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1、Chapter 5 DRAWING,Main contents: Deformation feature of drawing; Mechanic analysis of drawing; Problems arising in drawing; Drawing of cylindrical work-piece; Drawing of other revolving work; Drawing of boxes; Other drawing methods ; Assistant procedures of drawing.,Key points Drawing of cylindrical
2、 work-piece. Difficult parts: Mechanic analysis of drawing,New words,deep drawing/深拉深, blank holder/压边圈, cylindrical/圆柱形的，cup/杯形件， conic /锥形的, box-shaped/盒形的，rectangular/矩形的 ironing drawing/变薄拉深,flange/凸缘, wrinkle/起皱 axisymmetric geometry/轴对称几何图形, die radius/凹模圆角半径, radial/径向的, punch corner radius/凸
3、模圆角半径, redundant/多余的 longitudinal/纵向的，relative thickness of material/相对厚度， drawing ratio/拉深比， blank diameter/毛坯直径, number of successive draws/ 拉深次数， add for trimming/修边余量,Deep drawing is the process by which a punch is used to force sheet metal to flow between the surfaces of a punch and a die. A fl
4、at sheet is formed into a cylindrical-, conical-, or box-shaped part. 1. Types 2. Deformation feature 3. Stress and strain state,5.1 Deformation features of drawing,1. Types,a)Pure drawing: without a reduction in the thickness b)Ironing drawing: with a reduction in the thickness,Grid method: Damage
5、sites: bottom radius Thickness: upper becomes thicker lower becomes thinner Hardening: upper serious bottom light Changes in grid: bottom no change wall from sector to rectangle,2. Deformation feature,Four parts: deformation zone(the flange) D-d transition zone -2 die radius force transmitting zone-
6、the wall transition zone-2 punch corner radius non-deforming zone-the bottom,3. Stress and strain state,5.2 Mechanic analysis of drawing,Stress analysis of deformation zone Stress distribution in deformation zone Varying law of maximum radial stress and maximum tangential stress Stress analysis of t
7、ransmitting zone of wall,Equations of equilibrium Plastic condition Boundary condition when,1. Stress analysis of deformation zone,2. Stress distribution in deformation zone,Characteristic point:,3.Varying law of maximum radial stress and maximum tangential stress,similar with hardening law,4. Stres
8、s analysis of transmitting zone of wall,5.3 Problems arising in drawing,Wrinkle Fracture Hardening,1.1 Generate deformation zone 1.2 Affecting factors Relative thickness t/D0,wrinkle Deformation degree m=d/D0,wrinkle ,1. Wrinkle,1. Wrinkle,1.3 Preventing measures drawing ring(blank holder) taper die
9、 : make flange small reverse drawing,1.4 Conditions of no wrinkles Flat die: t / D0(0.090.17)(1-m) Taper die: t / D00.03(1-m),1. Wrinkle,2. Fracture,2.1 Stress analysis of cylindrical surface flange deformation resistance friction caused by drawing ring die radius friction resistance die radius bend
10、ing resistance sum: efficient tension strength in the wall,2. Fracture,2.2 Condition of no fracture 2.3 Affecting factors 1) deformation degree: mfracture 2) properties of materials: bfracture 3) size of parts : d , t fracture 4) radius of die and punch: rp ,rdfrature 5) lubrication: benefit and har
11、mful,5.4 Drawing of cylindrical work-piece,1. Blank 2. Drawing coefficient 3. Number of drawing 4. Drawing force and drawing power 5. Features of subsequent drawing 6. Determination of drawing die size 7. Homework,1. Blank,Principle: constant surface area,2. Drawing coefficient,2.1Definition and mea
12、ning m=d / D0 (or dn / dn-1) an index measuring deformation degree of drawing 2.2Limit drawing coefficient m The maximum drawing coefficient where no wrinkle and no fracture occur. 2.3Affecting factors Material: Die : ZRdRp,m Drawing condition: blank holder, Hardeningm1m2mn; lubrication,3. Number of
13、 drawing,mm1 need more than one time drawing Examples,n=log dn / m1D0 / log mn+1,4. Drawing force and drawing power,4.1blank-holding force Q = A p 4.2drawing force theoretical formula F=A empirical formula F=kdtb 4.3choose press F = Fl + Q 4.4 drawing power,5. Features of subsequent drawing,Inhomoge
14、neous of blank thickness and mechanical properties ; Constant deformation zone ; Maximum drawing force occurs in later period ; Fracture occurs in the later period ; Wrinkle is not serious, because the subsequent drawing is more stable than the first drawing ; Drawing coefficient is large, because o
15、f hardening .,6. Determination of drawing die size,6.1punch rp , dp ,(p93) die rd ,Dd , blank holder 6.2clearance Z 6.3structure of die and punch,Homework,The workpiece shown in Fig.1 is made of 08 carbon steel sheet with the thickness of 2mm (1.5mm). Calculate the blank diameter before drawing, the
16、 number of operation, dimension of work piece after each operation, and the force need Judge whether a blank holder is needed and choose the press.,Fig.1 Final workpiece,Homework,5.5 Drawing of other revolving works,Cylindrical works with flange Cylindrical works with steps Taper works Spherical works,1. Cylindrical works with flange,1.1 Blank(5 parts):constant surface area 1.2 Drawing coefficient relative flange diameter,
