Papers by Keyword: Discrete Element Method (DEM)

Abstract: As the movement condition of the material in crushers and crushing process is very complex, it is hard to measure and observation directly or indirectly. It helps a lot for analyzing of the raw material and crusher interaction, optimizing design crusher, analyzing of the law crushing to analyze the crushing process of the material in the crushers. Therefore, the article explores the use of PFC^3D program to simulate the process of cone crushers crushing the material. It analyses the feasibility of using PFC^3D program to simulate the crushing process. It does the kinematics simulation of the material crushing in cone crusher. The data in the paper can provide certain reference in designing new and more efficient crusher.

Abstract: Discrete element softwares that have been reported at home and abroad, normally calculate with fixed mechanical models. As the development of discrete element theory, users need more different mechanical models. Based on the three dimensional discrete element software developed by our team independently, mechanical model dynamic loading module has been added, which enables the software to meet the needs for different demands, and provides convenience for further development of wider range of applications.

Abstract: The biaxial test on ballastless track subgrade material of surface layer and bottom layer of subgrade was established using the particle flow code(PFC). Based on the micro parameter gotten from the biaxial test, a two-dimensional discrete element model of slab Ballastless Track subgrade is modeled. The dynamic response under dynamic load was calculated. A comparison of simulation results and the field measured data shows goodness of fit which provides a new way of simulation on dynamic response of high speed railway subgrade.

Abstract: The design method research of position schemes for particle dampers applied to a flywheel under sinusoidal excitation has been investigated, in which discrete element method (DEM) and finite element analysis are used to study the relationship between the damping capacity of dampers filled with different metal particles and the dimensionless acceleration amplitude, and the specific parameter of radial position is introduced to discuss the influence on particle damping caused by different dampers attachment locations. A series of corresponding experimental investigation are conducted subsequently and the results indicate an auxiliary position scheme if the acceleration response of optimum location exceeds the threshold. It can be concluded that with the help of the specific parameter of radial position, the experiment results can be well explained, in addition, the design efficiency and accuracy will be raised, especially in the condition that the particles mass is strictly limited.

Abstract: Ballast-glue is a chemical material severed to adjust ballast stiffness and stabilize railway infrastructure, and its ballast-glue characteristics is less of microscopic research. The ballast-glue cubic sample compressed tests were carried, with curing time alteration, then a 3D discrete-element method (DEM) is used to investigate the glue bonding effects of the tests, where the ballast is made of real size irregular clumps, the ballast-glue is represented by bonds to simulate the tensile and shear strength, results show that ballast curing time is a key factor to govern the ballast-glue integrity and strength, ballast-glue increases the maximum compressed force up to 0.99Mpa, and the DEM bonding function is a potential tool for ballast-glue structure investigation.

Abstract: Detailed knowledge of particle-scale energy allocation behavior under the influence of particle breakage is of fundamental importance to the development of micromechanics-based constitutive models of sands. This paper reports original results of the energy input/dissipation of an idealized crushable soil using 3D DEM simulations. Particle breakage is modeled as the disintegration of synthetic agglomerate particles which are made up of parallel-bonded elementary spheres. Simulation results show that the initial specimen density and crushability strongly affect the energy allocation of the soil both at small and large strains. The major role of particle breakage, which itself only dissipates a negligible amount of input energy, is found to advance the soil fabric change and promote the interparticle friction dissipation. Particularly, at small strains, particle breakage disrupts the strain energy buildup and thus reduces the mobilized shear strength and dilatancy of a granular soil. At large strains where particle breakage is greatly reduced, a steady energy dissipation by interparticle friction and mechanical damping is observed. Furthermore, it is found that shear bands develop in most dense crushable specimens at large strains, but they are only weakly correlated to the anisotropy of the accumulated friction dissipation.

Abstract: For studying the working performance of the cutting header, the paper puts forward using DEM to study its dynamic breaking process when it is for cutting coal rock. The model of cutting header and the model of the two-dimensional DEM simulation analysis are set up separately. By applying reasonable mechanical model into coal rock particles and the cutting header, DEM simulation analysis of its cutting process is carried out. Such analysis is taken at different cutting speed. Then, the way of selecting working parameters is got. It preliminarily proves the feasibility of using DEM to analyze the working procedure of the cutting header and it provides a new research method for its optimization design.

Abstract: Subsoiling, as an important mode of conservation tillage, can break plowpan and increase permeability and water retention ability of soil which increase the crop yield. Subsoiler, as a key component of subsoiling, significantly effects on the tillage resistance. Reduction of working resistance of subsoiler can decrease output power of tractor and then further reduce the cost of subsoiling operation. The existing subsoilers have problem of overlarge subsoiling resistance. The conventional methods to resolve such problem include optimal design of the structural parameters of subsoiler and application of oscillation subsoiling device, but those methods not only make the structure of subsoiler more complex, but also increase the cost of agricultural production. Based on biomimetics principles, the upper surface outline of the claw of the house mouse (mus musculus), which has exponential function curve feature, was applied to the structural design of cutting soil edge of subsoiler shaft. Accordingly, the bionic subsoiler which has exponential function curve feature was designed and manufactured. The comparative experiments were conducted using the two types of subsoilers which have exponential function curve shape and parabola type in tillage depth at 300mm and 350mm with the forward velocitys of 0.5m/s and 1.0m/s in the indoor soil bin. The horizontal tillage resistances of the two types of subsoilers were measured using remote-measuring system of agricultural machinery dynamic parameters under different experimental conditions. The results showed that the horizontal tillage resistances increased with the increase of tillage depth and forward velocity. The horizontal tillage resistances of bionic anti-drag subsoiler (BAS) were obviously less than those of parabola type subsoiler (PTS) under same experimental conditions and the reduction was in the range of 8.5-38.2%. It indicated that the cutting soil edge of shaft with exponential function curve structure has remarkable anti-drag property. The simulations of tillage processes of the two types of subsoilers were conducted using discrete element method (DEM), the stress fields and velocity fields were obtained under different simulation conditions. The results showed that the directions of stress fields and velocity fields of the two types of subsoilers have forward and upward variation trend, but the directionality of contact stress of PTS was nonuniform compared with BAS, and such results lead to an increase in soil disturbance. The intensities of stress field and velocity field of BAS were obviously less than those of PTS under same experimental conditions, The results of simulation were consistent with the results of tillage experiments, indicating that the bionic subsoiler with exponential function curve feature has significant anti-drag property. The exponential function curve can be applied to the structural design of cutting soil edge of subsoiler aiming to reduce tillage resistance.

Abstract: Soil is one of the important mediators in the agricultural production and its particle is a discontinuous, heterogeneity and nonlinear natural geological substance. It is difficult to analyze the soil cutting process by using traditional methods. According to the discrete nature of the agricultural soils, discrete element method based on the discontinuity assumptions can be an alternative to analyze the changes under external forces in the soil cutting process. This article describes the basic principles, its applications and its prospects of the discrete element method, especially in the field of soil cutting.

Abstract: Grinding test was carried out to study the grinding of granite with single diamond grain. Forces were measured to investigate the mean normal and tangential forces acted on the diamond grain. The relationship between the forces and either spindle speed or the maximum thickness of the undeformed chip produced by a diamond grain was discussed. The digital models of granite were constructed by discrete element method. Based on the model, two-dimensional and 3-D analysis was carried out to simulate the grinding process with the single diamond grain. The simulation results were compared with experimental data, and some useful conclusions were obtained: the 3-D results agree well with the experiment data at the sameand largeas well as the sameand large; the 3-D and 2-D results are comparable to the experiment data at other machining parameters..