ENIN 343 Midterm

Manufacturing (definition)

Transformation of raw materials into useful products using the easiest and least expensive methods.

Inputs to a manufacturing system

Customer demands, materials, money (working and fixed capital), energy.

Processes within a manufacturing system

Management, design, and production.

Outputs of a manufacturing system

Consumer goods and capital goods.

Manufacturing classification by size

Mass production, medium production, and job lot (low) production.

High (mass) production volume

10,000 to millions of units/yr.

Advantages of high production

Established sales volumes, production independent of orders, low unit cost, least manufacturing time/unit, least skilled/cheapest labor.

Disadvantages of high production

Special-purpose machines, changes hard to implement, large inventories, inflexibility, large initial investment.

Medium production volume and features

100 to 10,000 units/yr; variable output, multipurpose machines, lower initial investment, faster market response.

Low production volume and features

1 to 100 units/yr; production tied to sales orders, general-purpose machines, least equipment investment, frequently changed products, highly skilled workers, very flexible.

Three parts of manufacturing capability

Technological processing capability, physical product limitations, production capacity.

Four main classes of engineering materials

Metals, ceramics, polymers, composites.

Metals subcategories

Ferrous and nonferrous.

Ceramics subcategories

Crystalline ceramics and glasses.

Polymers subcategories

Thermoplastics, thermosets, elastomers.

Composites subcategories

Metal matrix, ceramic matrix, polymer matrix composites.

Factors in machine selection

Process, production volume, quality of product, and characteristics of equipment.

Examples of general purpose machines

Lathes, drills, planers, grinders.

Five classifications of processes

Shape change, machining, surface finishing, joining, change of physical properties.

Shape change processes (definition)

Change starting material into the primary shape of the product; rough surface, lower accuracy.

Shape change processing methods

Extraction from ore, casting, hot/cold working, powder metallurgy, plastics molding.

Machining: chip removal type

Smooth surface, higher accuracy, either rotary or reciprocating.

Machining: non-chip-removal examples

Laser cutting and sparking machining.

Purpose of surface finishing

Obtain smooth surface, high accuracy, protective layer, appearance.

Surface finishing examples

Polishing, coating (painting, peening, electroplating), anodizing.

Anodizing

Creating a non-corroding oxide film on light alloys.

Joining processes

Welding, brazing, soldering, sintering, fastening screws, adhesives, rivets.

Processes that change physical properties

Heat treatment (annealing, normalizing, quenching, tempering), hot/cold working, shot peening.

SI base units

m, kg, s, ampere, Kelvin, candela, mole.

Two main groups of materials

Metallic and non-metallic.

Metallic materials subdivide into

Ferrous and non-ferrous.

Non-metallic materials subdivide into

Organic and inorganic.

Organic materials

Carbon chemically combined with oxygen, hydrogen, and other non-metallic substances (e.g., animal/vegetable cells, polymers).

Inorganic materials

Metallic and non-metallic elements chemically bonded (e.g., stone, glass, bricks).

Ceramics (definition)

Materials of metallic and/or non-metallic elements chemically bonded together.

Composite (definition)

Material of two or more phases processed separately then bonded to give properties superior to its constituents.

Types of polymers

Thermoplastic, thermosetting, and elastomer.

Three phases of materials

Gas, liquid, and solid (depend on temperature and pressure).

Molecular motion: vapor vs liquid vs solid

Vapor: move randomly; liquid: move within a container; solid: limited to certain locations.

Three common metal crystal structures

BCC (body-centered cubic), FCC (face-centered cubic), HCP (hexagonal close-packed).

Why are solid metals crystalline?

Atoms are aligned in a geometric pattern (space lattice) made up of unit cells.

Space lattice / unit cell

Space lattice: the geometric atomic pattern; unit cell: the repeating building block of the lattice.

What do material properties depend on?

The microstructure of the material.

Grain formation sequence

Nuclei initiation, crystals grow and contact each other, forming grain boundaries.

Engineering stress

Stress = F/A0 (Pa or psi).

Engineering strain

e = (L - L0)/L0.

Poisson's ratio

v = -(lateral strain)/(axial strain).

Hooke's law

Stress = E x strain (sigma_e = E e).

Young's modulus (E)

E = stress/strain.

Three key points from the tensile test

Yield strength (sigma_y), ultimate tensile strength (sigma_u), fracture strength (sigma_f).

Shear stress equation

tau = G x gamma.

Shear modulus G in terms of E and v

G = E / [2(1 + v)].

Ductility

Ability to deform without failure.

Ultimate elongation

e_u = (L_u - L_0)/L_0.

Total elongation (to fracture)

e_f = (L_f - L_0)/L_0.

Reduction of area (RA)

RA = (A_0 - A_f)/A_0; indicates brittle or ductile behavior.

Toughness

Energy absorbed for deformation or failure; area under the stress-strain curve.

True stress

sigma = F/A (using instantaneous area).

True strain

epsilon = integral of dL/L = ln(L/L0).

Relationship: true strain and engineering strain

epsilon = ln(1 + e).

Relationship: true stress and engineering stress

sigma = sigma_e (1 + e).

Flow curve equation

sigma = K epsilon^n.

K in the flow curve equation

Strength coefficient.

n in the flow curve equation

Strain hardening exponent.

Safety factor (SF)

SF = max allowable stress / applied (design) stress.

Standard hardness tests

Rockwell, Brinell, Vickers, Shore's scleroscope.

Density

Mass per unit volume (m/V).

Specific weight

Weight per unit volume (W/V).

Thermal expansion equation

Delta L = alpha L0 Delta T.

Specific heat

Energy required to raise a unit mass by one degree; C = H/(W Delta T).

Three other methods of materials evaluation

Impact test (Charpy), fatigue test, fracture toughness test.

Fracture toughness equation

K_IC = Y sigma_app sqrt(pi a).

Cooling curve

Solidification curve of a metal as it cools.

Phase diagram (equilibrium)

Graphical representation of the phases present and the composition, temperature, and pressure ranges over which they are stable.

Why is pig iron important?

Intermediate form from which steel can be made; also used in foundries.

Blast furnace charge (top)

Iron-bearing materials, coke (fuel), and flux (limestone/dolomite).

Blast furnace blast (bottom)

Heated air plus fuel (gas, oil, powdered coal).

Iron ores used in the blast furnace

Hematite Fe2O3 (70% Fe), limonite Fe2O3.xH2O, magnetite Fe3O4.

Sinter

Agglomerate of iron-bearing material and flux particles.

Pellets

Agglomerate of iron-bearing material with fuel and binder.

Function of coke

Heat for smelting, chemical reactant (CO), and carbon that dissolves in the metal.

Function of flux (limestone/dolomite)

Forms fluid slag with coke ash, gangue, and impurities; controls sulphur content of the iron.

Blast furnace gas use

Unused CO (B.F. gas) is used to preheat the blast air.

Blast furnace outputs

Liquid iron (cast into pigs or sent to steelmaking) and slag (waste, other uses).

Impetus for Direct Reduction of Iron (DRI)

Low grade ores and available fuels (low grade non-coking coal).

Aims of DRI

Produce steel directly from ore; produce iron comparable to pig iron; produce low-C iron/steel.

Electric furnace steelmaking

Most commonly used; mainly scrap; graphite electrodes; 3-phase power; 60,000-100,000 A.

Basic Oxygen Furnace (BOF) charge and method

Scrap and molten iron; O2 lance above bath at high velocity (140-180 psi); temperatures up to 3000 F; flux added via chute.

BOF key advantage

Very flexible with respect to raw materials.

Killed steel

Deoxidized; no gas evolution during solidification; forms a cavity (pipe) after solidification.

Rimming steel

No/light deoxidation; CO evolves during solidification; honeycomb structure that compensates for shrinkage.

Advantages of continuous casting

Better productivity and higher yields.

Steel (definition)

Alloy of Fe, C, and other elements; cast, rolled, or forged.

Steel classifications

Carbon steel (low, medium, high) and alloy steel (low, high).

AISI-SAE steel numbering

4 digits: first two = class of steel; last two = carbon in hundredths of a percent.

AISI-SAE examples

10xx plain carbon; 11xx resulfurized carbon; 30xx Ni-Cr; 50xx low chromium.

Low alloy vs high alloy steel

Low alloy: special alloying elements < 8.0%; high alloy: > 8.0%.

Alloy steel characteristics

Higher ductility and strength, hardenability, high toughness, high/low temp properties, corrosion and wear resistance, fine grain size.

Ferritic stainless steel

12-20% Cr; cannot be heat-treat hardened; good corrosion resistance (types 405, 430).

Martensitic stainless steel

12-17% Cr, 0.15-1.1% C; hardenable; high strength; moderate corrosion resistance (types 410, 416).