苹果跌落冲击力学特性研究

果品跌落冲击力学特性的研究是表征其流变性能、跌落损伤机理以及设计作业件的基础。构建果实自由跌落冲击力学参数测试系统，对“富士”苹果进行不同高度的单次自由跌落、同一部位的多次跌落试验。在测试获得冲击力－时间数据的基础上，基于运动学原理进行理论分析计算，得到加速度－时间、冲击力－变形量、应力－应变以及跌落冲击弹性恢复系数等动态关系。研究结果表明随着跌落高度、跌落次数的增加，苹果冲击力、加速度峰值、冲击最大变形、冲击结束后的残余变形逐渐增大。苹果跌落弹性恢复系数随着跌落高度而逐渐降低，随着跌落次数增加而逐渐增大。跌落次数对跌落变形量增加的影响不显著，随着跌落次数的增加残余变形变化很小。

Dropping impact mechanical characteristics of apple

In the process of sorting, packaging and transportation, the produce is submitted to impact which cause it's bruising. A testing system was developed to determine the mechanical parameters of produce during dropping impact. Two dropping impact tests were conducted on fresh 'Fuji' apples grown in Shandong, China. The one was dropping test at five heights of 15, 30, 45, 60, 75 cm. Another one was repeated impact test of the same point of the objects' surface at the same height. Based on the data of impact force versus time obtained from tests, the curves for acceleration versus time, deformation versus time, impact force versus deformation, stress versus strain and coefficients of restitution were obtained by theoretical analysis. Results show that with the increase of dropping height and repeated impact, the impact force, peak acceleration, maximum deformation and remaining deformation of apple increase. The impact resilience coefficients of restitution of apple reduce with the increase of dropping height, but increase with the increase of repeated impact. The influence of repeated impact on deformation of apple is not notable.