Mineral sizers break the material in three stages. In the first and third stages, the material is broken by cutting and sizzling the tooth tips. The load of the roll teeth increases with the increase of the cutting depth. When the cutting depth reaches a certain degree, the local stress of the material will exceed its maximum crushing strength, and then the material will have local forward separation. With the occurrence of the collapse, the load of the roll teeth will drop sharply. Figure clearly shows the relationship between the load of the roller teeth and the action time. The second stage is broken by the relative action of the back of the teeth to cut the material, in addition to the role of the force is different, the load change of the rod teeth is very similar. In addition, mineral sizers have the function of forced discharge, so the extreme situation that the tooth roll is suddenly stuck by non-crushing foreign matter may occur, and the kinetic energy of the tooth roll will be almost completely absorbed by the roll teeth. In summary, it can be considered that the typical load conditions of the roller teeth are as follows.
In the first and third stage crushing conditions, in the first and third stage crushing process, the material is broken by cutting and tearing of the tooth tip. Therefore, in this condition, there is a uniform pressure p along the cutting surface of the lift.
P-0mix(1) p·s·rm,(2), where σmx is the maximum crushing strength of the broken material: m, is the rated torque of the tooth roll, r is the rotation radius of the tooth tip, s is the maximum cross-section area of the tooth tip into the material.
2 Mineral sizers finite element analysis of roll teeth
2.1 After proper simplification of the finite element analysis model, stif85 in ansys element library is selected for analysis because the shape of the roll teeth designed by our company is extremely irregular. The tip of the tooth is the loading part, and it is properly encrypted when dividing the grid. The finite element model is composed of 349 elements and 437 nodes.
2.2 Restraining parents
The tooth cap is fastened on the tooth ring by a tension bolt. In order to simulate the actual situation, the three line displacements of the tooth cap near the joint of the bolt position are limited in the finite element analysis. In this way, on the one hand, it conforms to the actual situation, and on the other hand, it can also be used to check the bolt strength with the constraint reaction of the analysis result.
2.3 Analysis results by calculating on apolo-dn580, the stress distributions of mineral sizers roll teeth under three working conditions were obtained
(1) Under working conditions 1 and 3, the maximum stress point occurs at a certain depth from the tip of the tooth and near the top of the tooth surface. This is an inevitable result of the asymmetric design of the top of the tooth. In addition, the stress value of the arc transition at the root of the tooth tip is also larger than that in the adjacent area, which indicates that the tooth tip is not only subjected to pressure, but also to bending moment in 1,3 working conditions.
(2) Under working condition 2, the maximum stress point occurs at a certain depth from the back of the tooth and near the tip of the tooth. The stress value of the inner two corners of the tooth is also significantly higher than that of the adjacent areas, which is the result of tension at the inner corner.
(3) It can be seen from table 1 that the stress condition under the stuck condition is much worse than that under other conditions. The calculated maximum equivalent stress under this condition is 840mpa, while the yield strength of the material is 883mpa. Therefore, the strength of the teeth can still meet the requirements when the tooth rolls are suddenly locked.