Austenitic stainless steel of type X6CrNiNb18-10 exhibits advantageous mechanical and chemical properties and is a common material for numerous applications in the nuclear power plant and chemical industries. Besides the mechanical strain induced by high pressure, the fatigue life in welded pipelines is affected by additional thermomechanical strains due to thermal loading. The welding process mainly determines the geometry and metallurgical constitution of the welded joint. Therefore, the butt welds additionally influence the strain gradient along the component and reduce its lifetime. While the base and weld material are similar, they show different softening and hardening behavior, especially at ambient temperature. Cyclic hardening occurs in the base material, whereas cyclic softening can be observed in the weld material. The hardness distribution along the welded joint reveals no clear differentiation of the base material, the heat affected zone, and the weld material. The attributes of the individual materials cannot be transferred to the welded joint automatically. Thus, the analysis of the interaction between the materials along the welded joint is a main topic of this research. To this end, digital image correlation (DIC) is used for different kinds of specimens and load conditions. The position along the testing area at which fatigue failure occurs depends on the specimen type and the load condition but not on the temperature. Further, isothermal and anisothermal fatigue tests on welded cruciform specimens are presented. The common practice of the effective strain is discussed for the analyzed conditions.

References

References
1.
Kerntechnischer Ausschuss, 2013, “
Components of the Reactor Coolant Pressure Boundary of Light Water Reactors, Part 2: Design and Analysis
,” Kerntechnischer Ausschuss, Salzgitter, Germany, Standard No. KTA 3201.2 2013-11.
2.
Deutsches Institut für Normung, 2013, “
Unfired Pressure Vessels—Part 3: Construction
,” Beuth Verlag, Berlin, Standard No. DIN EN 13445-3:2013-12.
3.
ASME Boiler and Pressure Vessel Code
,
2007
, “
Section III Division 1—Subsection NB: Class 1 Components; Rules for the Construction of Nuclear Power Plant Components
,” ASME, New York.
4.
Bosch
,
A.
,
Lang
,
E.
,
Beier
,
H. T.
,
Vormwald
,
M.
,
Langschwager
,
K.
,
Scholz
,
A.
, and
Oechsner
,
M.
,
2014
, “
Ermüdungsnachweis für Unbearbeitete und Nachbearbeitete Schweißverbindungen Einschließend Thermozyklische, Elastisch-Plastische Beanspruchungen
,” Final Report, IGF-Vorhaben-Nr. 17457 N.
5.
Langschwager
,
K.
,
Bosch
,
A.
,
Lang
,
E.
,
Rudolph
,
J.
,
Vormwald
,
M.
,
Scholz
,
A.
, and
Oechsner
,
M.
,
2014
, “
Fatigue Behavior of Butt Weld Seams: Experimental Investigation and Numerical Simulation
,”
ASME
Paper No. PVP2014-28787.
6.
Schuler
,
X.
,
Herter
,
K.-H.
, and
Rudolph
,
J.
,
2013
, “
Derivation of Design Fatigue Curves for Austenitic Stainless Steel Grades 1.4541 and 1.4550 Within the German Nuclear Safety Standard KTA 3201.2
,”
ASME
Paper No. PVP2013-97138.
7.
Smaga
,
M.
,
Hahnenberg
,
F.
,
Sorich
,
A.
, and
Eifler
,
D.
,
2011
, “
Cyclic Deformation Behavior of Austenitic Steels in the Temperature Range −60 °C<=T <=550 °C
,”
Eng. Mater.
,
465
, pp.
439
442
.
8.
Sorich
,
A.
,
Smaga
,
M.
, and
Eifler
,
D.
,
2013
, “
Influence of Loading Conditions on the Cyclic Deformation Behavior and Phase Transformation of the Austenitic Stainless Steel AISI 347 at Ambient Temperature and 300 °C
,”
7th International Conference on Low Cycle Fatigue
, Aachen, Germany, Sept. 9–11, pp. 33–38.
9.
Molak
,
R. M.
,
Paradowski
,
K.
,
Brynk
,
T.
,
Ciupinski
,
L.
,
Pakiela
,
Z.
, and
Kurzydlowski
,
K. J.
,
2009
, “
Measurement of Mechanical Properties in a 316L Stainless Steel Welded Joint
,”
Int. J. Pressure Vessels Piping
,
86
(
1
), pp.
43
47
.
10.
Remes
,
H.
,
2013
, “
Strain-Based Approach to Fatigue Crack Initiation and Propagation in Welded Steel Joints With Arbitrary Notch Shape
,”
Int. J. Fatigue
,
52
, pp.
114
123
.
11.
Madi
,
Y.
,
Matheron
,
P.
,
Recho
,
N.
, and
Mongabure
,
P.
,
2004
, “
Low Cycle Fatigue of Welded Joints: New Experimental Approach
,”
Nucl. Eng. Des.
,
228
(1–3), pp.
161
177
.
12.
Reynolds
,
A. P.
, and
Duvall
,
F.
,
1999
, “
Digital Image Correlation for Determination of Weld and Base Metal Constitutive Behavior
,”
Weld. Res. Suppl.
,
355
(Suppl) pp. 355–360.
13.
GOM mbH
,
2009
, “
ARAMIS Manual—Software
,” GOM GmbH, Braunschweig, Germany.
14.
Bauerbach
,
K.
,
Vormwald
,
M.
, and
Rudolph
,
J.
,
2009
, “
Fatigue Assessment of Nuclear Power Plant Components Subjected to Thermal Cyclic Loading
,”
ASME
Paper No. PVP2009-77450.
15.
Hobbacher
,
A.
,
2007
,
Recommendations for Fatigue Design of Welded Joints and Components
, Springer International Publishing, Cham, Switzerland.
16.
Radaj
,
D.
,
1996
, “
Review of Fatigue Strength Assessment of Nonwelded and Welded Structures Based on Local Parameters
,”
Int. J. Fatigue
,
18
(
3
), pp.
153
170
.
17.
Rudolph
,
J.
,
Götz
,
A.
, and
Hilpert
,
R.
,
2012
, “
Regelwerkskonforme Bestimmung von Erschöpfungsgraden bei Allgemeinen Elasto-Plastischen Finite-Elemente-Analysen—Teil 1
,” Technische Sicherheit, pp.
39
44
, 7–8.
18.
Bosch
,
A.
,
Rudolph
,
J.
, and
Vormwald
,
M.
,
2015
, “
Numerical Investigations of Seam Welds Under Low Cycle Fatigue—Proposal for Lifetime Estimation and Recommendations for Design With Commonly Used Guidelines
,”
ASME
Paper No. PVP2015-45576.
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