Optical Strain Measurement on Small Specimens Based on Laser Speckles
Progresses in developments of high resolution digital cameras and processors power as well enable the use of optical systems for axial and biaxial strain measurements. The main benefit of these systems is a contact free measurement on the sample surface without any influence to the sample. The commonly used optical systems based on following markings attached to sample surface which have to be applied before testing. This paper presents an alternative optical measuring system using the speckle-correlation-technique. The laser based method does not need any special sample markings before testing. The speckle correlation in the presented extensometer measures up to two-dimensional surface strains in tensile as well as in compression tests; original gauge lengths down to 1.5 mm are supported.
Yuri Estrin and Hans Jürgen Maier
E. Schenuit et al., "Optical Strain Measurement on Small Specimens Based on Laser Speckles ", Materials Science Forum, Vols. 584-586, pp. 237-242, 2008