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I am trying to calculate the static yield stress of a specimen using the 0.2% offset line on a stress strain curve. I found the static yield stress of the specimen to be the number in bold (104.1239). Given the shape of the graph and how close the static yield stress appears to be to the UTS, I was wondering if this value actually looked correct? Or could I have accidentally calculated the dynamic yield stress instead?

The material I used in this test was a "low grade aluminum"... which is throwing my thought process off.

I would really appreciate any insight on this.

enter image description here

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  • $\begingroup$ Do you know the specific grade of aluminium, that you used? $\endgroup$ – Andrew Mar 19 '18 at 7:35
  • $\begingroup$ 160mm/min is awful fast dont you think? Whats the gage length? In any case you should show the offset line on the plot. $\endgroup$ – agentp Mar 19 '18 at 11:09
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The mechanical properties of an aluminum alloy definitely vary with the various series designations. As I am not totally sure which series you are working with and how you are doing your calculations, I cannot say whether your actual strength values are correct.

However, it is possible that your yield strength and ultimate tensile strength are not very far apart. For example, in aluminum 1100, the difference between yield strength and ultimate tensile strength is only 5 MPa at room temperature. Your alloy may be similar in nature.

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In the old days before computers, we just drew the 0.2 % offset or the 0.5 % strain lines , and where they intersected the stress / strain curve was the yield strength. Of course materials are strain rate sensitive but it does not appear that this data contains such information.

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