“嘎拉”苹果跌落损伤脆值及损伤边界研究(英)

对于果实产品,通常其作业、运输过程中的主要机械破坏形式为跌落冲击引起的产品局部损伤,而非直接发生破裂.作为传统跌落冲击脆值与破损边界理论的延伸,提出了跌落损伤脆值与跌落损伤边界的新概念以及相应的工程定义.考虑到传统产品脆值与破损边界曲线试验方法的局限性,提出了测定获取果实跌落冲击损伤脆值与跌落损伤边界曲线的技术过程与方法.以嘎拉苹果为研究对象,设计多组不同高度对嘎拉苹果进行自由跌落刚性冲击试验.在测试获得冲击力一时间数据的基础上,通过理论分析计算,得到加速度一时间、变形量一时间等动态关系曲线,获得了嘎拉苹果跌落损伤脆值;构造了嘎拉苹果跌落损伤边界曲线.结果表明,跌落损伤边界曲线与传统产品跌落破损边界曲线存在较大差异.对应果实产品,即使速度很小,只要产品瞬时加速度达到一定值,也将产生冲击损伤:对应不同的损伤率,构造了相应多条损伤边界曲线.提出的概念及研究结果为控制果实类产品的跌落损伤、合理地进行缓冲包装设计提供了新的理论基础.

Dropping bruise fragilities and bruise boundaries of 'Gala' apples

The major mechanical damages of fruit are usually not direct split but local bruise caused by dropping impact during harvesting, sorting, packaging, and transportation. It is necessary to develop engineering approaches to control the fruit's local bruise volume and bruise ratio. As an extension of traditional product fragility and damage boundary, the concept of dropping bruise fragility and bruise boundary was developed and the definition of them was presented in this paper. In view of the limitations for traditional testing methods, the method and procedure for determining dropping bruise fragility and bruise boundary were also established by adopting flee-fall dropping tests. The flee-fall dropping impact tests with a series of drop heights were conducted on flesh 'Gala' apples. The dropping bruise fragilities and bruise boundaries of 'Gala' apples at different bruise ratios were determined by means of test results and theoretical analysis. The results showed that there were obvious differences between dropping bruise boundary and traditional damage boundary of products. Even if the velocity approached zero,the 'Gala' apple could be bruised as long as acceleration of it exceeds a certain value. Moreover, a series of dropping bruise fi'agilities and dropping bruise boundaries of the 'Gala' apple were established corresponding to its bruise ratios.