Investigation on compression bruised mechanism of Cyperus esculentus L based on experiment and finite element method

Abstract

Cyperus esculentus L is a newly emerging multi-purpose food, which is also a raw material for drinks or brewing. It is susceptible to mechanical damage during mechanical harvesting, stored and food processing. The compression bruise is an important factor that affects the quality of Cyperus esculentus L. The compression bruise's region will be intruded into by bacteria, resulting in a reduction of food quality. Therefore, it is significant to study the compression bruise mechanism. Its mechanical properties are measured by experiment and applied as a reference to simulation. The macroscopic characteristics of the bruise were observed, and the bruised area was extracted. The experiments were carried out, which the loading displacement, loading speed and moisture content were selected as the factors. It is found that when the loading speed is 20 mm/min, the moisture content is 38 % and the loading displacement is 1.37 mm, the minimum loading force is 94.704 N and the minimum bruised area ratio is 18.924 %. The 3D scanning method was applied to establish the model of Cyperus esculentus L. The results of simulation show when the equivalent strain threshold is 0.10, the relative error is 15.05 % compared with experiment. The changes of equivalent stress, equivalent strain and internal energy are analyzed in the process of compression. The bruised volume and bruised sensitivity are analyzed in the condition of different loading displacements. The bruised sensitivity increases from 8955.24 mm³/mJ to 16814.82 mm³/mJ, when the loading displacement changes from 0.5 mm to 2.0 mm. The bruised sensitivity reduced from 16814.82 mm³/mJ to 13725.42 mm³/mJ, when the loading displacement from 2.0 mm to 2.5 mm.