Sheet Metal Forming, Forging and Extrusion

Using a ball-peen hammer, strike the surface of aluminium sheets of various thickness until they develop a curvature. Describe your observations about the shapes produced.

The thinner the sheet, the bigger the curvature. If the sheet is too thin, the sheet will be bent

Can SPF/DB and creep age sheet metal forming processes be done at room temperature? Explain your answer?

No, because superplasticity of materials, diffusion bonding and creep of alloys can generally occur at elevated temperatures, except for a few metals, such as mercury and polymers.

At what temperatures, elevated temperature or room temperature is shot peening forming conducted? Why?

Shot peening forming is normally conducted at room temperature as the residual compressive stress may be lowered or eliminated at elevated temperatures.

Why are forging and extrusion commonly used in aerospace industry, but not casting

Forgings have the advantages of better strength, toughness, surface finish, and dimensional accuracy. Forgings have the advantages of economic viability (depending on lot size), good mechanical properties, and the ability to produce complex parts with good surface finish. Forgings are available in a wide variety of sizes and materials, and the equipment for forging is widespread in industry

What are the functions of flash in close-die forging?

Flash accommodates extra metal, Flash presents a severe constrain on any more outward metal flow due to the increased frictional resistance. Thus, the metal flows to other direction in the cavity and fully fills the cavit

Compared with extrusion of aluminium alloys, during extrusion of titanium alloys, why are the billets heated to higher temperatures

Because titanium alloys have higher strength and lower ductility due to their HCP (alpha-phase) and BCC (beta-phase) lattice structure

Compared with extrusion of aluminium alloys, during extrusion of titanium alloys, why are Cold die and press tooling used?

Cold die and press tooling to ensure the alloy billets to be deformed

Why is lubricant always used during metal extrusion in aerospace industry?

Aerospace materials are normally high strength materials and are harder to be extruded. Flow stress of such materials during extrusion increases very rapidly with increase in strain rate.

Lubricant one

Lubrication of the outer periphery of the billet to lubricate billet–container interface

Lubricant two

Lubrication at the front of the die to lubricate die bearing-extruding metal interface

SPF/DB

is used to make complicated structure, such as the Integrally stiffened structure, the sandwich structure.

SPF

large metal panels with limited shape change or curvature

CAF

large curved sheet.

SF

Axially symmetrical parts

Stretch forming

to make parts with big shape changes