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Author Topic: Proper bronze, steel, bone and obsidian elasticity data  (Read 7100 times)

Putnam

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Proper bronze, steel, bone and obsidian elasticity data
« on: April 06, 2015, 04:52:54 pm »

My material helper has evolved to the point where I can now get better representations of RL metals than Dwarf Fortress actually has. More importantly, it allows me to make bronze have proper values.

Code: [Select]
[IMPACT_YIELD:602000]
[IMPACT_FRACTURE:843500]
[IMPACT_STRAIN_AT_YIELD:899]
[COMPRESSIVE_YIELD:602000]
[COMPRESSIVE_FRACTURE:843500]
[COMPRESSIVE_STRAIN_AT_YIELD:899] 67 GPa
[TENSILE_YIELD:172000]
[TENSILE_FRACTURE:241000]
[TENSILE_STRAIN_AT_YIELD:156] 110 GPa
[TORSION_YIELD:172000]
[TORSION_FRACTURE:241000]
[TORSION_STRAIN_AT_YIELD:384]
[SHEAR_YIELD:172000]
[SHEAR_FRACTURE:241000]
[SHEAR_STRAIN_AT_YIELD:384] 44.8 GPa
[BENDING_YIELD:172000]
[BENDING_FRACTURE:241000]
[BENDING_STRAIN_AT_YIELD:156]

I got this from this page's data on bronze's shear modulus. The bulk modulus was calculated with the equation , where E is the young's modulus and G is the shear modulus (accounting for significant figures, of course).

Steel also has bad data, so here's steel with proper shear modulus value:

Code: [Select]
[IMPACT_YIELD:1505000]
[IMPACT_FRACTURE:2520000]
[IMPACT_STRAIN_AT_YIELD:940]
[COMPRESSIVE_YIELD:1505000]
[COMPRESSIVE_FRACTURE:2520000]
[COMPRESSIVE_STRAIN_AT_YIELD:940] 160
[TENSILE_YIELD:430000]
[TENSILE_FRACTURE:720000]
[TENSILE_STRAIN_AT_YIELD:225] 200
[TORSION_YIELD:430000]
[TORSION_FRACTURE:720000]
[TORSION_STRAIN_AT_YIELD:538]
[SHEAR_YIELD:430000]
[SHEAR_FRACTURE:720000]
[SHEAR_STRAIN_AT_YIELD:538] 80
[BENDING_YIELD:430000]
[BENDING_FRACTURE:720000]
[BENDING_STRAIN_AT_YIELD:215]

Steel already had bulk modulus and young's modulus known in the files, so I could easily get the shear modulus by , where K is bulk modulus and E is young's modulus.

And bone, too!

Code: [Select]
[IMPACT_YIELD:200000]
[IMPACT_FRACTURE:200000]
[IMPACT_STRAIN_AT_YIELD:500]
[COMPRESSIVE_YIELD:200000]
[COMPRESSIVE_FRACTURE:200000]
[COMPRESSIVE_STRAIN_AT_YIELD:500] bulk modulus 40 GPa
[TENSILE_YIELD:115000]
[TENSILE_FRACTURE:130000]
[TENSILE_STRAIN_AT_YIELD:575] young's modulus 20 GPa
[TORSION_YIELD:115000]
[TORSION_FRACTURE:130000]
[TORSION_STRAIN_AT_YIELD:1643]
[SHEAR_YIELD:115000]
[SHEAR_FRACTURE:130000]
[SHEAR_STRAIN_AT_YIELD:1643] shear modulus 7 GPa
[BENDING_YIELD:115000]
[BENDING_FRACTURE:130000]
[BENDING_STRAIN_AT_YIELD:575]

Used game values for strength (which are all correct, upon verification) along with this research paper's data for Poisson ratio and Young's modulus, which can be calculated to bulk modulus and shear modulus by and , respectively (where ν is poisson's ratio and E is Young's Modulus).

Obsidian, too:

Code: [Select]
[IMPACT_YIELD:1000000]
[IMPACT_FRACTURE:1000000]
[IMPACT_STRAIN_AT_YIELD:3846]
[COMPRESSIVE_YIELD:1000000]
[COMPRESSIVE_FRACTURE:1000000]
[COMPRESSIVE_STRAIN_AT_YIELD:3846] bulk modulus 26 GPa
[TENSILE_YIELD:35000]
[TENSILE_FRACTURE:35000]
[TENSILE_STRAIN_AT_YIELD:53] young's modulus 66 GPa
[TORSION_YIELD:35000]
[TORSION_FRACTURE:35000]
[TORSION_STRAIN_AT_YIELD:114]
[SHEAR_YIELD:35000]
[SHEAR_FRACTURE:35000]
[SHEAR_STRAIN_AT_YIELD:114] shear modulus 30.7 GPa
[BENDING_YIELD:35000]
[BENDING_FRACTURE:35000]
[BENDING_STRAIN_AT_YIELD:53]

Poisson ratio 0.08. Poisson ratio and shear modulus, so I am way too lazy to photoshop right now, here's a table of every equation at the bottom of this page:

https://en.wikipedia.org/wiki/P-wave_modulus

All elasticity data auto-calculated with my material helper, but it's best to post the equations involved anyway.
« Last Edit: April 14, 2015, 03:45:40 am by Putnam »
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Armok

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Re: Proper bronze elasticity data
« Reply #1 on: April 06, 2015, 05:52:26 pm »

This has got to be the best post pointing out an inaccurate detail in a game ever. From it's politeness, to the fact of what that detail is.
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Putnam

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Re: Proper bronze elasticity data
« Reply #2 on: April 06, 2015, 06:01:38 pm »

Well, the file itself said that it was incomplete.

Bismuth bronze has the exact same values, too, so that should also be changed.

I'll do more research to determine if there's anything more I can find. For example, compressive strengths right now are simply 3.5x tensile values, and shear values are the same as tensile values.
« Last Edit: April 06, 2015, 06:07:25 pm by Putnam »
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Meansdarling

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Re: Proper bronze elasticity data
« Reply #3 on: April 06, 2015, 06:12:47 pm »

So awesome! Science.
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Putnam

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Re: Proper bronze elasticity data
« Reply #4 on: April 06, 2015, 06:48:39 pm »

Hmm. Here's what I think iron's physical properties should probably look like:

Code: [Select]
    [IMPACT_YIELD:155000]
    [IMPACT_FRACTURE:230000]
    [IMPACT_STRAIN_AT_YIELD:271]
    [COMPRESSIVE_YIELD:460000]
    [COMPRESSIVE_FRACTURE:920000]
    [COMPRESSIVE_STRAIN_AT_YIELD:271] bulk modulus 170 GPa
    [TENSILE_YIELD:155000]
    [TENSILE_FRACTURE:230000]
    [TENSILE_STRAIN_AT_YIELD:73] young's modulus 211 GPa
    [TORSION_YIELD:155000]
    [TORSION_FRACTURE:230000]
    [TORSION_STRAIN_AT_YIELD:109]
    [SHEAR_YIELD:89500]
    [SHEAR_FRACTURE:140000]
    [SHEAR_STRAIN_AT_YIELD:109] shear modulus 82 GPa
    [BENDING_YIELD:89500]
    [BENDING_FRACTURE:140000]
    [BENDING_STRAIN_AT_YIELD:109]

Vs current:

Code: [Select]
[IMPACT_YIELD:542500] Was 1080000, but just using 3.5x tensile multiples for everything until better numbers are available, which might not be likely
[IMPACT_FRACTURE:1085000]
[IMPACT_STRAIN_AT_YIELD:319]
[COMPRESSIVE_YIELD:542500]
[COMPRESSIVE_FRACTURE:1085000]
[COMPRESSIVE_STRAIN_AT_YIELD:319] bulk modulus 170 GPa
[TENSILE_YIELD:155000]
[TENSILE_FRACTURE:310000]
[TENSILE_STRAIN_AT_YIELD:73] young's modulus 211 GPa
[TORSION_YIELD:155000]
[TORSION_FRACTURE:310000]
[TORSION_STRAIN_AT_YIELD:189]
[SHEAR_YIELD:155000]
[SHEAR_FRACTURE:310000]
[SHEAR_STRAIN_AT_YIELD:189] shear modulus 82 GPa
[BENDING_YIELD:155000]
[BENDING_FRACTURE:310000]
[BENDING_STRAIN_AT_YIELD:73]

Reasons for the changes:

Impact "[applies] a Hertzian contact stress at the point of impact to a solid body, with compression stresses under the point, but with bending loads a short distance away". This suggests that IMPACT values should be COMPRESSION or BENDING, whichever's lower. Naturally, this is always bending, because...

Bending causes "the material at the over-side of the beam [to be] compressed while the material at the underside is stretched", with "Shear stress parallel to the lateral loading plus complementary shear stress on planes perpendicular to the load direction". Thus, it seems that it would be whatever is least of SHEAR, TENSILE and COMPRESSIVE (though I'm actually not entirely sure about that).

Bending, impact and torsion STRAIN_AT_YIELD values I'm unsure about; considering the way the game calculates blunt bypass and such, it's probably best that the IMPACT be identical to COMPRESSIVE. TORSION isn't used in-game at all, so that's not too worrisome, but SHEAR seems closest. BENDING is used only in wrestling calculations, but it's still important, and SHEAR seems also to be the closest here (though TENSILE might be good too).

TENSILE_YIELD I kept the same explicitly as a basis for all the other values.

TENSILE_FRACTURE value was taken from Cast iron 4.5% C, ASTM A-48 and multiplied by 155/130 (since said cast iron has 130 MPa tensile yield), taking significant figures into account.

All SHEAR values are ~.577 (inverse square root of 3) times TENSILE values.

COMPRESSIVE_FRACTURE is four times TENSILE_FRACTURE.

COMPRESSIVE_YIELD is COMPRESSIVE_FRACTURE divided by two, since I couldn't find better data.

STRAIN_AT_YIELD values  are changed in accordance with YIELD values.

Eldin00

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Re: Proper bronze elasticity data
« Reply #5 on: April 06, 2015, 07:16:22 pm »

It's good to see that you found a source for more data on bronze, I had a terrible time tracking down that one. I do wish that your source provided some information on what bronze alloy their number refers to though, since the term 'bronze' can apply to a variety of copper-tin, copper-silicon, copper-phosphorus, or copper-aluminum alloys.
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Putnam

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Re: Proper bronze elasticity data
« Reply #6 on: April 06, 2015, 07:42:06 pm »

I know it's not phosphorus, since it looks like it has phosphor bronze separately.

smakemupagus

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Re: Proper bronze elasticity data
« Reply #7 on: April 06, 2015, 08:13:06 pm »

Hey Putnam,

You're doing great work.  I suggest if possible that you don't mix the stats for pure and cast iron, as they're very different alloys. 

As you know, relatively pure wrought iron will be relatively soft.  While conversely, cast iron will be very brittle (really for the level of fidelity the game needs, I think cast might as well be the same as pig iron).  Neither is great as a weapon or tool, although no doubt plenty of conscripts all over the world had to make do with some inferior alloys.  But the "iron age" coincided with the development of various processes developed locally to make simple steels, either by carburization of pure iron, or by decarburization of cast iron.  Europe, asia, and africa all had steels in the BCE era, of varying composition and quality, which of course all improved a lot over time with experimentation.

I don't know what Toady really intends of course, but if it were me, I would probably use stats from a pure wrought iron for IRON and from a decent steel for STEEL.  ... That's nice because IRON can just be basically elemental iron and noone has to do a lot of historical research or make too much of a judgement call.

An alternative would be to use a basic mild steel for IRON, and use a more advanced steel for STEEL ... That's appealing since arguably it would reflect the historical practices of the Iron age more accurately.  But, someone would have to make a judgment call about which alloy gets to be which.

Putnam

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Re: Proper bronze elasticity data
« Reply #8 on: April 06, 2015, 08:29:33 pm »

I've tried to avoid mixing them wherever possible. Iron in-game seems to be a low-grade steel, weirdly enough. The iron there is purely a preliminary example and not really intended to replace stuff.

BoredVirulence

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Re: Proper bronze elasticity data
« Reply #9 on: April 07, 2015, 01:18:49 pm »

This is great. I use bronze predominantly, because its how I picture dwarves. Its always bothered me that its not better than iron.
I just might have to replace those metals RAWS with yours.
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Putnam

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Re: Proper bronze elasticity data
« Reply #10 on: April 07, 2015, 03:49:09 pm »

These proper raws actually make it worse, but okay.

Putnam

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Re: Proper bronze and steel elasticity data
« Reply #11 on: April 10, 2015, 02:06:13 am »

Updated OP with proper steel shear modulus. May make steel worse for cutting, but I'm not sure. It'll still be better than everything but adamantine, though.

EDIT: Also with bone data.
« Last Edit: April 10, 2015, 02:28:46 am by Putnam »
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Thief^

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Re: Proper bronze, steel and bone elasticity data
« Reply #12 on: April 10, 2015, 11:05:25 am »

I must say I seriously approve of this and hope you keep going (and I hope toady integrates the results!)
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Eldin00

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Re: Proper bronze, steel and bone elasticity data
« Reply #13 on: April 10, 2015, 01:45:16 pm »

I've been working on a similar project to this (also using Putnam's material helper). In addition to updating the material properties, I've been updating the the reactions for most of the alloys to be more in line with their real-world equivalents. If anyone is interested, the raws which have resulted from my efforts thus far can be found here. So far I've only worked on metals, and comments about my data sources and which specific alloys I based data on are in the inorganic_metal.txt raw file, if anyone is interested.
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AceSV

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Re: Proper bronze, steel and bone elasticity data
« Reply #14 on: April 12, 2015, 08:13:22 am »

Iron in-game seems to be a low-grade steel, weirdly enough.

That would be historically accurate, as early metalsmiths could not have extracted pure elemental iron.  As iron was exposed to the flames of the furnace, it was also exposed to the carbon content generating those flames.  Carbon also reduces the melting point of iron. 

If you wanted to be "accurate", this means that iron from a carbon fuel smelter might be chemically different from iron from a magma smelter, depending on the magma's carbon content.  Iron might also pick up some interesting impurities from magma fumes, but good luck finding numbers for that. 

EDIT:  (Actually, it looks like magma often contains magnesium, which would be a useful addition to steel)
EDIT2:  (No, I'm thinking of manganese)
« Last Edit: April 12, 2015, 08:27:39 am by AceSV »
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