# Solid mechanics

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

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Mapes
Homework Helper
Gold Member
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?

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

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

Mapes