ME 336 Final Exam 3

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Describe a process for forming 8-foot section of gray iron pipe

Cast iron parts are made by sand casting; there may be a permanent core down the center

Describe a process for forming 20-foot long sections of rigid PVC sewer pipe

PVC softened using plasticizers; but sewer pipes are not very soft. PVC heat above Tg and extruded into shape.

Describe a process for forming 20-foot long sections of rigid Cu tubing

Ci tubing extruded using a mandrel & annealed or hot extruded with a steel die

Describe a process for forming 10-foot long sections of rigid stainless steel

Stainless steel pipe extruded and annealed; may need to cast if walls are thick

Describe a process for forming 6-foot long sections of laboratory glass tubing

Heat the glass above Tg and extrude it using a mandrel; die can be almost anything because stresses are not too high

Differences in welding cutting and spark machining

Spark machining uses a dielectric fluid to concentrate the arc into a small region & quench the ejected molten material with a pulsed power supply; arc welding doesn't have the dielectric fluid the power supply is continuous

What does thermal activation have to do with viscoelastic strains in polymeric materials?

viscoelastic polymer molecules are in constant thermally activated motion, and their motion is biased on applied stress

What does Tg have to do with viscoelastic strains in polymeric materials?

Tg is the boundary above which there is sufficient thermal energy constant molecular motion, allowing for viscoelastic strain to occur

The first crystals in a metal casting normally form at

the mold wall because the pre-existing surface reduces the energy barrier to nucleation

Coring may occur above the peritectic and

be followed by surrounding at the peritectic

Die castings tend to produce metal objects having very small grains because

the heat is conducted out through the metal mold very rapidly

The driving force for coarsening is

the reduction in surface area and surface energy.

Investment casting uses

a pattern made from a material with a low melting point

The best alloys for soldering

have low solidification ranges

One of the essential functions of the coating on a welding rod is

to provide a shielding gas

Precipittion-strengthened Al alloys are no considered weldable because

the welding process destroys the favorable precipitate distribution

Arrowhead defect may occur in extruded parts when

the surface regions are strained more than the interior regions

The pressure multiplying factor for frictionless axial upsetting is

one

A metal with a high ductility will have

a large limiting draw ratio when used in a deep drawing operation

Machinability is favored by low

strain rate sensitivity

Cemented carbide cutting tools consist of

WC, TiC, or TaC crystal bound together by cobalt metal

In Taylor's formula for tool life, namely vt^n=C, the exponent, n, characterizes the cutting material. n for high speed steel tools is

smaller than n for coated carbide tools

Ultrasonic machining is really

an abrasive process

Injection molding is suitable for

high-volume production of inexpensive thermoplastic parts

Blow molding is not applicable to simple metals because

metals solidify by a strongly first-order transformation in which a low viscosity liquid changes discontinuously to a rigid solid

A chopped fiber composite can behave like a continuously reinforced composite when

the bonding between fiber and matrix is strong

Bulk molding compounds consist of

chopped fibers in uncured thermoset resins

The green strength of a ceramic powder compact is

mainly due to secondary bonds between ceramic powders and the binder

The isoelectric point is

the pH of an aqueous slurry at which the powder particles have zero surface charge

Mass transport in PVD is

not by forced convection

Cryogenic treatment of tool steels may transform a small amount of retained austenite, but the effect

cannot readily explain practitioners' claims of profoundly enhanced wear resistance

Most of NASA's space based materials processing experiments have

not been run and reproduced well enough to produce good scientific value

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