Study On The Torsional Effect Of Piezoelectric Quartz Disc And Manufacture Of A New-type Torque Sensor

Since Curie brothers discovered piezoelectricity of quartz crystal in 1880, the research on piezoelectric effect is always the key subject of the foundation theory of piezoelectricity and the science of smart material. Because of the technology development and engineering practical requirement, at present the piezoelectric theory has already place emphasis from on the two dimension effect based on stress analysis, namely the longitudinal effect, transverse effect and shear effect to on the three dimension effect based on deformation analysis, such as the extending effect, compressing effect, bending effect, torsional effect, but the piezoelectric theory based on deformation analysis has not yet established. Supported by the Doctor Subject Foundation of the Ministry of Education of China under Grant No. 98014106 and by the National Science Foundation under Grant No. 60374043, by using the knowledge of different interdisciplines such as Piezoelectricity, Physics of Dielectrics, Physics of Crystals, Theory of anisotropic Elasticity and the Maxwell electromagnetic theory the piezoelectric torsional effect of quartz disc is investigated in this paper, and then the integral research method of piezoelectric torsional effect is first obtained. Based on the torsion effect a new torque is successfully manufactured.Firstly, the complicated stress distribution of an Y0°-cut piezoelectric quartz disc under torsion is first investigated by utilizing the torsion theory of anisotropic elasticity, and then through the Maxwell electromagnetic theory and piezoelectricity the distribution of bound volume and surface charge densities is computed. By Finite Element method the distribution of nonlinear polarized electric field in the quartz disc is simulated. The results of calculation and simulation indicate that the bound charge density on the surface perpendicular to the mechanical axis is nonhomogeneous and antisymmetric with respect to the electric axis. Therefore to effectively dispose detection electrodes to measure the electric result of torsional effect, the partitioned electrode method, rather than usual single electrode method must be adopted, and the Charge method, not general Voltage method is used to connect the output of all electrodes. The theoretical and experimental results show that the piezoelectric torsional effect is existed in quartz disc and the charge measured is linear with the torque.Secondly, on the basis of investigation of the torsional effect of quartz disc, the key dimensions of the torque sensor based on torsional effect are designed by Finite Element Method, and then a new-type piezoelectric torque sensor is successfully manufactured. The outstanding feature of the torque sensor contrary to other type of quartz torque sensor is that it adopts torsion effect of quartz disc, rather than shear effect. Only three Y0°-cut discs are used in the torsion quartz measuring cell, which can avoid or reduce the cross talk of an axial and arbitrary radial force, and at the same time improve sensitivity. The calibration results shows that it has high static linearity, and its natural frequency is greater than 12 kilohertz, so the torque sensor has full reached the dynamometer standard stipulated by CIRP-STCC. The new torque sensor has applied for Chinese Invention Patent.Finally, in order to measure the torque of drilling, the orthogonal experiment method in which the three factors are the diameter of drill, feed and spindle speed is performed. According to Analysis of Variance, it is suggested that the diameter of drill is the moresignificant than feed, and than cutting speed. Through Multiple Linear Regression, the experiential expression of torque during drilling 45 steel is obtained. Hereby it proves that the performance of the new-type torque sensor reach the practical requirements which can be used in practical measurement.