Finite element analysis of blueberry stack damage
Zhaoqi Zheng, Chen Jing-hui, Wei Tian, Chao Zhang, Zimin An
Abstract
Abstract Blueberries are prone to mechanical damage during the processes of grading, packaging, transportation, and selling, and stack damage is one of the important causes of blueberry quality loss. The mechanical parameters of blueberry should be obtained firstly to create the mechanical model for analyzing the stack problems of multilayer blueberries. Precise mechanical parameters were obtained for the first time by performing a compression experiment and analyzing an explicit dynamics simulation based on the finite element model. It was found that the elastic modulus of the blueberries was 0.225 MPa and that the Poisson's ratio of the blueberries was 0.35. The placement direction of the blueberries had the greatest impact on the rupture force, followed by the number of stacked layers and the loading speed. A regression model was also obtained by considering the influences of the three factors on the rupture force. The rupture force in this research ranged from 3.15 to 7.04 N. The calyx and bottom were the most vulnerable parts of the blueberries. The upper contact part of multilayer blueberries had a greater chance of damage, and the lower contact part was the opposite because the blueberries close to the bottom layer exerted a buffering effect. Moreover, this research demonstrates the importance of applying linear explicit dynamics simulation techniques to agricultural and food products. Practical Applications The main reason for the decreasing market value and quality of blueberries is damage occurring between the point of harvesting and consumption. The damage caused by stack is one of the important factors in this process. This article accurately determined the mechanical parameters of blueberries. On this basis, the important factors that cause blueberry stack damage were further studied. Taking the rupture force as a measure, empirical models for rupture susceptibility were described. This article not only provides ideas for how to reduce blueberry stack damage and to extend blueberry shelf life but also provides a theoretical basis for research on the mechanical structure and mechanized processing of blueberries.