###### Abstract
In Reference [5], fatigue tests were performed to estimate the coplanar and branch crack growth rates on rail and wheel steel under non-proportional mixed mode I/II loading cycles simulating the load on rolling contact fatigue cracks; sequential and overlapping mode I and II loadings were applied to single cracks in the specimens. Long coplanar cracks were produced under certain loading conditions. The fracture surfaces observed by scanning electron microscopy and the finite element analysis results suggested that the growth was driven mainly by in-plane shear mode (i.e., mode II) loading. Crack branching likely occurred when the degree of overlap between these mode cycles increased, indicating that such a degree of enhancement led to a relative increase in the maximum tangential stress range, based on an elasto-plastic stress field along the branch direction, compared to the maximum shear stress. Moreover, the crack growth rate decreased when the material strength increased because this made the crack tip displacements smaller. The branch crack growth rates could not be represented by a single crack growth law since the plastic zone size ahead of the crack tip increased with the shear part of the loading due to the T-stress, resulting in higher growth rates. In Reference [6], sequential and overlapping mode I and III loading cycles were applied to single cracks in round bar specimens. The fracture surface observations and the finite element analysis results suggested that the growth of long coplanar cracks was driven mainly by mode III loading. The cracks tended to branch when increasing the material strength and/or the degree of overlap between the mode I and III loading cycles. The equivalent stress intensity factor range that could consider the crack face contact and successfully regress the crack growth rate data was proposed for the branch crack. Based on the results obtained in this study, the mechanism of long coplanar shear-mode crack growth turned out to be the same regardless of whether the main driving force was in-plane shear or out-of-plane shear. The last paper in this Special Issue concerns real components and, in particular, aerospace structures, whose residual life in the presence of a service crack is evaluated. In Reference [7], the authors presented the results of a systematic crack propagation analysis campaign performed on a compressor-blade-like structure. The point of novelty was that different blade design parameters were varied and explored in order to investigate how the crack propagation rate in low cycle fatigue (LCF, at R ratio R = 0) could be reduced. The design parameters/variables studied in this work were as follows: (1) the length of the contact surfaces between the dovetail root and the disc, and (2) their inclination angle. Effects of the friction coefficient between the disc and the blade root were also investigated. The LCF crack propagation analyses were performed by recalculating the stress field as a function of the crack propagation by using the Fracture Analysis Code (Franc3D\({}^{\circledR}\)[[http://www.fracanalysis.com/Fracture](http://www.fracanalysis.com/Fracture)]([http://www.fracanalysis.com/Fracture](http://www.fracanalysis.com/Fracture)) Analysis Consultants, Inc 121 Eastern Heights Dr Ithaca, 14850 New York, NY, USA. Phone: 607-257-4970). The three co-guest-editors of this special issue shared the editorial duties, managing the review process for the papers considered for publication. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The editors would like to express their thanks to all authors of the Special Issue for their valuable contributions and to all reviewers for their useful efforts to provide valuable reviews. We expect that this Special Issue offers a timely view of advanced topics in the structural behaviour of advanced materials, which will stimulate further novel academic research and innovative applications. The authors declare no conflict of interest.