Thermal Stress Analysis Of Large Diameter Tubing By Intermediate Frequency Induction Heating

The matching of intermediate frequency induction heating parameters and hydraulic ultra-low push speed is one of the key problems affecting the quality of the elbow in the large-scale push hydraulic pipe bender.So the analysis and research of intermediate frequency induction heating parameters is particularly important.In view of the complexity of magnetic-thermal-force coupling in practical conditions,this paper using the method of numerical simulation analyzed and optimized the effect of process parameters on the heating effect of X80 pipeline steel during induction heating,and the numerical simulation of the optimized heating parameters is applied to analyze the distribution of thermal stress in the tube during induction heating to ensure the bending quality of the elbow.The main contents of the research are as follows:(1)Based on the theory of induction heating and bending forming of elbows by induction heating,the mathematical model and finite element calculation model of induction heating for pipe are established and the effect of various process parameters on the heating effect were analyzed.The skin effect and adjacent effect had great influence on the heating effect.(2)The mathematical equation of the two regression models are obtained by regression analysis of the simulation data under different heating parameter combination.Compared and analyzed the relevant test standards of each regression equation,a mathematical model for the outer wall temperature prediction during induction heating is obtained.(3)Taking the process parameters as the test factors and the inner and outer wall temperature difference of the pipe as the evaluation index,the orthogonal test was established to optimize the process parameters.The primary and secondary relationships of the process parameters affecting the heating effect and the optimal combination of the process parameters are obtained as well as provided the basis for further optimization of the process parameters.The BP neural network is constructed using the orthogonal test and numerical simulation data as samples.Obtained the prediction model of the influence of process parameters on heating effect,and as a fitness function,used the genetic algorithm to optimize the process parameters globally.So that obtained the optimal process parameters group of pipe induction heating.(4)The simulation model is established by the optimized process parameter group,so that calculated the magnetic-thermal-mechanical coupling of induction heating of pipe.The correctness of the optimization method is verified by compared the results of optimization and simulation,and the distribution of stress and strain in the induction heating process under the process parameters is analyzed to ensure the stability of the bending quality and the service life of the pipe.