Residual stress in 3 layer cantilever beam

1. Mar 29, 2007

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

2. Mar 30, 2007

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.

3. Mar 31, 2007

soiree

HI Ikalogic,

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!

4. Apr 1, 2007

Staff: Mentor

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.