Five Definitions of Strain for Large Deformations

Snapshot 1: 1% tensile deformation; note that all five strains have almost identical values

Snapshot 2: 90% tensile deformation; note the differences between the five strains

Snapshot 3: 1% compressive deformation; note that all five strains have almost identical values

Snapshot 4: 50% compressive deformation; note the differences between the five strains

Snapshot 5: 90% compressive deformation.; note the large differences between the five strains

This Demonstration depicts the relationship between strain defined in five different ways and the percent deformation of specimens subjected to uniaxial tension and compression. The percent deformation is selected with a slider and the corresponding strain values are displayed numerically and as moving dots on curves. Also shown is the ratio, , between the length of the stretched or compressed specimen, and , where is the initial length and the absolute deformation in length units. The strain definitions are: Cauchy's strain, , Hencky's, , Green's, , Swainger's, , and Almansi's, . Each strain is plotted versus the percent deformation, , as a colored curve along which the dots move.

References:

M. Reiner, "Phenomenological Macrorheology," Rheology, Theory and Application, F. R. Eirich, ed., New York: Academic Press, 1956 pp. 9–62.

M. G. Sharma, "Theories of Phenomenological Viscoelasticity Underlying Mechanical Testing," Testing of Polymers: Vol. 1, J. V. Schmitz, ed., New York: Interscience Publishers, 1965 pp. 147–199.