Use of MMC in engines
Use of MMC in engines
(OP)
Does anyone have information in regard to the applications of metal matrix composite (MMC) materials within piston engines? I understand that MMC (Al-SiC variety) is used in F1 pistons, and perhaps a few other applications.
I'm interested in finding a supplier for this sort of material, and if someone could give me some contact info I'd appreciate it.
I'd also like to know what the material strength and fatigue properties of various MMCs are, so that I may determine their suitability to an application that I have in mind.
I'm interested in finding a supplier for this sort of material, and if someone could give me some contact info I'd appreciate it.
I'd also like to know what the material strength and fatigue properties of various MMCs are, so that I may determine their suitability to an application that I have in mind.





RE: Use of MMC in engines
for many years we have struggled with driveshaft whirl, since in the past we've resisted going to a two piece driveshaft. Our driveshaft supplier came up with an MMC driveshaft, which improved the whirl speed (basically root E/rho) by 15%. He also gave us a video showing what happened at whirl. A steel or aluminium shaft flips out, and then twists itself into a knot and breaks in half, which is fairly exciting, at 5000 rpm, but not too bad. The MMC shaft flipped out, and then exploded into a hail of shrapnel.
The supplier was Dana, perhaps they could help you.
Cheers
Greg Locock
RE: Use of MMC in engines
Lemme take a guess about your driveshaft, to see if I'm on the right page. The trouble with a 1-piece driveshaft is that it's got a solid center, and thus a low whirl frequency, right?
RE: Use of MMC in engines
We used aluminium sometimes because it is more highly damped than the steel ones, so it is better for gear noise etc. We could also get it in a bigger o d, which does improve the frequency a bit.
One rather nasty solution is to use a carbon wrapped aluminium shaft - this only buys you about 5-10% or so, because the stiffness mismatch between the aluminium and the carbon results in an inefficient use of teh aluminium. The cost is ridiculous.
Cheers
Greg Locock
RE: Use of MMC in engines
In regard to "roughly proportional," if I remember right, that's true for thin-walled shafts, but not solid ones. For the thin-walled ones, the only ways to bring up the frequency that come to mind are to increase the OD of the tube (perhaps maintaining the same wall thickness), and to reduce the length of the tube. I don't have the eqns in front of me, so please correct me if I'm wrong on that. I assume that something gets in the way if you increase the diameter, which is why you'd strap a bearing in there? A big, long, fat shaft is probably more expensive and prone to dents, dings, and miscellaneous abuse too... Please tell me more about the constraints, if you get a chance.
I once had a client ask why I'd suggested a hollow shaft for his (high-speed) application. He'd expected a thick solid shaft. I said "because it increases the whirl frequency," to which he replied "how can it possibly do that?" I tried to find a polite way to explain the relationship between the area moments of inertia and mass per unit length, and I think I pulled it off w/o embarassing him. Tough to say though...
Anyone else out there - I'm still looking for a MMC supplier (haven't called Dana yet).
RE: Use of MMC in engines
OD is more or less fixed by clearance to floor (above), exhaust (right) fuel tank (left) ground clearance line (below), and what the customer actually cares about, the size of the tunnel.
Cheers
Greg Locock
RE: Use of MMC in engines
I can't (of course) comment on the usefulness of MMC in that application.
RE: Use of MMC in engines