LCF and crack growth: recent results obtained by DIC

Abstract

Abstract. 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 ΔJ eff 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.

Application of high‐performance DIC for a comprehensive evaluation of biaxial fatigue crack growth experiments

“…As it is a special trial with mixed HCF and LCF loads, the images of 575 cycles—two HCF cycles before and after 115 LCF cycles—are stored completely for a detailed evaluation of crack opening/closing behaviour. [ 29 ] After the trial, automated postprocessing is started for the full‐field evaluation described subsequently. The postprocessing time is divided into 14 min on the GPU for full‐field DIC processing of 1200 images and another 15 min to process the crack growth results shown in Figure 7 in a Python script.…”

Suitability of DIC and ESPI optical methods for monitoring fatigue damage development in X10CrMoVNb9-1 power engineering steel

“…However, the high sensitivity to vibration of ESPI setup practically narrows its application to the laboratory scale. On the other hand, the DIC was successfully used to determine the fatigue life of different materials, for example: aluminium alloys [25], nickel-based alloys [26], glass fibre-reinforced polymer composites [27], woven organic matrix composites [28] or even asphalt concrete [29].…”