Research On The Overall Formability Of Tailor Rolled Blanks

Two of the major issue that the automotive industry must face are energy saving and environment protection.In order to solve these two problems,researchers have proposed many methods and one of them is auto lightweight technology.Using Tailor Rolled Blanks(TRB)to manufacture automotive parts is an effective way to realize auto lightweight.The core technology of producing TRB is Variable Gauge Rolling Technology.During the rolling process,variable thickness sheets can be produced by online adjusting the roll gap.Nowadays,the production process of TRB is pretty mature.But there are many aspects to be researched in the application of TRB such as the forming properties,stamping die design and springback of TRB.The research object of this paper was TRB with thin zone of 1.0 mm,thick zone of 1.2mm and transition zone of 100mm length.The transition zone of Tailor Rolled Blanks was divided into six parts by the method of discretization and each part was substituted by equal thickness sheet.Based on experimental research,the overall formability of TRB was studied.The main research results are as follows:(1)The measured mechanical properties were used to qualitatively evaluate the forming property of the sheets.The conclusion drawn from analyzing the mechanical properties was that forming property was worst at the thickness of 1.6mm,best at the thickness of 1.2mm.The forming property was getting better along with the decrease of thickness while the thickness of sheet was less than 1.6mm.The forming property was getting better along with the increase of the thickness while the thickness was more than 1.6 mm.(2)Hole expanding rate,Conical cup value and Cupping value were used to evaluate the flanging performance,drawing property and bulging capability.The experiment results showed that the flanging performance was getting worse along with the increase of the thickness;the drawing property was better when the plasticity was better;and the bulging capability of the sheets increased while the thickness increases.(3)Forming Limit Diagrams of the different thickness sheet was tested and drawn in the same coordinate system.The forming limit was consistent with the plasticity of the sheet.The sheet with thickness of 1.2mm had highest forming limit and 1.6mm had lowest forming limit.During stamping process,FLD can be used to arrange the thickness distribution and optimize stamping process.(4)Buckle resistance under several experimental conditions of the different thickness sheet was tested.The experiment results showed that the buckle resistance increased then decreased with the increase of thickness.Sheet with thickness of 1.8 mm had best buckle resistance and 1.4 mm had worst buckle resistance.(5)U-shape parts of TRB were studied.The experiment results showed that as for the researched TRB sheets in this paper,springback angle in thin area was less than that in thick area.The springback angle increased with the increase of blank holder force and the size of the sheet.The springback angle was not germane to punch speed.(6)TRB square boxes was made by self-designed TRB drawing molds and the influence of drawing forming under several blank holder force was studied.