| SAG is the short form of Semi-autogenous Grind and is one of the most important primarygrinding equipments in modern mining plant. In order to increase the production efficiencyand bring further profits to the enterprise, the diameter of SAG is increasing gradually. Forcrashing and grinding the mine the rotator which can take the ores, grinding balls and slurryto rotate together is the important part of SAG including cylinder, feed end cover anddischarge end cover. Under the long term, heavy load and low speed operating condition,lots of cylinders show cracks in the weld lines before they reach fatigue life. For studying onthe reasons lead to the cracks, the SAG is tested by using finite element tech in this thesis.Firstly, the paper sketches out the evolution of autogenous and semi-autogenous technology.On the base of domestic and international papers and thesises, in the marketing area, forChina the biggest SAG is manufactured by CITIC Heavy Industries Company Ltd foundedin1956, the size of SAG is11m×5.4m,11m is the diameter. However, in the world thebiggest SAG is manufactured by ThyssenKrupp Polysius, the length of diameter reaches to13.4m. In the researching area, from the papers and thesises we learned that, compared todomestic research institute, foreign researchers are familiar with using Discrete ElementMethod to study the rotation activity of ores, grinding balls and slurry in the rotators. Thereare lots of papers with respect to DEM in the international papers. But there is few researchbased on DEM to study SAG in China. In the second chapter, this paper explains the externaland internal structure of SAG, lean on schematic diagram in detail. Also the operatingprinciple of SAG is stated at the same time. And a integration SAG grinding circuit systemwas presented according to the advanced foreign circuit picture. In the chapter3,4,5,6,mainly on the basis of the parameters of one large-scale SAG, using the Equivalent densitymethod to calculate the load of this SAG under three kinds of working conditions including full-load static condition, normal operation condition and launching condition. After theloading calculation, solid modeling of rotator of SAG is made by using ANSYS software andmeantime load and constraint were applied on the solid modeling. When the preprocessor isfinished, calculate the stress and displacement of cylinder, feed end cover and discharge endcover under the three condition, meanwhile analysed the five order modal of one SAG,verified the design scheme of SAG is reasonable. On the other hand, in this paper an originalworking condition named impacting working condition is founded. In this special workingcondition, the impact between grinding balls and cylinder is considered. In order to get theaccurate the results, the location and velocity of the grinding balls at the impacting momentmust be confirmed. After the location and velocity are done, ANSYS software can figure outthe value of impacting force which will be applied as load on the solid model under ANSYSenvironment. As a result, the stress calculated by ANSYS is greater than the yield limit ofmaterial of rotator and than weld strength. Theoretically the impacting working condition ismain cause of the serious deformation of rotator and cracks on weld lines. After draw theconclusion of analysis, some rational proposal is presented to alleviate serious deformationand cracking problems. At the end of this paper, a prospect of SAG is made from fiveaspects. |
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