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

Summary The spatiotemporal response of a stainless steel plate undergoing cyclic laser shock is recorded with an infrared camera, and digital image correlation 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‐Loève decomposition to extract dominant temporal and spatial modes. The temporal modes are then inserted in a spatiotemporal digital image correlation 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 3 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. Due to the drastic decrease in the number of degrees of freedom because of data reduction, the number of analyzed frames can be reduced from 50 down to 6 to capture the thermomechanical response, thereby leading to enhanced efficiency.