Explicit dynamics simulation study to determine the damage patterns of apples (Red Fuji) under impact loading

Collisions between apples and mechanical structures are inevitable during the harvest of fresh-market fruit. Even moderate impacts can lead to internal damage, significantly affecting the shelf life and quality of the fruit. In recent years, technologies such as spatial frequency domain imaging and structured light reflection imaging have made progress in early damage detection. However, considering both economic feasibility and practical applicability, there remains a need to explore accurate and quantitative methods for damage assessment. To address this issue, this study constructed a 3D model of ‘Red Fuji’ apples through physical experiments and reverse engineering. Explicit dynamic simulations based on the finite element method were conducted to evaluate the mechanical damage under various impact conditions. A total of 125 simulation scenarios were designed by combining five impact heights, five impact angles, and five contact materials. Key data and visual representations of stress evolution were obtained from the simulations. Results indicated that the highest damage susceptibility occurred when apples impacted steel at a height of 20 cm and an angle of 135°, while the lowest damage susceptibility was observed when impacting polyvinyl chloride at a height of 15 cm and an angle of 90°. Furthermore, a response surface methodology was employed to analyze the quantitative values of damage susceptibility. The maximum discrepancies between experimental and simulated results in terms of damage depth, area, and volume were 0.90 cm, 2.94 cm², and 11.85 cm³, respectively. The prediction error of damage susceptibility ranged from 0.883 to 11.3 %. The consistency of the damage patterns further validates that the finite element model can effectively simulate apple damage under specific impact scenarios. This study provides insights for reducing mechanical damage during harvesting.