Piezoelectric strain sensor/actuator rosettes

In-plane anisotropy in the linear piezoelectric constitutive law for [011]_c cut and poled PMN-0.29PT is demonstrated to enable its use as a sensor/actuator rosette. The equations for a 0°/45°/90° rosette are developed using the conditions of coupling between the in-plane strain of the crystal and a substrate, and zero out-of-plane stress on the crystal (plane stress conditions in the crystals). The crystals are bonded to a substrate aluminum plate that is instrumented with strain gages next to the crystals. The plate is subjected to bending about different axes and the resulting electric displacement change of the crystals is monitored. The strain components calculated using the change of electric displacement are compared with the strain components measured using strain gages. This sensor/actuator rosette approach is demonstrated to enable both sensing principal strain components and actuating principal strains in an electronically controllable direction.