Creep Cavity Initiation

This FESI-sponsored workshop, to be held on Tuesday, October 11, 2022 at St Anne’s College, University of Oxford, Woodstock Road, Oxford OX2 6HS, forms part of the dissemination of research carried out by The Open University, Oxford University, the University of Bristol and Beihang University (China) with funding from EPSRC (Grant EP/R026076/1), EDF Energy Ltd (High Temperature Centre) and EPRI (USA).

The life of modern (and legacy) power generating plant is limited by the high temperature performance of the construction materials. But a continuing lack of understanding of the underlying processes controlling nucleation of creep cavities (i.e. damage) means that empirical models fitted to macroscopic data are currently employed to assess creep failure and define safe operating life. Development of creep cavitation is contingent on initiation events, early growth and the potential for the cavities to close. The latter mechanism is important when micro- and/or macro-stresses are relaxed. Fundamental insights, knowledge and models arising from recent research programmes have the potential to allow more physically based design and assessment procedures to be developed for components that operate in a creep regime. This will help to underwrite life extensions of legacy power generating plant that are limited by the high temperature performance of the construction materials, as well as supporting future designs of power generating plant that must exceed a 60-year life specification.

Speakers invited to the workshop from EPRI, EDF and the UKAEA, Culham Centre for Fusion Energy, will reflect on the importance of understanding the creep behaviour of commercial materials including martensitic steels, stainless steels, nickel-based alloys and copper for future large scale power generation plant. There will be a review of classical creep cavity nucleation theory for metals and alloys that has been developed over the past 50 years, highlighting how grain boundary micro-mechanism models can now be incorporated in crystal plasticity finite element (CPFE) analyses. The development of novel macro- and micro- length scale test specimen designs to evaluate the influence of stress magnitude and microstructure on creep cavitation damage will be presented. In addition, the workshop will illustrate how the state of cavitation has been quantified using small angle neutron scattering (SANS), high resolution FIB serial sectioning and image analysis using artificial intelligence (AI). These quantified observations of nucleated cavities in metals and alloys have been assessed to infer the mechanisms contributing to cavity nucleation/early growth and inform more realistic predictive models.

To view the workshop programme, including confirmed speakers. please follow this link.