Engineering Unit: Grade 9 science IB Flashcards
What is a Mechanical Property?
A mechanical property determines how a material will react when it is subjected to one or more mechanical constraints.
List the types of Mechanical Properties:
- Hardness (resists penetration)
- Elasticity (returns to original shape)
- Resilience (resists physical impacts)
- Ductility (stretches without breaking)
- Malleability (flattens or bends without breaking)
- Tensile strength (resists tension, elastic)
What is a mechanical constraint?
A mechanical constraint describes the stress produced within a material when it is subjected to one or more external forces; mechanical constraints produce various effects inside a material.
List the 5 principle mechanical constraints:
- Compression (crushes materials)
- Tension (force that stretches materials)
- Torsion (force that twists materials)
- Bending (force that bends materials)
- Shearing (force that cuts/tears materials)
What are the 4 mechanical functions?
- Link
- Guide
- Lubrication
- Seal
Define a link:
Links are used to connect 2 or more parts of an object.
Define a guide:
Forces a part to follow a certain guiding motion (translation/rotation)
Definition of lubrication:
Reduces friction by technical means.
Definition of seal:
Prevents a gas or liquid from escaping.
Types of guiding:
Rotations, Translation, Helical
Gear Train:
- Components of a gear train include and driver, and a follower, sometimes they also include intermediates.
- In a gear train each gear turns opposite in direction to the gear(s) directly beside it
- Reversible
- Motion Transmission system: rotation - rotation
- Should be lubricated
Chain and Sprocket systems:
- Components of a chain and sprocket system include gears, and a chain .
- In a chain and sprocket system gears within the train turn one way, and gears outsides the chain turn the opposite direction.
- Reversible
- Motion Transmission system: rotation - rotation
- Should be lubricated
Chain and Sprocket systems:
- Components of a chain and sprocket system include gears, and a chain .
- In a chain and sprocket system gears within the train turn one way, and gears outsides the chain turn the opposite direction.
- Reversible
- Motion Transmission system: rotation - rotation
- Should be lubricated
Friction gear system
- Components of a friction gear system include and driver, and a follower, sometimes they also include intermediates.
- In a friction gear system each gear turns opposite in direction to the gear(s) directly beside it
- Reversible
- Motion Transmission system: rotation - rotation
- Should NOT be lubricated
- Diameter = teeth (equivalent to gear train)
Belt and Pulley system
- Components of a belt and pulley system include pulleys (gears without teeth), and a belt.
- In a belt and pulley system pulleys within the belt turn one way, and pulleys outsides the belt turn the opposite direction.
- Reversible
- Motion Transmission a system: rotation - rotation
- Should NOT be lubricated
Wheel and worm-wheel system
- Components of a wheel and worm-wheel system include a worm-wheel (screw), whose rotation is transmitted to one or more wheels.
- In a wheel and worm-wheel system both the wheel and worm-wheel both rotate in the same direction.
- NOT reversible, the worm-wheel is ALWAYS the driver
- Motion Transmission system: rotation - rotation
- Should be lubricated
Rack and Pinion system
- Contains at least one gear called a pinion, and a straight, teethed bar called a rack,
- Reversible
- Motion Transformation System : Rotation - translation (& vice versa)
- Should be lubricated
Screw-Gear System
- Contains a screw and a nut
- Irreversible; nut rotates and transforms into the translational motion in the screw. The nut it always the driver
- Motion Transformation System : Rotation - translation
- Should be lubricated
Cam and follower system
- Contains a cam (egg shaped piece), and a follower (a stick that bobs).
- NOT Reversible, Cam is ALWAYS driver
*Follower follows…lol…. It is driven. - Cam rotates, Follower translates
- Motion Transformation System : Rotation - translation
- Should NOT be lubricated
Slider-crank mechanism
- Contains a crank, slider, and guide.
- Reversible, crank and slider can switch which is driver/driven
- Crank rotates like wheels, slider translates like a piston
- Motion Transformation System : Rotation - translation (& vice versa)
- Should be lubricated
Speed Change!
Increase: Driver is bigger/has more teeth than driven
Decrease: Driven is smaller/has less teeth than driven
No Change: Driver and driven are the same in size/teeth
Define exploded view
Shows all components of an object separated from each other.
