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Time of Flight Diffraction (ToFD) - Pre-course eLearning Package
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Time of Flight Diffraction (ToFD) Course

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Time of Flight Diffraction (ToFD) -
Pre-course eLearning Package

If you enrol on a classroom-based course in ultrasonic testing with TWI, you can now ensure you are fully prepared using our pre-course eLearning packages. These entirely optional add-ons allow you to familiarise with all of the key concepts that will be covered in the classroom, giving yourself the best possible chance of learning everything you need to achieve certification.

This option is only available to students enrolling on full courses. The  eLearning material is made available 30 days before the course start date, giving you plenty of time to build your confidence before you enter the classroom.

 The eLearning part of this training course is divided in four modules:

  •  Module 1: Basic Principles of Ultrasound and Ultrasound Testing

  •  Module 2: Principles Underlying Time of Flight Diffraction

  •  Module 3: Data Analysis

  •  Module 4: Review

Each module contains:

  • Pages explaining the underlying theory

  • Videos explaining the theoretical and practical aspects of Time of Flight Diffraction (ToFD),
    Silverlight interactive exercises in which the student can build a set-up, practice calibration and scanning and learn to evaluate real data        

Prices depend where you will be attending the course - find out more

When you have booked your training, you will receive an email notification with your login details. You will then have 30 days before the course start date to go through the modules. 

Module 1: Basic Principles of Ultrasound and Ultrasound Testing
  • Non-Destructive Testing (NDT)

  • Sound versus ultrasound

  • Distance, velocity, cycle, material density

  • Sine wave, frequency, wavelength

  • dB system

  • The shell of an ultrasound instrument, ToFD probes, ToFD wedges

  • Pulser/receiver, square pulse

  • Wave propagation, scattering, absorption, energy spreading

  • Beam, sound field, beam diameter

  • Through transmission, pulse echo, angle beam, immersion, PAUT

  •  A-Scan

  • Structure and qualification of a procedure, training, acceptance criteria

  • Calibration blocks, couplant

  • Marking on part, probe positioning

  • Naming files, storing data

  • Section's test

Module 2: Principles underlying ToFD

  • Butt welds

  • Digital instrument, pulser/receiver, digitizer, filters, gain

  • Probes, frequency spectrum, signal waveform

  • Wedges, hard wedges

  • Scanner, encoder

  • Huygens’ principle, diffraction

  • Snell’s law, incident vs. refracted, critical angles

  • ToFD A-Scan, phase shift, phase difference, averaging

  • PCS, transit time, depth calculation, height calculation, position uncertainty

  • Beam spread, beam spread in-wedge, beam spread in-part, frequency spectrum

  • Lateral wave, backwall, mode-converted backwall

  • Dead zones, accuracy, resolution

  • B-Scan, gray scale

  • Whisker effect, parabolic cursors 

  • Non-parallel and parallel scans    

  • Multiple scans

  • Influence of frequency on coverage, dead zones

  • Influence of wedge angle on time scale, coverage

  • Influence of PCS on dead zones, resolution, coverage

  • How to optimize the digitizing frequency, filters, averaging, time window, sensitivity, PRF

  • Calibration of the beam index point, velocity

  • Scanning speed

  • Wedge delay calibration, lateral wave straightening, lateral wave removal

  • Interactive exercises on set-ups, beam index point and velocity calibration, scanning

  • Interactive exercises on wedge delay calibration and lateral wave straightening

  • Section’s test

    Module 3: Data Analysis

  • B-Scan perspective

  • Lateral wave, backwall and mode-converted backwall signals

  • Effect of beam spread on depth and the backwall signal

  • Indication classification, probe position vs. height, angle vs. height

  • Geometrical indications, double-V welds, pipes misalignment, different wall thickness

  • Data quality, calibration, basic analysis, detailed analysis

  • Signal start, grouping, point-like indications

  • Height and depth, top-surface breaking, bottom-surface breaking, embedded

  • Length and position, parabolic shape, elongated and curved

  • Interactive viewer, top-surface breaking, bottom-surface breaking, embedded

  • Interactive exercises on set-up, beam index calibration, scanning, data analysis

  • Section’s test  

    Module 4: Review

  • Hardware

  • Scans and views

  • Theory

  • Set-ups

  • Calibration

  • Data analysis

  • The defects

So that your computer can run the Phased Array eLearning modules you will need the following basic systems:

Operating System
Windows Vista 7, 8 or 10

Internet Explorer 11 or higher (PC)

Silverlight Plug-in

You can get the Silverlight Plug-in using the following link:

Internet connection:
2 MBIT/s


To get an idea of what you can expect when you begin the course, and view some helpful tutorial videos , click the link below:

View the course taster

Please use the latest version of the browser Internet Explorer with Silverlight installed to view the tasters. Videos are best seen in full screen mode, exercises must be in full screen mode to work.