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Research and development into a European Code of Practice for strain controlled thermomechnical fatigue testing

pubblicazioni - Articolo

Research and development into a European Code of Practice for strain controlled thermomechnical fatigue testing

strain controlled thermomechnical fatigue testing Claudia Rinaldi a , Valerio Bicego b , Peter Hähner c , Ernst Affeldt d , Thomas Brendel d , Henrik Andersson e , Tilmann Beck f , Hellmuth Klingelhöffer g , Hans-Joachim Kühn g , Alain Köster h , Malcolm Loveday i , Massimo Marchionni l , Catherine Rae m Rivista: International Journal of Fatigue – Volume 30 N. 2 2008 ISSN 0142-1123 UK, 24 Marzo, 2007 A CESI RICERCA B CESI SPA C JRC INSITUTE FOR ENERGY D MTU AEREO ENGINES E KIMAB F UNIVERSITY OF KARLSRUHE G BAM H ECOLE NATIONALE SUPERIEURE DES MINES DE PARIS I NATIONAL PHYSICAL LABORATORY L CNR-IENI M UNIVERSITY OF CAMBRIDGE Thermo-mechanical fatigue (TMF) testing plays an increasingly important role in the design, the reliability assessment and the life cycle management of safety critical components used, for instance, for power generation, in the process industry and in aeronautical and automotive applications, with a view to increasing the fuel efficiency, safety and service intervals, while reducing production(and materials) costs. In European Commission funded research project (acronym: TMF – Standard) of the 5 th Framework Programme, 20 European laboratories have undertaken a joint research effort to establish a validated code-of-practice (CoP) for strain-controlled TMF testing. Starting from a survey of the testing protocols and procedures previously used by the partners, a comprehensive pre-normative research activity into various issues has been completed, addressing the dynamic temperature control, the effect of deviations in nominal temperatures and phase angles, the influences of temperature gradients, as well as the practicalities of test interruption and restart procedures. Meaningful allowable tolerances for the various test parameters were identified and practical recommendations as to the test techniques were formulated. From this a preliminary CoP was compiled and used to guide an extensive round robin exercise among amplitude TMF of nominally homogencous metallic materials subjected to spatially uniform temperature fields and uniaxial mechanical loading. It is intended in the field strain-controlled TMF. This paper highlights some of the results of the TMF-Standard project. Moreover, commonalities and differences of the present CoP with respect to the standard documents for strain-controlled TMF, which have been developed at ISO and ASTM levels, are presented in this paper.

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