jupitersterrain four

As deformation proceeds the geometric instability causes strain to continue concentrating in the neck until the material either ruptures or the necked material hardens enough, as indicated by the second tangent point in the top diagram, to cause other regions of the material to deform instead. The amount of strain in the neck is called the natural draw ratio.  because it is determined by the material's hardening characteristics, not the amount of drawing imposed on the material. Ductile polymers often exhibit tense necks because molecular orientation provides a mechanism for hardening that predominates at large strains


23.45, 1.12.12.