“…Suppose that the body is composed of a homogeneous, isotropic, incompressible elastic , All tensor and vector components are taken with respect to the fixed rectangular coordinate system previously chosen. Greek and Latin subscripts have the respective ranges (1,2) and (1,2,3), repeated subscripts are summed, and a subscript preceded by a comma indicates partial differentiation with respect to the corresponding x-coordinate. material characterized by an elastic potential I¢ representing the strain.energy density per unit undeformed volume.…”