Full Matrix Capture (FMC) / Total Focusing Method (TFM)


HOW TOTAL FOCUSING METHOD WORKS?
 

The Total Focusing Method (TFM) is an ultrasonic array post-processing technique which is used to synthetically focus
at every point of a region of interest.


1st STEP: DATA COLLECTION WITH FULL MATRIX CAPTURE (FMC)

  • > Full Matrix Capture (FMC) is another way of collecting phased array data
  • > This technique doesn’t require any knowledge of the piece to be inspected (nor shape, nor velocities)
  • > Each element is just activated (shot) one by one
  • > All the elements in reception are recorded and thus a Matrix of signal is stored in order to be processed

2sd STEP: RECONSTRUCTION: Total Focusing Method (TFM)

  

Data

The TFM algorithm uses all signals recorded using the FMC data acquisition mode , available on M2M systems.

According to the EN 16018:2011 European standard:

Full Matrix Capture (FMC): FMC 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

Real-time imaging TFM on GEKKO

Imaging of TFM vs. EScan on corrosion mapping

 

MAIN ADVANTAGES OF TFM
 

  • > Optimal focusing and spatial resolution everywhere
  • > Direct imaging of a large area for one probe position
  • > All reachable angles with the array simultaneously
  • > Defect characterisation
  • > Comprehensive imaging of defect
  • > 3D imaging

 COMPARISON WITH ELECTRONIC SCANNING

 

 Electronic scanning_TFM vs Electronic Scan  TFM_TFM vs Electronic Scan

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

 

COMPARISON WITH SECTOR SCANNING

 

Sectorial scanning_TFM vs SectorScan  TFM_TFM vs Electronic Scan

Sectorial scanning

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

TFM

• 64-element aperture
• Focused everywhere
• 64 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