No abstract

Large uncertainties exist in fatigue life evaluation using existing elastic stress analysis. The usage factor is obtained by comparison of strain amplitude evaluation on different points of the components and the fatigue S-N curve of the material. This paper will review existing codified rules in major nuclear Codes that are proposed as simplified elastic-plastic analysis of strain amplitude. The different formulas proposed by the different Codes are described with their own background document and compared on typical cases. Methods are based on simplified elastic-plastic approach (elastic analysis plus correction factor) with associated material data. The Code comparison includes nuclear Codes, as ASME Boiler and Pressure Vessel Code Section III, French RCC-M and RCC-MRx and German KTA; Russian PNAEG Code and JSME rules are also considered based on specific English version of the Codes for fatigue rules. Two types of components are concerned by the comparison: vessels and piping systems. All these Codes are proposing different Ke and Kv rules based on different assumption. Finally, a first set of recommendation to perform reference inelastic analysis will be presented to improve existing codes on an harmonized way, associated to analytical recommendations, all material properties needed and criteria to apply this modern methods. This review is mainly done in World Nuclear Association (WNA), Cooperation in Reactor Design Evaluation and Licensing (CORDEL) Working Group, Codes & Standards Task Force.

For many design and ageing considerations fracture mechanics is needed to evaluate cracked components. The major parameters used are K and J. For that, the different codes (RSE-M appendix 5, RCC-MRx appendix A16, R6 rule, ASME B&PV Code Section XI, API, VERLIFE, Russian Code…) propose compendia of stress intensity factors, and for some of them compendia of limit loads for usual situations, in terms of component geometry, type of defect and loading conditions. The benchmark bench-KJ, proposed in the frame of the OECD/IAGE Group, aims to compare these different estimation schemes by comparison to reference analyses done by Finite Element Method, for representative cases (pipes and elbows, mechanical or/and thermal loadings, different type and size of cracks). The objective is to have a global comparison of the procedures but also of all independent elements as stress intensity factor or reference stress. The benchmark will cover simple cases with basic mechanical loads like pressure and bending up to complex load combinations and complex geometries (cylinders and elbows) including cladding or welds: these cases are classified into 6 tasks. Twenty-eigth partners are involved in this benchmark. This paper gives a global overview of the different tasks of the benchmark and presents the analysis of the results for the first task, devoted on the elastic stress intensity factor calculation (task 1).

The objective of the ADIMEW project, that follows BIMET program finished in 2000, is to contribute to the development and verification of analysis methods which describe the behaviour of an external circumferential defect at the surface of a Dissimilar Metal Weld (DMW). The complexity of the problem results from the prevailing mixed-mode loading conditions, the variation in material constitutive equations across the weld zone, and the presence of large residual stress field. Under these circumstances, classic fracture mechanics concepts are difficult to apply. Recently different cracks has been discovered in different US and European plants (VC SUMMER, RINGHALS, BIBLIS). The problem of integrity of aged (cracked) DMW’s remains an important safety issue. This paper presents the new on-going program ADIMEW, with similar organisation than BIMET and complementary objectives. Within the framework of this project, one large test has been successfully done on July 2003. The paper presents a general overview of the program and the major recommendations and conclusions.

This paper presents the state of the art and the progress made in the numerical simulation of the stress state in a complex multi-material structure, using not only sophisticated finite element tools, but also the simplified engineering methods. A comparison of the numerical results concerning residual stresses is made with those measured using X-ray diffraction method and incremental hole-drilling technique. Finally, an example is given on the analysis of a fully circumferential crack in a typical bimetallic weld under pressure, thermal, and residual stresses. [S0094-9930(00)00703-4]