| The load spectrum of components can provide data support for the design of components.Due to the lack of load spectrum,the fatigue damage of components under cyclic load was seldom considered in the design of rotary tiller.The rotary tiller work load test system was designed to test the rotary tiller work load in this paper,the load spectrum have been compiled based on the actual test work load foundation.So we can provide the theory data for the rotary tiller design.The main research contents are as follows:(1)Analysis of load and determination of patch position.According to the particularity of the practical working condition of rotary tiller,the strain test method was adopted to reflect the working load of rotary tiller through the torque load on the universal joint.The ANSYS Workbench finite element analysis software was used to conduct a simulation analysis of the forces on the universal joint,and it was determined that the position of the strain gauge sticking was 0-67mm away from the universal joint power input end,and the direction was±45°along the axis direction of the universal joint.(2)Load test device design.According to the theory of torque measurement signal transmission problem,based on the STM32 microcontroller,developed a high sampling rate,high transmission rate of the wireless torque test equipment,including sensor module,power module,signal conditioning module and wireless data transmission module,and based on the Keil software,the software program of the test equipment,including the system main program,the A/D conversion subroutine,wireless data sending subroutine,etc.,and the real-time test data can be displayed on the PC through the serial port assistant.(3)Rotary tiller working load test.The sensor was calibrated using the parallel resistance calibration method,and the relationship between the torque and the output voltage of the bridge which isM(28)6.7025×U_o-88.296,the output voltage range corresponding to the input torque within the range of 0-1326 N·m was 13.000-211.000 mv.The designed test system was used to carry out field load measurement under different working conditions.According to the change of tillage depth in the working process of rotary tiller,the test area is divided into acceleration area,stabilization area and deceleration area.The communication state of the system is stable and the data efficiency is 99.05%.(4)Compiling the working load spectrum of the rotary tiller.Take out the load data of the stable working area and extract the effective data of the load data;According to the calibration results,the amplitude threshold method is used to extract the load data within the calibration range,and the operating torque range in the stable region is between514.929-1185.179 N·m.The torque load data of the same tillage depth and different tillage speed were combined,the data of the stable working area were converted into the corresponding shear stress value according to the formulat(28)M W,and the peak and valley values after being taken out were counted and counted by rain-flow counting method,and the load spectrum under the corresponding tillage depth was compiled.Through the analysis of load spectrum,the following conclusions can be drawn:when the tillage depth was 16 cm,the amplitude frequency was the highest in the mean value 27.96MPa group,which occurred 5545 times,accounting for 37.52%of the total frequency;When the tillage depth was 10 cm,the amplitude frequency was the highest in the mean value group of 23.49MPa,which occurred 9574 times,accounting for 67.34% of the total frequency.After the mean value was unified,it was found that the mean load was 864 N·m when the tillage depth was 16cm,and 784 N·m when the tillage depth was 10cm. |
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