LCF and crack growth: Recent results obtained by DIC

Nowadays, several components for aerospace and energy applications (i.e., turbine disks, offshore pipelines, and combustor chambers) are designed following a safe-life approach in the low cycle fatigue (LCF) regime. As also in the LCF regime it is worth adopting a damage tolerance design, fatigue life is assessed considering a crack propagating from the first load cycle, starting from an initial defect present in the component's most-stressed region or from a microstructural feature. In this frame, fatigue crack growth is described considering LCF conditions, where the driving force at the crack tip can be described with the ΔJeff parameter. The paper aims to give an overview of the potential applications and perspectives for the adoption of digital image correlation (DIC) measurements to study LCF nucleation and propagation. A visual technique based on the DIC displacement fields was developed to measure crack opening and closing levels in the presence of large strains. The technique is applied to different materials (steels, AlSi10Mg, nickel-based super-alloys). In addition, further applications of the DIC strain measurements are revised for the study of the nucleation stage and the crack tip process zone.