Qualifications & Experience
To commence 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. The candidate should have the following technical experience and personal 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
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Introduction & Background
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 a 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. The performance is highly dependent on the microstructure and the residual stress (RS) which, if unknown, leads to undesirable “overdesign”. On the other hand, the 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.
Additionally, there is an industrial challenge on reducing the 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 our AFRC industrial partners (Rolls Royce Plc., Timet, Aubert&Duval, Airbus) in aerospace and nuclear industries to manufacture parts to strict design specifications.
Research plan, current challenges & objectives
At the 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.
This PhD aims to research:
- 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.
This fully-funded NMIS PhD opportunity will cover Home and EU Fees and Stipend.
We will only accept applications from international students who confirm in their email application that they are able to pay the difference between the Home and International fees (approximately £16,500 per annum). The Stipend is not to be used to cover fees. If you are unable to cover this cost the application will be rejected.
The student will be jointly supervised by Dr David Gonzalez and Dr Salah Rahimi from the AFRC. This academic team has the required skills in modelling and experimental methods.
Please note: We request that potential candidates direct all questions to email@example.com.
Dr. David Gonzalez
Dr. David Gonzalez research activity is focused on the simulation of the mechanical behaviour of materials at different length scales and the development of hierarchical multiscale approaches. He has applied these methods to a number of industrial problems. He has expertise in building and validating these models to provide engineers with tools for improving material manufacture and material performance under service conditions such as fatigue, creep and residual stress at various length scales. Before joining the AFRC at the University of Strathclyde in February 2020, he has worked in a number of industrially and EPSRC funded projects at Manchester University, Oxford University and Birmingham University. Funding was supported by industrial collaborators including Mitsubishi Heavy Industries, Rolls Royce and Sandvik. He also has experience teaching engineering and MSc courses, supervising 20 final-year undergraduate projects as well as supporting PhD students. Additionally, he has been involved in several experiments (as a PI and as a co-PI) using synchrotron X-ray facilities at the European Synchrotron Radiation Facility to investigate the short fatigue crack evolution. He has experience combining these results to build image-based models to predict deformation in metallic materials and micro-cracking in ceramic materials. He also has experience in validating multiscale polycrystalline models against experimental data using neutron diffraction (ND) at the Rutherford Appleton laboratory (Oxfordshire).
Dr Rahimi leads the AFRC materials and residual stress team. This research team has a well-established background in developing a number of experimental protocols that are ideally suited to inform and validate such models. The techniques used include microstructural and mechanical characterization (e.g. EBSD, SEM, high strain rate flow stress) to relate manufacturing processing to microstructure evolution and its effect on materials performance. Additionally, Dr Rahimi leads the state-of-the-art hole-drilling and contour methods equipment at the AFRC for residual stress measurements. These techniques have been successfully applied in a number of industrial research and development programmes for our AFRC industrial partners.
The AFRC is part of the University of Strathclyde and of the NMIS (National Manufacturing Institute Scotland).
More information about the AFRC
How to apply
Individuals interested in this project should email: firstname.lastname@example.org, along with the title of the project you are applying for and attach your most up-to-date cv aligned with the requirements of this studentship. Due to funding restrictions this position is only available for UK or European Union candidates.