A Matlab Simulink model is presented, where the constitutive equations of piezoelectricity are implemented in a distributed mass scheme. The model comprises two main sub-systems (mechanical and electrical) and their interaction. The electrical part mainly reproduces the basic functions of the driving electronics. As for the mechanical sub-system, the actuator was ideally divided into an arbitrary number of equal elements, connected through springs and dash-pots. The model is able to describe a range of frequencies in the actuator response and allows to calculate the internal stress state during actuation. This is an important parameter for applications because tensile stresses can lead to failure. Experimental data are here reported for a range of commercially available multilayer piezo-actuators and compared to model outputs to show the reliability of the latter