Metal forming - Chapter 15: Fundamentals of Metal Forming...

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Chapter 15: Fundamentals of Metal Forming
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Deformation processing Exploit ‘plasticity’ – ability of solids to deform and flow without deterioration of properties Processing entirely in solid state Little material wastage Requires large forces – high machine tooling costs large production volumes may be required to justify costs Processes include bulk flow, simple shearing, or compound bending
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States of Stress
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Stresses in Metal Forming Stresses to plastically deform the metal are usually compressive Examples: rolling, forging, extrusion However, some forming processes Stretch the metal ( tensile stresses) Others bend the metal ( tensile and compressive) Still others apply shear stresses
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Forming Operations
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Forming Operations
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Forming Operations
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Bulk Deformation Processes Thicknesses / cross-sections are reduced considerably or shapes massively altered during processing
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Basic bulk deformation processes: Rolling Reduce thickness / cross-section using compressive forces exerted by rolls Rolls rotate at speeds faster than incoming material feed speeds friction propels material forward Variants: (a) Hot Rolling rolling uniformly heated sample Instantaneous recrystallization
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Basic bulk deformation processes: forging Induce plastic deformation through localized compressive forces applied through dies (i.e. hammers, presses or special machines) Hot (T > Recrystallization temperature) or Cold (T < Recryst. temp.)
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Basic bulk deformation processes: Extrusion Metal is compressed and forced to flow through a suitably shaped die to form a product with reduced cross-section Commonly used as a ‘Hot’ (T > Recrystallization temperature) process Commonly used for low yield strength metals (Al, Cu, Mg and their alloys)
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Basic bulk deformation processes: Wire / Rod / Tube Drawing Similar to extrusion , the difference being that we ‘pull’ the metal through an orifice here as opposed to ‘pushing’ a metal through an orifice as in extrusion
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Sheet Metalworking Deformation such that the thickness and surface area remain relatively constant High surface area-to-volume ratio of starting metal loses heat rapidly operations performed ‘cold’ The clearance between die and punch is small ( < 5-10% of thickness of metal) metal responds by localized shear Often called pressworking because presses perform these operations Parts are called stampings Usual tooling: punch and die
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Basic sheet metalworking operations: bending Plastic deformation of metals about a linear axis with little or no change in surface area
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Basic sheet metalworking operations: wire/rod/tube drawing Family of operations where plastic flow occurs over a curved axis and the sheet is formed into a recessed three-dimensional part with a depth several times the thickness of the metal
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Basic sheet metalworking operations: shearing
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Forming Processes: Independent Variables Those aspects of the process over which the
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This note was uploaded on 01/19/2012 for the course IE 230 taught by Professor Xangi during the Spring '08 term at Purdue University-West Lafayette.

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Metal forming - Chapter 15: Fundamentals of Metal Forming...

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