Consider two objects made of different isotropic materials A

Consider two objects made of different isotropic materials (Aluminium and Steel) but with the same geometry, loads and boundary conditions. Which of the materials would have a higher stress and why?

Solution

Neglecting Poisson effect, if uniaxial stresses are concerned, the elastic range stresses in both aluminium and steel would be the same. This is due to the stress definition, that is Stress = Load / Area.

In case the Poisson effect is considered, then the stresses would be different as we take into account the cross-section changes under the loading.