A research team led by Professor Xu Daochun from the College of Technology at Beijing Forestry University has published groundbreaking findings on walnut vibration harvesting mechanisms in the top-tier journal in agricultural engineering Biosystems Engineering , which boasts a five-year average impact factor of 5.2. The study, titled "Fracture Type and Excitation and Detachment Forces of Chinese Walnuts under Dynamic Conditions in Vibration Harvesting", systematically reveals the mechanical properties of walnut stem detachment during vibrational harvesting. This discovery offers critical theoretical support for optimizing the design of intelligent harvesting equipment. The research outcomes are expected to enhance the harvesting efficiency of specialty economic forest crops in China and drive innovation in forestry mechanization technologies.

Vibration harvesting is a highly effective method for the large-scale mechanised harvesting of walnuts. However, theoretical analysis and study of the detachment force and fracture type under dynamic conditions is lacking in the current research on walnut detachment during vibration harvesting. Here, a theoretical model of walnut motion under applied vibration is established to obtain the relationship between the excitation force and the response frequency and amplitude. A stress analysis of the Chinese walnut fruit is then carried out to determine the fracture type. Dynameter and field harvesting experiments were conducted to verify the theoretical analysis and make further explorations. The results demonstrate the correctness of the formula for calculating the excitation force and verify that the fracture type of walnuts under vibration harvesting is bending fracture. The proposed fracture zone index β is found to be between 0.235 and 0.385. Moreover, using a novel video extraction method, the walnut fruit detachment force was determined to range from approximately 6.2 to 8.4 N. These results provide a reference for choosing vibration parameters and calculating the excitation force.

Diagram of the motion of the fruit–stalk system in a half cycle when fracture occurs

Liu Changyi from the School of Technology is the first author of the paper and Professor Xu Daochun is the corresponding author.This work was supported by the National Key Research and Development Program of China (2019YFD1002401).

Paper link: https://doi.org/10.1016/j.biosystemseng.2024.12.005

Written by Liu Changyi, Xu Daochun
Translated and edited by Song He
Reviewed by Yu Yangyang