关键词: 山核桃, 破壳试验, 离散单元法, 裂纹研究

Abstract: Using experimental and simulation studies, the laws of crack generation and development in hickory under impact are investigated. The experiment was mainly to use the omnipotent testing machine to carry out the impact shell breaking test and conduct 15 repeated tests for three different heights on the nut in the long axis, oblique direction, and short‑axis loading direction respectively. The test results show that, regardless of the loading direction, the maximum value of the shell breaking impact force is around 240 N. The force is smaller as it gets closer to the horizontal axis and larger as it approaches the long axis. Taking this as a starting point, the lateral cross‑section of the nut is simplified to a circular shape, and the hickory discrete element model is constructed by adding a strong binding force model based on the conventional elastoplastic element contact model. Simulation results show that the horizontal indenter pressed at a constant speed could caused the symmetry crack of the hickory model; at the same time, the vertical indenter could cracked the hickory model in the form of S-shaped blocks. The process of hickory nut cracking was captured using a high‑speed camera, which is consistent with the simulation results.This study provides an important reference for the design, optimization and in‑depth understanding of the mechanism of the Chinese hickory cracking machinery.

Key words:  walnut, shell breaking test, discrete element method, crack research