Bay 12 Games Forum
Dwarf Fortress => DF Modding => Topic started by: Uristocrat on May 06, 2011, 04:36:08 am
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I've found a cool site that has more data than I knew existed for all kinds of wood. The problem is that they report everything in terms of things like MOR (modulus of rupture), MOE (modulus of elasticity) and WML (work to maximum load) and I don't know which DF values those correspond to. And then I have to make sure I've got the units right.
For example, here's the data on mangrove wood (http://www.fpl.fs.fed.us/documnts/TechSheets/HardwoodNA/htmlDocs/avicenniaeng.html) (EDIT: also in metric units (http://www.fpl.fs.fed.us/documnts/TechSheets/HardwoodNA/htmlDocs/avicenniamet.html)). It's black mangrove (Avicennia spp.), if you're curious. The density (actually, specific gravity) is the only thing on that table I'm convinced I fully understand right now.
I know that DF has material definition tokens (http://df.magmawiki.com/index.php/DF2010:Material_definition_token) and I've read all about those, but there's not a lot of information, even when cross-referenced with the data on armor quality (http://df.magmawiki.com/index.php/Metal#Weapon_.26_Armor_Quality) that gives a helpful table with some units.
I also looked up the MOR, MOE and WML (http://ezinearticles.com/?Hardwood-Mechanical-Properties---What-Do-They-Really-Mean?&id=4919469) and while I found some good explanations (http://tinytimbers.com/cypress_info.htm), it's still pretty hard to convert this stuff into values DF can actually use.
Is the MOE bending yeild? Is the MOR bending fracture? I'm not quite sure. I get really, really high numbers when I try to convert those values (in millions of lbf/in2!) to Pa, which is supposed to be what the raws use. It's at 10,000 now and I'm getting a value in the 1010 range, so I must have something wrong. The compression table looks like it should be related to compressive yield and maybe WML is related to impact yield. Shear might be related to shear yield.
But I'm just not sure. Add to the fact that I'm getting wildly different values out of Google calculator than anything I see in the raws and I start to think that I'm doing something wrong.
Does anyone more familiar with this stuff know which of these things correspond to what in DF? Or maybe someone can make sure that I'm converting things to the proper units? (DF Wiki seems to indicate that the raw values are in Pa, even though it lists them in kPa).
EDIT: I guess you can convert the data sheets to metric just by clicking the link on the page. That doesn't help much. It shows that I have values in MPa. DF uses Pa, per the wiki. So either that value isn't used in DF at all, or DF isn't giving wood nearly enough credit for... something.
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Oh yeah, I found an interesting article on the DF Wiki about material science (http://df.magmawiki.com/index.php/Material_science), but it doesn't quite help me know which things match up with which.
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I've found a cool site that has more data than I knew existed for all kinds of wood. The problem is that they report everything in terms of things like MOR (modulus of rupture), MOE (modulus of elasticity) and WML (work to maximum load) and I don't know which DF values those correspond to. And then I have to make sure I've got the units right.
For example, here's the data on mangrove wood (http://www.fpl.fs.fed.us/documnts/TechSheets/HardwoodNA/htmlDocs/avicenniaeng.html) (EDIT: also in metric units (http://www.fpl.fs.fed.us/documnts/TechSheets/HardwoodNA/htmlDocs/avicenniamet.html)). It's black mangrove (Avicennia spp.), if you're curious. The density (actually, specific gravity) is the only thing on that table I'm convinced I fully understand right now.
I know that DF has material definition tokens (http://df.magmawiki.com/index.php/DF2010:Material_definition_token) and I've read all about those, but there's not a lot of information, even when cross-referenced with the data on armor quality (http://df.magmawiki.com/index.php/Metal#Weapon_.26_Armor_Quality) that gives a helpful table with some units.
I also looked up the MOR, MOE and WML (http://ezinearticles.com/?Hardwood-Mechanical-Properties---What-Do-They-Really-Mean?&id=4919469) and while I found some good explanations (http://tinytimbers.com/cypress_info.htm), it's still pretty hard to convert this stuff into values DF can actually use.
Is the MOE bending yeild? Is the MOR bending fracture? I'm not quite sure. I get really, really high numbers when I try to convert those values (in millions of lbf/in2!) to Pa, which is supposed to be what the raws use. It's at 10,000 now and I'm getting a value in the 1010 range, so I must have something wrong. The compression table looks like it should be related to compressive yield and maybe WML is related to impact yield. Shear might be related to shear yield.
But I'm just not sure. Add to the fact that I'm getting wildly different values out of Google calculator than anything I see in the raws and I start to think that I'm doing something wrong.
Does anyone more familiar with this stuff know which of these things correspond to what in DF? Or maybe someone can make sure that I'm converting things to the proper units? (DF Wiki seems to indicate that the raw values are in Pa, even though it lists them in kPa).
EDIT: I guess you can convert the data sheets to metric just by clicking the link on the page. That doesn't help much. It shows that I have values in MPa. DF uses Pa, per the wiki. So either that value isn't used in DF at all, or DF isn't giving wood nearly enough credit for... something.
Your first link points to weird and a-typical descriptions. Typically MOE refers to modulus of elasticity. It's the slope of the elastic portion of the stress-strain curve. Typically the yield strength is the amount of stress (force per area) that's required to cause a permanent change in length of an object. Think of a rubber band, when you stretch the rubber band far enough it doesn't return to the same shape, it gets a little looser. That mean's you just temporarily exceeded the tensile yield strength of the rubber while stretching it.
In terms of sources for wood, I would check out matweb.com and search for wood. They have some very, very good data there. The nasty thing about yield data is that it is path-dependent, unlike the modulus. So a piece of iron which has been hammered into a spear blade is going to yield at a different stress than the iron wire used to make chain mail.
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Your first link points to weird and a-typical descriptions. Typically MOE refers to modulus of elasticity. It's the slope of the elastic portion of the stress-strain curve. Typically the yield strength is the amount of stress (force per area) that's required to cause a permanent change in length of an object. Think of a rubber band, when you stretch the rubber band far enough it doesn't return to the same shape, it gets a little looser. That mean's you just temporarily exceeded the tensile yield strength of the rubber while stretching it.
In terms of sources for wood, I would check out matweb.com and search for wood. They have some very, very good data there. The nasty thing about yield data is that it is path-dependent, unlike the modulus. So a piece of iron which has been hammered into a spear blade is going to yield at a different stress than the iron wire used to make chain mail.
Well, the data I was looking up was specific to wood, if that matters. I'm not sure if MatWeb has data per type of wood? Searching for "wood" (or even "mangrove wood") gives me a ton of results for "North Wood Plastics" ... This might be a better data source for alloys and the like.
And I still need to figure out how to convert that into DF-usable information. But thank you for the reply, the thread vanished and I didn't notice it for quite a while.
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Matweb aggregates data from various material suppliers, and can be kind of wonky, but there is plenty of data on wood there (there are 287 entries under wood, some of which are composite products). The best way to access it is by clicking on material catagory search and then navigating by the menu on the right.
Speaking specifically about mangrove, you won't find it anywhere because mangrove is a generic term for tress (and shrubs) which grow in a certain environment. It's not actually a species of wood.
For example here are some data sheets from Matweb:
Northern White Pine
http://www.matweb.com/search/DataSheet.aspx?MatGUID=9412b2f342c7407abfecfa1420560b37
American Western red cedar:
http://www.matweb.com/search/DataSheet.aspx?MatGUID=d88f1ca91b534780a7c8c7dda02ae0dd
North American red oak:
http://www.matweb.com/search/DataSheet.aspx?MatGUID=3a971164050b4313930591eed2539366
African Mahogany:
http://www.matweb.com/search/DataSheet.aspx?MatGUID=8188e7e1f11b4deb9fd67fe18d83e272
American Red Maple:
http://www.matweb.com/search/DataSheet.aspx?MatGUID=67e57f907bc842259e268a5c8e4a7457
European willow:
http://www.matweb.com/search/DataSheet.aspx?MatGUID=d0fce8e05e2d41ae9676addf6aeb3e6c
There are often multiple datasheets for a given DF term (for example there are three different types of oak), often with different values. They tend to be pretty close however, so averaging or picking one should both work fine.
These data sheets report on many of the same categories as DF. I can't help you with the DF units though. Perhaps you could compare the DF values for well know materials (iron, copper, gold) to real world values and see if you can come up with a conversion that makes sense?
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The 'Hardwood Mechanical Properties' link does seem quite dubious, as BishopX pointed out. Modulus of elasticity in itself is an inexact term, as there are multiple moduli of elasticity. From what I read from the tinytimbers.com link, I suspect that here it refers to, or at least corresponds to shear modulus. It doesn't show up in raws on its own, but it tells us the ratio between SHEAR_YIELD and SHEAR_STRAIN_AT_YIELD. We can also deduce the other moduli from it if we know the Poisson's ratios (anisotropic materials have more than one) for the material.
Modulus of rupture seems to stand in for bending strength, except it is usually used to describe brittle anisotropic material. If so, it would be equal to BENDING_YIELD, and possibly BENDING_FRACTURE.
Wood however is not brittle, so we need an additional term to describe the amount of energy it can still absorb after yielding. Thus we have WML, which seem to be the toughness of the wood in question. WML has no equivalent in raws as DF doesn't take the toughness of materials into account yet. If we made an assumption about woods stress-strain curve after yield, we could use WML to calculate strain to failure, but DF doesn't use that either.