Papers by Author: Yan Qin Zhang

Abstract: Thermal deformation of large size hydrostatic bearing rotary workbench is the most direct factor that affects the machining accuracy of work-piece. The thesis puts forward the method of adding reinforcing plate structure to restrain the workbench thermal deformation, establishes three-dimensional supporting workbench model, with finite element method and sequence of fluid-solid coupling technology have carried on the thermal deformation calculation workbench, and reveals the influence law of different installation position of rib plate on the workbench thermal deformation. The results of the study shows that the method of adding reinforcing plate structure to reduce the thermal deformation of hydrostatic bearing worktable is feasible, and determine the optimal position of reinforcing plate by comparing different results.

Abstract: With heavy NC machine tool is widely used in many oil pad round guide hydrostatic bearing as the research object, in the under condition of variable viscosity, establish oil film viscosity-temperature equation. Adopt finite volume method, simulation the hydrostatic bearing internal fluid temperature field under different flow rates on the speed of 6R / min. Numerical simulation hydrostatic thrust bearing oil film temperature field, can find a general high temperature region, and then take effective control temperature. It can achieve the hydrostatic thrust bearing oil film temperature field prediction for engineering practical oil chamber structure, offer the theoretical foundation for optimization design.

Abstract: The pressure field of the clearance oil film of the hydrostatic bearing in varies velocities was simulated based on Finite Volume Method (FVM) by the software of Computational Fluid Dynamics. In this article, a conclusion could be drawn that the viscosity has great influences on the pressure in the heavy hydrostatic bearing and it cannot be neglected especially in high rotating speed. The results of numerical calculations provide internal flow status inside the bearing, which would help the design of the oil cavity structure of the bearing in engineering practice.

Abstract: The multi flexible body dynamical simulation model of dynamical vibration absorption lathe tool with large length to diameter ratio is built up according to the actual experiment lathe tool by using the software ADAMS and ANSYS. The experiment data which are consistent with the simulation result verify the correctness of the multi flexible body dynamical model. Aiming at reducing the peak value of system frequency response, the dynamical vibration absorption system is optimized. The optimized frequency curve shows that the system frequency response is improved obviously. On this basis the influence of the mass of heavy turning body on the vibration system is discussed. Also, the relationship of the mass of heavy turning body and the optimal system parameters including equivalent stiffness coefficient and equivalent viscous damping coefficient is studied. This offers the design considerations about the structure of the dynamical vibration absorption lathe tool with large length to diameter ratio.

Abstract: A scheme of improving performance of hydrostatic journal support was presented, that is, control journal support pose by controlling flow of four controllable chambers and Coupling various oil film thickness, to assure journal support expected pose; Chamber flow can be regulated by electro hydraulic servo valve-control variable pump according to the surface roughness, load, cutting force, and thermal results of journal support. The mathematical model of the controllable chambers flow, servo variable mechanism and controller were built; the pose control model was established, which contain the kinematics positive and negative solution and control strategy of hydraulic cylinder position feedback; Hardware-in-loop simulation experiment was carried on the electro hydraulic servo test bench by mean of the non-linear relation of film thickness and the hydraulic cylinder displacement. Simulation and Hardware-in-loop simulation experiment results show that the controllable journal support exhibit high oil film rigidity can stably and quickly track the expected goal and can be broadly applied in high precision heavy horizontal machine tool.

Abstract: Lubricant viscosity is one of the key parameters in hydrostatic bearing research. In order to solve the load capacity of hydrostatic bearing in the heavy equipment, viscosity-temperature equation of lubricant film is established, and the viscosity-temperature curve is fitted by B-Spline curve. Finite volume method is used on numerical simulation of pressure field of heavy hydrostatic bearing in constant and variable viscosity respectively and in different rotational velocity, whereafter, viscosity influence on load capacity of heavy hydrostatic bearing is discussed. The results show that, viscosity impose a minor influence on cavity pressure of hydrostatic bearing when rational velocity is low; whereas, when rational velocity is high, especially to the heavy hydrostatic bearing which with high liner velocity influence of viscosity changing must be taken into account in calculation. Numerical simulation results reflect the pressure distributing state of bearing veritably; furthermore, these provide theoretical basis for hydrostatic bearing design and lectotype in practical application.

Abstract: Owing to setting viscosity of lubrication oil as a constant value will lead errors in hydrostatic bearing calculation, the influence of cavity depth on load capacity of heavy static bearing is analyzed in variable viscosity condition. Firstly, viscosity-temperature equations of oil film are established; secondly, viscosity-temperature curve is fitted by B-Spline; finally, using finite volume method, hydrostatic pressure field and dynamic pressure field of heavy hydrostatic bearing is calculated with different cavity depth at the same velocity, and influence of cavity depth on load capacity is revealed. The results show that, were the cavity depth shallow enough(≤2mm), hydrostatic pressure and dynamic pressure of cavity would decline rapidly with the cavity depth increasing; whereas, were cavity deep enough(≥2mm), hydrostatic pressure and dynamic pressure of cavity would change little with the cavity depth extending. This numerical simulation reflects real distribution of bearing pressure appropriately, and provides a theoretical basis for hydrostatic bearing design and lectotype.

Abstract: The build-in dynamical vibration absorption system with damping is applied to increase the dynamic stiffness of a boring bar. According to construction and vibration features, multi flexible body dynamical model of the vibration absorption system is built up by using the software of ADAMS and ANSYS. Also the vibration characteristic of an actual boring bar is analyzed by using SA-78 2ch FFT analyzer. Through the analysis of simulation results and experimental data the accuracy of the model is validated. On this basis the influence of the radial stiffness coefficient of rubber brushes, the damping coefficient of damping fluid and the mass of heavy turning body on the vibration system is discussed by using the vibration analyses module of ADAMS. The simulation results verify the feasibility of the initial structure design; establish the design key points in the actual design. The multi flexible body dynamical model of the vibration absorption system has been simulated, optimized and analyzed. And optimized parameters are obtained finally. With these optimized parameters, actual dynamical vibration absorption boring bar with damping can be designed, and the dynamic stability of the bar is enhanced thereby.

Abstract: In order to solve the thermal deformation of the hydrostatic thrust bearing in the heavy equipment, a simulation research concerning temperature field of multi-pad hydrostatic thrust bearing having circular cavities was described. The Finite Volume Method of Fluent has been used to compute three-dimensional temperature field of gap fluid between the rotation worktable and base. This study theoretically analyzes the influence of cavity radius and cavity depth on the bearing temperature performance according to computational fluid dynamics and lubricating theory. It has revealed its temperature distribution law. The simulation results indicate that an improved characteristic can be gotten from a circular cavity hydrostatic thrust bearing, oil cavity temperature decreases by gradually with cavity radius enhancing, oil cavity temperature decreases by gradually with cavity depth. Through this method, the safety of a hydrostatic thrust bearing having circular cavities multi-pad can be forecasted, and the optimal design of such products can be achieved, so it can provide reasonable data for design and lubrication and experience and thermal deformation computation for hydrostatic thrust bearing in the heavy equipment.

Abstract: The surface material of Elastic-metal pads(EMP) is PTFE which has poor wearability . Ion implantation can improve the wearability of EMP surface .This paper investigated the wearability improvement of the EMP’s surface by Al2O3/PTFE film which generated by ion implantation. The accelerating voltage of the ion implantation apparatus is 40KV and the ion emitting energy of aluminum is 20KeV. The dosages of three kinds of Al3+ ion beams in the study are 1×1015 ions/cm2, 5×1015 ions/cm2 and 1×1016 ions/cm2 respectively. The aluminum ion’s density is 10uA/cm2. The vacuum pressure of the ion implantation is 3×10-3Pa. The experimental specimens modified by Al3+ ion implantation were tested by ESCA, XRD, AFM/FFM and nanometer probe , which got the chemical bond, phase structure and friction coefficient of the film. According to the experimental results, the mathematical model was built using the Fesow Geometric Model and the Halind Rang Theory. The computer simulation was made in which SRIM simulator program was employed. The ion implantation’s energy for the simulation is 20keV and the material density of PTFE is 2.56g/cm³. In addition, the dose is 5×1015 ions/cm², the time interval is 230 minutes and the velocity of Al3+ ion implantation is 2.15-2.20×1013 ions/minute. Finally the simulation curves of particle distribution, energy distribution and impairment etc. were plotted and discussed.