Research on the piezoelectric torsional effect of a rectangular quartz disc and a novel drilling dynamometer

The theoretical foundation of a new-type drilling dynamometer (i.e. the torsional effect of a rectangular piezoelectric quartz disc), the structure design and calibration of the drilling dynamometer are investigated in this paper. By using the theory of anisotropic elasticity and the Maxwell electromagnetism, the torsion stress and the distribution of surface charge densities of a rectangular quartz disc are calculated. According to the theoretical analyses of the bound charge densities, the detection electrodes are effectively disposed on the surface of the piezoelectric disc. The experimental results show that the torsional effect exists in the rectangular quartz disc and the bound charges are linear with the torque applied. Based on the torsional effect, a new type of drilling dynamometer is designed, in which only four quartz discs are used. The axial force measuring cell consists of two X0°-Cut quartz discs, and by the partitioned electrode method only two Y0°-Cut quartz discs can simultaneously sense the radial force and torque. After static calibrations, the torque sensor has full reached the dynamometer standard stipulated by CIRP-STCC. Undoubtedly the drilling dynamometer will provide a new method for measuring the drilling force and monitoring the drilling process.