The real part is however not perfect in order to

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Unformatted text preview: ced by the macro geometrical compensations (Δgeo). Consequently, small variations of the real geometry of the parts may induce great changes of the contact stresses. The maximum equivalent stress in the material may thus exceed the ultimate stress or fatigue limit of the material, lead ing to early fracture of the mechanism. 2.2. M icro geometrical accommodation The micro geometrical accommodation of each surface under contact (MGA) can be characterized by the evolution of its bearing ratio curves (t(c) in figure 3) during operation. The bearing capacity depends on the quality of the surfaces (R roughness, W wave and form defect), the hardness of the materials and the running time (N cycles). It evolves during the life of the part, due to local plastic deformations or abrasions. Such micro geometrical accommodations modify the distribution of the matter around the mean surface profile, increasing t he number of points under contact (figure 3). 228 J. M. Linares et al. Micro geometrical accommodation t(c) = g (Form, R, W) N cycle = 0 N cycle high b a ≠ c Figure 3; Micro geometrical accommodation The ideal surface profile for a mechanic al contact and the related bearing ratio curv...
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This note was uploaded on 08/03/2010 for the course DD 1234 taught by Professor Zczxc during the Spring '10 term at Magnolia Bible.

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