MMET 206 - Exam 1 - TAMU - Asadi

What are the 4 environmental stressors taken into account when analyzing a product's life cycle?

-Resource and water consumption
-energy consumption over life
-emission of CO2, NOx, SOx, particulates, etc
-toxic residues, acidification, ozone depletion

How much embodied energy in steel?

29 (MJ/Kg)

How much embodied energy in Polyethylene?

80 (MJ/Kg)

6 types of physical material properties

Mechanical
Thermal
Electrical
Magnetic
Optical
Corrosion

Definition of Normal Strain

volume change

Definition of stiffness

measures how well a material can resist the change in length under a normal stress

Definition of Rigidity

Measures how well a material can resist the change in shape under a shear stress

what machine is used to measure stresses in a structure?

Strain Gages

What does an impact test measure?

the energy absorbed by the high strain rate fracture

in an Impact Test, the impact energy absorbed by the sample = ___

change in potential energy

how is a materials resistance to crack propagation determined?

notched bar impact method

viscoelastic materials can transition from ___ state to ___ state

glass sate to rubber state

what does fatigue testing do?

identifies the endurance limit, a stress below which fatigue will not occur

definition of hardness

a mineral's resistance to being scratched/ localized plastic deformation

What are the 4 methods of measuring hardness?

1. Rockwell - depth of penetration
2. Brinell - curved surface area
3. Vickers - projected area
4. Shore durometer -A for rubber/D for hard plastic

definition of bond energy

the amount of energy required to break apart a mole of crystals/ molecules into its component atoms, a measure of bond strength

definition of crystalline materials

made up of a single or multiple crystals

definition of crystal lattice

imaginary skeleton of a crystal structure

what are the 7 crystal systems?

triclinic
rhombohedral
orthorhombic
monoclinic
cubic
hexagonal
tetragonal

TRUE/FALSE: the hardness of a material depends on its cutting direction

TRUE

What are the 8 allotropes of Carbon?

1) Diamond,
2) Graphite
3) Lonsdaleite
4) C60 (Buckminsterfullerene or buckyball)
5) C540
6) C70
7) Amorphous carbon
8) single-walled carbon nanotube or buckytube

4 examples of things that need single crystalline materials

-Diamond single crystals for abrasives
-Aircraft engine turbine blades (Ni-based superalloy)
-Silicon wafers for IC chips
-Sapphire wafer for LED and optical lenses

Steps for a Product Life-Cycle Assessment

1. Produce a Life-Cycle Inventory for each design
2. Analyze the inputs and outputs for every phase and identify the environmental stressors
3. Add data together for the complete product life cycle and select the design that produces the least amount of environmental stressors

European Union's RoHS restricts the use of the following 6 substances in electrical and electronic equipment

1. Lead
2. Mercury
3. Cadmium
4. Cr^+6
5. & 6. PBB and PBDE (flame retardants)
Apple doesn’t allow PVC

What were the top 4 greenhouse gasses emitted in 2018 and their %'s?

1. Carbon Dioxide - 81%
2. Methane - 10%
3. Nitrous Oxide - 6%
4. Fluorinated Gases - 3%

What are he two sectors that cause the most emissions from energy consumption?

Transportation - 36%
Electricity Generation - 32%

Two main types of material properties

Chemical and Physical

3 mechanical material properties tests

tensile test
impact test
hardness test

Definition of Mechanical Properties

a materials ability to resist various effects caused by mechanical forces/ stresses

What is the Yield Strength and Young's Modulus of steel?

Yield Strength: 250-700 MPa
Young's Modulus: 200 GPa

What is the Yield Strength and Young's Modulus of HDPE (plastic)?

Yield Strength: 26-33 MPa
Young's Modulus: 0.8 GPa

Definition of strain

the materials response to stress

Definition of Shear Strain

shape change

formula for rigidity

rigidity = shear stress/ shear strain

Definition of Ductility

percent elongation at fracture

Ductility formula

(final length - original gage length) / gage length ⋅ 100

definition of deflection

how much a material curves under a load

definition of the Modulus of Toughness

The total area under the stress-strain curve to the point of rupture

Toughness is the combination of 2 properties:

strength and ductility

___ temperature = ___ impact energy = ___ ductile

what are two exceptions?

higher temp = higher impact energy = more ductile

exceptions: copper and aluminum

creep is the relationship between:

strain and time

definition of viscoelasticity

a property of materials that exhibits both viscous (liquid) and elastic (solid) characteristics when undergoing deformation

viscoelasticity is unique to ___

polymers

What does a fatigue test generate?

a S-N curve (Stress vs Number of load cycles)

what are the 2 types of shore durometer tests and what materials are they used on?

Shore A for rubber
Shore D for hard plastic

definition of metallic bond

sea of free valance electrons

definition of ionic bond

the attraction between oppositely charged ions (cations and anions)

what are the 2 types of physical bonds?

Van der Waals bonds
Hydrogen bonds

what two materials have both chemical and physical bonds?

polymers and graphite

what are the types of crystalline materials?

1. single crystalline (silicon wafer)
2. poly crystalline (metals, ceramics)
3. semi-crystalline (polymers)

what are the 3 most common unit cell types

BCC
FCC
HPC

unit cell types (7)

triclinic
tetragonal
rhombohedral
monoclinic
cubic
orthorhombic
hexagonal

How are Lattice Directions denoted?

[a b c]

How are the family of equivalent planes denoted?

{a b c}

Definition of Allotropic/ Polytrophic materials

materials which can exist in more than one crystal structure

What are the inputs in a product's life cycle? (3)

Energy
Feedstocks
Transportation

What is Life Cycle Inventory (LCI)

Inputs: raw materials, bulk materials, energy, water
Outputs: products, by products, gas emissions, product waste

After analyzing a products life cycle which design should you select?

The one that produces the least amount of environmental stressors in which carbon footprint is the main target

Definition of Embodied Energy

the energy required to produce raw materials from ores and feedstocks

How does using recycled materials affect the life cycle of a product?

Significantly lowers the embodied energy needed

How much embodied energy in Aluminum Alloys?

200 (MJ/Kg)

How much embodied energy in Concrete?

1.2 (MJ/Kg)

How much embodied energy in Device-Grade Silicon?

~2000 MJ/kg

Recycling requires ___% less energy with aluminum

95%

Recycling requires ___% less energy with steel

33%

Recycling requires ___% less energy with paper

40%

Recycling requires ___% less energy with plastic

90%

Recycling requires ___% less energy with glass

30%

Definition of Carbon Footprint

the total amount of greenhouse gas emissions caused directly and indirectly by an individual, organization, event, or product

Definition of greenhouse gases

Gases that trap and hold heat in the atmosphere and contribute to the greenhouse effect

3 Types of Fossil Fuels

coal, oil, natural gas

95% of CO2 emissions come from

Fossil Fuel Combustion

Where does society burn the most fossil fuels and their %'s

1. Electricity Generation - 42%
2. Transportation - 32%

How do we obtain the historical COs levels?

Atlantic ice cores

How much CO2 will be released to the atmosphere by burning 1 gallon of gasoline?

8.887 Kg or 23-26 kg

Definition of stress

what the material feels inside when there is an external force

What units are used to measure stress?

N/m² and Pascal (Pa)

How to calculate stress

force/area

Direction of Tensile stress

Direction of compressive stress

Definition of Normal Stress and the 2 types

forces are perpendicular to the surface of the material

tensile and compressive

Direction of shear stress

How to calculate normal strain

the change in elongation/original length

Two forms of Normal Strain

longitudinal strain and lateral strain

Definition of Longitudinal strain

The change in length parallel to the stress

(the change in length along the x direction)

Definition of Lateral strain

The change in length perpendicular to the stress

(the change in length along the y or z direction)

Poisson's Ratio (υ)

-lateral strain/ longitudinal strain

How is Shear Strain measured

an angle in radians

for perfectly incompressible material (materials volume remains constant under load), Poisson's ratio (υ)= __?

0.5

What is the Poisson's Ratio of rubber, steel, glass, cork?

0.5, 0.3, 0.2, 0.0

Definition of Elastic Range

Material will resume its original dimension after load is removed

Definition of Plastic Range

Material has permanent deformation occurs after load is removed

What is the Yield Point

When elastic range ends and plastic range begins

Definition of Tensile Strength

the largest stress a material can bear

You don't want to advertise a material or having more than ___% of its actual Yield Strength or more than ___% of its actual Tensile Strength

no more than 60% of YS
no more than 50% of TS

What is the heart of the Tensile Test Machine?

Load Cell

What is the Elastic Modulus?

The slope of the elastic range of a stress-strain diagram

Formula for stiffness

normal strain/ normal stress

If percent elongation ___ --> Ductile
If percent elongation ___ --> Brittle

>5% --> Ductile
<5% --> Brittle

___ stiff --> ___ brittle

more stiff --> more brittle