@davesrocketshop this probably needs your input, if you have time. I can double-check the values themselves, but evaluating whether the proposed treatment of UltimateStrain is correct gets a little beyond me 😁 .

I'm not sure about UltimateStrain. This isn't saying you're wrong, but I'm not an expert here so need to do some research.

I don't think you can find the UltimateStrain that way. I'm digging deeper, but here is the AI summary:

You cannot calculate the ultimate strain directly from the ultimate tensile strength (UTS); they are two different properties measured at the same point on a stress-strain curve. The ultimate strain is the total strain the material has undergone at the point of UTS, while the UTS is the maximum stress the material can withstand.

• Ultimate Tensile Strength (UTS): This is the maximum stress a material can endure before it starts to neck and weaken. It is represented by the peak of the engineering stress-strain curve.

• Ultimate Strain : This is the total strain experienced by the material when it reaches its ultimate tensile strength. It is the value of the strain at the peak of the stress-strain curve.

To find the ultimate strain, you need to refer to the stress-strain curve generated during a tensile test and identify the strain value that corresponds to the point of maximum stress (UTS). You can either read this value directly from the curve or extract it from the raw data of the test.

Elongation and Area Reduction is related to point of fracture, and I likely have the formula wrong too, so it's best I remove the value for UltimateStrain for these cards.

However, something still seems a little odd, I searched for "ultimate strain at fracture as a force", and it reminded me strain is not a force, but defined it as:

Strain: A dimensionless ratio that measures how much a material deforms when a force is applied. It is calculated as:

• Engineering Strain = (Change in Length) / (Original Length)

and a little further down I read:
Fracture Strain: The strain value at the exact moment the material breaks. It is calculated by dividing the total elongation of the material at fracture by its original length.
So in this case, I could understand elongation of 17% (for Copper-102) to resolve as a dimensionless value of

• Fracture Strain = (17%) / (100%) = 0.17 or maybe (100%+17%)/(100%) = 1.17
  There is no kPa unit value in this result.... so I'm sort of wondering if the units are wrong for UltimateStrain.

I'll go ahead and update the cards by removing UltimateStrain, and then also apply Dave's multistrings and TAGs suggestions - those are good suggestions worth adding.

Question:
These cards only present 295K, but the documents have multiple temperature points for the same copper materials, so it may be useful too add them to the cards too, maybe as 2D or 3D arrays. Do you want me to add them too? or maybe add it in a separate PR to keep the size of this PR from growing too much?

Question:
It would be useful to pull-in other data from C10200 to supplement Copper-102, C12200 to supplement Copper-122{a/b}.....like Poisson's Ratio, densities, etc. Should I append to this PR? or leave this work for a separate PR to avoid growing this PR too large?

If you have the temperature based data, I'd add that here too. No one uses it yet, but that's because it's not been available. Build it and they will come!

I wouldn't worry about the size of the PR. It's still pretty self contained. It's pretty difficult to change a material without affecting projects, so it's better to be complete and correct.

As for strain, I believe you may be right about dimensions. I blindly copied what was in the previous material cards which probably wasn't the best idea. Checking in other materials, various Aluminum and Steel materials have values, all dimensionless. While you're in there it might be a good idea to remove the units from the LinearElastic.yml file to avoid future confusion.

One final note: your materials don't include the source of your information. This is useful for validating data in the future. Please add appropriate "SourceURL" and "ReferenceSource" values, especially since you have that information available. For an example see: https://github.com/davesrocketshop/Woods/blob/master/Resources/Materials/African%20Blackwood.FCMat

I know I'm being picky here, but it's better to include these things for materials included in the core. It's different if you're just using them in your own projects.

Main source of information came from:
References for Copper-102...955
copper.org 144/8R
There is a similar document located on the Nickel institute, but it's named as cda144-8-mechanical-low-temperature.pdf

details and history concerning IACS% with 100% applying to Cu~99.95%
Interesting details about IACS 100%, values are typically reported at 20°C.
Details about Magnetic Permeability

Pure copper Poisson's ratio of 0.344 and Bulk Modulus of 137 GPa for 300°K
Poissins-Ratio.gif see this page

Somewhat generic/general info

Specific Heat multiplier = 4186.8
Thermal Conductivity multiplier = 1.73
Cooefficient of Expansion used = 9/5*1000000
Conductivity used = 58
Magnetics used = 1.32 / 1.26e-6 =1050119

Will look at adding Ultimate Strain next...

It took a bit of digging, but this makes sense.

I don't think you can find the UltimateStrain that way. I'm digging deeper, but here is the AI summary:

You cannot calculate the ultimate strain directly from the ultimate tensile strength (UTS); they are two different properties measured at the same point on a stress-strain curve. The ultimate strain is the total strain the material has undergone at the point of UTS, while the UTS is the maximum stress the material can withstand.

* Ultimate Tensile Strength (UTS): This is the maximum stress a material can endure before it starts to neck and weaken. It is represented by the peak of the engineering stress-strain curve.

* Ultimate Strain : This is the total strain experienced by the material when it reaches its ultimate tensile strength. It is the value of the strain at the peak of the stress-strain curve.

To find the ultimate strain, you need to refer to the stress-strain curve generated during a tensile test and identify the strain value that corresponds to the point of maximum stress (UTS). You can either read this value directly from the curve or extract it from the raw data of the test.

I went to the root directory and ran grep "ltimateStress" -R * and found many lines with UltimateStrain but also found 3 lines with ultimateStrain too.

• Many of the lines were for *.FCMat card files, but taking a look at a few random files like AlZn4 or a few more Steels, I was finding 'Elongation' values entered into the 'UltimateStrain' (I'm guesing that Elongation was confused with UltimateStrain, or maybe it's a case of.... if you have this value available, but you have this UltimateStain field which is sort of close, so let's put it there because it's sort of close).
• Then there were the 3 grep lines with ultimateStrain, this one is a little confusing + ultimateStrain.length() + ultimateTensileStrength.length() + yieldStrength.length() which appears to be mixing Strain and Stength.

Then, there is a csv file too, src/Mod/BIM/Presets/pset_definitions.csv. This one is interesting, because there is UltimateStrain and UltimateStress. Following this clue further, if you go into git history, this csv file was in directory ARCH, and eventually in directory BIM, so I'm guessing these two values originated in FreeCAD architecture.

Okay, going back to google, and searching for Ultimate Strain AND Architecture brought back info more in line with what you described. I found this particularly interesting, especially figure 2, and further-on more about fatigue - interesting pdf.

...anyhow, in summary, looking at the aluminum and steel cards, it may be worth adding fields for 'Elongation' and also 'Reduction of area'. Understandable, there might not be any current use for these at the moment, but it will help users plug Elongation values into Elongation, and not UltimateStrain - basically, there are going to be several *.FCMat cards that need reviewing for UltimateStrain.

These may also shed some more light, since ultimatestress is visible here, but I did not follow-up on these.

grep "ltimatestrain" -R *
grep "ltimatestress" -R *

QUESTION:
'Elongation' and 'Reduction of area', leave them for another PR, other?

Getting back to Ultimate Strain....

This is going a little slower than I expected. I noticed the graphs aren't linear. This non-linearity can be expected when pulling paper through some photocopiers or scanners back in the 70s, 80s, 90s (For example: a company I had worked at in the past, had to put warnings on their punchout sheets telling end users not to rely entirely on a photocopied images of punchouts as they might not be 'correct' when they eventually punched-out holes and found small non-conformities). To reduce the non-linearity, I started finding points per grid instead of per page, so instead of Copper-102 using bottom left=127,794 and top right=1044,27, I started using the grids like 40-50kpsi stress and 0-0.05in/in strain.

At the moment, here are the first 3...

All these points above are based on the Tensile Strength shown in Table 2, for example, Copper 102, 295°K, Tensile Strength is 48,400psi, which, interestingly, is not the peak of the curve (closer to 48,900kpsi), this might be due to +/-tolerances, but then again, if you look at the fracture point for 295°K, there is a big difference, where the elongation=17% on table2, versus the curve's=18.5%

QUESTION:
Should I include (calculated) Modulus of Resilience or (calculated) Material Toughness?

Copper-102 (Cold drawn 60%)

QUESTION: Include (estimated from curve) YieldStrain?

Sanity check:
copper_ult1.csv

Fast-tracked values remaining UltimateStrains for 295°K - Currently going through other temps so they can be shown here when done.

Remember that this will be in v1.2. You have lots of time to make it as complete as you see fit.

Thanks, this project has a pretty fast tempo, so I was expecting it to flip pretty soon (I was using v0.8 back in Feb, and (package) v1.02 now).

Something broke along the way.
I managed to remove the last 2, then add new one here:
https://github.com/JoesCat/FreeCAD/commits/Cu/
..but...
it didn't appear to propagate correctly on your end.... (I still see mention of linkedlist patch).

...anyhow.... appears I still needed to fill in holes, otherwise FreeCAD would Bork.
...and Poisson, UltimateStrain, YieldStrain, Elongation, ReductionOfArea aren't visible (I guess it seems not to like floats yet).

I only entered Copper-102 at this point, in case this is not the expected direction and other edits required to go in another direction.

Also wasn't sure what to call these new temperature arrays, so I basically used similar descriptions as the top of Table2 in the pdf.

I think the arrays are still the solution for you. A missing feature that will be added in 1.2 is interpolation. The temperatures don't need to be at fixed intervals

I suspect, libspiro might be able to help with interpolation (thinking curve-fitting), unless you already have some other curve-fitting solution available..

I think the arrays are still the solution for you. A missing feature that will be added in 1.2 is interpolation. The temperatures don't need to be at fixed intervals

I suspect, libspiro might be able to help with interpolation (thinking curve-fitting), unless you already have some other curve-fitting solution available..

I have a "mostly" implemented solution already. Just need to finish it. It got lost in my tiff with the CWG

Young's Modulus

Multiplier = YYY Mpsi x 6.89476 = ZZZ GPa

Shear Modulus

Multiplier = YYY Mpsi x 6.89476 = ZZZ GPa

ym_sm.ods Sanity Check for Young's and Shear Modulus.
NOTE: Libre-office ods file, since prior CSV only returned values instead of formulas (This shows the math).

Other misc...

• C95500, added Compressive=60ksi
• all alloys, min/max alloys, C64700 Si=0.4-0.8%

Is this PR ready?

Including this here, however, did not think it was accurate enough to include in the Copper Cards as I didn't take enough slices to follow the curves accurately (so you won't see these in the cards). Question: Add these in too?

Modulus of Resilience (Ur)

Material Toughness

Ultimate Strain

Yield Strain

Fracture Strength

Multiplier = YYY kpsi x 6.89476 = ZZZ MPa

More Misc...

• Copper-510 typically ≈0.34, H04 tempered ≈0.341, Annealed ≈0.33
• Copper-647, first page mentions Alloys≈2.5% by WT, so...2.5-1.97-0.01≈0.52
• Density and magnetic susceptibility=-1.04e-9

...continuation...

All these points above are based on the Tensile Strength shown in Table 2, for example, Copper 102, 295°K, Tensile Strength is 48,400psi, which, interestingly, is not the peak of the curve (closer to 48,900kpsi), this might be due to +/-tolerances, but then again, if you look at the fracture point for 295°K, there is a big difference, where the elongation=17% on table2, versus the curve's=18.5%

Sanity Check:
copper_ult1.ods
What is all the numbers...

Done.

@davesrocketshop @FreeCAD/cad-working-group is this good to be merged?

@davesrocketshop @FreeCAD/cad-working-group is this good to be merged?

There's a lot here. Let me review again. I'll get back to you later today

OK with the change. Can’t judge on the values though but the more we have the better it is.

@davesrocketshop good to go?

Thumbs up