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The branch impact failure mechanism has gradually received attention from scholars, along with the application of impact cutting methods in plantation forest pruning. In this paper, the impact cutting failure mechanism of Populus tomentosa branches was mainly studied. The impact cutting process of branches was simulated by using Finite Element Method (FEM)-based explicit dynamics. The stress change and deformation characteristics in the branch failure process were studied. A theoretical model of branch impact cutting mechanism with branch diameter, cutting clearance, and branch angle as the main factors was proposed. The model describes the branch cutting damage process and the changing characteristics of cutting force. A branch failure state equation was proposed to describe the branch impact cutting failure patterns. The forest experiment was conducted to validate the branch impact cutting mechanism and the branch failure state equation. This work fills a vacancy of relevant theory and provides a theoretical basis for the future development of forestry and agricultural equipment using impact cutting.

As the main forest firefighting equipment, portable wind extinguisher plays a major role in forest and grassland firefighting. The same as other hand-held vibration machines, portable wind extinguisher inevitably causes hand-transmitted vibration which is an important cause of discomfort for operators, decreased work efficiency, and even health hazards. In this paper, a biomechanical response model of hand-transmitted vibration is established based on the operating posture of the wind fire extinguisher. A standard vibration test platform was set up for the test, and the model parameters were identified through the standard vibration test data. The vibration response predicted by the model is compared with the measured response of portable wind extinguisher to verify the feasibility of the model prediction. The vibration response of the standard vibration experiment platform was used to compare the influence of hand force on the hand-transmitted vibration response. The results show that the goodness of fit between the vibration transmissibility response predicted by the arm model and the response measured by the standard vibration test platform is between 75% and 92%, and the goodness of fit between the vibration transmissibility response predicted by the arm model and the response measured by the portable wind fire machine is within the range of 77%. The research in this article can provides theory and data basis for improvement of vibration reduction protection strategy and device of portable pneumatic extinguisher.

Standing tree pruning in fast-growing forests is an essential part of the targeted nurturing of quality fast-growing forests. Because of the high risk and low efficiency of traditional pruning methods, a climbing and pruning robot was developed, its design was optimized, and related experimental research was carried out. This paper describes the design scheme of the Monkeybot mechanical structure and control system and theoretically analyzes the clamping mechanism, walking mechanism, cutting mechanism, and obstacle avoidance mechanism to determine the critical design parameters. On the premise of ensuring a good pruning effect, Ansys Workbench Gui Explicit Dynamics was used for the cutting simulation experiment. The test adopts a three-factor and three-level orthogonal test method to explore the best design parameter combination when reducing the maximum shear stress on branches. A forest work performance evaluation was carried out using prototypes designed with the best variety of parameters. The forest test results show that the Monkeybot could prune trees with a diameter at breast height of 10~20 cm, the average operation time for pruning a tree was less than 30 s, the winter pruning effect was ideal, the maximum climbing height could reach 7.18 m, and the maximum pruning diameter could reach 2.79 cm. The development of the machine can provide equipment support for the research of fast-growing forest standing tree pruning and nurturing technology.