Effective development of advanced materials and components requires an understanding of their behaviour under load at various conditions. Optical full-field measurement techniques are increasingly being used in material testing, fracture mechanics, and vibration analysis.
Electronic Speckle Pattern Interferometry (ESPI) is a full field non-contact experimental measuring technique that allows rapid and highly accurate measurement of the three components of deformation and generation of strain/stress distribution with high resolution. It is well suited for the determination of the true peak strain and the strain distribution in regions of strain concentration that are usually the most critical in an investigation. ESPI measurement results are also used for FEA validation of complex, anisotropic materials.
ESPI can be considered as an electronic version of holographic interferometry that uses a CCD camera instead of a photographic film to acquire and store the fringe images, while a computer is used to process the images – for details see Measurement Principles of ESPI.
The ESPI technique is successfully applied to a wide range of applications in complex industrial components like car bodies, gear-boxes, engines and research studies, e.g. biomechanical investigations.