3 point bending nanodiamond test

[cdnprodigy]

I have a question regarding the compressibility of a nanodiamond. It is regarding the steric accuracy of a diamond probe surface.

Assuming a block of singly nucleated nanodiamond 100 X 100 X 100 nm. Assuming a section *magically* cut out of the middle measuring 75 X 75 X 1 nm. The goal is to press the sides of the diamond block and have the cutout inner surface faces touch. My question is, would the diamond fracture before the opposing cutout surfaces touched?

I think this is basically a three point bending test of a very small chunk of diamond measuring 75 X 75 X 49.5 nm. Could the diamond be bent 4 or 5 angstroms along its 49.5 nm thickness before fracturing? I'm sure there is an equation to plug in numbers, but I don't yet know what it is. Thx.

 

[NickE]

Easy to do if you know the modulus, Yield, and Tensile strengths, along with Poisson's ratio.

(FEA would be handy as this is a simple geometry.)

That said mechanics was my worst area of materials. I could build an FEA model to do this but couldnt check it. (IE: I forgot how to do manual mechanics.)

 

[CoryPad]

As diamond has strong covalent bonds, it has linear behavior up to fracture, therefore it won't have a yield point.

A simple strength calculation could be done, but really this is a fracture mechanics question. To determine the behavior, you would need elastic modulus, Poisson's ratio, and the fracture toughness of diamond.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[NickE]

Thanks for pointing out my error Cory, and thinking about it I dont think that 3-pt bending is a good simplification.

 

[IRstuff]

This is more the realm of a uniformly loaded plate with straight sides, ala Roark and Young, Chapter 10, Table 26.

Not sure if the standard values are valid for this thin a plate, though...

TTFN