Reengineering of the aircraft structural life prediction process to fully exploit advances in very high performance digital computing is proposed. The proposed process utilizes an ultrahigh fidelity model of individual aircraft by tail number, a Digital Twin, to integrate computation of structural deflections and temperatures in response to flight conditions, with resulting local damage and material state evolution. A conceptual model of how the Digital Twin can be used for predicting the life of aircraft structure and assuring its structural integrity is presented. The technical challenges to developing and deploying a Digital Twin are discussed in detail.

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Reengineering Aircraft Structural Life Prediction Using a Digital Twin

Roles of microstructure in fatigue crack initiation

Slip and fatigue crack formation processes in an α/β titanium alloy in relation to crystallographic texture on different scales

https://uwaterloo.ca/centre-advanced-materials-joining/sites/ca.centre-advanced-materials-joining/files/uploads/files/13_a_noroozi_2005.pdf

A two parameter driving force for fatigue crack growth analysis

The reach of tribology has expanded in diverse fields and tribology related research activities have seen immense growth during the last decade. This review takes stock of the recent advances in research pertaining to different aspects of tribology within the last 2 to 3 years. Different aspects of tribology that have been reviewed including lubrication, wear and surface engineering, biotribology, high temperature tribology, and computational tribology. This review attempts to highlight recent research and also presents future outlook pertaining to these aspects. It may however be noted that there are limitations of this review. One of the most important of these is that tribology being a highly multidisciplinary field, the research results are widely spread across various disciplines and there can be omissions because of this. Secondly, the topics dealt with in the field of tribology include only some of the salient topics (such as lubrication, wear, surface engineering, biotribology, high temperature tribology, and computational tribology) but there are many more aspects of tribology that have not been covered in this review. Despite these limitations it is hoped that such a review will bring the most recent salient research in focus and will be beneficial for the growing community of tribology researchers.

/pdf/a-review-of-recent-advances-in-tribology-48dk6nml6e.pdf

A review of recent advances in tribology

Fatigue crack initiation was studied in a bimodal TA6V titanium alloy. A ghost structure inherited from the forging process, the scale of which is roughly 100 times the apparent grain size, was found to govern the initiation process. In these macrograins, that we have labelled macrozones, most of the primary alpha grains (αp) are found to display the same crystallographic orientation. Fatigue cracks are initiated on the basal plane or, if basal slip is difficult, on the prismatic plane. Thus in macrozones, where basal or prismatic slip is easy, numerous neighbouring tiny cracks appear over the whole macrozone, which have the size of the primary αp grains. In these macrozones the contribution of crack coalescence to crack growth is consequently very significant. On the contrary, if basal and prismatic slips are both difficult in the macrozone, no crack can be found in the corresponding macrozone. The crack initiation process is thus highly heterogeneous at the scale of the macrozone. Furthermore, this microstructure is found to induce a large scatter in the fatigue life of notched samples.

Local texture and fatigue crack initiation in a Ti-6Al-4V titanium alloy

Plane strain crack closure and cyclic hardening

Cyclic plasticity and variable amplitude fatigue

Mode II fatigue crack growth tests as well as tests in sequential mode I and then mode II were performed on ferritic‐pearlitic steel. For ΔKII ranging from 7 to 43 MPa m−−√m\sqrt{m}, bifurcation occurs after 12–450 μm of coplanar growth at a decreasing speed. By contrast, hundreds of micrometres of constant speed coplanar growth were obtained under sequential mode I and then mode II loading, for ΔKII=20MPAm−−√m\sqrt{m} and ΔKI ranging from 0.25 to 1.0 ΔKII. The crack growth rate is a simple sum of the contributions of each mode for ΔKI= 0.25 ΔKII but above this value a synergetic effect is found. The mechanism of this fast‐propagation mode is discussed in the light of strain range maps ahead of the crack tip obtained by digital SEM image correlation and elastic–plastic finite element calculations. The stability of the crack path according to the maximum growth rate criterion is demonstrated.

Sylvie Pommier

Papers

Local texture and fatigue crack initiation in a Ti-6Al-4V titanium alloy

Plane strain crack closure and cyclic hardening

Cyclic plasticity and variable amplitude fatigue

Fatigue crack growth under non-proportional mixed-mode loading in ferritic-pearlitic steel

Extended Finite Element Method for Crack Propagation