NDT Services from TWI

Optical NDT Techniques and Image processing

Description

Optical interferometric techniques and imaging processing have been widely used in material characterization, defects detection, strain measurement, design verification/optimization, residual stress evaluation, vibration analysis and 3D shape measurement. They provide powerful quantification means to engineering inspectors in their pursue of product design, process optimisation, and integrity assessment for safety critical components and structures. Optical techniques offer a unique combination of high sensitivity, full-field and real time visualisation. Compared to other non-destructive testing techniques, optical techniques reveal defects in an object by assessing the response of surface deformation to defects under stressing, which is closely correlated with the strength and integrity of the object. Not only the modes of defects could be determined, the strains and stresses field associated with these modes could be quantified as well.

Laboratories

The NDT department in TWI Wales has well-equipped laboratories and workshops with highly skilled technical staffs. Equipments for optical interferometric measurements include holography (HI), electronic speckle pattern interferometry (ESPI), moiré interferometry (MI). The equipment in the laboratories can be categorised into the four principal areas:

  • Testing and characterization of materials, including composites, metal alloys, ceramics
  • Thermal mechanical behaviors study and life perditions of microelectronics
  • Residual stress measurement of welding joints
  • Prototype development and experimental qualification

Facilities:

  • 3-D Moiré interferometer with high temperature oven and phase-shifting software)
    3-D Moire interferometer
  • High speed camera with image processing software
  • Optical set-up for holographic interferometry, speckle interferometry, electronic speckle pattern interferometry, digital speckle correlation

Applications

  1. Characterization of thermal mechanical response of Carbon Composite laminates. The shear strain/stress between 7 layers are measured
    Characterization of thermal mechanical response of Carbon Composite laminates
    Characterization of thermal mechanical response of Carbon Composite laminates
  2. Combination of optical interferometry and hole-drilling for residual stress measurement
    Combination of optical interferometry and hole-drilling for residual stress measurement
    Combination of optical interferometry and hole-drilling for residual stress measurement
  3. Optical inspection of PCB and reliability study of BGA package
      Thermal deformation of Pb-free solders joints
    (with 0.6 mm diameter) along a cross-section of a
    BGA package at 100°C
    Thermal deformation of Pb-free solders joints
    Thermal deformation of Pb-free solders joints (with 0.5 mm diameter)
    along a cross-section of a BGA package at 150°C

For more information on the services offered, contact:

NDT Technology Group

TWI Ltd, Granta Park, Great Abington,
Cambridge, CB21 6AL, UK
Tel: +44 (0)1223 899000 Fax: +44 (0)1223 892588

TWI Technology Centre (Wales) Ltd, ECM2,
Hoel Cefn Gwrgan, Margam, Port Talbot, SA13 2EZ, UK
Tel: +44 (0)1639 873100 Fax: +44 (0)1639 864679

E-mail: ndt@twi.co.uk

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