Research On Multi-Physical Field Coupling And Mechanical Behavior Of High-field Pulsed Magnet

In today's fierce international high-tech competition,the strength of basic scientific research has become a major indicator of a country's scientific and technological,economic and even national defense capabilities.Pulsed magnetic field is an important tool for modern basic scientific research.With the continuous deepening of basic research in condensed matter physics,biomedicine,nanoscience and microgravity,researchers have put forward higher requirements for the strength of pulsed magnetic field.At present,due to the mechanical stability of high-strength pulsed magnets and the life of the magnets,the pulsed magnetic field used to ensure the experimental environment in actual basic scientific research usually runs below 80 T,and pulsed magnets with higher magnetic field strength have not been widely used.High-strength pulsed magnets work in extreme experimental environments such as high voltages,high currents,and extremely low temperatures.They involve the mutual coupling of multiple physical fields such as electric,magnetic,temperature,and stress fields.It is an extremely complex strong electromagnetic system with huge magnets.The electromagnetic stress and the electromagnetic coupling effect in the multi-level coil magnet are the main reasons that limit the further increase of the pulsed magnetic field strength.In response to the above problems,this article aims to achieve a 100 T pulsed strong magnetic field,and conducts a comprehensive research on the design theory and manufacturing process of high-strength pulsed magnets.The research results have broken through the existing technical limitations of pulsed magnet system design,and developed basic science.Research has important academic value and practical significance.The main content and research results are summarized as follows:In terms of the electromagnetic thermal multi-physics coupling of high-strength pulsed magnets,the circuit model,magnetic field model and heat transfer model of pulsed magnets are derived with full consideration of the temperature rise effect,eddy current effect and magnetoresistance effect of the pulsed magnet conductor material,the electromagnetic thermal multiphysics coupling model of high-strength pulsed magnet is established.On this basis,a 100 T magnet three-coil electromagnetic thermal multi-physics coupling analysis was carried out.Through the superposition of the magnetic fields contributed by the inner,middle and outer three coils,a peak magnetic field strength of 100 T was generated in the center hole of the magnet,and the 100 T magnet was analyzed.The resistance,inductance,current and temperature rise of the three coils during the discharge process,and the proportion of the magnetic field contribution of the three coils and the geometry of the inner coil are optimized,and the influence of the stainless steel sleeve on the 100 T pulsed magnetic field is explored.In terms of the mechanical behavior characteristics of the high-strength pulsed magnet,the damage factor of the copper-niobium wire of the magnet conductor material is coupled into the main control equation,and the hybrid strengthening model is used as the strengthening criterion to establish the phenomenological constitutive model of the copper-niobium wire,and according to the modeling method of fiber reinforced material in finite element,the progressive failure model of fiber material is built.On this basis,a study on the mechanical behavior of a100 T pulsed magnet was carried out,the load distribution mechanism in the magnet was pointed out,and the peak stress level of the three coils of the 100 T magnet was analyzed.It was pointed out that the maximum stress in the fiber reinforced layer was 3.2 GPa,which was lower than that of the reinforced layer.The ultimate strength of the material,and the effects of pre-strain and axial pressure on the mechanical behavior of 100 T magnets are explored.A new method of using Zylon/Kevlar hybrid fibers to reinforce 100 T pulse magnets is proposed.This reinforcement method can effectively prevent the conductor layer and the reinforcement layer from shearing.Ultimate strength is analyzed and verified.In terms of the coupling compensation of multi-stage pulse magnets,a new method of connecting a decoupling transformer in series in the multi-stage pulse magnet discharge circuit is proposed to compensate the magnetic field drop caused by electromagnetic coupling between the coils.Taking the 100 T three-coil magnet as the research object,the circuit structure of the decoupling 100 T magnet system is proposed.Through the compensation effect of the decoupling transformer,the magnetic field of the outer and middle coils of the 100 T magnet no longer falls.The electromagnetic thermal multi-physics coupling model of the decoupling transformer is established,and the magnetic field,temperature rise and resistance change of the three windings of the decoupling transformer during the discharge process are explored.The mechanical behavior characteristics of the decoupling transformer are analyzed,and the middle winding of the decoupling transformer is in a toroidal compression state,and a mechanical reinforcement scheme of the decoupling transformer is proposed.In the experimental research of 100 T high-strength pulsed magnetic field,the 100 T threecoil pulsed magnet and decoupling transformer designed in this paper were wound and assembled,the processing technology was explored,and a set of 100 T pulsed strong magnetic field system experimental platform was established.The withstand voltage test of the 100 T three-coil magnet and the decoupling transformer and the positioning test of the center point of the magnetic field were carried out.According to the test principle from single coil to multiple coils,the three coils of the magnet were gradually discharged and tested,and finally the decoupling transformer was connected in series.The entire decoupling 100 T system was jointly tested,and the highest pulsed magnetic field strength was tested to 80 T.The influence of different discharge processes on the 100 T pulsed magnetic field is further discussed,and the influence of the decoupling transformer on the external coil when the coil fails,and the influence of the residual irreversible inductance of the magnet coil on the magnetic field waveform are explored.The feasibility of the 100 T pulse magnet design scheme and the effectiveness of the decoupling transformer are verified,which provides important practical experience and data support for the impact of higher magnetic field strength in the future.