The expansion of a shell node leads to a set of nodes lying on a straight line. Therefore, the stretch tensor 
![]() is reduced to the stretch along this line. Let
 is reduced to the stretch along this line. Let 
![]() be a unit vector parallel to the expansion and
 be a unit vector parallel to the expansion and 
![]() and
 and 
![]() unit vectors such that
 unit vectors such that 
![]() and
 and 
![]() . Then
. Then 
![]() can be written as:
 can be written as:
leading to one stretch parameter ![]() . Since the stretch along
. Since the stretch along 
![]() and
 and 
![]() is immaterial, Equation (105) can also be replaced by
 is immaterial, Equation (105) can also be replaced by 
| (106) | 
representing an isotropic expansion. Equation (104) can now be replaced by
|  | ||
| (107) | 
Consequently, a knot resulting from a shell expansion is characterized by 3 translational degrees of freedom, 3 rotational degrees of freedom and 1 stretch degree of freedom.