13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- the value of w in each material point of the solid analyzed. Different hardness distributions along the depth have been studied here. Thus the value of w corresponding to the value of the hardness at that depth has been imposed in the material for each Gauss integration point. The different hardness distributions imposed in the subsurface region of inner ring and the correspondent w distributions are shown in Fig. 5 (a)(d). At distances greater than 1 mm from the surface, HB, for distributions (a) and (b), are taken to be constant, at a value such that the related fatigue limit, w=w(HB), is approximately 360 MPa. This assumption is equivalent to considering how the effect of a surface hardening process would benefit the fatigue response of the bearing. Results show that the values of the damage factor n and the depth at which the maximum n is reached, are strongly dependent on the particular distribution of hardness imposed (Fig. 6). Figure 5. Hardness distributions ((a)-(b)) and correspondent values of w ((c)-(d)) in the first millimeter of depth . Figure 6. Damage factor versus distance from surface. In (a) the original Dang Vang safe locus has been used, while in (b) the bilinear limit curve, as described in section 2.1. The different distributions are referred to Fig. 5.
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