Same E for true stress true strain?

[kelvin490]

Before yield we know that stress/strain= E. Can we obtain the same E if we substitute true stress and true strain in the equation? Why

 

[PhanthomJay]

For materials that approximately obey Hookes law in the elastic region prior to yield (steel being the classic example), the true E modulus is slightly higher, but insignificant. True stress versus engineering stress becomes significant after yield , especially when necking begins. Before yield, the reduced area of the cross section is a rather small percentage of the original.