Seminar 6th July 2011 4 p.m. University of Southampton, Room 3031, Building 7 (Lanchester)
A Crystal Plasticity Study of Constitutive Behaviour, Crack-Tip Deformation and Oxygen Diffusion for a Polycrystalline Nickel-Based Superalloy
Dr Liguo Zhao, Department of Mechanical and Design Engineering
University of Portsmouth
- Web page
- http://www.southampton.ac.uk/ses/research/groups/engmats.page?
- Categories
- Finite elements
- Submitter
- Petrina Butler
Dr Liguo Zhao
Crystal plasticity has been applied to model the cyclic constitutive behaviour of a polycrystalline nickel-based superalloy at elevated temperature from finite element analyses of Representative Volume Element (RVE). Model simulations are in good agreement with the experimental results for stress-strain loops, cyclic hardening behaviour and stress relaxation behaviour during the hold periods at the maximum and minimum strain levels.
The model was further applied to study the near-tip deformation of a transgranular crack in a CT specimen using a submodelling technique. The interaction between oxygen diffusion and heterogeneous plasticity deformation at grain level was investigated, aiming to quantify the oxidation embrittlement of the material under fatigue loading conditions at high temperature.
Prediction of oxidation-assisted crack growth has also been carried out based on finite element analyses of oxygen diffusion, coupled with viscoplastic deformation, near a fatigue crack tip. A failure envelop has been constructed for crack growth prediction based on the consideration of both oxygen concentration and accumulated inelastic strain near the crack tip. The predictions from the failure envelop compared well with the experimental results for triangular and dwell loading waveforms, with marked improvements achieved over those predicted from the viscoplastic deformation alone.
Speaker Biography
Dr Liguo Zhao is a Senior Lecturer in the Department of Mechanical and Design Engineering of the University of Portsmouth, and currently holds the prestigious Royal Society Leverhulme Trust Senior Research Fellowship. He has a BEng and a PhD in Solid Mechanics, awarded by Xi'an Jiaotong University of China. Research interests include fracture, fatigue and creep of advanced aerospace materials, environment-assisted crack initiation and propagation, constitutive modelling of engineering materials, residual stress and its effect on failure in polymer composites, thermal shock fracture of solids, and multiple crack interaction.
Dr Zhao has more than eight-years postdoctoral research experience, and worked at Cambridge University, Imperial College, Nottingham University and Portsmouth University. He has published over 30 refereed journal papers with very good international recognition. Dr Zhao is supervising two postdoctoral researchers and a PhD student who are working on fatigue, creep and fatigue-oxidation behaviour of nickel alloys. His research is supported by the EPSRC, the Royal Society, the Leverhulme Trust and the Royal Academy of Engineering of the UK.
This seminar is part of the joint research group initiative and researchers from ALL groups (Bio, Materials and nCATS) should attend. Others also are welcome.
Tea, coffee and biscuits will be served from 15:45.
Contact
Dr Nong Gao
Materials Research Group
School of Engineering Sciences
University of Southampton
Southampton SO17 1BJ, United Kingdom
Tel. (00-44) (0)23-80595094
FAX (00-44) (0)23-80593016
E-mail: N.Gao@soton.ac.uk