Simulation and experimental research on fruit branch pruning process based on ANSYS/LS-DYNA

Objective  The goal was to in depth study the pruning process characteristics and cutting mechanism of fruit branches, and provide a reference for optimizing the core cutting components of pruning machines and improving the cutting performance of electric pruning machines.

Method  Taking the branch of ‘Shixia’variety of longan as the test object, ANSYS/LS-DYNA was used to perform finite element simulation of the branch cutting process. We built a branch cutting test platform for cutting experiments, verified the accuracy of the simulation model, used a high-speed camera to observe the branch cutting process, analyzed the stress distribution and cutting mechanism of moving blades, branches, and fixed blades in the cutting process, and determined the area where the maximum equivalent stress occured.

Result  The cutting process of actual test and simulation test could be divided into five stages including the extrusion stage, cutting-in shearing stage, stable shearing stage, shearing stage and branch vibration stage. The actual cutting force was slightly higher than the simulation value. The maximum relative error between the actual value and the simulation value of the peak cutting force of the cutter for cutting 10, 15 and 20 mm diameter branches was 7.8%, and the average relative error was 7.0%. The trends of the experimental and simulated cutting force curves were roughly the same. During the cutting process, the maximum equivalent stresses of the moving blade, branch and fixed knife appeared near the cutting edge, branch and fixed knife cut. The maximum equivalent stresses of the moving blade and fixed knife were both less than the yield limits of the tool materials, and the tools would not fail.

Conclusion  The finite element model is basically consistent with the actual situation and has certain reference value for the design and improvement of pruning machine.