The project:
Engineering Critical Assessment calculations for welded joints must include provision for the effect of residual stresses on welding defects. Distributions of welding residual stress are generally not known, so very conservative profiles are needed. Computer predictions are possible, but their accuracy relies on an accurate knowledge of the mechanical material behaviour at high temperature during very fast thermal cycles.
The objective of this project is to develop a constitutive model for ferritic reactor pressure vessel steels that is suitable for use in finite element welding simulations for the prediction of residual stress. The model will integrate phase transformation, material hardening and annealing phenomena to predict yield and hardening behaviour for realistic thermal and deformation cycles. The model will be calibrated using the new Gleeble machine at the University of Manchester in conjunction with various techniques for microstructural analysis and hardness measurement. It will be validated using neutron diffraction measurements already obtained for a variety of weld geometries.
The collaboration will be achieved via the close links between the Materials Performance Centre at The University of Manchester and TWI, including:
- Approximately 75% of the REs time spent at TWI, Cambridge.
- Regular planned time spent in the Materials Performance Centre to undertake specific experimental studies (including Gleeble testing) of welds and links to ongoing weld residual stress modelling studies at Manchester.
- Quarterly progress meetings with the academic supervisors at TWI and Manchester, alongside regular informal contact.
The RE will attend TWI's conventional Graduate induction course. Training of the RE will cover induction, health and safety and risk assessment. The RE is free to attend other TWI provided training courses, including report writing, presentation and project management. The RE will be encouraged to read widely about the subject of the research and to attend relevant technical seminars and conferences in the field.
Training will be provided into wider aspects of structural integrity assessment through one-to-one discussions with colleagues on the job and attendance on relevant internal and external courses. Instruction will be provided on the use of any specialist equipment and experimental procedures that may be required for the research. The RE will be expected to produce papers and presentations on the research in due course.
The RE will attend meetings at TWI to consider the commercial and management issues associated with the project. The RE will work alongside experts in modelling and fracture within TWI to develop proposals for research programmes within TWI's core research programme, to manage research contracts, and to assist in the production and delivery of reports, milestones/deliverables. The RE will be integrated and treated as a full member of Structural Integrity Group.
Four Year Engineering Doctorate Student with The University of Manchester A constitutive model for the prediction of microstructure and welding residual stresses in ferritic steels
