The Nondestructive Disassembly Method Of Interference Fit Sleeve In The Case Of Cooling Excitation

Remanufacturing is a main method for the recycling of end-of-life products,also an important measure to practice circular economy and to establish the resource-economical and environment-friendly society.As a primary process of remanufacturing,disassembly has a significant influence on recyclability rate of retired parts,as well as the efficiency and costs of the followed repair process.Interference fit is widely used in mechanical products as a kind of rigid connection;it’s hard to be dismounted and easy to be damaged.How to realize automated and nondestructive disassembly is worthy of research.Taking interference fit components as research objects,the disassembly technique is studied.As for contained part such as sleeve,a disassembly method by cooling excitation is put forward,which uses liquid nitrogen to cool the contained part,then cooling deformation is occurred and the interference is weakened,so that nondestructive disassembly is implemented.Surrounding the disassembly method proposed,theoretical analysis,finite element simulation and experiment research are conducted.The main work is as follows:(1)Building the interference fit shaft-sleeve model,the variation regularity of disassembly force is studied through static analysis and transient dynamical analysis.Considering the influence of axial deformation on disassembly,a regression equation about disassembly force,interference amount and the bending of shaft is obtained by regression analysis,which can estimate the disassembly force.(2)The fundamental of the cooling excitation disassembly method and its influence factors are expounded.Taking the sleeve and shaft seat as research objects,the transient heat transfer differential equations under liquid nitrogen cooling excitation are established,transient temperature field is solved by Laplace transformation and numerical inversion;based on thermoelasticity,disassembly force equation is derived,and theoretical model of cooling excitation disassembly method is formed.As the key model parameters,the heat transfer coefficient of liquid nitrogen cooling and the thermal contact resistance are calculated.(3)Simulation researches on cooling excitation disassembly method are carried out,which include brass-45#steel,45#steel-45#steel,QT500-45#steel three kinds of material combination models,and the variation regularity of temperature and disassembly force are gained which are changing with cooling time.The model parameters such as heat transfer coefficient,thermal contact resistance,thermal conductivity,etc,and cooling combining heating method are explored to find their influences on disassembly results.(4)Through experiment researches,the disassembly force and the surface appearance of the demounted sleeve are studied,the differences between simulation results and experiment results are deeply analyzed.After confirming the key factor,the simulation model is modified.In sum,the cooling excitation disassembly method helps to decrease disassembly force and disassembly damages effectively,so the disassembly method is proved to be feasible.