Residual stress in 3 layer cantilever beam

[soiree]

Hi guys & girls,
I have a problem, I am trying to calculate the residual stress as a function of depth of each layer.

I am using a Focused Ion Beam system to milling/removal thin layers of material from each layer of this cantilever, & measuring the deflection.

I can obtain the average stress in each layer after removing the whole layer by using Stoney's equation. But am trying to predict / calculate the residual stress through the thickness of the layers.

The main problem I am having is that I have no idea how to find the neutral axis each time i remove a thin layer of each of the different layers.

the beam is made of Ti, SiO2, & Si. with Young's modulus 110, 85, 130 G Pa respectively.

Can anyone help?! I am so confused!
Cheers
Toby

 

[ikalogic]

DO you have access to a PC with Solid works and COsmos... a friend of mine made all stress calculations of our graduation robot on this software. if you'r interrested, tell me and i'll put you in touch with him.

 

[soiree]

HI Ikalogic,
no i don't have access to to either of those packages; i do have access to Matlab & DaVis 7.2.

If you wouldn't mind putting me in touch with him that would be great!

I am also trying to model the residual stress as a function of thickness in thin films using the slot method [i.e. milling a slot of know length, width, depth & looking at the stress relaxation / by measuring relative movements of the top surface before & after milling the slot].

Much appreciated!

 

[berkeman]

I'd like to try moving this question from the EE forum to the General Physics forum for a bit. This is a complicated question that deserves a wider set of views.