Solid Mechanics: Calculating Stress for Aluminium & Steel

[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 don't 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 that's going to help

 

[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?

 

[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

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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

 

[Dell]

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

 

[Mapes]

That's what it looks like.