Multiphysics-Fields-Based Method To Design Optimization Of Factors Affecting The Vibration Response For Machine Motorized Hydrostatic Spindle System

The Machine Motorized Hydrostatic Spindle(MMHS)system is the key component of the CNC machine tool,which plays an important role in its machining process and directly affects machining accuracy.The MMHS system at high-speed will produce additional weight and large heat transfer to its components,due to RotorDynamics and thermal loads effect.Unnecessary weight owing to high-speed and heat transfer effects will release high vibration to the spindle system,hence reaching it proper machining efficiency is noticeably challenging.Recently,the motorized hydrostatic spindle has developed rapidly due to its outstanding advantages to overcome the challenge of machining efficiency.There has been a lack of research into design optimization,which fully considers RotorDynamics and thermal effects.This thesis is aimed to develop a multiphysics-fields-based method to design and analysis for optimizing the performance factors of MMHS system under RotorDynamics and thermal effects.The multiphysics-fields-based method is categorized into three main parts:design and Computation-Fluid-Dynamic(CFD)analysis for journal bearings,steady-state-thermal analysis for stator-rotor,and RotorDynamics analysis for spindle system.With the purpose of providing basics parameters for bearing support and CFD model,new four recess journals bearing due its effective to support large loads,providing large stiffness and damping is designed.First,general mathematical model for journals bearing has been developed by using basic theories of the hydrostatic flow.Then,the corresponding analytical models for velocity-field,pressure-field,carrying capacity,oil-film stiffness and temperature rise are developed by applying Navier-Stocks and energy methods.An integrated thermomechanical model of MMHS system is developed by using Finite-Element-Method(FEM)in RotorDynamics analysis and heat transfer analysis.The L series CN lathe motorized spindle is provided to establish thermomechanical model includes of fully integrated models of spindle dynamic,rotating disk,and hydrostatic journal bearing and thermal models.Simulation and analysis of factors affecting the vibration characteristics of MMHS system is entirely established by using multiphysics-field method.The method estimates the static stiffness,natural frequency and its mode-shapes,and steady-state frequency response function.The FEM analysis is verified by applying the principles of similarity design method,and programing in MATLAB and using DH-VTC experimental test established on manufactured spindle supported to its bearings.Further,the parametric-optimization method is established through using Response-Surface(RS)model that improved by including the effects of RotorDynamics and thermal accompanied by Taguchi quality loss analysis.Box-Behnken Design(BBD)of experiment,due to its efficiency in providing much data in a nominal number of required statistical experiments is used to build the Design of Experiment(DOE)for RS optimization method.The results found showed that:the hydrostatic bearing can support great loads without journal turning and deliver high direct stiffness along with damping coefficients.The load carrying capacity and static stiffness of hydrostatic bearing do not rely on fluid viscosity,thus these features making them perfect rotor support elements in manner fluid pumps.Further,multiphysics-fields-based method to design and analysis results obtained showed that the MMHS system is greatly influenced by the body temperature of stator-rotor when comparing it to FEM analysis under only cutting force effect.The rotating unbalanced force of motor-rotor and its thermal-loss have higher contribution to max-deformation of whole MMHS system.The dynamic RotorDynamics analysis result obtained noted that,the thermal-induced-prestress parameter has large effects on MMHS system design due to the axial thermal stress at motor-rotor location that causes the spindle shaft to be prestressed.Finally,from the design optimization results obtained found that,the proposed method not only improves the structural weight of MMHS system,but also the potential savings can be achieved in term material and energy resource.It found that there about more than twenty-percent of total material loss cost saving for MMHS system,and so about more than twelve percent saving for quality feature when comparing to its original value.The worthy agreement between results is obtained when comparing the FEM analysis results of optimal RS analysis model with that of the original model.The thesis presents an original research on integrated RotorDynamics analysis and heat transfer analysis and its effects on the vibration characteristics of MMHS system accompanied by optimizing the performance factors of MMHS system.It satisfactorily contributes to(i)further understanding the static RotorDynamics analysis of spindle system under thermal-induced forces effects,(ii)knowledge the effect of thermal-induced-prestress parameter on dynamic RotorDynamics analysis,and prediction of its improvements in vibration characteristics of MMHS system,and(iii)development of an effective design optimization method for designing MMHS system.Then,prediction of the sensitivities of performance factors on vibration characteristics of MMHS system under thermal-induced-prestress and RotorDynamics effects.