NDT Acoustic Emission Testing 3

Question 1

Acoustic emission testing is particularly well-suited for in-service inspection of pressure vessels because:

Accepted Answer

It monitors the entire structure simultaneously while the vessel is under load

Answer

It can detect flaws regardless of orientation without removing insulation

Answer

It does not require any couplant or surface preparation

Answer

It can identify the chemical composition of any corrosion products present

Question 2

The Felicity Effect occurs when:

Accepted Answer

AE reappears during reloading at a stress level below the previous maximum, indicating damage

Answer

AE signals are recorded only above a fixed frequency of 100 kHz

Answer

Sensors exhibit a nonlinear frequency response at high signal amplitudes

Answer

Background noise masks true AE signals during high-pressure testing

Question 3

ASTM E650 provides guidelines for:

Accepted Answer

Mounting and use of piezoelectric acoustic emission sensors

Answer

Radiographic film interpretation for weld discontinuities

Answer

Calibration of ultrasonic reference blocks

Answer

Magnetic particle testing of ferromagnetic castings

Question 4

Which characteristic makes acoustic emission testing especially valuable for monitoring fiber-reinforced composite structures?

Accepted Answer

It can differentiate damage mechanisms such as matrix cracking, fiber breakage, and delamination by signal frequency and amplitude

Answer

AE can detect only surface cracks, which are most critical in composites

Answer

Composites do not attenuate AE signals, allowing single-sensor whole-structure coverage

Answer

AE testing does not require surface preparation on composite laminates

Question 5

To minimize interference from mechanical background noise during an AE test on operating equipment, a technician should:

Accepted Answer

Increase the detection threshold and use frequency filtering to eliminate noise frequencies

Answer

Switch from piezoelectric sensors to magnetostrictive sensors

Answer

Reduce the preamplifier gain to prevent sensor saturation

Answer

Perform the test only when ambient temperature exceeds 50°C

Question 6

Compared to ultrasonic testing, acoustic emission testing is considered a 'passive' technique because:

Accepted Answer

It detects stress waves emitted by the material itself rather than introducing external energy

Answer

It requires no electrical power supply during data acquisition

Answer

Sensors are permanently bonded and cannot be repositioned after initial placement

Answer

The method produces no permanent record of the inspection results

Question 7

Zonal location in acoustic emission testing determines the source position by:

Accepted Answer

Identifying the sensor that receives the signal first and assigning the source to that sensor's zone

Answer

Calculating exact time-of-arrival differences between all sensors to triangulate a precise coordinate

Answer

Measuring the peak frequency of each hit to map it to a frequency-location lookup table

Answer

Using the signal amplitude decay curve to back-calculate distance from each sensor