Changes within the global energy market and a demand for a more flexible operation of gas- and steam-turbines lead to higher utilization of main components and raise the question how to deal with this challenge. One strategy to encounter this is to increase the accuracy of the lifetime assessment by quantifying and reducing conservatisms. At first the impact of considering a fracture mechanical notch support under creep-fatigue loading is studied by discussing the results of an extensive experimental program performed on notched round-bars under global strain control. A proposal of how to consider this fracture mechanical notch support within a lifetime assessment is discussed within the second part of the paper. Here, a theoretical finite element method (FEM)-based concept is introduced and validated by comparing the theoretical prediction with the results of the previously mentioned experimental study. Finally, the applicability of the developed and validated FEM-based procedure is demonstrated.

References

References
1.
Dowling
,
N. E.
,
1979
, “
Notched Member Fatigue Life Predictions Combining Crack Initiation and Propagation
,”
Fatigue Eng. Met. Struct.
,
2
(
2
), pp.
129
138
.
2.
Madia
,
M.
, and
Zerbst
,
U.
,
2016
, “
Application of the Cyclic R-Curve Method to Notch Fatigue Analysis
,”
J. Int. J. Fatigue
,
82
(Pt. 1), pp.
71
79
.
3.
Kontermann
,
C.
,
Almstedt
,
H.
,
Scholz
,
A.
, and
Oechsner
,
M.
,
2016
, “
Notch Support for LCF-Loading: A Fracture Mechanics Approach
,”
Struct. Integrity Procedia
,
2
, pp.
3125
3134
.
4.
Skelton
,
R. P.
,
1982
, “
Growth of Short Cracks During High Strain Fatigue and Thermal Cycling
,” ASTM International, West Conshohocken, PA, ASTM Special Technical Publication, Vol.
770
, pp.
337
381
.
5.
Vormwald
,
M.
,
2002
, “
Rissentstehung und Kurzrisswachstum unter Schwingbelastung
,” DVM-Bericht 234 Bruchvorgänge, pp.
19
35
.
6.
Elber
,
W.
,
1970
, “
Fatigue Crack Closure Under Cyclic Tension
,”
Eng. Fract. Mech.
,
2
(
1
), pp.
37
44
.
7.
Newman
,
J. C. J.
,
1984
, “
A Crack Opening Stress Equation for Fatigue Crack Growth
,”
Int. J. Fract.
,
24
(
4
), pp.
R131
R135
.
8.
Pommier
,
S.
, and
Bompard
,
P.
,
2000
, “
Bauschinger Effect of Alloys and Plasticity-Induced Crack Closure: A Finite Element Analysis
,”
Fatigue Fract. Eng. Mater. Struct.
,
23
(
2
), pp.
129
139
.
9.
de Matos
,
P. F. P.
, and
Nowell
,
D.
,
2008
, “
Numerical Simulation of Plasticity-Induced Fatigue Crack Closure With Emphasis on the Crack Growth Scheme: 2D and 3D Analyses
,”
Eng. Fract. Mech.
,
75
(
8
), pp.
2087
2114
.
10.
McClung
,
R. C.
,
Thacker
,
B. H.
, and
Roy
,
S.
,
1991
, “
Finite Element Visualization of Fatigue Crack Closure in Plane Stress and Plane Strain
,”
Int. J. Fract.
,
50
(
1
), pp.
49
27
.
11.
Park
,
S.-J.
,
Earmme
,
Y.-Y.
, and
Song
,
J.-H.
,
1997
, “
Determination of the Most Appropriate Mesh Size for a 2-D Finite Element Analysis of Fatigue Crack Closure Behaviour
,”
Fatigue Fract. Eng. Mater. Struct.
,
20
(
4
), pp.
533
545
.
12.
Andersson
,
H.
,
Persson
,
C.
,
Hansson
,
T.
,
Melin
,
S.
, and
Jarvstråt
,
N.
,
2004
, “
Constitutive Dependence in Finite-Element Modelling of Crack Closure During Fatigue
,”
Fatigue Fract. Eng. Mater. Struct.
,
27
(
2
), pp.
75
87
.
13.
Antunes
,
F.
, and
Rodrigues
,
D.
,
2008
, “
Numerical Simulation of Plasticity Induced Crack Closure: Identification and Discussion of Parameters
,”
Eng. Fract. Mech.
,
75
(
10
), pp.
3101
3120
.
14.
Cochran
,
K. B.
,
2009
, “
Numerical Modeling Issues in Finite Element Simulation of Plasticity Induced Crack Closure With an Emphasis on Material Model Effects
,” Ph.D. thesis, University of Illinois, Urbana-Champaign, IL.
15.
Cochran
,
K. B.
,
Dodds
,
R. H.
, and
Hjelmstad
,
K. D.
,
2011
, “
The Role of Strain Ratcheting and Mesh Refinement in Finite Element Analyses of Plasticity Induced Crack Closure
,”
Int. J. Fatigue
,
33
(
9
), pp.
1205
1220
.
16.
Kloos
,
K. H.
,
Granacher
,
J.
, and
Oehl
,
M.
,
1993
, “
Beschreibung des Zeitdehnverhaltens warmfester Stähle—Teil 1: Kriechgleichungen für Einzelwerkstoffe,” Materialwissenschaften
und Werkstofftechnik
,
24
(
8
), pp.
287
295
.
17.
Griffith
,
A. A.
,
1920
, “
The Phenomena of Rupture and Flow in Solids
,”
Philos. Trans., Ser. A
,
221
(
582–593
), pp.
163
198
.
18.
Irwin
,
G. R.
,
1957
, “
Analysis of Stresses and Strains Near the End of a Crack Traversing a Plate
,”
ASME J. Appl. Mech.
,
24
, pp.
361
364
.
19.
Rice
,
J. R.
,
1986
, “
A Path Independent Integral and the Approximate Analysis of Strain Concentration by Notches and Cracks
,”
ASME J. Appl. Mech.
,
35
(
2
), pp.
379
386
.
20.
Kontermann
,
C.
,
2017
, “
Entwicklung und Validierung eines FEM-Basierten Rissfortschrittsmodells zur Beschreibung von Stützwirkung unter Kriechermüdungsbeanspruchung
,” Ph.D. thesis, TU Darmstadt, Darmstadt, Germany.
21.
Saxena
,
A.
,
1986
, “
Creep Crack Growth Under Non-Steady-State Conditions
,” Fracture Mechanics, Vol. 905, ASTM International, West Conshohocken, PA.
22.
Nikbin
,
K. M.
,
Smith
,
D. J.
, and
Webster
,
G. A.
,
1986
, “
An Engineering Approach to the Prediction of Creep Crack Growth
,”
J. Eng. Mater. Technol.
,
108
(
2
), pp.
186
191
.
23.
Nikbin
,
K. M.
,
2009
, “
Predicting Creep and Creep/Fatigue Crack Initiation and Growth for Virtual Testing and Life Assessment of Components
,”
Virtual Testing and Predictive Modeling
, Springer, Boston, MA, pp.
105
136
.
24.
Mehmanparast
,
A.
,
Davies
,
C. M.
,
Webster
,
G. A.
, and
Nikbin
,
K. M.
,
2014
, “
Creep Crack Growth Rate Predictions in 316H Steel Using Stress Dependent Creep Ductility
,”
Mater. High Temp.
,
31
(1), pp.
84
94
.
25.
Kontermann
,
C.
,
Scholz
,
A.
, and
Oechsner
,
M.
,
2014
, “
A Method to Reduce Calculation Time for FE Simulations Using Constitutive Material Models
,”
Mater. High Temp.
,
31
(
4
), pp.
334
342
.
You do not currently have access to this content.