Dynamic Characteristic Analysis And Reliability Robust Design Of Gear Shaft In Shearer Cutting Section

This paper takes the transmission shaft of MG750 shearer's cutting unit as the research object.It is connected with the cutting motor torque shaft to transmit large output torque,which plays a crucial role in the normal work of the cutting part drive system.Through the detailed study of this key part,establish the "bearing-rotor" system model,analysis the dynamic characteristics of bearings and this shaft,and consider the system resonance failure,shaft stiffness failure and bearing fatigue failure,further analysis the influences of bearing structure,material parameters,initial radial clearance and external load on bearing radial stiffness with the change of rotation speed.By taking the radial stiffness of the bearing as the medium,study the influences of these parameters on the dynamic characteristics and reliability of the system.Finally,complete the system reliability robust design by integrating all failure modes and system reliability sensitivity calculation results,and establishing corresponding mathematical optimization model.Specific contents are arranged as following:(1)Based on Hertz and EHL theory,Palmgren's modified formula and Dowson's minimum film thickness formula for linear contact elastohydrodynamic lubrication under isothermal conditions,establish a solution model for dynamic stiffness of cylindrical roller bearing and analysis the influence rules of bearing structure and material parameters,radial clearance,working speed and radial load on radial stiffness.(2)Using transmission shaft of the simplified parametric modeling and importing it into workbench,replacing bearing with spring to carry out the modal analysis and harmonious response analysis.Using DOE construct experiment of the natural frequency of the system,radial deformation of shaft end and random factors.Finally,using the transfer matrix method verify the results of the finite element.(3)Using the response surface analysis screens all random variables.Using genetic BP neural network fits the functional relationships between system natural frequency,the maximum radial deformation of shaft end and the axial dimensions,the material parameters.In addition,the functional relationship between the maximum orthogonal shear stress on the contact surface between the bearing roller and the inner and outer raceway and the structural material parameters of the bearing is fitted.Finally,establish the functional functions and analyze their reliability sensitivity analysis including bearing strength,natural frequency and shaft stiffness.(4)Based on the reliability robust design theories,optimize the quality and reliability sensitivity of the drive shaft system,establish mathematical optimization model that solved by Matlab,takes the bounds of each random variable and bearing strength reliability,transmission shaft frequency reliability and stiffness reliability lower limit as a constraint.In conclusion,for three main failure modes of the gear shaft,apply reliability knowledge to carry out reliability sensitivity analysis and robust design of the system.Particularly,study the influences of bearing structure,material parameters,radial load and initial radial clearance on the system that provides certain reference value for production design and performance optimization of drive shaft.