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MSc Eng. Geology > Structures and Mechanisms > Flashcards

Structures and Mechanisms Flashcards

1
Q

What is stress?

A

This is when a member is under compression. When something is under compression it is called a strut.

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2
Q

What is strain?

A

This is when a member experiences a tensile force. A member in tension is called a tie.

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3
Q

What is the formula for strain?

A

Strain = Change in Length/ Original Length

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4
Q

Does strain have a unit?

A

No.

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5
Q

What is the formula for stress?

A

Stress = Force/Area

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6
Q

Does stress have a unit?

A

Yes, it is measured in N/mm2.

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7
Q

What is a vector quantity?

A

A vector quantity has both a magnitude and a direction.

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8
Q

Give an example of a vector quantity.

A

Velocity, weight and force are all vector quantities.

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9
Q

What is the formula for the principle of moments?

A

∑ clockwise moments = ∑ anticlockwise moments

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10
Q

What are the formulae for the conditions of equilibrium?

A

Σ Fh = 0
Σ Fv = 0
Σ M = 0

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11
Q

What mechanism allows a motor to be disengaged from a gear system.

A

A clutch allows a motor to be disengaged from a gear system.

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12
Q

What does a bearing do?

A

A bearing supports a shaft and minimizes the energy lost due to friction.

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13
Q

What does a coupling do?

A

A coupling links an output to a gearbox or generator. A coupling also allows torque to be transmitted easily. They can also be disconnected for repairs.

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14
Q

What does a brake do?

A

A brake reduces the speed of rotation.

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15
Q

Give two examples of a brake.

A

Disk brake, V-brake, water brake, air brake and drum brake.

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16
Q

How does a disk brake work?

A

A disk brake works by pushing brake pads against a brake rotor with a set of calipers.

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17
Q

What are the advantages of a compound over a simple gear train?

A

A compound gear train allows a larger change in speed to be gained in a smaller space.

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18
Q

What does a ratchet and pawl do?

A

A ratchet and pawl stops rotation in one direction.

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19
Q

What does a worm and wheel do?

A

A worm and wheel allows a large change in speed and torque in a small space. It also rotates the direction of motion around 90 degrees.

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20
Q

What do bevel gears allow?

A

Bevel gears allows the direction of motion to be rotated around 90 degrees.

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21
Q

What are the advantages of belt drives?

A

Belt drives allow slippage, which is necessary if there are fragile components in a system. They are also cheap to replace if they break.

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22
Q

State the three main types of belts.

A

V belts, flat belts and toothed belts.

23
Q

State the advantages of chain drives over belt drives.

A

Chain drives allow a high force to be applied with no slippage.

24
Q

What does a cam do?

A

A cam changes rotary motion into oscillating or reciprocating.

25
Q

How is a cam used in an engine?

A

In an engine the cams open and close the valves which let air and fuel in, or exhaust gases out.

26
Q

What three things do all levers have in common?

A

All levers have a load, an effort and a fulcrum.

27
Q

What does EFL stand for? Give an example as well.

A

This means that the fulcrum is in the middle. An example of this is a tin opener.

28
Q

What does ELF stand for? Give an example.

A

This means that the load is in the middle. An example of this is a wheelbarrow.

29
Q

What does LEF stand for? Give an example.

A

This means that the effort is in the middle. An example of this is a fishing rod.

30
Q

What is the formula for a gear ratio?

A

Gear ratio = Driven/driver

31
Q

What is a simple gear train?

A

This is when two or more gears are meshed together.

32
Q

What is a compound gear train?

A

This is when there are two or more gears on one shaft.

33
Q

What is the formula for the velocity of gears?

A

Input speed x Input size = Output speed x Output size

34
Q

What is the formula for velocity ratio?

A

Velocity ratio = speed of input/speed of output

35
Q

What is the formula for torque?

A

T = Fr

36
Q

Explain what a dynamic force is.

A

This is when movement is involved. It is more noticeable and structures usually move.

37
Q

Explain what a static force is.

A

This is when there is no movement involved and structures don’t move.

38
Q

Explain what a bending force is.

A

A bending force is when something curves or flexes. It is often in structures with a force across their length.

39
Q

Explain what a shear force is.

A

This is when something is cut or torn, i.e: a pair of scissors.

40
Q

Explain what a torsion force is.

A

Torque is a torsion force, this is a twisting force, i.e: a screw or bolt.

41
Q

Explain what a compression force is.

A

This when there is a downward weight/pushing force on a member.

42
Q

Explain what a tensile force is.

A

This is when a member is experiencing a pulling force.

43
Q

What is rotational motion?

A

This is when something turns in a circle. For example a wheel or a CD.

44
Q

What is linear motion?

A

This is when something moves in a straight line.

45
Q

What is reciprocating motion?

A

This is a backwards and forwards motion in a straight line. For example a piston.

46
Q

What is oscillating motion?

A

This is a backwards and forwards motion, swinging in an arc. For example a swing.

47
Q

What do all mechanisms have in common?

A

All mechanisms: -involve some kind of motion.

                           - involve some kind of force.
                           - make a job easier to do.
                           - need some kind of input to       work.
                           - produce an output.
48
Q

Give the two main types of frame structures.

A

Cantilevered frame structures and truss frame structures.

49
Q

When analysing a cantilevered frame structure how do you find the forces and direction of the forces in each member?

A

You use nodal analysis. You choose a node with one known and two unknown forces, and then work out each force. DO NOT USE THE PRINCIPAL OF MOMENTS!

50
Q

When analysing a truss frame structure how do you find the forces and direction of forces in each member?

A

You treat it as a beam and use moments to find the reaction forces. Then you use resolution of forces the find the remaining forces.

51
Q

Name as many pneumatic actuators as possible.

A

Push button, plunger, roller, roller trip, solenoid, lever, diaphragm, pilot air, foot pedal, spring.

52
Q

What pneumatic control system is a shuttle valve used in?

A

OR control.

53
Q

How do you create a simple pneumatic AND control system?

A

You use two 3/2 valves in series.

54
Q

What is the full name of a 3/2 valve?

A

A three port, two state valve.

MSc Eng. Geology (50 decks)

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