Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

DT > Technical Understanding 1 > Flashcards

Technical Understanding 1 Flashcards

1
Q

how can structural integrity be achieved by strengthening

A
  • reinforcing or protecting the material

- reinforcing the assembly of parts within the product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how can you protect a product from complete failure if it is over-stressed

A
  • by using sacrificial parts e.g. fuses, elbow pads
  • designed to be the weakest so they will break first to protect more significant parts
  • usually easy to replace
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

processes to ensure structural integrity: material reinforcing

A
  • corner protectors e.g. on speaker cabinets

- plain bearing is used to support a shaft

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

processes to ensure structural integrity: material stiffening

A
  • achieved by adding folds, ribs or webs (Eiffel tower)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

processes to ensure structural integrity: material protection

A
  • surface finish: paint, lacquer, galvanising, anodising
  • adding stabiliser to a polymer e.g. UV light to uPVC
  • preservative
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

processes to ensure structural integrity: triangulation

A
  • adding cross members to a rectangular frame
  • adding corner braces
  • adding gusset plates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are surface finishes and coatings used for

A
  • used to protect against wear, dirt, damage, corrosion and decay
  • enhances appearance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

vanishing and painting

A
  • attractive and hardwearing finish to woods
  • clear or colour, matt, satin or high-gloss finish
  • both heat and waterproof
  • applied with brush or spray
  • can be non-toxic but requires maintenance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

finishing timber

A
  • sanded before with glass paper, garnet paper, and wire wool
  • sanding sealer is a solvent based product that seals the surface and raises the wood fibres to be sanded
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

wax/polish and sealants

Timber

A
  • used when a natural appearance on wood is required
  • E.G. olive oil - used as a finish when the wood is going to come into contact with food (salad servers)
  • Danish or linseed oil - can be used on most woods; it needs 2 to 4 coats for the best protection
  • teak oil - for teak, made of linseed oil and silicone to give it a harder wearing surface

-beeswax is used in interior wooden furniture and gives a natural looking finish

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Preservative

Timber

A
  • can be applied by spraying or brushing but pressure treatment is preferred

Eg

  • tar oil: highly water repellent, has an odour. Uses are bridges, railway sleepers
  • immersion treatments: timber is placed in a bath of preservative, heated then cooled
  • pressure impregnation: wood is put in a vacuum and pressure is applied until the timber refuses to absorb more
  • tantalising : chemicals become chemically fixed into the timber and cannot be removed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Powder coatings

Timber

A
  • more durable on manufactured boards than paint
  • impact, chip, temperature and stain resistant
  • involves the use of electrostatic charge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Finishes for metals

A
  • painting or lacquering
  • needs to be prepared and cleaned
  • enamelling - uses: decorative jewellery
  • buffing: creates a shine
  • polishing: removes deep scratches
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Dip coating/plastic coating

A

Mainly on metals. They are heated then dipped and a gel coating is formed, using powder and a fluidised bed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Electroplating

A
  • coating objects with a thin layer of metal using electricity
  • E.G.gold, silver, chromium, tin, nickel and zinc
  • done by electrolysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Galvanising

A
  • zinc is used to cover steel
  • consists of: surface preparation, galvanising and final inspection
  • steel needs to be perfectly clean
  • needs flux: prevents oxidisation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Mechanism definition

A

A mechanism is a device that transforms an input motion and force into a desired output motion and force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How to work out mechanical advantages of force

A

MA = output force/input force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Types of motion

A

Rotary
Linear
Reciprocating
Oscillating

20
Q

What is a lever

A

A lever consist of a bar which pivots on a fulcrum. The input force is called effort, the output force is called load

21
Q

What is a compound lever

A

Consists of two or more simple levers working together E.G.pliers

22
Q

What is a linkage

A

It is an assembly parts used to direct forces and movement where it is needed, it can change the direction of motion and convert between different types of motion

23
Q

Bevel gears

A
  • transfers direction of 90 degrees, but can be other ages as well
  • the 2 gears are different sizes therefore there is not a 1:1 gear ratio
24
Q

Mitre gears

A
  • 1:1 gear ratio

- pair of identical bevel gears

25
Q

helical gears

A
  • teeth cut at an angle

- therefore run quieter because the teeth mesh gradually

26
Q

A rack and pinion

A
  • changes between rotary and linear motion e.g. lifts
27
Q

worm gears

A
  • 1 continued tooth ‘single thread’
  • 90 degrees drive direction
  • experience large frictional forces and wear quickly
  • self locking
28
Q

Chain and sprocket drive

A
  • input and output shafts are placed a distance apart, linked by a chain and they both rotate in the same direction
  • gear ratio = no. of teeth ion output/ no. of teeth on input
29
Q

belt and pulley drives

A
  • quieter belt and used in lower load applications
  • v shaped belt provides a large contact area and so ensures less slippage
  • toothed belts are used when slipping mustn’t occur
  • must always have correct tension (too much = high friction losses, too little = chain may slip/jump of sprocket)
30
Q

screw threads

A

changes rotary motion into linear

- uses: 3D printers, where accurate linear positioning is required

31
Q

what is a cam

A

a cam and followers converts motion to reciprocating motion

  • dwell - where no follower motion occurs
  • stroke - maximum distance the follower rises
32
Q

epicyclic gears

A

4 main components: sun gear, planetary pinions/planet carrier, ring gear

  • 1 of 3 must stay stationary
  • if power is fed into any 2 components, the whole train rotates 1:1
33
Q

benefits of epicyclic gears

A
  • the output shaft is in direct line (co-Linear) with inout shaft
  • they are very rugged, capable of carrying large torques in a compact passage
  • several gear ratios can be obtained by braking different components in the system
34
Q

uses of epicyclic gears

A
  • car engines
  • electric drills
  • compact gear box on DC motors
35
Q

What is a bearing

A

A component which supports a moving part and allows it to move only in the desired direction

  • used to support a drive shaft so it can rotate freely
  • The forces on the shaft can be radial (sideways) or axial (pushes the shaft along its axis)
36
Q

What is a plain bearing

A

Passing the shaft through a hard wearing metal which offers low resistance, made of polymers e.g. nylon
- lubricated and usually sealed

37
Q

What is a ball bearing

A

Consists of metal balls running between two races, handle radial loads
- lubricated and usually sealed

38
Q

What is a tapered roller bearing

A

Due to the cone shape, they can support axial and radial loads

A thrust bearing uses - only axial

39
Q

What are fluid bearings for

A

For high-performance and high-speed applications
- they can be used to support shaft within a sleeve of high-pressure oil or air. Such bearings provide exceedingly low friction and almost nowhere

40
Q

Efficiency in mechanical systems

A

An ideal mechanism transfers power without adding to or subtracting from it. It doesn’t lose energy due to friction, or by generating sound or heat/wear.

However friction is always present so the equations are used to work out the efficiency

41
Q

What are the efficiencies of a typical gear system

A
  • epicyclic gear train 97%
  • three stage compound gear train 94%
  • worm drive could be as low as 20%
42
Q

what are pneumatics

A
  • they are linear actuators in which the driving force is provided by a supply of compressed air
  • the stroke of the cylinder is the distance travelled by the pushrod
  • cylinders controlled by valves - 3 port and 5 port depending on application
43
Q

single acting cylinder SAC

A
  • contains a spring
  • compressed air is supplied, the piston and pushrod moves outwards until the ends top, air pressure is removed, air supply can escape
  • have a strong out stroke but weak in stroke
44
Q

double acting cylinder DAC

A
  • 2 air ports

- both out stroke and in stroke are under air pressure

45
Q

uses of pneumatics and hydraulics

A
  • pneumatics in food industries (no problem if it leaks unlike the oil used in hydraulics)
  • hydraulics - where accurate control and large force is required
46
Q

Explain how an open loop control system works in a product such as a microwave oven

A
  • In an open loop system there is no feedback, the
    output is not measured/does not feedback to the
    input.
  • no sensors to detect the output (the food cooking), so the input (the heat/time) does not detect if the food has been
    cooked.
47
Q

Explain how the graph shows that this sensor produces a linear output in response to the applied force.

A

There is a positive correlation relationship between
the two variables, where one variable increases while the
other increases

DT (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions