The effective length of a piezoelectric cylindrical specimen in strain measurements is determined by considering the stress decay in a cylindrically anisotropic, circular cylinders of piezoelectric materials subjected to 2D surface tractions and prescribed end loads. On the basis of the state space formalism, the problem is studied by means of matrix algebra. The significance of the end effects is evaluated through a characteristic decay length. The study enables us to assess Saint-Venant's principle as applied to piezoelectricity in general and to determine the effective lengths of tensile and torsional specimens of piezoelectric materials in particular.
