| Based on the 1000/250 type mill MDDK diameter of 250 mm,1000 mm long roller as the research object,in order to comprehensively improve the quality of flour as the goal,the roller kinematics and dynamics theoretical analysis and the corresponding experiment combination,and the use of Ansys The Workbench finite element analysis software analyzes the dynamics,stress fatigue and dynamic characteristics of the roller from the perspective of dynamics of the roller.It provides effective theoretical support for the research and development,maintenance and use of the roller and the optimal design of the roller shaft.The main research work of this paper is as follows:(1)In combination with the structure and working principle of a roller mill,a dynamic model of the roller and a kinetic balance equation of the roller are established based on the Lagrangian equation in the form of viscous friction and Rayleigh dissipation functions.Different assumptions are made in the rotation of the roller.The kinematics model,the differential equations for torsional vibration,the kinematics model for the radial vibration of the roller,and the differential equation for the radial vibration are established respectively for the torsional vibration of the roller.The establishment of the equation reveals the function of the angular displacement as a function of time during torsional vibration,whereas the differential equation for radial vibration reveals the radial displacement as a function of time.After that,the kinematic parameters and dynamic parameters of the roller were calculated.(2)Calculate the kinematics parameters and productivity of MDDK 1000/250 mill roller.The roller linear velocity was 6.28m/s and the centripetal acceleration was 315.51mm/s~2.The dynamics parameters of the roller are calculated,and the external forces of the roller under no-load and load are theoretically analyzed respectively.When the load of the roller is obtained,the variation range of the starting angle?is 0°???9.7°.The frictional force of the roller and the slow roller is in the range of 6520.14N?F1?6615N,7244.60N?F2?7350N,The curve of the frictional force of the slow/slow roller with the starting angle?,the curve of the grinding length with the starting angle?,the quality of the grinding roller,the radial support force of the bearing against the roller,the friction resistance moment of the bearing against the roller,and the external exciting force Changes over time,as well as the roll moment of inertia,polar moment of inertia,moment of momentum,and roll deflection.The derivation of these parameters makes the kinematics and kinetic parameters of the roller concretely quantified in theory and provides a reference for the flour processing industry.(3)Under the premise of being able to accurately reflect the actual mechanical properties of the roller structure,through the actual parameters of the MDDK 1000/250 mill roller,SolidWorks software was used to establish a three-dimensional solid simplified model of the roller and the roller bearing,and It was introduced into ANSYS Workbench for static analysis,strain fatigue analysis and modal analysis and transient dynamic analysis of the dynamic characteristics of the roller.(4)Based on the static analysis of the grinding roller,the stress cloud map and deformation cloud diagram of the roller structure are obtained.The maximum equivalent stress position,maximum deformation position and stress concentration position of the roller occur at the contact parts of the shaft and the bearing,respectively.The maximum value of the equivalent stress of the roller is 166.04MPa from the stress cloud diagram of the roller structure in the middle part of the roller body and the shoulder part of the roller.After that,the stiffness and strength of the grinding roller were checked,which provided theoretical support for the structure design of the grinding roller.The modal analysis of the grinding roller was used to calculate the first six-order main vibration mode and the first six-order vibration mode of the grinding roller.State natural frequency,the minimum natural frequency of the grinding roller is 192.01Hz,and the working frequency of the grinding roller is f1=8Hz,and the maximum exciting frequency of the motor is 24.33Hz.It is judged whether the roller structure generates resonance.If resonance occurs,then In the later design of the roller structure can be optimized to avoid resonance.(5)Analyze the transient dynamics of the roller,and discuss the response of the roller under the external excitation force to the stress,strain,velocity and acceleration.The maximum equivalent stress of the roller reached steady state is 18.642MPa,the linear velocity and the centripetal acceleration values are respectively 6.2885m/s and 315.73m/s~2.The range of movement of grinding roller is 0~250.01mm,which provides a theoretical basis for improving the addition of elemental components and designing the structural dimension of the weak part of grinding roller.(6)The stress fatigue analysis was performed on the roller,and the maximum safety factor under the high cycle fatigue of the roller was 15 and the minimum was 0.70646.The cloud damage and life curve of the roller was obtained.The maximum damage was obtained from the roller damage cloud map.Occurs at the contact portion between the roller shaft and the bearing,and the position where the shortest life occurs from the life cloud map corresponds to the position where the maximum equivalent stress occurs in the static analysis of the roller,and the fatigue failure of the roller can also be seen from the figure.The minimum number of fatigue cycles is 27,950,and the maximum is 10~6.Determine whether the minimum fatigue life meets the design requirements.(7)Experimental testing of the kinematic parameters of the roller was carried out.The maximum linear velocity of the roller reached 6.101m/s and the maximum centripetal acceleration was 297.768m/s~2.The test results were compared with the simulation results.The linear velocity error rate is 3.07%and the centripetal acceleration error rate is 6.035%.The experimental results are basically consistent with the simulation results.In addition,the vibration speed,vibration acceleration,and vibration displacement of the BUHLER 1000/2501 heart mill roll at three different positions of C,D,and E at the time of load operation were experimentally measured.The variation ranges of vibration speed at E and E were2.94-4.03mm/s,3.57~4.82mm/s,and 3.86~4.95mm/s,respectively;the vibration acceleration change intervals were 19.85~23.12m/s~2,and 19.24~21.17m/s~2,respectively,17.88~20.1m/s~2,the range of change of vibration displacement is 0.007~0.026mm,0.008~0.019mm,0.01~0.015mm,respectively,and the radial runout at C is basically stable at 0.012mm,which is equivalent to the theoretical calculation of 0.0126mm.In comparison,the error rate is only5%.Afterwards,detailed analysis was made on the three groups of data,and suggestions for improving the service life of the grinding roll were proposed. |
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