FMC/TFM

Choosing the right probe and propagation path

Olympus Canada - Chi-Hang Kwan

Namicon – Octav Teodorescu

Olympus Europa - Florin Turcu

01 Introduction

02 Total Focusing Method

03 Choice of probe and propagation modes

04 Solution: A.R.O.I.

05 Experimental validation

06 Conclusions

07 References

01 Introduction

TFM/FMC

Page 4

FMC – Full Matrix Capture and TFM – Total Focusing Method

Ultrasound Imaging Technique with a high potential for

▪ Improved sensitivity

▪ Wider field of view

▪ True-to-geometry view

▪ Potentially improved probability of detection (POD)

Phased Array – has its roots in single-element conventional ultrasound;

TFM – can be seen as next step in industrial Ultrasound imaging following PA

• Complexity – requires guidance and standards of practice to consider:

• Choice of probe/wedge combination

• Selection of mode and propagation path

02 Total Focusing Method

TFM/FMC – the basics

Page 6

FMC – Full Matrix Capture and TFM – Total Focusing Method

– Total Focusing Method (TFM) is an advanced data processing algorithm.

▪ AQUISITION

– Data is usually acquired using the FMC (Full Matrix Capture) method.

▪ FOCUSING

– When applied to ultrasound data acquired with a multi-channel instrument, it allows focusing the acoustic energy in all

points of a given region of interest.

▪ IMAGE:

– The result is a high resolution image of the zone of interest

FMC/TFM – How it works

It all starts withConventional UT

UT

Acoustics

Near field/ far field zones

Beam spread

Mode conversion – Snell/Descartes Law

ALL is still valid and MUST be taken into account

when using/performing TFM

Going ThroughBasic Phased-Array

PAUT

Page 10

S

Signals coming from the reflector

arrives at first on the closest element

Signals coming from the reflector

finally arrives on the furthest elements

Appropriate delays

are electronically

introduced during

reception

Only signals “satisfying” delay law shall

be “in phase” and generate significant

signal after summation

How Phased-array work ?▪ DELAYS: Appropriate delays are introduced electronically during emission and reception

▪ SUMMATION: Only signals “satisfying” delay law shall be “in phase” and generate significant signal after summation

And nowFMC – Full Matrix Capture1st step

FMC = Full Matrix Capture

Pulse on 1st element, receive on all

Pulse on 2nd element, receive on all

Pulse on 3rd element, receive on all

….

A complete « MATRIX » is built

generating a huge amount of data.

FMC Probe elements

. . .

Acquisition matrix.

Each matrix element stores one A-scan

Repeat 1 million times

Result: 1 million matrices 32x32 A-scans

TFM = Total Focusing Method2nd step

TFM Techniques

TFM = Total Focusing Method = data processing

An image is processed

Each pixel is treated as a focal point

The algorithm used to image this data is generated

through a standard sum and beam-forming approach

Other algorithms possible

S

S

Transmitter 1

S

Transmitter 2

Transmitter 32

FMC

TFMLine 1

Line 2

Line 32

Zone of

interest

A-scans saved in each line

of the FMC matrix

Delays applied for

synthetic focusing in

reception phase

Delays applied for

synthetic focusing in

transmission phase

summation summation

Resulted focused data in

one image point

Page 16

To obtain an image

03 Modes of Propagation

The operator needs to indicate the chosen Mode and Path depending on application

Direct Paths 4 possibilities

TT, LL, TL, LT

Modes of Propagation

Where:

T → Transverse / Shear Wave

L → Longitudinal / Pressure WaveLL TT

TTTTLL

LL

TT LL

TL LT

Indirect Paths (or pitch-catch / or half-skips) 8 possibilities

LLL, LLT, LTL, LTT,

TLL, TLT, TTL, TTT

Modes of Propagation

L

L

L

L

L

T

T

T

TT

T

T

Remember Snell (Descartes) law:

– the higher the velocity, the larger the reflection / refraction angle

Mode Conversions

𝑆𝑖𝑛 ∅𝑖𝐿

𝑐𝐿1=𝑆𝑖𝑛 ∅𝑅𝐿

𝑐𝐿1=

𝑆𝑖𝑛 ∅𝑅𝑇

𝑐𝑇1=𝑆𝑖𝑛 ∅𝑟𝐿

𝑐𝐿2=𝑆𝑖𝑛 ∅𝑟𝑇

𝑐𝑇2

Mode Conversions

T

LL

T

T

L

▪How do we use it?

Remember Snell (Descartes) law:

– the higher the velocity, the larger the reflection / refraction angle

Mode Converted Paths (or Full-Skips) 16 possibilities

LLLL, LLLT, LLTL, LLTT,

TTLL, TTLT, TTTL, TTTT , etc…

Modes of Propagation - complexity

Note: Not all modes are useful in

practice for common applications.

Most Common Modes

1. Direct: TT, LL

2. Half-Skip: LLL, TTT, LTT, TLT, TLL

3. Full-Skip: TTTT, LLLL

1

2

3

Modes - example

TT mode

Modes - example

TTT mode

04 Solution: A.R.O.I

Page 27

Addressing complexity AROI

▪ Olympus developed and patented a unique TFM scan plan method

▪ AROI – Acoustic Region of Influence

TTT

Page 28

Addressing complexity AROI

▪ Analytical – simulation method of acoustic field

▪ Implements basic acoustic formulas: reflection, refraction, beam spread, near field etc

▪ Does not require computing power

TTT

Page 29

Addressing complexity AROI

▪ Image depends on:

– Probe and wedge

– Wave mode

– Sound Path

– Reflector type: volumetric or planar/ flat

– Reflector orientation (if planar)

TTT

05 Experimental validation: choice of

probe, mode and path

Page 31

Resolution block▪ Different aperture

▪ Different pitch

▪ Different frequency

Low frequency/ small pitch HIGH frequency/ small pitch Low frequency/ large pitch and

aperture

Good resolution and sensitivity near surface Good resolution and sensitivity middle zone Good resolution and sensitivity middle and distant zone

Page 32

5L64-A32 – pitch 0.5, aperture 32mm 5L64-NW1 – pitch 1, aperture 64mm

a) b) c)

d)e)

Corrosion - Pitting

▪ Different aperture

▪ Different pitch

Small pitch and aperture Larger pitch / wider aperture

Better directionality / small coverageWorse directionality / larger coverage

Page 33

T

T

T

T

L

T

T

L

a)b)

Weld - CrackSub-surface Back-wall

▪ Different modes

▪ Different path

Page 34

TT TT – 10MHz

TT TT – 5MHz

Weld – lack of fusion▪ Different frequency

06 Conclusions

Conclusions

Page 36

▪TFM – new technique with a lot of potential in corrosion and weld applications

▪High complexity, but high potential for being miss-used

▪AROI – Acoustic Region of Influence

– Can help the operator chose the right parameters vs application

– An excellent tool for learning

– Light algorithm – no Finite Element Simulation

07 References

References

Page 38

▪ [1] C. Holmes, B. W. Drinkwater, and P. D. Wilcox, “Post-processing of the full matrix of ultrasonic transmit–receive array

data for non-destructive evaluation,” NDT E Int., vol. 38, no. 8, pp. 701–711, Dec. 2005.

▪ [2] K. Sy, P. Bredif, E. Iakovleva, O. Roy, and D. Lesselier, “Development of methods for the analysis of multi-mode TFM

images,” J. Phys. Conf. Ser., vol. 1017, p. 012005, May 2018.

▪ [3] Chi-Hang Kwan, Guillaume Painchaud-April, Benoit Lepage, TFM Acoustic Region of Influence, ASNT Spring Research

Symposium

▪ [4] Olympus, Phased Array Probe catalogue

Test Overview

Test Block EP1000-PABLOCK-1 Phased Array

Aluminium Demo Block with 5L64A32 and

SA32-N55S-IHC

Page 39

Results

Page 40

LLL TTT

LTTTT

Results

Page 41

LLL TTT

LTTTT

Results

Page 42

LLL TTT

LTTTT

Results

Page 43

LLL TTT

LTTTT

Results

Page 44

LLL TTT

LTTTT

Results

Page 45

LLL TTT

LTTTT

Results

Page 46

LLL TTT

LTTTT

Results

Page 47

LLL TTT

LTTTT

MX2 & SX Updated 2019 MXU 4.4R4 !

Page 48

MX2:

▪ Multi-Group inspection

▪ Modularity for changing needs

SX:

Single group inspection

Small

Simple

Still an OmniScan

MX1New electronics updated in 2018 to be CE certified & ROHS compliant

ECA & ECT Modules

BondTesting C-scan

Page 49

ADVANCED ULTRASONIC TECHNIQUES TRAINING & WORKSHOP

Page 50

- Phased Array

- TOFD

- TFM / FMC

- Basic & Physics

- Scan Plan & Acquisition & Analysis

- Applications

- Hands-on & Practice

- Q & A

- Conclusions

METHODS:

CONTENT:

WORKSHOP:

Grand Hotel Phoenicia – Bucharest September 2019