Research On Low-relaxation Prestressed Steel Strand Induction Heating Numerical Analysis

In the electrical engineering discipline,electromagnetic thermal effect is an important part of this discipline.The stabilizing process of low-relaxation prestressed steel strand is the critical step to determine product quality,the process is achieved by induction heating.The electrical parameters and structural size of the induction heating coil directly affect the temperature difference between center and surface,heating time and system output power of steel strand induction heating.In view of this,steel strand is heated by spiral induction heater as the research object,the relationship models between the temperature difference between center and surface,heating time and system output power of steel strand induction heating and the main electrical parameters,structural parameters are studied,the optimal value are found combined with intelligent algorithms.Finally,the steel strand induction heating result and system efficiency are improved.The calculation method of steel strand deformation is derived based on Hertz contact theory,the measured experiment of deformation is carried out,the calculation result of this method and experimental result are consistent.On this basis,the accurate finite element model of steel strand induction heating is established.The electromagnetic field,eddy current field and temperature field in the induction heating process of steel strand are calculated by using the finite element analysis method,the relevant data are obtained.The measured experiment of steel strand induction heating temperature field is carried out,finite element analysis result and experimental result are consistent.By finite element analysis,it is known that the main electrical parameters of affecting the temperature difference between center and surface,heating time of steel strand induction heating are current density and frequency.A variety of mathematical models between the current density,the frequency and the temperature difference between center and surface,heating time are established by multiple linear regression method,the evaluation criteria of optimal mathematical model is proposed,the optimal mathematical model is power function.On this basis,a coefficient correction method of mathematical model is proposed based on polynomial fitting method,the prediction accuracy of optimal mathematical model is further improved.The network model is established using the algorithm of BP neural network,it is verified that the optimal mathematical model by coefficient correction predicts more accurate.The typical electrical parameters of steel strand induction heater are designed,the inner diameter size of induction coil is changed,a large number of finite element data of the temperature difference between center and surface,heating time and system output power are calculated.By using polynomial fitting method,the functional relationships between the inner diameter and the temperature difference between center and surface,heating time and system output power are established.The measured experiment of induction coil is carried out,the established functional relationship and experimental result are consistent.Based on the determined mathematical models between the temperature difference between center and surface,heating time and system output power and the main electrical parameters,structural parameters,using linear weighted sum method,minimum deviation method and an improved minimum deviation method to construct the evaluation function,the best numerical value of electrical parameters and structure size are found combined with genetic algorithms.