The outer construction of nuclear transport packages relies heavily on two grades of austenitic stainless steel, 316 and 304. These steels provide excellent material properties at both ambient and elevated temperature primarily due to their post yield ductility and high failure strain. This proposal will investigate the fracture behaviour of these materials at ambient temperature under quasi-static conditions.
Current finite element models accurately reproduce elastic material response and reasonably accurately predict the materials response in the plastic regime up to the ultimate tensile strength (UTS). No claim to accurate prediction of failure is made beyond UTS. Standard tension tensile testing of the material to produce a standard elastic-plastic material model (typically used in industry) is insufficient to predict the stress-strain response beyond UTS.
This project will characterise the plasticity and fracture behaviour of these materials with regard to stress triaxiality and Lode parameter space beyond UTS using a standard tensile testing machine and novel specially shaped test specimens designed to provide different multiaxial loading conditions and hence different stress triaxialities i.e. Scherzug, Piers, tensile coupon, plane strain specimen, compression cylinder etc. Traditional methods of stain measurement cannot be employed because they provide average values rather than fracture process zone values necessary for accurate prediction of failure using finite element techniques. Test methodology and strain measurement techniques using digital image correlation (DIC) will be developed and correlated with finite element analysis to confirm the stress-state. From these analyses, fracture loci will be deduced and bounding failure limits proposed.
It is anticipated that a mesh independent failure model will be implemented in the ABAQUS finite element package and in LS DYNA using the GISSMO damage model. These models will provide a good approximation to failure for use in future validation studies and analytical assessment of nuclear packages where failure is of concern.
Essential Qualifications and Skills
Good honours degree in mechanical engineering or equivalent (2.1 or above). Good working knowledge of materials testing and FE based modelling, candidates with knowledge of ABAQUS and/or LS DYNA would be particularly welcome.
This is a fully funded student scholarship - “This Studentship is Subject to Contract”
Please quote the reference "G.Rothwell1" on the Research Proposal you will attach to your PhD application.