Dynamic Evaluation System Of Geometric Accuracy For Electrical Upsetting Process Of Large-scale Nickel-based Alloy Valve And Its Application

The electric upsetting process of super-large size gas valve is a complex process of electric-thermal-multi-field coupling.These process parameters affect each other during the electric upsetting process,thus,any unreasonable setting of process parameters may lead to defects or even scrapping of electric upsetting parts and it is difficult to design process parameters.Now,the design of electric upsetting process scheme for super large size gas valve assisted by finite element simulation.However,it is an urgent problem to find a method to verify the geometric accuracy of upsetting finite element simulation and ensure the reliable geometric shape prediction ability of the model.On the other hand,the size measurement of electric upsetting parts generally adopts manual measurement,which has low efficiency and poor detection accuracy and is difficult to measure the size of electric upsetting parts in the forming process.Therefore,it is of great practical significance to seek a method with high measuring efficiency and precision to measure electric upsetting parts in forming process.In this paper,a dynamic evaluation system for geometric accuracy of electrical upsetting process of large nickel-based superalloy valve was established.The geometric accuracy of electric upsetting finite element simulation was tested and evaluated,and the key dimensions of electric upsetting parts were measured efficiently and accurately during the forming process.The paper laid the groundwork for digital twin of electric upsetting technology.The main research contents and conclusions of this paper are as follows:(1)The camera calibration was finished based on Bouguet calibration method.The distortion of camera image was corrected,and the accuracy of electric upsetting image was improved.Meanwhile,the identification of electric upsetting parts in the image was realized based on machine vision measurement.According to the identification,the measurement of the key dimensions of electric upsetting parts and the identification of the contours of electric upsetting defects was completed.Based on MATLAB platform,a geometric dynamic evaluation system for electric upsetting forming process of gas valve was developed,which realized the dynamic measurement of key dimensions of workpiece and the dynamic evaluation of geometric accuracy of finite element simulation.(2)A finite element model of the electrical upsetting process was established,and the finite element simulation of the electric upsetting process was carried out according to the actual valve electric upsetting process.The geometric accuracy of finite element simulation was tested and evaluated in combination with the actual electric upsetting forming process during the dynamic evaluation system of geometric accuracy.The results show that the finite element model of electric upsetting can predict the geometric shape of electric upsetting parts with high precision,which can guide the practice production of electric upsetting parts.(3)Based on the finite element model of electric upsetting process,the influence of current and upsetting force on the defects of garlic hollow,surface pits and surface waves in the upsetting process was studied.It was found that increasing the initial value of heating current current and the ascending gradient of heating current could effectively improve the garlic hollow defect.The surface pit can be effectively controlled by adjusting the peak upsetting force.The surface wave can be avoided by keeping the upsetting force loading stable at the later stage.(4)The validity of the control method for defects in electric upsetting process was verified by the electric upsetting experiment of large size gas valve.The results show that the optimization method is effective,which can eliminate defects in electric upsetting process and ensure the smooth progress of electric upsetting process.The geometric accuracy of the finite element model in the optimization scheme was re-evaluated,and the reliability of the upsetting finite element model was verified again.