Research On Mechanical Modeling And Defect Elimination Criterion Of Thick Plate Rolling

The thick plate,as the raw material of engineering structure,is widely used in bridge,ship slab,ocean engineering and other fields,and occupies an irreplaceable position in the national economy.As a mature steel processing technology,the hot rolling is the main method to produce thick plate.However,China's thick plate production still has problems in utilizing the potential of the rolling mill adequately and the quality of rolled products is not high enough.Thus,it is urgent to improve the level of rolling technology.The research on the model of rolling parameter is valuable as it is the basis for the adjustment of thick plate production process.At present,the methods of studying rolling parameters are theoretical analysis,neural network modeling and finite element simulation.Among them,the theoretical analysis can derive specific analytical formula and display the constraint function relationship of various physical parameters clearly,which is beneficial to reveal the essence of rolling process.Besides,the neural network modeling and finite element simulation can analyze complex rolling process,and provide comparatively accurate predicted results.In this paper,the rolling force of thick plate and the elimination of central defects are studied by the above methods and combined with experiments.The main work and progress are as follows:(1)In order to solve the problem that it is difficult to solve the rolling energy rate caused by the nonlinear characteristic of the Mises specific plastic energy rate,this paper constructed a new linear yield criterion by calculating the integral median value of the variable angle yield function.The new criterion is called as the IM yield criterion for short.On this basis,the corresponding equation of specific plastic energy rate was derived,and the reliability of the new criterion was verified by experimental data.The proposed yield criterion can provide the method preparation for the linearized analysis of rolling energy rate in this paper.(2)According to the characteristics of metal flow in rolling process,an elliptically distributed kinematically admissible velocity field was built in this paper,and a theoretical model of rolling force based on this velocity field was obtained.Meanwhile,a neural network model based on the production data was established,and a data model whose accuracy was significantly higher than that of the theoretical model was obtained.On this basis,the two models were integrated by the method of error gap compensation,and an integrated model with clear mathematical interpretation and reliable accuracy was obtained.Furthermore,the experimental verification and the analysis of the parameter law were carried out.The above analysis provides a new method for the accurate obtaining of rolling force.(3)In order to study the evolution behavior of void defects in thick plate rolling,an upper bound triangular velocity field with an elliptical defect was established.The defect elimination criterion was derived through energy calculation,and the corresponding simulations for comparison and experimental verification were performed to verify the reliability of the derived criterion.Meanwhile,compared with the existing criteria,the criterion shows high accuracy and can give scientific guidance for eliminating defects and improving the quality of thick plate.