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Looking beneath the surface - Industrial Member Report 746/2002

 

Review of shearography

TWI Industrial Member Report Summary 746/2002

S A Shaw

Background

In the field of non-destructive testing (NDT), there is a constant search for better techniques, which are capable of providing improved information concerning material flaws.

New types of composite and polymer based materials, which are now commonly used (in particular in the aerospace industry), place particular demands on NDT methods to detect discontinuities and flaws such as disbonds and delaminations because the materials themselves have inhomogeneous structures.

Shearography is a relatively new technique that has given very promising results and is now routinely used for the detection of flaws in many industrial applications, such as in the tyre industry, but has yet to be fully exploited in other industrial sectors.

Shearography, also known as 'speckle pattern shearing interferometry' (SPSI), is a full field optical (interferometric) method based on laser optical deformation and strain measurement. Although this technique was first described in literature as early as 1973, it only started being accepted by industry in the early 1990s.

This report seeks to provide a review of the progress made in the use of shearography as an NDT technique and to discuss the relative advantages and disadvantages in different applications. The report will also identify the most appropriate applications of shearography and the capabilities and limitations of the method in detecting and characterising flaws.

Objectives

  • Identify the different applications of shearography.
  • Determine for one or more applications the capabilities and limitations of the method including the ability to detect and characterise flaws.

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