4130 stress-strain curves
4130 stress-strain curves
(OP)
In the Atlas of Stress-Strain Curves, 2nd ed, in chart AS.005 (https://books.google.com/books?id=up5KS9fd_pkC&...) they present 3 charts of tensile stress-strain curves up to yield for 4130 at room and elevated temps for three different heat treatments. Now, first of all, the labeling of the charts is a bit odd - they refer to the "Left", "Center", and "Right" charts, but they're arranged on two rows and labeled like this:
(a) (b)
..(c)..
Based on the nominal strengths listed in the caption - Left is 150 ksi, Center is 180 ksi, and Right is 200 ksi - I'm pretty sure that the order is
(150) (200)
...(180)...
So that's one thing. The other thing is, check out the modulus on chart (c). The RT curve crosses right at .004 strain, 100 ksi, for a modulus of 25 Msi, when I'm expecting something closer to 29-30. If you check charts (a) and (b), they go through .004 strain, 120 ksi, for a modulus of 30 Msi, just as expected. So I think chart (c) is in error.
The caption references WADC TR 56-340, as published in Aerospace Structural Materials Handbook, Vol 1, Code 1201. Unfortunately, I've been unable to find either of these. Does anybody have a copy?
(a) (b)
..(c)..
Based on the nominal strengths listed in the caption - Left is 150 ksi, Center is 180 ksi, and Right is 200 ksi - I'm pretty sure that the order is
(150) (200)
...(180)...
So that's one thing. The other thing is, check out the modulus on chart (c). The RT curve crosses right at .004 strain, 100 ksi, for a modulus of 25 Msi, when I'm expecting something closer to 29-30. If you check charts (a) and (b), they go through .004 strain, 120 ksi, for a modulus of 30 Msi, just as expected. So I think chart (c) is in error.
The caption references WADC TR 56-340, as published in Aerospace Structural Materials Handbook, Vol 1, Code 1201. Unfortunately, I've been unable to find either of these. Does anybody have a copy?





RE: 4130 stress-strain curves
You are correct on the order.
You can't take an accurate modulus off of a typical tensile test curve, and these have been 'smoothed' on top of that.
25Msi is plenty close for this work, after all the properties for a different heat of steel will be different from these anyway.
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P.E. Metallurgy, Plymouth Tube
RE: 4130 stress-strain curves
RE: 4130 stress-strain curves
These also look like 'artists conceptions' and not exact test curves.
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P.E. Metallurgy, Plymouth Tube
RE: 4130 stress-strain curves
My concern isn't pulling a modulus off of the chart. It's that, if the indicated modulus is so far off from what it should be, the whole chart is wrong, probably scaled incorrectly in one or both axes. Which is a problem if I want to calculate area under the curve, or ... do anything with it, really.
RE: 4130 stress-strain curves
I wouldn't even try to compare them to each other in absolute terms, unless you can find the raw data.
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P.E. Metallurgy, Plymouth Tube
RE: 4130 stress-strain curves
1. based on true SS, not on an engineering SS.
2. focus on the linear portion of the curve. 100-120ksi points OP used are off elastic deformation. if using .002 strain, you will get a bit higher E.
Anyway that is not a good method to get an accurate E, but may be good enough for an educational purpose.
RE: 4130 stress-strain curves
When we have to report a modulus we will load the sample to and estimated 50% or yield, then unload to about 10%, and then re-load slowly. This will get you a good section of load curve to calculate from.
We do calculate it for every lab test, and if it is within 25-32Msi we are ok. If it comes out higher or lower we redo the tensile test because it will throw the yield calculation off by too much.
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P.E. Metallurgy, Plymouth Tube