Young's Modulus/Poisson Ratio

[RAD17]

I need to determine Young's modulus and Poisson's ratio from the elastic stiffnesses for a cubic crystal that is being stressed along the x axis.
It is initially L *w and goes to (L+delta L)*(w - delta w). Where w is along the x-axis and L is along the y axis. How do I change stresses and strains along with lengths into elastic stiffnesses?

 

[radou]

I need to determine Young's modulus and Poisson's ratio from the elastic stiffnesses for a cubic crystal that is being stressed along the x axis.
It is initially L *w and goes to (L+delta L)*(w - delta w). Where w is along the x-axis and L is along the y axis. How do I change stresses and strains along with lengths into elastic stiffnesses?

What exactly do you mean by ' L*w '? Do you know the stresses?

 

[Clausius2]

Looking into some elasticity book you'll find:

-The change in volume of the cube is relationed to the poisson coefficient, such that for poisson coefficients 1/2 the body is incompressible.

-The stresses, deformations, elastic modulii and poisson coefficient are relationed through the Hooke's law.