Published on 03-Feb-2024

Shearography in Non-destructive Testing: A Comprehensive Review

Shearography in Non-destructive Testing: A Comprehensive Review

Sources - Wikipedia

Table of Content


Introduction

Shearography is an advanced optical technology used to detect tiny deformations and defects on the surface of objects.

It is based on the principle of interference and detects possible structural defects by observing the slight displacement of objects under loading stress or environmental changes.

Leendertz and Butters first proposed this technology and began to attract attention in the early 1980s.

However, real breakthroughs and applications occurred in subsequent decades, especially in the late 1990s and early 2000s, as optical and computational technology advances made shear interferometry more reliable and precise.

Schematic of a Shearography Test

In the operation of shear interferometry, the surface of the object to be inspected is first coated with a layer of photosensitive material, and then a laser beam is used to illuminate the surface. 

This laser beam produces an interference pattern after reflection.

When an object is stressed or deformed, small displacements of the surface cause a change in the interference pattern. By recording these changes, defective areas can be identified.

Compared with the traditional NDT Method, the shear interferometry method has the advantages of non-contact, rapidity, and high sensitivity, and can accurately detect cracks, wrinkles, or other structural problems without damaging the object's surface.

In modern-day NDT, shear interferometry is widely used in high-end industries such as aerospace and automobile manufacturing to detect various defects in complex structures. Its high sensitivity and accuracy make it a viable NDT method. 

Shearography and its Principles

Shearography, an advanced Non-destructive Testing (NDT) method, is a technique that detects defects in materials without causing damage.

It's widely employed by NDT Technicians to assess the integrity of various structures and components.

A Shearography Tyre testing machine

1. Mechanical Principles of Shearography

* Shear Sensitivity:

Shearography is sensitive to minute changes in material surfaces caused by stress or deformation.

NDT technicians utilize this sensitivity to identify defects like cracks, delaminations, or material inconsistencies.

* Interferometry:

Employing interferometry, Shearography compares the interference patterns between stressed and unstressed areas to pinpoint variations caused by defects.

This helps in Non-destructively evaluating the material's structural integrity.