| Centrifugal casting is a kind of special castings,which is quite suitable for manufacturing hollow axisymmetric parts.Furnace tubes in chemical industry are manufactured mainly by centrifugal casting.In the process of manufacturing furnace tubes,vibration of the mould leads to uneven thickness of tubes,then influences the performance of the tubes.This desertation takes the roller-supporting horizontal centrifugal casting machine as ths research subject and the contents include a systematically research on the dynamic performance of the centrifugal casting machine,the influences of various parameters on the dynamic performance and the influences of vibration on the final wall thickness of the centrifugal casting furnace tubes through the mechanical modeling and experimental approach.The main research contents and achievements of this desertation are listed below:The calculation models of stiffness and damping of roller-supporting are built through mechanical analysis,then the vibration model of roller-supporting horizontal centrifugal casting machine is established with considering the mass eccentricity and the phase angle of the eccentric mass,and the model is solved numerically by use of transfer matrix method.The influences of supporting span and supporting angle on the natural vibration of mould rotor and the influences of eccentricity and phase angle of eccentric mass on the unbalanced response of mould rotor are studied.A vibration test rig of centrifugal casting machine is designed and set up,and the test is conducted to verify the validity of the theoretical model.The models describing the geometric errors and the surface topography of the rollers and mould are established.The approach to calculate the coordinates of contact points is established through geometrical analysis to determine the excited forces caused by the geometric errors or surface topography of the mould.Using tranfer matrix method,vibration characteristics of the mould are calculated with considering the geometric errors and surface topography of rollers.The influeces of geometric errors and surface topography of rollers and mould on the frequency-amplitude response,vibration mode and the orbit of mould center are studied.The stiffness and damping model of block foundation on elastic half-space is established.Using vibration theory and rotor dynamics,the dynamic model of roller-supporting horizontal centrifuga]casting machine with considering the foundation is established.With transfer matrix method,the dynamic model is solved and the influences of the height,embedment depth and bottom size of foundation on the natural vibration and forced vibration are numerically studied.Based on the dynamicl model of centrifugal casting machine and hydrodynamics theory,the coupling model of vibration and molten metal flow for mould is established,and the modified transfer matrix method is used to solve this coupling model.Then the vibration amplitude and the molten metal flow pattern at different moments are obtained.The influences of the mass of molten metel on the amplitude and resonance speed and the influences of the eccentricity of the mould rotor and the weight of molten metal on the thickness of the furnace tubes are studied.Combining heat transfer theory and the coupling model of mould vibration and the molten metal flow pattern,the model of coupling mould vibration,molten metal flow pattern and the solidification of casting tubes is established.With this coupling model,the vibration amplitude and the molten metal flow pattern and the temperature field at different moments are obtained.The cooling process of casting furnace tubes and the effect of mould vibration on the final wall thickness of easting furnace tubes are studied and analyzed.The research and the results obtained in this desertation can provide theoretical reference for the design and optimization of the roller-supporting horizontal centrifugal casting machine and the prediction of the wall thickness of the centrifugal casting furnace tubes. |
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