Study On White Crushing Mechanism Of Brown Rice

Rice is the staple food for two-thirds of China's population.The annual per capita consumption of rice is about 140 kilograms,with a total consumption of nearly 200 million tons.The output of rice ranks first in the world in successive years.However,due to the lack of research on the mechanism of rice crushing,there is no theoretical guidance for processing parameters,which causes serious waste in the process of rice processing in China.The existence of cracks in rice itself is an important reason for the breakdown of rice grains.It is important to study the mechanism of crack formation and propagation in paddy for paddy processing.In this paper,starting from the mechanical mechanics of brown rice,the generation and propagation of cracks in the micro-state of brown rice are observed and analyzed directly by scanning electron microscopy,and the generation and propagation of cracks are studied by means of fractal theory.Finally,the stress of brown rice in the process of processing is discussed by means of discrete element simulation.The main research contents and conclusions are as follows:Three varieties of brown rice were dried by texture analyzer at different time to obtain test samples with different moisture content.Compression,shear and three-point bending tests were carried out with self-designed fixture.The results showed that the compressive force of brown rice grain was greater than the shear force of grain and the three-point bending force of grain at the same moisture content.Compression work of brown rice grain is greater than shear work and three-point bending work.Compressive elastic modulus of brown rice grain is larger than shear modulus of shear force and shear modulus of three-point bending force.When the moisture content is different,the mechanical properties of brown rice samples with low moisture content are larger than those of brown rice grains with high moisture content under the same application mode.The stress crack initiation and propagation of brown rice under different moisture content and different application modes were observed by scanning electron microscopy.This paper mainly observes and analyses the damage of the internal structure of brown rice and theform of stress crack formation and propagation when brown rice is subjected to external force.Through observation and analysis,it is found that the form of stress crack generation and propagation basically conforms to that of brittle materials,and to some extent conforms to the self-similarity of fractal theory,which provides a feasible theoretical basis for subsequent theoretical analysis.On the basis of image analysis and fractal geometry in fractal theory,the mechanism of stress crack generation and propagation is analyzed statically and dynamically.Crack propagation models in different forms are established,including intergranular fracture model,transgranular fracture model,intergranular and intergranular coupling fracture model and bifurcation model.Fractal dimensions of different fractal models and critical crack propagation force are calculated respectively.At the same time,the dynamic analysis of the crack shows that the length of the crack,the speed of the crack formation and the bending angle of the crack propagation have an effect on the intensity factor of the crack formation and propagation.The process of brown rice whitening was simulated by EDEM discrete element analysis software.By changing the working speed and clearance of the equipment,it was found that the movement speed of brown rice particles changed obviously while the resultant force changed slightly when the parameters of the equipment were changed.In addition,it is found that the crushing of brown rice is the main reason for the crushing.By changing the working parameters,the extrusion force on brown rice can be effectively reduced.