a) Explain the differences in the necked regions for the two tensile specimens (one made of metal and the other made of plastic) and why they occur?
b)Is the material in the necked region of the polymer mechanically the same as the material in the unnecked region? how are they different? is the polymer(HDPE) material initially isotropic? is the material in the necked region isotropic?
c) What would an idealized load- deflection curve for a polymer look like for a specimen where a neck forms begin to propagate?