Bulk Deformation Flashcards
Plastic deformation
Occurs between yield stress (Y) and ultimate tensile strength, area of permanent deformation before cracking starts
Cold forming
Room temp
Good surface finish
Strain hardening = better strength
Warm forming
Between room temp & recrystallization temp
Hot forming
Above recrystallization temp
Isotropic
For brittle metals
Isotropic properties
Properties that are uniform in all directions
Open die forging
Work is compressed between two dies
Impression die forging
Material squished between dies in the inverse shape of the part
Isothermal/hot die forging
Dies are heated to recrystallization temps
Low flow stress allows easy material flow into cavities
Heading
Used to form heads on rods, pressure provided by a punch at the end of the rod
Piercing
Punches a shaped indent into piece
Cogging/drawing out
Bar fed through converging dies to reduce thickness
Fullering
Distributes material away from a certain area
Edging
Gathers material into a certain area
Roll forming
Material is fed through grooved rollers
Skew rolling
Forms ball bearings using offset corkscrew rollers
Rolling
Compressive forces are used to reduce the thickness of a lone workpiece
Hot rolling
Recrystallization when cooling with new smaller grains
Low internal stress = uniform grains
Cheaper
Cold rolling
Strain hardening = stronger
Better dimensional tolerance
More expensive
Flat rolling defects
Wavy edges
Zipper cracks (in middle)
Edge cracks
Alligatoring
Ring rolling
A thick ring is expanded into a thinner ring with a larger diameter
Thread and gear rolling
Cold forming using threaded rollers
Stronger than a machined thread
Rotary tube piercing
Creates a cavity in the center of the workpiece using compression (which leads to tensile stress)
Types of extrusion
Direct extrusion (piece moves towards die)
Indirect extrusion (die moves towards piece)
Hydrostatic extrusion (piece pushed with fluid pressure)
Impact extrusion (just smack it through)
Drawing (piece pulled through converging die)
