Influence Of Blunt Punching’s Tools On Texture And Residual Stress Of Silicon Steel Lamination

Non-oriented silicon steel is widely used in iron cores of various motors,generators and transformers because of its good magnetic conductivity and low core loss(iron loss).In the production process of automobile drive motor,in order to manufacture iron core sheet with high efficiency,punching technology is used.However,punching will introduce residual stress at the cutting edge of the sample,resulting in the evolution of texture at the cutting edge,which will affect the magnetic properties of the iron core.At the same time,the punching tool will inevitably be worn in industrial production.Therefore,there is great theoretical value and practical significance to deeply study the influence of blunt punching tools on the residual stress distribution and texture evolution at the cutting edge,so as to provide a theoretical basis for regulating the texture and residual stress distribution of materials in the manufacturing process of motor iron core.In this thesis,tensile specimens with different stress states are designed based on stress triaxiality,and tensile experiments are carried out with electronic universal material testing machine to obtain the stress-strain curves of different stress states,then the parameters of Johnson cook plasticity model and damage criterion are fitted.Secondly,the finite element simulation model of blunt punching tool is established by ABAQUS.Combined with the results of finite element simulation and EBSD,the deformation process of cutting edge is deeply studied.The results show that the blunt punching tool will form a large bending area in the cutting edge of non-oriented silicon steel.The bending area can be divided to three distinct areas: a highly deformed area,a bent area with moderate deformation and a non-deformed area.And the closer to the cutting edge,the greater the plastic deformation.Then,combined with the finite element simulation analysis and nano-indentation test results,it is confirmed that punch tools with high wear will form residual tensile stress at the cutting edge,and the distribution of residual tensile stress depends on the wear degree of the punch tools and the chamfer size of the punch.Finally,with the help of EBSD,the microstructure evolution and texture evolution of cutting edge are analyzed,and the deformation mechanism and texture evolution mechanism of cutting edge are revealed.The results show that the main deformation mechanism of medium bending zone and non-bending zone at the cutting edge is dislocation slip,and the grain orientation mainly develops to {211}<uvw>;The deformation mechanism of high strain region is dislocation slip and the formation of micro shear bands,which mainly forms {110} fiber texture.