| Cylindrical drawing is a metal forming method that uses tools to make a panel changes into a cylindrical,which conducts popular applications in manufacturing now.In the process of deep drawing,wrinkling,fracture and thinning are important factors which effects the quality of forming parts.With the increasing demand for the quality of drawing parts,the research of variable blank-holder force and variable blank-holder force device has become a focus in the field of drawing process.The text focuses on cylindrical drawing and derives the critical wrinkling stress and fracture blank-holder force.Besides,numerical simulation software has been used to analyze the relationship among different blank-holder force and thickness reduction.In addition,more reasonable blank-holder style is proposed and a variable blank-holder force device is designed.Main research content and result are shown as following.(1)By establishing wrinkling model and mathematics formulas,cylindrical blank-holder force of restraining cylindrical wrinkling is derived according to energy approach.Besides,fracture model of cylindrical is established.According to the ultimate stress and drawing force of processing panel,critical blank holder force formula which used to restrain cylindrical fracture is derived.Combined with concrete case,the concrete scope of restraining wrinkling and fracture is confirmed.(2)By establishing finite analysis model,using shell elements to mesh the established model.Then,use surface to surface,apply force and constraints.Next,the maximum and the minimum critical blank-holder load has been obtained according to theoretical analysis.Finally,change regulation has been analyzed in the study.(3)By analyzing the variation situation when applying different constant blank-holder force,simulation scope has been confirmed.In the scope,traditional blank-holder loading form(crescendo,decrescendo and exponential type)has been simulated.Besides,wall thinning and material flowing during drawing has been analyzed.In addition,the effect of different constant blank-holder force acting on drawing has also been analyzed.Additionally,new blank-holder loading way has been proposed and which has been verified by simulation.At last,the advantages among the new blank-holder force and other traditional blank-holders has been summarized.(4)According to the new blank-holder curve proposed above,a mechanical drawing tool device which can obtain new blank-holder force curve has been designed.Besides,the parts of the device has been designed.Eventually,two dimension and three dimension models of the designed device has been established and feasible analysis has been conducted.Above all,the text establishes an analysis model of cylindrical drawing force and proposed the upper and lower critical blank-holder force calculation formula based on wrinkling and fracturing.Besides,finite analysis model of cylindrical has been established and the research obtains the variation situation of wall thickness.In addition,the effect that traditional blank-holder loading way acts on thinning of wall thickness has been obtained.Additionally,the study obtained reasonable blank-holder force curve based on reasonable wall thickness hypothesis and designs corresponding mechanical variable blank-holder device.The result of the study contains theoretical and applied value to increase drawing quality of cylindrical in some extent. |
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