Phasenschiebe-Shearografie misst Dehnungen

The digital-shearography in conjunction with a phase-shifting unit can be applied for interferometric measurements of longitudinal and lateral strains by loading specimens in a tensile testing machine. By turning a mirror in one of the two illumination arms of the interferometer for a very small angle, a pair of sheared images of the object is generated on the image plane of the CCD-camera. Therefore this measuring technique is called shearography. This paper deals with a special shearing device with two shearing directions in conjunction with several illumination beams to determine the complete strains. Measuring the strains of the specimen in a tensile testing machine the formation of the interference fringe pattern in the elastic and elasto-plastic range can be observed on the screen in real time.