Brainscape's Knowledge GenomeTM

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


See full index

NDT Level-3 ( Pual E. Mix - By Wilay & Sons) > 2- Acoustic Emissions > Flashcards

2- Acoustic Emissions Flashcards

1
Q

,,,,,,, testing is based on the fact that solid
materials emit sonic or ultrasonic acoustic emissions when they are mechanically or thermally stressed to the point where deformation or fracturing occurs

A

Acoustic emission

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

Acoustic emission testing is based on the fact that solid materials emit ,,,,, or ,,,, emissions when they are mechanically or thermally ,,,,,, to the point where deformation or fracturing occurs

A

sonic
ultrasonic acoustic
stressed

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

During plastic deformation, dislocations move through the material’s crystal lattice structure producing ,,,,,,,AE signals, which can be measured only over short distances under laboratory conditions

A

low-amplitude

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

The ,,,,,,method detects, locates, identifies, and displays flaw data for the stressed object the
moment the flaw is created

A

AE test

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

flaws can not be retested by the ,,,,, method

A

AE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Almost all materials produce acoustic emissions when

they are stressed beyond their ,,,,, to ,,,,,,

A

normal design ranges

final failure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

first practical use of AE occurred in about ,,,,,, bc

A

6500

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

the father of modern AE testing was ,,,,,, of Germany

A

Josef Kaiser

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

A short, transient AE event is produced by a very fast release of elastic energy for a specific ,,,,, movement

A

dislocation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The ,,,,,,,, is the source of the elastic wave that propagates in ,,,,,,directions and cannot be stopped

A

local dislocation

all

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

On flat surfaces, the wave propagates as ,,,,,, around the source

A

concentric circles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

amplitude of the concentric waves is attenuated with ,,,,,, time and distance

A

increasing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

The maximum distance where an AE event can be detected depends on ,,,,,,,,

A

material properties,
geometry of the test object,
its content and
environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

On ,,,,,, or ,,,,, surfaces, AE events can be detected at ,,,,,, meters, which is a great advantage for this method

A

flat
cylindrical
several

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

With tank bottom testing, waves are analyzed that propagate through the liquid from the source to the ,,,,,,

A

tank wall

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Without liquid in the tank, the waves would be greatly ,,,

A

attenuated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

liquid-filled pipelines where the maximum distance AE events can be detected is ,,,,,, than in gas-filled tubes because the AE signal is attenuated ,,,,, in the liquid
volume than in thin-walled tubing

A

longer

less

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

AE waves reach the sensors with certain delays that depend on the position of the ,,,,,

A

AE source

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

The position of the source can be calculated using the

,,,,,,,. This is known as,,,,,,

A

different arrival times

“location calculation.”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

AE testing can be a process chain consisting of the following
steps:

A
  • Test object and application of load
  • Source mechanisms(releasing elastic energy)
  • Wave propagation (from the source to the sensor)
  • Sensors:
  • Acquisition of measurement data
  • Display of measurement data
  • Evaluation of the display
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Material properties and environmental conditions influence the start of the release of ,,,,, (i.e., the start of crack formation).

A

elastic energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

There are two types of AE signals,,,,,,

A

transient ( or bursts)

continuous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

starting and ending points of the transient signal are clearly differentiated from ,,,,,,

A

background noise

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

With continuous AE signals, ,,,,, and ,,,,, variations can be seen but the signal ,,,, thereby appearing continuous

A

amplitude
frequency
never ends

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

,,,,,,, filters are used to minimize background noise while enhancing the AE signal.

A

band pass

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Digital systems sample the AE signal every ,,,, or ,,,,, times a second

A

100ns

10 million

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

time interval between first threshold crossing and peak

amplitude is known as

A

Rise Time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

time interval between first and last threshold crossing

A

Signal Duration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

RMS

A

Root mean square

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

AE bursts are produced by both ,,,,and ,,,,

A

defects

background noise

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

,,,,, is one of the most important burst features

A

Peak amplitude

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

In most cases, bursts with less than ,,,,, crossings and durations ,,,,, are regarded as unwanted noise signals

A

three threshold

less than 3 ms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

,,,,, usually indicate electrical noise peaks if they arrive at all channels at ,,,,,

A

Very short signals

the same time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Coupling agents are crucial to the quality of ,,,,,

A

sensor coupling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

coupling agent provide good ,,,,, between the ,,,,, and the ,,,,,,of the test object

A

acoustic contact

sensor and surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Care must be taken to assure couplant is selected so

that it is acceptable at the normal ,,,, and does not ,,,, the test object’s surface

A

test temperature

corrode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

A variety of ,,,,,, are available for industrial application

A

silicone greases (coupling agent)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

coupling layer should be made as ,,,,, as possible by firmly pressing the sensor ,,,, the test object’s surface

A

thin

against

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Quality of coupling must be verified through ,,,,

A

pencil lead break or automatic coupling test

40
Q

,,,,, type of sensors convert ,,,,,, into ,,,,,signals

A

Piezoelectric
mechanical waves
electrical AE

41
Q

Piezoelectric sensor are ,,,, and more ,,,, than other sensor techniques such as ,,,,,,

A

hardy
sensitive
capacitive, electrodynamic, or laser-optical.

42
Q

When testing metal vessels for integrity, frequencies between ,,,, and,,,, are often used

A

100 Hz

300kHz

43
Q

At frequencies range 100 Hz to 300kHz, the sensors have a resonance of about ,,,,,

A

150kHz

44
Q

Piezoelectric sensors, cover the range of 150 to 300kHz with a variation of sensitivity of about ,,,,

A

6dB

45
Q

The resonant frequency indirectly determines the,,,,, of the sensor

A

spatial range

46
Q

High-frequency sound attenuates ,,,,, so it has a shorter ,,,,,.

A

faster

detection distance

47
Q

Background noises coming from longer distances

typically consist of frequency components below ,,,,,

A

100kHz

48
Q

For testing tank bottoms, sensors with a high sensitivity down to ,,,,,,are required because these signals must run for ,,,,,,.

A

25kHz

long distances

49
Q

Sensors often contain built-in ,,,,, and are attached to ,,,,, using magnetic holding devices

A

pre-amlifiers

magnetic test objects

50
Q

Typically, the ,,,,, power supply

for the preamplifiers is fed through the signal cable and can have a length of several hundred meters

A

28 VDC

51
Q

The sensitivity of piezoelectric sensors can be as high as ,,,,,,

A

1000V/mm

52
Q

a displacement of 0.1 picometer (pm) generates a ,,,,,,signal that can be easily distinguished from electrical noise, which is about ,,,,,,

A

100 mVpk

10 mVpk

53
Q

For comparison purposes, the atomic radii of the elements are in the range of 150pm with manganese at ,,,,, and lead at ,,,,

A

112pm

175pm

54
Q 
Types of AE sensors are; 
S.....
A....
D....
AD..
A

Single
Compact Single
Differential
Compact Differential

55
Q

,,,,,,,, sensors are typically used when there is a degradation of the AE signal by ,,,,, or ,,,,,, interferences.

A

Differential
electrostatic
electromagnetic

56
Q

When testing magnetic materials, sensors are usually attached to the test object using ,,,,

A

magnetic holders

57
Q

When nonmagnetic objects are tested, ,,,,,, may be used for sensor hold-down

A

elastic ties, tape, clamps, and glue

58
Q

cable connects the sensor with the preamplifier and should not be longer than ,,,,, because of the capacitance load on the sensor

A

1.2m

59
Q

The ,,,,,, inside the channel is used to eliminate noise sources and matches the measurement chain to the requirements of the application

A

frequency filter

60
Q

The ,,,, to ,,,, filter is used for tank bottom tests where leakage and corrosion may be problems

A

20 to 100kHz

61
Q

The ,,,,to ,,,,, filter is used for integrity studies of

metallic components.

A

100 to 300kHz

62
Q

Filters with frequencies above ,,,,, can be used where there are short distances between sensors

A

300kHz

63
Q

,,,,,, converters are used to digitize the filtered AE signals.

A

A/D ( analog to digital )

64
Q

A continuous sampling rate of ,,,, or ,,,,,measurement values per second per channel is used for feature extraction, which is processed in real time.

A

10MHz or 10 million

65
Q

FPGAs

A

field programmable gate arrays

66
Q

Optional transient recorders provide a way to store large amounts of information about complex ,,,,

A

AE waves

67
Q

The transient recorder is an optional addition to the

channel ,,,,

A

plug-in

68
Q

The ,,,,temporarily stores data when the CPU is busy with other tasks and cannot accept more data

A

data buffer

69
Q

The difference distance between a defect source and other sensors equals the ,,,,,

A

arrival time difference times the sound velocity

70
Q

The defect location calculation is based on the ,,,,,, of the AE signal propagating from its source to different sensors

A

arrival time differences

71
Q

AE wave is propagating in ,,, from its source and arrives at different sensors at different times.

A

concentric circles

72
Q

This time delay is proportional to the,,,,

A

distance between the sensor and the source

73
Q

,,,,,, is a mathematical way to determine the point density within a certain area, marking those areas of high point density by colored rectangles or circles

A

Clustering

74
Q

Advantages of AE testing;

A

-Pneumatic pressure testing can minimize potential overdesign of tank support systems.
- during pressurization provides in-depth information
beyond the statements—failure, leakage, or noticeable deformation
during test.
- the pressure system can be tested within standard operating conditions and acceptable temperature ranges

75
Q

AE Testing Advantages by Operating Medium: (Gas or Liquid);

A
  • Minimizes downtime caused by removal of the tank working medium if this medium is used for pressurization
  • Minimizes expensive drying operations following tank de-inventorying (as required with hydrotesting).
  • Minimizes de-inventorying water and subsequent decontamination expenses.
  • Minimizes the problem of catalysts becoming unstable in chemical reactors during de-inventorying operations.
  • AE testing can detect corrosion and minimize or eliminate the need for internal inspection.
76
Q

AE Testing advantages Compared to Other NDT Methods;

A
  • monitors the dynamic reaction of the test object passively, without intervention, when the load is applied.
  • In most cases, the AE method can detect sources at several meters distance from the sensor
  • AE provides 100% pressurized wall monitoring
  • AE provides real-time monitoring of the growth of unknown defects at a given load, even remotely by data transmission.
  • It monitors a structure under all operating conditions.
77
Q

AE Testing Limitations;

A
  • Defects that do not grow or move cannot be detected
  • The only defects that can be detected without exceeding the highest preceding load are defects that are already active at the actual load level and
    endangering the component
  • Evaluation criteria do not exist in the form of commonly accessible data; the rating of AE results is dependent on the knowledge and experience
    of the service provider.
  • AE testing is sensitive to process noise exceeding the detection threshold. Raising the threshold level decreases test sensitivity. Above a certain noise level, AE testing is no longer efficient.
78
Q

AE Testing Location Errors;

A
  • A different wave mode than the assumed one determines the arrival time.
  • A wave takes a different propagation path than assumed by the algorithm.
    • Multiple waves that overlap at the sensor.
    • Sources emit signals in such quick succession that there is not enough time
    for the signals in the structure to decay. Therefore they do not represent
    a new hit
79
Q

AE transducers are state-of-the-art piezoelectric sensors operating at frequencies from ,,,,, to ,,,,,,

A

20 KHz to 1.5 megahertz (MHz)

80
Q

some AE transducer sensors are capable of reliable operation at temperatures as high as ,,,,, centigrade

A

550°C

81
Q

A ,,,,, airborne sensor is used for remote leak monitoring applications.

A

200kHz

82
Q

,,,,, testing is a powerful method for examining the behavior of materials deforming under stress

A

Acoustic emission (AE)

83
Q

,,,,,,can be defined as a transient static wave generated by the rapid release of energy within a material

A

Acoustic emission (AE)

84
Q

AE sensors are low-noise detectors that operate in the ultrasonic frequency range of ,,, to ,,,,

A

10kHz to 2MHz

85
Q

Through AE Testing, Physical motions as small as ,,,, can be detected

A

1 X 10 minus 12 ( pm)

86
Q

AE sensors can hear the breaking of a ,,,, of metal or a ,,,,,, in a fiber-reinforced composite material

A

single grain

single fiber

87
Q

AE technology provides an ,,,,, system to prevent catastrophic failures

A

early warning

88
Q

AE is also used for a wide range of process applications such as ,,,, and a variety of
,,,, processes

A

leak detection, particle impacts, electrical discharges,

friction-related process

89
Q

ISO and ASTM define acoustic emission as the class of phenomena that generates transient elastic waves by ,,,,

A

rapid release of energy from localized sources

90
Q

The CEN document restricts the acoustic emission term to the transient elastic waves generated by ,,,,,

A

the release of energy or by a process.

91
Q

The ASTM defines the “Felicity effect” as ,,,,,

A

the presence of an acoustic emission at a fixed sensitivity level, at stress levels below those applied previously

92
Q

Three types of compressive elastic waves generated in solids are;

A
  • primary waves, or P-Waves
  • shear waves, secondary waves, or S-waves
  • surface wave, Raleigh wave, or R-wave
93
Q

Impact-echo testing relies mainly on the propagation and reflection of ,,,,

A

P-waves.

94
Q

For normal concrete, P-wave speed varies from about ,,, to ,,,,

A

3000 to 5500m/s.

95
Q

The relationship among wave speed, frequency, and wavelength is given by Eq.

A

C = f x λ (lambda)

where;
C = speed of the stress wave
f = frequency in kHz
λ = wavelength in m

NDT Level-3 ( Pual E. Mix - By Wilay & Sons) (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions