Springback Prediction And Process Parameter Optimization Of High-strength Thin-sheet Multi-step Press Forming And Its Application

In recent years,with the rapid development of aerospace,ocean engineering,petrochemical industry and other industries,high temperature,high pressure,high corrosion and other extreme working conditions continue to emerge,and the demand for special round tubes with high temperature,high pressure,corrosion resistance and other characteristics is growing.Multi-step forming of high strength sheet metal has become an important method of special pipe processing because of its advantages of reducing die size,deformation amount,deformation resistance,improving forming quality,high precision,high reliability and high production efficiency.However,due to the high resilience of high strength sheet metal,it is still difficult to control the resilience of high strength sheet metal in actual production,and it is difficult to optimize the process parameters due to the complexity of the interaction of multi-step pressing forming process parameters.In this paper,springback prediction and process parameters optimization of multi-step pressing of high strength sheet metal are studied,and applied to the design of ABMZ02 high strength sheet metal parts in a company to verify the effectiveness of the proposed method.The main contents of this paper are as follows:In the first chapter,the status quo of multi-step forming technology for high strength sheet metal is summarized,the research significance and technical background of the subject are expounded,and the research status of springback prediction technology and process parameter optimization technology for multi-step forming are summarized.According to the shortcomings of existing research methods,the research content and organization structure of this paper are put forward.In the second chapter,the analysis method of multi-step forming mechanism of high strength sheet metal is presented.This method analyses the forming process and springback process of multi-step pressing of high strength sheet metal.The springback and forming quality of multi-step pressing parts of high strength sheet metal under different process parameters are studied by numerical simulation technology.The importance of process parameters is ranked by grey relational theory,and the main influencing parameters of springback prediction and process parameters optimization are obtained,so as to determine springback prediction reasonably.It provides a theoretical basis for optimum design variables of process parameters.In the third chapter,the springback prediction method of multi-step forming of high strength sheet metal is proposed.On the basis of orthogonal experiment,this method establishes the prediction model by BP neural network,and optimizes the transfer weight and neural threshold of BP neural network by genetic algorithm,so that BP neural network can jump out of local optimum and get the global optimum solution.The springback prediction model was established to predict the springback radius of forming parts and to control the springback status of high strength sheet metal.The prediction model of die radius was established to predict the optimum die radius for rapid die design.Finally,the springback and optimum die radius prediction of multi-step pressing of high strength sheet metal are taken as an example to verify the validity of this method.In the fourth chapter,the optimization method of multi-step pressing process parameters for high strength sheet metal is proposed.In this method,the process parameters of multi-step high strength sheet metal forming are taken as design variables,the forming quality and efficiency as design objectives,and the springback radius deviation,maximum thinning rate and thickness deviation are taken as constraints.A mathematical model for optimizing process parameters of multi-step high strength sheet metal forming is established.In the process of solving,the moving least squares response surface approximation model is established by uniform Latin hypercube experiment,and the global optimal empirical search multi-objective ant colony algorithm is used to solve the problem,and the Pareto solution set of optimizing process parameters is obtained.The process parameters of multi-step pressing of high strength sheet metal were optimized to improve the forming efficiency and quality.In the fifth chapter,combined with the project of springback prediction and process parameter optimization of multi-step forming of high strength sheet metal carried out by Zhejiang University and a company,the springback prediction and process parameter optimization of ABMZ02 high strength sheet metal parts are carried out by using this method to verify the effectiveness of the method described in this paper.In the sixth chapter,summarized the research content of this paper,and prospects the future research direction based on the existing multi-step forming research.