My ASNT UT Level III Pre-exam Study notes. Not proven yet! The exam is due next month.
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1. Study Note 1: Ultrasonic Testing Source: http://www.ndt-
ed.org/EducationResources/CommunityCollege/Ultra
sonics/cc_ut_index.htm
2. Content: Section 1: Introduction 1.1: Basic Principles of
Ultrasonic Testing 1.2: Advantages and Disadvantages 1.3:
Limitations
3. Content: Section 2: Physics of Ultrasound 2.1: Wave
Propagation 2.2: Modes of Sound Wave Propagation 2.3: Properties of
Acoustic Plane Wave 2.4: Wavelength and Defect Detection 2.5: Sound
Propagation in Elastic Materials 2.6: Attenuation of Sound Waves
2.7: Acoustic Impedance 2.8: Reflection and Transmission
Coefficients (Pressure) 2.9: Refraction and Snell's Law 2.10: Mode
Conversion 2.11: Signal-to-Noise Ratio 2.12: Wave Interaction or
Interference 2.13: Inverse Square Rule/ Inverse Rule 2.14:
Resonance 2.15 Measurement of Sound 2.16 Practice Makes
Perfect
4. Content: Section 3: Equipment & Transducers 3.1:
Piezoelectric Transducers 3.2: Characteristics of Piezoelectric
Transducers 3.3: Radiated Fields of Ultrasonic Transducers 3.4:
Transducer Beam Spread 3.5: Transducer Types 3.6: Transducer
Testing I 3.7: Transducer Testing II 3.8: Transducer Modeling 3.9:
Couplants 3.10: Electromagnetic Acoustic Transducers (EMATs)
Continues Next Page
5. 3.11: Pulser-Receivers 3.12: Tone Burst Generators In
Research 3.13: Arbitrary Function Generators 3.14: Electrical
Impedance Matching and Termination 3.15: Data Presentation 3.16:
Error Analysis 3.17: Transducer Quality Factor Q 3.18: Testing
Techniques 3.19: UT Equipment Circuitry 3.20: Further Reading on
Sub-Section 3
6. Content: Section 4: Calibration Methods 4.1: Calibration
Methods 4.2: The Calibrations 4.2.1: Distance Amplitude Correction
(DAC) 4.2.2: Finding the probe index 4.2.3: Checking the probe
angle 4.2.4: Calibration of shear waves for range V1 Block 4.2.5:
Dead Zone 4.2.7: Transfer Correction 4.2.8: Linearity Checks (Time
Base/ Equipment Gain/ Vertical Gain) 4.2.9: TCG-Time Correction
Gain 4.3: Curvature Correction 4.4: Calibration References &
Standards 4.5: Exercises 4.6: Video Time
9. Content: Section 7: Reference Material 7.1: UT Material
Properties 7.2: General References & Resources 7.3: Video Time
Content: Section 8: Ultrasonic Inspection Quizzes 8.1: Ultrasonic
Inspection Quizzes 8.2: Online UT Quizzes
10. Section 1: Introduction
11. 1.1: Basic Principles of Ultrasonic Testing ULTRASONIC
INSPECTION is a nondestructive method in which beams of
high-frequency sound waves are introduced into materials for the
detection of surface and subsurface flaws in the material. The
sound waves travel through the material with some attendant loss of
energy (attenuation) and are reflected at interfaces. The reflected
beam is displayed and then analyzed to define the presence and
location of flaws or discontinuities. The degree of reflection
depends largely on the physical state of the materials forming the
interface and to a lesser extent on the specific physical
properties of the material.
12. For example, sound waves are almost completely reflected at
metal/gas interfaces. Partial reflection occurs at metal/liquid or
metal/solid interfaces, with the specific percentage of reflected
energy depending mainly on the ratios of certain properties of the
material on opposing sides of the interface. Cracks, laminations,
shrinkage cavities, bursts, flakes, pores, disbonds, and other
discontinuities that produce reflective interfaces can be easily
detected. Inclusions and other in-homogeneities can also be
detected by causing partial reflection or scattering of the
ultrasonic waves or by producing some other detectable effect on
the ultrasonic waves.
13. In ultrasonic testing, the reflected wave signal is
transformed into an electrical signal by the transducer and is
displayed on a screen. In the applet below, the reflected signal
strength is displayed versus the time from signal generation to
when a echo was received. Signal travel time can be directly
related to the distance that the signal traveled. From the signal,
information about the reflector location, size, orientation and
other features can sometimes be gained.
15. Basics of Ultrasonic Test- Contact Pulse Echo Method
http://www.cnde.iastate.edu/faa-casr/engineers/Supporting%20Info/Supporting%20Info%20Pages/Ultrasonic%20Pages/Ultra-principles.html
16. Immersion Method- Figure below shows an immersion UT setup
with CRT or computer screen display. IP indicates the initial pulse
while FW and BW indicate the front and back wall of the specimen,
respectively. Water path Time / Distance Amplitude Display /
CRT
17. Basics of Ultrasonic Test- A-Scan
18. 1.2: Source-1: The advantages of ultrasonic testing include
Ultrasonic Inspection is a very useful and versatile NDT method.
Some of the advantages of ultrasonic inspection that are often
cited include: It is sensitive to both surface and subsurface
discontinuities. The depth of penetration for flaw detection or
measurement is superior to other NDT methods. Only single-sided
access is needed when the pulse-echo technique is used. It is
highly accurate in determining reflector position and estimating
size and shape. Minimal part preparation is required. Electronic
equipment provides instantaneous results. Detailed images can be
produced with automated systems. It has other uses, such as
thickness measurement, in addition to flaw detection.
19. Source-2: The advantages of ultrasonic testing include It
can be used to determine mechanical properties and microstructure.
It can be used for imaging and microscopy. It is portable and cost
effective. It can be used with all states of matter except plasma
and vacuum. It is not affected by optical density.
20. Source-3: Advantages and Disadvantages The principal
advantages of ultrasonic inspection as compared to other methods
for nondestructive inspection of metal parts are: Superior
penetrating power, which allows the detection of flaws deep in the
part. Ultrasonic inspection is done routinely to thicknesses of a
few meters on many types of parts and to thicknesses of about 6 m
(20 ft) in the axial inspection of parts such as long steel shafts
or rotor forgings High sensitivity, permitting the detection of
extremely small flaws Greater accuracy than other nondestructive
methods in determining the position of internal flaws, estimating
their size, and characterizing their orientation, shape, and nature
Only one surface needs to be accessible
21. Operation is electronic, which provides almost
instantaneous indications of flaws. This makes the method suitable
for immediate interpretation, automation, rapid scanning, in-line
production monitoring, and process control. With most systems, a
permanent record of inspection results can be made for future
reference Volumetric scanning ability, enabling the inspection of a
volume of metal extending from front surface to back surface of a
part Nonhazardous to operations or to nearby personnel and has no
effect on equipment and materials in the vicinity Portability
Provides an output that can be processed digitally by a computer to
characterize defects and to determine material properties
22. The disadvantages of ultrasonic inspection include the
following: Manual operation requires careful attention by
experienced technicians. Extensive technical knowledge is required
for the development of inspection procedures. Parts that are rough,
irregular in shape, very small or thin, or not homogeneous are
difficult to inspect. Discontinuities that are present in a shallow
layer immediately beneath the surface may not be detectable.
Couplants are needed to provide effective transfer of ultrasonic
wave energy between transducers and parts being inspected.
Reference standards are needed, both for calibrating the equipment
and for characterizing flaws.
23. 1.3: Limitations (Disadvantages) As with all NDT methods,
ultrasonic inspection also has its limitations, which include:
Surface must be accessible to transmit ultrasound. Skill and
training is more extensive than with some other methods. It
normally requires a coupling medium to promote the transfer of
sound energy into the test specimen. Materials that are rough,
irregular in shape, very small, exceptionally thin or not
homogeneous are difficult to inspect. Cast iron and other coarse
grained materials are difficult to inspect due to low sound
transmission and high signal noise. Linear defects oriented
parallel to the sound beam may go undetected. Reference standards
are required for both equipment calibration and the
characterization of flaws.