Manufacturing Processes and Materials Engineering Lecture Notes

Comprehensive question-and-answer review flashcards covering composite materials, casting processes, glassworking, polymer processing, metallurgy, mechanical properties, and surface metrology.

What is a composite material?

A material made of two or more physically distinct phases whose combination produces unique properties different from its individual constituents.

What role does the matrix phase (primary phase) play in a composite material?

It provides bulk form and holds embedded reinforcing material in place.

What are traditional composites?

Natural or long-established composites such as wood and concrete.

What characterizes synthetic composites?

Modern composite systems combining separately-produced components to achieve desired structures and properties.

What constitutes a metal-matrix composite (MMC)?

A metal matrix combined with a second phase (such as ceramic particles or strong fibers) for reinforcement.

What is the purpose of the reinforcing phase (secondary phase) in a composite?

It is an embedded secondary phase intended to improve strength or other material properties.

What is a cermet and what is it used for?

A composite with ceramic reinforcement inside a metallic matrix; used for hardness- and wear-resistant parts.

What are polymer-matrix composites?

Composites consisting of a polymer primary phase reinforced by fibers, particles, or flakes.

What is a laminar composite structure?

A structure consisting of two or more bonded integral layers (e.g., plywood).

What is a sandwich structure and why is it constructed that way?

A composite panel with a thick low-density core bonded between thin outer sheets, built for high strength-to-weight and stiffness-to-weight ratios.

How is the manufacturing process of casting defined?

A process where molten metal is poured into a mold cavity and then solidified to the target shape.

What is pouring temperature in casting?

The temperature of molten metal as it enters the mold.

What is superheat in metal casting?

The temperature difference between the pouring temperature and the metal's solidification-start temperature.

How is pouring rate defined?

The volumetric flow rate of molten metal entering the mold cavity.

What problems can turbulence cause during pouring?

It is irregular, agitated fluid flow that may cause oxide formation, gas entrapment, and mold erosion.

What is fluidity in the context of molten metal?

The ability of molten metal to flow and fill mold cavities before solidification stops further flow.

What is solidification shrinkage?

The volume reduction occurring when metal changes from liquid to solid and as the solid cools.

What is the mushy zone in a solidifying alloy casting?

The region in a solidifying alloy casting where solid dendrites and trapped liquid co-exist.

Which type of casting mold must be destroyed to remove the solidified part?

Expendable mold.

Which component of a sand casting mold creates internal holes and cavities?

Core.

Which casting component supplies additional molten metal to compensate for solidification shrinkage?

Riser.

Which property of molding sand allows gases to escape through the mold?

Permeability.

Which casting process uses a wax pattern to produce intricate metal parts?

Investment casting.

Which process uses a polystyrene foam pattern that vaporizes during pouring?

Lost-foam casting.

Which casting process forces molten metal into a metal mold under high pressure?

Die casting.

Which permanent-mold process produces hollow castings by draining out the remaining liquid metal after partial solidification?

Slush casting.

Which casting process uses a rotating mold to distribute molten metal toward its outer region?

Centrifugal casting.

Which sand-mold property allows the mold to give way as the casting contracts during cooling?

Collapsibility.

What is the characteristic structure of ordinary glass?

Vitreous.

What material is the principal glass-forming ingredient in common glass?

Silica.

What is the term for the batch of starting materials prepared for melting in glassworking?

Charge.

Which glass-shaping process is commonly used for mass-producing relatively flat products such as dishes and bakeware?

Pressing.

Which process produces continuous glass products by pulling the softened material?

Drawing.

Which glassworking process shapes hot glass between rollers to produce flat products?

Rolling.

Which heat treatment process reduces undesirable residual stresses in formed glass?

Annealing.

Which treatment rapidly cools the surfaces of heated glass to develop beneficial residual compressive stresses?

Tempering.

Which finishing operation removes material to improve the shape or dimensions of glass edges and surfaces?

Grinding.

Why is glass generally stronger when its surfaces are under compression?

Because of crack resistance.

What property measures a polymer melt's resistance to flow?

Viscosity.

What type of fluid behavior describes polymer melts whose apparent viscosity decreases as shear rate increases?

Pseudoplastic.

What is die swell in polymer processing?

The expansion of a polymer extrudate after leaving a die.

Which process produces continuous plastic products by forcing polymer melt through a die opening?

Extrusion.

In a single-screw extruder, which section homogenizes the melt and builds pressure before it reaches the die?

Metering section.

Which extrusion defect produces a rough surface because of excessive stresses near the die entrance?

Melt fracture.

Which process produces hollow plastic products by expanding a softened tube or preform against a mold using internal pressure?

Blow molding.

Which process shapes a heated thermoplastic sheet using vacuum, pressure, or mechanical assistance?

Thermoforming.

Which molding process places a charge directly into a heated mold, where it is compressed and cured?

Compression molding.

Which defect appears when molten plastic solidifies before completely filling the mold cavity?

Short shot.

What happens in a substitutional solid-solution?

Other type atoms take the regular atom-spots inside the crystal lattice.

What are the two major categories of metals?

Ferrous (with iron) and non-ferrous (no iron).

Which material has good workability and ductility, and contains no carbon?

Pure non-ferrous metal such as pure copper or pure aluminum.

Where are alloying elements located inside an alloy?

Either replacing host-metal atoms (substitutional) or fitting in gaps between them (interstitial).

What is thermal shock, and when does it occur in metals?

Cracking caused by sudden uneven temperature change; it usually happens during rapid cooling.

What is the main difference between traditional ceramics and new/advanced ceramics?

Traditional ceramics use natural raw materials, whereas advanced ceramics use specially-processed high-purity synthetic powders.

What are examples of common ceramic materials?

Aluminum oxide, silicon carbide, and silicon nitride.

What structural feature describes glass?

An amorphous (non-ordered, non-crystalline) solid structure.

Why are some ceramic products shaped before heating?

Because they become very hard and brittle once fired, meaning you cannot easily reshape them afterwards.

What happens during recrystallization in metals?

New strain-free grains form, replacing deformed grains when heated above the recrystallization temperature.

What are the key characteristics of a thermosetting polymer?

It permanently hardens when heated and cannot melt again after curing.

What type of material is used for flexible hoses?

Elastomer / rubber-type polymer.

What does a glass-transition mean for polymers?

The temperature range where a hard-brittle polymer turns softer and more flexible.

What is the purpose of molecular arrangement in polymer structures?

It decides the polymer's strength, flexibility, and heat-resistance properties.

How is an atom defined?

The smallest basic unit that makes up all materials.

What is a valence electron?

Electrons in an atom's outer shell that help form bonds between atoms.

How is an ionic bond described in the lecture notes?

Type of atomic bond where atoms share electrons with each other.

What is a covalent bond?

A bond where atoms share electrons with each other.

What is a metallic bond?

A special bond that holds metal atoms together.

What is crystallization?

The process where atoms arrange themselves into an ordered crystal structure.

What is a lattice?

A regular repeating-pattern framework inside a crystal.

What does FCC stand for and what is it?

Face-Centered-Cubic, a common crystal structure found in many metals.

What is a vacancy in a crystal structure?

An empty spot where an atom is missing from the crystal lattice.

What occurs during elastic deformation?

Temporary shape change; the material returns to its original form after force is removed.

How is stiffness defined?

A material's resistance to being bent or deformed.

How is strength defined?

The ability of a material to resist breaking under applied force.

What is ductility?

The ability of a metal to stretch into thin wires without cracking.

What does hardness measure?

A measure of how resistant a surface is to scratches or dents.

What does a stress-strain curve show?

A graph showing how a material responds to applied force and deformation.

What is hot hardness?

The ability of a material to stay hard even at high temperatures.

What is forging?

Shaping metal by hammering or pressing it.

What is the recrystallization temperature?

The temperature at which a worked metal starts forming new undamaged grains.

What is hot working?

Shaping metal at a temperature above its recrystallization point.

How is density defined?

The mass of a material per its unit volume.

What is thermal expansion?

The tendency of a material to grow slightly larger when heated.

How is melting point defined for a pure metal?

The fixed temperature where a pure metal changes between solid and liquid states under given conditions.

What is the solidus temperature?

The temperature at the very start of melting for an alloy.

What is the liquidus temperature?

The temperature where an alloy becomes completely liquid.

What is specific heat?

The amount of heat needed to raise one unit mass of material by $1^\circ$.

What is thermal conductivity?

The ability of a material to let heat pass through it.

What is mass diffusion?

The slow movement of individual atoms from one region to another inside a solid material.

What is electrical resistivity?

A material's inherent property that opposes the flow of electric current.

What is electroplating?

A process that coats a part with a thin metal layer using electric current.

How is tolerance defined?

The allowable small deviation from a part's exact specified size.

What is measurement?

The act of finding the real dimension or size of an object.

What is gaging?

Checking whether a part falls within its allowed size-limits using special tools.

How is precision defined in measurement?

How consistent repeated measurements are with each other.

What does form refer to in manufacturing inspection?

The overall geometric shape of a surface or finished part.

What is waviness on a machined surface?

Broad, gentle wave-like undulations across a machined surface.

What is surface integrity?

The condition of a part's outer layer, including hidden damage caused by processing.

What is machining?

Cutting or removing material to reach precise final dimensions.

What components make up surface texture?

The combined surface features: roughness, waviness, and overall form.