基于准静态压缩方法的玉米粒破碎试验

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

    • 摘要: 为减少粮食因破碎而导致的损耗浪费,探索玉米颗粒的抗破碎能力,该研究利用准静态压缩试验共获得了920组玉米粒的力学特性数据,并通过韦伯分布拟合对玉米粒破碎力进行了分析。试验对比压缩方位及压缩速率对玉米粒破碎力的影响,确定准静态压缩的试验条件,在此基础上探索玉米含水率、粒径、轴比对玉米粒破碎性质的影响。结果表明:沿玉米厚度方向压缩可获得玉米粒的最大破碎力;压缩速率小于0.10 s−1时,压缩速率对玉米粒破碎力分布无影响。另外,玉米粒的含水率、粒径、轴比均影响其破碎力分布。含水率14.72%的玉米粒破碎力的韦伯分布尺度参数a最大,表明其破碎力分布更为集中;小粒径玉米粒更容易破碎,粒径小于7 mm时玉米粒破碎率达100%;玉米粒破碎率和破碎力均与轴比呈反比,表明饱满圆润的玉米颗粒更容易发生破碎。该试验可为玉米在储运、加工过程中的降碎降损提供可靠的数据支撑。

       

      Abstract: 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.

       

    /

    返回文章
    返回