Time-varying compressive mechanical characteristics and empirical model construction of loquat (Eriobotrya japonica Lindl.) based on FEM-RSM

Abstract

Loquats (Eriobotrya japonica Lindl.) comprise peel, flesh, and kernel and are commonly used in the food, pharmaceutical, and light industrial fields. The compression issue involves multiple stages from harvesting to postharvest, and understanding the mechanical response of loquats during transient compression processes is crucial for controlling mechanical damage. This study analyzed the route of stress transmission and the evolution of characteristics during compression processes. Comprehensive empirical models for mechanical damage and empirical models with constraint conditions were established to adapt to different mechanical research and development conditions. A three-dimensional model of a loquat was constructed using reverse engineering methods, and a finite element model comprising three parts, namely, peel, flesh, and kernel, was established. The accuracy of the model under compression conditions was validated (maximum error of 6.46 %). Compression mechanical characteristics were compared using four contact materials (aluminum alloy, PVC, ceramics, and rubber), four forces (5, 10, 15, and 20 N), and four angles (0°, 20°, 40°, and 60°). During the compression process, stress concentration occurred at the junction between the flesh and kernel of the loquat. Compared with the other three materials, rubber exhibited a lower equivalent compressive stress on the loquat. The equivalent compressive stress on the loquat was the lowest at a compression angle of 20°. An empirical model considering the interaction between force and angle was developed, along with the empirical models under single-constraint conditions. This study provides insights into the mechanical characteristics of fruit compression caused by harvesting methods and offers solutions for the optimization design of harvesting machinery.