3.7 (b) Definition of Strain

Previous:  3.7 Infinitesimal Deformation

Let  deformation gradient  , then

If is orthogonal, then , then i.e. no change in length

Thus rigid body rotation does not produce any change in length.

Consider

 If    is small compared to  then

 where   infinitesimal strain tensor

Next:  3.8  Geometrical Meaning of E_ij