Research On Optimizing Technology Of Laser Melt Deposition With Synchronous Electromagnetic Field

Laser melting deposition is a technology combined with high power laser technology and CAD/CAM technology which can realize the rapid and near net shape forming of metal parts with complex structure.It can not only reduce the product development cycle,but also maximize the savings of raw materials significantly.However,due to the lack of process standards,defects such as internal pores and cracks often occur in the workpiece,which seriously restrict its application in a wider field.The alternating magnetic field can induce the electromagnetic force in the nearby conductor and thus make the conductor plastic deformation.This principle has been widely used in the field of metal forming.Drawing on electromagnetic forming technology,this paper aims to make workpiece plastic deformation using induced electromagnetic force to the tensile strain of the workpiece due to cooling shrinkage,so as to reduce the residual stress,suppress the thermal crack growth.The primary work of this paper is summarized as follow:(1)Analysed the mechanism of the residual stress formation and the mechanism of the electromagnetic field enhancing laser melting deposition,including reducing the residual stress and refining the dendrite structure.(2)Simulated the process of laser melting deposition assisted by electromagnetic field using ANSYS.The distribution of residual stress in time and space with and without electromagnetic field as well as its change regulation loaded with different electromagnetic force is studied.(3)Built test device and carried out the single pass and single layer experiment.Prepared the metallographic sample and analyzed the internal microstructure.(4)Carried out the singal pass and multilayers experiment on the basis of single pass single layer experiment,multi passes multi layers experiment was carried out.The residual stress on the surface of the workpiece was measured by X-ray diffraction,and the residual stress in the depth direction was measured with the method of electrolytic polishing.In this paper,the coupling of three fields of temperature,stress and electromagnetism are realized by programming language APDL.Using the simulation model,not only the distribution of residual stress is studied,but also the influence of electromagneticfield on the residual stress is analyzed.The simulation results are in good agreement with the later experiments,laying the foundation for further research in the later stage...