Stress and Sound

Question 1

Stress

Answer 1

An internal force in an object which resists any attempt by an external force to change the shape of the object

Question 2

Types of Stress

Answer 2

Tension

Compression

Shear

Torsion

Bending

Question 3

Tension

Answer 3

A stress that tries to pull an object apart

Two forces acting in the opposite direction outward, along the same line

Question 4

Compression

Answer 4

A stress that tries to push an object together

Two forces acting in opposite direction inward, along the same line

Question 5

Shear

Answer 5

A stress that tries to slide objects apart

Two forces acting in opposite direction (inward or outward) along different lines

Question 6

Torsion

Answer 6

A twisting force

Two forces applied in opposite direction, along the same axis

Question 7

Bending

Answer 7

A combination of tension, compression, and shear

Question 8

Strain

Answer 8

The deformation of a material caused by stress

Question 9

Elasticity

Answer 9

The property of a material to return to its original shape after being placed under an external stress

Question 10

Elastic Limit

Answer 10

The greatest external stress an elastic solid can sustain without undergoing permanent (plastic) deformation

Question 11

Yield Point

Answer 11

The point where a material will continue to deform without applying additional force other than gravity

Question 12

Ultimate Strength

Answer 12

Point where the part will break

Question 13

Hook’s Law

Answer 13

Stress is equal to strain until the elastic limit is exceeded

Question 14

Requirements for Sound to Exist

Answer 14

Source

Transmission medium

Receptor

Question 15

Waves

Answer 15

Consists of crests and troughs

Question 16

Wave Length

Answer 16

The distance between crests

Question 17

Cycle

Answer 17

One complete crest and trough

Question 18

Frequency

Answer 18

The number of cycles that pass a given point in one second

Question 19

Frequency Measurement Units

Answer 19

Hertz

One Herts is equal to one cycle per second

Question 20

Speed of Sound

Answer 20

Changes as both the density and the temperature of the medium changes

Question 21

Speed of Sound and Density

Answer 21

The speed of sound is directly proportional to the density of the transmission medium

Sound travels 15 times faster through steel as it does through the air

Question 22

Speed of Sound and Temperature

Answer 22

The speed of sound is directly proportional to the temperature of the medium

The speed of sound will change by 1.1 fps. For each degree of Farhenheit temperature change

Question 23

Speed of Sound at Sea Level Under Standard Conditions

Answer 23

1116 fps = Mach 1
761 mph = Mach 1

Question 24

Subsonic

Answer 24

True airspeed less than Mach 1

Question 25

Mach Critical

Answer 25

.72-.85 subsonic airspeed The subsonic airspeed at which a shock wave will start to develop on an aircraft's wing horizontal stabilizer and cockpit

Question 26

Transonic

Answer 26

True airspeed passing through Mach 1

Question 27

Supersonic

Answer 27

True airspeed above Mach 1

Question 28

Doppler Effect

Answer 28

A frequency shift caused by the relative motion between the source and receptor

Question 29

Fuselage

Answer 29

Main body of the aircraft

Question 30

Truss

Answer 30

Pratt truss Warren truss

Question 31

Pratt Truss

Answer 31

Box like frame Not very strong

Question 32

Warren Truss

Answer 32

Triangular frame Strongest truss type frame

Question 33

Monocoque (4)

Answer 33

Old metal and wood covered aircraft Skin is stretched around vertical members called rings and formers Skin gives the structure strength, holds the fuselage rigid and requires a thick skin Dents, cracks cause a rapid failure

Question 34

Semi-Monocoque

Answer 34

Most modern metal covered aircraft are of this type Along with the vertical. This structure also incorporates longitudinal members called longerons - Longerons and stingers - Bending loads are taken up the longitudinal members. Therefore, skin thickness can be reduced

Question 35

Bulkheads

Answer 35

Used attachment points, and pressurization sections

Question 36

Rings and Formers

Answer 36

Hold the fuselage and shape

Question 37

Longerons

Answer 37

Heaviest members extends across several vertical members Takes up primary bending load

Question 38

Stringers

Answer 38

Lightweight, maintain shape of the structure

Question 39

Guessets

Answer 39

Used at the intersection of vertical and horizontal members Add strength and stiffness to the airframe

Question 40

Aircraft Skin

Answer 40

Monocoque and semi-monocoque aircraft have stressed skin Skin is under constant tension, compression, bending and torsion loads NOTE: Even small cracks are critical

Question 41

Pylons

Answer 41

Provide mounting points for engines and external stores

Question 42

Nacelles

Answer 42

Smooth airflow and reduce the drag around engines, fuel tanks, etc...

Question 43

Wings

Answer 43

Main lifting body of the aircraft May be designed to house wheels, supports, contain fuel, mount flight controls, etc...

Question 44

Metal Wings

Answer 44

During flight, wing is subject to bending loads Lower skin more critical to repar than lower wing (look up and confirm in book) Lower skin under a tension load Upper skin under a compression load

Question 45

Semi-Cantilever

Answer 45

Requires extra bracing

Question 46

Landind Struts

Answer 46

On a low wing aircraft

Question 47

Lifting Struts

Answer 47

On a high wing aircraft

Question 48

Cantilever wing

Answer 48

Requires no external bracing and has a heavy constructed center section

Question 49

Spars

Answer 49

Runs the span of the wind from the wing root to the wing tip The principal structural component of the main load bearing member Wings may have a single or multi-spar design

Question 50

Wings contain

Answer 50

Spars, ribs, stringers, and bulkheads

Question 51

Wing Covering Materials

Answer 51

Metal Composite material Doped fabric Plywood