI Josh Lacey :: Lab Questions :: Lab 3-
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