Authors

Abstract

Accurately determining the angle of repose for irregular and dispersed agricultural grain materials requires a simulation model that effectively represents the actual grain shapes and utilizes numerical methods to analyze their stacking behavior. This study focuses on "Yongyou 15" rice grains, employing 3D raster scanning technology to obtain precise contour data. Through a reverse modeling process, a detailed 3D geometric model of the grains was developed, resulting in a discrete element model comprising 618 grains of varying diameters, created using granular polymer theory. Discrete element analysis software (EDEM) was integrated with MATLAB image processing to simulate the falling and stacking process of the rice grains within a stainless steel bottomless cylindrical tube. The contour of the grain heap was analyzed using linear fitting, followed by a micro-mechanical investigation of the grain heap structure. The analysis indicated that the pressure depression within the heap is caused by the oblique transmission of contact forces. The simulated angle of repose under experimental conditions was 31.29°±0.41°, differing by only 0.81% from the actual measured angle of 31.04°±0.21° obtained through physical stacking experiments. These results demonstrate that combining numerical simulations with image feature extraction is a reliable and efficient method for assessing the stacking properties of agricultural materials.

Abstract in Chinese

为了准确确定不规则、分散的农业物料籽粒的休止角，需要建立与真实物料形状高度相似的籽粒仿真模型，并采用数值方法对物料的堆积特性进行仿真研究。本研究以“甬尤15号”水稻籽粒材料为例，利用三维光栅扫描技术获取籽粒的轮廓数据，采用逆向建模过程生成籽粒的三维几何模型，基于颗粒-聚合物理论建立由618个不等径颗粒组成的水稻籽粒离散元模型。利用离散元分析软件EDEM和MATLAB图形图像处理技术，模拟了水稻籽粒在不锈钢无底圆柱形管中落料和堆积过程，并对堆积图像轮廓采取线性拟合，同时对籽粒堆微观力学结构进行研究，得到籽粒堆压力凹陷的原因，来自籽粒堆内部接触力的斜向传递特征。模拟试验条件得到休止角为 31.29°±0.41°，与实际堆积试验休止角31.04°±0.21°对比，偏差为0.81%。结果表明，数值模拟结合图像特征提取的方法对测量农业物料堆积特性有效可行。