Transcript Mech 285 Lectures Professor Rodney Herring

Mech 285 Lectures
Professor Rodney Herring
Text Book
The Science and Engineering of Materials (Fifth Edition) by Donald
R. Askeland and Pradeep P Phule is the course text book
Assignments
There will be three assignments, one in May (3 marks), one in June (3
marks) and one in July (4 marks). (10 marks total)
Tests
There will be two mid-terms (15 marks each), one in late May or
early June, another in June or early July.
The final will be in August (40 marks).
Laboratories
There are 5 labs conducted in room ELW B231. Their manuals are
obtained by the MECH 285 web site. (20 marks total)
1) The Use of Phase Diagrams (5 marks)
TAs – Amine Yildiz (Mondays) & Robert McLeod (Tuesdays)
2) Introduction to Practical Metallography (5 marks)
TAs – Amine Yildiz (Mondays) & Robert McLeod (Tuesdays)
3) Solification of Pb-Sn Alloys (5 marks)
TAs – Julio Rodriguez (Mondays) & Neil Armour (Tuesdays)
4) Measurement of Thermal Conductivity (2.5 marks)
TAs – Julio Rodriguez (Mondays) & Neil Armour (Tuesdays)
5) Dislocations (2.5 marks)
TAs – Julio Rodriguez (Mondays) & Neil Armour (Tuesdays)
Lectures
There will be 16 lectures, which can be found on the MECH 285 web
site.
The lectures are in PowerPoint and pdf format, which can be
downloaded to your computer.
The source of the lectures are derived from
1) the text book, Science and Engineering of Materials (Fifth
Edition) by Donald R. Askeland and Pradeep P Phule
2) personally generated information
3) published literature
Lecture 1 - Objectives
At the end of this lecture you should be able to:
• Describe the course organization, name the required text book,
be aware of the class expectations and know how your
performance will be evaluated.
• Know the various classification of materials and some
examples of each
• Describe a typical new product design process
• Discuss the role of materials in the design process
Materials Science and Engineering
(MSE)
MSE is an interdisciplinary field concerned with inventing new
materials and improving existing materials by developing a deep
understanding of the microstructure-composition-processing
relationships.
Vocabulary is important and the following 4 terms will be used over
and over.
• Composition means the chemical make-up of a material.
• Structure means a description of the arrangement of atoms.
• Synthesis refers to how materials are made from naturally
occurring or man-made chemicals.
• Processing means how materials are shaped into useful
components to cause changes in the properties of different
materials.
Materials Science and Engineering
(MSE)
• In materials science the emphasis is on understanding the
underlying relationships between synthesis and processing,
structure and properties of materials.
• In materials engineering, the focus is on how to translate or
transform or apply materials into a useful device or structure.
Types of Engineering Materials
There are four common states of matter, which are the most basic
forms of materials. These are:
• 1) Plasma
–
–
–
–
Combustion – internal combustion engine
Florescent lights, Neon signs
Welding arc
Fusion energy, the Sun
• 2) Gases
–
–
–
–
Compression/expansion; heat pumps, refrigerators
Heat exchange in many systems
Vacuum pumping
Fuel in internal combustion engine
What is a Plasma?
Sun
Fusion
Neon-Lights
Types of Engineering Materials
• 3) Liquids
– Fluid dynamics
– Hydraulics
– Cryogenics, eg., Liquid Petroleum, Liquid Nitrogen, Liquid Hydrogen (Fuel
Cells)
• 4) Solids
–
–
–
–
–
–
Metals and alloys
Semiconductors
Ceramics
Glasses
Polymers (plastics)
Composites
Of these states, in this course we will primarily focus on the solid
materials.
“Functional” Classification of Materials
• Aerospace Materials – strong, light weight, resistance to radiation
damage
• Biomedical materials – materials that replace bones, organs,
teeth, etc.
• Electronic materials – semiconductors used in computers,
ceramics used as sensors, metals used as conductors,
superconductors for powerful magnets.
• Energy and Environmental materials – The nuclear industry use
uranium for fuel, zirconium to hold the uranium and high-strength,
low-corrosion steel in the nuclear reactors. The fuel cell industry
uses many types of materials such as zeolites, alumina, etc as
catalysts. Solar panels use materials such as amorphous silicon.
• Magnetic materials – computer hard disks and audio and video
cassettes use many types of ceramics, metals, and polymers
“Functional” Classification of Materials
• Photonic or Optical materials – silica is used for fiber optics.
Communication industry uses optical materials for semiconductor
detectors watand Lasers. Polymers are used to make Liquid
Crystal Displays used in the projector used for this lecture.
• “Smart” materials – can sense and respond to an external
stimulus such as temperature, stress, humidity or chemical
environment consisting of a sensors and actuators and read change
and initiate an action such as Lead Zirconium Niobate (PZT).
• Structural materials – are designed for carrying some kind of
stress such as in buildings, bridges and automobiles and they
usually consist of steels, aluminum, concrete and composites.
Often in these applications, combinations of strength, stiffnes and
toughness are needed under different conditions of temperature
and loading. These are still the most common use of materials.
Functional classification of materials with some examples.
Classification of Materials Based on “Structure”
• Crystalline – material’s atoms are arranged in a periodic fashion.
– Single crystals are entirely consisting of only one crystal such as silicon
used in the electronics industry
– Polycrystalline – material consists of many crystals or grains with a certain
size, shape, composition, etc. The grains are separated from each other by
grain boundaries.
• Amorphous – material’s atoms do not have a long range order.
– The newest material being developed is amorphous metals, which have a
super-large elastic modulus enabling extremely high stiffness and elasticity.
Why Study Materials
• Engineers do many things besides design new products.
• One of the distinguishing characteristics about engineers is their ability to “design”.
- To many, “design” is the essence of engineering!
• To design is to synthesize something “new” or collect/arrange existing items in a
new way to satisfy a recognized need of society.
– Referred to as, “Technology Push versus Market Pull”.
• A good design demands both “analysis” and “synthesis”.
– Few products consist of only one component/material
– Systems to subsystems to assemblies to components to materials.
• A very simple definition of a material is, “the substance of which something is
made”.
• The production and processing of materials into finished goods is a large part of our
economy, creating many jobs. New products are primarily made by engineers.
• Because creating new and better products involves analysis and synthesis with the
building blocks being materials. Engineers MUST know what materials exist and
have a broad knowledge of material properties.
Material Selection Process
The materials selection process changes as the design process
changes.
The mechanical engineer must recognize the different stages of the
design. One model is shown below.
The MSE tetrahedron shows the heart and soul of this field. The main
objective is to develop materials or devices that have the best
performance for a particular application where the performance-to-cost
ratio, as opposed to performance alone, is of utmost importance.
The three corners of the tetrahedron are represented by A – the
composition, B – the microstructure, C- the synthesis & processing of
materials, which are all interconnected and ultimately affect the cost-toperformance ratio.
Application of the tetrahedron of MSE to ceramic superconductors.
Note that the microstructure-synthesis and processing-composition are
all interconnected and affect the performance-to-cost ratio.
The performance-to-cost ratio is high limiting these materials only to
specialty applications such as small magnets having low-field strength.
Application of the tetrahedron of MSE to sheet steels for automobile
chassis. Note that the microstructure-synthesis and processingcomposition are all interconnected and affect the performance-to-cost
ratio.
Application of the tetrahedron of MSE to semiconducting
polymers for microelectronics.
Material Selection Process
The interactions among the design function, material, shape, and
process are at the heart of the materials selection process.
• Out of the 100,000 materials available for use by engineers, the
down selection process starts by using design constraints to limit
choices of materials. Thus the properties of the materials MUST
be known.
• Data for materials properties are needed at every stage of the
design process.
Design Process
The design process is changing due to global pressures and new
technology.
Global competitiveness is pushing:
• Shorter lead times
• Shorter delivery times
• Flexibility in product variations
• Higher quality
Environmental issues are becoming increasingly important.
• Energy and Materials optimization in a life-cycle design
• The manufacturer is responsible for environmentally safe disposal.
– Insurance companies demand proof.
– Green labels give competitive edge.
• Environmental and regulatory agencies demand life cycle design
documentation.
Design Process
Technology of Materials Design and Applications
• Requires high-speed computer with large and fast memories
• Data base management programs
• Scanners/digitizers/numerical fitting software
• Simulations before prototype production.
• Simulations before design experimentation.
Engineering Megatrends
Megatrends are revolutioning new product design
•
•
•
•
•
•
•
•
•
•
•
More powerful computer tools
Design for export
Design for manufacturing
Outsourcing engineering design
Quest for quality
Smart machines
Faster design cycles
Taylor-made materials
Life-cycle engineering
Engineering without walls
Micro and nanoscale designs
Materials Properties for Design
Physical Properties
• Crystal structure
• Density
• Melting point
• Viscosity
• Vapor pressure
• Porosity
Mechanical Properties
• Hardness
• Modulus of elasticity
• Poisson’s ratio
• Yield strength
• Shear strength
• Fatigue
• Fracture stength
• Creep
• Wear
• Erosion
Materials Properties for Design
Electrical Properties
• Conductivity
• Mobility of carriers
• Carrier lifetime
• Charge density
• Dielectric constant
Photonic Properties
• Transparency
• Reflectivity
• Refractive index
• Emissivity & Absorptivity
Thermal Properties
• Conductivity
• Specific heat
• Coefficient of expansion
• Emissivity
• Ablation rate
Materials Properties for Design
Chemical Properties
• Oxidation
• Hydration
• Corrosion
• Electronegativity
• Electropositivity
• Molecular weight
• Molecular number
(periodic table)
Magnetic Properties
• Permeability
• Hard versus soft
• Hysteresis
Nuclear Properties
• Half life
• Absorption cross-section
• Stability
Materials Properties for Design
Fabrication Properties
• Formability
• Machinability
• Weldability
• Castability
• Hardenability
• Heat treatability
Representative strengths of various categories of materials.
National Aerospace Plane (NASP) – X-33 prototype, which
uses different materials for different parts.
Realization for the Need of Materials Design
Major changes in F1 cars
• carbon composite brake pads
• ceramic capped cylinder heads
• electronic fuel injection system
• electronic brakes and accelerators
Need for:
• light weight, high
strength materials
• high strength, high
temperature materials
Polymers being used to make an exact reproduction of a face.
Electronic materials
being used as a
blanket.
Photonic materials
being used in an
advanced
camouflage
device.
Cost of Materials
Materials typically are considered on the basis of performance, cost
and processing ease.
• Cost of materials can significantly affect the final product cost
with 50% being the rule
• Automobile materials typically are 70% of the manufacturing
costs.
• Ship materials are nominally 45% of the manufacturing costs
• In electronic devices, such as computers, materials can be 75% of
the manufacturing costs.