Tutorials and Sustainability Flashcards
Sustainable development requires materials that minimize what?
Social, environmental and economic impact of development
Define sustainable development
Meets the needs of the present without compromising the ability of future generations to meet their needs
What parameters can control to support sustainability?
Choice of materials, their source, durability, mode of construction, design choices, energy use choices, maintenance
What are the 3 Rs in order of importance?
Reduce, reuse, recycle
Name and describe the three components of energy footprint
1) indirect: extraction, material transportation, processing and manufacturing
2) direct: transportation and construction of infrastructure
3) recurring: repair, maintenance, refurbishment, replacement
How bad is cement for environment?
Production of cement produces 8% of greenhouse gas emissions. Building operations contribute 17% of GHG emissions.
Name the 4 types of engineering materials
Metals and alloys, polymers, ceramics and glass, composites
Name the properties of metals and alloys
- Homogenous and recurring microstructure
- crystalline
- conductive electrically
- alloys are combos of 2 or more materials and their properties depend on proportion
Name the properties of ceramics and glasses (also what is glass made of)
Silicate
- non-metallic inorganic material
- insulating
- brittle
- homogeneous microstructure
Not highly crystalline hence brittle and clear (for glass). In fact, when making glass, we are ruining the crystalline microstructure of sand
Name the properties of polymers and plastics
- Chains of self repeating molecules
- Composed of hydrocarbons
- Some possible cross linking
- High degree of plasticity (shape and mouldable)
- Electrically insulating
Name the properties of composite materials
- 2+ engineering materials
- Huge variation in macroscopic properties
- Eg. reinforced concrete and fibre reinforced polymers
Stress vs Force?
Stress is force divided by area! Stresses can be applies in different axes (uni axial and triaxial, shear and normal)
What is elasticity and what is the name of the law associated with it?
Hooke’s Law
It’s the ability of the material to deform and return to its unreformed state
What is plastic deformation?
When deformation becomes permanent. Energy is lost destructively. Unloading could occur but the specimen won’t return to its undeformed shape. Brittle materials break without being plastic
What is strain rate and how does it affect materials?
It’s the rate of external applied loading. Material is constantly trying to get into equilibrium with the application of the forces. At fast rates, material has less time to adjust and so it’s more brittle and has less plastic deformation.
How does temperature affect materials?
At higher temperature, materials are more ductile. Lower = brittle duh
How does the degree of triaxiality affect materials?
Higher degree = more brittle because of negation of poisson effect. The material has no room to expand because loaded from every side and therefore it becomes brittle and has to break. With lower degree of triaxiality, poisson effect can take into place and allow deformation
Go to tutorial lecture 2, slide 42 and name each point on stress-strain curve. Also what is difference between Eng curve and true curve?
Slide 45-46 of same lecture
What does fatigue failure look like?
Microscopic defects that are loaded cyclically form cracks and eventually fail suddenly
What are crack intuition and crack propagation?
Crack initiation occurs at localized places where material cannot withstand load (usually at discontinuities and surface flaws). Crack propagation occurs from gradual widening of the crack due to cyclic loading. In fatigue, this creates beach patterns.
Describe fatigue limit for ferrous alloys (eg. steel)
Some stresses will never reach fatigue limit and thus will never fail. You can have an infinite number of cycles as long as you stay below the fatigue limit stress-cycle curve.
What is the equation for how much percentage of life you have left?
Sum of cycles/cycles to failure. If >= 1 then specimen will fail. Called the Palmgren-miner hypothesis
What is creep?
Long term plastic and permanent deformation under constant sustained loads below the the yield point. Creep is time dependent and there is more creep at higher temperatures and at higher loads.
What are the stages of creep (4)?
Initial elastic strain, primary creep, secondary (steady state) creep, tertiary creep
