Spatiotemporal regularization for digital image correlation: Application to infrared camera frames

International audienceThe spatiotemporal response of a stainless steel plate undergoing cyclic laser shock is recorded with an infrared camera, and Digital Image Correlation (DIC) is used to analyze both displacement and temperature fields. Two very challenging difficulties are addressed: i) large gray level variations (due to temperature changes) and ii) convection effects affecting images. To this aim, a spatiotemporal regularization is designed exploiting a numerical model of the test. The thermomechanical space-time predictions are first processed through Karhunen-Loeve decomposition to extract dominant temporal and spatial modes. The temporal modes are then inserted in a spatiotemporal DIC framework to estimate the experimental spatial modes that account for both gray level variations (and hence temperature) and displacement fields. It is shown that with only three modes, the full thermomechanical response of the material is captured. The temporal regularization issued from the model also allows the spurious effect of convection to be filtered out. Because of the drastic decrease in the number of degrees of freedom due to data reduction, the number of analyzed frames can be reduced from 50 down to 6 to capture the thermomechanical response, thereby leading to an enhanced effciency