Solid mechanics

1. Nov 21, 2009

Dell

now i am looking for the stress $$\sigma$$ for the aluminium and for the steel
i would want to say simply $$\sigma$$=F/A but i need to somehow take into account the types of materials and their elasticity,
i think that hookes law could help me here but i dont know the strains
also how do i take the volume into account? the only equation i have for volume is $$\Delta$$=$$\epsilon$$x + $$\epsilon$$y + $$\epsilon$$z, but i doubt thats going to help

2. Nov 21, 2009

Mapes

You know a little about the strains, since the rigid top plate supplies a constraint on the components' deformation. What can you say about the strain of the steel and aluminum?

Each component will have its own stress, cross-sectional area, and force. Can you relate the forces to the applied load?

3. Nov 21, 2009

Dell

i would think that the aluminium and steel have the same strains.
i can find the ratio of forces on each material as their area of the rigid plate? is this correct?

F(Al) = 4P/7
F(Steel)= 3P/7

-------------

can i say that since i only have forces on the y axis

$$\sigma$$=$$\epsilon$$*E

now since the strains are the same

$$\sigma$$Al=$$\epsilon$$*70*109
$$\sigma$$Steel=$$\epsilon$$*200*109

now i have t equations and 3 unknowns, but i know

$$\sigma$$Al*2*10-3 + $$\sigma$$Steel*1.5*10-3=385*103

thanks for the help

4. Nov 21, 2009

Dell

does that mean that the stress has nothing to do with the height of the element

5. Nov 21, 2009

Mapes

That's what it looks like.