The paper is concerned with the modeling of the behaviour of welds when subjected to severe thermal and mechanical loads where the maximum temperature during dwell periods lies in the creep range. The methodology of the life assessment method R5 is applied where the detailed calculations are carried out using the linear matching method (LMM), with the objective of generating an analytic model. The linear matching method has been developed to allow accurate predictions using the methodology of R5, the UK life assessment method. The method is here applied to a set of weld endurance tests, where reverse bending is interrupted by creep dwell periods. The weld and parent material are both Type 316L(N) material, and data were available for fatigue tests and tests with 1 and $5h$ dwell periods to failure. The elastic, plastic, and creep behavior of the weld geometry is predicted with the LMM using the best available understanding of the properties of the weld and parent material. The numerical results are translated into a semi-analytic model. Using the R5 standard creep/fatigue model, the predicted life of the experimental welds specimens are compared with experimental data. The analysis shows that the most severe conditions occur at the weld/parent material interface, with fatigue damage concentrated predominantly in the parent material, whereas the creep damage occurs predominantly in the weld material. Hence, creep and fatigue damage proceed relatively independently. The predictions of the model are good, except that the reduction in fatigue life due to the presence of the weld is underestimated. This is attributed to the lack of separate fatigue date for the weld and parent material and the lack of information concerning the heat affected zone. With an adjustment of a single factor in the model, the predictions are very good. The analysis in this paper demonstrates that the primary properties of weld structures may be understood through a number of structural parameters, defined by cyclic analysis using the linear matching method and through the choice of appropriate material data. The physical assumptions adopted conform to those of the R5 life assessment procedure. The resulting semi-analytic model provides a more secure method for extrapolation of experimental data than previously available.

1.
Bretherton
,
I.
,
Knowles
,
G.
,
Hayes
,
J. P.
,
Bate
,
S. K.
, and
Austin
,
C. J.
, 2004, “
PC/AGR/5087: Final Report on the Fatigue and Creep-Fatigue Behaviour of Welded Cruciform Joints
,” Report RJCB/RD01186/R01, British Energy, Barnwood, Gloucester, UK, January.
2.
Bretherton
,
I.
, and
Budden
,
P. J.
1999, “
Assessment of Creep-Fatigue Endurance of Large Cruciform Weldments
,”
Trans. SMiRT 15
, Seoul, Aug. 15–20, IV, pp.
185
192
.
3.
Ponter
,
A. R. S.
, and
Engelhardt
,
M.
, 2000, “
Shakedown Limits for a General Yield Condition: Implementation and Examples for a Von Mises Yield Condition
,”
Eur. J. Mech. A/Solids
0997-7538,
19
, pp.
423
446
.
4.
Chen
,
H. F.
, and
Ponter
,
A. R. S.
, 2001, “
A Method for the Evaluation of a Ratchet Limit and the Amplitude of Plastic Strain for Bodies Subjected to Cyclic Loading
,”
Eur. J. Mech. A/Solids
0997-7538,
20
, pp.
555
572
.
5.
Chen
,
H. F.
, and
Ponter
,
A. R. S.
, 2002, “
The 3-D Shakedown and Limit Analysis Using the Linear Matching Method
,”
Int. J. Pressure Vessels Piping
0308-0161,
78
, pp.
443
451
.
6.
Chen
,
H. F.
, and
Ponter
,
A. R. S.
, 2003, “
Application of the Linear Matching Method to the Integrity Assessment for the High Temperature Response of Structures
,”
PVP (Am. Soc. Mech. Eng.)
0277-027X,
458
, pp.
3
12
.
7.
Chen
,
H.
, and
Ponter
,
A. R. S.
, 2004, “
Integrity Assessment for a Tubeplate Using the Linear Matching Method
,”
Int. J. Pressure Vessels Piping
0308-0161,
81
, pp.
327
336
.
8.
Chen
,
H.
, and
Ponter
,
A. R. S.
, 2004, “
A Simplified Creep-Reverse Plasticity Solution Method for Bodies Subjected to Cyclic Loading
,”
Eur. J. Mech. A/Solids
0997-7538,
81
, pp.
651
577
.
9.
British Energy Generation Ltd
, 2003, “
R5: Assessment Procedure for the High Temperature Response of Structures, Issue 3
,” R. A. Ainsworth, ed., Barnwood, Gloucestershire, UK.
10.
Ponter
,
A. R. S.
, and
Chen
,
H.
, 2006, “
The Development of a Failure Model for Welds under Variable Load at High Temperature
,” Department of Engineering, University of Leicester, Internal Report, January.