Dynamic finite element simulation of the collision behavior and multi-parameter quantitative characterization of the damage degree of banana fruit in the post-harvest operations

Squeezing, collision, friction and other behaviors are widely present in the post-harvest processing operations of bananas, such as field picking, de-handing, cleaning, packaging and transportation, which will inevitably cause a certain degree of mechanical damage to banana fruits. In view of the difficulty in accurately detecting and quantifying fruit damage in the early stage of production, this paper adopted dynamic finite element numerical simulation and multi-parameter optimization of response surface to carry out simulation analysis on the collision behavior of banana fruit in the post-harvest operations, and the accurate assessment and quantitative characterization of fruit damage degree and erosion rule were carried out. The three-dimensional solid model of banana was established by reverse engineering method based on 3D scanning technology. The multi-scale finite element model of banana was further established by combining the constitutive parameters of banana bunch obtained from quasi-static mechanical experiments. In this study, a total of 27 collision systems including different contact materials, collision angles and impact speeds were developed to quantitatively characterize the changing rules of contact force, equivalent stress, energy, damage volume and bruise susceptibility of fruit under different experimental scenarios. An empirical prediction model for banana fruit’s bruise susceptibility was established using response surface optimization methodology, and the comprehensive effects of contact material, collision angle and impact speed on fruit damage were obtained. On this basis, three dynamic collision systems including banana hand and impact panel were developed, and the generation region and erosion rule of equivalent stress of banana hand and impact panel under different encounter postures were further investigated. Finally, the physical verification experiments of banana impact and collision were carried out based on the characteristics of banana growth distribution and movement in the actual post-harvest operations. The experimental results showed that the prediction models of bruising susceptibility of banana fruit under different scenarios achieved a prediction accuracy of more than 80 %. The residual stress inside the banana hand under Posture_3 is the smallest (2.55e-2 MPa), and the maximum relative error between the predicted value and the experimental value of bruising susceptibility is less than 8.5 %. These results indicate that the multi-scale dynamic finite element model and the empirical prediction model of collision system for bananas are reasonable and correct, and the study have certain reference value for the numerical simulation and quantitative characterization of damage degree of other fruits and vegetables.