Dovstam added frequency dependent complex terms to
Dovstam added frequency dependent complex terms to this statement to account for material damping.  Cauchy generalized this statement to an arbitrary body and constructed two six-dimensional vectors related either by the compliance matrix or its inverse, the stiffness matrix.  This law approximates the relationship between stress and strain, and the point at which this law fails to hold approximates the Elastic Limit.  FTP, name this relationship usually formulated for the force applied to, and resultant deformation of, massless springs, mathematically given as F equals negative k x.
Dovstam added frequency dependent complex terms to this statement to account for material damping.  
{Hooke}'s law