NUMERICAL/EXPERIMENTAL CHARACTERIZATION OF A PIEZOELECTRIC DRIVEN ELECTROMEDICAL DEVICE

The present work refers to the numerical/experimental characterisation of an electromedical device, based on piezo actuator technologies, used for dermacosmetic applications. Special focus was given to the fatigue related problems that have arisen during the operational life of the device, and which are related to the high frequency dynamic loads to which the device itself is subjected. Preliminary studies have indicated a recursive crack faults that characterize, the slim extremities of the devices (bar); previous test, also put in evidence, that the crack location generally lies along an operational deflection mode nodal line. To better understand the physical phenomena at the basis of this circumstance and to design specific solutions to overcome this problem, a set of numerical and experimental activities have been planned and performed. The set of activities may be summarised as follow: FEM modelling of the bar devices and extraction of eigen-frequencies and modes FEM modelling of forced response to the piezoelectric excitation and the calculation of fatigue parameters Experimental vibrational analysis by the use of scanning laser technique; operational mode shapes extraction. It should be noted that the use of the laser technique has permitted the identification of the high frequency modes and has avoided problems which could arise with accelerometers due to their dimensions, mass loading effects and limited frequency response. The results of this program have shown good agreement between the experimental and numerical values and have identified also the significant influence of the boundary conditions on the life on the bar. The study has also identified some possible solutions including the modification of the material, change of shape, or the use of a different soldering technology [1] [2].