Weld related fatigue failure is one of the most common concerns in welded structures. From the fatigue design point of view, weld toe failure is preferable to weld root failure. Base plate thickness is a controlling parameter for weld toe failure, while weld metal size is a controlling parameter for weld root failure. However, controlling the weld metal size is not easy because the actual weld penetration and weld leg size vary along a weld and from weld to weld. Therefore, analyzing fatigue test data for weld root failure tends to enlarge scatter band due to variability in weld penetration and weld leg size when the nominal weld size is considered. The structural stress based weld fatigue master S-N curve adopted by 2007 ASME section VIII Div. 2 and new API 579/ASME FFS-1 was constructed by incorporating only clearly defined weld toe fatigue data. In this article, a simplified structural stress procedure was developed and a design master S-N curve for weld root failure was established based on the published fatigue test data. Consequently, the mean design master S-N curve for weld root failure is downshifted relative to the mean master S-N curve for weld toe failure, and has a wider scatter band. To be conservative, a crack path along weld throat is recommended for structural stress calculation. Also, the transverse shear stress effects on structural stress calculation can be ignored.

References

References
1.
Dong
,
P.
,
Zhang
,
J.
, and
Hong
,
J. K.
,
2005
, “
Structural Stress Analysis
,” U.S. Patent No. 6,901,809.
2.
Dong
,
P.
,
Hong
,
J. K.
,
Osage
,
D. A.
, and
Prager
,
M.
,
2002
, “
Master S-N Curve Method for Fatigue Evaluation of Welded Components
,” Welding Research Council Bulletin Vol.
474
,
Welding Research Council
.
3.
Dong
,
P.
,
Hong
,
J. K.
, and
Cao
,
Z.
,
2003
, “
Stress and Stress Intensities at Notches: ‘Short Crack Anomalous Growth’ Revisited
,”
Int. J. Fatigue
,
25
, pp.
811
825
.10.1016/S0142-1123(03)00130-0
4.
Dong
,
P.
, and
Hong
,
J. K.
,
2004
, “
The Master S-N Curve Approach to Fatigue Evaluation of Offshore and Marine Structures
,”
Proceedings of the 23rd International Conference on Offshore Mechanics and Arctic Engineering, Volume 2: Safety and Reliability, Materials Technology Workshop
, Paper No. OMAE2004-51324, pp.
847
855
,
OMAE
.10.1115/OMAE2004-51324
5.
Dong
,
P.
, and
Hong
,
J. K.
,
2006
, “
A Robust Structural Stress Parameter for Evaluation of Multiaxial Fatigue of Weldments
J. ASTM Int.
,
3
(
7
), Paper No. JAI100348.10.1520/JAI100348
6.
Dong
,
P.
,
Hong
,
J. K.
, and
De Jesus
,
A. M. P.
,
2007
, “
Analysis of Recent Fatigue Data Using the Structural Stress Procedure in ASME Div 2 Rewrite
,”
ASME J. Pressure Vessel Technol.
,
129
(
3
), pp.
355
362
.10.1115/1.2748818
7.
Dong
,
P.
, and
Hong
,
J. K.
,
2007
, “
On the Residual Stress Profiles in New API 579/ASME FFS-1 Appendix E
,”
Welding in the World
,
51
(
5–6
), pp.
119
127
.
8.
Kyuba
,
H.
, and
Dong
,
P.
,
2005
, “
Equilibrium-Equivalent Structural Stress Approach to Fatigue Evaluation of a Rectangular Hollow Section Joint
,”
Int. J. Fatigue
,
27
, pp.
85
94
.10.1016/j.ijfatigue.2004.05.008
9.
Kang
,
H. T.
,
Dong
,
P.
, and
Hong
,
J. K.
,
2007
, “
Fatigue Analysis of Spot Welds Using a Mesh-Insensitive Structural Stress Approach
,”
Int. J. Fatigue
,
29
, pp.
1546
1553
.10.1016/j.ijfatigue.2006.10.025
10.
Hong
,
J. K.
, and
Dong
,
P.
,
2008
,
Analysis of Solder Fatigue in Electronic Packaging Using a Mesh-Insensitive Structural Stress Method
,”
Mater. Sci. Forum
,
580-582
, pp.
233
238
.10.4028/www.scientific.net/MSF.580-582.233
11.
Knight
,
J. W.
,
1979
, “
Some Basic Fatigue Data for Various Types of Fillet Welded Joints in Structural Steel
,”
Welding Res. Int.
,
9
(
3
), pp.
22
42
.
12.
Data from DSME
,
2005
,
Original data from Fraunhoper Institute
.
13.
Andrews
,
R. M.
,
1987
, “
The Effect of Misalignment on the Fatigue Strength of Welded Cruciform Joints
,” TWI Report No. 354/1987.
14.
Denny
,
A. K.
, and
Jubb
,
J. E. M.
,
1977
, “
Fatigue Crack Propagation in Submerged Arc Cruciform Welded Joints
,”
Welding Res. Int.
,
7
(
1
), pp.
57
75
.
15.
Sorensen
,
J. D.
,
Tychsen
,
J.
,
Andersen
,
J. U.
, and
Brandstrup
,
R. D.
,
2006
, “
Fatigue Analysis of Load-Carrying Fillet Welds
,”
ASME J. Offshore Mech. Arct. Eng.
,
128
, pp.
65
74
.10.1115/1.2163876
16.
Lotsberg
,
I.
,
2003
, “
Fatigue Capacity of Fillet Welded Connections Subjected to Axial and Shear Loading
,” IIW Doc. XIII-2000-03(XV-1146-03),
IIW
.
17.
MacFarlane
,
D. S.
, and
Harrison
,
J. D.
,
1965
, “
Some Fatigue Tests of Load Carrying transverse Fillet Welds
,”
Br. Welding J.
,
12
, pp.
613
623
.
18.
Gurney
,
T. R.
, and
MacDonald
,
K.
,
1995
, “
Literature Survey on Fatigue Strengths of Load-Carrying Fillet Welded Joints Failing in the Weld
,” OTH 91 356,
Health and Safety Executive
.
19.
Kainuma
,
S.
, and
Kim
,
I.-T.
,
2005
, “
Fatigue Strength Evaluation of Load-Carrying Cruciform Fillet-Welded Joints Made With Mill Steel Plates of Different Thickness
,”
Int. J. Fatigue
,
27
, pp.
810
816
.10.1016/j.ijfatigue.2005.01.002
20.
Eurocode 3, EN 1993-1-9, Steel Structures, Part 1-9: Fatigue, 1993.
21.
Fatigue Design of Offshore Steel Structures
,”
Recommended Practice DNV-RP-C203, Det Norske Veritas
,
August 2005
.
You do not currently have access to this content.