Effects of variety and moisture content on mechanical properties of millet grain group

Abstract: In order to clarify the rheological mechanical properties of millet grain group during mechanical harvesting and processing, this paper studied the effects of different varieties and different moisture contents on the creep characteristics of millet grain group. In this experiment, different varieties (Jingu 21, Zhangza 10), and different moisture contents (12.10%, 16.05%, 20.00%) of millet grain group were selected as creep experimental factors. The creep characteristics (instantaneous elastic modulus, delayed elastic modulus, relaxation time and viscosity coefficient) of millet seed group were used as experimental indicators, and one-way analysis of variance and multi-factor analysis of variance were performed. Based on the original contents of millet seed group, the target moisture contents of the millet grain group were formulated to be 12.10%, 16.05%, 20.00%. The experiment was conducted on the CMT-6104 universal testing machine, and the special fixture for testing the creep characteristics of millet grain group was designed. Combining the Burgers model, nonlinear programming method was used to optimize search regression parameters, and creep parameters of millet grain group were obtained. The creep curve of millet grain group of different varieties showed that, as time going on, the amount of deformation caused by creep tended to be constant, which reaching the strain saturation. There were differences in the millet grain group creep characteristic curves of the different varieties. The significance test standard was 0.05, and the variance analysis was performed. The results showed that the creep characteristics of millet grain group could be described by the four-element Burgers model, and the creep parameters of millet grain group with different moisture content and different varieties were different. The variety had a significant effect on the delayed elastic modulus of the millet grain group. The delayed elastic modulus of the Jingu 21 millet grain group was higher than that of Zhangza 10. The moisture content had significant effects on the instantaneous elastic modulus, delayed elastic modulus and viscosity coefficient of the millet grain group, which was decreasing while the moisture increasing. The instantaneous elastic modulus of the millet grain group with the water content of 12.10% was significantly higher than the water content of 16.05% and 20.00%. The delayed elastic modulus of the millet grain group with the moisture content of 12.10% was significantly higher than the water content of 20.00%. The instantaneous elastic modulus and the delayed elastic modulus represented elasticity and hardness of the millet grain group, respectively. With the increasing of the moisture content of the millet grain group, the instantaneous elastic modulus and the delayed elastic modulus of millet grain group decreased, resulting in a high increasing of the creep curve. The strain in the screw conveyor of combine harvester was correspondingly larger. In this paper, the creep properties of millet grain group with different varieties and different moisture contents were studied experimentally, which provided theoretical support for low-loss harvesting, processing and storage and parameter optimization of millet. There are many factors affecting the mechanical properties of the material, in addition to the influence of moisture contents and varieties, it is also related to many factors such as temperature, internal molecular structure and chemical composition of the material, et al. The rheological properties of agricultural materials need to be further studied in conjunction with the principles of life sciences.