Numerical Simulation On The Effects Of Normal Pressure On Deformation Of Superalloy Thin-walled Sheet

In areas such as automotive, aerospace, structural light-weighting has been themain development direction of sheet metal forming, therefore the light structuralmaterials with high strength has received considerable attention in recent years. Thewidely used ni-base superalloy materials was chosen as the experimental material forthis dissertation. It has excellent capacity in resistance to high temperture, But theproportion of Ni is big. In order to lose weight, the wall thickness of the sheet must beselected very thin. At the same time, the ni-base superalloy materials has a large yieldstrength. It is difficult to use the conventional forming method to process parts. So themain contents of this dissertation is to study how to improve the formability of thethin-walled difficult forming parts.This paper is based on the basis of research work of normal pressure can promotethe formability of the sheet metal to analyze the normal pressure how to affect thedeformation behavior of the ni-base superalloy sheet metal. Angle from the shapeanalysis of the changes and the feasibility of technology. The bulging method was takento analyze normal pressure how to affect the sheet metal. The overlapped sheet withstrengthening effect was loaded to the forming sheet, The normal pressure plays animportant role to the forming sheet.Using rigid punch, polyurethane rubber and viscousmedium as the punch.Firstly, the sheet bulging process which considered the effects of normal pressurewas analyzed. It was conclued the factor to affect the normal pressure by the concept offormability increase factor. In this paper, viscous pressure bulging of sheet metal withthe overlapped sheet is proposed according to the practical limitations to the influenceof through-thickness normal stress on sheet metal formability.It is shown that themagnitude and distribution of transverse normal pressure are dependent on theoverlapping sheet metal strain hardening exponent, strength coefficient and thicknessvalues.Secondly, the FEM analysis of overlapped GH4169in different forming methodswere carried out. Using rigid punch, polyurethane rubber and viscous medium as thepunch and finite element analysis software as DEFORM-2D and ANSYS/LS-DYNA toanalyze stress, stress deviatoric and strain state of the overlapped sheet viscous pressurebulging process. It is shown that the magnitude and distribution of normal pressure aredependent on the thickness and material strength of overlapping sheet.Finally, the experiment was taken to verify the FEM results. GH4169is chosen asthe material investigated, the overlapping sheet is austenitic stainless steel1Cr18Ni9Ti.The VPB test of overlapped GH4169was carried out. To analyze the strain of sheet of different dome height, we found out that normal pressure can affect strain distribution.