Development of a rotation transducer based on bimorph PZT's

Rotational degrees of freedom are basic to solve substructuring and structural modification problems. While they are included in finite element models, the common experimental tests do not provide these quantities, because of the difficulty of their measurement. In this paper, the possibility of using low-cost PZT transducers to estimate rotational quantities is considered. Reference is made to bimorph patches that are able to measure the local curvature of a structure. From this curvature, rotation can be obtained either by integration or by interpolation. PZTs are convenient due to their low cost and, generally, minimum test structure intrusiveness. However, different drawbacks must be overcome: first, an appropriate assembly of the sensor on the structure is necessary to obtain reliable results. Second, a problem of cross-sensitivity must be solved, especially for measurements on plates. Third, a calibration procedure must be devised, since such PZTs do not have a calibration card. Some comparisons of rotational FRFs obtained from PZTs and other standard techniques are presented that show a very good agreement and indicate that their use can be very convenient.