Experimental Study On Resistance Characteristics Exerted On A Moving Object In Granular Materials

In fields of bio-pharmaceuticals,chemical engineering,agriculture and geophysics,mechanical equipment often encounters a large number of discrete particles during operations.The interaction of granular materials and the equipment will directly affect the work efficiency,operating performance and service life of the device.Among these,the resistance characteristics exerted objects in granular materials are extremely important for the shape design,performance optimization and service life prediction of the industrial equipment.And the magnitude and evolution characteristics of the resistance are closely related to the dynamic state of the surrounding particulate media.At present,there is relatively few research work in this area,and there is no unified and clear understanding of the mechanism of resistance and the scale relationship with the motion state of objects.Based on an annular rheometer and a self-designed experimental platform for particle oblique impact,this paper attempts to analyze the dynamic behavior of an object moving in granular materials from rotation and impact.We try to analyze the generation mechanism and establish the corresponding resistance scale rate in different situations.The main work is as followings.Firstly,based on an annular rheometer,we measure the evolution characteristics of the resistance exerted on the disk-shaped rotor during rotation in granular materials from the transient to the stable process.Based on two different particle materials,the influence of the buried depth of the disk rotor on the torque experienced by the disk in the steady state stage is analyzed.We have established a scaling law between torque and depth of embedding.Finally,the influence of the variation of granular materials properties on the proposed scaling law is discussed.Secondly,we study the influence of rotor speed on the magnitude and evolution characteristics of the resistance.In glass materials,we establish the dependence between the resistance of the rotor in granular materials and the rotation speed.And the logarithmic scaling obtained is basically consistent with other existing similar experimental results.The experimental results of different particle sizes and different buried depths verify the universality of the scaling law.Finally,based on experiments with different sizes of rotors at different buried depths in plastic granular materials,we have found that the rules between the resistance and rotation speed are qualitatively opposite to those in glass beads;On this basis,the scale between the resistance and its speed of a rotor in plastic granular materials is established.Thirdly,the experimental platform for particle oblique impact is set up,and we mainly study the resistance characteristics of granular materials to impact particles under the condition that the impact particles are embedded in granular materials.The experimental results of vertical impact of impact particles verify the reliability of the experimental device and data processing method.On this basis,the scale relationship between impact particles and impact energy are obtained by measuring the embedding depth of impact particles at different impact speeds and impact angles.We establish a corresponding averaged force phenomenological model.At the same time,the force circumstance of the particles is reversed by tracking the trajectory of the impact particles with a high-speed camera.The dependence of resistance on impact velocity and impact depth is discussed,and the resistance model exerted on impact particles in granular materials is set up.In this paper,the experimental study of the resistance characteristics exerted on moving objects in granular materials is carried out based on the two forms of rotation and impact.We obtain the scale relationship between the resistance and feature of movement and position under steady-state and transient conditions,and preliminary analyze the mechanism and evolution characteristics of resistance in a granular medium.The development of these basic researches not only reveals the dynamic behavior of objects moving in granular materials,but also has important implications for practical issues concerning discrete granular materials in the fields of chemical engineering,agriculture,medicine,and geotechnical engineering.