introduction to advanced ultrasonics
TRANSCRIPT
-
7/28/2019 Introduction to Advanced Ultrasonics
1/24
Phased Array and Time-of-Flight
Diffraction (TOFD)
Introduction to Advanced
Ultrasonic Phased Array
-
7/28/2019 Introduction to Advanced Ultrasonics
2/24
a linear array (1D) is
basically a long
conventional probe
cut in many small
elements, that can be
individually excited
Design Parameters of Phased-
Array Probes
-
7/28/2019 Introduction to Advanced Ultrasonics
3/24
Phased-Array probes
Time
Single Trigger
Pulse
Wave front
-
7/28/2019 Introduction to Advanced Ultrasonics
4/24
Conventional Waveforming
Beam steering using conventional UT probe (Transmit): angled wedge introduces appropriate delays during emission
to generate angle beam
CrystalWedge
Material
Excitationpulse
Wave front
Delay
Location
A B C
A B C
-
7/28/2019 Introduction to Advanced Ultrasonics
5/24
Conventional Waveforming
Beam steering using conventional UT probe (RECEIVE) : angled wedge introduces delays during reception, so that
only waves in phase.
CrystalWedge
Material
Received signal
Delay
Location
A B C
A B C
S
-
7/28/2019 Introduction to Advanced Ultrasonics
6/24
Phased-Array Waveforming
Beam steering using phased-array probe : appropriate delays introduced electronically during emission
to generate angle beam
Wave front
Time
Delay
Element
Focallaw
-
7/28/2019 Introduction to Advanced Ultrasonics
7/24
Beam Focusing
Is the capabi l ity tocon verge the
acoust ic energyintoa small focal spot
Allows forfocus ingat several depths,using a single probe
-
7/28/2019 Introduction to Advanced Ultrasonics
8/24
Beam Steering
-
7/28/2019 Introduction to Advanced Ultrasonics
9/24
Beam Steering
Is the capabi l ity tomod ify the refracted
angleof the beamgenerated by thearray probe.
Allows formult ip leang le inspect ions,using a single probe
-
7/28/2019 Introduction to Advanced Ultrasonics
10/24
Combined Beam Processing
Linear combined with steering and focusing
-
7/28/2019 Introduction to Advanced Ultrasonics
11/24
-
7/28/2019 Introduction to Advanced Ultrasonics
12/24
Tandem for Vertical Defects
-
7/28/2019 Introduction to Advanced Ultrasonics
13/24
TOFD
For Weld Inspection
Description of TOFD technique (Theory)
-
7/28/2019 Introduction to Advanced Ultrasonics
14/24
FLAW
Diffracted
waves
Diffracted
waves
Incident
wave
Reflected
wave
All directions
Low energy
Independent of
incidence angle
The Diffraction Phenomenon
-
7/28/2019 Introduction to Advanced Ultrasonics
15/24
2 probes (transmitter, receiver)
Wide beam, longitudinal waves
Symmetric to the weld center
Diffraction signal detection (high
receiver sensitivity)
Basic Setup
-
7/28/2019 Introduction to Advanced Ultrasonics
16/24
Signals received
Lateral wave, subsurface
Back-wall echo
Mode converted (shear wave) echo
Define top and bottom of part
Note phase change
TOFD Signals
-
7/28/2019 Introduction to Advanced Ultrasonics
17/24
Transmitter Receiver
Lateral wave
Upper tip
Lower tip
Back-wall reflection
TOFD Signals
-
7/28/2019 Introduction to Advanced Ultrasonics
18/24
Data Visualization (TOFD)
Lateral
waveBack-wall
A-scan
Indication
-
7/28/2019 Introduction to Advanced Ultrasonics
19/24
Near Surface Crack
The crack blocks the Lateral Wave
And the lower tip appears on the A-scan
21
1
2
-
7/28/2019 Introduction to Advanced Ultrasonics
20/24
Lack of Fusion, Interpass
1
2
3
-
7/28/2019 Introduction to Advanced Ultrasonics
21/24
Lack of Root Penetration
Note the inverted phase between LW and defect
1
2
3
1
23
-
7/28/2019 Introduction to Advanced Ultrasonics
22/24
Diffracted rather than reflected signals
Longitudinal waves
B-scan type imaging (side view) Accurate sizing capability (height)
Interpretation of defects
Less sensitive to defect orientation
TOFD - Advantages
-
7/28/2019 Introduction to Advanced Ultrasonics
23/24
Blind area - near surface, backwall ID and OD Geometry (Hi-Lo)
Weak signals
Couplant loss
Flaw classification limitation
Interpretation of defects
Sensitive to grain noise and Coarse
grained materials
TOFD - Limitations
-
7/28/2019 Introduction to Advanced Ultrasonics
24/24
Typical manual TOFD scanner