13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- 4.2. Computation of the SIF parameter, crack meshing An automatic Matlab code was developed to generate Abaqus input scripts, which remesh the cracks in a fretting cylinder/plane interface during the propagation’s stage. This model with its mesh was inspired by the work of H. Proudhon [5]. The crack patch can be located anywhere in the plane's interface and can be described using sequential segments to reproduce as close as possible the real crack path. In the present investigation, crack nucleation is located at the contact border which is confirmed by experimental observations and multiaxial fatigue Modelling [1, 2, 6]. Two different crack path descriptions will be considered in the present analysis: a) The crack is normal to the surface. Indeed, as indicated in the introduction, in numerous works published in the literature [1, 2] the crack is assumed to propagate in the normal direction of the surface in a fretting configuration. For such conditions only, one segment is required for the FEM simulation. b) The crack is kinked. The path is described thanks to three segments provided in Figure 6.b. to approximate the real evolution of the crack propagation. This involves an angle of nearly 47.5° on the surface down to 0° deeper below the interface. This description is more complex to implement but it is also more relevant considering the real crack path evolution. Figure 6. Illustration of the two crack mesh developed in the present investigation a) Plain normal crack hypothesis - b) Kinked crack's description The Contour Integral's method (CI) is used by Abaqus 6.9 to estimate Stress Intensity Factors (SIF) at the crack tip. First, the Rice's integral (J-integral) is calculated, to then be related to KI and KII [7]. CPE3 triangular elements are used everywhere in the model except for the crack tip, where CPE4 quadrilateral elements are used for the CI. In the present analysis, only the mode I component (KI) will be considered as it is applied in many fretting fatigue modelling description [1]. Although the
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