Shearography - New NDT Method
Shearography is a non-destructive measurement method that allows the detection of defects and sub-surface delaminations in composite material. As new NDT method Shearography enables a non-contact inspection and delivers full-field results obtaining 1,4 Million data points per measurement. Therefore Shearography is considered as a very fast complementary method for conventional NDT methods.Shearography Measurement Principle
Shearography technology is laser measurement method and derivate of a conventional electronic interferometric speckle measurement method (ESPI). This adaptation of Shearography enables the use in field under non-vibration isolated conditions enjoying still the high measurement sensitivity that Laser-Shearography provides to the end-user of 30nm out-of-plane (z-direction).Measurement procedure:
The Shearography sensor illuminates the surface with speckled laser light emitted from the laser diodes. The reflection of the laser light carries the surface information to the observing CCD camera. Shearography always needs a reference image and a loading image of a component for measurement results. Exposed to load (thermal heat pulse, vacuum, etc.) the inspected material shows a local deformation (loading image). From the loading image the reference is subtracted. The local defect shows a different behavior exposed to load than its surrounding “healthy” area.
Since Shearography is a differential measurement method with sheared object beams, which ensures system stability for use in field. Not the deformation of the defect is detected but the gradient of the deformation. Therefore typical Shearography defects images show the “butterfly” defect that is seen in the animation below.
Airbus NDT-Inspection Team uses Steinbichler ISISmobile 3000 Shearography System
Successful cooperation between Airbus and Steinbichler Optotechnik in applying the shearography method for the non-destructive testing of composite materialsSince 2003, Airbus uses a Steinbichler shearography system on various Airbus sites in Germany and France. The NDT inspection team has a ISISmobile 3000 in operation which covers a measurement area of nearly DIN A3 paper size and has proven a reliable tool for Airbus quality assurance. Due to the system´s high resolution (provided by the shearography method - 30 nm out-of-plane), possible defects can be found throughout various material combinations and defect depths.