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Special sessions

Special Sessions

Internal Fatigue Crack Initiation and Growth in Metals

 

Organizers:

 

Eberhard Kerscher, University of Kaiserslautern, Germany

Sefanie Stanzl-Tschegg, University of Natural Resources and Applied Life Sciences (BOKU) Vienna, Austria

Topic of the Special Session:

 

Fatigue of Metals continues to be a very challenging topic of research. There are still a lot of questions to be answered to understand fatigue mechanisms. Recent years have seen a growing interest in fatigue failures starting from the inside of a part or specimen although classical fatigue cracks are normally expected to start at the material surface. There seem to be two governing reasons for internal crack initiation and grow:

 

  • The increased surface quality of parts reduces the probability of surface failure.

 

  • At low load amplitudes and correspondingly long fatigue life times there are failures below the classical fatigue limit, which are investigated in very high cycle fatigue (VHCF)-research projects. These failures are often accompanied by modifications of the fatigue fracture surface at the crack initiation site, called fine granular area (FGA), optical dark area (ODA), or granular bright facet (GBF).

 

The goal of the proposed session is to discuss current results on the interior fatigue crack initiation and growth in metals with leading researchers in this field.

 

Fatigue in Nuclear Plant Materials - Session co-organised by INCEFA+ Project

 

Organizers:

 

Sergio Cicero, University of Cantabria, Spain

Kevin Mottershead, AMEC Foster Wheeler, UK

Matthias Bruchhausen, European Commission - JRC, The Netherlands

Thomas Mettais, EDF, France

Roberto Lacalle & Román Cicero, Inesco Ingenieros, Spain

Topic of the Special Session:

 

There has been a significant research effort in recent years addressing the influence of high temperature light water reactor (LWR) coolant environments on fatigue of pressure vessel and circuit materials. The response of these materials to cyclic loading resulting from plant transients is assessed on the basis of materials properties and design codes similar to the ASME III and XI design codes for fatigue endurance (commonly referred to as fatigue initiation) and fatigue crack growth respectively. These materials research activities have addressed both the effects on fatigue life, using conventional fatigue endurance testing methods, and fatigue crack growth using fracture mechanics specimens. As an example, for both ferritic and austenitic steels, significant effects of high temperature water on fatigue endurance have been observed under specific conditions.

 

The application of fatigue assessment procedures for nuclear components (e.g., USNRC Regulatory Guide 1.207) can result in predictions of very high cumulative fatigue usage factors for some plant components and transients which appear inconsistent with the relatively good performance of stainless steel components in operating reactors over several decades, revealing the existence of significant knowledge gaps.

 

The aims of this session are, among others:

 

1. To share views on international approaches for assessing Environmental Assisted Fatigue

 

2. To share understanding of gaps in assessment capabilities

 

3. To share ideas for improved understanding to the benefit of assessment capability

 

 

 

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