Constraints (definition + types)
Effect of external forces on objects
Compression: crush
Tension: stretch
Torsion: twist
Deflection: bend
Shearing: cut
Deformation (definition)
Constraints have a tendency to deform objects
Types of deformation
Elastic: temporary change, constraint removed, returns to orignal shape
Plastic: permanent change in the shape or dimensions of the material
Fracture: material breaks
Mechanical Properties
- Hardness: Ability to resist indentation, abrasion (scratches) deformation
- Elasticity: Ability to deform & return to its original shape after constraint removed
- Plasticity: Doesn’t return to its original shape after stress, can be shaped
- Resilience: Ability to resist shocks without breaking, often deform and return to original shape
- Stiffness: Ability to retain shape when subjected to constraint (no bending though)
- Toughness: Ability to absorb energy and plastically deform without fracturing (plastic)
- Compressive strength: Resist compression
- Tensile strength: Resist tension
- Shearing strength: Resist shearing
- Ductility: Manufacturing metals Stretching into wire without breaking
- Malleability: Manufacturing metals Flattened into sheet or bent (shaped) without breaking
Electro-chemical properties
- Chemical neutrality: Ability to be chemically inactive; resist chemicals
- Resistance to corrosion: Prevent formation of rust; resist effects of corrosive substances
- Electrical conductivity: Ability to carry an electric current
- Heat resistance or conductivity: Ability to resist or transmit heat
- Lightness*: A property of low density materials
Degradation
Decline in properties due to effects of environment
Protection
Application procedures to prevent/delay degradation: protective coating
- Zinc coating (galvanization), anti-rust - metals
- Incorporating pigments and/or antioxidants - plastics
- Applying paint or varnish, waterproof coating - any materials
Wood
Organic matter from trees
Deciduous: slow growth, hardwood
Coniferous: fast growth, softwood
- x conduction of heat and electricity
- needs to be treated (fungus, insects, water)
Metals
Alloys
- Conductors of heat and electricity
- grease, paint, phosphate (prevent rust)
Ceramics
Inorganic material (silicon dioxide SiO2)
- x conductor of heat and electricity
- hard (not resilient)
- stiff
- heat resistance
- corrosion resistance
- waterproof
Thermoplastics
Soften and melt if heat applied
- X conductors of heat and electricity
- elastic
- light
- chemical neutrality
- corrosion resistance
- resilient
Thermosets (Thermosetting plastics)
Once formed, doesn’t soften or melt when heat applied
- x conductors of heat and electricity
- hard
- stiff
- heat resistant
- corrosion resistant
- resilient
Links
Direct vs Indirect: Does it have something that helps connect to?
Rigid vs Flexible: Solid or bendable?
Removable or Non-Removable: Does it damage the system when removing?
Complete vs Partial: Does it move together or individually?
Guiding
Translational, helical, rotational
Motion transmission systems
Rotational to rotational
- Friction gears (Reversible) - no teeth
- Pulley belt (Reversible) - no teeth
- Gear Train (Reversible) - teeth
- Chain Sprocket (Reversible) - teeth
- Worm Gear (not reversible) - guitar pegs
Formula for transmission speed and size
Speed A x Size A = Speed B x Size B
Motion transformation system
Rotational to Translational (Vice versa)
Screw gear (nut fixed or screw fixed) - not reversible
Can follower (cam controls) - not reversible
Slider crank - reversible
Rack and Pinion (circle) - reversible
