Time of Flight Diffraction (TOFD)


TOFD course is suitable for personnel, who having with ultrasonic testing experience, who are looking to expand their knowledge into advanced ultrasonic applications and gain a qualification in Time of Flight Diffraction (TOFD). Consider our  study theory & practical work in hand with various flaw specimens & gain your knowledge as well as conception of the nature of discontinuities.

TOFD theory is  based on diffraction, hardware provided used pulsers, receivers separately, encoders used for measured scan distance, data acquisition and interpretation. You will also learn about equipment used & selection of frequency, PCS and angles, flaw location and sizing, limitations of detection and resolution, codes and standards, and reporting.
Basic difference Level-2 & Level-3 is as below:
Level-3 course have more calculation & how to use Specifications, Codes & Standards.

1. Chapter  – TOFD Introduction & History
2. Chapter  – TOFD Vs Other methods
                    TOFD Signals Signals received
                         • Lateral wave (LW), subsurface
                         • Back-wall echo(BW)
                         • Mode converted ( shear wave echo)
                         • Diffracted signals from defects

3. Chapter   – Physics – Tip Diffraction
Diffraction Mechanism, Effects of Diffraction, Ultrasonic diffraction
4. Chapter  – Fundamentals of TOFD
Basic Setup, TOFD Signals, The Lateral wave, Back wall Signal, Diffracted wave -
                         Defect signals, 
                         Mode converted shear signals, Phase - Relationship between waves, ToFD Data
                         (A-Scan to B-Scan), TOFD Dead Zones, ToFD Probe angle, Transducer size, Probe
                         frequency TYPICAL TOFD SETUP, Time of Arrival calculation

5. Chapter  – Equipment Setup & Parameters Selection
Probe, Beam spread, Difference in beam spread with respect to frequency, Probe
                       frequency, Probe angle, 
                       Recommended Probe selection parameters for thickness up to 70mm, Probe-
                       Centre Separation (PCS),
                       Probe-Centre Separation
      Settings Gain setting, Time window settings, Time-to-depth conversion (Screen Calibration), 
      Sensitivity settings, Calibration,
      Scanning : Longitudinal scan - Non-Parallel or D-scan or line scan, Limitations
                         Parallel scan - Lateral, transverse or B-scan, Limitation
                         Mechanical Scanner
                         Scan Resolution (Sampling Interval), Parameters for a ToFD Scan

                         Parameters to be considered in TOFD
                         Transducer size & Probe frequency

6. Chapter    - Errors in TOFD
Errors in the timing
                         Near Surface errors
                         Dead zone errors
                         Resolutions of top and bottom tips
                         Off-Axis depth error
                          PCS errors Multiple arcs
                          Other errors

7. Chapter    – Digitization Principles
Key Parameters of digitizer
                         • Frequency (Digitizer)
                         • Processor (no. of bits or amount of information that can be handled)
                         • Averaging
                         • PRF
                         • Acquisition Rate
                         • Soft Gain

8. Chapter   – Data Analysis & Sizing
Interpretation and analysis of TOFD images
                         Assessing the quality of the TOFD image
                         Identification of relevant indications
                         Classification of relevant indications
                         Surface breaking discontinuities
                         Embedded discontinuity indications 
                         Gain Settings, Missed Scan, Loss of Signa, Effect of thick couplant layer, 
                         Screen Calibration , Lateral wave synchronization, Sizing Techniques,
                         Height measurements, Synthetic Aperture Focusing Technique (SAFT) ,
                         TOFD image of surface notch's, 
TOFD image of opposite surface discontinuity,
                         TOFD image of opposite surface discontinuity with a larger depth,
                         TOFD image of a through wall discontinuity, TOFD image of point like
                          TOFD image of a change in thickness

9. Chapter   – Codes & Standards - TOFD
Many national and International standards or European Standards are available :-
                         EN, ASME, ASTM, AWS, ISO, etc.

10.Chapter  –  Applications of TOFD