Chapter 6 – Sheet-metal Forming

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A cup is subjected to three different types of deformation. Cup wall Punch region Biaxial Flange Biaxial Stresses and deformation in a section from a drawn cup Triaxial As the metal being drawn, • Change in radius • Increase in cup wall Thickness profile of drawn cup Clearance between the punch and the die > 10-20% thickness. • Metal in the punch region is thinned down biaxial tensile stress. • Metal in the cup wall is subjected to a circumference strain, or hoop and a radial tensile strain. • Metal at the flange is bent and straightened as well as subjected to a tensile stress at the same time. Suranaree University of Technology Tapany Udomphol Jan-Mar 2007
Redrawing • Use successive drawing operations by reducing a cup or drawn part to a smaller diameter and increased height – known as redrawing. Examples: slender cups such as cartridge case and closedend tubes. 1) Direct or regular redrawing : smaller diameter is produced by means of a hold-down ring. The metal must be bent at the punch and unbent at the die radii see Fig (a). Tapered die allows lower punch load, Fig (b). 2) Reverse or indirect redrawing : the cup is turned inside out the outside surface becomes the inside surface, Fig (c). Better control of wrinkling and no geometrical limitations to the use of a holddown ring. Suranaree University of Technology Tapany Udomphol Jan-Mar 2007
Page 1 and 2: Sheet-metal Sheet metal forming Sub
Page 3 and 4: Introduction • Sheet metal formin
Page 5 and 6: Classification of sheet metal formi
Page 7 and 8: a) Uniaxial b) Biaxial c) Hydrostat
Page 9 and 10: Deformation geometry Plane stress P
Page 11 and 12: Forming equipments Forming equipmen
Page 13 and 14: Actions of presses (according to nu
Page 15 and 16: Tooling Basic tools used with a met
Page 17 and 18: Schematic diagram of a die set A di
Page 19 and 20: Progressive forming • Punches and
Page 21 and 22: Rubber hydroforming • Using a pad
Page 23 and 24: Clamp Bending and contouring Form b
Page 25 and 26: Spinning processes • Deep parts o
Page 27 and 28: Shearing and blanking Shearing (a)
Page 29 and 30: Blanking : The shearing of close co
Page 31 and 32: Shaving : A secondary shearing or c
Page 33 and 34: Bending The bend radius R = the rad
Page 35 and 36: Effect of b/h ratio on ductility
Page 37 and 38: For aluminium alloys and austenitic
Page 39 and 40: Stretch forming • Forming by usin
Page 41 and 42: Diffuse necking In biaxial tension,
Page 43: Punch Holddown ring • It is best
Page 47 and 48: Drawability (deep drawing) Drawabil
Page 49 and 50: Practical considerations for round
Page 51 and 52: The plastic strain ratio R measures
Page 53 and 54: Forming limit criteria • Tensile
Page 55 and 56: The forming limit diagram • The s
Page 57 and 58: Defects in formed parts Springback
Page 59 and 60: Stretcher strain in low-carbon stee

Chapter 6 – Sheet-metal Forming

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