Finite element modeling of the biomechanical properties of Populus tomentosa branches and analysis of pruning mechanisms

The finite element method can effectively simulate the pruning process to investigate the pruning mechanism. To ensure the reliability of the simulation results, it is essential to measure and calibrate the model parameters. In this study, a finite element model was established to simulate the pruning process executed by pruning robots. The biomechanical properties of Populus tomentosa branches were determined using mechanical tests. The finite element model parameters were calibrated using the Plackett-Burman and Box-Behnken methods, and the reliability of these calibrated parameters was subsequently validated through field testing in a forest environment. Finally, the calibrated finite element model was used to investigate the impact-cutting pruning mechanism of Populus tomentosa branches to further solve the problems of poor pruning quality and serious blade wear caused by unreasonable working parameters of the blade in the pruning process. The results indicate that the calibrated finite element model of the biomechanical properties of Populus tomentosa branches accurately simulates the pruning process. Moreover, the simulation results show that reducing the cutting speed and increasing the blade wedge angle led to a decrease in the peak stress and thus blade wear while increasing the cutting speed and reducing the blade wedge angle led to an improvement in the pruning quality. At cutting speeds of more than 6 m∙s⁻¹ and with a blade wedge angle of less than 35°, branches with a diameter of 25 mm were cut with a cutting share of nearly 100 %. This study provides a robust model for the simulation and optimization of impact-cutting pruning by robots, which is of considerable significance for the development of high-quality products in the enhancement of forestry pruning practices.