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Research Papers: Materials Technology

Fatigue Assessment of Aluminum Ship Details by Hotspot Stress Approach

[+] Author and Article Information
Bård Wathne Tveiten

SINTEF,
Trondheim, N-7465Norway

Stig Berge

Norwegian University of Science and Technology,
Trondheim, NO-7491Norway

Xiaozhi Wang

American Bureau of Shipping,
Houston, TX 77060

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received September 23, 2011; final manuscript received April 16, 2013; published online July 15, 2013. Assoc. Editor: Xin Sun.

J. Offshore Mech. Arct. Eng 135(4), 041401 (Jul 15, 2013) (10 pages) Paper No: OMAE-11-1084; doi: 10.1115/1.4024268 History: Received September 23, 2011; Revised April 16, 2013

This paper presents a robust methodology for fatigue assessment of aluminum ship details using a hot-spot stress range approach. A series of fatigue tests of a typical aluminum ship detail was carried out to obtain a design S–N curve. The test detail was analyzed by the finite element method using several modeling techniques and element types. The results from both experimental tests and finite element analysis are discussed. Recommendations on the procedure of fatigue assessment of aluminum ships including S–N curve to be used are also presented.

Copyright © 2013 by ASME
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References

Figures

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Fig. 4

Solid finite element model (deformation scaled by a factor of 18.5). Stress in longitudinal direction, S33 (global coordinate system). Element size at weld toe location, 1.5 mm × 1.5 mm × 1.5 mm (0.5t × 0.5t × 0.5t).

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Fig. 3

Schematic outline of test specimen

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Fig. 2

S–N data expressed in terms of IIW [1] hot-spot stress range definition, FAT 40 design curve (Figure from Ref. [14])

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Fig. 1

Definitions of stress used in fatigue analysis

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Fig. 5

Close-up of hot spot location B, shell finite element model (deformation is scaled by a factor 18.7). Stress in longitudinal direction at upper surface of flange, S22 (local coordinate, surface normal at flange [0,1,0]). Element size at weld toe location, 0.6 mm × 0.6 mm × 0.6 mm (0.2t × 0.2t × 0.2t).

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Fig. 6

Normalized longitudinal stress distribution along center line of stiffener close to weld toe location for various shell finite element models

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Fig. 7

Normalized longitudinal stress distribution along center line of stiffener close to weld toe location for the “converged” solid and shell finite element models, hot spot location B

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Fig. 8

Normalized longitudinal stress distribution along center line of stiffener close to weld toe location for the “converged” solid and shell finite element models, hot spot location A

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Fig. 9

Normalized longitudinal stress distribution obtained from finite element analyses using converged element mesh and element sizes of 1.0·t (3 mm)

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Fig. 10

Schematic outline of test rig arrangement (top) and picture of specimen (bottom) with outline of fatigue cracking (broken lines)

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Fig. 11

Normalized longitudinal stress distribution obtained from finite element analyses and strain gauge measurements, static test #1, FEA results derived at center line, HS A

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Fig. 12

Normalized longitudinal stress distribution obtained from finite element analyses and strain gauge measurements, static test #1, FEA results derived at center line, HS B

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Fig. 13

Close-up, normalized longitudinal stress distribution obtained from finite element analyses and strain gauge measurements, static test #1, FEA results derived at center line, HS B, close to hot-spot location

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Fig. 14

S–N data for fatigue life (100 mm crack) plotted versus 1.5t–0.5t extrapolated hot spot stress

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Fig. 15

S–N data for fatigue life (100 mm crack) plotted versus 0.5t hot spot stress

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