Engineering Materials and Testing Concepts

Vocabulary flashcards summarizing key terms and definitions from the lecture on engineering materials, their classifications, properties and standard mechanical testing methods.

Engineering Materials

Substances used to create products and structures; broadly classified into metals, non-metals, polymers, ceramics, composites and semiconductors.

Metals

Materials composed primarily of metallic elements that are dense, conductive, opaque, and generally strong, stiff and ductile.

Ferrous Metals

Metallic materials whose main constituent is iron; include cast iron, steel and wrought iron.

Non-Ferrous Metals

Metals and alloys that contain little or no iron, e.g., copper, aluminium and zinc.

Alloy

A metallic material formed by combining a metal with at least one other element to improve properties.

Cast Iron

Ferrous alloy with 2–4 % carbon, produced by smelting and casting; not worked with hammers.

Grey Cast Iron

Common cast iron whose fracture surface looks gray due to flake graphite; good thermal conductivity and vibration damping.

White Cast Iron

Cast iron in which carbon exists only as cementite; very hard, wear-resistant and brittle.

Malleable Cast Iron

White cast iron heat-treated to convert carbides to compact graphite, giving improved ductility and machinability.

Nodular (Ductile) Cast Iron

Cast iron modified with magnesium so graphite forms as spheroids, yielding high strength and ductility.

Wrought Iron

Nearly pure iron (<0.08 % C) made in a puddling furnace; tough, ductile, weldable and corrosion-resistant.

Steel

Ferrous alloy with <2 % carbon, refined from pig iron; properties vary with carbon content and alloying.

Low-Carbon Steel

Steel containing 0.08–0.35 % C; highly weldable and formable but low hardenability.

Medium-Carbon Steel

Steel with 0.35–0.65 % C; higher strength and hardenability than low-carbon grades.

High-Carbon Steel

Steel containing 0.65–1.3 % C; very hardenable with high wear resistance but poor weldability.

Stainless Steel

Ferrous alloy with ≥11 % chromium (often plus nickel); outstanding corrosion resistance.

High-Speed Steel

Tool steel alloyed with W, Mo, Cr or Co; retains hardness at high cutting speeds.

Silicon Steel

Iron alloy with up to 3.2 % Si; exhibits high electrical resistivity and excellent magnetic properties, used in transformers.

Copper (Cu)

Red-orange non-ferrous metal known for high electrical and thermal conductivity, malleability and corrosion resistance.

Aluminium (Al)

Lightweight non-ferrous metal (density 2.7 g cm⁻³) with good conductivity, corrosion resistance and formability.

Zinc (Zn)

Bluish-white metal used mainly for galvanizing, die-casting and battery anodes.

Brass

Copper-zinc alloy exhibiting good machinability, conductivity, low friction and non-magnetic behaviour.

Bronze

Copper-tin alloy, typically 88 % Cu / 12 % Sn, valued for low friction, corrosion resistance and casting properties.

Polymer

Substance composed of very large molecules formed from repeating monomer units.

Polymerization

Chemical reaction in which monomers join to form a polymer chain.

Thermoplastic

Polymer that softens on heating and can be remelted and recycled; generally linear- or branched-chain.

Thermoset

Polymer that forms cross-links during curing; hard and heat-resistant but not remeltable or recyclable.

Elastomer

Polymer with lightly cross-linked chains allowing large, reversible elastic deformation (e.g., natural rubber).

Fiber (Polymer)

Polymer with strong intermolecular forces that can be drawn into long filaments, used in textiles (e.g., nylon).

Linear Polymer

Macromolecule consisting of unbranched chains of repeating units.

Branched Polymer

Polymer whose main chain carries side-branch chains.

Cross-Linked Polymer

Polymer whose chains are connected by covalent bonds forming a 3-D network.

Network Polymer

Highly cross-linked polymer forming a rigid three-dimensional structure (typical of thermosets).

Homopolymer

Polymer made from one type of monomer (e.g., polystyrene).

Copolymer

Polymer formed from two or more different monomers (e.g., ethylene-vinyl acetate).

Natural Polymer

Polymer occurring in nature, such as cellulose, proteins or DNA.

Synthetic Polymer

Man-made polymer produced from petrochemical feedstocks, e.g., plastics and synthetic rubber.

Organic Polymer

Polymer whose backbone contains carbon atoms.

Inorganic Polymer

Polymer whose backbone lacks carbon atoms (e.g., silicones, polyphosphazenes).

Polyethylene (PE)

Thermoplastic made from ethylene monomers; produced as LDPE or HDPE for bags, bottles, films and pipes.

Polypropylene (PP)

Heat-resistant, chemical-resistant thermoplastic used in food containers, ropes and labware.

Polyvinyl Chloride (PVC)

Versatile thermoplastic available in rigid and flexible forms for pipes, cable insulation and profiles.

Polystyrene (PS)

Thermoplastic used as solid plastic (CD cases) or foam (packaging, insulation).

Polytetrafluoroethylene (PTFE)

Highly inert fluoropolymer known as Teflon, used for non-stick coatings and electrical insulation.

Nylon (Polyamide)

Family of synthetic fiber-forming polymers valued for strength, wear resistance and use in textiles.

Polyurethane (PU)

Polymer family used in foams, coatings, shoe soles and wheels; properties vary with formulation.

Ceramic

Inorganic, non-metallic material formed by shaping and firing; hard, brittle and heat-resistant.

Porcelain

White, translucent ceramic made from kaolin, feldspar and quartz; used for tableware and art objects.

Stoneware

High-strength ceramic made from clay and feldspar; used for tiles and building products.

Earthenware

Low-fired, porous ceramic made from clay and sand; common for pottery and cookware.

Refractory

Ceramic able to withstand very high temperatures; includes firebricks, magnesite and silica bricks.

Glass

Amorphous inorganic solid, typically silica-based, that is transparent and a good electrical insulator.

Cement

Hydraulic binder that sets and hardens by reaction with water; fundamental to concrete and mortar.

Abrasive

Very hard material used to wear away or polish other substances (e.g., diamond, silicon carbide).

Advanced Ceramic

Engineered ceramic (e.g., Si₃N₄, SiC, ZrO₂) with specialized properties for high-tech applications.

Bio-Ceramic

Advanced ceramic used as an implant or prosthetic material due to biocompatibility.

Composite Material

Material made of two or more distinct constituents (matrix and reinforcement) with synergistic properties.

Matrix (Composite)

Continuous phase in a composite that binds reinforcements and transfers loads.

Reinforcement (Composite)

High-strength phase (fiber, particle, etc.) that provides stiffness and strength to a composite.

Particle-Reinforced Composite

Composite strengthened by discrete particles; includes concrete and dispersion-strengthened alloys.

Fiber-Reinforced Composite

Composite in which load-bearing fibers (glass, carbon, aramid) are embedded in a matrix.

Structural Composite

Composite such as laminates or sandwich panels designed for high stiffness and strength in structures.

Laminar Composite

Composite built from bonded layers oriented in specific directions (unidirectional, cross-ply, etc.).

Sandwich Panel

Structural composite with two strong face sheets bonded to a lightweight core, offering high stiffness-to-weight.

Nano-Composite

Composite containing nano-scale reinforcements that give superior mechanical, thermal or barrier properties.

Large-Particle Composite

Particle composite where particles restrain matrix movement at macroscopic scale (e.g., concrete).

Dispersion-Strengthened Composite

Composite with very fine particles (10–100 nm) that impede dislocation motion, enhancing strength.

Critical Fiber Length

Minimum fiber length required so load is effectively transferred from matrix to fiber for reinforcement.

Semiconductor

Material with electrical conductivity between conductors and insulators; e.g., silicon and gallium arsenide.

Doping (Semiconductors)

Intentional addition of impurities to a semiconductor to control its electrical conductivity.

Elemental Semiconductor

Semiconductor composed of a single element such as silicon (Si) or germanium (Ge).

Compound Semiconductor

Semiconductor formed from two or more elements, e.g., GaAs, CdTe; classified as II–VI or III–V.

Impact Test

Experiment measuring energy absorbed by a notched specimen under sudden load, indicating toughness.

Charpy Impact Test

Impact test where a simply-supported, notched bar is struck in the middle; energy absorbed is recorded.

Izod Impact Test

Impact toughness test using a cantilevered, notched specimen struck at its top.

Toughness (Material)

Ability of a material to absorb energy and plastically deform before fracturing.

Tensile Test

Test in which a specimen is pulled in tension until failure to determine mechanical properties.

Yield Strength

Stress at which a material begins to plastically deform (0.2 % offset is commonly used).

Ultimate Tensile Strength

Maximum engineering stress reached in a tensile test before necking starts.

Modulus of Elasticity

Slope of the initial linear portion of a stress–strain curve; measures stiffness.

Fracture Strength

Stress at which a specimen ultimately breaks during a tensile test.

Percentage Elongation

Total strain at fracture expressed as a percent of original gauge length; indicates ductility.

Hardness Test

Procedure that measures a material’s resistance to localized plastic deformation (indentation or scratching).

Rockwell Hardness Test

Indentation hardness test where depth of penetration under specific loads and indenters is measured.

Vickers Hardness Test

Indentation test using a diamond pyramid; hardness number calculated from load divided by impression area.

Brinell Hardness Test

Indentation test using a 10 mm hardened steel or carbide ball and measuring impression diameter.

Indenter

Hardened tip (ball, cone or pyramid) used to make an impression during hardness testing.

Proportionality Limit

Maximum stress up to which stress and strain are directly proportional (Hooke’s law region).

Elastic Limit

Highest stress a material can withstand without permanent deformation after unloading.

Notch Sensitivity

Degree to which the presence of a notch reduces a material’s toughness or strength.

Brittle Fracture

Failure with little plastic deformation, producing bright, crystalline surfaces.

Ductile Fracture

Failure after significant plastic deformation, producing dull, fibrous surfaces.