Commencing around May/June 2021, this 3.5 year studentship is available for UK, EU and International* students, who possess a first class or 2.1 (Honours), or equivalent EU/International qualification, in the relevant discipline of Solid Mechanics, Materials Science, Engineering, Physics or Mathematics. Candidate should have the following skills:
- Computer programming skills in at least one language (Matlab, Fortran, Python etc)
- Self-motivated individual with skills and/or interest in solid mechanics, physics, mathematics, materials and computer models.
- Knowledge in finite element modelling would be an advantage but is not essential
- A proactive approach, with initiative and ability to work independently
- Ability to: Synthesise, summarise and draw conclusions
- Strength to cope with schedules and deadlines
- Excellent organisational and communication skills
- Excellent written and spoken English.
Efficient manufacturing requires an improved understanding of relationships between processing routes, microstructure and final material properties, including residual stress. This has important benefits to reduce the cost and timescale of introducing an engineering component into the market through reductions in manufacturing trials, which are considerable in sectors such as aerospace and nuclear. Integrated computational materials engineering (ICME) is an emerging multi-disciplinary field that aims to model the material properties based on their microstructure by using physics-based approach for optimized manufacturing and performance.
Additive manufacturing (AM) introduces a range of variabilities which have an impact on the mechanical performance of components such as residual stresses, microstructural variation and porosity. This can lead to premature failure under cyclic loading or stress corrosion cracking. Performance is highly dependent on microstructure and residual stress (RS) which, if unknown, leads to undesirable “overdesign”. On the other hand, processing parameters (laser power, geometry and passing speed) during manufacturing have a profound effect on the resulting microstructure and the RS. Therefore, there is a need to establish relationships between processing conditions and mechanical properties to deliver guidance for engineers when estimating the service in AM components against premature component failure. ICME, coupled with experimental validation, offers flexibility and extrapolation of the manufacturing variables as opposed to costly testing campaigns.
There is an industrial challenge on reducing cost of high performance materials which has increased dramatically over the last two decades. Advanced modelling and numerical techniques are required to optimise fabrication and joining technologies, since in-service degradation and failure normally occurs at material interfaces such as welds or AM components, where non-optimal microstructures interact with localised stresses and structural discontinuities. This research will help AFRC industrial partners (Rolls Royce Plc, Timet, Aubert&Duval, Airbus) in aerospace and nuclear industries to manufacture parts to strict design specifications.
At AFRC we currently use digital twins that use thermo-mechanical finite element models, mechanical material subroutines and simplified microstructure evolution models. The overall aim of the project is to further develop these existing models and to compare the results against the vast existing data from our facilities. The temperature history during manufacturing, geometrical distortions and residual stress will be contrasted against the results from a thermo-mechanical manufacturing model. The temperature and strain histories will serve as an input for a simplified model to calculate the microstructure evolution. The final mechanical properties will be validated against calculations from an existing in-house physically-based model that describes the movement of dislocations. To achieve this, the student will integrate a number of multiscale modelling techniques to predict and validate the resulting microstructure and the RS at large and small scales as a function of the manufacturing processing conditions. This would allow validation of the finite element models implemented in ABAQUS software. The strategy will be to, where possible, work from existing partially developed models rather than developing models from the scratch.
• A microstructurally-sensitive physically-based viscoplastic model, that describes the movement of dislocations at the continuum level, for a range of temperatures and strain rates which are relevant to manufacturing.
• A themo-mechanical model that mimics the manufacturing process, incorporating appropriate heat generation and heat transfer via radiation, convection and conduction. This will predict the temperature fields, geometrical distortions and residual stress that arise from the manufacturing process, allowing model validation against the corresponding experimental data.
• A strain-temperature dependent model for microstructure evolution (grain size and precipitates) and corresponding mechanical properties, whose accuracy will be evaluated using data from our imaging and mechanical testing facilities.
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