The influence of finite three dimensional axial erosion on the fatigue life of partially autofrettaged pressurized cylinders Article

cited authors

  • Levy, C; Perl, M; Ma, Q

fiu authors

abstract

  • Erosion geometry effects on the mode I stress intensity factor (SIF) for a crack emanating from an erosion's deepest point in a finitely eroded, fully autofrettaged, pressurized, thick-walled cylinder as well as an infinitely eroded, partially autofrettaged, pressurized cylinder are investigated. The problem is solved via the FEM method. Autofrettage, based on von Mises yield criterion, is simulated by thermal loading and SIFs are determined by the nodal displacement method. SIFs are evaluated for a variety of relative crack depths, a/t = 0.01 - 0.45 and crack ellipticities, a/c = 0.5 - 1.5 emanating from the tip of an erosion of various geometries, namely, a) semi-circular erosions of relative depths of 1-10% of the cylinder's wall thickness, t; b) arc erosions for several dimensionless radii of curvature, r't = 0.05 - 0.4; and c) semi-elliptical erosions with ellipticities of d/h = 0.5-1.5. In the finite erosion case, the semi-erosion length to the semicrack length, Le/c, is taken between 1 and 10, whereas the autofrettage cases investigated include 30%, 60% and 100% autofrettage. The normalized SIF of a crack emanating from a finite erosion is found to rise sharply for values of Le/c<3 and remain almost constant afterwards. The normalized effective SIF values for the same configuration are found also to rise sharply initially, but they continue rising, albeit at a much slower rate for Le/c>3. In the case of partial autofrettage, both the normalized SIFs and normalized effective SIFs of a crack emanating from an infinitely long erosion decrease with increasing autofrettage with the most rapid decrease occurring between 0-60% autofrettage. Apart from the well known effects of crack geometry and erosion geometry on the fatigue life of pressurized cylinders, it appears that the two dichotomous trends found in this work may have a profound effect on the fatigue life as well and need further study.

publication date

  • December 1, 2000

start page

  • 163

end page

  • 168

volume

  • 417