Mechanical Analysis And Structural Optimization Of Large Three-Row Roller Slewing Ring

As the main bearing of shield,the three-row roller slewing ring is used to connect the cutter system and the power system of a shield machine.It is a typical oversized rolling bearing with low speed and heavy load.The main bearing of the shield machine is subjected to huge force and moment during the working process.Its performance and life have a significant impact on the excavation of a shield.Therefore,it is necessary to design a three-row roller slewing ring which can meet the working requirements of the shield.In this thesis,based on the mechanical analysis of the three-row roller slewing ring,the parameters and roller generatrix modification were optimized.The main research contents are as follows:Based on the analysis of the structure and load characteristics for a three-row roller slewing ring,the mechanics analysis of each row of rollers was conducted respectively.The calculation formula of load distribution region and static equilibrium conditions were used to analyze the load borne by each roller of the main roller,secondary roller and radial roller under the central axial force,overturning moment and radial force.According to the mechanical analysis and structural characteristics of the three-row roller slewing ring,the optimization model was established.The constraint conditions were the design requirements of static load,the design requirements of roller quantity,etc.The objective functions were the longest basic rating life and the smallest total volume,etc.Taking an actual working condition of a three-row roller slewing ring bearing as an example,a parameter feasible region of the main roller structure was determined according to the optimization model.Its life was 21488.02 hours by using the life calculation theory of slewing bearing life.The distribution of load on the roller is related to the roller generatrix.By analyzing the advantages and disadvantages of various modified curves,the logarithmic curve was selected as the modified curve.In order to make it more suitable for heavy and eccentric loads,an external load coefficient representing the end modification amount was added on the basis of the logarithmic curve.The maximum stress value unmodified roller and rollers with different external load coefficients were calculated by finite element method,and the curve with the smallest stress value as the modification curve was selected for the generatrix of the roller.The stress value of logarithmic curve was minimum when the external load coefficient was 3 after analysis.Due to the significant impact of surface roughness and dimensional accuracy of rollers on their mechanical properties,the surface roughness measuring instrument and CMM were used to measure the surface roughness of the modified roller and the points on the generatrix.The fitting curve was obtained by data fitting method,and the external load coefficient of the fitting modification curve was calculated.