Details of Grant 

EPSRC Reference:	GR/J59920/01
Title:	MICROMECHANISTIC INTERACTIONS IN THERMOMECHANICAL FATIGUE
Principal Investigator:	Withers, Professor P
Other Investigators:	Newcomb, Dr S Newcomb, Professor S Stobbs, Dr W
Researcher Co-Investigators:
Project Partners:	Rolls-Royce Plc
Department:	Materials Science & Metallurgy
Organisation:	University of Cambridge
Scheme:	Standard Research (Pre-FEC)
Starts:	01 October 1993	Ends:	31 May 1997	Value (£):	211,133
EPSRC Research Topic Classifications:	Eng. Dynamics & Tribology
EPSRC Industrial Sector Classifications:	Aerospace, Defence and Marine
Related Grants:
Panel History:
Summary on Grant Application Form
Many components in high temperature plant and in aeroengines experience fatigue loading, in which the loading arises in part directly from mechanical action, and in part as a result of temperature gradients or thermal expansion mismatch. Conventional design philosophies assume that conservative life predictions can be made using isothermal data at the maximum thermomechanical fatigue (TMF) loading temperature, but recent TMF results have shown that this assumption is often unsafe. Recently developed engineering approaches to component lifting under TMF assume that the different damage mechanisms which are seen in isothermal tests as a function of strain and temperature can be summed around the TMF cycle, as independent damage fractions. The object of this proposal is to examine this basic assumption. The study will concentrate on the potential micromechanistic interactions which can occur in fatigue loading where both the strain and temperature are changing; interactions between deformation and fracture mechanisms characteristic of different temperatures, interactions between the evolving microstructure and the deformation behaviour, interactions between oxidation and plasticity, and between coatings and the substrate, for loading during strain/temperature cycles which cross a variety of mechanistic transitions. The results will show which types of interaction can have a dominant effect on TMF life in single crystal Ni-base turbine blade alloys, and will provide a scientific basis on which to develop material behavioural modelling for TMF and hence appropriate life prediction strategies.
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Organisation Website:	http://www.cam.ac.uk