Papers by Keyword: Discrete Element Method (DEM)

Abstract: Usually, the screw is placed in rotary kiln for calcination of selenium dioxide, so that the materials can be evenly conveyed in the rotary kiln. Through the software of Solid Edge, the geometric model could be established. The materials in the cylinder were regarded as the discrete particles. Then geometric model was imported into the EDEM and the particles movement simulation has been done. Without considering the floating of the screw in the cylinder, linear rotation speed of the cylinder and screw could be set. Through the simulation and analysis, the relative particles movement charts can be obtained. It provides certain reference value to the rotary kiln designing and the research of particles' axial movement in rotary kiln.

Abstract: Since a long time of excavation, the slope in Yang-mountain of Suzhou Province became a high and steep slope which has 260m difference in height, on top of this slope there is a high risky cataclastic texture bedrock landslide. Based on geologic investigation of the landslide, combined with 3DEC numerical simulation, the paper gave a comprehensive analysis on formation precondition, evolution procedure, failure model and mechanism from the points of topographic feature, structure evolution history, lithology and external influence. It is shown that the free face in front of the landslide, weak quartz porphyry dike in front of the sliding zone, cataclastic rock structure formed by nappe structure are the main factors which control the formation and failure mode of the landslide.

Abstract: Compared with the closed screw conveyor, the discharging performance of open-type screw structure has a certain degree of uncertainty. The design of open-type screw structure is firstly presented in this paper. A novel open-type screw discharging structure is developed on the base of the requirement of industry, and structural parameters and operation parameters of screw are given. Based on the discrete element method, the simulation model of spiral discharging performance is built. The influence of the angular velocity of on open-type screw discharging performance is discussed. The analysis results show that the angular velocity of screw has a great influence on the discharge performance in the condition that other parameters remain unchanged. The presented method has an important guiding role and theoretical reference value to design of open-type screw discharging structure.

Abstract: One of the important objectives of lunar exploration is to obtain the lunar soil samples. However, the sampling process is very different from that on the Earth due to special characteristics of the lunar soil and surface environment. In order to ensure that the lunar exploration and sampling are successful, large numbers of ground experiments and computer simulations must be taken. In this paper, the surface lunar soil excavation simulation is investigated by three-dimensional discrete element method (DEM). It is implemented based on the open source LIGGGHTS, which takes the lunar soil as spherical particles. The interaction between the excavation tool and lunar soil is demonstrated. The excavation force and torque have also been calculated in real time. Moreover, the comparison of the excavation in different environments between the Earth and Moon corresponding to their different gravity accelerations was done. This paper shows that three-dimensional discrete element method can be used for the surface lunar soil excavation simulation and can provide important reference results for actual operations.

Abstract: The bonded particle model (BPM) of granite for pre-stressed machining is build by using the discrete element method (DEM). This model can not only descript the intergranular fracture behavior but also the transgranular fracture behavior of the granite. The processes of crack propagation under different pre-stressed machining conditions are studied by means of DEM simulation. Damages and cracks of surface/subsurface are also observed. The simulation results show that, while the magnitude of pre-stress is controlled in a certatin range, the number of radial cracks reduce as the increasing of pre-stress magnitude, contray to the transverse cracks. It could be seen that maching damage is decreased and surface quality is improved by applying the pre-stressed machining method, and the discrete element method is an effective way to simulate the machining process of granite.

Abstract: In order to solve the technical problem of gob-side entry retaining in inclined coal seam, combined with the practical mining conditions in a certain mine, this paper adopts the discrete element method, applies numerical simulation to analyze inclined coal seam gob-side entry retaining with three different supporting ways, and studies surrounding rock deformation characteristics of gob-side entry retaining. The research results show that the filling body upper boundary for right side can control the roadway surrounding rock deformation better compared with the boundary is used as the hypotenuse; Meanwhile, the pressure of surrounding rock of coal seam gob-side entry retaining is mainly from the impact of the immediate roof natural fall of the upper goaf tilt and the weight of caving coal gangue and coal seam of immediate roof above; According to the surrounding rock deformation characteristics of coal seam remain gateway along goaf, it is determined to use combined supporting method of concrete filling in roadway sides and anchor wire rope supporting inside the roadways, providing the design basis of gob-side entry retaining in coal seam for the similar geological conditions.

Abstract: A selected material, polystyrene microsphere series, is created as a building block of two-dimensional (2D) aggregates to examine scaling behaviors of the compressive stress condition. The 2D aggregated clusters are confined between the two cantilevers of 30 micron in diameter. These cantilevers can slide and force the aggregates move in the lateral direction. The compressive yield stress is directly measured during experiments by quantitative image analysis on the optical microscope. Locations of polystyrene aggregates are traced by Discrete Element Method (DEM), computer simulation. The 2D mechanical properties are examined for the particle size scaling behaviors as a function of particle area fraction and the average particle coordination number. The larger the particle size, the greater the modulus and the yield stress.

Abstract: Rotary kilns are widely used in metallurgical industry. By using the software of Solid Edge, the geometric model could be established. Then the model was imported into the discrete element simulation software of EDEM 2.4. Material in the rotary kiln was regarded as particles. Regardless of the floating of the screw in the cylinder, the rotation speed of cylinder and screw could be set. By the "grid bin group" option of the "analyst" module, the simulation model was divided into sections. Finally the relative particles motion charts and particles distribution could be obtained and analyzed. Comparing with the traditional physical prototype testing method, it is more economic and efficient. It has a certain reference value to the study of the particles movement in the rotary kiln.

Abstract: Particle damping is a method for improving damping of a dynamic system by means of energy dissipation due to repeated collisions of a free mass on the base structure. In this paper, the theoretical investigations carried out to study and characterize damping with respect to the level of base excitation. The mathematical model consists of a particle damping system. The response obtained from the mathematical model for the drum brake and paticle damper. Here the effect of particle damping is studied for low frequency and high amplitude excitation. Optimum parameters are determined for design of impact damper based on the mathematical model. A good match is obtained by theoretical results.

Abstract: Ballast degradation and unrecoverable deformation are emerged on the railway ballast track under the loads of high-speed and heavy loading locomotive. With the change of tamping frequency, a better understanding of the physics of compactness degree is important for long-time stability of ballast. This paper presented a numerical investigation of the bulk materials dynamics and the transient impaction of a system of irregular polyhedral particles confined with a rectangular box with a retaining wall subjected to cyclic tamping loading. Sphere packing method was being used in this study to simulate typical full-sized ballast particles. This paper aimed to establish firm-soft coupling particle-flow tamping operation simulation numerical model based on contact dynamics theory. This study checked the validity of the model while different tamping working conditions and out-loads was being implemented. The study shows that discrete element method (DEM) is an efficient method to reveal the rearrangement rule of railway ballast after the process of tamping operation.