Hello,

Given that,

diameter = d = 16 mm

elongation = dL = 0.08 mm

Modulus of Elasticity = 200 GPa = 200 x 10^3 N / mm^2

Gauge Length = Length of specimen used for test = L = 80 mm

We know that,

E = stress / strain

So, E = stress / ( dL / L )

So, 200 x 10^3 = stress / ( 0.08 / 80 )

So, stress = 200 N / mm^2

Hence, the maximum stress in the material is 200 N / mm^2

Best Wishes.