Maximum Modulus of Elasticity 3

[duc916]

I am designing a part that is a long slender rod that must be very stiff. Most of the steels I have looked at have a modulus of elasticity that is very similar. Is there an alloy that has a very high modulus of elasticity (maybe a metal matrix)? I am not concerned at this point about buckling the column due to the design parameters; my primary concern is to reduce deflection. I am running geometry iterations in FEA now, but a higher modulus is needed. Thanks for the help.

Dan

 

[alexit]

There is a high-stiffness metal called ferro-titanit:

http://www.edelstahl-witten-krefeld.de/en/lieferprogramm/ferro_titanit/index.jsp

We have successfully used this for making very long tooling arbors for grinding. There are many grades, but it is basically ~5 micron grain size titanium in interstitial matrix with steel alloy.

This is a workable material, but machines more like titanium than steel (slowly and with great forces.)

Alex

 

[funnelguy]

Try tungsten carbide. 2-4X Stiffer than steel and available in the form you describe.

Alternatively look at SiC and some other ceramics. Steel is pretty much steel.

 

[NickE]

yeah- steel pretty much has the same modulus no matter the alloy or temper.

for why go here:
thread330-87802

read down a few posts... Maui gives a great qualitative description and then follows with a more quantitative description.

nick

 

[duc916]

Funnelguy,
Can SiC and other ceramics handle shock? The impression I have of ceramics is they can not handle any shock loads; this rod is an actuator with an input frequency of around 83 Hz (5000 rpm).

Alex,
I was told that the ferro-titanit does not have very good wear characteristics. What is the best way to attach a wear surface to it, furnace brace, press fit, adhesive, etc.?

Thanks for the help; I will check the materials you guys listed above.

 

[JTreglio]

I would suggest you consider a PVD coating, like TiN, if the ferro-titanit does not provide adquate wear resistance. If properly deposited, the PVD coating will hold up extremely well.

Jim Treglio
Molecular Metallurgy, Inc.

 

[EdStainless]

Tungsten Carbide with less than 7% Co binder. Use a fine or microfine grain for better toughness. E is up around 90million psi.
SiC is the other choice.

Corrosion never sleeps, but it can be slowed down.

 

[funnelguy]

duc916,
You mention that buckling won't be a problem and that you wish to minimize deflection of this long slender rod. I figure that unit stress must be pretty low and that your fight, therefore, is to achieve some relatively low strain value. Am I close or do I misunderstand the application? The long, slender rods I am familiar with are why the Euler formulas exist!

Anyway, the density of tungsten carbide may be an issue for an actuator (pushrod?) at 5000 RPM. Perhaps some of the materials experts could comment on the suitability/availability of silicon nitride for this appication. Could you possibly post envelope dimensions for this actuator rod? I hope you don't have design specs that force the use of unobtanium or such!

When you hear hoofbeats, think horses, not zebras...

 

[alexit]

In our rotating application Tungsten was too dense, made for a low natural frequency (the reason we needed more stiffness) so was Rhenium.

Ferro-titanit is titanium in 440C stainless steel matrix material. (Almost) anything you would do to 440C for wear can be done to this material. PVD or plating, ion implantation or surface treatments will give you good surface wear.

Consider SiN as a ceramic alternative...it is used as the ball in ball bearings in many applications. Once, many years ago, the Cerbec company gave ball samples away with a prize if you could break one. We froze it to -100°C then placed it on a hardened anvil and applied 20 metric tons using a press (it drove the ball into the anvil, but not a scratch to the ball.) Others tried hammers, etc. even firing it from a black powder rifle into (through) a concrete block. I know that only one person ever collected the prize and he used thermal stress and impact loading together to chip the ball.

 

[TVP]

alexit,

Ferro-titanit is Titanium Carbide particles dispersed in a steel matrix, not titanium metal.

 

[alexit]

I stand corrected