Deformation Behaviour of P91 Martensitic Steel: testing and crystal plasticity modelling

Speaker:   Prof. Noel O’Dowd

Affiliation: School of Engineering

            Bernal  Institute

            University of Limerick, Ireland

            noel.odowd@ul.ie

Abstract： 

In this presentation, Noel will discuss how the finite element method is used to predict the deformation of metallic materials using physical models to represent the material behaviour. At the micro-scale (10-6 m scale) the theory of crystal plasticity is used to describe the slip behaviour of atomic planes due to dislocation motion. The computational modelling is linked to experimental analysis, as the application of such models in engineering design relies on experimental validation over the range of length scales modelled. In this work experiments have been carried out using a number of techniques including electron back scattered diffraction (EBSD) in a scanning electron microscope (SEM) which can be used to track the orientation changes in the material at the microscale. A new type of shear specimen is used which allows large deformations (up to 40% plastic strain) to be observed in the material and assessed using EBSD methods. Micro-pillar testing using a nano-indenter is also used to examine deformation of a single crystal (grain) of the material so that effects of grain boundaries are excluded. The methods will be illustrated for an engineering steel (P91) which has a complex martensitic microstructure with sub-grain structures at the sub-micron (0.4 µm) level. The ability of the methods to predict deformation

About speaker:

Noel O'Dowd is Chair of Mechanical Engineering at the University of Limerick. Noel received his degree in Mechanical Engineering from the University of Galway and went onto complete an MSc and PhD in Solid Mechanics from Brown University, USA. After completing his PhD, Noel took up a research fellowship with the Graduate Aeronautical Laboratories at the California Institute of Technology. Professor O'Dowd then joined the academic staff at Imperial College London for thirteen years before joining the University of Limerick in 2006. Noel was Vice-Chair of the American Society of Pressure Vessels committee on Materials and Fabrication  and is a Visiting Professor at Imperial College London. Professor O'Dowd's research is in the area of computational mechanics and fracture mechanics of engineering materials. He has published over a hundred and thirty research articles in these and related areas. His research in fracture mechanics and residual stress have been incorporated into industry procedures for assessing the safety of metallic structures.