Mechanical compression characteristics of rapeseed based on continuous damage theory

In the process of mechanised sowing and harvesting, the damage and fragmentation of rapeseed are often caused by multiple contacts. The expansion of micro-defects and the accumulation of fusion damage in rapeseed can lead to fragmentation. To explore the law of mechanical damage of rapeseed, an elastoplastic model was established by Hertz con-tact mechanics. Combined with the continuous damage theory, the evolution equation of compression damage was established, and the accumulation method of compression damage was clarified. Three kinds of commercial seeds were taken as the experiment material. A single compression crushing test was carried out to verify the correctness of the elastoplastic model but multiple compression crushing tests were carried out to explore the damage accumulation process and method. The results show that the elas-toplastic model can better fit the relationship between force and deformation during compression. The critical damage deformation dd is equal to critical elastoplastic defor-mation ds. When the deformation is more significant than 15 +/- 2% of the diameter, the plastic deformation of rapeseed occurs. When the deformation is < dd, the rapeseed will not be broken during the 30 cycles of equal displacement compression. When the deformation is > dd, the damage leads to the decrease of the effective elastic modulus. With the increase of the compression deformation, the damage to the rapeseed intensified, resulting in the rapeseed being more easily broken. The research can provide a theoretical basis for designing structure and parameters in mechanised sowing and harvesting for rape.(c) 2022 Published by Elsevier Ltd on behalf of IAgrE.