ENME502 Engineering Materials I Practice Flashcards

Comprehensive vocabulary flashcards covering material structure, mechanical properties, polymers, composites, ceramics, and corrosion as outlined in the ENME502 test notes.

Subatomic structure

The structure level looking at details less than $0.2\,nm$.

Atomic structure

The structure level looking at details between $0.2$ and $10\,nm$ to explain bonding.

Microscopic structure

The structure level ($1-1000\,um$) used to explain grains, phases, defects, pores, and fibres.

Bulk structure

The structure level greater than $1\,mm$ explaining the whole component's behaviour.

Metallic bonding

Positive metal ions surrounded by free-moving electrons, providing good conductivity and ductility.

Ionic bonding

Bonding involving electron transfer that creates positive and negative ions, typically resulting in hard, brittle, and insulating materials.

Covalent bonding

Bonding where atoms share electrons in directional bonds, resulting in strong, high melting point, and often brittle materials.

Secondary / Van der Waals bonding

Weak attraction between molecules or chains typically found in polymers and molecular solids.

Crystalline structure

Atomic arrangement where atoms repeat in an ordered pattern over long distances.

Amorphous structure

Atomic arrangement with no long-range repeating order, such as glass.

FCC (Face-centred cubic)

A close-packed crystal structure with atoms at cube corners and face centres; examples include aluminium, copper, and nickel.

BCC (Body-centred cubic)

A crystal structure with atoms at cube corners and one atom in the centre; not close-packed; examples include alpha iron and tungsten.

HCP (Hexagonal close-packed)

A hexagonal stacking arrangement that is close-packed but has fewer slip systems; examples include magnesium and zinc.

Vacancy

A point defect representing a missing atom in the crystal lattice.

Interstitial atom

A point defect where an extra atom is squeezed into a non-lattice position.

Substitutional atom

A point defect where a different atom replaces a normal atom in the lattice.

Dislocation

A line-like distortion in the crystal that allows slip and plastic deformation.

Elastic deformation

Reversible deformation where atomic bonds stretch slightly and the material returns to its original shape after load removal.

Plastic deformation

Permanent shape change where atomic planes slip into new positions and remain after the load is removed.

Grain size reduction

A strengthening mechanism where smaller grains provide more grain boundaries to block dislocation movement.

Solid solution strengthening

Adding alloy atoms that distort the lattice and block dislocations.

Cold working / strain hardening

Plastic deformation at low temperature that creates more dislocations which block each other, increasing strength while reducing ductility.

Stiffness

Resistance to elastic deformation, measured by Young's modulus ($E$).

Strength

A material's resistance to plastic deformation or failure.

Yield strength

The specific stress level where plastic deformation begins.

Ultimate tensile strength (UTS)

The maximum engineering stress reached on a stress-strain curve.

Ductility

The amount of plastic deformation occurring before failure, often measured as percent elongation.

Hardness

Resistance to local surface deformation or indentation.

Toughness

The energy absorbed before fracture, represented by the area under the stress-strain curve.

Engineering stress ($\sigma$)

$\sigma = \frac{F}{A_0}$, where $F$ is the force and $A_0$ is the original cross-sectional area.

Engineering strain ($\epsilon$)

$\epsilon = \frac{\Delta L}{L_0}$, representing the change in length divided by the original length.

Necking

The local narrowing or thinning of a material that occurs after reaching the Ultimate Tensile Strength (UTS).

Monomer

The small molecule or repeat unit that serves as the building block of a polymer.

Polymer

A very large molecule made from many repeating units joined into a chain.

Saturated hydrocarbon

A hydrocarbon where carbon atoms have single bonds only.

Unsaturated hydrocarbon

A hydrocarbon that contains double or triple bonds between carbon atoms.

Thermoplastic

A polymer that softens or melts when heated and can be remoulded or recycled easily.

Thermoset

A polymer that is set permanently by crosslinking during curing and does not melt when heated.

Matrix

The phase in a composite that holds the reinforcement, protects it, and transfers the load.

Reinforcement

The phase in a composite, such as fibres or particles, that provides strength and stiffness.

Rule of Mixtures

A linear weighted average formula ($P_c = P_f V_f + P_m V_m$) used to estimate the properties of a composite.

Vitrification

A ceramic fabrication process where ceramic powder is mixed with glass powder and fired so the glass phase bonds the particles.

Sintering

A process of firing a compacted powder below its melting point to allow particles to diffuse and bond.

Anode

The component of a corrosion cell where oxidation occurs and metal atoms lose electrons; this is where corrosion takes place.

Cathode

The component of a corrosion cell where reduction occurs and electrons are consumed.

Electrolyte

A conducting environment, such as water with salts or acids, that allows ion movement in a corrosion cell.

Passivation

The formation of a protective oxide layer on a material's surface that slows down the corrosion rate.

Sacrificial anode

A method of cathodic protection where a more active metal is attached to a structure to corrode in its place.

Isotropic

A material condition where properties are the same in all directions.

Anisotropic

A material condition where properties differ depending on the direction, common in fibre composites and rolled metals.