Due to the large particle size and short crushing process of mineral sizers, and the main breaking mechanism is tensile and shear failure, it is difficult to determine the load size and distribution during the design. In this paper, a new strength analysis method based on discrete element (DEM) and finite element (FEM) is proposed to analyze mineral sizers roll tooth strength. By applying distributed loads, the authenticity and accuracy of roll tooth strength calculation are improved. The distributed load was calculated by discrete element software EDEM. In this paper, considering the size effect of material strength, uniaxial compression test and Brazilian disc test were carried out on materials with different size, respectively. The compressive and tensile strengths of materials were calibrated, and the bonding parameters in discrete element simulation were finally determined. By analyzing the discrete element simulation results, the distributed load on the roll teeth when the force on the roll teeth is maximum is selected and loaded to the FEM model of the roll teeth at the corresponding working position at the corresponding time in ANSYS environment for strength analysis. The results show that the roller tooth load is mainly distributed at the back of the tooth at the maximum loading time, and there is stress concentration at the front of the tooth root.
In recent years, with the development of particle model, contact model and other mathematical models, the discrete element method has been widely and deeply used in the mineral sizers. Legendre et al. iI used EDEM software to simulate single particle crushing of jaw crusher and verified the results of energy consumption optimization. Cleary et al. "21" proposed a discrete element replacement model calculation algorithm based on falling weight test before material modeling, and used discrete element simulation technology to study the effects of material characteristics and environmental parameters on the working performance of cone crusher. Discrete element method (DEM) and Finite element method (FEM) are increasingly used to analyze the interaction between loose or brittle materials and other continuum. For example, In the performance analysis of crusher, screen machine and other equipment, the mechanical and kinemical properties of materials and the impact of materials on equipment are studied. In this regard, the discrete element software EDEM developed a coupling channel with the finite element software ANSYS Workbench, which can realize the unidirectional coupling between the discrete element and the finite element. It is suitable for the situation that the deformation of the equipment is not large, and it is not enough to affect the mechanical and kinematic characteristics of the material.
Roller tooth strength is an important basis for tooth profile design and optimization. The traditional method of analyzing the strength of roller teeth takes the maximum crushing strength of material as the compressive stress value to load on the tip and back of the roller teeth. In this paper, DEM FEM is used to analyze the strength of mineral sizers roll teeth. According to the actual production conditions of a certain mineral sizers, a DEM-FEM model was established. In EDEM, mineral sizers' crushing process was simulated and the load information of roll teeth was extracted. The finite element model of the roll tooth was established in ANSYS Workbench, and the load information of the roll tooth was loaded on the roll tooth using the EDEM-ANSYS Workbench coupling channel, and the strength analysis of the roll tooth was completed.
In this paper, the material discrete element model and the finite element model of the roll teeth are established according to the interaction between the roll teeth and the broken material as shown in Figure 1(a). mineral sizers have the screening function. Large particle size materials will be broken by grading. Small particle size materials that can pass directly through the gap between the teeth rolls will not be broken. Therefore, in this paper, hexahedral bonding model is established for large particle size materials and single particle model is established for small particle size materials. Figure 1(b) shows the particle bonding model of the material and the FEM model of the roll teeth, wherein the roll teeth rotate counterclockwise.
In the particle bonding model, the discrete elements with overlapping contact radii bond, and there are bonding forces and torques between the bonding elements. The bonding force and moment are determined by displacement. FIG. 2 shows the bonding diagram of particles i and j, in which displacement is mainly represented by the relationship between speed and time. Where, Fn and F are normal force and tangential force respectively; Tm and T are normal and tangential moments respectively; A is the contact area, after A=π; J is the moment of inertia, J=0.5π, m is the bonding radius; S. And S are normal and tangential stiffness respectively; Is the time step; And 4 are normal and tangential velocity respectively; And are normal and tangential angular velocities respectively. When the normal and tangential stresses between particles are greater than the set values, the bonding relationship of discrete elements is damaged [, as shown in Equation (2) : x<E+2 engineering A(2)-F A This model can only be used between two particles, and the contact radius should be larger than the particle radius. The coupling process of DEM and FEM can be briefly summarized as: (1) DEM was used to simulate the crushing process and calculate the force acting on the surface mesh of the roll tooth model; (2) DEM and FEM were coupled to load the force to the finite element model of the roll tooth; (3) mineral sizers strength analysis of the roll tooth with FEM. Based on this method, EDEM-ANSYS Workbench software coupled with mineral sizers was used to analyze the strength of roll teeth and calculate the stress distribution and displacement deformation of roll teeth under normal crushing conditions.