A New Calibration Method for Dynamically Loaded Transducers and Its Application to Cavitation Impact Measurement

Abstract

The erosion produced by cavitation is a serious problem in hydraulic machinery. During investigations of the dynamic loading generated by collapsing cavitation on a surface, a dynamic pressure transducer was developed. The piezoelectric polymer PVDF (Polyvinylidene fluoride) was used as the pressure sensitive material. A novel method of dynamic calibration has also been developed. The transducer is loaded through pencil lead by a beam supported at its other end on a knife edge and loaded at the center by weights. As the static load is increased, the pencil lead breaks and the load is released suddenly. The unloading time is faster than for any other conventional calibration method and is of the same order as cavitation loading. Descriptions of the developments of both the calibration method and the transducer are given. The principal advantages of the new method are the short pulse duration and the simplicity of the test procedure. The paper is an extension of the previously reported work by Momma and Lichtarowicz (1994), giving further information on the operating characteristics of the transducer in comparison with the traditional ball-dropping method.