Section 6: Selected Applications & Techniques

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6.App-1.3 6.App-1.3.1 The Theory More Reading on Time of Flight Diffraction (TOFD) Time of flight diffraction (TOFD) detects flaws using the signals diffracted from the flaw’s extremities. Two angled compression wave probes are used in transmit-receive mode, one each side of the weld. The beam divergence is such that the majority of the thickness is inspected, although, for thicker components, more than one probe separation may be required. When the sound strikes the tip of a crack, this acts as a secondary emitter which scatters sound out in all directions, some in the direction of the receiving probe. A ‘lateral wave’ travelling at the same velocity as the compression waves, travels directly from the transmitter to the receiver. The time difference between the lateral wave and the diffracted signal from the flaw provides a measure of its distance from the scanned surface. If the flaw is large enough in the through wall dimension, it may be possible to resolve the tip diffracted signals from its top and bottom, thereby allowing the through wall height of the flaw to be measured. http://www.iteglobal.com/services/advanced-ndt/time-of-flight-diffraction-tofd/
Due to the low amplitude of the diffracted signals, TOFD is usually carried out using a preamplifier and hardware designed to improve signal-to-noise performance. As the probes are scanned along the weld, the RF A-Scan signals are digitised and displayed in the form of a grey-scale image showing flaws as alternating white and black fringes. Depending on which direction the probes are moved over the component surface, it is possible to construct ‘end-view’; (B-scan TOFD) or ‘side-view’ (D-scan TOFD) cross-sectional slices. TOFD can also utilise Synthetic Aperture focusing or beam modelling software to minimise the effects of beam divergence, thereby providing more accurate location and sizing information.
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Section 6: Selected Applications &
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6.11: Casting 6.12: Inspection of b
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6.1.1 Casting Defects & Discontinui
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Casting Defects & Discontinuities-
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Casting Defects & Discontinuities
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Casting Defects & Discontinuities
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Processing Defects & Discontinuitie
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6.1.3 Welding Defects & Discontinui
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Welding Defects & Discontinuities
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Welding Defects & Discontinuities-
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Service Induced Defects & Discontin
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Figure 4-24 - In a carbon steel sam
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Figure 4-36 - Weld detail used to j
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Figure 4-38 - Failure of DMW joinin
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Figure 4-58 - Cross-sectional view
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Figure 5-2 - Hot Lean Amine Corrosi
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Figure 5-46 - Overhead interstage k
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Figure 5-48 - Metallographic sample
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6.2: Rail Inspection
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The need for a better inspection me
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Transverse Fissure
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One of the methods used to inspect
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Techniques: Examples of axles with
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6.3: Weldments (Welded Joints)
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UT of Weldments (Welded Joints) F s
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Flaw Detection- Depth Determination
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T = Plate Thickness ϴ = Shear wave
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Flaw Detection- Triangulations of r
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To determine the proper scanning ar
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Expert at works
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Typically scanning patterns
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Weld Scanning
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Weld Scanning
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Echo Dynamic- Position of Defects
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Plate Weld Scanning
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Plate Weld Scanning
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Practice Makes Perfect 52. One of t
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6.4: Pipe & Tube
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Pipe & Tube
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Pipe Scanning
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Pipe Scanning 48.59 o max 30 o max
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Pipe Scanning
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Pipe Scanning- thickness/OD ratio W
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Pipe Scanning- Contact Methods
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Q: Calculate the maximum shear wave
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Q35: During immersion testing of pi
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6.5: Echo Dynamic
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6.5.1 Basic echodynamic pattern of
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C.1 Pattern 1 Point-like reflector
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C.2 Pattern 2 Extended (elongated)
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C.3 Pattern 3a Extended (elongated)
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C.3 Pattern 3b Oblique incidence, t
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C.3 Pattern 3b Oblique incidence, t
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C.4 Pattern 4 Multiple reflector re
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Echodynamic- Change of echo height
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Break Time
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Echo Dynamic of Discontinuity- Flaw
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Echo Dynamic of Discontinuity- Impr
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Echo Dynamic of Discontinuity- Refl
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Echo Dynamic of Discontinuity- Tand
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Echo Dynamic of Discontinuity- Tand
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Echo Dynamic- Root Concavity
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Echo Dynamic
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Echo Dynamic
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Echo Dynamic- Broad indication with
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Echo Dynamic
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Echo Dynamic The echo response from
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Echo Dynamic Typical Echo Dynamic P
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Echo Dynamic Typical Echo Dynamic P
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Q183. In immersion testing, irrelev
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Q46. Which best describes a typical
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6.6: Technique Sheets
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Hanger Pin Testing using Shear Wave
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Physical Dimension
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Physical Dimension
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Reporting: Scanning Report - Top of
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Mock-Up
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Mock-Up
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Mock-Up
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Hanger Pin Testing using Shear Wave
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Pitch and Catch Methods- Set-up
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6.7: Material Properties- Elastic M
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6.7.2 The attenuation method The at
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6.7.3 Velocity Measurements Velocit
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Elastic Modulus Measurement - Young
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These basic material properties, wh
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Equipment: The velocity measurement
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Testing Procedure: Equipment Used.
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Velocity & Equations Poisson Ratio
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6.8: High Temperature Ultrasonic Te
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1.0 Background: Although most ultra
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Temperature Limitation: Conventiona
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敦煌大漠美食 -50 度火
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2.0 Methods used for H.Temperature
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For precision thickness gauging app
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(1b) Flaw detection As in high temp
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2.2 High Temperature Couplants Most
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Keyword: Note that normal incidence
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As a general rule, if the outer cas
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2.4 Equipment Functions Freeze Func
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Keyword: ■ ■ Velocity change of
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3.3 Increased Attenuation: Sound at
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3.4 Angular Variation in Wedges: Wi
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Page 329 and 330: TOFD for Weld- TOFD Parallel Scanni
Page 331 and 332: ■ Perpendicular Scanning Scanning
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Page 335 and 336: ■ Benefit of TOFD Parallel Scanni
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Section 6: Selected Applications & Techniques

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