wb
New Member
Posts: 8 
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Post by wb on Sept 27, 2016 0:19:58 GMT
Did I do this right? I had to lower the Young's Modulus from 1000 GPa that I saw in the literature to 800 GPa to keep the game from crashing because of the Poisson's Ratio. I'm not a materials scientist so I'm doing this somewhat blind. I'm sure the values are way better than you'd get in reality even after a bunch of development, if I knew what they did I'd probably make them worse but as it is I'm not sure what direction to change them in (besides obvious stuff like melting point or yield strength). The stuff I couldn't find quickly I just assumed (probably wrongly) to be close to graphite.
Material Graphene
Elements C
ElementCount 1
Density_kg__m3 2230
YieldStrength_MPa 130000
UltimateTensileStrength_MPa 130000
YoungsModulus_GPa 800
ShearModulus_GPa 280
BulkModulus_GPa 8
MeltingPoint_K 4900
SpecificHeat_J__kg_K 51000
ThermalConductivity_W__m_K 2500
ThermalExpansion__K -8e-6
ThermoelectricSensitivity_V__K 9e-5
Resistivity_Ohm_m .001
RefractiveIndex Graphite
RoughnessCoefficient 0.9
I had to replace the file in Data/Materials to actually get this to load, putting it in Mods\Data\Materials\Nonmetals.txt didn't seem to do anything.
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Post by Esterov on Jan 6, 2017 5:03:31 GMT
I was trying to mod in Sodium Chloride, I'm also running into problems with the Poisson Ratio assert Assertion at Logistic\Physics\Materials.cpp(328): Between(PoissonsRatio, -1., .5)Material Sodium Chloride
Elements Na Cl
ElementCount 1 1
Density_kg__m3 2165
MeltingPoint_K 1071
BoilingPoint_K 1686
SpecificHeat_J__kg_K 880
YoungsModulus_GPa 39.96
ShearModulus_GPa 8.97
BulkModulus_GPa 24.32
ThermalConductivity_W__m_K 6.5
ThermalExpansion__K 40.0e-6
EnthalpyOfFormation_kJ__mol -411.12(Sourced from Wiki and www.almazoptics.com/NaCl.htm ) |
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Post by n2maniac on Jan 6, 2017 7:11:10 GMT
There are 3 things that describe material stiffness: YoungsModulus (E) ShearModulus (G) BulkModulus (K) And Poissons ratio that describes (roughly) how two sides of a beam being bent either compress or stretch, related to where the material does not stretch at all (its neutral axis). It is better explained here. The assertion is saying "what a minute, a beam should not have its neutral axis outside of the material, something has gone wrong!". Wikipedia has a good description here of how they connect to Poissons ratio. Specifically: For wb, BulkModulus is way off (I don't know the correct value, but it isn't 100x lower than Young's Modulus). For Esterov, my first guess is shear modulus is low. In general, if you are making a new material, you need all 3 moduli. If you need to guess at one, lookup the Poisson ratio for a similar material, assume it is the same, and solve. If the object isn't being used structurally or thermally stressed, copy something that is close. Hope this helps. |
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Post by Esterov on Jan 6, 2017 20:22:43 GMT
Thank you, that helped a lot actually. I looked up another source for Sodium Chloride, and I found two other sources that explain the Poisson ratio to be between 0.203 and 0.26. The other of those websites also provides the Modulus values: Poisson Ratio: 0.26 Young's Modulus: 39.98 GPa Shear Modulus: 12.61 GPa Bulk Modulus: 24.42 GPa (Source: www.korth.de/index.php/162/items/24.html ) But plugging 0.26 as v, 12.61 GPa as G, 39.98 GPa as E and 24.32 GPa as K Gives me the following equation 2 * 12.61 GPa * (1 + 0.26) = 39.98 GPa = 3 * 24.32 GPa * (1 - 2 * 0.26) Which creates.. this result 31.72 GPa = 39.98 GPa = 35.02 GPa Am I not following the equation right, are the values on the website wrong. Or is sodium chloride governed by different rules or something? (Also, plugging in the new modulus values causes an assert fail again because the Shear Modulus portion == Young's Modulus if v ~= 0.585) |
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Post by n2maniac on Jan 7, 2017 6:18:15 GMT
Esterov Interesting problem. Might be that sodium chloride is not quite isotropic (since the crystal directions are ordered, material properties can differ a bit depending on if you measure with atoms lined up or not). After looking at some of the material files, I don't see bulk modulus listed very often. For instance: Material Diamond
Elements C
ElementCount 1
Density_kg__m3 3520
YieldStrength_MPa 1600
UltimateTensileStrength_MPa 2800
YoungsModulus_GPa 1220
ShearModulus_GPa 508.3
MeltingPoint_K 3823
BoilingPoint_K 5100
SpecificHeat_J__kg_K 519
ThermalConductivity_W__m_K 2100
ThermalExpansion__K .9e-6
ThermoelectricSensitivity_V__K 20e-6
Resistivity_Ohm_m 1e18
DielectricStrength_MV__m .1
RelativePermittivity 5.7
BandGap_eV 5.5
LasingDamageThreshold_TW__m2 .00051
RefractiveIndex Diamond
RoughnessCoefficient 0.1I would try omitting BulkModulus and see if it still complains. If so, I will edit my previous post to to a better recommendation (regarding bulk modulus). Also, random thing for wb that I couldn't help but notice: your specific heat of graphene looks really high (like, 10x that of water, which is typically a red flag). 700 - 2000 J/kgK is more reasonable. Its not going to make much of a difference unless it ends up being a shield against nukes / lasers, but it is off.
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Post by Esterov on Jan 7, 2017 8:56:50 GMT
Removed Bulk Modulus, still crashes due to an invalid poisson ratio.
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Post by n2maniac on Jan 7, 2017 9:38:56 GMT
Removed Bulk Modulus, still crashes due to an invalid poisson ratio. Ugh, right, it still sees that issue from the remaining two values. Ultimately, we have to either convince the game that it doesn't have to follow that rule or bring the values into compliance. This source lists the shear and bulk moduli as ranges: For Poisson's ratio to be 0.203, we need E = 2 * 1.203 * G = 2.406 * G. Shear numbers there give: Shear (GPa) -> Young GPa
15.9 38.3
12.8 30.8I know there is still something I am not understanding here, but I think you will need to use different values than you originally found. The big one for E & G to yield v between -1 and +0.5 is 0 < E < 3G. The source that indicated these values doesn't compute an invalid Poisson ratio, so I will recommend starting there. Hope that helps. |
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Post by bigbombr on Jan 7, 2017 13:02:43 GMT
Did I do this right? I had to lower the Young's Modulus from 1000 GPa that I saw in the literature to 800 GPa to keep the game from crashing because of the Poisson's Ratio. I'm not a materials scientist so I'm doing this somewhat blind. I'm sure the values are way better than you'd get in reality even after a bunch of development, if I knew what they did I'd probably make them worse but as it is I'm not sure what direction to change them in (besides obvious stuff like melting point or yield strength). The stuff I couldn't find quickly I just assumed (probably wrongly) to be close to graphite. Material Graphene
Elements C
ElementCount 1
Density_kg__m3 2230
YieldStrength_MPa 130000
UltimateTensileStrength_MPa 130000
YoungsModulus_GPa 800
ShearModulus_GPa 280
BulkModulus_GPa 8
MeltingPoint_K 4900
SpecificHeat_J__kg_K 51000
ThermalConductivity_W__m_K 2500
ThermalExpansion__K -8e-6
ThermoelectricSensitivity_V__K 9e-5
Resistivity_Ohm_m .001
RefractiveIndex Graphite
RoughnessCoefficient 0.9
I had to replace the file in Data/Materials to actually get this to load, putting it in Mods\Data\Materials\Nonmetals.txt didn't seem to do anything. If you're adding this, you might want to look at this: advances.sciencemag.org/content/3/1/e1601536.full |
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Post by RiftandRend on Jan 25, 2017 1:03:50 GMT
Did I do this right? I had to lower the Young's Modulus from 1000 GPa that I saw in the literature to 800 GPa to keep the game from crashing because of the Poisson's Ratio. I'm not a materials scientist so I'm doing this somewhat blind. I'm sure the values are way better than you'd get in reality even after a bunch of development, if I knew what they did I'd probably make them worse but as it is I'm not sure what direction to change them in (besides obvious stuff like melting point or yield strength). The stuff I couldn't find quickly I just assumed (probably wrongly) to be close to graphite. Material Graphene
Elements C
ElementCount 1
Density_kg__m3 2230
YieldStrength_MPa 130000
UltimateTensileStrength_MPa 130000
YoungsModulus_GPa 800
ShearModulus_GPa 280
BulkModulus_GPa 8
MeltingPoint_K 4900
SpecificHeat_J__kg_K 51000
ThermalConductivity_W__m_K 2500
ThermalExpansion__K -8e-6
ThermoelectricSensitivity_V__K 9e-5
Resistivity_Ohm_m .001
RefractiveIndex Graphite
RoughnessCoefficient 0.9
I had to replace the file in Data/Materials to actually get this to load, putting it in Mods\Data\Materials\Nonmetals.txt didn't seem to do anything. The density seems more like 2.23 kg/m3, not 2230 kg/m3 |
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Post by theholyinquisition on Jan 25, 2017 1:32:03 GMT
I always put the modded materials into their appropriate files(vitreous carbon in non-metals, for instance). Have I been doing it wrong? |
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Post by mmmfriedrice on Jan 25, 2017 16:45:28 GMT
I've inserted them directly into the data files, as it doesn't seem to remember the materials if I put them in the mods folder, and all my modules reset.
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