0.2% proof stress - youngs modulus Last Post 21 Apr 2012 09:46 AM by Niel. 1 Replies.
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jduk28

New Member
Posts:2

 19 Apr 2012 09:42 AM for a uni question i need to draw a stress - strain graph. i worked out the stress and strain and drew the graph, then i was asked to find the 0.2% proof stress. the scale of my strain at the bottom of the graph went from 0 - 0.02 so i couldnt find the 0.2%. after trawling the internet for hours i have found that some people say 0.02 expressed as a percentage is 0.2, which i understand but then how do i label the graph? do i lable the x axis "strain" with the scale 0 - 0.02 or %strain with the scale 0 - 2. if the second option is right then at what stage do i times the strain by 100 to make it a percent? before or after i find the youngs modulus? (stress/strain)
Niel

Basic Member
Posts:193

 21 Apr 2012 09:46 AM Does your stress / strain curve look something like this http://en.wikipedia.org/wiki/File:Stress_v_strain_Aluminum_2.png If so go to Wikipedia and review what is said about ductile materials http://en.wikipedia.org/wiki/Ultimate_tensile_strength#Ductile_materials The 0.2% point is the variation from the linear portion of the stress strain curve and is used to determine the yield point for ductile materials. Niel Leon Engineering.com