Design curves, such as fatigue design S-N curves, are usually constructed by analyzing test data, which often exhibit large scatter. There are several methods available to construct a design curve and some of these methods, with varying degrees of conservativeness, accuracy, and simplicity, have been adopted by engineering standards, codes and guidelines, such as the American Society of Mechanical Engineers (ASME) Code. However, to meet increasing engineering demands, a simplified and user-friendly engineering method with rigorous mathematical and physical basis is still urgently needed to accurately manage the margin of safety and decrease the cost. In this paper, the current engineering practices for constructing a design curve are briefly reviewed, followed by the introduction of the tolerance limit concept because of its ability to relate the design curve well to sample size, failure probability, and confidence level. Recognizing the physical unsoundness of the hyperbolic shape of the design curves constructed with the Owen's tolerance limit approach, a new simple design curve construction method is developed based on the “equal partition principle.” Finally, the predicted results from various methods are compared and the advantage of the new method is demonstrated with several worked examples.

References

References
1.
Shen
,
C. L.
,
Wirsching
,
P. H.
, and
Cashman
,
G. T.
,
1996
, “
Design Curve to Characterize Fatigue Strength
,”
J. Eng. Mater. Technol.
,
118
, pp.
535
541
.10.1115/1.2805953
2.
Shen
,
C. L.
,
1994
, “
The Statistical Analysis of Fatigue Data
,” Ph.D. dissertation, Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, AZ.
3.
Lee
,
Y. L.
,
Pan
,
J.
,
Hathaway
,
R.
, and
Barkey
,
M.
,
2005
,
Fatigue Testing and Analysis: Theory and Practice
,
Elsevier Butterworth-Heinemann
,
Boston
.
4.
Criteria of the ASME Boiler and Pressure Vessel Code for Design by Analysis in Sections III and VIII, Division 2
,
1969
,
The American Society of Mechanical Engineers
,
New York
.
5.
Det Norske Veritas
,
2010
, “
Fatigue Design of Offshore Steel Structures
,” DNV-RP-C203.
6.
British Standard
,
1993
, “
Code for Practice for Fatigue Design and Assessment of Steel Structures
,” BS7608.
7.
Owen
,
D. B.
,
1968
, “
A Survey of Properties and Applications of the Noncentral t-Distribution
,”
Technometrics
,
10
, pp.
445
478
.
8.
ASTM
,
1991
, “
Standard Practice for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life Fatigue Data
,” E739-10.
9.
Lieberman
,
G. J.
,
1957
, “
Tables for One-Sided Statistical Tolerance Limits
,” Applied Mathematics and Statistics Laboratory, Stanford University, Stanford, CA, Technical Report No. 34.
10.
Natrella
,
M. G.
,
1963
,
Experimental Statistics
,
National Bureau of Standards Handbook 91, US Government Printing Office
,
Washington, DC
.
11.
Link
,
C. L.
,
1985
, “
An Equation for One-Sided Tolerance Limits for Normal Distributions
,” Research Paper FPL 458, U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, WI.
12.
Abramowitz
,
M.
, and
Stegun
,
I. A.
, eds.,
1972
,
Handbook of Mathematical Functions With Formulas, Graphs, and Mathematical Tables
,
9th printing
,
Dover Publications
,
New York
.
13.
Neter
,
J.
,
Wasserman
,
W.
, and
Kutner
,
M. H.
,
1990
,
Applied Linear Statistical Models
,
Richards D. Irwin, Inc.
,
Homewood, IL
.
14.
Wei
,
Z.
,
Luo
,
L.
,
Lin
,
B.
,
Konson
,
D.
, and
Yang
,
F.
,
2012
, “
Design Curve Construction Based on Two-Stress Level Test Data
,” SAE Technical Paper No. 2012-01-0069.
15.
Dong
,
P.
,
Hong
,
J. K.
,
Osage
,
D.
, and
Prager
,
M.
,
2002
, “
Master S-N Curve Method for Fatigue Evaluation of Welded Components
,” WRC Bulletin, ISBN#1-58145-481-3.
16.
Kumar
,
K. S.
,
Van Swygenhoven
,
H.
, and
Suresh
,
S.
,
2003
, “
Mechanical Behavior of Nanocrystalline Metals and Alloys
,”
Acta Mater.
,
51
, pp.
5743
5774
.10.1016/j.actamat.2003.08.032
17.
Bažant
,
Z. P.
,
1999
, “
Size Effect on Structural Strength: A Review
,”
Arch. Appl. Mech.
,
69
, pp.
703
725
.10.1007/s004190050252
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