Study On Numerical Simulation And Parameter Optimization Of Electric Upsetting Process For Marine Diesel Gas Valves

The gas valve electrothermal upsetting process is an electro-thermal-mechanical multifield coupling process.It is difficult to coordinate control of various parameters in a multifield coupling environment.How to systematically and effectively obtain reasonable matching process parameter schemes has been the focus of research content.The trial and error method is often used in the experimental research,which has a long period and high cost.In particular,the current development of engines toward high stability,high power,and large size requires the development of high precision,high quality,and large rod crosssections.At the same time,the materials need to have high toughness,heat resistance,and corrosion resistance.However,the large-size gas valve electric upsetting parts are timeconsuming,the cost of consumables is higher,and the processing is more difficult.Based on the qualitative analysis of the electric upsetting process,this paper aims at the nickel-based superalloy Nimonic 80 A material has high deformation resistance under high temperature conditions,narrow forming temperature range,electric upsetting process parameter adjustment has more important characteristics on its deformation results,From the "temperature control" and "shape control",macro and micro multi-scale multi-scale use of finite element simulation technology to build a large size,long rod diameter gas valve blank local electric heating upsetting analysis platform,its forming mechanism,process parameters Research has been conducted on optimization and other aspects.It provides a theoretical basis for guiding the actual production to find the optimal parameter allocation scheme and formulating accurate process specifications.The full text work is summarized as follows:(1)The process of electric upsetting is a highly nonlinear multi-field multi-scale dynamic coupling deformation,and the inconsistency between the parameters is prone to defects.Through a comprehensive and in-depth study of the electric upsetting process,the corresponding relationship between each process parameter and product defect is qualitatively analyzed in combination with the analysis of the failed product,and the main parameter types are determined according to the effect and degree of influence.(2)Analyze the thermo-electric coupling,thermo-mechanical coupling principle and rigid-plastic model theory in the finite element solution,and combine the specific forming characteristics to establish the finite element analytical equation of the multi-field interactive coupling analysis of the electrothermal upsetting process,clarify the meaning ofeach parameter in the analysis and the basis for its selection,and provide a solid theoretical basis for the establishment of the electric upsetting simulation model.(3)For the large-size valves of low-speed marine diesel engines,on the basis of solving the key problems of multi-field direct coupling in simulation,material parameter construction,current density and upsetting force boundary condition loading,contact resistance between blank and anvil,Using MSC.Marc.advanced nonlinear finite element analysis software and secondary development subroutines,a properly simplified multi-field and multi-scale electrothermal upset forming analysis model is established to realize the dynamic coupling simulation of the entire upsetting process.(4)Carry out finite element simulation of the electric upsetting process of Nimonic80 A high-temperature nickel-based alloy material,based on the simulation results,quantitatively analyze the main process control parameters,and study the blank deformation process under constant current density and upsetting pressure The laws and characteristics of temperature,equivalent strain rate,forming size and grain structure change.And analyze and explore the occurrence of defects in the process.(5)To improve the defects generated in the forming process,a multi-stage loading method of current density and upsetting pressure is proposed.The best parameter matching scheme obtained by simulation is used for the test,and the obtained valve products are dissected and inspected,and the simulation results are compared with the parameters such as the maximum forming temperature,the shape of the heading,the aspect ratio,and the grain size as evaluation indicators verification.Provide an effective reference for formulating the optimal process specifications for actual production.