Issue 35

R.A. Cardoso et alii, Frattura ed Integrità Strutturale, 35 (2016) 405-413; DOI: 10.3221/IGF-ESIS.35.46 412 Figure 10 : Results for crack path simulation, ∆b=70μm. Note that although the initial estimate of crack initiation path was 4° while the actual path was 17°, the direction of crack propagation obtained via max( Δ k 1 ) tends to the location of the real crack as it becomes larger. However, the min(Δ τ ) criterion leads to a complete different path that has no correlation at all with the experimental result. C ONCLUSIONS ome methodologies to predict the direction of crack initiation and further propagation under fretting conditions were assessed, where available experimental data were used to evaluate the accuracy of the methodologies. Two methods based on critical distances to estimate the crack initiation planes were studied. The critical direction method, provided better results than the critical plane model, which was not able to produce any reasonable estimates of crack initiation direction. In order to predict the crack propagation path two distinct methodologies were applied, one based on the maximum SIF range mode I in an infinitesimal kinked crack with origin in the pre-existent crack and another based on the stress field near to the crack tip. The criteria based on stress field, min(Δ τ ) , led to inconsistent predictions, whereas the criteria based on SIF, provided good agreement with the experimental response, even from a not so good choice for the direction of crack initiation. Further work mainly for earlier stages of crack birth need to be conducted in order to establish more accurate estimates of crack path in fretting conditions. R EFERENCES [1] Araújo, J.A., Nowell, D., Analysis of pad size effects in fretting fatigue using short crack arrest methodologies, Int J Fatigue, 21 (1999) 847-856. [2] Dubourg, M.C., Lamacq, V., Stage II crack propagation direction determination under fretting fatigue loading: a new approach in accordance with experimental observations. In: Hoeppner DW, et al., editors. Fretting fatigue: current technology and practices, ASTM STP 1367, West Conshohocken; (2000) 436-450. [3] Susmel, L., Taylor, D., Non-propagating cracks and high-cycle fatigue failures in sharply notched specimens under in phase Mode I and II loading, Eng F Analysis, 14 (2007) 861-876. [4] Taylor, D., Geometrical effects in fatigue: a unifying theoretical midel, Int J Fatigue, 21 (1999) 413-420. [5] Susmel, L., Taylor, D., Can the conventional high-Cycle multiaxial fatigue criteria be re-interpreted in terms of the theory of crical distancies: SDHM, 2 (2006) 91-180. [6] Taylor ,D., The Theory of Critical Distances. Oxford: Elsevier. 1st edition, (2007). S