自适应荔枝果去核力学仿真与性能试验

Comparison on Mechanical Simulation and Performance Testing for Adaptive Litchi Pitting

摘要:

去核是制取荔枝灯笼果肉的必备工序，但荔枝核径多变，机械化高效成功去核困难。为解决这一难题，通过测定荔枝果物理性能，设计了一种自适应去核的刀具和机构；并基于LS-DYNA动力学仿真和台架试验，量化了荔枝3种转速去核过程等效应力和切削应力的时空变化规律；比较了变核径荔枝果不同转速自适应去核成功率和果肉损失率，评价了综合去核效果。仿真结果确定了转速对荔枝果等效应力分布与切削应力极值的影响，且仿真试验与台架试验结果基本一致。随着转速增加，荔枝果最大等效应力与最大切削应力均下降，变核径荔枝果自适应去核成功率提升。3种转速中，292 r/min去核综合效果最优，其去核成功率和果肉损失率分别为100%和22.4%。

Abstract:

Pitting is an essential step for producing litchi lantern flesh, while the variable pit size poses a challenge for efficient and successful mechanical pitting. To solve this problem, an adaptive pitting tool and mechanism was designed by measuring the physical properties of litchi fruit, and the spatiotemporal changes of equivalent stress and cutting stress during the pitting process of litchi at three different rotational speeds were investigated, based on the LS-DYNA dynamic simulation and bench tests. Furthermore, it quantified and compared the success rates and pulp loss rates of adaptive pitting for litchi fruit with variable pit sizes at different rotational speeds, and evaluated the overall pitting performance. Lychee fruit and kernel sphericity coefficients of 0.95 and 0.74 were obtained, and their three-dimensional radial dimensions showed normal distributions. The simulation results indicated the effects of rotational speed on the distribution of effective stress and the extreme values of cutting stress in litchi fruit was consistent with the bench test results. As rotational speed increased, both the maximum equivalent stress and maximum cutting stress in the litchi were decreased, leading to improved success rates for adaptive pitting of litchi with variable pit size. Among the three tested rotation speeds (feed with speeds of 100 mm/min and 20 mm depth), pitting at 292 r/min demonstrated the best overall pitting performance, with a 100% success rate and a pulp loss rate of 22.4%, respectively. The revealed adaptive pitting mechanism were significant for developing high-quality and efficient pitting devices for stone fruits, including but not limited to litchi.