Full Matrix Capture (FMC) Total Focusing Method or Total ...

According to the EN 16018:2011 European standard:

Full Matrix Capture (FMC): full matrix capture specific data-acquisition process using ultrasonic array probes where each element in an array is successively used as the transmitter, while all elements are used as receivers for each transmitted pulse

Total Focusing Method or Total Electronic Focusing (TFM): electronic focusing which consists of adapting the receiving delay laws to focus at many points which form a grid, after a single pulse which generates a large and/or divergent ultrasonic beam

𝑠𝑛1 𝑡 … 𝑠𝑁1 𝑡…

N emitters

N r

ecei

vers

Px

𝐸1

➢ Element n°1 fires


N emitters

N r

ecei

vers

Px


𝑅1 𝑅2 𝑅3 𝑅𝑁

➢ All the elements receives


N emitters

N r

ecei

vers

Px


➢ All the elements receives

𝐸2



N emitters

N r

ecei

vers

Px


➢ All the elements receive





N emitters

N r

ecei

vers

Px





𝐸3



N emitters

N r

ecei

vers

Px










N emitters

N r

ecei

vers

Px








𝐸N

➢ Last element fires


N emitters

N r

ecei

vers

Px








➢ Last element fires




1. Define a region of interest in the component

2. Time-of-flight calculation tij(P) for all couple (Ei, Rj)

Px

𝐸i 𝑅j

3. Amplitude extraction from each signal at time tij(P)

4. Sum of the N x N amplitudes

5. Perform the steps above for all pixels

N emitters

N r

ecei

vers

𝑡𝑖𝑗 = 𝑡𝐸𝑖𝑃 + 𝑡𝑃𝑅𝑗

Aij

Px

Electronic scanning• 8-element aperture• Focused along the defects in the middle• 57 shots

TFM• 64-element aperture• Focused everywhere• 64 shots

• Lateral resolution limited by the pitch; in this case 1 mm

• Focusing capability limited by the selected aperture

• Directive beam (along direction of propagation)

• Area of inspection limited to (N – A) * pitch

• Step size determined by the system (Gekko = 65536 pixels); in this case 0.15 mm

• Complete aperture for focusing

• Omni-directional beam

• Area of inspection > N * pitch

Sectorial scanning• 64-element aperture• Focused along the defects in the middle• Sectorial between -55° and 55° with 110 shots

• Optimal resolution at the point of focalisation

• Directive beam (along direction of propagation)

• Energy from N elements sent into the part

• Optimal resolution everywhere

• Omni-directional beam

• Only one element fired at a time

TFM• 64-element aperture• Focused everywhere• 64 shots

Hydrogen Induced Cracking (HIC) is caused by the blistering of a metal due to a high concentration of hydrogen. The blistering damage tends to form parallel to the surface

Once the ductility of the metal has reduced to a significant amount, the metal will form stepwise internal cracks connecting adjacent hydrogen blisters.

While the initial stage of HIC is not critical (individual cracking), it can become dangerous should HIC give rise to step-wise cracking that propagates into a weld or begins to go step-wise through the wall

The idea is thus to detect potential connexion between the various cracks before catastrophic failure

We compare standard electronic scanning to TFM

Escan FMC

By nature, the TFM from a FMC leads to a large beam spread so energy sent into directions capable of detecting the connexion between the crack

connexion

connexion

connexion

backwall backwall

HICHIC HIC

High temperature hydrogen attack is a form of damage commonly observed in steels exposed to highpressure hydrogen at elevated temperatures.

The damage occurs as hydrogen atoms diffuse into steels, react with carbon, form methane gasinternally in the material, which results in decarburization and fissuring (micro-cracking).

As the defects are quite small (micro) it is quite difficult to detect them with conventional UT method;an analysis of the backscattered energy is usually performed

TFM has been recently introduced by Oil & Gas companies and training centers as a mean to detectHTHA damage

To develop an new method the big difficulty is to have access to HTHA samples

Special test specimens were realized in similar conditions than the ones encountered on the field. They were thensectioned to expose HTHA cracks near the backwall

The specimen were metallographically ground and polished according to ASTM E3-01. Small cracks are visiblearound the grains

Equipment:

• We use our portable phased-array unit with embedded TFM: Gekko

• Manufactured specimen, 50-mm thick carbon steel

• Depending on the thickness we use 64-element linear arrays with frequencies ranging from 5 to 10 MHz

• We use off-the-shelf 2D scanners to scan the mockup

• For analysis, we do it onboard with the Gekko software, Capture, or off-line with our analysis software:Enlight

TFM area

PA probe

trajectory

The TFM area is positioned at the bottom of themockup to detect early stage HTHA

We use a 64L3-G2 probe

A 2D scan is performed over the mockup with a 1-mmstep along the scan axis and

Cumulated Tscan

Cumulated Tscan

Dscan

Dscan

Cscan

Cscan

backwall

In the Tscan, we can see smallindications initiating from thebackwall propagating 3 mm fromthe backwall

backwall

HTHA

In the Dscan, we can see that theHTHA indications propagate alongthe full length of the mockup

HTHA

The Cscan shows the cartography ofHTHA damage in the component

HTHA

The TFM allows full characterization(length, height) of the HTHAdamage inside the specimen

The sample is 100 mm thick

We use a 64L5-G3 probe

The TFM area encompasses the entire thickness. Thepixel size respect the ʎ/5 rule to avoid losing amplitudedata

We can detect HTHA going all the way up to 60 mm

For thicker materials the TFM can use in conjunctionwith lower frequency probe

HTHA

HTHA

Lavender is teaching HTHA detection and sizing courseusing TFM among several techniques

This course is founded on extensive work andexperience gained during industrial trials as part ofthe E2G HTHA JIP

Many data have been acquired using the TFMtechniques finding HTHA damage in the base material,the HAZ and weld

HTHA

Courtesy of Lavender

Samples with serious HTHA damage can leadto extended cracking

HTHA

Courtesy of Lavender

Lavender booth C04-41

Courtesy of BP

© BP Products North America© BP Products North America

© BP Products North America

TFM is being used by BP and its service providers to detect stage 1 HTHA

PAUT TFM and ATFM resolution is in the range of 0.3 mm (300 μm), a significant improvement over the techniques recommended in API RP 941.

TFM has been successfully introduced by Oil & Gas companies, services providers and training centersfor the detection of hydrogen damages

TFM offers high-resolution images that allow the detection and characterization of both HIC and HTHAdamages

The availability of portable equipment capable to perform real-time TFM offers a new tool to the NDToperator arsenal

Welcome to visit our booths D06-10 & C05-42

Full Matrix Capture (FMC) Total Focusing Method or Total ...

Documents

Transcript of Full Matrix Capture (FMC) Total Focusing Method or Total ...