Mechanics of neck formation in the cold drawing of elastic films

A discussion is given of the unidirectional, but nonuniform stretch of long, wide strips of film. It is observed that each of the material functions, τ, β, γ, in a recently proposed unidimensional theory of neck formation and cold drawing for bars of small but not zero thickness is determined, in the case of a strip of film, by the strain‐dependent shear modulus μ of the three‐dimensional material of which the bar is composed. The dependence of the shear modulus μ on shear strain and of τ, β,and γ on axial stretch is evaluated for a model of an elastic material susceptible to cold drawing, and the calculated values of τ, β,and γ, are used to draw film profiles for various stages of neck formation.