Details of Grant 

EPSRC Reference:	GR/T10558/01
Title:	Reliable Measurement of Residual Stress in Large Engineering Components
Principal Investigator:	Truman, Professor CE
Other Investigators:	Pavier, Professor MJ Smith, Professor D
Researcher Co-Investigators:
Project Partners:	British Energy Doosan Power Systems (Mitsui Babcock) IZAR QinetiQ Rolls-Royce Plc
Department:	Mechanical Engineering
Organisation:	University of Bristol
Scheme:	Standard Research (Pre-FEC)
Starts:	01 January 2005	Ends:	30 June 2008	Value (£):	186,501
EPSRC Research Topic Classifications:	Materials testing & eng.
EPSRC Industrial Sector Classifications:	Energy
Related Grants:	GR/T10541/01
Panel History:
Summary on Grant Application Form
The presence of tensile three dimensional (3D) or triaxial residual stresses can act to increase the likelihood of failure in engineering components. For example, in components operating at high temperature, these stresses increase the likelihood for creep failure. If the stresses are highly triaxial, only small amounts of creep strain are required before local failure. The likelihood for significant 3D residual stresses is greater in large, thick section components because there is greater material constraint preventing distortion.Knowledge of the triaxial residual stress state is therefore an essential ingredient in the integrity assessment of any component. To obtain this knowledge it is important to carry out measurements. In large specimens this must involve cutting combined with measurement of strain relaxation since the only alternative, neutron diffraction, cannot be used in steel specimens for depths larger than 30mm. Unfortunately, current cutting techniques make two assumptions that we know must be invalid for thicker components. The first assumption is that the residual stress state is essentially 2D, that is stresses through the thickness are negligible. The second assumption is that strain relaxation during cutting is purely elastic and that plastic redistribution does not occur. Recent experiments carried out at the University of Bristol have demonstrated these two assumptions are invalid for large components.The main theme of this proposal is to use a 3D eigenstrain formulation to develop analytical methods for obtaining these 3D residual stresses in large components. The new method will make the current assumptions unnecessary and will thus allow reliable measurements to be made for large, thick section components.
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Organisation Website:	http://www.bris.ac.uk