Experimental study on corn grain crushing via quasi-static compression method

Grain crushing has been caused lots of wastes sometimes, due mainly to the overloaded force. Corn crushing is particularly prominent to determine the normal operation of the storage and transportation system. Therefore, the basic mechanical data is required to avoid the crushing of grain particles in the machine and process. In this study, 920 mechanical datasets of corn were obtained after compression experiments. The sample group with 95% confidence was determined to fit the corn crushing force using Weibull distribution. The crushing properties of corn were discovered within this sample range. Furthermore, compression experiments of corn were carried out to obtain more accurate mechanical data for the kernel breakage tolerance of corn. Compression direction and compression rate were determined to calculate the maximum resistance crushing force of corn. The crushing force was compared in the three compression directions (length, width and thickness direction). The experimental results showed that the maximum crushing force of corn was obtained when compressing along the thickness direction. The crushing force was obtained to indicate the critical corn resistance to the external forces. Furthermore, the 'quasi-static' concept was introduced into the compression test to avoid the influence of kinetic energy on the mechanical properties under the high loading rate. There was no influence of the compression rate (strain rate, below 0.10 s^-1) on the Weibull distribution of corn crushing force. Therefore, the compression rate of 0.10 s^-1 and thickness direction compression were selected as the experimental condition to improve the test efficiency under the quasi-static compression. The maximum crushing force of corn was then obtained to investigate the effects of moisture content, particle size and corn axial ratio on the crushing force. There was the different distribution of crushing force among corn grains with different moisture contents. Corn grains with a moisture content of 14.72% shared a relatively uniform distribution of crushing force between 150-500 N, compared with the more concentrated distribution of crushing force in the rest moisture levels. The particle size of corn grains was depended on the scale parameter (a) and shape parameter (b) in the Weibull distribution of the corn crushing force. Smaller corn particles exhibited the higher crushing rate. The 100% rate was achieved, when the particle size was below 7 mm. Additionally, the smaller corn kernels exhibited the lower crushing force and less consumption of crushing energy. Compared with the medium-sized corn, the larger kernels were more prone to breakage. The crushing force and energy of particle sizes in the range of 7-9.5 mm exhibited a larger standard deviation, indicating a more discrete distribution of the data. A large axial ratio of corn was that the shape of corn kernels was fuller and rounder. The crushing rate of corn increased with the increase of axial ratio. Corn with large axis ratio was more prone to broken, indicating the lower crushing force and energy consumption. Moreover, the crushing force of corn with a smaller axial ratio shared the larger standard deviation, indicating the higher discreteness with the pressure of corn. The mechanical data and influencing factors on the corn crushing were obtained using compression test and Weibull distribution. The finding can provide the reliable data support to reduce crushing and loss in the process of mechanized processing, transportation and storage of corn.