Chapter 12 - The Technological World Flashcards
What is a constraint?
The effect an external force has on a certain material
What are the five types of constraints?
Compression, tension, torsion, shearing, deflection.
What is compression? (description, symbol, example)
- Description: crushing
- Symbol: —–> <—–
- Example: Hands squeezing a wet sponge
What is deflection? (description, symbol, example)
- Description: Bending
- Symbol: |î|
- Example: A fish bending a finishing rod
What is tension? (description, symbol, example)
- Description: Stretching
- Symbol: <—- —->
- Example: rope in a tug of war
What is torsion? (description, symbol, example)
- Description: Twisting
- Symbol: rotating
- Example: wringing out a towel
What is shearing? (description, symbol, example)
- Description: Cutting
- Symbol: —-> | ⇽—-
- Example: Scissors cutting paper
What are the three types of deformations?
- Elastic
- Plastic.
- Fracture
What is an elastic type of deformation?
Temporary change in shape or dimensions of the material. Material will automatically return to its original form.
What is a plastic type of deformation?
Permanent change in the shape or dimensions, material remains deformed.
What is a fracture type of deformation?
Material Breaks.
What are the six Mechanical Properties of Materials?
- Hardness
- Elasticity
- Resilience
- Ductility
- Malleability
- Stiffness
What is the mechanical property of hardness?
Ability to resist indentation/scratches
What is Elasticity?
Ability to return to their original shape after undergoing a constraint.
What is resilience?
Ability to resist shocks without breaking
What is ductility?
Ability to be stretched without breaking
What is malleability?
Ability to be flattened or bent without breaking
What is stiffness?
Ability to retain their shapes when subjected to various constraints.
What are the three other properties of mechanical materials?
- Resistance to corrosion
- Electrical conductivity
- Thermal conductivity
What is resistance to corrosion?
Ability to resist the formation of rust or
degradation by acids, salt, water, etc.
What is electrical conductivity?
Ability to carry and electrical current
What is thermal conductivity?
Ability to transmit heat
What is degradation?
Decline in a material’s properties due to the effects of the surrounding environment.
What is protection of a material?
Application of a substance to a material to prevent or delay its degradation.
What are the 2 categories of wood, where do they come from?
- Hardwood → Deciduous trees
- Softwood → Conifers
What is modeified wood?
Wood mixed with other substances (glue, plastics, preservatives)
What are three problems with wood?
- Rotting
- Infestation
- Mold
What are two solutions to the problems caused when using wood?
- Coating
- Treated wood
What are problems with ceramics?
- Acids and bases can degrade ceramics
- A sudden change in temperature can deteriorate the properties of ceramic
What are problems with metals and alloys?
- They rust
What is the solutions to the problems of metals and alloys?
- Coating!!
What are plastics made out of?
Fossil fules
What is a thermoplastic?
Become soft when heated and hard when cooled (can be recycled)
What is a thermosetting plastic?
Remains permanently hard when heated (more resilient)
What are the three problems for plastic degradation?
- Water absorbsion
- Oxidation
- Uv rays
What are the three solutions to the problems regarding plastics?
- Waterproof coating
- Antioxidant material
- pigment to absorb UV ray
What are the two combination of materials used for composites?
- Reinforcement (provides strength)
- Matrix (surrounds and supports the reinforcement)
