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Semester 3 > Mechanical Basis > Flashcards

Mechanical Basis Flashcards

1
Q

definition of machine

A

a device that can achieve predetermined mechanical motion and it consists of numbers of fixed and moving bodies. it is used to provide significant forces to transform and transmit significant energy and power

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2
Q

characteristics of machine

A
  • design by mankind
  • convert energy
  • have relative and regular motion
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3
Q

definition of machinery

A
  • machine have more than 3 features, mechanism have 2 characteristics. machinery is the term used to cover both mechanism and machine
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4
Q

definition of machine element and catagory

A

basic element of manufacture. 2 catagories are
- general purpose parts/element common
- special parts/element peculiar

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5
Q

definition of link

A

a rigid structure that joined by numbers of machine element is a basic element in kinematic analysis

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6
Q

types of link

A

frame, driving, driven
- frame : the fixed and stationery link in mechanism
- driving link : link that moves according to the movement rule
- driven link : remaining link movement that follow driving link

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7
Q

kinematic pairs

A

every link must be kept permanently in contact with other link by some kind of connection with motion relative to them, in order to transform and transmit motion

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8
Q

types of kinematic pairs

A
  • revolute pair : pair that permits only relative rotation
  • sliding pair : pair that allow only relative rectilinear translation
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9
Q

degree of freedom

A

F = 3N - 2Pl -Ph

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10
Q

definition of planar linkage

A

kinematic pairs in a mechanism are lower pairs

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11
Q

types of 4 bar linkage

A
  • crank rocker mechanism
  • double rocker mechanism
  • double crank mechanism
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12
Q

match the diagram

A
  • arrow keluar is rotating
  • arrow dua masuk is swing
  • arrow keluar dari dalam is crank and oscillating
  • arrow dua keluar is translating
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13
Q

characteristics analysis of 4 bar linkages

A
  • pressure and transmission angle
  • dead point
  • quick return characteristics
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14
Q

what is dead point

A

rocker CD is input link and crank AB is output link. when the AB and the coupler BC is overlapping collinear, AB1C1D, and extended collinear AB2C2D. at that instant y=0degree. those two limitating positions are called dead point

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15
Q

deadpoint flywheel

A

when the rocker serves as the driver, the linkage is being driven through a deadpoint with the inertia of flywheel, fixed with driven crank

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16
Q

characteristics of quick return

A

if the crank is rotating at a constant speed, the oscillating link moves forward slowly and return quickly

17
Q

ΞΈ and K

A
  • the crank angle between 2 limitating position
  • the coefficient of travel speed variation for time ratio
18
Q

basic structure of cam mechanism

A
  • it has curved/grooved contour which is usually used for contiunous constant velocity rotation and some for oscillating reciprocal movement
19
Q

classification of cam mechanism

A
  • by the shape of the follower end : knife-edge, roller, flat-faced
  • by the shape of the cam : translating, plate, cylindrical
  • by the form of closure : force closure, form closure
20
Q

working process of cam mechanism

A
  • base circle
  • offset
  • total follower travel
  • cam angle for rise
  • cam angle for outer dwell
  • cam angle for inner dwell
  • cam angle for return
  • dispalcement curve of the follower
21
Q

follower motion curve

A
  • at the beginning and the end of the rise, the acceleration is positive and negative infinity. any of which will produce infinite inertia force.
  • although the inertial force would not be infinite, it will reach a considerable value which will result in the large amount of shock, called rigid impulsive and rigid jerk.
  • those 2 will produce a large vibration, high stress level and serious wear. it is only applied to low operations
22
Q

constant acceleration and deceleration motion

A

soft impulse/soft jerk. can be used for low/intermediate speed cams

23
Q

soft impulse/soft jerk

A

in acceleration plot, the acceleration jumps and will result in the abrupt changes in inertia force. the inertial force will be finite, instead of infinite so it will cause finite impulse or jerk

24
Q

fundamental law of gearing

A

in order to maintain a constant angular velocity ration, the shape of the teeth must be normal at the point of contact between 2 teeth always passes the fixed point

25
Q

involute curve

A

if the line rolls on a circle with a radius r6, the track of the line is called involute curve

26
Q

involute properties

A
  • 𝑁𝐾̅̅̅̅ = 𝐴𝑁
  • normal line is always tangent to base circle
  • shape depends upon the size of the base circle
  • length of common line unchanged
  • ## no involute curve inside the base circle
27
Q

spur gear nomenclatures

A
  • base circle
  • addendum circle
  • dedendum/root circle
  • circular pitch
  • tooth thickness
  • tooth space
  • reference circle
  • addendum/dedendum
  • base pitch
  • face width
28
Q

parameters of involute gears

A
  • module
  • pressure angle
  • coefficient of addendum and coefficient of clearance
  • formula of standard spur
29
Q

pressure angle, coefficient of addendum, coeffiecient of clearance

A

the pressure angle of tooth profile on the ref circle, where ha is the coa, c

30
Q

condition of engaging for a pair of gears

A

module and pressure angle of 2 meshing gears must be the same, respectively

31
Q

reference centre distance

A

a = r1 + r2 = m/2 (z1 + z2)

32
Q

gear manufacture method

A
  • milling
  • generating
  • molding
33
Q

speed ratio

A
  • the speed ratio of a worm set is equal to the ratio of the teeth on worm wheel to the number of threads on the worm.

i12 = w1/w2 = z1 + z2 = d2/d1tany1

the left/right hand rule of worm can be used to determined the rotation of the worm wheel

34
Q

failure modes of gear type

A
  • fracture of teeth
  • pitting
  • wear of teeth
  • seizure of teeth
  • plastic deformation
35
Q

types of belt drives

A
  • flat
  • v belt
  • v ribbed
  • synchronous
36
Q

Fe calculation

A

Fe = Ff = F1 - F2

37
Q

P calculation

A

P = FeV/1000

38
Q

maximum effective tension FEC

A
  • initial static tensile force
  • wrap angle
  • friction coeffiecient

Semester 3 (4 decks)

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