Theoretical And Applied Research Of Optimal Thermal Fit Of Hollow Piece And Cylindrical Piece

Thermal deformation is the general phenomenon of thermal effect. Variation in temperature causes the corresponding changes in the dimension of components, conventional thermal deformation theory and calculating formulas are approximately applicable to the components of low or general precision but not to the high precision or modern nanoscale precision field. The paper summarizes domestic and abroad achievements in this area. On the basis of now available achievement of professor Fei Yetai, Under the subsidization of several projects, theoretical and experimental studies on hollow pieces and cylindrical pieces in even steady-state temperature field have been undertaken and the mathematical models have been set up for the first time. And studies on a few kinds of hollow pieces and cylindrical pieces under stress in uneven steady-state temperature field have been undertaken as well, the rule of thermal effect on fit of hollow piece and cylindrical piece are analyzed, the theory of optimal thermal fit is advanced to solve the thermal effect on fit. The main contents of the thesis includes as following:After several years of research, we get some conclusions of important scientific value and practical significance. The thermal deformation of any components' dimension does not follow the law of conventional linear formulas but connected with other dimension of the body , can be shown as the nonlinear function of other dimension, functions of thermal deformations of hollow pieces and cylindrical pieces in even steady-state temperature field have been achieved for the first time in domestic high precision field, the experimental results have been presented to confirm the theory. On the basis of synthetically analysis about domestic and abroad achievements, studies on some typical hollow piece and cylindrical piece in uneven steady-state temperature field are accomplished. The results consummate the whole theory of thermal deformation, and it will lay a more comprehensive and intact foundation about the research of thermal deformation.The tolerance and fit of the hollow piece and cylindrical piece is a very important primary standard in mechanical field. Current standards of tolerance and fit are based on standard temperature 20°C. so the precision of fit can be achieved only on 20°C, but the temperature will change when the mechanical system runs in steady operation, the ruleof thermal deformation of hollow piece is different with the rule of thermal deformation of cylindrical piece, so if the temperature changes, the fit precision will depress. To solve the problem, the theory of optimal thermal fit is advanced after comprehensive research on fit and tolerance. Offsets for the current basic deviation of hole-base cylindrical piece are given to solve the effect of thermal deformation.Quartic equations are adopted to simulate the deformation of model of water turbine rotor used in Sanxia engineering after lots of experiments, measuring results on the water turbine rotor used in Sanxia engineering is also presented, and the results verify the theory. The achievements of research have been applied in the processing and control process of water turbine rotor used in Sanxia engineering.On the basis of now available achievement of professor Fei Yetai's research team, dedicated clamping fixtures are designed to make it convenient for internal diameter measuring of hollow pieces , external diameter measuring of cylindrical piece, and measuring of gap length. The experimental devices not only finishes verification but also provides foundation for more accurately research of thermal deformation.The main originality innovation of the thesis includes as following:1.Functions of thermal deformations of hollow pieces and cylindrical pieces in even steady-state temperature field and uneven steady-state temperature field have been achieved for the first time in domestic high precision field.2.The theory of optimal thermal fit is advanced after comprehensive research on fit and tolerance to solve the problem of thermal deformation, and the thermal offsets for the hole-base system national deviation standard of frequent dimensional range and typical structure in different temperature field.3.On the basis of synthetically analysis about domestic and abroad achievements, studies on some typical hollow piece and cylindrical piece in uneven steady-state temperature field are accomplished, and have solved the problem of thermal deformation of water turbine rotor used in Sanxia.