3-D Stress Intensity Factors for arrays of inner radial lunular or crescentic cracks in thin and thick-walled spherical pressure vessels

M. Perl, V. Bernstein

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Some spherical pressure vessels are manufactured by methods such as the Integrated Hydro-Bulge Forming (IHBF) method, where the sphere is composed of a series of double curved petals welded along their meridional lines. Such vessels are susceptible to multiple radial cracking along the welds. For fatigue life assessment and fracture endurance of such vessels one needs to evaluate the Stress Intensity Factors (SIF) distribution along the fronts of these cracks. However, to date, only one 3-D solution for the SIF for a circumferential crack in a thick sphere is available, as well as 2-D SIFs for one through the thickness crack in thin spherical shells. In the present paper, mode I SIF distributions for a wide range of lunular and crescentic cracks are evaluated. The 3-D analysis is performed, via the FE method employing singular elements along the crack front, for five geometries representing thin, moderately thick, and thick spherical pressure vessels with outer to inner radius ratios of η=Ro/Ri=1.01, 1.05, 1.1, 1.7, and 2.0. SIFs are evaluated for arrays containing n=1-20 cracks; for a wide range of crack depth to wall thickness ratio, a/t, from 0.025 to 0.95; and for various ellipticities of the crack, i.e., the ratio of crack depth to semi crack length, a/c, from 0.2 to 1.5. The obtained results clearly indicate that the SIFs are considerably affected by the three-dimensionality of the problem and by the following parameters: the geometry of the sphere- η, the number of cracks in the array-n, the depth of the cracks-a/t, and their ellipticitya/

Original languageEnglish
Title of host publicationASME 2008 Pressure Vessels and Piping Conference, PVP2008
Pages3-11
Number of pages9
DOIs
StatePublished - 1 Dec 2008
EventASME 2008 Pressure Vessels and Piping Conference, PVP2008 - Chicago, IL, United States
Duration: 27 Jul 200831 Jul 2008

Publication series

NameAmerican Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP
Volume5
ISSN (Print)0277-027X

Conference

ConferenceASME 2008 Pressure Vessels and Piping Conference, PVP2008
Country/TerritoryUnited States
CityChicago, IL
Period27/07/0831/07/08

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