Research On Multidimensional Load Sharing Structure And Arrangement Of Piezoelectric Dynamometer

With the development of testing technology, a growing number of industrial productions need the participation of sensors to complete production process monitoring. Due to the continuous improvement of production levels, new and higher requirements of sensors are put forward for some specific applications. For example, in the process of friction stir welding, the force on the top of the welding is often more than 10KN, and the welding position changes simultaneously. So in order to feedback and control real-time welding process and achieve a wide range of welding force of partial load measurement, the accurate measurement of external force in different positions has become the key point; on the other hand the welding plane size is very large, while the workpiece tend to be thin, so insufficient stiffness become another problem to solve.Starting from the requirements of the above applications, treating the piezoelectric quartz sensor as the core sensing element in this paper, a dynamometer with load sharing functions is designed, realizing precise measurement of multidimensional, heavy and position-changed force.In order to achieve the load-distribution measurement of heavy force, this paper first describes the axial and transverse load-distribution principle of sensor, designs the excavate ring type load sharing structure and notch-type load sharing structure, by comparing the simulation maximum deformation and practical processing feasibility. Notch-type load sharing structure is finally determined. On the basis of using square form of sensor layout, to solve the difficulties of test plane stiffness small, load-sharing structure is designed in the sensor range according to the four square arrangement. The upper and lower plate of dynamometer with 30mm、60mm、90mm three different span of load sharing structure is designed. The elastic method and preload are determined, then designing positioning pin used in assembly to ensure the accuracy of assembly. Finally, a description of assembly process is illustrated in detail.The simulation analysis of axial and transverse load is carried out on the dynamometer by using ANSYS Workbench, and the axial and transverse load tests are conducted on the dynamometer. By comparing the output of the three kinds of load-sharing structure span curve’s quadratic term coefficient, load-sharing ratio and the biggest difference of sensor output when load point in different positions, there are about 40% deviation when doing the axial test and 10% deviation when doing the transverse test. Through convex platform the contact accuracy of dynamometer is improved, and do axial and transverse load test on the improved dynamometer, but the results still exist great deviations. Finally making the sensor output curve as a calibration curve, the differences between the sensors’ outputs is calculated with different load points. As for the dynamometer outputs’nonlinear problem, the method of sensor outputs proportional calculation (SOPC) is proposed. This method is used to calculate the unknown external load, and the axial and transverse error can be controlled within 1%, achieving the target of ideal measurement.