C. Sgarra et M. Vianello, DIRECTIONS OF COAXIALITY BETWEEN PURE STRAIN AND STRESS IN LINEAR ELASTICITY, Journal of elasticity, 46(3), 1997, pp. 263-265
For a linear anisotropic hyperelastic body subjected to a state of pur
e strain it is shown that there are at least three directions such tha
t the stress and strain tensors are coaxial.