The safe and efficient operation of modern heavy duty gas turbines requires a reliable prediction of fatigue behavior of turbine components. Fatigue damage is located in areas where cyclic stress and strain amplitudes are highest. Thus, geometrical notches associated with stress/strain concentrations and stress/strain gradients appear to be the most important sites for fatigue crack initiation. The paper addresses a nonlocal concept for cyclic life prediction of notched components. Contrary to various local approaches in the field, the proposed method explicitly accounts for stress and strain gradients associated with notches arising from grooves, cooling holes, fillets, and other design features with stress raising effect. As a result, empirical analytical expressions for considering either strain or stress gradients for cyclic life prediction are obtained. The method has been developed from cyclic test data on smooth and notched specimens made of a ferritic 1.5CrNiMo rotor steel. The analytical formulations obtained have then been applied to test data on the nickel base superalloy MAR-M247 CC showing a good agreement between prediction and measurement. Moreover, the proposed nonlocal lifing concept has been validated by component tests on turbine blade firtrees. The predicted number of cycles to failure correlates well with the experimental results showing the applicability of the proposed method to complex engineering designs.

1.
Dowling
,
N. E.
, 1999,
Mechanical Behavior of Materials
,
Prentice-Hall
,
Englewood Cliffs, NJ
.
2.
Suresh
,
S.
, 1991,
Fatigue of Materials
,
Cambridge Solid State Science Series
,
Cambridge University Press
,
Cambridge, UK
.
3.
Makkonen
,
M.
, 2003, “
Notch Size Effects in the Fatigue Limit of Steels
,”
Int. J. Fatigue
0142-1123,
25
, pp.
17
26
.
4.
Ciavarella
,
M.
, and
Meneghetti
,
G.
, 2004, “
On Fatigue Limit in the Presence of Notches: Classical vs. Recent Unified Formulations
,”
Int. J. Fatigue
0142-1123,
26
, pp.
289
298
.
5.
Sehitoglu
,
H.
, 1983, “
Fatigue Life Prediction of Notched Members Based on Local Strain and Elastic-plastic Fracture Mechanics Concepts
,”
Eng. Fract. Mech.
0013-7944,
18
, pp.
609
621
.
6.
Peterson
,
R. E.
, 1974,
Stress Concentration Factors
,
Wiley
,
New York
.
7.
Taylor
,
D.
, and
O’Donnell
,
M.
, 1994, “
Notch Geometry Effects in Fatigue: A Conservative Design Approach
,”
Eng. Failure Anal.
1350-6307,
1
, pp.
275
287
.
8.
Bellett
,
D.
,
Taylor
,
D.
,
Marco
,
S.
,
Mazzeo
,
E.
,
Guillois
,
J.
, and
Pircher
,
T.
, 2005, “
The Fatigue Behavior of Three-dimensional Stress Concentrations
,”
Int. J. Fatigue
0142-1123,
27
, pp.
207
221
.
9.
Filippini
,
M.
, 2000, “
Stress Gradient Calculation at Notches
,”
Int. J. Fatigue
0142-1123,
22
, pp.
397
409
.
10.
Xu
,
R. X.
,
Thompson
,
J. C.
, and
Topper
,
T. H.
, 1995, “
Practical Stress Expressions for Stress Concentration Regions
,”
Fatigue Fract. Eng. Mater. Struct.
8756-758X,
18
, pp.
885
895
.
11.
Glinka
,
G.
, and
Newport
,
A.
, 1987, “
Universal Features of Elastic Notch-Tip Stress Fields
,”
Int. J. Fatigue
0142-1123,
8
, pp.
235
237
.
12.
Noda
,
N.-A.
, and
Takase
,
Y.
, 2006, “
Stress Concentration Formula Useful for all Notch Shape in a Round Bar
,”
Int. J. Fatigue
0142-1123,
28
, pp.
151
163
.
13.
Siebel
,
E.
, and
Stieler
,
M.
, 1955, “
Ungleichförmige Spannungsverteilung bei schwingender Beanspruchung
,”
VDI Z. (1857-1968)
0372-453X,
97
(
5
), pp.
121
126
.
14.
Qylafku
,
G.
,
Azari
,
Z.
,
Kadi
,
N.
,
Gjonaj
,
M.
, and
Pluvinage
,
G.
, 1999, “
Application of a New Model Proposal for Fatigue Life Prediction on Notches and Key-Seats
,”
Int. J. Fatigue
0142-1123,
21
, pp.
753
760
.
15.
Naik
,
R. A.
,
Lanning
,
B. D.
,
Nicholas
,
T.
, and
Kallmeyer
,
A. R.
, 2005, “
A Critical Plane Gradient Approach for the Prediction of Notched HCF Life
,”
Int. J. Fatigue
0142-1123,
27
, pp.
481
492
.
16.
Härkegard
,
G.
,
Denk
,
J.
, and
Stärk
,
K.
, 2005, “
Growth of Naturally Initiated Fatigue Cracks in Ferritic Gas Turbine Rotor Steels
,”
Int. J. Fatigue
0142-1123,
27
, pp.
715
726
.
17.
Coffin
,
L. F.
, 1987, “
Notch Fatigue Crack Initiation Studies in a High Strength Nickel Base Superalloy
,”
Eng. Fract. Mech.
0013-7944,
28
, pp.
485
503
.
18.
Gangloff
,
R. P.
, 1981, “
Electrical Potential Monitoring of Crack Formation and Subcritical Crack Growth for Small Defects
,”
Fatigue Fract. Eng. Mater. Struct.
8756-758X,
4
, pp.
15
33
.
19.
Johnson
,
H. H.
, 1965, “
Calibrating the Electric Potential Method for Studying Slow Crack Growth
,”
Mater. Res. Stand.
0025-5394,
5
, pp.
442
445
.
20.
ABAQUS
, 2003,
User’s Manual
, Version 6.4, Vol.
III
, Hibbitt, Karlsson, & Sorenson, Inc.
21.
Steinchen
,
W.
,
Yang
,
L. X.
,
Kupfer
,
G.
, and
Mäckel
,
P.
, 1998, “
Strain Analysis by Digital Shearography: Potentials, Limitations and Demonstrations
,”
J. Strain Anal. Eng. Des.
0309-3247,
33
, pp.
171
182
.
22.
Steinchen
,
W.
,
Kupfer
,
G.
,
Mäckel
,
P.
, and
Vössing
,
F.
, 1999, “
Determination of Strain Distributions by Means of Digital Shearography
,”
Measurement
0263-2241,
26
, pp.
79
90
.
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