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Old 07-21-2002, 12:09 PM   #61
SaabJohan
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Quote:
Originally posted by 454Casull
No, I'm just wondering why it's used.
Because of the weight-to-stiffness-to-strength ratio. It also conduct heat very well. MMC should even be superior to the aluminum-beryllium alloy earlier used (Al-Be was banned in F1 since it's poisonous).

According to NASA’s Marshall Space Flight Center, MMC parts can give a weight reduction of at least 45% with the same material and design requirements.
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Old 07-21-2002, 10:20 PM   #62
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here's a question for you, SJ, since you mentioned a favorable weight-to-stiffness ratio:

What's the average young's modulus for a typical Al-SiC MMC used in a piston? What's the density of that MMC? (I'd be surprised if E/r was much different for MMC than for Al or Steel)
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Old 07-22-2002, 10:13 AM   #63
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Quote:
Originally posted by ivymike1031
here's a question for you, SJ, since you mentioned a favorable weight-to-stiffness ratio:

What's the average young's modulus for a typical Al-SiC MMC used in a piston? What's the density of that MMC? (I'd be surprised if E/r was much different for MMC than for Al or Steel)
It's hard to find good info on theese materials but this is what I've found:

The properties of the material depends on how much SiC there are in the aluminum, but I think the content of SiC for piston material is high.
First the strength, an Al alloy can have around 300 MPa in ultimate tensile strength. If we have an MMC containing around 35% SiC the strength will be around 600 MPa.
I've haven't found anything about the density, but the young's module divided by density is a little above 50 GPa. Steel, aluminum, titanium and magnesium have a number of around 28 GPa.
MMC is also very hard and have a low coefficient of heat expansion.
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Old 07-22-2002, 10:53 AM   #64
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I think you got your units wrong on those figures, but the scalar value for steel seems to be approx. correct. I get 26.4E+6 N*m/kg for steel.

If your figures for the MMC are correct, I'm very interested in using it in a few frequency-sensitive applications within a high performance engine. Do you happen to have contact information for a supplier of this material?
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Old 07-22-2002, 05:01 PM   #65
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The units are correct but the values are just approx.

Don't know any company that manufacture these materials but it shouldn't be impossible to find out.

I know two manufacturers that make products in mmc, pistons, liners and sleeve coatings. The coating is used in for example F1, Cart, BTCC and Nascar.
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Old 07-22-2002, 05:04 PM   #66
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SJ, how can you possibly divide GPa by density and end up with GPa? Density isn't unitless!

for steel: E = 207GPa, rho = 7850 kg/m3, E/rho = 26.4E+6 N*m/kg
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Old 07-22-2002, 05:09 PM   #67
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here is some further info on a particular kind of MMC: http://www.matweb.com/search/Specifi...bassnum=NAMC20
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Old 07-22-2002, 05:21 PM   #68
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I used the units that I found here, http://www.csm.se/ which is the same place I got the data from.
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Old 07-22-2002, 06:41 PM   #69
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I'm guessing that you used specific gravity, rather than density (sg is unitless, and gives the right magnitude on the answer)... I didn't think of that before I posted previously.

In case the terminology isn't the same everywhere, specific gravity is the density of a material divided by the density of water. Thus steel has a s.g. of about 7.85 (unitless).

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