If the stresses that cause deformation in a body are not uniform, differences develop between the strains in the different regions. These differences depend on the level of n. If n is high, the difference will be less than if n is low. A tensile bar in which the cross-sectional area of one region, Aao, is a little less than the area, Abo, in the rest of the bar is illustrated in Figure 13.1.
The tensile force, F, is the same in both, Fa = Fb, regions so
Because ε = ln(AoA), the instantaneous ...