Test 3 Study Guide Review

A collection of vocabulary terms and definitions derived from the lecture notes for Test 3.

Apparent Elastic Limit

The point at which the rate of change of strain is 50% greater than the initial rate of change of strain.

white cast iron

produced by rapid cooling of molten iron. Most of the carbon remained combined with iron in the form of iron carbide.

high strength

very brittle

not easily machined

abrasion resistant

Modulus of Rupture

Under center-point loading, R = 3PL/2bd².

Thermal Stress

Stresses in materials caused by changes in temperature that lead to changes in geometries.

Thermal Strain

The deformation per unit length in a material due to temperature change, given by εt = δt / L = α Δt.

common characteristics of metals

Metallic bonding: atoms or molecules are in metallic bonding with the electrons from the outer shell of the atoms in a common "electron gas," which binds the molecules together

Crystalline structure

High electrical conductivity

High ductility: one plane of close-packed atoms can slide over another one without fracture

Ferrous Metals

Metals in which the principal element is iron, such as steel and wrought iron.

Non-ferrous Metals

Metals in which the principal element is not iron, such as copper, aluminum, and nickel.

nonferrous metals differences in properties from ferrous metals

properties are less affected by heat treatments

more corrosion resistant

lower modulus of elasticity

lower fatigue strength

mostly used in alloy form

Wrought Iron

iron containing a small amount of slag (less than 3%) and a very small amount of carbon (less than 0.1%). Slag particles appear as long fibrous elements in the iron

High ductility and toughness

Cast Iron

Iron that contains between 2.2 to 4.5% carbon (types: gray, white, ductile cast iron)

Brinell Hardness Test

Method for measuring hardness by applying a known load to an indenter and measuring the indentation size.

Rockwell Hardness Test

A hardness test where a minor load is applied before a major load, and the indentation is measured post-load.

Corrosion of Metals

disintegration of metals by surrounding media (acids, bases, brines, oxygen or water)

Electrolytic (or Galvanic) Corrosion

When two metals are in contact, the more active metal will tend to corrode. The metal with a lower (or more negative) reaction potential will tend to corrode. Anode will corrode

Thermosetting Plastics

harden (or "thermoset") in an irreversible process when heated. Chemically setting plastics: harden by adding suitable chemicals

Plasticizer

Additive used in polymers to increase flexibility.

Additives in Plastics

Substances like antioxidants, flame retardants, and dyes added to improve properties of plastics.

Engineering Plastics

Plastics designed for specific engineering applications, offering unique properties like strength and insulation.

list all common forms of nonferrous metals

copper, aluminum, lead, zinc, nickel

common forms of nonferrous metals: copper

Density = 8.9 g/cm3

High electric conductivity

Soft and ductile

High resistance to atmospheric corrosion

Can be work-hardened

common forms of nonferrous metals: aluminum

Soft & ductile

High electrical conductivity

Low density of 2.7 g/cm3 (note: 7.9 g/cm3 for Iron)

High resistance to atmospheric corrosion

common forms of nonferrous metals: lead

Density = 8.88 g/cm3

High specific gravity of 11.36

Malleable

Low endurance limit

Good corrosion & acid resistance

Usage: solder (95% Pb, 3% Sn, 2% Ag), ball bearing (85% Cu, 5% Sn, 5% Zn, 5% Pb)

common forms of nonferrous metals: zinc

Brittle at room temperature

Can be work hardened (density =7.1 g/cm3)

Usage: galvanizing of steel

common forms of nonferrous metals: nickel

High strength & ductility

Resistant to corrosion at elevated temperatures

Ex: Monel Metal (66% Ni, 28% Cu, & small amounts of Fe, Mn, & Al)

Very ductile & tough

High tensile strength at low and high temperature

High resistance to corrosive liquids

list all copper alloys and their composition

brass (65-70% Copper, 35-30% Zinc), bronze (< 20% Tin. more than 80% Copper), aluminum bronze (5-10% Aluminum, 90% Copper, some Iron), beryllium copper (2% Beryllium, 98% Copper)

copper alloys: brass

Higher tensile strength and hardness with little reduction in ductility.

Usage: plumbing

copper alloys: bronze

Slightly higher tensile strength & hardness than Brass

copper alloys: aluminum bronze

High tensile strength & hardness

Low ductility

Usage: condenser tubing

copper alloys: beryllium copper

Specific gravity of 1.85

E = 42 x106 psi

Most effective alloy of Copper

Great strength while retaining the desirable properties of copper

Usage: precision springs

results of hardness tests can be used to…

estimate the ultimate strength of metals

rockwell C

Indenter: diamond cone

Major load: 150 kg

Number = 100 - (d / 2μm)

rockwell B

Indenter: 1/16 in. diameter steel ball

Major load: 100 kg

Number = 130 - (d / 2μm)

rockwell hardness test

A minor load is first applied to seat the indenter. A major load is then applied. The indentation by the major load is then measured (after the major load is removed)

brinell hardness number (BHN)

load mass / indented area = p / [πD/2 ( D - (D^2 - d^2) )
D = diameter of steel ball (mm)

d = diameter of indentation (mm)

tension test

to obtain stress-strain diagram & the following properties:

Yield Strengths at certain offset

Ultimate Tensile Strength

Elastic Modulus

% Elongation at failure (measure of ductility)

steel

.05% to 2.0% Carbon (usually less than 1.2%)

Properties depend on: carbon content, alloying elements, microstructure (which can be modified through heat treatments), mechanical work (work-hardened)

Usage: structural steel, reinforcing bars, form works

ductile cast iron

contains 0.05% of magnesium.

Most of the carbon are in the form of spheroidal graphite.

higher tensile strength & ductility as compared with gray cast iron

gray cast iron

produced by slow cooling of molten iron. Most of the carbon are separated in the form of graphite (in flake form)

easily machined but low in ductility

effects of adding chromium to steel

combines with Carbon & Iron to form a double Carbide, produces stainless and heat-resisting steel

ex: Low Chromium Alloy: 1 - 2% Cr 1% C, Stainless Steel: 10 - 27% Cr

effects of adding molybdenum to steel

increases tensile strength at high temperature, hardening agent in steel

effects of adding nickel to steel

Adds strength with little loss in ductility

Gives high resistance to corrosion at high temperature when used in high percentages (ex: High temperature alloy: 25-35% Ni)

effects of adding manganese to steel

Helps to eliminate harmful components in the production of steel

Combines with Carbon to form Mn3C, which increases the hardness and resistance to abrasion without loss of ductility, and slightly increases the tensile strength of steel

effects of adding sulfur to steel

Makes the steel more easily machined

as % carbon increases…

ductility decreases

toughness decreases

strength generally increases

as % cold work increases…

hardness increases
ductility decreases

yield strength increases

toughness decreases

% cold work formula

(A0 - Af) / A0 × 100

methods of work hardening

cold rolling and cold drawing

principle of work hardening

If a metal has a Yield Point of 50 ksi. The bar is stressed past its yield point to point A (80 ksi) and released. If the same bar is re-tested, it will show a Y.P. of 80 ksi. In effect, the metal has been work-hardened.

effects of adding tungsten to steel

forms a hard stable Carbide, increases the tensile strength at high temperature, too brittle for structural purposes

e.g. usage in cutting tools

effects of adding silicon to steel

combines with Carbon to form a hard Carbide, increases tensile strength without loss in ductility

methods to reduce corrosion of metals

Passivation: using the corroded metal as a protective shield against further corrosion. Ex: Aluminum → Aluminum oxide / Chromium → Chromium oxide. Weathering steel (Corten Steel): a special steel alloy designed to allow the oxidized steel to protect the rest of the steel from further oxidation

Organic coating - using paints or varnishes as a protective layer.

Coating with a stable metal. Ex: Gold plating or silver plating

Active metal bar as a sacrificial anode: Ex: Zinc bar in steel storage tank → Galvanized steel (Zinc acts as a sacrificial anode)

Inhibitor in the electrolyte (liquid): It either forms a passivation layer on the metal, or reduces the dissolved oxygen in the liquid. Ex: Corrosion inhibitor in anti-freeze for car radiator.

Metals which are close in reaction potentials

Noble metals

Electrical insulation between different metals

Impressed Current Cathodic Protection: connect the structure to be protected to a dc electric source to cause a flow of electrons towards it, making it a cathode (and protecting it from corrosion)

thermoplastics

soften when heated and harden when cooled, no matter how many times the cycle is repeated

polymers

extremely large molecules that are made up of smaller units called monomers

plastics

synthetic organic polymers capable of being molded and used in engineering applications

raw materials in plastics

Cellulose from plant fibers

Derivatives from coal and tar (such as Phenol, cresols & naphthalene)

Derivatives from petroleum (such as ethylene and propylene)

methods of production of plastics

Condensation Polymerization: reactive molecules combine with one another to form polymers while small molecules, such as H2O are released

Addition Polymerization: small identical or somewhat diversified molecules are linked together, with no elimination of small molecules (ex: PMMA)

-Plasticizers to increase flexibility

-Antioxidants to reduce the rate of degradation (or oxidation) due to heat or UV light

-Reinforcements to increase strength

-Flame retardants to reduce flammability

-Dyes to add color

properties of engineering plastics

Light weight (high strength/density)

Good electrical insulation

Low heat conductivity

Colorability

Metals may be molded into plastics

Some plastics are chemical resistant

thermoplastic: ABS (Acrylonitrile-Butadiene-Styrene)

specific gravity: 1.18

tensile strength: 6,000 - 6,500 psi

Elongation: 15 - 60%

Elastic Modulus: 250 - 300 x10^3 psi

Usage: pipes, concrete forms, building and vehicle components, appliance housing

thermoplastic: PMMA (polymethyl methacrylate or plexiglass)

specific gravity: 1.18

tensile strength: 7,000 - 10,000 psi

Elongation: 2 - 10%

Elastic Modulus: 300 - 400 x10^3 psi

Usage: windows, wall panels, lighting devices

thermoplastic: PVC (Polyvinyl chloride) -- may be rigid or flexible

specific gravity: 1.32 - 1.44

tensile strength: 6,000 - 9,000 psi

Elongation: 5%

Elastic Modulus: 350 - 450 x10^3 psi

Usage: pipes, ducts, gutters, sidings

thermosetting plastic: PF (Phenol-Formaldehyde or Bakelite)

specific gravity: 1.25 - 1.30

tensile strength: 7,000 - 8,000 psi

Elongation: 1.0 - 1.5%

Elastic Modulus: 1 x10^6 psi

Usage: serving trays, radio cabinet, electrical parts

thermosetting plastic: Polyester reinforced with glass fibers (fiberglass)

specific gravity: 1.90

tensile strength: 5,000 - 9,500 psi

Elastic Modulus: 1.5 - 2 x106 psi

Usage: fiberglass boats, auto bodies, vent and ducts, adhesives

Design considerations when using plastics versus metals

1. Low Elastic Modulus/ tensile strength:

20-100 vs. 200-1000 (for metals)

2. High coefficient of thermal expansion:

5-20 times those of metals

3. High creep deformation under load

Common Plastics Used in Packaging: Polyethylene Terephthalate (PET or PETE)

Uses: Plastic soft drink bottles, mouthwash bottles, peanut butter and salad dressing containers

Common Plastics Used in Packaging: polystyrene (PS)

Uses: Videocassette cases, compact disc jackets, coffee cups, knives, spoons and forks, cafeteria trays, grocery store meat trays

Common Plastics Used in Packaging: Polypropylene (PP)

Uses: Ketchup bottles, yogurt containers and margarine tubs, medicine bottles

Common Plastics Used in Packaging: Low Density Polyethylene (LDPE)

Uses: Bread bags, frozen food bags, grocery bags

Common Plastics Used in Packaging: Vinyl (polyvinyl chloride or PVC)

Uses: Clear food packaging, shampoo bottles

Common Plastics Used in Packaging: High Density Polyethylene (HDPE)

Uses: Milk, water and juice containers, grocery bags, toys, liquid detergent bottles

AISI (American Institute of Steel and Iron) and SAE (Society of Automobile Engineers) Nomenclature For Steels

10 XX Plain Carbon Steel

11 XX Plain Carbon (Resulferized)

13 XX Manganese (1.5 - 2.0%)

23 XX Nickel (3.25 - 3.75%)

40 XX Molydenum (0.20 - 0.30%)

41 XX Chromium (0.40 - 1.2%), Molydenum (0.08 - 0.25%)

where, XX is the Carbon content -- 0.XX%

ASTM Designation for steels

A36 Common structural carbon steel, used mainly for buildings

Yield Point = 36 ksi (or 250MPa)

Tensile strength = 58 - 80 ksi

Elongation = 20%.

A529 High strength carbon steel, used for bolted and welded building frames and trusses

Yield Point = 42 ksi

Tensile strength = 60 - 85 ksi

Elongation = 19%

A514 Heat treated steel, used in welded bridges and other structures

Yield strength = 100 ksi

Tensile strength = 115 - 135 ksi

Elongation = 18%

A572 High-strength low-alloy steel (with high corrosion resistance)

Yield Str. Tensile Str. Elongation

Grade 42 42 ksi 60 ksi 20%

Grade 50 50 ksi 65 ksi 18%

Grade 60 60 ksi 75 ksi 16%

The grade of the steel usually specifies its yield strength.

elastic modulus of all steels

28,000,000 - 30,000,000 psi

main product & byproduct of blast-furnace process

pig iron (not workable due to high carbon content making it brittle) and slag

three raw materials & their functions for the production of iron in the blast-furnace process

iron ore, coke (provides fuel and reducing agent CO), limestone (used as flux to get rid of impurities like sulfur and an extra source of carbon monoxide)

formula for computing splitting tensile strength

2P / (pi * ld)