Crack-Closure Measurements in Low-Cycle Fatigue With Digital Image Correlation

In this work, an experimental campaign devoted to measure closure levels onto specimens subjected to low-cycle fatigue (LCF) conditions is described. Two different straining conditions were investigated (i.e., R 1⁄4 1 and R 1⁄4 0.5). The measurements of rop, crack-opening stresses, were carried out by adopting the concept of “crack-tip opening displacements” and “local strain cycles.” However, instead of the original strain gauges measurements above the plane of the propagating crack, the strain cycles were measured by DIC in proximity of the crack tip. Experimental results were compared to those provided by the analytical model proposed by Newman.