Research On The Bending Compensation Oriented Prediction Model Of Three-dimensional Variable Curvature Metal Tube

Three-dimensional variable curvature metal tube have been widely used in aerospace,ship,vehicle,nuclear power and other fields,and the springback phenomenon of metal tube is one of the main factors affecting the precision of tube bending.Base on the theoretical study of the springback phenomenon,this thesis propose an in-depth study on the springback prediction model of fixed curvature metal tube and three-dimensional variable curvature metal tube.A numerical calculation method of springback prediction model adapted to the characteristics of tube axis was obtained.Finally,based on the springback prediction model,a springback prediction and automatic compensation system for metal tube bending was developed,and application verification was performed.The main contents of this thesis are as follows:The first chapter introduces the application background of metal tube,especially three-dimensional variable curvature metal tube,and analyzes the springback problem of metal tube in bending forming.The research status of bending springback prediction models for fixed curvature metal tube and three-dimentional variable curvature metal tube is reviewed.Finally,the research content and organizational structure of this article are introduced.The second chapter theoretically analyzes the bending springback of fixedcurvature metal tube from the two aspects of bending springback phenomenon and stress analysis of metal tube,and obtain the ideal model of bending springback of fixedcurvature metal tube.The model is improved by analyzing the error of the theoretical springback prediction model,thereby improving the accuracy of the springback prediction.Finally,the accuracy of the springback model and numerical simulation results were verified by bending experiments on fixed curvature metal tube.The third chapter combines the bending and torsion combine situation of the metal tube,and popularizes the springback prediction model of the fixed curvature metal tube,obtain the mapping function of tube central axis curvature and torsion before and after springback.Combined with the Frenet frame of space curve,the springback prediction model of three-dimensional variable curvature metal tube is studied.In the fourth chapter,according to the characteristics of different curves,a variety of numerical methods of differential equations are generalized to the numerical solution of differential equations of the springback prediction model of three-dimentional variable curvature metal tube,and the application conditions of various numerical methods for different curves and accuracy requirements are studied.The boundary of the mapping function of tube central axis curvature and torsion before and after springback was used to invert the mapping function numerically to realize the springback compensation control of the three-dimensional variable curvature tube.Finally,numerical simulation experiments are performed to verify the accuracy of the springback prediction model of three-dimentional variable curvature metal tube and its numerical calculation,as well as the springback compensation of metal tube based on the prediction model.In the fifth chapter,based on the springback prediction model of metal pipe fittings with fixed curvature and three-dimentional variable curvature metal tube proposed in this paper,a metal pipe fitting springback prediction system is developed..The structure and function modules of the system was specified.Application verification of fixed curvature and small-scale nuclear reactor heat exchange spiral tube respectively.In the sixth chapter,conclusions were given along with the recommendations for future research.