Issue 38

H. Wu et alii, Frattura ed Integrità Strutturale, 38 (2016) 99-105; DOI: 10.3221/IGF-ESIS.38.13 99 Focussed on Multiaxial Fatigue and Fracture Application of the Moment Of Inertia method to the Critical-Plane Approach Hao Wu School of Aerospace Engineering and Applied Mechanics, Tongji University, Siping Road 1239, 200092, Shanghai, P.R.China wuhao@tongji.edu.cn Marco Antonio Meggiolaro, Jaime Tupiassú Pinho de Castro Pontifical Catholic University of Rio de Janeiro, PUC-Rio, R. Marquês de São Vicente 225, Rio de Janeiro, 22451-900, Brazil meggi@puc-rio.br , jtcastro@puc-rio.br A BSTRACT . The Moment-Of-Inertia (MOI) method has been proposed by the authors to solve some of the shortcomings of convex-enclosure methods, when they are used to calculate path-equivalent ranges and mean components of complex non-proportional (NP) multiaxial load histories. In the proposed 2D version for use with critical-plane models, the MOI method considers the non-proportionality of the projected shear-shear history on each candidate plane through the shape of the load path, providing good results even for challenging non-convex paths. The MOI-calculated path-equivalent shear stress (or strain) ranges from each counted load event can then be used in any shear-based critical-plane multiaxial fatigue damage model, such as Findley’s or Fatemi-Socie’s. An efficient computer code with the shear-shear version of the MOI algorithm is also provided in this work. K EYWORDS . Multiaxial fatigue; Non-proportional loadings; Equivalent ranges; Critical-Plane Approach. Citation: Wu, H., Meggiolare, M.A., de Castro, J.T.P., Application of the Moment Of Inertia method to the Critical-Plane Approach, Frattura ed Integrità Strutturale, 38 (2016) 99-105. Received: 12.05.2016 Accepted: 15.06.2016 Published: 01.10.2016 Copyright: © 2016 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION irection-sensitive materials like most metallic alloys tend to initiate a single dominant microcrack under fatigue loadings. Under multiaxial loading conditions this behavior tends to be well modeled by critical-plane fatigue- damage models, which search for the material plane at the critical point where the corresponding accumulated damage parameter is maximized. Although in general any plane can be a candidate at the critical point, Bannantine and Socie [1] narrowed down the search space for the critical plane at the critical point of the structural component when it is under free-surface conditions, as usual, classifying the most common microcracks into three types, which depend on the fatigue damage mechanism: Case A tensile or Case A shear microcracks, which grow at the critical point along planes perpendicular to the free surface; and D