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EPSRC Reference: GR/S34045/01
Title: Multi-scale modelling and simulations of cleavage fracture in steels
Principal Investigator: Chapman, Professor SJ
Other Investigators:
Roberts, Professor S Wilkinson, Professor AJ Ockendon, Dr J
Researcher Co-Investigators:
Project Partners:
Ricardo Group Serco
Department: Mathematical Institute
Organisation: University of Oxford
Scheme: Standard Research (Pre-FEC)
Starts: 31 March 2004 Ends: 29 June 2007 Value (£): 227,664
EPSRC Research Topic Classifications:
Continuum Mechanics Eng. Dynamics & Tribology
EPSRC Industrial Sector Classifications:
Technical Consultancy Construction
Related Grants:
Panel History:  
Summary on Grant Application Form
The key ingredient in understanding the important engineering problem of ductile/brittle transitions in ferritic steels is the initiation of matrix fracture from microcracks (cracked carbide particles) in the plastic zone around the tip of a macrocrack. It is the prediction of the stress field around such a particle that is the centrepiece of this proposal. The underlying mechanisms that need to be considered are the dynamics of (i) the dislocations emitted from the crack in the carbide, and (ii) the dislocations in the plastic matrix, especially those around the periphery of the particle. Current discrete dislocation simulations are only able to deal with this as a two-dimensional problem in plane or antiplane strain for a carbide particle embedded in a pristine matrix. Hence we propose to develop mathematically similar continuum models, using the discrete dislocation simulations as a quality control initially. The continuum models will then be extended to progressively more realistic three-dimensional dislocations in the matrix. It is our intention that the resulting understanding will be robust enough to be ultimately incorporated into a local fracture condition in situations in which many carbide particles are randomly distributed around the macrocrack tip. The models will be developed hand-in-hand with physical experiments on ferritic steels with wellcharacterised microstructures. Specimens will be loaded to fracture or near fractureover a range of temperatures, sectioned, and examined gy SEM to identify fracture nuclei.
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Organisation Website: http://www.ox.ac.uk