Strain field measurements in industrial applications using dual-beam digital speckle photography

Dual-beam digital speckle photography is a non-contacting full-field technique which can measure one strain component at the CCD-camera frequency. The technique uses two symmetrically incident laser beams of different wavelengths and the speckle field for each illumination beam is recorded simultaneously before and after object deformation. The system is designed for strain field measurements in rough environments. In this paper some experiments are performed to investigate the system performance. In a tensile test the measured strain value was found to be in good agreement with the strain given by resistance strain gauges. Experiments at elevated temperature have also been performed, where thermal strain fields were measured at 500°C.